WO2017154634A1 - Light-processing device, and method for adjusting interval between surface of object to be processed and window member - Google Patents

Abstract

Disclosed are a light-processing device 100 for equalizing processing by equalizing gaps, and a method for adjusting the interval between the surface of an object to be processed and a window member 12. One aspect of the light-processing device is provided with: a light source unit for emitting light; a processing unit 20 in which the surface of the object to be processed is exposed to light emitted from the light source unit in a processing gas atmosphere; a window member that separates the light source unit and the processing unit, the window member transmitting light emitted from the light source unit; a gas-charging/discharging unit for channeling the processing gas along the surface between the surface of the object to be processed and the window member; and a differential-pressure-regulating unit for regulating the pressure difference of both sides separated by the window member while the processing gas is flowing.

Description

Light processing apparatus, and method of adjusting distance between surface of object to be treated and window member

BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a light processing apparatus and a method of adjusting the distance between the surface of an object to be processed and a window member. More specifically, the present invention relates to a light processing apparatus suitable for, for example, smear removal (desmear) processing in a printed circuit board manufacturing process, and a distance between a surface of an object to be processed and a window member used in the light processing apparatus. It relates to the adjustment method.

Conventionally, for example, light ashing processing of resist in manufacturing process of semiconductor, liquid crystal panel, etc. removal processing of resist adhering to the pattern surface of template in nanoimprint apparatus, dry cleaning processing of glass substrate for liquid crystal, silicon wafer etc., printed substrate BACKGROUND ART A light processing apparatus and a light processing method using ultraviolet light are known as a light processing apparatus and a light processing method used for smear removal (desmear) processing and the like in a manufacturing process. In particular, an apparatus or method using active species such as ozone or oxygen radicals generated by vacuum ultraviolet radiation emitted from an excimer lamp etc. is suitably used because it can perform predetermined processing more efficiently in a short time. It is done.

For example, Patent Document 1 (Japanese Patent Laid-Open No. 2015-120129) proposes a method of irradiating the substrate with ultraviolet light as a desmear process for the via hole, and the substrate on which the via hole is formed is irradiated with ultraviolet light under an atmosphere containing oxygen. It has been proposed to do. When oxygen is irradiated with ultraviolet light, active species such as ozone and oxygen radicals are generated. The smear combines with these active species and is removed as carbon dioxide and water vapor. Then, carbon dioxide and water vapor are exhausted to the outside of the processing chamber as exhaust gas.

The processing chamber in which the object to be processed (workpiece) such as a substrate is placed is separated from the light source emitting ultraviolet light by the transparent window member, and the distance between the window member and the work is as narrow as 1 mm or less It is set to. And, during the light processing, the distance between the window member and the work (the distance from the lower surface of the window member to the surface of the work, hereinafter, this distance is also called "gap") is equal over the entire surface of the work There is a need.
Because the UV rays from the light source are absorbed by the processing gas flowing in the processing chamber, if the gap is non-uniform, the amount of UV rays reaching the work becomes non-uniform depending on the location of the work, which causes non-treatment. This is because uniformity occurs.
In order to make the gap uniform, suction holes are provided in the mounting table on which the workpiece is placed and vacuum suction is performed to bring the workpiece into close contact with the mounting table, thereby enhancing the flatness of the surface of the workpiece.

JP, 2015-120129, A

However, as the processing accuracy in the desmearing process and the like is improved, it has been found that even if the gap is made uniform by the conventional method as described above, the process becomes nonuniform. Although such non-uniformity in processing was considered to be due to non-uniformity of the gap, the cause of the non-uniformity of such gap was not known.
Then, this invention makes it a subject to equalize a gap and to equalize a process.

In order to solve the above problems, in one aspect of the light processing apparatus according to the present invention, the surface of the object to be treated is exposed to the light emitted from the light source unit and the light emitted from the light source unit in the atmosphere of treatment gas. Processing unit, a window member separating the light source unit and the processing unit and transmitting light emitted from the light source unit, a surface of the object to be processed and the window member along the surface And a differential pressure adjusting unit configured to adjust a pressure difference between both sides separated by the window member in a state in which the processing gas flows.

