Polishing condition determination device, single-sided polishing device, polishing condition determination method, and single-sided polishing method

Abstract

To provide a polishing condition determination device that can suppress variations in the amount of material removed during polishing. [Solution] The polishing condition determination device determines the polishing conditions when polishing a wafer, which is held on a polishing head via a back pad, using a polishing liquid supplied to the polishing pad through the gap between a retainer ring surrounding the wafer and the polishing pad, while pressing the wafer against the polishing pad. The device comprises an acquisition unit that acquires the cumulative usage time of the back pad and the cumulative usage time of the polishing pad, and a determination unit that determines the polishing conditions of the wafer based on the cumulative usage times of the back pad and the polishing pad.

Description

Technical Field

[0001] The present invention relates to a polishing condition determination device, a single-sided polishing device, a polishing condition determination method, and a single-sided polishing method.

Background Art

[0002] Conventionally, a control method for a single-sided polishing device that polishes a wafer has been known (see, for example, Patent Documents 1 and 2). The configuration of Patent Document 1 sets polishing conditions based on the cumulative usage time of a retainer ring, the cumulative usage time of a polishing pad, and the cumulative usage time of a conditioner that conditions the polishing pad. The configuration of Patent Document 2 changes the polishing conditions according to the amount of elongation in the vertical direction of a membrane.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, some single-sided polishing devices have a configuration in which a back pad for holding a wafer and a retainer ring for surrounding the periphery of the wafer are provided on a polishing head. In such a configuration, the wafer is pressed against the polishing pad by the elastic force of the back pad, and polishing liquid is supplied between the wafer and the polishing pad from the gap between the retainer ring and the polishing pad to polish the wafer. However, in the single-sided polishing device provided with the above-described back pad and retainer ring, the polishing cost per batch may vary.

[0005] The present invention aims to provide a polishing condition determination device, a single-sided polishing device, a polishing condition determination method, and a single-sided polishing method that can suppress variations in the amount of material removed during polishing. [Means for solving the problem]

[0006] The polishing condition determination apparatus of the present invention determines the polishing conditions when polishing a wafer, which is held on a polishing head via a back pad, using a polishing liquid supplied to the polishing pad through the gap between a retainer ring surrounding the wafer and the polishing pad, while pressing the wafer against the polishing pad. The apparatus comprises an acquisition unit that acquires the cumulative usage time of the back pad and the cumulative usage time of the polishing pad, and a determination unit that determines the polishing conditions of the wafer based on the cumulative usage times of the back pad and the polishing pad.

[0007] In the polishing condition determination device of the present invention, it is preferable that the determination unit determines the polishing time as the polishing condition based on a correlation in which the amount of material removed per unit time decreases as the cumulative usage time of the back pad increases, and a correlation in which the amount of material removed per unit time increases as the cumulative usage time of the polishing pad increases.

[0008] In the polishing condition determination device of the present invention, it is preferable that the determination unit determines the polishing time based on the following formula (1). T1=A+Bb×Tb+Cb+Bp×Tp+Cp … (1) T: Polishing time (seconds) Tb: The cumulative usage time (seconds) of the back pad. Tp: The cumulative usage time (seconds) of the polishing pad. A: Base time (seconds) obtained by performing a linear regression analysis on the actual values ​​of single-sided polishing of the wafer. Bb: A coefficient corresponding to the back pad obtained by performing a linear regression analysis on the actual values ​​of single-sided polishing of the wafer. Cb: Adjustment time (seconds) corresponding to the back pad, obtained by performing a linear regression analysis on the actual values ​​of single-sided polishing of the wafer. Bp: A coefficient corresponding to the polishing pad obtained by performing a linear regression analysis on the actual values ​​of single-sided polishing of the wafer. Cp: ​​The adjustment time (seconds) corresponding to the polishing pad, obtained by performing a linear regression analysis on the actual values ​​of single-sided polishing of the wafer.

