Method and device for improving leveling effect of grinding pad

Abstract

The invention discloses a method for improving the leveling effect of a polishing pad and a chemical mechanical polishing device.The method for improving the leveling effect of the polishing pad comprises the steps that the surface of the polishing pad is divided into n subareas along the swing track of a leveler, and n is a positive integer larger than 1; partition pressure, namely input pressure, borne by the surface of a leveling disc on the leveler in the ith partition is detected, the output pressure of the leveler in the ith partition is adjusted according to the following formula, i belongs to [1, n], the corrected output pressure Di of the ith partition is equal to the initial set pressure A + the compensation pressure Ci of the ith partition, # imgabs0 #, K is a compensation coefficient, n is a positive integer, and n is a positive integer. The value range of K is 0.1-1.0, and bi is the subarea pressure generated by the ith subarea on the polishing pad on the surface of the leveling disc; # imgabs1 # B is the average pressure obtained by averaging the subarea pressure generated by each subarea on the surface of the leveling disc. The problem of uneven consumption of grooves in the surface of the grinding pad can be solved, and the leveling effect of the grinding pad is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of integrated circuit manufacturing, and in particular relates to a method and a device for improving the leveling effect of a grinding pad. Background Art

[0002] During chemical mechanical polishing (CMP), the polishing head presses the wafer and applies pressure, and relative rotation is used to provide the mechanical force required for material removal during polishing. The grooves on the surface of the CMP pad are used to transport the polishing fluid and discharge polishing byproducts. However, because the mechanical contact of the polishing mechanism, that is, the contact between the grooves on the surface of the polishing pad and the wafer of the polishing head, is uneven, the consumption of the grooves of the polishing pad is also uneven. The uneven grooves caused by local excessive consumption will affect the stability of the transmission of the polishing fluid and byproducts, and significantly shorten the service life of the polishing pad.

[0003] The conditioner is mainly composed of a conditioner arm, a cylinder and a conditioner disk (also called a diamond disk). One end of the conditioner arm is fixed to the outside of the grinding pad, and the other end is connected to the cylinder. The piston end of the cylinder is connected to the diamond disk, and the diamond disk is installed on the conditioner arm. The diamond disk is controlled by the conditioner arm and swings back and forth along a fixed path. The position of the diamond disk (the distance from the center of the grinding pad) is recorded in real time. The cylinder provides downward pressure on the surface of the grinding pad. Small diamonds are installed on the surface of the diamond disk, which plays a role in trimming the surface of the grinding pad by scraping off the surface material. Summary of the invention

[0004] In view of all or part of the deficiencies of the prior art described above, the object of the present invention is to provide a method for improving the smoothing effect of a polishing pad and a chemical mechanical polishing device, which can improve the problem of uneven consumption of grooves on the surface of the polishing pad, thereby improving the smoothing effect of the polishing pad, preventing the stability of the transmission of the polishing liquid and by-products from being affected, and extending the service life of the polishing pad.

[0005] In order to achieve the above-mentioned invention object, the present invention provides the following technical solutions:

[0006] The present invention provides a method for improving the leveling effect of a grinding pad, comprising dividing the surface of the grinding pad into n partitions along the swing trajectory of a leveler, where n is a positive integer greater than 1, respectively detecting the partition pressure, i.e., the input pressure, on the surface of the leveling disk on the leveler in the i-th partition, and adjusting the output pressure of the leveler in the i-th partition according to the following formula, where i∈[1,n]:

[0007] Corrected output pressure D of the i-th partition i = Initial set pressure A + compensation pressure C of the ith zonei ;

[0008] Among them, K is the compensation coefficient, the value range of K is 0.1-1.0, b i is the partition pressure generated by the i-th partition on the polishing pad on the surface of the flat disk; B is the average pressure obtained by adding up and averaging the partition pressures generated by each partition on the surface of the flat disk.

[0009] The present invention collects the contact pressure between the leveler and the grinding pad by partitions, calculates the pressure that needs to be compensated for each partition, performs decompression compensation for the area with small contact pressure to reduce the groove consumption rate of the partition, and performs pressure increase compensation for the area with large contact pressure to increase the groove consumption rate of the partition. Adjusting the partition pressure of the leveler can improve the uneven consumption of the grooves on the grinding pad, make the groove height on the surface of the grinding pad tend to be uniform, improve the leveling effect of the grinding pad, prevent the stability of the transmission of grinding liquid and by-products from being affected, and extend the service life of the grinding pad.