The inventors have found that in the light processing apparatus, the central portion of the window member is lifted to the light source side during light processing (a convex deflection occurs) to cause partial nonuniformity in the gap. Furthermore, as a result of investigating the reason, the inventors found out that the following is the cause.
(1) A differential pressure generated on the inlet side and the outlet side of the gas due to the process gas flowing in the narrow space between the window member and the work.
(2) An increase in internal pressure caused by discharge resistance (pressure loss) in the discharge side piping of the processing gas.
(3) Pushing up the window member by the repulsive force of the O-ring pressed against the periphery of the window member.
In addition, it was also found that the deflection of the window member is not necessarily convex on the light source side, and depending on the conditions, it may be convex on the work side.
If the window member is thickened to make it difficult to bend against such bending of the window member, the distance from the light source to the work becomes longer and the amount of ultraviolet light absorbed by the window member increases. The amount of ultraviolet light reaching the This increases the processing time. In addition, increasing the cost of the window member and increasing the total weight of the device also makes it undesirable to thicken the window member.

According to the light processing apparatus of the present invention, the gap can be easily made uniform by a simple method of adjusting the pressure difference by the differential pressure adjusting unit, and the size reduction and cost of the apparatus can be achieved along with the uniformity of the light processing. It can also contribute to suppression.
In the light processing device, preferably, the differential pressure adjusting unit adjusts an amount of exhaust of the processing gas from the processing unit by the gas supply / discharge unit. In terms of adjusting the pressure difference, although the method of adjusting the supply amount of the processing gas or adjusting the pressure on the light source unit side can also be realized, the influence on the processing capacity of the light processing apparatus is small. The method of adjusting the displacement is superior.

The light processing apparatus further includes a spacer which is interposed between the window member and the surface of the object to be treated to maintain the distance between the window member and the surface, and the differential pressure adjusting unit It is also preferable to adjust the pressure difference so that the pressure on the side of the object to be treated is lower than the pressure on the light source side among the two sides separated by the window member. Since the spacer prevents the window member from coming close to the surface of the object to be treated, the differential pressure adjustment unit makes the gap uniform by simple adjustment to lower the pressure on the object side by a certain amount or more. Can be

Furthermore, in order to solve the above problems, one aspect of the method of adjusting the distance between the surface of the object to be treated and the window member according to the present invention transmits the light and the surface of the object to be treated exposed to light. Adjusting the differential pressure to adjust the pressure difference between the two sides separated by the window member while the processing gas is flowing between the window member and the processing chamber. And a process.
According to such an interval adjusting method, the gap can be easily made uniform by a simple method of adjusting the pressure difference in the pressure difference adjusting process, and the light processing can be made uniform.

The space adjusting method further includes a pressing process for pressing the sealing member elastic than the window member against the peripheral portion of the window member to prevent the leakage of the processing gas, and the differential pressure adjusting process includes the pressing process. The pressure difference between the two sides separated by the window member may be adjusted to a pressure difference according to the pressing strength of the airtight member in the pressing process.
For example, the strength of the pressure applied to the window member may be changed depending on conditions such as the size, material, thickness, surface condition, etc. of the object to be treated in the airtight member performed with the O-ring or sealing member. The strength of pressing on the window member greatly affects the deflection of the window member. Therefore, in the differential pressure adjustment process, the gap can be made uniform by adjusting the pressure difference to a pressure difference corresponding to the strength of pressing.

According to the present invention, the gap can be made uniform to make the process uniform.
The objects, aspects and effects of the present invention described above as well as the objects, aspects and effects of the present invention not described above can be carried out by those skilled in the art by referring to the attached drawings and claims. It can be understood from the form (detailed description of the invention).

FIG. 1 is a schematic configuration view showing the light processing apparatus of the present embodiment. FIG. 2 is a view showing the structure of the ejector. FIG. 3 is a cross-sectional view showing the structure of the window member. FIG. 4 is a table showing experimental results confirming the contribution of differential pressure adjustment. FIG. 5 is a graph showing a change in the gap difference between the central portion and the peripheral portion of the window member with respect to the pressure difference between the processing unit and the light irradiation unit. FIG. 6 is a graph showing a change in the gap difference between the central portion and the peripheral portion of the window member with respect to the pressure difference between the processing unit and the light irradiation unit when the spacer is provided.