[0009] In the polishing condition determination apparatus of the present invention, it is preferable that the acquisition unit acquires the thickness of the wafer before polishing, and the determination unit determines the polishing conditions for the wafer based on the cumulative usage time of the back pad and the polishing pad and the thickness of the wafer before polishing.

[0010] In the polishing condition determination apparatus of the present invention, it is preferable that the acquisition unit acquires target values ​​for the flatness of the wafer before polishing and the flatness after polishing, and the determination unit determines the polishing conditions for the wafer based on the cumulative usage time of the back pad and the polishing pad, the thickness of the wafer before polishing, and the target values ​​for the flatness before polishing and the flatness after polishing.

[0011] In the polishing condition determination apparatus of the present invention, it is preferable that the acquisition unit acquires target values ​​for the flatness of the wafer before polishing and the flatness after polishing, and the determination unit determines the polishing conditions for the wafer based on the cumulative usage time of the back pad and the polishing pad, and the target values ​​for the flatness of the wafer before polishing and the flatness after polishing.

[0012] The single-sided polishing apparatus of the present invention comprises a polishing processing unit that polishes a wafer held by a polishing head via a back pad, using a polishing liquid supplied to the polishing pad through the gap between a retainer ring surrounding the wafer and the polishing pad, while pressing the wafer against the polishing pad; a polishing condition determination unit that determines the polishing conditions when polishing the wafer in the polishing processing unit; and a polishing control unit that controls the polishing processing unit based on the polishing conditions determined by the polishing condition determination unit.

[0013] The present invention provides a method for determining polishing conditions, which involves pressing a wafer held by a polishing head via a back pad against a polishing pad, and using a polishing liquid supplied to the polishing pad through a gap between a retainer ring surrounding the wafer and the polishing pad to determine the polishing conditions when polishing the wafer. The method involves obtaining the cumulative usage time of the back pad and the cumulative usage time of the polishing pad, and determining the polishing conditions of the wafer based on the cumulative usage times of the back pad and the polishing pad.

[0014] In the polishing condition determination method of the present invention, it is preferable to determine the polishing time as a polishing condition based on a correlation between the amount of material removed per unit time decreasing as the cumulative usage time of the back pad increases, and a correlation between the amount of material removed per unit time increasing as the cumulative usage time of the polishing pad increases.

[0015] In the polishing condition determination method of the present invention, it is preferable to determine the polishing time based on the following formula (1). T1=A+Bb×Tb+Cb+Bp×Tp+Cp … (1) T: Polishing time (seconds) Tb: The cumulative usage time (seconds) of the back pad. Tp: The cumulative usage time (seconds) of the polishing pad. A: Base time (seconds) obtained by performing a linear regression analysis on the actual values ​​of single-sided polishing of the wafer. Bb: A coefficient corresponding to the back pad obtained by performing a linear regression analysis on the actual values ​​of single-sided polishing of the wafer. Cb: Adjustment time (seconds) corresponding to the back pad, obtained by performing a linear regression analysis on the actual values ​​of single-sided polishing of the wafer. Bp: A coefficient corresponding to the polishing pad obtained by performing a linear regression analysis on the actual values ​​of single-sided polishing of the wafer. Cp: ​​The adjustment time (seconds) corresponding to the polishing pad, obtained by performing a linear regression analysis on the actual values ​​of single-sided polishing of the wafer.

[0016] In the method for determining polishing conditions of the present invention, it is further preferable to obtain the thickness of the wafer before polishing, and determine the polishing conditions of the wafer based on the cumulative usage times of the back pad and the polishing pad, and the thickness of the wafer before polishing.

[0017] In the method for determining polishing conditions of the present invention, it is further preferable to obtain the target values of the flatness of the wafer before polishing and after polishing, and determine the polishing conditions of the wafer based on the cumulative usage times of the back pad and the polishing pad, the thickness of the wafer before polishing, and the target values of the flatness of the wafer before polishing and after polishing.