[0010] The corrected output pressure D of the i-th partition i The method for obtaining the pressure is as follows: the flexible pressure sensor continuously or intermittently detects the partition pressure generated by each partition on the surface of the flat disk, calculates the partition pressures of the n partitions to obtain the average pressure B, and finally obtains the compensation pressure C of the i-th partition. i and the corrected output pressure D of the i-th partition i The flexible pressure sensor is more suitable for the pressure detection requirements of the groove surface of the polishing pad and can also withstand certain deformation.

[0011] n=10, the surface of the polishing pad is evenly divided into 10 partitions along the swing trajectory of the leveler, and the pattern of the partition is a ring-shaped area distributed around the center of the polishing pad; a plurality of detection units of the flexible pressure sensor are evenly distributed on the surface of the leveling disk in an array. The more partitions are divided, the more accurate the adjustment result tends to be, further reducing the loss of the polishing pad.

[0012] The monitoring process includes a monitoring process and an adjustment process. The monitoring process is to obtain the zone pressure obtained by the leveler passing through each zone. The adjustment process is to adjust the output pressure of the leveler when the leveler passes through each zone. The monitoring process and the adjustment process are performed once or repeatedly. If the zone pressure difference between the zones is small after a single adjustment, no further adjustment is required. If a significant change occurs again, another adjustment can be made.

[0013] The adjustment process can be performed when any of the following situations is met: when the deviation value between the initial set pressure A and a single partition pressure is higher than a preset value, or when the deviation value between the initial set pressure A and multiple partition pressures are all higher than the preset value, or when the deviation value between the initial set pressure A and the average pressure B is higher than the preset value; the preset value, the initial set pressure A and the compensation coefficient K are all determined by the process requirements.

[0014] The adjustment process is performed after the grinding of an integer number of wafers is completed. The output pressure is adjusted because there is a large deviation between the detected input pressure and the set output pressure. This deviation needs to be adjusted accurately after accumulating a certain amount of data. Therefore, the adjustment can be performed after grinding several wafers. In addition, non-integer wafers mean that the wafers are not yet completed. At this time, correcting the output pressure will affect the leveling effect.

[0015] The present invention also provides a chemical mechanical polishing device, including a polishing pad, a polishing head and a planarizer arranged on the polishing pad, and the output pressure of the planarizer in any one or more of the partitions is adjusted by using the method for improving the planarization effect of the polishing pad.

[0016] The leveler includes a leveling arm, a leveling disk and a pressure control system, and the pressure control system includes a cylinder, a pressure sensor and a data processing module. The leveling arm, cylinder, pressure sensor and leveling disk are installed in sequence, and the data processing module adjusts the output pressure according to the input pressure. A pressure sensor is designed inside the leveler, which can collect the pressure of the contact between the leveler and the grinding pad in different zones, and calculate the pressure that needs to be compensated for each zone. Decompression compensation is performed for areas with small contact pressure to reduce the groove consumption rate of the zone, and pressure increase compensation is performed for areas with large contact pressure to increase the groove consumption rate of the zone. Adjusting the zone pressure of the leveler can improve the uneven consumption of the grooves on the grinding pad and make the groove height on the surface of the grinding pad tend to be uniform.

[0017] The pressure sensor is a flexible pressure sensor, which includes a plurality of detection units, which are evenly distributed on the surface of the flattening plate in an array. The detection units are evenly distributed in an array to monitor the uniformity of the output pressure of the flattener.

[0018] The grooves on the surface of the polishing pad are distributed in concentric rings, rectangles or irregular shapes, so that each of the partitions corresponds to a part of the grooves. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the specific embodiments of the present invention, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 is a partial structural schematic diagram of a chemical mechanical polishing device provided by an embodiment of the present invention;

[0021] Figure 2 is a schematic structural diagram of a leveler provided in an embodiment of the present invention;

[0022] Figure 3 is a schematic diagram of the distribution of detection units on a flat plate provided by an embodiment of the present invention;

[0023] Figure 4 It is a schematic diagram of the effect of the polishing pad being improved after normal consumption by the present invention.

[0024] Figure numerals: 1-polishing pad; 100-groove; 2-leveler; 21-leveling arm; 22-leveling disk; 23-cylinder; 24-pressure sensor; 240-detection unit. DETAILED DESCRIPTION

[0025] The technical solutions in the specific embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] It should be noted that, in order to describe the technical solution more specifically, the steps described in the following embodiments do not strictly correspond to the steps described in the content of the invention.

