Method for detecting depth of groove of grinding pad

Abstract

The invention provides a grinding pad groove depth detection method, which comprises the following steps that a grinding disc is controlled to rotate to an initial position, a polishing head is controlled to move to a preset position, and a detector on the polishing head can emit detection light to a grinding pad; controlling the polishing head to drive the detector to move according to a preset movement track; obtaining a first series of values below the motion trail of the polishing head and calculating a groove depth value of the polishing pad before polishing; the polishing head is controlled to move downwards to the grinding position, the grinding disc is controlled to drive the grinding pad to rotate, and meanwhile the polishing head is controlled to rotate and / or move relative to the grinding pad for grinding; the grinding disc is controlled to rotate to the initial position, and the polishing head is controlled to ascend to the preset position and rotate according to the preset movement track; obtaining a second series of values below the motion trail of the polishing head and calculating a groove depth value of the grinding pad after grinding; comparing the difference between the groove depth value before grinding and the groove depth value after grinding; the grinding device is high in working efficiency and cannot pollute the grinding pad.

Description

Technical Field

[0001] The invention relates to the field of semiconductor technology, and in particular to a method for detecting the depth of a grinding pad groove. Background Art

[0002] Chemical mechanical planarization, or CMP, is a process technology that can achieve global planarization of semiconductor components (such as wafers). CMP equipment includes a grinding disc and a polishing head. The grinding disc is provided with a grinding pad. The polishing head absorbs the wafer onto the grinding pad and the surface of the wafer is planarized by relative movement or relative rotation between the polishing head and the grinding disc.

[0003] The surface of the polishing pad is provided with many grooves. As the planarization process proceeds, the grooves will gradually become thinner and consumed. After the polishing pad has been used for a certain period of time, the planarization efficiency of the wafer becomes very poor. Therefore, the polishing pad is a consumable material, and the service life of the polishing pad is a very important factor. A new polishing pad needs to be replaced in time to continue processing the wafer and ensure the output of the factory.

[0004] In the prior art, when the CMP equipment is shut down, the depth of the groove of the polishing pad is measured manually with a tool to determine the consumption of the groove and whether a new polishing pad needs to be replaced. This detection method requires manual measurement, which is not only inefficient, but also easy to contaminate the polishing pad. Summary of the invention

[0005] The object of the present invention is to provide a method for detecting the depth of a grinding pad groove which has high working efficiency and will not pollute the grinding pad.

[0006] In order to achieve the above-mentioned purpose, the present invention provides a method for detecting the groove depth of a grinding pad, comprising a grinding disc and a polishing head, wherein a grinding pad is arranged on the grinding disc, and the polishing head is arranged above the grinding pad, and the detection method comprises the following steps:

[0007] Control the grinding disc to rotate to an initial position, control the polishing head to move to a preset position, the preset position is set above the grinding pad, and a detector is set on the polishing head, and the detector can emit detection light to the grinding pad;

[0008] Control the polishing head to drive the detector to move along a preset motion trajectory;

[0009] Obtaining a first series of values ​​below the polishing head motion trajectory and calculating a pre-grinding groove depth value of the polishing pad, the first series of values ​​comprising a plurality of pre-grinding groove top distance values ​​and a plurality of pre-grinding groove bottom distance values;

[0010] Control the polishing head to move down to a grinding position, which is set just below a preset position, control the grinding disc to drive the grinding pad to rotate, and 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] Obtaining a second series of values ​​below the polishing head motion track and calculating the post-grinding groove depth value of the polishing pad, the second series of values ​​including a plurality of post-grinding groove top distance values ​​and a plurality of post-grinding groove bottom distance values;

[0013] Compare the difference between the groove depth value before grinding and the groove depth value after grinding.

[0014] It can be seen from the above scheme that by performing automatic detection once before and after grinding and calculating the corresponding groove depth values, and then comparing the groove depth values ​​before and after grinding, the groove difference and consumption value of the grinding pad after grinding a wafer can be obtained, which is convenient for timely replacement of a new grinding pad. Compared with the existing technology, it has the advantages of high detection efficiency and good detection accuracy, and the automatic detection is used without contaminating the grinding pad.

