Device and method for on-line measurement of wafer grinding force
A method and apparatus for on-line measurement of the wafer thinning and grinding force, related to the field of ultra-precision machining of semiconductor wafer materials. The grinding force measuring apparatus comprises a semiconductor wafer, a worktable, a bearing table, a thin film pressure sensor, and a data processing and wireless transmission module. The grinding force measuring method includes sensor calibration based on the testing device and on-line measurement of grinding force. Using the grinding force measuring device and method provided by the invention, the grinding force in the semiconductor wafer grinding process can be monitored in real time, which is of great significance for semiconductor processing and reducing grinding damage. The invention also has the following characteristics: the sensor adopts a film pressure sensor, the response time is short, and the test precision is high; the data transmission adopts a wireless transmission design, thus the grinding force can be monitored in real time during the wafer and spindle rotation process and the risk of winding during wafer rotation can be avoided. The sensor adopts a distributed design, which can monitor the distribution of the grinding force along the wafer radial direction or crystal orientation.
1. A wafer grinding force on-line measuring device, comprising:
a semiconductor wafer ( 1 ),
a bonding adhesive ( 2 ),
a thin film pressure sensor ( 3 ), a worktable ( 4 ),
a bearing table ( 5 ),
a wafer spindle base ( 6 ),
a data acquisition and wireless transmission module, and
a wireless receiving module;
wherein the semiconductor wafer ( 1 ) is connected to a work surface ( 404 ) of the worktable ( 4 ) through the bonding adhesive ( 2 ), wherein the thickness of the bonding adhesive ( 2 ) is less than 300 μm; wherein a bottom surface of the thin film pressure sensor ( 3 ) is in the same plane with a bottom surface of the bonding adhesive ( 2 ), and the thickness of the thin film pressure sensor ( 3 ) is 3-10 μm greater than that of the bonding adhesive ( 2 ); wherein a threading hole ( 403 ) is disposed in the worktable ( 4 ), the threading hole ( 403 ) is cuboid-shaped, and runs through the worktable ( 4 ); wherein the thin film pressure sensor ( 3 ) is connected to the data acquisition and wireless transmission module through a conducting wire that runs through the threading hole ( 403 ); wherein the data acquisition and wireless transmission module is located in a cavity ( 503 ) of the bearing table ( 5 ) and affixed to the bearing table ( 5 ) through a bolt and a screw hole ( 502 ); and wherein the bearing table ( 5 ) is affixed to the wafer spindle base ( 6 ) located on a grinding machine.
2. A wafer grinding force on-line measuring device according to claim 1 , wherein the wafer ( 1 ) is chosen from the group consisting of silicon wafer, silicon carbide wafer, gallium arsenide wafer, zinc telluride cadmium wafer, and zinc oxide wafer.
3. A wafer grinding force on-line measuring device according to claim 1 , wherein the bonding adhesive ( 2 ) is chosen from the group consisting of temporary bonding adhesive, blue thin film, and double-sided adhesive tape.
4. A wafer grinding force on-line measuring device according to claim 1 , wherein the thin film pressure sensor ( 3 ) is a single-point thin film pressure sensor, or an array type thin film pressure sensor, or a combination thereof.
5. A wafer grinding force on-line measuring device according to claim 1 , wherein the thinfilm pressure sensor is uniformly distributed along direction of radius of the wafer or crystal direction of the wafer.
6. A wafer grinding force on-line measuring device according to claim 1 , wherein the worktable ( 4 ) comprises the work surface ( 404 ), a fixed platform ( 405 ) and a bolt hole ( 402 ); wherein the work surface ( 404 ) have a height no lower than that of the fixed platform ( 405 ), wherein the thickness of the worktable ( 4 ) is no less than 1 cm.
7. A wafer grinding force on-line measuring device according to claim 1 , wherein the bearing table ( 5 ) comprises the cavity ( 503 ) and the screw hole ( 502 ).
8. A wafer grinding force on-line measuring device according to claim 1 , wherein the bearing table ( 5 ) and the grinding machine is affixed by vacuum adsorption or a bolt connection.
9. A method for on-line measurement of wafer grinding force, comprising the steps of:
step 1: providing the wafer grinding force on-line measuring device as described in claim 1 ;
step 2: providing a calibrated force hammer, applying a constant force migrating across the surface of the wafer; when the hammer migrates across a central position of the thin film pressure sensor, recording a pressure of the hammer and a voltage of the thin film pressure sensor; changing the pressure and repeating the above steps to establish a relationship between the pressure of the hammer and the voltage of the thin film pressure sensor; and
step 3: installing the on-line measuring device of wafer thinning grinding force on a bench of a grinding machine, grinding a wafer, and monitoring the thin film pressure sensor voltage signal in real time, wherein when a grinding wheel contacts and leaves the thin film pressure sensor, the voltage signal first increases and then decreases; recording the maximum voltage signal as U t , deducing grinding force Ft based on the relationship between pressure and voltage established in step 2, thus measuring the grinding force;
wherein a corresponding stress is σ=F t /A max , wherein Amax is the maximum contact area between a grinding tooth and the thin film pressure sensor.
10. A method for on-line measurement of the wafer grinding force according to claim 9 , wherein: the geometric shape of the force hammer is identical to that of the grinding tooth of the grinding wheel.