A method for detecting a groove depth of a polishing pad
By automatically detecting the depth of the polishing pad grooves, the problems of low efficiency and contamination in existing technologies have been solved, enabling efficient and accurate polishing pad replacement and ensuring the continuity and quality of wafer processing.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- STAR KEY SEMICONDUCTOR (WUHAN) CO LTD
- Filing Date
- 2024-11-05
- Publication Date
- 2026-07-07
AI Technical Summary
In the existing technology, the detection efficiency of the groove depth of the polishing pad is low and the polishing pad is easily contaminated, resulting in inaccurate judgment of the polishing pad's service life and affecting the wafer planarization efficiency.
An automatic detection method is adopted, which uses a detector on the polishing head to obtain the groove depth value before and after polishing, calculates the difference in groove depth, and combines a preset motion trajectory and an alarm module to achieve automated detection and timely replacement of polishing pads.
It improves detection efficiency and accuracy, avoids contamination of the grinding pad, ensures the continuity and quality of wafer processing, and reduces the differences in grinding multiple batches.
Smart Images
Figure CN119526255B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of semiconductor technology, and more specifically to a method for detecting the depth of grinding pad trenches. Background Technology
[0002] Chemical mechanical planarization (CMP) is a process technology that enables global planarization of semiconductor devices (such as wafers). CMP equipment includes a grinding disc and a polishing head. The grinding disc is equipped with a grinding pad, and the polishing head picks up the wafer and places it onto the grinding pad. Through the relative movement or rotation of the polishing head and the grinding disc, the wafer surface is planarized.
[0003] The surface of the polishing pad has numerous grooves. As the planarization process proceeds, these grooves gradually thin and wear down. After a certain period of use, the planarization efficiency of the wafer becomes very poor. Therefore, the polishing pad is a consumable material, and its lifespan is a crucial factor. It is necessary to replace the polishing pad with a new one in a timely manner to continue wafer processing and ensure factory output.
[0004] Current technology typically involves manually measuring the depth of the polishing pad grooves using tools when the CMP equipment is shut down to assess the wear and determine if the polishing pads need to be replaced. This method requires manual measurement, which is not only inefficient but also prone to contaminating the polishing pads. Summary of the Invention
[0005] The purpose of this invention is to provide a method for detecting the groove depth of an abrasive pad that is highly efficient and does not contaminate the abrasive pad.
[0006] To achieve the above objectives, the present invention provides a method for detecting the groove depth of an abrasive pad, comprising an abrasive disc and a polishing head, wherein an abrasive pad is disposed on the abrasive disc and the polishing head is disposed above the abrasive pad, characterized in that the detection method comprises the following steps:
[0007] The grinding disc is rotated to the initial position, and the polishing head is moved to the preset position. The preset position is set above the grinding pad. A detector is installed on the polishing head, and the detector can emit detection light toward the grinding pad.
[0008] The polishing head is controlled to drive the detector to move along a preset trajectory.
[0009] Obtain the first series of values below the movement trajectory of the polishing head and calculate the depth of the pre-grinding groove of the grinding pad. The first series of values includes multiple pre-grinding groove top distance values and multiple pre-grinding groove bottom distance values.
[0010] Control the polishing head to move down to the grinding position, which is set directly below the preset position. Control the grinding disc to drive the grinding pad to rotate, and at the same time control the polishing head to rotate and / or move relative to the grinding pad to perform grinding.
[0011] Control the grinding disc to rotate to the initial position, control the polishing head to rise to the preset position and rotate according to the preset motion trajectory;
[0012] Obtain the second series of values below the movement trajectory of the polishing head and calculate the depth of the groove after grinding on the grinding pad. The second series of values includes multiple distance values from the top of the groove after grinding and multiple distance values from the bottom of the groove after grinding.
[0013] Compare the difference between the groove depth values before and after grinding.
[0014] As can be seen from the above scheme, by performing automatic detection and calculating the corresponding trench depth values before and after grinding, and then comparing the trench depth values before and after grinding, the trench difference and consumption value of the grinding pad after grinding a wafer can be obtained, which facilitates timely replacement of the new grinding pad. Compared with the existing technology, it has the advantages of high detection efficiency and good detection accuracy. Moreover, the automatic detection will not contaminate the grinding pad.
[0015] A further approach is to arrange the first and second series values in the order they were acquired, with the groove depth before grinding being the absolute value of the difference between the top distance of the groove before grinding and the bottom distance of its adjacent groove before grinding, and the groove depth after grinding being the absolute value of the difference between the top distance of the adjacent groove after grinding and the bottom distance of its adjacent groove after grinding.