[0015] A further solution is that the first series of values ​​and the second series of values ​​are arranged in sequence according to the order of acquisition, the groove depth value before grinding is the absolute value of the difference between the groove top distance value before grinding and its adjacent groove bottom distance value before grinding, and the groove depth value after grinding is the absolute value of the difference between the adjacent groove top distance value after grinding and its adjacent groove bottom distance value after grinding.

[0016] A further solution is to analyze the uniformity of the groove tops and the groove bottoms of the polishing pad before polishing based on the acquired first series of values.

[0017] A further solution is to analyze the uniformity of the groove tops and the groove bottoms of the polishing pad after polishing based on the obtained second series of values.

[0018] A further solution is that 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 and swinging back and forth in the horizontal direction.

[0019] A further solution is that the polishing head is provided with an adsorption area and a retaining ring, the adsorption area is arranged on the inner side of the retaining ring, an opening is opened on the retaining ring, and the detector is arranged in the opening and can emit a detection signal downward.

[0020] A further solution is that, during the grinding process, a third series of values ​​is obtained once at a preset time interval and the groove depth value during grinding is calculated, and the third series of values ​​includes multiple groove top distance values ​​during grinding and multiple groove bottom distance values ​​during grinding.

[0021] It can be seen from the above scheme that by intermittently obtaining the groove depth value in the current grinding process, on the one hand, it is convenient to monitor the groove depth changes of the grinding pad in real time, and on the other hand, while ensuring that the amount of data is sufficient, it is possible to minimize unnecessary data volume, which is conducive to reducing the difficulty of data analysis.

[0022] A further solution is that the third series of values ​​are data obtained during the polishing head rotates a preset number of times, the third series of values ​​are arranged in sequence according to the order of acquisition, and the groove depth value during grinding is the absolute value of the difference between the groove top distance value during grinding and its adjacent groove bottom distance value during grinding.

[0023] It can be seen from the above scheme that the above setting is helpful for the staff to analyze the groove depth consumed by a single grinding.

[0024] A further solution is that the detection method also includes a groove limit prompting step.

[0025] It can be seen from the above scheme that since grooves of different depths correspond to different grinding rates, through the above settings, it is possible to determine whether there is a problem with the wafer based on the groove limit prompt step and adjust the grinding steps or grinding process parameters in time to ensure the quality of each wafer and avoid differences in removal amount between different wafers during multi-batch grinding.

[0026] A further solution is that the groove limit prompting step includes:

[0027] Obtaining a third series of values ​​once at a first preset time interval and calculating the groove depth value during grinding;

[0028] Determine whether the groove depth value in the current grinding is less than a preset threshold;

[0029] If yes, the alarm module is controlled to issue a primary alarm, and the primary alarm includes at least one of the following: a sound alarm, a light alarm, and a vibration alarm;

[0030] Determine whether the current grinding work is completed;

[0031] If not, the polishing head is controlled to continue grinding until the grinding work is completed.

[0032] It can be seen from the above scheme that by comparing the groove depth value during grinding with the size of the preset threshold, it is convenient to judge whether a new grinding pad needs to be replaced before the next grinding, which has the advantages of being simple, direct and convenient; when the alarm module sounds an alarm, if the current grinding work is not completed, the grinding will continue until the new grinding pad is replaced after the grinding work is completed, thereby ensuring that the current grinding work proceeds normally.

[0033] A further solution is that, during the process of controlling the polishing head to continue grinding, the third series of values ​​are obtained again at intervals of a second preset time and the groove depth value during grinding is calculated;

[0034] Determine whether the groove depth value in the current grinding is less than a safety threshold, and the safety threshold is less than a preset threshold;

[0035] If so, the alarm module is controlled to issue a secondary alarm and adjust the grinding parameters. The secondary alarm includes at least one of the following: sound alarm, light alarm and vibration alarm. The grinding parameters include grinding time and / or grinding pressure. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 Schematic diagram of a grinding pad and a polishing head in an embodiment of the present invention.

