US-20260124788-A1 - METHOD AND SYSTEM FOR DETECTING COMPLETION OF INGOT SLICING PROCESS

US20260124788A1US 20260124788 A1US20260124788 A1US 20260124788A1US-20260124788-A1

Abstract

A system and method for detecting completion of ingot slicing process are provided. The method includes: holding an ingot's top and bottom surfaces with upper and lower suction cups; applying a pulling force via the upper suction cup with a load cell while an ultrasonic source vibrates the ingot; turning off the ultrasonic source when the pulling force is below a set value; performing an abnormality handling process if vacuum is not maintained between the upper suction cup and wafer or between the lower suction cup and ingot bottom, or if vacuum pressure detected by a negative pressure proportional regulator valve is below a threshold value; releasing the wafer onto a receiving tray; performing the abnormality handling process if cracks on the surface of the wafer is detected; and performing the abnormality handling process if the space between a fork suction cup and the wafer is not kept vacuum.

Inventors

Chih-Yu Ke
Kun-Wei Lin
Tung-Ying Lin

Assignees

INDUSTRIAL TECHNOLOGY RESEARCH INSTITUTE

Dates

Publication Date: 20260507
Application Date: 20251017
Priority Date: 20241105

Claims (10)

1 . A method for detecting completion of ingot slicing process, performed by a controller for detecting an ingot when the ingot undergoes an ultrasonic slicing process after the ingot is laser-modified, wherein the method comprises: controlling an upper suction cup and a lower suction cup to respectively hold a top surface and a bottom surface of the ingot, wherein the upper suction cup is connected to an ultrasonic source and is provided with a load cell, the upper suction cup applies a pulling force in a direction away from the ingot to the top surface while the ultrasonic source generate ultrasonic waves to vibrate the ingot, and the pulling force applied by the upper suction cup to the top surface is detected by the load cell; controlling the load cell to detect whether the pulling force applied by the upper suction cup to the top surface is less than a set value; if yes, the ultrasonic source is turned off, and the upper suction cup holds a wafer separated from the ingot; if no, returning to the previous step; controlling an upper vacuum pressure gauge and a lower vacuum pressure gauge to respectively detect whether a space between the upper suction cup and the wafer, and a space between the lower suction cup and the bottom surface of the ingot are kept under vacuum; if yes, proceeding to the next step; if no, an abnormality handling process is performed; controlling a negative pressure proportional regulator valve to detect whether a vacuum pressure between the upper suction cup and the wafer is less than a threshold value, wherein if yes, the abnormality handling process is performed; if no, proceeding to the next step; turning off the upper suction cup to release the wafer onto a receiving tray, and detecting, by a photoelectric proximity sensor, whether a surface of the wafer is cracked, wherein if yes, the abnormality handling process is performed; if no, proceeding to the next step; and controlling a fork suction cup to hold the wafer from the receiving tray, and detecting, by a fork vacuum pressure gauge, whether a space between the fork suction cup and the wafer is kept under vacuum; if no, the abnormality handling process is performed; if yes, the wafer is moved out of the receiving tray by the fork suction cup.
2 . The method for detecting completion of ingot slicing process as claimed in claim 1 , wherein the threshold value is 80% of a preset vacuum pressure value.
3 . The method for detecting completion of ingot slicing process as claimed in claim 1 , wherein the fork suction cup is further connected to an image capture device, and at least one image of the wafer is captured by the image capture device to determine whether a contour of the wafer is complete; if no, the abnormality handling process is performed; if yes, the wafer is moved out of the receiving tray by the fork suction cup.
4 . The method for detecting completion of ingot slicing process as claimed in claim 3 , wherein the image comprises static and/or dynamic images.
5 . The method for detecting completion of ingot slicing process as claimed in claim 1 , wherein the abnormality handling process comprises issuing an abnormality alert.
6 . The method for detecting completion of ingot slicing process as claimed in claim 1 , wherein the controller comprises a human-machine interface and a central-processing unit or a programmable micro control unit, or a programmable microprocessor.
7 . The method for detecting completion of ingot slicing process as claimed in claim 1 , wherein the set value is zero.
8 . A system for detecting completion of ingot slicing process, connected to an ultrasonic slicing machine to separate a wafer from an ingot, and comprising: a slicing device comprising an upper suction cup and a lower suction cup, wherein the upper suction cup is connected to an ultrasonic source, and the upper suction cup and the lower suction cup are configured to respectively hold a top surface and a bottom surface of the ingot, and the upper suction cup is configured to apply a pulling force in a direction away from the ingot to the top surface, while the ultrasonic source is configured to generate ultrasonic waves to vibrate the ingot; a load cell connected to the upper suction cup and configured to detect the pulling force applied by the upper suction cup to the top surface; an upper vacuum pressure gauge connected to the upper suction cup, and configured to detect a vacuum degree between the upper suction cup and the top surface; a lower vacuum pressure gauge connected to the lower suction cup, and configured to detect a vacuum degree between the lower suction cup and the bottom surface; a negative pressure proportional regulator valve connected to the upper suction cup, and configured to detect a vacuum pressure between the upper suction cup and the wafer; a receiving tray movably disposed below the upper suction cup, and configured to receive the wafer held by the upper suction cup; a photoelectric proximity sensor connected to the receiving tray, and configured to detect whether a surface of the wafer on the receiving tray is cracked; a fork suction cup movably disposed on one side of the receiving tray, and configured to hold the wafer from the receiving tray to move the wafer out of the receiving tray; a fork vacuum pressure gauge connected to the fork suction cup, and configured to detect a vacuum degree between the fork suction cup and the wafer; and a controller electrically connected to and configured to control aforementioned components.
9 . The system for detecting completion of ingot slicing process as claimed in claim 8 , further comprising an image capture device is connected to the fork suction cup, and an image of the wafer is captured by the image capture device to determine whether a contour of the wafer is complete.
10 . The system for detecting completion of ingot slicing process as claimed in claim 8 , wherein the controller comprises a human-machine interface and a central processing unit or a programmable micro control unit, or a programmable microprocessor.

