CN116300317A - Photoresist coating method - Google Patents
Photoresist coating method Download PDFInfo
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- CN116300317A CN116300317A CN202310316023.2A CN202310316023A CN116300317A CN 116300317 A CN116300317 A CN 116300317A CN 202310316023 A CN202310316023 A CN 202310316023A CN 116300317 A CN116300317 A CN 116300317A
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- 229920002120 photoresistant polymer Polymers 0.000 title claims abstract description 217
- 238000000576 coating method Methods 0.000 title claims abstract description 59
- 239000000853 adhesive Substances 0.000 claims abstract description 72
- 230000001070 adhesive effect Effects 0.000 claims abstract description 72
- 230000001133 acceleration Effects 0.000 claims abstract description 46
- 238000000034 method Methods 0.000 claims abstract description 29
- 239000011248 coating agent Substances 0.000 claims abstract description 28
- 238000005507 spraying Methods 0.000 claims abstract description 26
- 239000007788 liquid Substances 0.000 claims abstract description 25
- FFUAGWLWBBFQJT-UHFFFAOYSA-N hexamethyldisilazane Chemical group C[Si](C)(C)N[Si](C)(C)C FFUAGWLWBBFQJT-UHFFFAOYSA-N 0.000 claims description 54
- 238000001816 cooling Methods 0.000 claims description 22
- 239000003085 diluting agent Substances 0.000 claims description 15
- 239000011230 binding agent Substances 0.000 claims description 12
- 239000011247 coating layer Substances 0.000 claims description 3
- 230000003068 static effect Effects 0.000 claims description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 3
- 238000005406 washing Methods 0.000 claims description 2
- 239000004065 semiconductor Substances 0.000 abstract description 3
- 230000008569 process Effects 0.000 description 23
- 238000004026 adhesive bonding Methods 0.000 description 19
- 238000010586 diagram Methods 0.000 description 19
- 239000007921 spray Substances 0.000 description 14
- 239000003292 glue Substances 0.000 description 13
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical group [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 10
- 239000012071 phase Substances 0.000 description 10
- 229910052710 silicon Inorganic materials 0.000 description 10
- 239000010703 silicon Substances 0.000 description 10
- 230000001105 regulatory effect Effects 0.000 description 6
- 238000004528 spin coating Methods 0.000 description 6
- 230000007547 defect Effects 0.000 description 5
- 238000007711 solidification Methods 0.000 description 4
- 230000008023 solidification Effects 0.000 description 4
- 230000009471 action Effects 0.000 description 3
- 238000001179 sorption measurement Methods 0.000 description 3
- 238000004544 sputter deposition Methods 0.000 description 3
- 239000000758 substrate Substances 0.000 description 3
- 230000008901 benefit Effects 0.000 description 2
- 230000004927 fusion Effects 0.000 description 2
- 239000002904 solvent Substances 0.000 description 2
- 238000003892 spreading Methods 0.000 description 2
- 230000007480 spreading Effects 0.000 description 2
- 239000012808 vapor phase Substances 0.000 description 2
- 239000002699 waste material Substances 0.000 description 2
- 238000009825 accumulation Methods 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000004140 cleaning Methods 0.000 description 1
- 238000010073 coating (rubber) Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 230000005484 gravity Effects 0.000 description 1
- 230000005660 hydrophilic surface Effects 0.000 description 1
- 230000005661 hydrophobic surface Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000004806 packaging method and process Methods 0.000 description 1
- 238000001259 photo etching Methods 0.000 description 1
- 230000000704 physical effect Effects 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 239000011800 void material Substances 0.000 description 1
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- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
- G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
- G03F7/16—Coating processes; Apparatus therefor
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- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
- G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
- G03F7/16—Coating processes; Apparatus therefor
- G03F7/162—Coating on a rotating support, e.g. using a whirler or a spinner
-
- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
- G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
- G03F7/16—Coating processes; Apparatus therefor
- G03F7/168—Finishing the coated layer, e.g. drying, baking, soaking
-
- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
- G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
- G03F7/70—Microphotolithographic exposure; Apparatus therefor
- G03F7/708—Construction of apparatus, e.g. environment aspects, hygiene aspects or materials
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- Public Health (AREA)
- Exposure Of Semiconductors, Excluding Electron Or Ion Beam Exposure (AREA)
Abstract
The application belongs to the technical field of semiconductor integrated circuits, and particularly relates to a photoresist coating method. The photoresist coating method comprises the following steps: the method comprises the steps of spraying an adhesive for improving the adhesive force of photoresist on the first surface of a wafer, dripping a first preset amount of first liquid on the first surface of the wafer, driving the wafer to rotate at a first acceleration so that the first liquid moves from a dripping point to the edge direction of the wafer, enabling the adhesive to be uniformly spread on the first surface of the wafer through the movement of the first liquid, dripping a second preset amount of photoresist on the center of the wafer, driving the wafer to rotate at a second acceleration to enable the second preset amount of photoresist to spread on the first surface within a first time period after the photoresist is dripped, and driving the wafer to rotate at a preset rotating speed within a second time period so as to form a photoresist coating with uniform thickness on the first surface of the wafer, wherein the first time period is smaller than the second time period. The photoresist coating method can spin-coat ultrathin and high-uniformity photoresist on the surface of the wafer.
