Semiconductor material grinding and processing fixture with measurable and controllable pressure and processing method

Abstract

The invention discloses a semiconductor material grinding and processing fixture with measurable and controllable pressure, comprising a fixture outer bracket, a fixture sleeve, an adsorption head and a fixture inner shaft, wherein the fixture outer bracket is fixedly connected to the fixture sleeve, the adsorption head is fixedly connected to the lower end of the fixture inner shaft, the adsorption head is arranged in the fixture outer bracket, the fixture inner shaft is arranged in the fixture sleeve, the fixture sleeve is threaded with a pressure coarse adjustment knob, the pressure coarse adjustment knob is connected to an upper base plate, the upper base plate is longitudinally connected to a motor via a tension pressure sensor, the motor drives the fixture inner shaft to move longitudinally relative to the fixture sleeve, and when the pressure coarse adjustment knob is rotated, the upper base plate, the tension pressure sensor, the motor, the screw nut kinematic pair and the fixture inner shaft are driven to move longitudinally together, and the tension pressure sensor is used to measure the longitudinal tension pressure. The invention adjusts the pressure range through the pressure coarse adjustment knob, and the motor fine-tunes in real time to reach the set pressure, thereby realizing high-precision measurement and control of pressure during grinding.

Description

Technical Field

[0001] The invention relates to a semiconductor material processing fixture, in particular to a semiconductor material grinding processing fixture with measurable and controllable pressure. Background Art

[0002] During the processing of semiconductor wafers or materials, the wafers or materials need to be ground and polished. During the grinding process, the fixture clamps the wafer or material on the grinder for precision processing. During the processing, the fixture needs to apply a certain amount of pressure on the wafer or material to ensure that the wafer or material is processed correctly.

[0003] When grinding semiconductor materials, especially antimonides and III-V materials represented by GaSb, InSb, InAs, etc., it is necessary to control the back pressure of the wafer or material to prevent excessive pressure from causing material breakage, edge collapse and scratches. When grinding the back of some small wafers and devices, the pressure required is between 100 and 800 grams, and the pressure control requires more precision and accuracy.

[0004] The current precision grinding fixtures are pressurized mechanically, such as directly adding a load block of a certain weight, adjusting the downward pressure through a mechanical knob and spring force, or using a cylinder to set the pressure. These pressurization methods are relatively rough and are suitable for high pressure. Due to the inaccuracy of spring and cylinder control, the error exceeds 10% within a small pressure range below 1000g and the repeatability is poor. These are not conducive to the precise control of pressure and are not suitable for high-standard semiconductor material processing. Summary of the invention

[0005] In view of the above-mentioned defects of the prior art, the task of the present invention is to provide a semiconductor material grinding processing fixture with measurable and controllable pressure, the purpose of which is to improve the pressure accuracy in the pressure range below 1 kg, and also to improve the repetitive consistency of the grinding removal amount and the surface consistency of the material after processing. Another task of the present invention is to provide a processing method using the semiconductor material grinding processing fixture of the present invention.

[0006] The technical solution of the present invention is as follows: A semiconductor material grinding processing fixture with measurable and controllable pressure, comprising a fixture outer bracket, a fixture sleeve, an adsorption head and a fixture inner shaft, the fixture outer bracket is fixedly connected to the fixture sleeve, the adsorption head is fixedly connected to the lower end of the fixture inner shaft, the adsorption head is arranged in the fixture outer bracket, the fixture inner shaft is arranged in the fixture sleeve, the fixture sleeve is threaded with a pressure coarse adjustment knob, the pressure coarse adjustment knob is connected to an upper base plate, the lower part of the upper base plate is longitudinally connected to a motor through a tension pressure sensor, the motor drives the fixture inner shaft to move longitudinally relative to the fixture sleeve, and when the pressure coarse adjustment knob is rotated, the upper base plate, the tension pressure sensor, the motor, the screw nut kinematic pair and the fixture inner shaft are driven to move longitudinally together, and the tension pressure sensor is used to measure the longitudinal tension pressure.