[0018] In the method for determining polishing conditions of the present invention, it is further preferable to obtain the target values of the flatness of the wafer before polishing and after polishing, and determine the polishing conditions of the wafer based on the cumulative usage times of the back pad and the polishing pad, and the target values of the flatness of the wafer before polishing and after polishing.

[0019] The single-sided polishing method of the present invention determines the polishing conditions by the above-described method for determining polishing conditions, and polishes the wafer based on the polishing conditions.

Brief Description of the Drawings

[0020] [Figure 1] It is a plan view showing the whole single-sided polishing apparatus according to the prior art and the first and second embodiments. [Figure 2] It is a schematic view showing a schematic configuration of a rough polishing section according to the prior art and the first and second embodiments. [Figure 3] The results of experiments conducted to lead to the present invention are shown. (A) is a graph showing the correlation between the cumulative usage time ratio of the back pad and the polishing rate, and (B) is a graph showing the correlation between the cumulative usage time ratio of the polishing pad and the polishing rate. [Figure 4] It is a block diagram of a control device constituting a single-sided polishing apparatus according to the first and second embodiments. [Figure 5]This is a flowchart of the rough polishing step included in the single-sided polishing method according to the first embodiment. [Figure 6] This is a flowchart of the rough polishing step included in the single-sided polishing method according to the second embodiment. [Figure 7] This is a box plot showing the thickness measurement results of the polysilicon film after polishing according to the example. [Modes for carrying out the invention]

[0021] [Prerequisite technology] First, before describing embodiments of the present invention, we will describe the prerequisite technologies used in those embodiments. Figure 1 is a plan view showing the entire single-sided polishing apparatus. Figure 2 is a schematic diagram showing the general configuration of the rough polishing section. The single-sided polishing apparatus 1 shown in Figure 1 polishes a wafer W in multiple stages. The polishing process performed by the single-sided polishing apparatus 1 includes a rough polishing step, a first finishing polishing step that polishes to a finer roughness than the rough polishing step, and a second finishing polishing step that polishes to a finer roughness than the first finishing polishing step. The wafer W may be a bare wafer Wb without any films formed on it, or it may be a film-coated wafer Wa, for example, with a polysilicon film formed on the surface to be polished W1. The single-sided polishing apparatus 1 comprises a polishing processing unit 2 and a control device 9.

[0022] The polishing processing unit 2 comprises a cleaning unit 3, a polishing unit 4, a unit transport unit 5, and four holding units 6.

[0023] The unpolished wafer W is placed in the cleaning unit 3. This unpolished wafer W is held by the holding unit 6 and polished by the polishing unit 4. The polished wafer W is placed in the cleaning unit 3 by the holding unit 6. This polished wafer W is transported to the outside as appropriate. Furthermore, the polishing head 61 of the holding unit 6 located above the cleaning unit 3 is cleaned as appropriate.

[0024] The polishing section 4 comprises a rough polishing section 41, a first finishing polishing section 42, and a second finishing polishing section 43. The cleaning section 3, the rough polishing section 41, the first finishing polishing section 42, and the second finishing polishing section 43 are positioned below four holding sections 6 supported by the unit transport section 5. Since the rough polishing section 41, the first finishing polishing section 42, and the second finishing polishing section 43 have similar configurations, the rough polishing section 41 will be described in detail, while the descriptions of the first finishing polishing section 42 and the second finishing polishing section 43 will be simplified.

[0025] The rough polishing unit 41 performs a rough polishing process on the wafer W transported from the cleaning unit 3. As shown in Figure 1 or Figure 2, the rough polishing unit 41 includes a platen drive unit 411, a platen 412, and a polishing fluid supply unit 413. The platen drive unit 411 rotates the platen 412 which is connected to the rotating shaft 411A of the platen drive unit 411. A polishing pad 414 for rough polishing is provided on the upper surface of the surface plate 412. The polishing pad 414 is sized to allow simultaneous polishing of the two wafers W held by each holding unit 6. The polishing fluid supply unit 413 supplies a slurry-like polishing fluid for coarse polishing to the polishing pad 414.