[0037] Figure 2 Schematic diagram of trench depth measurement in an embodiment of the present invention.

[0038] Figure 3 It is a flowchart of the detection method according to an embodiment of the present invention.

[0039] Figure 4 It is a flowchart of the groove limit prompting step in an embodiment of the present invention.

[0040] The present invention is further described below in conjunction with the accompanying drawings and embodiments. DETAILED DESCRIPTION

[0041] See also Figures 1 to 3 The present embodiment provides a method for detecting the groove depth of a grinding pad, comprising a grinding disc and a polishing head 2, wherein a grinding pad 1 is arranged on the grinding disc, and the polishing head 2 is arranged above the grinding pad 1. A total of a plurality of protrusions 11 are arranged vertically and horizontally on the grinding pad 1, and a groove 12 is formed between two adjacent protrusions 11. An adsorption area 21 and a retaining ring 22 are arranged on the polishing head 2, and the adsorption area 21 is arranged on the inner side of the retaining ring 22.

[0042] The detection method of this embodiment includes the following steps:

[0043] S1: Control the grinding disc to rotate to the initial position and then keep it still, control the polishing head 2 to absorb the wafer and move it into the grinding chamber of the grinding equipment and move 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 provided on the retaining ring 22 of the polishing head 2. An opening is provided on the retaining ring 22. The detector 3 is provided in the opening and can emit a detection signal downward. 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, which calculates the distance between the target object and the laser detector by measuring the time required for the laser beam to be emitted and received. One or more detectors 3 can be provided. When two are provided, the two detectors 3 are symmetrically provided on both sides of the retaining ring 22. When three or more are provided, all detectors 3 are evenly spaced and provided on the circumference of the retaining ring 22.

[0044] S2: Control the polishing head 2 to drive the detector to move along a preset motion trajectory; the preset motion trajectory may be a trajectory of the polishing head 2 rotating around its own axis, or a trajectory of the polishing head 2 rotating around its own axis while swinging back and forth in the horizontal direction. The former is preferred in this embodiment.

[0045] S3: Obtain a first series of values ​​below the motion trajectory of the polishing head 2 and calculate the pre-grinding groove depth value of the polishing pad 1, the first series of values ​​including a plurality of pre-grinding groove top distance values ​​and a plurality of pre-grinding groove bottom distance values.

[0046] The first series of values ​​arranges the data in the order of acquisition. The groove depth value before grinding is the absolute value of the difference between the groove top distance value before grinding and the adjacent groove bottom distance value before grinding, that is, the groove depth value before grinding h 前 =|d1 前 -d2 前 |.

[0047] The groove top distance values ​​before grinding and the groove bottom distance values ​​before grinding can be arranged in a row at intervals, or the groove top distance values ​​before grinding are arranged in a row and the groove bottom distance values ​​before grinding are arranged in a row, and the groove top distance values ​​before grinding correspond to the groove bottom distance values ​​before grinding one by 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, and at the same time control the polishing head 2 to rotate and / or move relative to the grinding pad 1 for grinding.

[0049] S5: After grinding is completed, the grinding disc is controlled to rotate to the initial position, and the polishing head 2 is controlled to rise to a preset position, and then the polishing head 2 is controlled to rotate again according to a preset motion trajectory, and the rotation speed of the polishing head 2 after grinding is kept equal to the rotation speed of the polishing head 2 before grinding.

[0050] S6: Obtain a second series of values ​​below the motion trajectory of the polishing head 2 and calculate the post-grinding groove depth value of the polishing pad 1, the second series of values ​​including a plurality of post-grinding groove top distance values ​​and a plurality of post-grinding groove bottom distance values.

