Plasma vacuum hot pressing bonding machine for semiconductor wafer surface bonding processing and bonding method
Technical Field
The invention relates to the technical field of chip equipment and semiconductor manufacturing, and provides a plasma vacuum in-situ bonding machine for semiconductor wafer surface bonding processing and a bonding method thereof.
Background
Bonding is an indispensable important link in the semiconductor manufacturing process, wafer bonding has wide application in the fields of integrated circuit manufacturing, micro electro mechanical system packaging, multifunctional chip integration and the like, but due to different requirements of different application fields on material bonding performance, the functions of bonding equipment have larger difference, so that a bonding system needs to be designed more reasonably and strictly according to the material preparation requirements.
Wafer bonding can be directly carried out in air, but by-product precursors such as hydroxyl, water vapor and the like in the air can be adsorbed on the surface of a wafer in an atmospheric environment, so that a large number of bubbles and oxide layers appear on a bonding interface after bonding, the bonding quality of the wafer is greatly influenced, and the wafer bonding is not allowed for a photoelectric device with an interface electric channel.
Disclosure of Invention
In view of the above-mentioned shortcomings of the prior art, the present invention is directed to a plasma vacuum thermocompression bonding machine for semiconductor wafer surface bonding processing and a bonding method thereof, which can avoid the generation of bubbles and oxide layer at the bonding interface and improve the bonding quality.
The invention relates to a plasma vacuum hot-pressing bonding machine for bonding processing of the surface of a semiconductor wafer, which is characterized by comprising a machine body, a vacuum cavity arranged on the machine body and a vacuumizing device for vacuumizing the vacuum cavity, wherein an upper sample table and a lower sample table for respectively placing the semiconductor wafer to be bonded and processed are arranged in the vacuum cavity, and the upper sample table and the lower sample table are oppositely arranged and can move relatively to joint the two semiconductor wafers positioned on the upper sample table and the lower sample table; a cathode discharge plate capable of horizontally moving to a position between the two semiconductor wafers is arranged in the vacuum cavity; heaters are arranged on the upper sample stage and the lower sample stage, and heat generated by the heaters is transferred to the semiconductor wafers positioned on the upper sample stage and the lower sample stage.
Furthermore, the upper sample stage and the lower sample stage are arranged oppositely in the vertical direction, and the upper sample stage is driven to descend by a vertically arranged screw and nut mechanism or an air cylinder driving mechanism, so that the semiconductor wafer on the upper sample stage and the semiconductor wafer on the lower sample stage can be attached.
Further, the polishing surface of the semiconductor wafer on the upper sample stage is downward, and the polishing surface of the semiconductor wafer on the lower sample stage is upward.
Furthermore, the electric wire of the heater is protected by insulating ceramics to avoid short circuit caused by the contact of the electric wire and high temperature.
Furthermore, the right side inside the vacuum cavity is a cathode discharge plate placing area, the cathode discharge plate placing area is externally connected with a radio frequency power supply to electrify the cathode plate, and the cathode discharge plate is driven to move horizontally by a horizontally arranged screw rod nut mechanism or an air cylinder driving mechanism.
Furthermore, the screw rod nut mechanism vertically arranged on the upper sample platform is connected with and controlled by the stepping motor, so that the screw rod can adjust the pressure of the upper sample platform and the lower sample platform in a stepping manner.
Furthermore, silicon wafers, germanium wafers or indium phosphide wafers are adhered to the surfaces of the upper sample stage, the lower sample stage and the cathode discharge plate, and are used for removing the influence of stainless steel of the sample stage and the cathode discharge plate on the surface of the semiconductor wafer during plasma treatment so as to realize high-quality bonding of different semiconductor wafers.
Furthermore, the vacuum chamber is also connected with an air inlet channel for introducing nitrogen and argon.