[0027] Example

[0028] Provided are a chemical mechanical polishing device and a method for improving the leveling effect of a polishing pad.

[0029] A chemical mechanical polishing device, reference Figures 1 to 3, including a grinding pad 1 and a grinding head (not shown) arranged on the grinding pad 1 and a leveler 2, the leveler 2 includes a leveling arm 21, a leveling disk 22 and a pressure control system, the pressure control system includes a cylinder 23, a pressure sensor 24 and a data processing module, the leveling arm 21, the cylinder 23, the pressure sensor 24 and the leveling disk 22 are installed in sequence, the cylinder 23 is installed between the leveling arm 21 and the leveling disk 22 and changes the output pressure of the leveler 2 through the stroke (after the leveler 2 is installed, a special measuring tool is used to calibrate the output pressure, and the output pressure is adjusted by adjusting the pressure of the cylinder 23). The pressure sensor 24 is a flexible pressure sensor, and the flexible pressure sensor includes a plurality of detection units 240, and the plurality of detection units 240 are evenly distributed on the surface of the leveling disk 22 in an array. The flexible pressure sensor is more in line with the requirements of surface partition pressure detection of the groove 100 of the grinding pad 1, and can also withstand certain deformation. The detection units 240 are evenly distributed in an array to monitor the uniformity of the output pressure of the leveler 2. The surface of the grinding pad 1 is divided into n partitions along the swing trajectory of the leveler 2, where n is a positive integer greater than 1. The output pressure of the leveler 2 in any one or more of the partitions is adjusted using one of the following methods for improving the leveling effect of the grinding pad. Specifically, whether the output pressure is adjusted in one partition, multiple partitions or all partitions can be determined based on actual needs.

[0030] A method for improving the leveling effect of the grinding pad, reference Figure 1 , including dividing the surface of the polishing pad 1 into n partitions along the swing track of the leveler 2, where n is a positive integer greater than 1. In this embodiment, n=10, and the surface of the polishing pad 1 is evenly divided into 10 partitions along the swing track of the leveler 2. The pattern of the partitions is an annular area distributed around the center of the polishing pad 1. The more partitions are divided, the more accurate the adjustment result tends to be, and the loss of the polishing pad 1 is further reduced. Theoretically, with the iteration of cylinder technology, it can be infinitely evenly divided. The surface of the polishing pad 1 is provided with grooves 100, reference Figure 4 The a in the figure shows the cross section of the polishing pad 1 and the groove 100. The groove 100 is distributed on the surface of the polishing pad 1 in the shape of concentric rings, rectangles or irregular shapes (the top view of the groove 100 on the surface of the polishing pad 1 is not shown), so that each of the partitions corresponds to a part of the groove 100. The function of the groove 100 on the surface of the polishing pad 1 is to transport the polishing liquid and discharge the polishing by-products. For how to determine the partition, you can also refer to Figure 1 , the arrow shows the swing track / path of the leveler 2, and the area where the arrow is located is divided into 10 equal partitions ( Figure 1 The dot-dash lines in the figure indicate the division method), when the polishing pad 1 rotates, each partition constitutes an annular area distributed around the center of the polishing pad 1 (not shown).

[0031] The pressure detected by the flexible pressure sensor can be collected in different zones according to the requirements, and the zone pressure, i.e., the input pressure, received by the surface of the leveling disk 22 on the leveler 2 in the i-th zone is detected respectively, and the output pressure of the leveler 2 in the i-th zone is adjusted according to the following formula, where i∈[1,10]:

[0032] Corrected output pressure D of the i-th partition i = Initial set pressure A + compensation pressure C of the ith zone i ;

[0033] Among them, K is the compensation coefficient, the value range of K is 0.1-1.0, b i is the partition pressure generated by the i-th partition on the polishing pad 1 on the surface of the flattening disk 22, B is the average pressure obtained by adding up and averaging the zone pressures generated by each zone on the surface of the flattening disk 22 .

[0034] It includes a monitoring process and an adjustment process. The monitoring process is to obtain the partition pressure obtained by the leveler 2 after passing through each partition. The adjustment process is to adjust the output pressure of the leveler 2 when the leveler 2 passes through each partition (determine whether to adjust the output pressure of one partition, multiple partitions or all partitions according to actual needs); the monitoring process and the adjustment process are performed once or repeatedly. If a period of grinding and leveling is continued after a single adjustment, the difference in the partition pressure between the partitions obtained in the second monitoring process is small and no adjustment is required. If a significant change occurs again, it can be adjusted again. The adjustment process can be performed if one of the following situations is met: when the deviation value between the initial set pressure A and the pressure of a single partition is higher than the preset value, or when the deviation value between the initial set pressure A and the pressure of multiple partitions is higher than the preset value, or when the deviation value between the initial set pressure A and the average pressure B is higher than the preset value; the preset value, the initial set pressure A and the compensation coefficient K are all determined by the process requirements.