[0007] Furthermore, a distance measuring device is provided on the top surface of the outer bracket of the clamp, and the distance measuring device is used to measure the longitudinal movement distance of the adsorption head.

[0008] Furthermore, a controller is included, and the controller is electrically connected to the tension and pressure sensor, the motor and the distance measuring device respectively. The controller controls the operation of the motor according to the signals of the tension and pressure sensor and the distance measuring device, and the motor is controlled by the change of tension and the moving distance of the adsorption head respectively, so that better repeatability can be achieved.

[0009] Furthermore, in order to improve the accuracy of the longitudinal movement of the inner shaft of the clamp and avoid rotation of the inner shaft of the clamp during coarse adjustment, the upper base plate is fixedly connected with a support tube, and the support tube is connected to the coarse pressure adjustment knob through a bearing. The upper base plate is rotatably connected with the coarse pressure adjustment knob through the support tube, and the clamp sleeve and the inner shaft of the clamp are longitudinally slidably matched.

[0010] Furthermore, the motor is arranged in the support tube, and the upper end of the inner shaft of the clamp extends into the support tube.

[0011] Furthermore, the motor is connected to the upper end of the inner shaft of the fixture through a screw-nut kinematic pair.

[0012] Furthermore, a rotary joint for introducing vacuum is provided on the upper base plate, and a vacuum outlet joint is provided on the upper base plate.

[0013] Furthermore, the adsorption head is provided with a vacuum chamber, the vacuum chamber is provided with a vacuum interface, and the vacuum interface extends from the outer bracket of the fixture.

[0014] Furthermore, the distance measuring device is a wireless micrometer.

[0015] Another technical solution of the present invention is: a pressure-measurable, controllable and adjustable semiconductor material grinding processing method, using the aforementioned pressure-measurable, controllable and adjustable semiconductor material grinding processing fixture, including adsorbing a wafer on the lower end surface of the adsorption head and placing the semiconductor material grinding processing fixture on a grinding and polishing disk, first adjusting the pressure coarse adjustment knob so that the pressure Fw exerted on the wafer deviates from the required processing pressure by no more than 100g, and then controlling the motor action by the controller so that Fw reaches the required processing pressure, wherein Fw=W-F2, wherein W is the overall weight of the motor, the fixture sleeve, the adsorption head and the wafer connected in sequence, and the F2 is the tension measured by the tension sensor. During the grinding and polishing process, the motor action is controlled according to the tension change measured by the tension sensor and the longitudinal movement distance of the adsorption head measured by the distance measuring device so that the Fw is stabilized at the required processing pressure. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a three-dimensional schematic diagram of a semiconductor material grinding processing fixture with measurable and controllable pressure according to an embodiment.

[0017] Figure 2 It is a schematic cross-sectional structure diagram of a semiconductor material grinding processing fixture with measurable and controllable pressure according to an embodiment.

[0018] Figure 3 Schematic diagram of the external electrical connection structure of the semiconductor material grinding processing fixture with measurable and controllable pressure according to the embodiment.

[0019] Figure 4 It is a schematic diagram of the pipeline connection structure of the semiconductor material grinding processing fixture with measurable and controllable pressure according to an embodiment.

[0020] Figure 5 This is the force diagram of the wafer in the unpressurized hovering state.

[0021] Figure 6 This is the force diagram when the wafer is under pressure. DETAILED DESCRIPTION

[0022] The present invention will be further described below in conjunction with the embodiments, but are not intended to limit the present invention.

[0023] Please combine Figures 1 to 4 As shown, the semiconductor material grinding processing fixture 100 with measurable and controllable pressure involved in this embodiment includes a rotary joint 1, an upper substrate 2, a tensile pressure sensor 3, a motor 4, a support cylinder 5, a screw sleeve 6, a bearing 7, a pressure coarse adjustment knob 8, a fixture inner shaft 9, a fixture sleeve 10, a vacuum interface 11, a vacuum chamber 12, an adsorption head 13, a drive ring 15, a fixture outer bracket 16, and a wireless micrometer 17.