[0051] The second series of values ​​are arranged in the order of acquisition. The groove depth value after grinding is the absolute value of the difference between the distance value of the groove top after grinding and the distance value of the groove bottom after grinding, that is, the groove depth value after grinding h 后 =|d1 后 -d2 后 |.

[0052] The groove top distance values ​​after grinding and the groove bottom distance values ​​after grinding can be arranged in a row at intervals, or the groove top distance values ​​after grinding are arranged in a row and the groove bottom distance values ​​after grinding are arranged in a row, and the groove top distance values ​​after grinding correspond to the groove bottom distance values ​​after grinding one by one.

[0053] S7: Compare the difference between the groove depth value before grinding and the groove depth value after grinding, and the result obtained is the change value of the groove 12 depth before and after grinding. The change value can be expressed in the form of a graph, a table, etc., so that the staff can adjust the grinding parameters according to these change values ​​to avoid the difference in the removal amount between different wafers during multi-batch grinding.

[0054] The grinding parameters include but are not limited to: the rotation speed of the grinding disc, the rotation speed of the polishing head 2, the swing speed and swing distance of the polishing head 2, the grinding pressure of the polishing head 2, the grinding time, etc.

[0055] The detection method of this embodiment also includes:

[0056] According to the first series of values ​​obtained, the uniformity of the groove top and the groove bottom of the polishing pad 1 before grinding is analyzed. Specifically, by analyzing all the groove top distance values ​​before grinding, the uniformity of the groove top of the polishing pad 1 before grinding is obtained; by analyzing all the groove bottom distance values ​​before grinding, the uniformity of the groove bottom of the polishing pad 1 before grinding is obtained.

[0057] The detection method of this embodiment also includes:

[0058] According to the obtained second series of values, the uniformity of the groove top and the groove bottom of the grinding pad 1 after grinding is analyzed. Specifically, by analyzing all the groove top distance values ​​after grinding, the uniformity of the groove top of the grinding pad 1 after grinding is obtained; by analyzing all the groove bottom distance values ​​after grinding, the uniformity of the groove bottom of the grinding pad 1 after grinding is obtained.

[0059] The detection method of this embodiment also includes:

[0060] During the grinding process, the third series of values ​​are obtained once at a preset interval and the groove depth value during grinding is calculated. The third series of values ​​include multiple groove top distance values ​​during grinding and multiple groove bottom distance values ​​during grinding. The preset interval time can be set according to actual needs, for example, the third series of values ​​are obtained once at an interval of 10s. Since the detector 3 is in a working state during the grinding process, the detector 3 can obtain a large number of third series of values ​​in real time. If all the third series of values ​​are analyzed one by one, it will lead to a huge workload of analysis. Therefore, in this embodiment, the third series of values ​​are extracted once at a preset interval from these detected third series of values ​​as the analysis object. The other third series of values ​​can be classified as useless data as objects that do not need to be analyzed, which is conducive to reducing unnecessary data volume while ensuring that the data volume is sufficient, and is conducive to reducing the difficulty of data analysis.

[0061] The third series of values ​​is the data obtained during the polishing head 2 rotates a preset number of times. The preset number of times can be one or more than two times. In this example, one time is preferred. The third series of values ​​are arranged in the order of acquisition. The depth of the grinding groove is the absolute value of the difference between the distance value of the top of the grinding groove and the distance value of the bottom of the adjacent grinding groove, that is, the depth of the grinding groove h 中 =|d1 中 -d2 中 |.

[0062] The groove top distance values ​​during grinding and the groove bottom distance values ​​during grinding can be arranged in a row at intervals, or the groove top distance values ​​during grinding are arranged in a row and the groove bottom distance values ​​during grinding are arranged in a row, and the groove top distance values ​​during grinding and the groove bottom distance values ​​during grinding correspond to each other one by one.

[0063] See also Figure 4 The detection method of this embodiment also includes a groove limit prompting step, and the groove limit prompting step can be applied in the wafer grinding process.