Description
Technical Field
The application relates to the technical field of semiconductor integrated circuits and advanced packaging, in particular to a photoresist coating method.
Background
The photoresist is coated, namely, a thin, uniform and defect-free photoresist film is established on the surface of the wafer. The non-uniformity is generally 3% -5% in the ultra-thin thickness range within 100nm of the target photoresist thickness. The photoresist coating on the wafer generally adopts a traditional secondary coating mode, the thickness of the middle of the wafer after the photoresist coating is higher than the thickness of the edge after the photoresist coating is carried out by the secondary coating, which is different from the primary coating film forming method, because the secondary photoresist coating is carried out on the basis of the previous photoresist film, the secondary photoresist coating film and the first photoresist film can be subjected to secondary fusion physical action, especially the central photoresist dripping position, the fusion time of the photoresist solution in the center of the wafer and the previous photoresist film is longest, the middle solvent consumption is faster, the edge solvent consumption is slower, the concentration gradient difference of the photoresist coating solution is formed, the middle of the photoresist coating is obviously thicker than the edge, and the photoresist at the edge after solidification can be wrinkled.
Disclosure of Invention
The embodiment of the application provides a photoresist coating method, which can solve the problems of low spin coating efficiency and low process yield of ultrathin photoresist.
The photoresist coating method provided by the embodiment of the application is used for coating photoresist on the surface of a wafer, and comprises the following steps:
spraying an adhesive for improving the adhesive force of the photoresist on the first surface of the wafer,
dropping a first predetermined amount of a first liquid on a first surface of the wafer, driving the wafer to rotate at a first acceleration to move the first liquid from the dropping point to an edge direction of the wafer, so that the adhesive is uniformly spread on the first surface of the wafer by the movement of the first liquid,
dropping a second predetermined amount of photoresist to the center of the wafer, driving the wafer to rotate at a second acceleration during a first period of time after the completion of the photoresist dropping so that the second predetermined amount of photoresist spreads out on the first surface, driving the wafer to rotate at a predetermined rotation speed during a second period of time so as to form a photoresist coating layer having a uniform thickness on the first surface of the wafer,
wherein the first time period is less than the second time period.
According to an embodiment of the first aspect of the present application, spraying an adhesive for improving the adhesion of photoresist on the first surface of the wafer includes:
sending the wafer into the cavity of the binder unit, spraying the gas-phase binder on the first surface of the wafer,
the temperature in the cavity of the adhesive unit is more than or equal to 90 ℃.
According to any one of the foregoing embodiments of the first aspect of the present application, the first surface of the wafer is sprayed with an adhesive for improving the adhesion of the photoresist, and then comprises
The wafer is sent into a cooling cavity, and the temperature of the cooling cavity is reduced to below 30 ℃.
According to any one of the foregoing embodiments of the first aspect of the present application, the value of the first acceleration gradually increases, the maximum value of the first acceleration is 5000RPM/S or more, and the time for driving the wafer to rotate with the first acceleration is 30S or less.
According to any of the foregoing embodiments of the first aspect of the present application, the time for spraying the adhesive on the first surface of the wafer is 40 seconds or less.
According to any one of the foregoing embodiments of the first aspect of the present application, the first period is less than or equal to 5 seconds, the second acceleration gradually increases from the initial value to the maximum value in the first period, and the second acceleration is greater than or equal to 5000RPM/S and less than or equal to 20000RPM/S.
According to any one of the foregoing embodiments of the first aspect of the present application, the wafer is driven to rotate at a predetermined rotational speed for a second period of time to form a photoresist coating of uniform thickness on the first surface of the wafer, comprising
And in a second time period after the first time period, changing the acceleration of the wafer to enable the wafer to rotate at a constant speed at a preset rotating speed, wherein the time for the wafer to rotate at the constant speed at the preset rotating speed is less than or equal to 40 seconds so as to form a photoresist coating with uniform thickness on the first surface of the wafer.
According to any of the foregoing embodiments of the first aspect of the present application, the photoresist dropper for dropping photoresist onto the wafer remains relatively stationary with the wafer while a second predetermined amount of photoresist is dropped onto the center of the wafer.
According to any of the foregoing embodiments of the first aspect of the present application, the photoresist dropper for dropping photoresist onto the wafer has the same rotational speed as the wafer or is stationary when dropping a second predetermined amount of photoresist onto the center of the wafer.
According to any of the foregoing embodiments of the first aspect of the present application, the predetermined rotational speed is calculated as follows:
wherein A represents the rotation speed required by the wafer to reach the target photoresist thickness,
b represents the size of the wafer and,
c represents the average value of the wafer photoresist film thickness currently measured,
d represents the target photoresist thickness average for the wafer,
e represents the current rotational speed of the wafer,
f represents a correction factor, and the value of the correction factor is related to the photoresist adhesiveness.
According to any of the foregoing embodiments of the first aspect of the present application, the binder is HMDS;
or (b)
The first liquid is water or a diluent capable of washing out the photoresist.