[0024] The lower end of the rotary joint 1 is fixedly connected to the upper substrate 2, and a vacuum outlet joint 2a is provided on the side of the upper substrate 2. Vacuum is introduced into the top of the rotary joint 1 and is led out from the vacuum outlet joint 2a of the upper substrate 2. Terminals 1a are provided on the sides of the rotary joint 1 to realize the electrical connection between the pull pressure sensor 3, the motor 4 and the external controller 18 in the semiconductor material grinding and processing fixture.

[0025] The upper substrate 2 is fixed on the top of the supporting cylinder 5. The supporting cylinder 5 is hollow inside, and a tension and pressure sensor 3 is fixedly installed on the bottom of the upper substrate 2. The tension and pressure sensor 3 is connected to a motor 4, and the tension and pressure sensor 3 measures the longitudinal tension and pressure.

[0026] The bottom outer edge of the support cylinder 5 is fixed to the outer plate of the bearing 7, the axis of the bearing 7 is longitudinally arranged, and the inner plate of the bearing 7 is fixedly connected to the top of the pressure coarse adjustment knob 8, so that when the pressure coarse adjustment knob 8 is turned, the support cylinder 5 can be guaranteed not to rotate under the action of the bearing 7.

[0027] The coarse pressure adjustment knob 8 is processed with precision threads inside, and is matched with the clamp sleeve 10. The upper end of the clamp sleeve 10 is also processed with precision threads. The coarse pressure adjustment knob 8 and the clamp sleeve 10 are threadedly connected. When the coarse pressure adjustment knob 8 is rotated, the coarse pressure adjustment knob 8 and the clamp sleeve 10 can produce axial displacement (longitudinal displacement).

[0028] The clamp sleeve 10 is fixedly connected to the clamp outer bracket 16 , a driving ring 15 is fixedly arranged on the bottom surface of the clamp outer bracket 16 , and the inner cavity of the clamp outer bracket 16 is used to accommodate the adsorption head 13 to adsorb the wafer 14 .

[0029] The rotating shaft of the motor 4 is arranged downwards, and a lead screw is connected to the rotating shaft of the motor 4. A lead screw sleeve 6 cooperates with the lead screw to form a lead screw nut kinematic pair. The rotation of the motor 4 drives the lead screw sleeve 6 to perform longitudinal displacement.

[0030] The lower sleeve of the screw sleeve 6 is fixed to the top of the inner shaft 9 of the clamp. The inner shaft 9 of the clamp is vertically arranged and located in the clamp sleeve 10. The inner shaft 9 of the clamp is longitudinally slidably matched with the clamp sleeve 10, and the inner shaft 9 of the clamp is displaced and guided by the clamp sleeve 10. The inner shaft 9 of the clamp is fixedly connected to the adsorption head 13. In this way, under the drive of the motor 4, the adsorption head 13 can be driven to perform precise longitudinal displacement through the screw sleeve 6 and the inner shaft 9 of the clamp to adjust the pressure on the adsorption wafer on the adsorption head 13.

[0031] A vacuum chamber is arranged inside the adsorption head 13, and grooves and through holes are arranged on the bottom surface of the adsorption head 13 to communicate with the vacuum chamber 12. A vacuum interface 11 is also arranged on the top of the adsorption head 13, and the vacuum interface 11 is connected to the vacuum chamber. The top of the vacuum interface 11 passes through the top plate of the fixture outer bracket 16 and is connected to the vacuum outlet connector 2a of the upper substrate 2 through a hose. Through this passage, the vacuum chamber is vacuumed, so that the grooves and through holes at the bottom of the adsorption head 13 are used to adsorb the wafer 14.