Hereinafter, embodiments of the present invention will be described based on the drawings.
FIG. 1 is a schematic configuration view showing the light processing apparatus of the present embodiment. In the present embodiment, as an example of the light processing apparatus, an application example to a desmear processing apparatus is shown.
(Configuration of light processing device)
The light processing apparatus 100 includes a light irradiation unit 10 and a processing unit 20 that holds a substrate (work) W, which is an example of an object to be processed. The light irradiation unit 10 accommodates, for example, a plurality of ultraviolet light sources 11 that emit vacuum ultraviolet light, and irradiates the substrate W held by the processing unit 20 with the light from the ultraviolet light source 11. The light irradiation unit 10 corresponds to an example of the light source unit according to the present invention, and the processing unit 20 corresponds to an example of the processing unit according to the present invention.

The light irradiation part 10 is provided with the box-shaped casing 14 which has an opening part below. At the opening of the casing 14, for example, a window member 12 such as quartz glass, which transmits vacuum ultraviolet light, for example, is airtightly provided. The window member 12 corresponds to an example of the window member in the present invention.
The interior of the light irradiator 10 (casing 14) is maintained in an inert gas atmosphere by supplying an inert gas such as nitrogen gas from the supply port 15, for example. A reflecting mirror 13 is provided above the ultraviolet light source 11 in the light irradiation unit 10. The reflecting mirror 13 reflects the light emitted from the ultraviolet light source 11 to the window member 12 side. With such a configuration, the light of the ultraviolet light source 11 is irradiated substantially uniformly to the region R substantially corresponding to the full width of the reflecting mirror 13. That is, the region R is a region to be irradiated with ultraviolet light in the region sandwiched between the window member 12 and the surface of the stage 21, and the ultraviolet treatment region to perform the ultraviolet irradiation processing (desmear processing) on the substrate W Become.

The ultraviolet light source 11 emits, for example, ultraviolet light (vacuum ultraviolet light) having a wavelength of 220 nm or less, preferably 190 nm or less, and various known lamps can be used. Here, the reason for setting the wavelength to 220 nm is that when the wavelength of ultraviolet light exceeds 220 nm, it becomes difficult to decompose and remove the smear caused by the organic substance such as resin.
As the ultraviolet light source 11, for example, a xenon excimer lamp (peak wavelength 172 nm), low pressure mercury lamp (185 nm bright line) or the like in which xenon gas is sealed can be used. Among them, for example, a xenon excimer lamp is preferable as the one used for the desmear treatment.

The processing unit 20 includes a stage 21 that adsorbs and holds the substrate W on which the ultraviolet irradiation process (desmear process) is performed on the surface. The stage 21 is disposed to face the window member 12 of the light emitting unit 10. For example, suction holes (not shown) are bored in the stage 21 in order to suction the substrate W. The stage 21 is formed of, for example, an aluminum material in order to ensure flatness.
An outer peripheral groove 21 a is formed on an outer peripheral portion of the surface of the stage 21. The O-ring 22 is sandwiched between the outer peripheral groove 21 a and the window member 12 of the light irradiation unit 10, whereby the light irradiation unit 10 and the processing unit 20 are assembled in an airtight manner. The O-ring 22 corresponds to an example of the airtight member in the present invention.
The stage 21 is supported by an actuator 51 that moves the stage 21 in a direction (upper and lower direction in the drawing) toward and away from the window member. As the stage 21 is moved by the actuator 51, the strength with which the O-ring 22 is pressed against the window member 12 is adjusted.

At a side edge of one side (right side in FIG. 1) of the stage 21, an air supply path 24 for supplying a processing gas (processing gas) to the processing region R is formed. A supply device 41 for supplying a processing gas is connected to the air supply passage 24.
Further, at the side edge of the other side (left side in FIG. 1) of the stage 21, an exhaust path 25 for discharging the exhaust gas after desmearing processing to the outside of the stage portion 21 is formed.
Here, as the processing gas, for example, a mixed gas of oxygen gas, oxygen and ozone or water vapor, or a mixture of these gases with an inert gas or the like is used. The processing gas is supplied to the processing region R through the air supply passage 24 while the substrate W is irradiated with the ultraviolet light from the light irradiation unit 10, and is discharged to the outside of the stage unit 21 as an exhaust gas through the exhaust passage 25. Discharged into That is, the processing gas flows in the processing region R between the window member 12 and the substrate W from the right to the left in FIG.

In the light processing apparatus 100 of the present embodiment, the ejector 42 is attached to the exhaust passage 25. The ejector 42 uses a fluid to create a reduced pressure state, and in the present embodiment, for example, the flow of compressed air generated by the compressor 45 is used. The ejector 42 is attached to the exhaust path 25 to forcibly discharge the processing gas in the processing unit 20. The pipe connecting the exhaust passage 25 and the ejector 42 is provided with a cock 46 which is opened and closed by motor drive to adjust the opening degree of the pipe. The light processing apparatus 100 also includes a control unit 52 that controls the opening degree of the cock 46 and the driving of the actuator 51.