[0026] The first finishing polishing unit 42 performs a first finishing polishing process on the wafer W that has undergone a rough polishing process. The first finishing polishing unit 42 comprises a platen 422 and a polishing pad 424 for the first finishing polishing, as shown in Figure 1, and a platen drive unit and a polishing fluid supply unit, which are not shown. The polishing fluid supply unit supplies a slurry-like polishing fluid for the first finishing polishing to the polishing pad 424.

[0027] The second finishing polishing unit 43 performs a second finishing polishing process on the wafer W that has undergone the first finishing polishing process. The second finishing polishing unit 43 comprises a platen 432 and a polishing pad 434 for the second finishing polishing, as shown in Figure 1, and a platen drive unit and a polishing fluid supply unit, respectively (not shown). The polishing fluid supply unit supplies a slurry-like polishing fluid for the second finishing polishing to the polishing pad 434.

[0028] The unit transport unit 5 supports four holding units 6 and sequentially transports each holding unit 6 to the cleaning unit 3, the rough polishing unit 41, the first finishing polishing unit 42, and the second finishing polishing unit 43. The unit transport unit 5 includes a support body 51 that supports each holding unit 6, and a support body drive unit 52 that rotates or raises the support body 51. The support body 51 comprises four main arms 511 arranged in a cross shape in plan view. Each main arm 511 has a sub-arm 512 at its tip that is perpendicular to the main arm 511 in plan view. The support body drive unit 52 comprises a rotating shaft 521 fixed to the center of the support body 51.

[0029] Each holding unit 6 is equipped with two polishing units 60, each provided on both ends of each sub-arm 512. Each polishing unit 60 is equipped with a disc-shaped polishing head 61. Each polishing head 61 holds the wafer W. Note that each holding unit 6 may be equipped with one polishing unit 60, or three or more.

[0030] Each polishing head 61 holds the wafer W opposite the surface to be polished W1 (front surface) (back surface) due to the surface tension of water or the like. A back pad 62 is positioned on the underside of the polishing head 61 so as to cover the entire underside. The back pad 62 is made of, for example, a porous resin material and can contain a liquid such as water. A ring-shaped retainer ring 63 is positioned on the outer periphery of the lower surface of the back pad 62. The retainer ring 63 contacts the outer edge of the wafer W located inside the retainer ring 63, and holds the wafer W so that it does not come out of the gap between the back pad 62 and the polishing pads 414, 424, 434.

[0031] Each polishing unit 60 further comprises a head drive unit 64 and a wafer pressure adjustment unit 65. Each head drive unit 64 is located inside the sub-arm 512 and rotates the polishing head 61, which is connected to the rotation axis of the head drive unit 64 via a head rotation axis member 641, in the same direction as or opposite to the rotation direction of the surface plates 412, 422, and 432. Each wafer pressure adjustment unit 65 is a fixed-pressure type device located inside the sub-arm 512, and adjusts the pressure (hereinafter sometimes referred to as "polishing pressure") that presses each wafer W against the polishing pads 414, 424, and 434. In the fixed-pressure type, the entire polishing head 61 is pushed down by cylinder pressure, and the polishing head 61 is pressed against the upper surface of the wafer W via the back pad 62, thereby pressing the polishing surface W1 of the wafer W against the polishing pads 414, 424, and 434.

[0032] In the rough polishing section 41, the rotational drive unit is composed of a combination of a platen drive unit 411 and a head drive unit 64. In the first and second finishing polishing sections 42 and 43, the rotational drive unit is composed of a combination of a platen drive unit (not shown) and a head drive unit 64, respectively.

[0033] The control device 9 controls the polishing processing unit 2 based on polishing conditions set using an input unit (not shown) to perform a rough polishing step, a first finish polishing step, and a second finish polishing step on the wafer W.