The bonding method is characterized by comprising the following steps:
s1, opening the vacuum cavity, respectively placing two semiconductor wafers to be bonded on the upper sample stage and the lower sample stage, and aligning and positioning;
s2, opening a vacuumizing device to finish high-vacuum extraction of the vacuum cavity;
s3, when the vacuum degree reaches a target value, argon begins to be input, after the air inlet pressure control is stable, the cathode discharge plate is driven to move to the middle area of the vacuum cavity between the upper sample stage and the lower sample stage, the radio frequency power supply is turned on to carry out plasma processing on the semiconductor wafer on the upper sample stage and the lower sample stage, and after the plasma processing, the radio frequency power supply is turned off to drive the cathode discharge plate to be pulled away from the bonding area;
s4, driving the upper sample stage to descend to enable the upper sample stage to be in bonding contact with the two semiconductor wafers on the lower sample stage and keep bonding pressure of the upper sample stage and the two semiconductor wafers;
s5, heating the two semiconductor wafers under pressure in situ;
and S6, annealing in situ after heating for a certain time, lifting the sample loading table after annealing is finished, removing the pressure applied to the two semiconductor wafers, opening the cavity, taking out the sample, and finishing in situ bonding.
Further, in the step S3, the target value of the vacuum degree is 10-4 Pa, the pressure control value of the vacuum chamber is 2.5 Pa, the pressure value between the two semiconductor wafers is 1000N-3000N), and the temperature of the two semiconductor wafers during in-situ heating is 300-.
The bonding method can bond the semiconductor wafer in a high vacuum environment, prevent an oxide layer from being introduced into a bonding interface, and avoid the problem that the bonding quality is influenced because bubbles are formed due to the adsorption of hydroxyl on the surface of the wafer.
Description of the drawings:
FIG. 1 is a schematic view of a partial three-dimensional structure of a plasma vacuum hot-pressing bonding machine;
FIG. 2 is a schematic view of a partial front cross-sectional structure of a plasma vacuum hot-pressing bonder;
FIG. 3 is a schematic view of the overall three-dimensional structure of the plasma vacuum hot-pressing bonding machine;
FIG. 4 is a flow chart of the bonding method of the present invention.
Detailed Description
The embodiments of the present invention provide a plasma vacuum in-situ bonding machine and a bonding method, and the present invention will be further described in detail with reference to the accompanying drawings and specific embodiments.
The invention relates to a plasma vacuum hot-pressing bonding machine for bonding processing of the surface of a semiconductor wafer, which comprises a machine body 1 and a vacuum cavity 2 arranged on the machine body 1, wherein the vacuum cavity 2 is a vertical cavity which is a full stainless steel copper ring sealing structure, the front surface of the vacuum cavity is a cavity sealing door which is provided with an observation window and provides a high vacuum environment for a bonding process, a circuit of each module is arranged in the machine body 1, and the front side of the machine body 1 is provided with a belt disc pressure gauge 10, a pressure adjusting knob 11 and the like.
The vacuum-pumping device 3 for vacuumizing the vacuum cavity is arranged on the machine body, and the vacuum-pumping device 3 is the existing equipment and comprises a molecular pump, a mechanical pump, a composite vacuum gauge, a gate valve, a butterfly valve, a resistance gauge, an ionization gauge, a film gauge and the like and is used for pumping gas in the vacuum cavity 2 to create a high-vacuum environment.
An upper sample table 4 and a lower sample table 5 which are used for respectively placing the semiconductor wafers to be bonded and processed are arranged in the vacuum cavity, and positioning grooves are formed in the upper sample table 4 and the lower sample table 5 and used for fixing the semiconductor wafers to be bonded and processed.
The upper sample table and the lower sample table are arranged oppositely in the vertical direction, wherein the upper sample table is driven to lift by a vertically arranged screw rod-nut mechanism or an air cylinder driving mechanism 8 and the like, so that a semiconductor wafer positioned on the upper sample table and a semiconductor wafer positioned on the lower sample table can be attached, wherein the polishing surface of the semiconductor wafer positioned on the upper sample table faces downwards, and the polishing surface of the semiconductor wafer positioned on the lower sample table faces upwards; preferably, the screw rod nut mechanism vertically arranged on the upper sample platform can be connected with and controlled by the stepping motor, so that the screw rod can adjust the pressure of the upper sample platform and the lower sample platform in a stepping manner.