According to any one of the foregoing embodiments of the first aspect of the present application, the first predetermined amount has a value ranging from 0.1mL to 0.5mL;
or (b)
The second predetermined amount is 1 mL-5 mL (for photoresist film with thickness of 20-100 nm).
According to the photoresist coating method, after the step of spraying the adhesive, the first liquid is spread on the surface of the wafer, so that the first liquid generates thrust to the adhesive sprayed on the first surface of the wafer in the process of moving from the dropping point to the edge of the wafer, the adhesive piled in an atomized manner is paved, the adhesive is further evenly spread on the first surface of the wafer, the HMDS is evenly distributed, the interface structure of the wafer is changed, the property of the wafer is changed from a hydrophilic surface to a hydrophobic surface, the adhesive force of the photoresist can be increased, and the spin coating efficiency of the photoresist is improved. And in the process of the subsequent photoresist spin coating, the process is carried out in two time periods, and in the first time period, the value of the second acceleration is rapidly increased, so that the photoresist can be instantly thrown to all parts of the first surface of the wafer after being dripped on the first surface of the wafer, and the photoresist is spread on the first surface, so that the peak defect is prevented from being formed at the dripping part of the photoresist. And in a second time period, the wafer rotates at a constant speed, so that the spread photoresist can keep high uniformity in the target thickness. The whole photoresist coating method can spin-coat ultra-thin (20-100 nm) and high-uniformity (unevenness less than 1%) photoresist on the surface of the wafer.
Drawings
Fig. 1 is a schematic structural diagram of a wafer according to an embodiment of the present application;
FIG. 2 is a flow chart of a photoresist coating method of an embodiment of the present application;
FIG. 3 is a schematic diagram of a cold-hot chamber used in the photoresist coating method according to the embodiment of the present application;
FIG. 4 is a schematic diagram illustrating the operation of the photoresist coating unit chamber used in the photoresist coating method according to the embodiment of the present application;
FIG. 5 is a 6 inch wafer glue contour plot obtained using the photoresist coating method of the embodiments of the present application;
FIG. 6 is a plot of an 8 inch wafer glue line profile obtained using the photoresist coating method of an embodiment of the present application;
FIG. 7 is a plot of a 12 inch wafer glue line profile obtained using the photoresist coating method of an embodiment of the present application;
fig. 8 is a schematic diagram of a defect of a conventional gumming process.
Detailed Description
Features and exemplary embodiments of various aspects of the present application are described in detail below to make the objects, technical solutions and advantages of the present application more apparent, and to further describe the present application in conjunction with the accompanying drawings and the detailed embodiments. It should be understood that the specific embodiments described herein are intended to be illustrative of the application and are not intended to be limiting. It will be apparent to one skilled in the art that the present application may be practiced without some of these specific details. The following description of the embodiments is merely intended to provide a better understanding of the present application by showing examples of the present application.
The wafer is a silicon wafer used for manufacturing a silicon semiconductor circuit, and the silicon wafer is generally classified into 6 inch, 8 inch, and 12 inch specifications because of its circular shape. The larger the diameter, the lower the cost of the final single chip, but the higher the processing difficulty. The wafer is in the shape of a circular sheet as shown in fig. 1, and the wafer S04 includes a first surface 1 and a second surface (not shown) opposite to each other, and a photoresist is coated on the first surface 1.
Referring to fig. 2, an embodiment of the present application provides a photoresist coating method for coating a photoresist on a wafer surface, the method including steps S1 to S3.
S1, spraying an adhesive for improving the adhesive force of photoresist on the first surface of the wafer.
The adhesive has the function of improving the adhesiveness of the wafer and the photoresist, and the photoresist can be firmly adhered to the first surface of the wafer in the subsequent process of spin coating the photoresist through the function of the adhesive. In some embodiments, the binder may be Hexamethyldisilazane (HMDS).
In some examples, the adhesive is sprayed on the first surface of the wafer by a vapor-phase spraying method, and the liquid HMDS is converted into a gaseous state by the vapor-phase spraying method and is coated and adsorbed on the surface of the wafer, so that the utilization rate of the HMDS is improved, and the cost is reduced. Specifically, step S1 includes:
s11, conveying the wafer into a cavity of the adhesive unit, and keeping the temperature in the cavity of the adhesive unit to be more than or equal to 90 ℃;
and S12, spraying the gas-phase adhesive on the first surface of the wafer.
Preferably, the temperature in the cavity of the binder unit is in the range of 90 ℃ to 200 ℃. The temperature range can keep the binder in a stable gas phase state, does not change the characteristics of the HMDS, and is favorable for the coating uniformity of the HMDS on the surface of the wafer.
S2, first liquid is dripped on the first surface of the wafer by a first preset amount, the wafer is driven to rotate by first acceleration, the first liquid moves from the dripping point to the edge direction of the wafer, and the adhesive is uniformly spread on the first surface of the wafer through the movement of the first liquid.