[0034] [Background leading to the present invention] Next, I will explain the circumstances that led to the present invention. Figure 3 shows the results of experiments conducted to derive the present invention, where (A) is a graph showing the correlation between the cumulative usage time percentage of the back pad and the polishing rate, and (B) is a graph showing the correlation between the cumulative usage time percentage of the polishing pad and the polishing rate. The inventors of the present invention encountered a problem in the rough polishing process when performing the rough polishing process on wafers Wa with the same specifications, setting the polishing time, the rotation speed of the surface platen 412 and the polishing head 61 (hereinafter sometimes referred to as "polishing rotation speed"), the polishing pressure, and the amount of polishing fluid supplied to the same values. As the number of polishing batches increased, the amount of material removed by polishing became inconsistent. Therefore, after conducting extensive research, the inventors concluded that changes in the properties of the back pad 62 and the polishing pad 414 may be a factor in the variation in the amount of material removed during polishing, and conducted the following Experiment 1.

[0035] In Experiment 1, we first created multiple wafers Wa with the same specifications and measured the thickness of each wafer Wa. Using a single-sided polishing apparatus 1, the polishing time, polishing rotation speed, polishing pressure, and polishing fluid supply amount were set to the same values ​​for each coated wafer Wa, and only the rough polishing process was performed for multiple batches. In this rough polishing process, the polysilicon film was polished on the coated wafer Wa, which had a polysilicon film applied to the polishing surface W1 of the wafer W.

[0036] In the rough polishing process of multiple batches, the back pad 62 and polishing pad 414 were replaced with new ones at predetermined intervals. In Experiment 1, the back pad 62 was replaced with a new one when its cumulative usage time reached a predetermined percentage. The cumulative usage time percentage of the back pad 62 is obtained by dividing the cumulative usage time of the back pad 62 by the upper limit of the cumulative usage time of the back pad 62 (the time set as the lifespan of the back pad 62). In Experiment 1, the polishing pad 414 was replaced with a new one when its cumulative usage time reached a predetermined percentage. Polishing pad 414 Cumulative usage time percentage This is obtained by dividing the cumulative usage time of the polishing pad 414 by the upper limit of the cumulative usage time of the polishing pad 414 (the time set as the lifespan of the polishing pad 414). 。 During the rough polishing process for multiple batches, the back pad 62 and polishing pad 414 were replaced with new ones at least once each.

[0037] The amount of material removed by polishing a film-coated wafer Wa was measured, and the correlation between the cumulative usage time percentage of the back pad 62 and the polishing rate was confirmed. Polishing amount represents the amount removed from the object being polished by polishing, and in this case, it represents the change in thickness (mm) before and after polishing. Polishing rate is the amount of material removed (mm) per unit time (1 second). As shown in Figure 3(A), we were able to confirm a correlation in which the polishing rate decreases as the cumulative usage time of the back pad 62 increases, that is, as the cumulative usage time of the back pad 62 increases. The inventors hypothesized the following reason for obtaining the correlation shown in Figure 3(A). As the cumulative usage time of the back pad 62 increases, the compressive modulus of the back pad 62 decreases. When the compressive modulus of the back pad 62 decreases, the distance Q from the lower surface of the retainer ring 63 to the polishing surface W1 of the film-coated wafer Wa (hereinafter sometimes referred to as "the amount of protrusion Q of the film-coated wafer Wa") decreases. When the amount of protrusion Q decreases, the polishing liquid flows more easily into the gap between the film-coated wafer Wa and the polishing pad 414. It was hypothesized that when the polishing liquid flows more easily into the gap, the temperature of the film-coated wafer Wa during polishing decreases, and the polishing rate decreases.

[0038] Furthermore, the correlation between the cumulative usage time percentage of the polishing pad 414 and the polishing rate was confirmed. As shown in Figure 3(B), we were able to confirm a correlation where the polishing rate increases as the cumulative usage time of the polishing pad 414 increases, that is, as the cumulative usage time of the polishing pad 414 increases. The inventors speculated that the reason for obtaining the correlation shown in Figure 3(B) is as follows: As the cumulative usage time of the polishing pad 414 increases, the abrasive particles contained in the polishing fluid are more easily retained on the polishing pad 414. It was hypothesized that as the abrasive particles are more easily retained on the polishing pad 414, the polishing rate will increase.