A cathode discharge plate 6 capable of horizontally moving to a position between the two semiconductor wafers is arranged in the vacuum cavity, wherein the right side in the vacuum cavity is a cathode discharge plate placing area, the cathode discharge plate 6 is located in the cathode discharge plate placing area in an initial state, when the vacuum cavity works, the cathode discharge plate 6 moves to a position between the two semiconductor wafers, and the cathode discharge plate 6 can be driven to horizontally move by a horizontally arranged screw rod nut mechanism or an air cylinder driving mechanism 9 and the like; the cathode discharge plate placing area is externally connected with a radio frequency power supply, so that the cathode plate can be electrified to generate plasma, the generated plasma can bombard and remove an oxide layer on the bonding surface of the semiconductor wafer, and a dangling bond is introduced to the bonding surface.
When the plasma processing step is finished, the cathode discharge plate is controlled to move rightwards and reset, and the cathode discharge plate is moved to the right side of the cavity, so that in-situ hot-pressing bonding can be carried out in the middle of the cavity.
The heaters 7 are arranged on the upper sample stage and the lower sample stage, heat generated by the heaters is transferred to the positioned semiconductor wafers on the upper sample stage and the lower sample stage, the heaters 7 can be electric heating wires and the like embedded in the upper sample stage and the lower sample stage, and the semiconductor wafers after plasma treatment are subjected to hot-press bonding under high vacuum, so that an oxide layer and bubbles at a bonding interface are effectively prevented from being introduced, and the bonding quality is improved.
The electric wire of the heater is protected by insulating ceramic in order to protect the electric wire, thereby preventing the electric wire from short circuit caused by contact with high temperature.
In order to design reasonably, silicon wafers, germanium wafers or indium phosphide wafers (i.e. semiconductor materials which are the same as the semiconductor wafers to be bonded) are adhered to the surfaces of the upper sample stage, the lower sample stage and the cathode discharge plate and are used for removing the influence of stainless steel of the sample stage and the cathode discharge plate on the surfaces of the semiconductor wafers during plasma treatment so as to realize high-quality bonding of different semiconductor wafers.
Further, the vacuum cavity is also connected with an air inlet channel for introducing nitrogen and argon; the outside of the actual vacuum cavity is provided with a vacuum air exhaust interface, a discharge gas inlet interface (namely an air inlet channel), a common nitrogen air exhaust interface, a resistance gauge interface, an ionization gauge interface and a film gauge interface, wherein the interfaces are used for meeting the requirements of vacuum pumping, nitrogen introduction and the guarantee of stable air pressure.
The bonding method is characterized by comprising the following steps:
s1, opening the vacuum cavity, respectively placing two semiconductor wafers to be bonded on the upper sample stage and the lower sample stage, and aligning and positioning;
s2, opening a vacuumizing device to finish high-vacuum extraction of the vacuum cavity;
s3, when the vacuum degree reaches a target value, argon begins to be input, after the air inlet pressure control is stable, the cathode discharge plate is driven to move to the middle area of the vacuum cavity between the upper sample stage and the lower sample stage, the radio frequency power supply is turned on to carry out plasma processing on the semiconductor wafer on the upper sample stage and the lower sample stage, and after the plasma processing, the radio frequency power supply is turned off to drive the cathode discharge plate to be pulled away from the bonding area;
s4, driving the upper sample stage to descend to enable the upper sample stage to be in bonding contact with the two semiconductor wafers on the lower sample stage and keep bonding pressure of the upper sample stage and the two semiconductor wafers;
s5, heating the two semiconductor wafers under pressure in situ;
and S6, annealing in situ after heating for a certain time, lifting the sample loading table after annealing is finished, removing the pressure applied to the two semiconductor wafers, opening the cavity, taking out the sample, and finishing in situ bonding.
Further, in step S3, the target vacuum degree is 10-4 Pa, the pressure control value of the vacuum chamber is 2.5 Pa (adjustable according to the requirement), the pressure value between the two semiconductor wafers is 1000N (adjustable according to the requirement, the maximum pressure is 3000N), and the temperature of the two semiconductor wafers during in-situ heating is 300 ℃ (adjustable according to the requirement, maximum 600 ℃).
The bonding method can bond the semiconductor wafer in a high vacuum environment, prevent an oxide layer from being introduced into a bonding interface, and avoid the problem that the bonding quality is influenced because bubbles are formed due to the adsorption of hydroxyl on the surface of the wafer.