[0035] The data processing module adjusts the output pressure according to the input pressure. The corrected output pressure D of the i-th partition i The method of obtaining the pressure is as follows: the flexible pressure sensor continuously or intermittently detects the partition pressure generated by each partition on the surface of the flattening plate 22, calculates the partition pressures of the 10 partitions to obtain the average pressure B, and finally obtains the compensation pressure C of the i-th partition. i and the corrected output pressure D of the i-th partition i .

[0036] In this embodiment, the initial setting pressure A=9N, the compensation coefficient K=0.8 (the compensation coefficient K is set by the engineer, and the upper and lower limits of the compensation pressure can be set according to actual conditions). The initial setting pressure A, partition pressure, average pressure B, compensation pressure and corrected output pressure of each partition are shown in Table 1.

[0037] Table 1 Pressure setting and adjustment parameters for each partition

[0038]

[0039] As can be seen from Table 1, the 10 partitions respectively obtain the corresponding corrected output pressures. In this embodiment, the output pressure of the cylinder 23 of the leveler 2 is adjusted in each partition. For example, the output pressure of the first partition is adjusted to 9.14N, which is 0.14N higher than the initial set pressure A, so that the groove 100 on the partition is subjected to greater pressure, and the consumption of the groove 100 increases. The output pressure of the fifth partition is adjusted to 8.82N, which is 0.18N lower than the initial set pressure A, so that the groove 100 on the partition is subjected to less pressure, and the consumption of the groove 100 is reduced. Finally, the height / depth of the groove 100 on the surface of the polishing pad 1 is close, and the consumption of the groove 100 is relatively uniform, thereby meeting the requirements of the leveling effect.

[0040] The adjustment process is performed after the grinding of an integer number of wafers is completed. The output pressure is adjusted because there is a large deviation between the detected input pressure and the set output pressure. This deviation needs to be adjusted accurately after accumulating a certain amount of data. Therefore, the adjustment can be performed after grinding several wafers. In addition, non-integer wafers mean that the wafers are not yet completed. At this time, correcting the output pressure will affect the leveling effect.

[0041] Figure 4 The middle dotted line indicates the center line of the polishing pad 1. A relatively large arrow indicates a relatively large output pressure, and a relatively small arrow indicates a relatively small output pressure. Taking the right side of the dotted line as an example (because the polishing pad 1 is rotated by a turntable, the left and right sides of the cross-sectional view are similarly symmetrical), the area where each raised part groove 100 is located can be roughly understood as a partition. In fact, it is not completely one-to-one corresponding, and it needs to correspond according to the actual partition situation. Figure 4 The initial state of the polishing pad 1 is to use the same pressure (initial setting pressure A) to level the polishing pad 1 (see Figure 4 a), after several wafers are polished and leveled, the groove 100 is not uniformly consumed (see Figure 4 b), when grinding and leveling the next wafer, the leveling pressure at the excessive consumption point can be reduced according to the above method (see Figure 4 c), pressure compensation can reduce the wear of excessive consumption and improve the uniformity of the groove 100 (see Figure 4 d). The present invention belongs to the field of chemical mechanical polishing process, and specifically relates to the consumption problem of the groove 100 of the polishing pad 1. A pressure sensor 24 is designed inside the leveler 2, which can collect the pressure of the contact between the leveler 2 and the polishing pad 1 in different zones, and calculate the pressure that needs to be compensated for each zone. Decompression compensation is performed for the area with small contact pressure to reduce the consumption rate of the groove 100 in the zone, and pressure increase compensation is performed for the area with large contact pressure to increase the consumption rate of the groove 100 in the zone. Adjusting the zone pressure of the leveler 2 can improve the uneven consumption of the groove 100 on the polishing pad 1, so that the height of the groove 100 on the surface of the polishing pad 1 tends to be uniform.