[0032] A wireless micrometer 17 serving as a distance measuring device is also fixedly mounted on the top plate of the fixture outer bracket 16 . The pin of the wireless micrometer 17 is arranged in the concave cavity of the fixture outer bracket 16 and contacts the upper surface of the adsorption head 13 , so as to measure the moving distance of the adsorption head 13 .

[0033] like Figure 3 As shown, a vacuum pump 19 is connected to a vacuum filter 20 and then connected to a rotary joint 1 through a vacuum pipeline to provide vacuum for the semiconductor material grinding fixture 100. A solenoid valve 21 is arranged on the vacuum pipeline, and the solenoid valve 21 is electrically connected to an external controller 18. The external controller 18 is also electrically connected to a motor controller 22, a sensor controller 23 and a signal receiver 24. The motor controller 22 is used to connect to the motor 4 and control the motor to work. The sensor controller 23 is used to connect to the pull pressure sensor 3 to pierce the pull pressure signal. The signal receiver 24 is connected to the wireless micrometer 17 to receive the distance signal measured by it.

[0034] Please combine Figure 5 , Figure 6 As shown, the method for grinding semiconductor materials with measurable and controllable pressure using the semiconductor material grinding fixture 100 is as follows:

[0035] The wafer 14 is adsorbed to the lower end surface of the adsorption head 13 and the semiconductor material grinding and processing fixture 100 is placed on the grinding and polishing disc 200. When the wafer 14 is not in contact with the surface of the grinding and polishing disc 200, the processed surface of the wafer 14 is not subjected to pressure. The screw sleeve 6, the inner shaft 9 of the fixture, the adsorption head 13, and the wafer 14 connected in sequence are regarded as a whole, and their weight is W1. At this time, they are subjected to the upward pulling force F1 of the motor 4, W1=F1. The weight of the motor 4 is W2. When the motor 4 and the aforementioned whole are regarded as a large whole, their total weight is W=W1+W2. At this time, the large whole is subjected to its own downward gravity W, and the pulling pressure sensor 3 exerts an upward pulling force F2 on it. W=F2. Among them, F2 can be measured by the pulling pressure sensor 3, and W1 and W2 can be weighed. In the figure, F1 is the pulling force received by the motor 4.

[0036] When the wafer 14 contacts the surface of the polishing disc 200, pressure is generated. This pressure can also be understood as the force exerted by the surface of the polishing disc on the wafer 14, which is Fw. At this time, the pull pressure sensor 3 exerts an upward pull force F2 on the whole. W= F2+Fw. Therefore, the pressure on the wafer is Fw=W-F2.

[0037] When setting the processing pressure of the wafer 14, first adjust the pressure coarse adjustment knob 8 so that the pressure Fw on the wafer 14 deviates from the required processing pressure by no more than 100g, and then the external controller 18 controls the motor 4 to adjust the height of the adsorption head 13 so that Fw reaches the required processing pressure, where Fw=W-F2.

[0038] During the grinding and polishing process, the external controller 18 controls the motor 4 to stabilize Fw at the required processing pressure according to the change in tension measured by the tension pressure sensor 3 and the longitudinal movement distance of the adsorption head 13 measured by the wireless micrometer 17. Specifically, the surface material of the wafer 14 is removed, which increases the gap between the surface of the wafer 14 and the surface of the grinding and polishing disc 200, resulting in a decrease in the force Fw on the wafer 14. In order to maintain the stability of Fw, the motor 4 needs to act to move the adsorption head 13 and the wafer 14 downward as a whole to compensate for the height of the material removed from the surface of the wafer 14. This process is repeated throughout the grinding process until the required thickness of the wafer 14 is reached and then stopped. The external controller 18 calculates the stroke length of the motor 4 during the grinding process in real time, and further calculates the thickness of the material removed from the surface of the wafer 14. At the same time, the wireless micrometer 17 also monitors and records the thickness of the material removed from the surface of the wafer 14 in real time. These two detection methods are carried out simultaneously, and the accuracy and repeatability of the thickness of the material removed from the surface of the wafer 14 can be improved through systematic comparison and correction.