Here, the structure of the ejector 42 will be described.
FIG. 2 is a view showing the structure of the ejector.
The ejector 42 has a suction port 421 connected to the exhaust path 25 described above, a primary side opening 422 to which compressed air is supplied from the compressor 45 described above, and a secondary side opening 423 from which gas is discharged. The compressed air supplied from the primary side opening 422 is blown out from the nozzle 424 to increase the flow velocity and flow into the diffuser 425. As the flow velocity increases in this manner, a reduced pressure state occurs between the nozzle 424 and the diffuser 425, and the exhaust gas is sucked from the suction port 421. The exhaust gas thus sucked is led to the secondary side opening 423 and flows out together with the flow of the compressed air.

FIG. 3 is a cross-sectional view showing the structure of the window member.
The window member 12 is provided with a spacer 121 in contact with the surface of the workpiece W. The height of the spacer 121 is, for example, about 100 μm to about 1 mm.
The window member 12 is a thin member in consideration of the transmittance of light to be irradiated, and for example, the thickness is 1/100 or less with respect to the length of one side. Therefore, the inventors have found that the window member 12 is bent due to the above-mentioned cause. Although the deflection in the direction approaching the workpiece W is suppressed by the spacer 121, the deflection in the direction away from the workpiece W can not be suppressed by the spacer 121. Then, as a result of intensive studies by the inventors in order to suppress such deflection of the window member 12 and equalize the gap between the workpiece W and the window member 12 over the entire surface of the workpiece W, the above-described differential pressure adjustment by the ejector Was found to be effective.

FIG. 4 is a table showing experimental results confirming the contribution of differential pressure adjustment.
In the table of FIG. 4, the uniformity of the gap is shown for each of the case where the differential pressure adjustment is not performed as in the prior art and the case where the differential pressure adjustment is performed using the ejector as in the present embodiment. . However, in the experiment in which the result is shown here, it is assumed that the window member 12 having no spacer 121 shown in FIG. 3 is used. For this reason, the window member 12 can also bend in the direction away from the work W as well as in the direction approaching it.
In the experiment shown in this table, when the flow rate of the processing gas is 4 l / min to 12 l / min, the uniformity of the gap was compared with the presence or absence of differential pressure adjustment. The workpiece W size is 340 mm × 510 mm, and the gap measurement point is 18 points. As the numerical value representing the uniformity of the gap, a value obtained by subtracting the narrowest gap value from the widest gap value (PP value) Was used.
As a result of the differential pressure adjustment, the pressure in the processing unit 20 was slightly reduced compared to the pressure in the light irradiation unit 10. Here, "slightly reduced pressure" means a pressure reduction of about 2 kPa at the maximum.
As can be seen from the table of FIG. 4, the PP value is reduced to about 1/10 when differential pressure adjustment is performed regardless of the flow rate of the processing gas. The small PP value means that the variation of the gap in the surface of the workpiece W is small and the uniformity of the gap is good.

Here, the change in the difference in the gap between the central portion and the peripheral portion of the window member with respect to the pressure difference between the processing unit 20 and the light irradiation unit 10 will be further described.
FIG. 5 is a graph showing the change in the difference in the gap between the central portion and the peripheral portion of the window member with respect to the pressure difference between the processing unit 20 and the light irradiation unit 10. Also in the experiment in which the result is shown here, the window member 12 without the spacer 121 shown in FIG. 3 is used.
The horizontal axis of the drawing represents the differential pressure obtained by subtracting the pressure on the light irradiation unit 10 side from the pressure on the processing unit 20 side, and the vertical axis represents the difference in gap between the central portion and the peripheral portion of the window member. However, +: the central portion is convex toward the light irradiation unit 10 side, and −: the central portion is convex toward the work W side.

A thick line 61 with a diamond mark indicates a change in the gap difference under the condition A in which the O-ring 22 is strongly pressed to the window member 12.
A thin line 62 with a square mark indicates a change in the difference of the gap under the condition B in which the O-ring 22 is normally pressed to the window member 12.
The dotted line 63 marked with a triangle indicates the change in the difference of the gap under the condition C in which the O-ring 22 is weakly pressed against the window member 12.
The strength of the pressing of the O-ring 22 against the window member 12 is changed by the vertical movement of the stage 21 by the actuator 51 shown in FIG. 1, but depending on various conditions such as the size, material, thickness and surface condition of the work W It is assumed that the above conditions A to C are selected.