Description

CROSS REFERENCE TO RELATED APPLICATION This application also claims priority to Taiwan Patent Application No. 113142247 filed in the Taiwan Patent Office on Nov. 5, 2024, the entire content of which is incorporated herein by reference. TECHNICAL FIELD The present disclosure relates to a wafer process-related technology related to wafer, in particular to a method for detecting completion of ingot slicing process and the system thereof. BACKGROUND In semiconductor processes, the procedure of separating a wafer from an ingot is referred to as “slicing.” A slicing machine is used to separate and remove a wafer from the surface of an ingot that has undergone laser modification and contains discontinuous invisible cracks. Currently available slicing methods adopt a diamond wire cutting process and an ultrasonic wet process. In the wet process, the ingot is placed in a liquid having a specific temperature (for example, water), with the liquid serving as a medium, and the wafer is separated from the ingot by means of acoustic wave vibration. However, the diamond wire cutting process suffers from higher material loss and slower cutting speed. The cutting process results in a material loss of approximately 260 μm. Considering a wafer thickness of 350 μm, this translates to almost one entire wafer being wasted per cut. Furthermore, the surface of the wafer after separation is rough, requiring subsequent surface machining and grinding. Accordingly, a technical approach for slicing by using laser light in combination with ultrasonic vibration and suction cups is developed. Laser light is used to form a modified layer with cracks inside the ingot, and in conjunction with ultrasonic vibration and the suction force applied by the suction cups, a fragment (i.e., the wafer) formed by the cracks extending from the modified layer is separated from the ingot. Compared with diamond wire cutting, laser modification can increase the number of wafers obtained. For example, if the thickness of the ingot is 20,000 μm and wafers of 350 μm thickness are to be cut, the material loss per wafer by diamond wire cutting is 260 μm, while the material loss per wafer by laser modification is 80 μm. Diamond wire cutting can produce 32 wafers, whereas laser modification can produce 46 wafers. Although the slicing method using laser light in combination with ultrasonic vibration and suction cups is faster and involves lower material loss, improper coordination between the ultrasonic vibration and the suction cups often results in wafers being fractured by the ultrasonic vibration. In addition, in the process of separating the wafer from the ingot using suction cups, opposite upper and lower suction cups respectively act on the wafer and the ingot by suction. If the vacuum degree between the suction cups and the wafer and ingot is not properly controlled, the wafer is prone to cracking during the separation process. Furthermore, during the process of transferring the wafer to a cassette, for example, when the wafer held by a suction cup is released onto a receiving tray, or when the wafer is transferred by a fork, the fragile wafer is easily broken. Accordingly, it has become an important issue to provide a “method and system for detecting completion of ingot slicing process” capable of confirming that the slicing process of a wafer is successful and the wafer does not crack. SUMMARY One embodiment of the disclosure provides a method for detecting completion of ingot slicing process. The method is performed by a controller and includes the following steps: controlling an upper suction cup and a lower suction cup to respectively hold the top surface and the bottom surface of the ingot, wherein the upper suction cup is connected to an ultrasonic source and is provided with a load cell, the upper suction cup applies a pulling force in the direction away from the ingot to the top surface while the ultrasonic source generate ultrasonic waves to vibrate the ingot, and the pulling force applied by the upper suction cup to the top surface is detected by the load cell; controlling the load cell to detect whether the pulling force applied by the upper suction cup to the top surface is less than a set value; if yes, the ultrasonic source is turned off, and the upper suction cup holds a wafer separated from the ingot; if no, returning to the previous step; controlling an upper vacuum pressure gauge and a lower vacuum pressure gauge to respectively detect whether the space between the upper suction cup and the wafer, and the space between the lower suction cup and the bottom surface of the ingot are kept under vacuum; if yes, proceeding to the next step; if no, an abnormality handling process is performed; controlling a negative pressure proportional regulator valve to detect whether the vacuum pressure between the upper suction cup and the wafer is less than a threshold value, wherein if yes, the abnormality handling process is performed; if no, proceeding to