If the time for spraying the gas-phase adhesive on the first surface of the wafer is too short, uneven phenomena can occur, so that the thickness of the subsequent photoresist is possibly uneven, and the yield of the photoetching spin coating process is low. Through step S2, in the process of moving the first liquid from the dropping point to the edge of the wafer, thrust is generated on the adhesive sprayed on the first surface of the wafer, and the accumulated adhesive is paved, so that the adhesive is uniformly paved on the first surface of the wafer. Through step S2, the time for spraying the adhesive to the first surface of the wafer can be shortened, and the spin coating efficiency of the photoresist can be improved.
The first liquid is generally non-reactive with the binder and does not alter the physical and chemical properties of the binder, for example, the first liquid may be water. Preferably, the first liquid is a material that is required for use in a photoresist coating process, for example, a diluent that is capable of cleaning the photoresist. The original purpose of the thinner is to clean the redundant photoresist on the back and the edge of the wafer, which is an indispensable step in the photoresist coating process, so that the use of the thinner for the first liquid does not increase the equipment needed in the photoresist coating method, and only the execution sequence of the existing equipment is required to be adjusted. It should be noted that although the thinner will wash away the photoresist, in step S2, the thinner is moved to the edge of the wafer by rotating the wafer rapidly, and most of the thinner is thrown away from the wafer surface by the centrifugal force, so that the subsequent photoresist coating is not affected.
In the specific implementation, the spray pipe capable of spraying the diluent is moved to the center of the wafer coated with the adhesive and is positioned above the first surface of the wafer, a first preset amount of diluent is dripped to the center of the first surface, and then the wafer is rotated at a high acceleration, so that the adhesive adsorbed on the surface of the wafer can be instantaneously spread under the action of a high centrifugal force by the diluent, and the spreading efficiency of the adhesive is improved.
In some embodiments, the value of the first acceleration is gradually increased, the maximum value of the first acceleration is 5000RPM/S or more, and the time for driving the wafer to rotate at the first acceleration is 30 seconds or less. In step S2, the acceleration value of the wafer increases linearly, and gradually increases from zero to about 10000RPM/S within 30 seconds, and the rapidly increasing centrifugal force is utilized to move toward the edge of the wafer instantaneously, so that the accumulated adhesive is uniformly spread on the first surface of the wafer during the movement. The wafer is driven to rotate by the first acceleration for too long, so that the HMDS is taken away too much, the bonding capacity of the edge of the wafer is poor, and the probability of generating glue coating defects on the edge of the wafer is increased.
In the traditional adhesive spraying process, if the adhesive spraying time is too short, the adhesive is unevenly distributed on the surface of the wafer, and a local accumulation phenomenon is caused; in order to uniformly spread the adhesive on the surface of the wafer, the adhesive is sprayed on the surface of the wafer for more than 2 minutes, so that the whole gluing process is longer due to longer spraying time on one hand, and the purpose of uniformly coating the adhesive on the surface of the mirror surface can be achieved on the premise of consuming a large amount of adhesive on the other hand, most of the adhesive drops to the bottom of the cavity of the adhesive unit under the action of gravity. The adhesive that has accumulated originally can be spread out rapidly on the first surface under the action of step S2, so that in step S1, the adhesive does not need to be sprayed to the first surface for a long time in order to uniformly spread the adhesive over the first surface. In some embodiments, the time to spray the adhesive on the first surface of the wafer is 40 seconds or less. The spraying time of the adhesive is greatly shortened compared with the spraying of the adhesive to the first surface which takes more than 2 minutes in the conventional process.
In some embodiments, the first predetermined amount has a value in the range of 0.1mL to 0.5mL. The first liquid has the effects that the accumulated adhesive is uniformly spread, so that the adhesive is not too little or too much, the purpose of uniformly spreading the adhesive cannot be achieved, the waste of the first liquid is caused by too much, the rotation time is increased, the first liquid is excessively remained on a wafer, and the subsequent gluing process is influenced; the range of 0.1-0.5 mL can enhance the cohesive force of the adhesive, improve the gluing uniformity and improve the wafer processing yield.
S3, dripping a second preset amount of photoresist to the center of the wafer, driving the wafer to rotate at a second acceleration in a first time period after the photoresist is dripped so as to spread the second preset amount of photoresist on the first surface, and driving the wafer to rotate at a preset rotating speed in a second time period so as to form a photoresist coating with uniform thickness on the first surface of the wafer; wherein the first time period is less than the second time period.
In the traditional photoresist coating process, when photoresist is dropped onto a wafer, the wafer at the bottom is rotated at a constant speed, so that the photoresist is spread on the surface of the wafer, but the process is easy to form bulges at the photoresist dropping position of the wafer, so that the non-uniformity of the whole photoresist coating in the nanometer thickness range is increased. In step S3 of the embodiment of the present application, the first period of time is shorter than the second period of time. In the first time period, the value of the second acceleration is rapidly increased, so that the photoresist can be instantly thrown to all parts of the first surface of the wafer after being dripped on the first surface of the wafer, and the photoresist is spread on the first surface, so that a peak is prevented from being formed at the dripping part of the photoresist. And in a second time period, the wafer rotates at a constant speed, so that the spread photoresist maintains high uniformity in a target thickness range.