[0016] A further approach is to analyze the uniformity of the top and bottom of the grooves of the grinding pad before grinding, based on the first series of values obtained.
[0017] A further approach is to analyze the uniformity of the top and bottom of the grooves on the grinding pad after grinding, based on the obtained second series of values.
[0018] A further approach is to preset the motion trajectory as the trajectory of the polishing head rotating around its own axis, or to preset the motion trajectory as the trajectory of the polishing head rotating around its own axis while swinging back and forth in the horizontal direction.
[0019] A further design involves a polishing head with an adsorption area and a retaining ring. The adsorption area is located inside the retaining ring, which has an opening. The detector is located inside the opening and can emit a detection signal downwards.
[0020] A further approach is to acquire a third series of values at preset intervals during the grinding process and calculate the groove depth values during grinding. The third series of values includes multiple groove top distance values and multiple groove bottom distance values during grinding.
[0021] As can be seen from the above scheme, by intermittently acquiring the current groove depth value during the grinding process, on the one hand, it is convenient to monitor the changes in the groove depth of the grinding pad in real time, and on the other hand, while ensuring sufficient data volume, it minimizes unnecessary data volume, which helps to reduce the difficulty of data analysis.
[0022] A further approach is to use the third series of values as data acquired during the preset number of rotations of the polishing head. The third series of values are arranged sequentially according to the order of acquisition, and the groove depth value during grinding is the absolute value of the difference between the distance to the top of the groove and the distance to the bottom of its adjacent groove.
[0023] As can be seen from the above scheme, the above settings make it easier for staff to analyze the groove depth consumed in a single grinding process.
[0024] A further approach is to include a trench limit indication step in the detection method.
[0025] As can be seen from the above scheme, since different depths of trenches correspond to different grinding rates, the above settings can be used to determine whether there is a problem with the wafer based on the trench limit prompt steps and adjust the grinding steps or grinding process parameters in a timely manner to ensure the quality of each wafer and avoid differences in the amount of material removed between different wafers during multi-batch grinding.
[0026] A further proposed solution is to include the following steps for providing trench limit indication:
[0027] The third series of values are obtained once at a first preset time interval, and the groove depth value during grinding is calculated.
[0028] Determine whether the current groove depth value during grinding is less than a preset threshold;
[0029] If so, the control alarm module will issue an initial alarm, which includes at least one of the following: audible alarm, visual alarm, and vibration alarm;
[0030] Determine whether the current grinding process is complete;
[0031] If not, control the polishing head to continue polishing until the current polishing operation is completed.
[0032] As can be seen from the above scheme, by comparing the groove depth value during grinding with the preset threshold, it is easy to determine whether a new grinding pad needs to be replaced before the next grinding. This has the advantages of being simple, direct and convenient. When the alarm module issues an alarm, if the current grinding work is not completed, grinding will continue until the grinding work is completed before a new grinding pad is replaced, ensuring that the current grinding work proceeds normally.
[0033] A further approach is to obtain the third series of values again and calculate the groove depth value during grinding at a second preset time interval while controlling the polishing head to continue grinding.
[0034] Determine whether the current groove depth value during grinding is less than the safety threshold; if the safety threshold is less than the preset threshold.
[0035] If so, the control alarm module will issue a secondary alarm and adjust the grinding parameters. The secondary alarm shall include at least one of the following: audible alarm, visual alarm, and vibration alarm. The grinding parameters shall include grinding time and / or grinding pressure. Attached Figure Description
[0036] Figure 1 This is a schematic diagram of the grinding pad and polishing head in an embodiment of the present invention.
[0037] Figure 2 This is a schematic diagram of trench depth measurement in an embodiment of the present invention.
[0038] Figure 3 This is a flowchart of the detection method according to an embodiment of the present invention.
[0039] Figure 4 This is a flowchart of the groove limit indication step in an embodiment of the present invention.
[0040] The present invention will be further described below with reference to the accompanying drawings and embodiments. Detailed Implementation
[0041] See Figures 1 to 3 This embodiment provides a method for detecting the groove depth of an abrasive pad, including an abrasive disc and a polishing head 2. An abrasive pad 1 is disposed on the abrasive disc, and the polishing head 2 is disposed above the abrasive pad 1. Multiple protrusions 11 are arranged longitudinally and transversely on the abrasive pad 1, and grooves 12 are formed between adjacent protrusions 11. The polishing head 2 is provided with an adsorption area 21 and a retaining ring 22, with the adsorption area 21 disposed inside the retaining ring 22.