In any of the above conditions A to C, when the differential pressure is zero, it can be seen that the window member 12 is bent in a convex state toward the light irradiation unit 10 side. And by making processing part 20 side into negative pressure to light irradiation part 10 side, a gap of a central part can be smaller than a peripheral part of window member 12, and it can be bent in a convex state on work W side. . However, the differential pressure when the gap is made uniform over the entire surface of the workpiece W differs depending on the conditions A to C described above. For example, in condition A, the gap is made uniform at a negative pressure of 1 kPa, for example, in condition B, the gap is made uniform at a negative pressure of 0.8 kPa, and in condition C, for example, the gap is made uniform at a negative pressure of 0.5 kPa. These pressure values are small compared to the atmospheric pressure, but the influence on small gaps, for example 1 mm or less, is sufficiently large.

Further, although the example shown in FIG. 5 is an example under the same conditions except that the O-ring 22 is pressed against the window member 12, the change in the gap difference with respect to the differential pressure is, for example, the difference in the flow rate of the processing gas Also show different changes.
Furthermore, in the example shown in FIG. 5, the gap is made uniform by setting the processing unit 20 side to a negative pressure with respect to the light irradiation unit 10 side, but for example, the case where the self weight deflection of the window member 12 is large or the O ring When the pressing force 22 is weak, when the flow rate of the processing gas is small, or when the discharge resistance (pressure loss) in the pipe on the exhaust side is small, etc., the processing unit 20 side is positive with respect to the light irradiation unit 10 side. The gap may be made uniform by pressure.

Even in such a case, the change tendency of the gap difference as shown in FIG. 5 is measured prior to the light processing, and the differential pressure at which the gap is made uniform is obtained as a value corresponding to various conditions. You can. An operation procedure in the light processing apparatus will be described below with reference to FIG. 1 on the premise that the differential pressure at which the gap is equalized is obtained in advance.
(1) The light irradiation unit 10 and the processing unit 20 are vertically separated. The window member 12 is attached to the light emitting unit 10 side.
(2) The work W is placed on the stage 21 and fixed by suction.
(3) The light emitting unit 10 is lowered or the processing unit 20 is raised. Thereby, the window member 12 contacts the O-ring 22 and the processing unit 20 is sealed. The control unit 52 controls the actuator 51 to move the stage 21 up and down to set the distance between the window member 12 and the work W to a predetermined distance of, for example, 1 mm or less.

(4) The supply device 41 operates to introduce the processing gas into the processing unit 20. Further, the ejector 42 also operates, and the gas is discharged from the processing unit 20. The process of (4) corresponds to an example of the gas supply and discharge process according to the present invention.
(5) The various conditions in the present light processing are input to the control unit 52, and a differential pressure corresponding to the conditions is obtained. Then, the control unit 52 adjusts the opening degree of the cock 46 to realize the differential pressure, and the gap between the window member 12 and the work W is maintained constant. In the case of this embodiment, since a spacer is provided between the window member 12 and the work W, strict control of the differential pressure is not required. If the opening degree of the cock 46 is slightly deviated to a larger side than the opening degree for achieving the required differential pressure, the gap is kept constant by the spacer.

The change of the difference of the gap in the central part and the peripheral part of the window member to the differential pressure of processing part 20 and light irradiation part 10 in the process of (5) is explained.
FIG. 6 is a graph showing the change in the difference in gap between the central portion and the peripheral portion of the window member with respect to the pressure difference between the processing unit 20 and the light irradiation unit 10 when the spacer 121 is provided on the window member 12.
The horizontal axis of the drawing represents the differential pressure obtained by subtracting the pressure on the light irradiation unit 10 side from the pressure on the processing unit 20 side, and the vertical axis represents the difference in gap between the central portion and the peripheral portion of the window member.
A thick line 64 with a diamond mark indicates a change in the difference of the gap under the condition A in which the O-ring 22 is strongly pressed to the window member 12.
A thin line 65 with a square mark indicates a change in the difference of the gap under the condition B in which the O-ring 22 is normally pressed to the window member 12.
The dotted line 66 marked with a triangle indicates the change in the difference of the gap under the condition C where the O-ring 22 is weakly pressed against the window member 12.