In some embodiments, the first period of time is less than or equal to 5 seconds, the second acceleration increases rapidly from an initial value to a maximum value over the first period of time, the second acceleration being greater than or equal to 5000RPM/S and less than or equal to 20000RPM/S. By utilizing the instantaneously increased second acceleration, the centrifugal force of the photoresist dropped in the center of the wafer is improved, the thickness of the photoresist in the center of the wafer is reduced, and the occurrence of convex defects can be avoided. The second acceleration value which is too small is insufficient to solve the peak-shaped defect of the photoresist at the center of the wafer; an excessive second acceleration value (for example, more than 20000 RPM/S) may generate excessive centrifugal force, and may separate the photoresist from the wafer surface, and a void problem may occur at a local interface, so that the second acceleration is preferably 5000RPM/S to 20000RPM/S.
In some embodiments, the wafer is driven to rotate at a predetermined rotational speed for a second period of time to form a photoresist coating layer having a uniform thickness on the first surface of the wafer, specifically comprising: and in a second time period after the first time period, changing the acceleration of the wafer to enable the wafer to rotate at a constant speed at a preset rotating speed, wherein the time for the wafer to rotate at the constant speed at the preset rotating speed is less than or equal to 40 seconds, so that a photoresist coating with uniform thickness is formed on the first surface of the wafer. In the second time period, the rotation acceleration of the wafer is reduced to zero, so that the wafer rotates at a constant speed at a preset rotating speed, the wafer maintains the constant rotating speed, the airflow velocity at the edge of the wafer can be reduced, and the problem of uniformity of gluing of the edge of the wafer is solved.
In some embodiments, to increase the efficiency of the prediction of the predetermined rotational speed, the trial-and-error rate is reduced, the predetermined rotational speed being calculated by the following equation:
wherein A represents the rotation speed required by the wafer to reach the target photoresist thickness, B represents the size (inch) of the wafer, C represents the average value of the photoresist film thickness of the wafer measured currently, D represents the average value of the photoresist thickness of the wafer, E represents the current rotation speed of the wafer, F represents the correction factor (which is a dimensionless parameter), the value of the correction factor is related to the selection of the photoresist, different photoresist adhesives are different, and the correction factor is different. By this calculation, the rotational speed required for the wafer to reach the target photoresist thickness can be predicted faster.
In some embodiments, to improve the thickness uniformity of the photoresist coating, a photoresist dropper for dropping photoresist onto the wafer remains relatively stationary with the wafer while a second predetermined amount of photoresist is dropped onto the center of the wafer. In the conventional photoresist dropping process, when photoresist is dropped onto the surface of a wafer, the wafer is generally in a state of uniform rotation, which causes uneven acting force in a certain direction when the photoresist contacts the surface of the wafer, so that the photoresist thickness in a certain direction or area of the wafer is thicker than that in other directions or areas. In the embodiment of the application, when the photoresist is dripped on the surface of the wafer, the photoresist dropper for dripping the photoresist on the wafer and the wafer are kept in a relatively static state, so that the photoresist is not subjected to uneven force due to the rotation speed difference between the photoresist and the wafer when the photoresist is dripped on the surface of the wafer, and the thickness of the photoresist coating is more uniform.
In some embodiments, the photoresist dropper for dropping photoresist onto the wafer has the same rotational speed as the wafer or is stationary while dropping a second predetermined amount of photoresist onto the center of the wafer. Preferably, in order to improve efficiency, when a second predetermined amount of photoresist is dropped to the center of the wafer, the photoresist dropper for dropping the photoresist to the wafer has the same rotation speed as the wafer, and the rotation axes are coincident. Since the wafer has already started to rotate in step S2 before the photoresist is dropped, in order to avoid stopping and restarting, the current rotation state of the wafer is maintained, so that the photoresist dropper and the wafer have the same rotation speed, and the rotation axes are coincident. Therefore, when the photoresist drops on the wafer, the photoresist can be kept relatively static with the wafer, and the photoresist is uniformly stressed in all directions when contacting the wafer interface.
In some embodiments, the second predetermined amount has a value in the range of 1mL to 5mL. If too much photoresist is dropped on the surface of the wafer, waste is caused, and on the one hand, the photoresist dropper may need to drop the photoresist several times to finish the photoresist dropping step, and the photoresist dropping interval can enter air, so that bubbles exist in the photoresist on the surface of the wafer. In the embodiment of the application, the photoresist dropping amount of 1 mL-5 mL can meet the requirement of photoresist thickness, and meanwhile, photoresist can be dropped once to the surface of the wafer, so that bubbles are prevented from being generated in photoresist dropping for multiple times.
In some embodiments, step S21 is included after step S1.
S21, conveying the wafer into a cooling cavity, and reducing the temperature of the cooling cavity to below 30 ℃. Because the temperature that the wafer is located when in binder unit cavity is higher, is greater than 90 ℃, consequently, in order to give the wafer rapid cooling, send into the cooling cavity with the wafer in, fall the temperature of cooling cavity below 30 ℃, make the wafer can the rapid cooling to the settlement temperature, the HMDS of atomizing state can be more adsorb on the wafer surface to do benefit to the step of follow-up rubber coating.