[0042] The detection method in this embodiment includes the following steps:
[0043] S1: After the grinding disc rotates to its initial position and remains stationary, the polishing head 2 picks up the wafer and moves it into the grinding chamber of the grinding equipment, then moves it to a preset position, which is set above the grinding pad 1. A detector 3 is provided on the polishing head 2. Preferably, the detector 3 is located on the retaining ring 22 of the polishing head 2. The retaining ring 22 has an opening, and the detector 3 is positioned within the opening and can emit a detection signal downwards. The detector can be an optical detector, and the detection signal can be an optical signal. In this embodiment, the detector 3 is preferably a laser detector. The distance between the target object and the laser detector is calculated by measuring the time required for the laser beam to travel from emission to reception. One or more detectors 3 can be provided. When two detectors are provided, they are symmetrically arranged on both sides of the retaining ring 22. When three or more detectors are provided, all detectors 3 are evenly spaced around the circumference of the retaining ring 22.
[0044] S2: Control the polishing head 2 to drive the detector to move according to a preset motion trajectory; the preset motion trajectory can be the trajectory of the polishing head 2 rotating around its own axis, or it can be the trajectory of the polishing head 2 rotating around its own axis while swinging back and forth in the horizontal direction. In this embodiment, the former is preferred.
[0045] S3: Obtain the first series of values below the motion trajectory of the polishing head 2 and calculate the depth value of the pre-grinding groove of the grinding pad 1. The first series of values includes multiple pre-grinding groove top distance values and multiple pre-grinding groove bottom distance values.
[0046] The first series of values are arranged sequentially according to the order in which they were acquired. The groove depth before grinding is the absolute value of the difference between the distance from the top of the groove before grinding and the distance from the bottom of its adjacent groove before grinding, i.e., the groove depth value h before grinding. 前 =|d1 前 -d2 前 |
[0047] The distance values of the top and bottom of the groove before grinding can be arranged in a row at intervals, or the distance values of the top and bottom of the groove before grinding can be arranged in a row, and the distance values of the top and bottom of the groove before grinding correspond one-to-one.
[0048] S4: Control the polishing head 2 to move down to the grinding position, which is set directly below the preset position. Control the grinding disc to rotate around its own axis, thereby driving the grinding pad 1 to rotate synchronously. At the same time, control the polishing head 2 to rotate and / or move relative to the grinding pad 1 to perform grinding.
[0049] S5: After grinding is completed, control the grinding disc to rotate to the initial position and control the polishing head 2 to rise to the preset position. Then control the polishing head 2 to rotate again according to the preset motion trajectory, and keep the rotation speed of the polishing head 2 after grinding equal to the rotation speed of the polishing head 2 before grinding.
[0050] S6: Obtain the second series of values below the movement trajectory of the polishing head 2 and calculate the depth of the groove after grinding of the grinding pad 1. The second series of values includes multiple distance values from the top of the groove after grinding and multiple distance values from the bottom of the groove after grinding.
[0051] The second series of values are arranged sequentially according to the order in which they were acquired. The groove depth after grinding is the absolute value of the difference between the distance from the top of the groove after grinding and the distance from the bottom of its adjacent groove after grinding, i.e., the groove depth value h after grinding. 后 =|d1 后 -d2 后 |
[0052] The distance values of the top and bottom of the groove after grinding can be arranged in a row at intervals, or the distance values of the top and bottom of the groove after grinding can be arranged in a row, and the distance values of the top and bottom of the groove after grinding correspond one-to-one.
[0053] S7: Compare the difference between the trench depth before and after grinding. The result is the change in trench depth before and after grinding. This change can be represented in the form of graphs, tables, etc., so that staff can adjust the grinding parameters according to these changes to avoid differences in the amount of material removed between different wafers during multi-batch grinding.
[0054] Grinding parameters include, but are not limited to: the rotation speed of the grinding disc, the rotation speed of the polishing head 2, the oscillation speed and oscillation distance of the polishing head 2, the grinding pressure of the polishing head 2, and the grinding time.
[0055] The detection method in this embodiment also includes:
[0056] Based on the first series of values obtained, the uniformity of the groove top and bottom of the grinding pad 1 before grinding is analyzed. Specifically, the uniformity of the groove top of the grinding pad 1 before grinding is obtained by analyzing all groove top distance values before grinding; the uniformity of the groove bottom of the grinding pad 1 before grinding is obtained by analyzing all groove bottom distance values before grinding.
[0057] The detection method in this embodiment also includes:
[0058] Based on the obtained second series of values, the uniformity of the groove tops and bottoms of the grinding pad 1 after grinding is analyzed. Specifically, the uniformity of the groove tops of the grinding pad 1 after grinding is obtained by analyzing all the groove top distance values after grinding; the uniformity of the groove bottoms of the grinding pad 1 after grinding is obtained by analyzing all the groove bottom distance values after grinding.