[0042] In terms of detection mechanism, the present invention only needs to detect the pressure change of the leveler 2, and does not require other complex detection instruments or detection methods such as detecting the specific contour of the grinding pad 1. In terms of feedback control logic, the feedback control logic of the present invention is to compensate the pressure of the leveler 2 after detecting the pressure change of the leveler 2. It is the feedback of the independent system of the leveler 2, rather than complex comprehensive feedback between mechanisms. Moreover, compared with other existing technologies, most of them belong to post-regulation, that is, the adjustment is started only after the contour of the grinding pad 1 has obvious changes. While detecting the pressure, the present invention can also realize the synchronous correction of the difference between the set output pressure and the actual pressure (the actual pressure is obtained according to the feedback of the detected input pressure), which can effectively avoid the obvious contour variation of the grinding pad 1, and belongs to a pre-regulation method.

[0043] The above embodiments are only used to help understand the method and core idea of ​​the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A method for improving the leveling effect of a polishing pad, characterized in that: The method comprises dividing the surface of the grinding pad (1) into n partitions along the swing trajectory of the leveler (2), where n is a positive integer greater than 1, respectively detecting the partition pressure, i.e., the input pressure, exerted on the surface of the leveling disk (22) on the leveler (2) in the i-th partition, and adjusting the output pressure of the leveler (2) in the i-th partition according to the following formula, where i∈[1,n]: Corrected output pressure D of the i-th partition i = Initial set pressure A + compensation pressure C of the ith zone i ; Among them, K is the compensation coefficient, the value range of K is 0.1-1.0, b i is the partition pressure generated by the i-th partition on the polishing pad (1) on the surface of the flattening disk (22); B is the average pressure obtained by adding up and averaging the zone pressures generated by each zone on the surface of the flattening plate (22).

2. The method for improving the leveling effect of the polishing pad according to claim 1, characterized in that: The corrected output pressure D of the i-th partition i The method for obtaining the pressure is as follows: the flexible pressure sensor continuously or intermittently detects the partition pressure generated by each partition on the surface of the flat plate (22), calculates the partition pressures of the obtained n partitions to obtain the average pressure B, and finally obtains the compensation pressure C of the i-th partition i and the corrected output pressure D of the i-th partition i .

3. The method for improving the leveling effect of the polishing pad according to claim 2, characterized in that: n=10, the surface of the polishing pad (1) is evenly divided into 10 partitions along the swing trajectory of the leveler (2), and the pattern of the partitions is an annular area distributed around the center of the polishing pad (1); a plurality of detection units (240) of the flexible pressure sensor are evenly distributed in an array on the surface of the leveling disk (22).

4. The method for improving the leveling effect of a polishing pad according to claim 1, characterized in that: The method comprises a monitoring process and an adjustment process. The monitoring process is to obtain the partition pressure obtained when the smoother (2) passes through each partition. The adjustment process is to adjust the output pressure of the smoother (2) when the smoother (2) passes through each partition. The monitoring process and the adjustment process are performed once or repeatedly.

5. The method for improving the leveling effect of the polishing pad according to claim 4, characterized in that: The adjustment process can be performed when any of the following conditions is met: when the deviation value between the initial set pressure A and a single or multiple partition pressures is higher than a preset value, or when the deviation value between the initial set pressure A and the average pressure B is higher than a preset value; the preset value, the initial set pressure A and the compensation coefficient K are all determined by process requirements.

6. The method for improving the leveling effect of a polishing pad according to claim 4, characterized in that: The adjustment process is performed after the grinding of the integer number of wafers is completed.

7. A chemical mechanical polishing device, characterized in that: The invention comprises a polishing pad (1) and a polishing head and a leveler (2) arranged on the polishing pad (1), and the output pressure of the leveler (2) in any one or more of the partitions is adjusted by using a method for improving the leveling effect of the polishing pad as described in any one of claims 1 to 6.

8. The chemical mechanical polishing device according to claim 7, characterized in that: The leveler (2) comprises a leveling arm (21), a leveling plate (22) and a pressure control system, wherein the pressure control system comprises a cylinder (23), a pressure sensor (24) and a data processing module, wherein the leveling arm (21), the cylinder (23), the pressure sensor (24) and the leveling plate (22) are installed in sequence, and the data processing module adjusts the output pressure according to the input pressure.

9. The chemical mechanical polishing device according to claim 8, characterized in that: The pressure sensor (24) is a flexible pressure sensor, and the flexible pressure sensor comprises a plurality of detection units (240). The plurality of detection units (240) are evenly and densely distributed in an array on the surface of the flattening plate (22).

10. The chemical mechanical polishing device according to claim 7, characterized in that: The grooves (100) on the surface of the polishing pad (1) are distributed in the shape of concentric rings, rectangles or irregular shapes, so that each of the partitions corresponds to a portion of the grooves (100).

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