For the purpose of facilitating an understanding of the embodiments of the present application, the following description is made in terms of specific examples, which are not to be construed as limiting the embodiments of the present application.
Example 1
Step one, a FOUP (Front Opening Unified Pod ) with a 6 inch wafer is placed onto a stage.
And step two, conveying the 6-inch wafer into a cavity of the adhesive unit, wherein the temperature of the cavity of the adhesive unit is between 90 and 100 ℃, and spraying HMDS (hexamethyldisilazane) on the surface of the silicon wafer in a gas phase manner for 10 to 15 seconds, so that the adhesive force between the surface of the wafer and the photoresist is increased.
And thirdly, the wafer sprayed with the HMDS enters a cooling cavity, a schematic diagram of the cooling cavity is shown in fig. 3, and the wafer is rapidly cooled to 25 ℃.
Step four, entering a gluing unit cavity, wherein the working schematic diagram of the gluing unit cavity is shown in fig. 4, the cooled wafer is transmitted to a sucker of a rotating motor S06, the wafer S04 is fixed, a diluent spray pipe S02 is moved to the position above the center of a wafer substrate coated with HMDS, the direction of a diluent spray nozzle S03 is regulated, 0.1-0.5 mL of diluent is dripped to the wafer, the wafer is pre-rinsed, the wafer is rotated clockwise (or anticlockwise), the rotating acceleration is 8000RPM/S, the rotating time is 15S, and the HMDS (hexamethyldisilazane) of a gas phase adsorbed on a silicon wafer is uniformly spread on the first surface of the wafer instantly, so that a foundation is provided for gluing uniformity.
And fifthly, after the pre-rinsing is finished, moving the photoresist dropper S01 to the position above the center of the wafer, and dripping photoresist to the wafer, wherein the photoresist dripping amount is controlled within 1-5 mL. The wafer rotation process after the glue dropping comprises two stages. In the first stage, at the moment of glue dripping, rotational acceleration rises to 5000-20000 RPM/S within 0.5-5S, rotational speed rises to 1000-3000 RPM, and photoresist in the center of the wafer is spread on the surface of the wafer. And in the second stage, the rotational acceleration is reduced to be kept at the speed corresponding to the preset rotational speed calculated by the rotational speed empirical formula (1), and then the acceleration is reduced to 0RPM/S, and the uniform motion is continued. The correction factor in the empirical formula is related to the photoresist viscosity, and the photoresist viscosity is corresponding to the correction factor of 0.05-0.2 when 500-3000 centipoises, and the uniform rotation time is 20-40 s, so that the corresponding photoresist thickness is obtained. The rotating direction S07 of the motor is clockwise (or anticlockwise), and the photoresist is sputtered on the photoresist adsorption barrel S05, so that the photoresist rapidly slides downwards due to smooth surface, and the photoresist is prevented from sputtering and rebounding to the wafer.
And step six, after the gluing is finished, the thinner spray pipe S02 is moved to clean the back surface and the edge of the wafer, the direction of the thinner spray nozzle S03 is regulated, and the residual photoresist on the back surface and the edge of the wafer is cleaned.
And step seven, after the gluing is finished, the wafer is sent into a cooling cavity, a schematic diagram of the cooling cavity is shown in fig. 3, and the temperature is quickly increased to 100 ℃ for solidification.
And performing spot check on the wafer, and measuring the unevenness of the adhesive surface of the wafer. The calculation formula of the unevenness of the rubber surface is as follows
The non-uniformity is less than or equal to 1 percent and is qualified, and qualified process products can enter an exposure machine for exposure. FIG. 5 shows a 6 inch wafer with a glue thickness of +.>
The contour diagram is calculated, and the non-uniformity of the contour diagram meets the requirement. It can be seen that the present embodiment solves the drawbacks of the conventional gumming process shown in fig. 8.
Example 2
Step one, a FOUP with an 8 inch wafer is placed on a stage.
Step two, an 8-inch wafer enters into a cavity of an adhesive unit, the temperature of the cavity of the adhesive unit is between 100 and 120 ℃, HMDS (hexamethyldisilazane) is sprayed on the surface of a silicon wafer in a gas phase mode, and the spraying time is 10 to 20 seconds, so that the adhesive force between the surface of the wafer and photoresist is increased.
And thirdly, the wafer sprayed with the HMDS enters a cooling cavity, a schematic diagram of the cooling cavity is shown in fig. 3, and the wafer is rapidly cooled to 23 ℃.
Step four, entering a gluing unit cavity, wherein the working schematic diagram of the gluing unit cavity is shown in fig. 4, the cooled wafer is transmitted to a sucker of a rotating motor S06, the wafer S04 is fixed, a diluent spray pipe S02 is moved to the position above the center of a wafer substrate coated with HMDS, the direction of a diluent spray nozzle S03 is regulated, 0.3-0.5 mL of diluent is dripped to the wafer, the wafer is pre-rinsed, the wafer is rotated clockwise (or anticlockwise), the rotating acceleration is 10000RPM/S, the rotating time is 20S, and the HMDS (hexamethyldisilazane) gas phase adsorbed on the silicon wafer is uniformly spread on the surface of the whole silicon wafer instantly, so that a foundation is provided for gluing uniformity.