[0059] The detection method in this embodiment also includes:
[0060] During the grinding process, a third series value is acquired at preset time intervals, and the groove depth is calculated. The third series value includes multiple groove top distance values and multiple groove bottom distance values. The preset time interval can be set according to actual needs, for example, acquiring the third series value at 10-second intervals. Since the detector 3 is in working condition during the grinding process, it can acquire a large number of third series values in real time. If all the third series values were analyzed one by one, the workload would be enormous. Therefore, in this embodiment, a third series value is extracted once from these detected third series values at preset time intervals as the analysis object. Other third series values can be classified as useless data and not analyzed. This helps to reduce unnecessary data volume while ensuring sufficient data volume, and reduces the difficulty of data analysis.
[0061] The third series of values are data acquired during the rotation of polishing head 2 a preset number of revolutions. The preset number of revolutions can be one revolution or two or more; in this example, one revolution is preferred. The third series of values are arranged sequentially according to the order of acquisition. The groove depth value during grinding is the absolute value of the difference between the distance from the top of the groove and the distance from the bottom of its adjacent groove, i.e., the groove depth value h. 中 =|d1 中 -d2 中 |
[0062] The distance values at the top and bottom of the grooves during grinding can be arranged in a row at intervals, or the distance values at the top and bottom of the grooves during grinding can be arranged in a row, and the distance values at the top and bottom of the grooves during grinding correspond one-to-one.
[0063] See Figure 4 The detection method in this embodiment also includes a trench limit prompting step, which can be applied to the wafer grinding process.
[0064] The steps for providing a trench limit indication include:
[0065] S10: During the grinding process, the third series of values are acquired once at a first preset time interval and the groove depth value during grinding is calculated;
[0066] S11: Determine whether the groove depth value during the current grinding process is less than the preset threshold. The preset threshold is slightly higher than the groove depth value of the grinding pad 1 that has reached the scrapping standard.
[0067] S12: If so, the control alarm module will issue an initial alarm, which includes at least one of the following: sound alarm, light alarm, and vibration alarm.
[0068] S13: Determine whether the current grinding work is complete.
[0069] S14: If not, control polishing head 2 to continue grinding.
[0070] S15: After a second preset time interval, obtain the third series of values again and calculate the groove depth value during grinding;
[0071] S16: Determine whether the groove depth value in the current grinding process is less than the safety threshold. If the safety threshold is less than the preset threshold and the safety threshold is greater than or equal to the groove depth value of the grinding pad 1 that has reached the scrapping standard.
[0072] S17: If so, the alarm module will issue a secondary alarm and adjust the grinding parameters; the secondary alarm shall include at least one of the following: audible alarm, visual alarm and vibration alarm; the grinding parameters shall include grinding time and / or grinding pressure.
[0073] S18: When the grinding operation is completed, control the grinding equipment to stop grinding.
[0074] That is, when the alarm module issues an alarm, the current grinding operation will not stop immediately. Grinding must continue until the grinding of the current wafer is completed. Then, the grinding equipment will stop, and the operator will remove the wafer and replace it with a new grinding pad 1 before proceeding to the next wafer. The alarm module will only stop issuing alarms after the new grinding pad 1 is replaced.
[0075] In this embodiment, the alarm module is preferably a warning light, and the alarm is preferably a light-based warning. For example, a preset threshold of 3mm and a safety threshold of 1mm are set. When the groove depth during grinding is less than 3mm, the warning light illuminates yellow, and the grinding equipment can continue grinding. During this process, the detector continues to monitor the groove depth during grinding. When the groove depth is less than 1mm, the warning light illuminates red. At this point, the grinding steps or grinding process parameters of the grinding equipment can be adjusted appropriately, such as extending the grinding time or increasing the grinding pressure, to ensure the grinding quality of the wafer and avoid differences in the amount of material removed between different wafers during multi-batch grinding.
[0076] Of course, in another embodiment, when the trench depth value during grinding is less than the safety threshold, the grinding equipment can be controlled to stop grinding immediately and replace with a new grinding pad to ensure the grinding quality of the wafer.
[0077] In summary, this invention automatically detects and calculates the corresponding trench depth values before and after grinding, and then compares the trench depth values before and after grinding to obtain the difference in trench depth and consumption value of the grinding pad 1 after grinding a wafer. This facilitates timely replacement of the new grinding pad 1. Compared with the prior art, it has the advantages of high detection efficiency and good detection accuracy. Moreover, the automatic detection method does not contaminate the grinding pad 1.