[0039] As shown in Figures 3(A) and 3(B), the correlation between the cumulative usage time of the back pad 62 and the polishing rate is inverse, as is the correlation between the cumulative usage time of the polishing pad 414 and the polishing rate. Due to this inverse correlation, we hypothesized that when performing a rough polishing process on a film-coated wafer Wa of the same specifications under the same polishing conditions (same polishing time, polishing rotation speed, polishing pressure, and polishing fluid supply), the amount of material removed by polishing will vary as the number of polishing batches increases. Furthermore, we hypothesized that this inverse correlation is the same when performing a first or second finish polishing process on a film-coated wafer Wa, or when performing a rough polishing process, a first finish polishing process, or a second finish polishing process on a bare wafer Wb. Based on the above inferences, the inventors have found that variations in the amount of material removed by polishing can be suppressed by determining the polishing conditions of the wafer W according to the cumulative usage time of the back pad 62 and the polishing pad 414, and have completed the present invention.

[0040] Furthermore, the inventors performed a linear regression analysis on the correlations shown in Figures 3(A) and 3(B), using the cumulative usage time of the back pad 62 and the polishing pad 414, and the polishing rate of each film-coated wafer Wa as explanatory variables, and the polishing time as the dependent variable. As a result, the following equation (1) was obtained as the formula for calculating the polishing time required to bring the polishing allowance of the film-coated wafer Wa to a target value. T1=A+Bb×Tb+Cb+Bp×Tp+Cp … (1) T1: Polishing time (seconds) Tb: Cumulative usage time (seconds) of backpad 62 Tp: Cumulative usage time of polishing pad 414 (seconds) A: Base time (seconds) obtained by performing linear regression analysis on actual data for single-sided wafer polishing. Bb: Coefficient corresponding to backpad 62 obtained by performing linear regression analysis on the actual values ​​of single-sided wafer polishing. Cb: Adjustment time (seconds) corresponding to the back pad 62, obtained by performing a linear regression analysis on the actual values ​​of single-sided wafer polishing. Bp: A coefficient corresponding to the polishing pad 414 obtained by performing a linear regression analysis on the actual values ​​of single-sided wafer polishing. Cp: ​​Adjustment time (seconds) corresponding to polishing pad 414, obtained by performing a linear regression analysis on the actual values ​​of single-sided wafer polishing.

[0041] Furthermore, the inventors have found that, in calculating the polishing time, in addition to the cumulative usage time of the back pad 62 and the polishing pad 414, variables such as the amount of protrusion Q of the film-coated wafer Wa at the start of polishing, the value of ESFQD (Edge Site flatness Front reference least sQuare Deviation) of the film-coated wafer Wa before polishing, and the target value of ESFQD may also be used. ESFQD is an index that represents the flatness of the film-coated wafer Wa. ESFQD is an index that indicates site flatness at the outer edge of a wafer W. ESFQD is measured using a flatness measuring device (e.g., KLA-Tencor: Wafer sight 2). ESFQD is the maximum displacement amount excluding the sign from the site plane calculated using the least squares method, based on the site plane obtained by dividing the outer edge of the wafer W into a large number of sector-shaped regions (sites) (e.g., 72). Each site has one data point.