And fifthly, after the pre-rinsing is finished, moving the photoresist drip S01 pipe to the upper part of the center of the wafer, and dripping photoresist to the wafer, wherein the photoresist dripping amount is controlled within 3-5 mL. The wafer rotation process after the glue dropping comprises two stages. In the first stage, at the moment of glue dripping, the rotation speed is increased to 5000-20000 RPM/S within 2-5S, the rotation speed is increased to 1000-3000 RPM, and the photoresist in the center of the wafer is spread on the surface of the wafer. And in the second stage, the rotational acceleration is reduced to be kept at the speed corresponding to the preset rotational speed calculated by the rotational speed empirical formula (1), and then the acceleration is reduced to 0RPM/S, and the uniform motion is continued. The correction factor in the empirical formula is related to the photoresist viscosity, and the photoresist viscosity is corresponding to the correction factor of 0.05-0.2 when 500-3000 centipoises, and the uniform rotation time is 30-40 s, so that the corresponding photoresist thickness is obtained. The rotation direction S0) of the motor is clockwise (or anticlockwise), the photoresist is sputtered on the photoresist adsorption barrel S05, and the photoresist rapidly slides down due to smooth surface, so that the photoresist is prevented from sputtering and rebounding to the wafer.
And step six, after the gluing is finished, the thinner spray pipe S02 is moved to clean the back surface and the edge of the wafer, the direction of the thinner spray nozzle S03 is regulated, and the residual photoresist on the back surface and the edge of the wafer is cleaned.
And step seven, after the gluing is finished, the wafer is sent into a cooling cavity, a schematic diagram of the cooling cavity is shown in fig. 3, and the temperature is quickly increased to 120 ℃ for solidification.
And performing spot check on the wafer, and measuring the unevenness of the adhesive surface of the wafer. The calculation formula of the unevenness of the rubber surface is as follows
The non-uniformity is less than or equal to 1 percent and is qualified, and qualified process products can enter exposureExposing by a machine. FIG. 6 shows an 8 inch wafer with a glue thickness of +.>
The contour diagram is calculated, and the non-uniformity of the contour diagram meets the requirement. It can be seen that the present embodiment solves the drawbacks of the conventional gumming process shown in fig. 8.
Example 3
Step one, a FOUP with a 12 inch wafer is placed on a stage.
And step two, conveying the 12-inch wafer into a cavity of the adhesive unit, wherein the temperature of the cavity of the adhesive unit is 120-150 ℃, and spraying HMDS (hexamethyldisilazane) on the surface of the silicon wafer in a gas phase manner for 20-30 s, so that the adhesive force between the surface of the wafer and the photoresist is increased.
And thirdly, the wafer sprayed with the HMDS enters a cooling cavity, a schematic diagram of the cooling cavity is shown in fig. 3, and the wafer is rapidly cooled to 28 ℃.
Step four, entering a gluing unit cavity, wherein the working schematic diagram of the gluing unit cavity is shown in fig. 4, the cooled wafer is transmitted to a sucker of a rotating motor S06, the wafer S04 is fixed, a diluent spray pipe S02 is moved to the position above the center of a wafer substrate coated with HMDS, the direction of a diluent spray nozzle S03 is regulated, 0.4-0.5 mL of diluent is dripped to the wafer, the wafer is pre-rinsed, the wafer is rotated clockwise (or anticlockwise), the rotating acceleration is 20000RPM/S, the rotating time is 10S, and the HMDS (hexamethyldisilazane) of a gas phase adsorbed on a silicon wafer is uniformly spread on the first surface of the wafer instantly, so that a foundation is provided for gluing uniformity.
And fifthly, after the pre-rinsing is finished, moving the photoresist dropper S01 to the position above the center of the wafer, and dripping photoresist to the wafer, wherein the photoresist dripping amount is controlled within 3-5 mL. The wafer rotation process after the glue dropping comprises two stages. In the first stage, at the moment of glue dripping, the rotation speed is increased to 5000-20000 RPM/S within 2-5S, the rotation speed is increased to 1000-3000 RPM, and the photoresist in the center of the wafer is spread on the surface of the wafer. And in the second stage, the rotational acceleration is reduced to be kept at the speed corresponding to the preset rotational speed calculated by the rotational speed empirical formula (1), and then the acceleration is reduced to 0RPM/S, and the uniform motion is continued. The correction factor in the empirical formula is related to the photoresist viscosity, and the photoresist viscosity is corresponding to the correction factor of 0.05-0.2 when 500-3000 centipoises, and the uniform rotation time is 30-40 s, so that the corresponding photoresist thickness is obtained. The rotating direction S07 of the motor is clockwise (or anticlockwise), and the photoresist is sputtered on the photoresist adsorption barrel S05, so that the photoresist rapidly slides downwards due to smooth surface, and the photoresist is prevented from sputtering and rebounding to the wafer.