[0078] Finally, it should be emphasized that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A method for detecting the groove depth of an abrasive pad, comprising an abrasive disc and a polishing head, wherein an abrasive pad is disposed on the abrasive disc, and the polishing head is disposed above the abrasive pad, characterized in that, The detection method includes the following steps: After the grinding disc is rotated to the initial position and then fixed, the polishing head is moved to a preset position. The preset position is set above the grinding pad. The polishing head is equipped with a detector that can emit detection light towards the grinding pad. The polishing head is controlled to drive the detector to move according to a preset motion trajectory before grinding. The preset motion trajectory is the trajectory of the polishing head rotating around its own axis, or the preset motion trajectory is the trajectory of the polishing head rotating around its own axis while swinging back and forth in the horizontal direction. Obtain a first series of values below the movement trajectory of the polishing head and calculate the pre-grinding groove depth value of the grinding pad. The first series of values includes multiple pre-grinding groove top distance values and multiple pre-grinding groove bottom distance values. The polishing head is controlled to move down to the grinding position, which is set directly below the preset position. The grinding disc is controlled to drive the grinding pad to rotate, and the polishing head is controlled to rotate and / or move relative to the grinding pad to perform grinding. After the grinding disc is rotated to the initial position, the polishing head is controlled to rise to the preset position after grinding and rotate according to the preset motion trajectory; Obtain the second series of values below the movement trajectory of the polishing head and calculate the groove depth value of the polishing pad after polishing. The second series of values includes multiple groove top distance values and multiple groove bottom distance values after polishing. Compare the difference between the groove depth value before grinding and the groove depth value after grinding; The grinding parameters for the next grinding cycle are adjusted based on the difference between the groove depth value before grinding and the groove depth value after grinding.
2. The method for detecting the groove depth of the grinding pad according to claim 1, characterized in that: The first series of values and the second series of values are arranged in order of acquisition. The groove depth before grinding is the absolute value of the difference between the top distance of the groove before grinding and the bottom distance of its adjacent groove before grinding. The groove depth after grinding is the absolute value of the difference between the top distance of the groove after grinding and the bottom distance of its adjacent groove after grinding.
3. The method for detecting the groove depth of the grinding pad according to claim 1, characterized in that: Based on the first series of values obtained, the uniformity of the groove top and groove bottom of the grinding pad before grinding is analyzed.
4. The method for detecting the groove depth of the grinding pad according to claim 1, characterized in that: Based on the obtained second series of values, the uniformity of the groove top and groove bottom of the grinding pad after grinding is analyzed.
5. The method for detecting the groove depth of the grinding pad according to claim 1, characterized in that: The polishing head is provided with an adsorption area and a retaining ring. The adsorption area is located inside the retaining ring, and the retaining ring has an opening. The detector is located inside the opening and can emit a detection signal downwards.
6. The method for detecting the groove depth of an abrasive pad according to claim 1, characterized in that: During the grinding process, a third series of values are acquired at preset intervals and the groove depth value during grinding is calculated. The third series of values includes multiple groove top distance values and multiple groove bottom distance values during grinding.
7. The method for detecting the groove depth of an abrasive pad according to claim 6, characterized in that: The third series values are data obtained during the process of the polishing head rotating a preset number of times. The third series values are arranged in order of acquisition. The groove depth value in grinding is the absolute value of the difference between the distance to the top of the grinding groove and the distance to the bottom of its adjacent grinding groove.
8. The method for detecting the groove depth of an abrasive pad according to claim 6 or 7, characterized in that: The detection method also includes a trench limit indication step.
9. The method for detecting the groove depth of an abrasive pad according to claim 8, characterized in that: The trench limit indication step includes: The third series of values are obtained once at a first preset time interval, and the groove depth value during grinding is calculated. Determine whether the current groove depth value during grinding is less than a preset threshold; If so, the control alarm module will issue an initial alarm, which includes at least one of the following: audible alarm, visual alarm, and vibration alarm; Determine whether the current grinding process is complete; If not, the polishing head is controlled to continue grinding until the current grinding operation is completed.
10. The method for detecting the groove depth of an abrasive pad according to claim 9, characterized in that: During the process of controlling the polishing head to continue grinding, the third series of values are obtained again at a second preset time interval, and the groove depth value during grinding is calculated. Determine whether the current groove depth value during grinding is less than the safety threshold; if the safety threshold is less than the preset threshold. If so, the control alarm module issues a secondary alarm and adjusts the grinding parameters. The secondary alarm includes at least one of the following: audible alarm, visual alarm, and vibration alarm. The grinding parameters include grinding time and / or grinding pressure.