Under the condition A indicated by the thick line 64, the gap difference is maintained at 0 at a negative pressure of 1.0 kPa or more. Further, under the condition B indicated by the thin line 65, the gap difference is maintained at 0 at a negative pressure of 0.8 kPa or more. Furthermore, under the condition C indicated by the dotted line 66, the gap difference is maintained at 0 at a negative pressure of 0.5 kPa or more.
As described above, by providing the spacer, the gap is always kept constant under any of the conditions A to C as long as the differential pressure is a certain value or more. Therefore, in the process (5), if the differential pressure is set to a relatively large value, even if the pressure in the processing chamber fluctuates somewhat due to the influence of the flow of the processing gas, etc., The gap can be kept constant.

The process of (5) above corresponds to an example of the differential pressure adjustment process according to the present invention, and the control unit 52 shown in FIG. 1 corresponds to an example of the differential pressure adjustment section according to the present invention. Hereinafter, the operation procedure of the light processing apparatus will be described.
(6) The ultraviolet light source 11 is turned on to start light processing.
(7) When the light processing is completed, the ultraviolet light source 11 is turned off.
(8) The introduction of the processing gas into the processing unit 20 is stopped, and the operation of the ejector is also stopped.
(9) The light emitting unit 10 rises or the processing unit 20 descends, and the light emitting unit 10 and the processing unit 20 are vertically separated.
(10) Take out the work W.
A uniform ultraviolet irradiation process (desmear process) can be performed on the entire surface of the workpiece W by the above-described procedure.

In addition, although the example which has a spacer was shown as a suitable example in the said embodiment, the light processing apparatus of this invention may not have a spacer.
Further, although the application example to the desmear processing apparatus is shown in the above embodiment, the present invention may be applied to the light ashing processing of the resist, the resist removing processing, the dry cleaning processing and the like.
Further, in the above embodiment, as an example of the differential pressure adjustment unit according to the present invention, one for adjusting the exhaust amount from the processing unit 20 is shown, but the differential pressure adjustment unit according to the present invention The amount of air may be adjusted, or the pressure on the light source unit side may be adjusted.

Although specific embodiments are described above, the embodiments are merely examples and are not intended to limit the scope of the present invention. The devices and methods described herein may be embodied in forms other than those described above. In addition, omissions, substitutions and changes can be made as appropriate to the above-described embodiments without departing from the scope of the present invention. Such omissions, substitutions and changes are included in the scope of the claims and their equivalents, and belong to the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 100 ... Light processing apparatus, W ... Work, 10 ... Light irradiation part, 12 ... Window member, 20 ... Processing part, 22 ... O ring, 24 ... Air supply path, 25 ... Exhaust path, 41 ... Supply apparatus, 42 ... Ejector , 45: compressor, 46: cock, 51: actuator, 52: control unit

Claims (5)

A light source unit that emits light;
A processing unit in which the surface of the object to be processed is exposed in the atmosphere of the processing gas to the light emitted from the light source unit;
A window member which separates the light source unit from the processing unit and transmits light emitted from the light source unit;
A gas supply / discharge unit for flowing the processing gas along the surface, between the surface of the object to be processed and the window member;
A differential pressure adjusting unit configured to adjust a pressure difference between both sides separated by the window member in a state where the processing gas is flowing;
A light processing apparatus comprising: 2. The light processing apparatus according to claim 1, wherein the differential pressure adjustment unit adjusts an exhaust amount of the gas supply / exhaust unit exhausting the processing gas from the processing unit. A spacer which is interposed between the window member and the surface of the object to be treated and which keeps the distance between the window member and the surface;
The differential pressure adjusting unit adjusts a pressure difference such that the pressure on the object side is lower than the pressure on the light source unit side among the two sides separated by the window member. The light processing device according to claim 1 or 2. A gas supply and discharge process for flowing a processing gas along the surface between the surface of the object to be treated exposed to light and being processed and the window member transmitting the light;
A differential pressure adjustment process of adjusting a pressure difference between both sides separated by the window member in a state where the process gas is flowing;
And adjusting the distance between the surface of the object to be treated and the window member. And a pressing process for pressing an airtight member that is more elastic than the window member against the peripheral portion of the window member to prevent the processing gas from leaking.
The differential pressure adjustment process is a process of adjusting a pressure difference between both sides separated by the window member to a pressure difference according to the pressure strength of the airtight member in the pressing process. How to adjust the interval.

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