And step six, after the gluing is finished, the thinner spray pipe S02 is moved to clean the back surface and the edge of the wafer, the direction of the thinner spray nozzle S03 is regulated, and the residual photoresist on the back surface and the edge of the wafer is cleaned.
And step seven, after the gluing is finished, the wafer is sent into a cooling cavity, a schematic diagram of the cooling cavity is shown in fig. 3, and the temperature is quickly increased to 150 ℃ for solidification.
And performing spot check on the wafer, and measuring the unevenness of the adhesive surface of the wafer. The calculation formula of the unevenness of the rubber surface is as follows
The non-uniformity is less than or equal to 1 percent and is qualified, and qualified process products can enter an exposure machine for exposure. FIG. 7 shows a 12 inch wafer with a glue thickness of +.>
The contour diagram is calculated, and the non-uniformity of the contour diagram meets the requirement. It can be seen that the present embodiment solves the drawbacks of the conventional gumming process shown in fig. 8.
Claims (12)
1. A photoresist coating method for coating a photoresist on a wafer surface, the method comprising:
spraying an adhesive for improving the adhesive force of the photoresist on the first surface of the wafer,
dropping a first predetermined amount of a first liquid on a first surface of the wafer, driving the wafer to rotate at a first acceleration to move the first liquid from the dropping point to an edge direction of the wafer, so that the adhesive is uniformly spread on the first surface of the wafer by the movement of the first liquid,
dropping a second predetermined amount of photoresist to the center of the wafer, driving the wafer to rotate at a second acceleration during a first period of time after the completion of the photoresist dropping so that the second predetermined amount of photoresist spreads out on the first surface, driving the wafer to rotate at a predetermined rotation speed during a second period of time so as to form a photoresist coating layer having a uniform thickness on the first surface of the wafer,
wherein the first time period is less than the second time period.
2. The method of claim 1, wherein the step of spraying an adhesive for improving adhesion of the photoresist on the first surface of the wafer comprises
Sending the wafer into the cavity of the binder unit, spraying the gas-phase binder on the first surface of the wafer,
the temperature in the cavity of the adhesive unit is more than or equal to 90 ℃.
3. The method of claim 2, wherein the step of spraying an adhesive for improving adhesion of the photoresist on the first surface of the wafer comprises
The wafer is sent into a cooling cavity, and the temperature of the cooling cavity is reduced to below 30 ℃.
4. The photoresist coating method according to claim 1, wherein: the value of the first acceleration is gradually increased, the maximum value of the first acceleration is more than or equal to 5000RPM/S, and the time for driving the wafer to rotate by the first acceleration is less than or equal to 30 seconds.
5. The photoresist coating method according to claim 4, wherein: and spraying the adhesive on the first surface of the wafer for 40 seconds or less.
6. The photoresist coating method according to claim 1, wherein: the first time period is less than or equal to 5 seconds, the second acceleration gradually increases to a maximum value from an initial value in the first time period, and the second acceleration is more than or equal to 5000RPM/S and less than or equal to 20000RPM/S.
7. The photoresist coating method according to claim 1, wherein: the wafer is driven to rotate at a preset rotating speed in a second time period to form a photoresist coating with uniform thickness on the first surface of the wafer, which comprises
And in a second time period after the first time period, changing the acceleration of the wafer to enable the wafer to rotate at a constant speed at a preset rotating speed, wherein the time for the wafer to rotate at the constant speed at the preset rotating speed is less than or equal to 40 seconds so as to form a photoresist coating with uniform thickness on the first surface of the wafer.
8. The photoresist coating method according to claim 1, wherein:
and when a second preset amount of photoresist is dripped to the center of the wafer, the photoresist dropper for dripping the photoresist to the wafer is kept in a relatively static state with the wafer.
9. The photoresist coating method according to claim 8, wherein: when a second predetermined amount of photoresist is dropped toward the center of the wafer, the photoresist dropper used to drop the photoresist toward the wafer has the same rotational speed as the wafer or is stationary.
10. The photoresist coating method according to claim 1, wherein the predetermined rotation speed is calculated as follows:
wherein A represents the rotation speed required by the wafer to reach the target photoresist thickness,
b represents the size of the wafer and,
c represents the average value of the wafer photoresist film thickness currently measured,
d represents the target photoresist thickness average for the wafer,
e represents the current rotational speed of the wafer,
f represents a correction factor, and the value of the correction factor is related to the photoresist adhesiveness.
11. The photoresist coating method according to claim 1, wherein: the binder is HMDS;
or (b)
The first liquid is water or a diluent capable of washing out the photoresist.
12. The photoresist coating method according to claim 1, wherein: the value range of the first preset quantity is 0.1 mL-0.5 mL;
or (b)
The value range of the second preset quantity is 1 mL-5 mL.
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| CN118707809A (en) * | 2024-07-16 | 2024-09-27 | 浙江大学 | A coating method for optimizing photoresist uniformity using ultrasonic waves |
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| CN118707809A (en) * | 2024-07-16 | 2024-09-27 | 浙江大学 | A coating method for optimizing photoresist uniformity using ultrasonic waves |
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