[0064] The groove limit prompt steps include:

[0065] S10: During the grinding process, obtaining a third series of values ​​once at a first preset time interval and calculating the groove depth value during grinding;

[0066] S11: Determine whether the groove depth value in the current grinding is less than a preset threshold value, and the preset threshold value is slightly higher than the groove depth value of the grinding pad 1 that reaches the scrap standard.

[0067] S12: If yes, control the alarm module to issue a primary alarm, the primary alarm including at least one of the following: sound alarm, light alarm and vibration alarm.

[0068] S13: Determine whether the current grinding work is completed.

[0069] S14: If not, control the polishing head 2 to continue grinding.

[0070] S15: obtaining the third series of values ​​again after a second preset time interval and calculating the groove depth value during grinding;

[0071] S16: Determine whether the groove depth value in the current grinding is less than a safety threshold, the safety threshold is less than a preset threshold, and the safety threshold is greater than or equal to the groove depth value of the grinding pad 1 that reaches the scrap standard.

[0072] S17: If yes, the alarm module issues a secondary alarm and adjusts the grinding parameters; the secondary alarm includes at least one of the following: sound alarm, light alarm and vibration alarm; the grinding parameters include grinding time and / or grinding pressure.

[0073] S18: When the grinding work is completed, the grinding equipment is controlled to stop grinding.

[0074] That is, when the alarm module sounds an alarm, the grinding work will not be stopped immediately, and the grinding work of the current wafer needs to be continued until the grinding work of the current wafer is completed. Then, the grinding equipment is stopped, and the staff takes out the wafer and replaces the new grinding pad 1 before the next wafer is ground. After the new grinding pad 1 is replaced, the alarm module stops sounding the alarm.

[0075] In this embodiment, the alarm module is preferably a warning light, and the alarm is preferably a light warning. For example, the preset threshold is set to 3mm, the safety threshold is set to 1mm, and when the groove depth value during grinding is less than 3mm, the warning light turns yellow, and the grinding equipment can continue to grind. During this process, the detector continues to detect the groove depth value during grinding. When the groove depth value during grinding is less than 1mm, the warning light turns red. At this time, the grinding steps or grinding process parameters of the grinding equipment can be appropriately adjusted, such as extending the grinding time, increasing the grinding pressure, etc., to ensure the grinding quality of the wafer and avoid differences in the amount of removal between different wafers during multi-batch grinding.

[0076] Of course, in another embodiment, when the groove depth value during grinding is less than the safety threshold, the grinding equipment can also be controlled to immediately stop grinding and replace the new grinding pad to ensure the grinding quality of the wafer.

[0077] In summary, the present invention can obtain the groove depth difference and consumption value of the grinding pad 1 after grinding a wafer by performing automatic detection once before and after grinding and calculating the corresponding groove depth values, and then comparing the groove depth values ​​before and after grinding, so as to facilitate timely replacement of the new grinding pad 1. Compared with the prior art, the present invention has the advantages of high detection efficiency and good detection accuracy, and the automatic detection is adopted, which will not contaminate the grinding pad 1.

[0078] Finally, it should be emphasized that the above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various changes and modifications. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for detecting the groove depth of a grinding pad, comprising a grinding disc and a polishing head, wherein the grinding disc is provided with a grinding pad, and the polishing head is provided above the grinding pad, wherein: The detection method comprises the following steps: Control the grinding disc to rotate to an initial position, control the polishing head to move to a preset position, the preset position is set above the grinding pad, the polishing head is provided with a detector, and the detector can emit detection light to the grinding pad; Controlling the polishing head to drive the detector to move along a preset motion trajectory; Acquire a first series of values ​​below the motion track of the polishing head and calculate the pre-grinding groove depth value of the polishing pad, wherein the first series of values ​​includes a plurality of pre-grinding groove top distance values ​​and a plurality of pre-grinding groove bottom distance values; Controlling the polishing head to move down to a grinding position, wherein the grinding position is arranged directly below the preset position, controlling the grinding disc to drive the grinding pad to rotate, and controlling the polishing head to rotate and / or move relative to the grinding pad to perform grinding; Controlling the grinding disc to rotate to an initial position, and controlling the polishing head to rise to the preset position and rotate according to the preset motion trajectory; Obtaining a second series of values ​​below the motion trajectory of the polishing head and calculating the post-grinding groove depth value of the polishing pad, wherein the second series of values ​​includes a plurality of post-grinding groove top distance values ​​and a plurality of post-grinding groove bottom distance values; The difference between the groove depth value before grinding and the groove depth value after grinding is compared.