[0039] It should also be pointed out that during the grinding process, the surface material of the wafer 14 is removed, which reduces the overall weight W1. At the same time, after the material is removed, Fw will also change. Taking 2-inch InSb as an example, when the thickness of 400 microns is removed during the entire grinding process, its weight changes by about 5g. The pressure on the 2-inch wafer is 800g (40g / cm2), and the grinding removal rate is 10 microns per minute and the grinding removal is about 400 microns. The change in W1 caused by material removal per minute is 0.13g. For smaller chips, such as 20mm*20mm chips, the change in W1 caused by the change in total thickness of 300 microns is only about 0.7 grams, which is very small for the pressure of 160g (40g / cm2) and the amount of material removed. Therefore, in the grinding process using this fixture, the impact of material removal on W1 and the amount of material removed can be ignored.

[0040] In Example 1, the overall weight of the design is W1=2560g, the weight of the motor 4 is W2=300g, a 2-inch InSb test piece is used, the preset pressure Fw=800g, and the force that the tensile pressure sensor 3 should measure is calculated to be F2=2060g.

[0041] Before grinding, place the fixture as a whole on the pressure test calibration device, adjust the pressure coarse adjustment knob 8 so that the reading of the tension pressure sensor 3 is about 1960g, and then lock the pressure coarse adjustment knob 8. Then control the motor 4 to move W1 upward a small distance as a whole so that the reading of the tension pressure sensor 3 is 2060g.

[0042] Ensure that the grinding and polishing disc 200 is flat and the abrasive A is evenly distributed on the surface, and place the clamp with adjusted pressure on the grinding and polishing disc 200. Run the grinding process A for grinding, and clear the wireless micrometer at the same time. The external controller 18 records the starting position X1 of the motor 4 and detects the reading of the tension pressure sensor 3 in real time. When it is less than 2060g, the motor 4 is controlled to adjust the overall upward movement so that the pressure is always maintained at 2060g; when it is greater than 2060g, the motor 4 is controlled to adjust the overall downward movement so that the pressure is always maintained at 2060g. Record the pressure changes in real time and form a pressure curve. Until the value of the wireless micrometer 17 reaches the removal thickness of 300um, record the end position X2 of the motor 4 at this time, and compare the difference between X2-X1 and the value reached by the wireless micrometer 17. The total time was recorded, and the material removal rate was calculated to be 9.6um / min. The difference between X2-X1 and the wireless micrometer 17 was + / -2um, and the thickness error was + / -0.67%. The TTV thickness change on the surface of the 2-inch test piece was 1 micron, and there was no chipping or damage on the edge of the wafer, and no obvious scratches on the surface. The real-time pressure change range was 6g, and the error of the test piece pressure was + / -0.4%.

[0043] Example 2, the overall weight of the design is W1=2560g, the weight of the motor 4 is W2=300g, a 20mm*20mm InSb test piece is used, the preset pressure Fw=160g, and the force that the tensile pressure sensor 3 should measure is calculated to be F2=2700g.

[0044] Before grinding, place the fixture as a whole on the pressure test calibration device, adjust the pressure coarse adjustment knob 8 so that the reading of the tension pressure sensor 3 is about 2600g, and then lock the pressure coarse adjustment knob 8. Then control the motor 4 to move W1 upward a small distance as a whole so that the reading of the tension pressure sensor 3 is 2700g.