2. The method for detecting the depth of the polishing pad groove according to claim 1, wherein: The first series of values ​​and the second series of values ​​are arranged in sequence according to the order of acquisition. The groove depth value before grinding is the absolute value of the difference between the groove top distance value before grinding and its adjacent groove bottom distance value before grinding, and the groove depth value after grinding is the absolute value of the difference between the groove top distance value after grinding and its adjacent groove bottom distance value after grinding.

3. The method for detecting the groove depth of the polishing pad according to claim 1, wherein: Based on the first series of values ​​obtained, the uniformity of the groove tops and the groove bottoms of the polishing pad before polishing is analyzed.

4. The method for detecting the groove depth of the polishing pad according to claim 1, wherein: Based on the acquired second series of values, the uniformity of the groove tops and the groove bottoms of the polishing pad after polishing is analyzed.

5. The method for detecting the groove depth of the polishing pad according to claim 1, wherein: The preset motion trajectory is a trajectory of the polishing head rotating around its own axis, or the preset motion trajectory is a trajectory of the polishing head rotating around its own axis and swinging back and forth in a horizontal direction.

6. The method for detecting the groove depth of the polishing pad according to claim 1, wherein: The polishing head is provided with an adsorption area and a retaining ring, the adsorption area is arranged on the inner side of the retaining ring, an opening is opened on the retaining ring, and the detector is arranged in the opening and can emit a detection signal downward.

7. The method for detecting the depth of the polishing pad groove according to claim 1, wherein: During the grinding process, a third series of values ​​is acquired once at a preset time interval and the groove depth value during grinding is calculated, wherein the third series of values ​​includes a plurality of groove top distance values ​​during grinding and a plurality of groove bottom distance values ​​during grinding.

8. The method for detecting the depth of the polishing pad groove according to claim 7, wherein: The third series of values ​​are data acquired during the preset number of rotations of the polishing head. The third series of values ​​arrange the data in sequence according to the order of acquisition. The depth value of the grinding groove is the absolute value of the difference between the distance value of the top of the grinding groove and its adjacent distance value of the bottom of the grinding groove.

9. The method for detecting the groove depth of the polishing pad according to claim 7 or 8, characterized in that: The detection method also includes a groove limit prompting step.

10. The method for detecting the groove depth of the polishing pad according to claim 9, characterized in that: The groove limit prompting step includes: Obtaining a third series of values ​​once at a first preset time interval and calculating the groove depth value during grinding; Determine whether the groove depth value in the current grinding is less than a preset threshold; If yes, the alarm module is controlled to issue a primary alarm, wherein the primary alarm includes at least one of the following: a sound alarm, a light alarm, and a vibration alarm; Determine whether the current grinding work is completed; If not, the polishing head is controlled to continue grinding until the grinding work is completed.

11. The method for detecting the groove depth of the polishing pad according to claim 10, characterized in that: During the process of controlling the polishing head to continue grinding, obtaining the third series of values ​​again at intervals of a second preset time and calculating the groove depth value during grinding; Determine whether the groove depth value in the current grinding is less than a safety threshold, and the safety threshold is less than a preset threshold; If so, the alarm module is controlled to issue a secondary alarm and adjust the grinding parameters, wherein the secondary alarm includes at least one of the following: a sound alarm, a light alarm, and a vibration alarm, and the grinding parameters include grinding time and / or grinding pressure.

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