[0045] Ensure that the grinding and polishing disc 200 is flat and the abrasive B is evenly distributed on the surface, and place the fixture with adjusted pressure on the grinding and polishing disc 200. At the same time, clear the wireless micrometer 17 and record the starting position X3 of the motor 4. Detect the reading of the tension pressure sensor 3 in real time. When it is less than 2700g, control the motor 4 to adjust the overall upward movement so that the pressure is always maintained at 2700g; when it is greater than 2700g, control the motor 4 to adjust the overall downward movement so that the pressure is always maintained at 2700g. Record the pressure change in real time and form a pressure curve. Until the value of the wireless micrometer 17 reaches the removal thickness of 300um, record the end position X4 of the motor 4, and record the total time. The material removal rate is calculated to be 8.9um / min. Compare the values ​​of X4-X3 and the wireless micrometer 17. The difference range is + / -3um, the thickness error is + / -1%, and the measured surface TTV change is 1 micron. There is no edge collapse and no damage on the wafer edge, and there is no obvious scratch on the surface. The real-time pressure variation range is 8g, and the chip pressure error is + / -2.5%.

Claims

1. A semiconductor material grinding fixture with measurable and controllable pressure, characterized in that: The invention comprises a fixture outer bracket, a fixture sleeve, an adsorption head, a fixture inner shaft and a controller, wherein the fixture outer bracket is fixedly connected to the fixture sleeve, the adsorption head is fixedly connected to the lower end of the fixture inner shaft, the adsorption head is arranged in the fixture outer bracket, the fixture inner shaft is arranged in the fixture sleeve, the fixture sleeve is threadedly fitted with a pressure coarse adjustment knob, the pressure coarse adjustment knob is connected to an upper base plate, a motor is longitudinally connected to the lower side of the upper base plate through a tension pressure sensor, the motor is connected to the upper end of the fixture inner shaft through a screw nut kinematic pair, the motor drives the fixture inner shaft to move longitudinally relative to the fixture sleeve, and when the pressure coarse adjustment knob is rotated, the upper base plate, the tension pressure sensor, the motor, the screw nut kinematic pair and the fixture inner shaft are driven to move longitudinally together, the tension pressure sensor is used to measure the longitudinal tension pressure, a distance measuring device is provided on the top surface of the fixture outer bracket, the distance measuring device is used to measure the longitudinal movement distance of the adsorption head, and the controller is electrically connected to the tension pressure sensor, the motor and the distance measuring device respectively; When grinding semiconductor materials, the wafer is adsorbed on the lower end surface of the adsorption head and the semiconductor material grinding fixture is placed on the grinding and polishing plate. The coarse pressure adjustment knob is first adjusted so that the pressure Fw on the wafer deviates from the required processing pressure by no more than 100g. The controller then controls the motor to make Fw reach the required processing pressure, wherein Fw=W-F2, wherein W is the overall weight of the motor, the fixture sleeve, the adsorption head and the wafer connected in sequence, and F2 is the tension measured by the tension sensor. During the grinding and polishing process, the motor is controlled according to the tension change measured by the tension sensor and the longitudinal movement distance of the adsorption head measured by the distance measuring device to stabilize Fw at the required processing pressure.

2. The semiconductor material grinding and processing fixture with measurable and controllable pressure according to claim 1 is characterized in that: The upper base plate is fixedly connected with a support tube, and the support tube is connected to the pressure coarse adjustment knob through a bearing. The upper base plate is rotatably connected to the pressure coarse adjustment knob through the support tube, and the clamp sleeve is slidably matched with the inner shaft of the clamp in the longitudinal direction.

3. The semiconductor material grinding and processing fixture with measurable and controllable pressure according to claim 2 is characterized in that: The motor is arranged in the support tube, and the upper end of the inner shaft of the clamp extends into the support tube.

4. The semiconductor material grinding and processing fixture with measurable and controllable pressure according to claim 1 is characterized in that: The upper base plate is provided with a rotary joint for introducing vacuum, and the upper base plate is provided with a vacuum outlet joint.

5. The semiconductor material grinding and processing fixture with measurable and controllable pressure according to claim 1 is characterized in that: The adsorption head is provided with a vacuum chamber, the vacuum chamber is provided with a vacuum interface, and the vacuum interface extends from the outer bracket of the fixture.

6. The semiconductor material grinding and processing fixture with measurable and controllable pressure according to claim 1, characterized in that: The distance measuring device is a wireless micrometer.

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