[0042] Assuming that the protrusion amount Q at the start of polishing, the ESFQD value of the film-coated wafer Wa before polishing, and the amount of adjustment for polishing time based on the target value of ESFQD are linearly correlated with each other, the following equation (2) is obtained as the formula for calculating the polishing time required to bring the polishing allowance of the film-coated wafer Wa to the target value. T2 = A + Bb × Tb + Cb + Bp × Tp + Cp +Bq×(DE)+Cq+Be×F+Ce+Bt×G+Ct … (2) T2: Polishing time (seconds) Bq: A coefficient corresponding to the protrusion amount Q, obtained by performing a linear regression analysis on the actual values ​​of single-sided wafer polishing. D: Wafer thickness before polishing (mm) E: Thickness of retainer ring 63 (mm) Cq: Adjustment time (seconds) corresponding to the protrusion amount Q, obtained by performing a linear regression analysis on the actual values ​​of single-sided wafer polishing. Be: A coefficient corresponding to the pre-polishing ESFQD obtained by performing linear regression analysis on the actual values ​​of single-sided wafer polishing. F: ESFQD before polishing Ce: Adjustment time (seconds) corresponding to the pre-polishing ESFQD, obtained by performing linear regression analysis on the actual values ​​of single-sided wafer polishing. Bt: A coefficient corresponding to the target value of ESFQD obtained by performing linear regression analysis on the actual values ​​of single-sided wafer polishing. G:ESFQD target value Ct: Adjustment time (seconds) corresponding to the target value of ESFQD, obtained by performing linear regression analysis on the actual values ​​of single-sided wafer polishing.

[0043] The base time A, coefficients Bb, Bp, Bq, Be, Bt, and adjustment times Cb, Cp, Cq, Ce, Ct in equation (2) can be determined, for example, by Experiment 2 below. First, create multiple wafers Wa with the same specifications and measure the thickness and ESFQD of each wafer Wa. Then, as in Experiment 1, the polishing time, polishing rotation speed, polishing pressure, and polishing fluid supply amount are set to the same values ​​for each film-coated wafer Wa, and only the rough polishing process is performed for multiple batches. In this rough polishing process for multiple batches, the back pad 62 is replaced with a new one when the cumulative usage time percentage of the back pad 62 reaches a predetermined percentage. The polishing pad 414 is replaced with a new one when the cumulative usage time percentage of the polishing pad 414 reaches a predetermined percentage.

[0044] Furthermore, when performing the rough polishing process for each batch, the order in which the rough polishing process is performed is set to be in order of increasing thickness of the coated wafers Wa. Then, the average value of the thickness of the coated wafers Wa in each batch before polishing is calculated as the thickness before polishing for each batch. The average value of the ESFQD before polishing for each batch is calculated as the ESFQD before polishing for each batch. Then, by performing a linear regression analysis with the cumulative usage time of the back pad 62 and polishing pad 414, the polishing rate, the thickness of the retainer ring 63, the target value of ESFQD, and the thickness and ESFQD of the film-coated wafer Wa before polishing as explanatory variables and the polishing time as the dependent variable, the base time A, coefficients Bb, Bp, Bq, Be, Bt, and adjustment times Cb, Cp, Cq, Ce, Ct can be determined. Note that the thickness of the retainer ring 63 and the thickness of the film-coated wafer Wa before polishing correspond to the protrusion amount Q.

[0045] In equation (2), without using the ESFQD value of the film-coated wafer Wa before polishing and the target value of ESFQD as variables, the following equation (3) can also be derived as a formula for calculating the polishing time required to bring the polishing allowance of the film-coated wafer Wa to the target value, based on the cumulative usage time of the back pad 62 and the polishing pad 414 and the thickness of the film-coated wafer Wa before polishing. T3 = A + Bb × Tb + Cb + Bp × Tp + Cp +Bq × (DE) + Cq … (3) T3: Polishing time (seconds) Furthermore, in equation (2), instead of using the protrusion amount Q at the start of polishing as a variable, the following equation (4) can be derived as a formula for calculating the polishing time required to bring the polishing allowance of the film-coated wafer Wa to the target value, based on the cumulative usage time of the back pad 62 and the polishing pad 414, and the target values ​​of the ESFQD as the flatness of the film-coated wafer Wa before polishing and the ESFQD after polishing. T4 = A + Bb × Tb + Cb + Bp × Tp + Cp +Be×F+Ce+Bt×G+Ct … (4) T4: Polishing time (seconds)

[0046] When performing a first or second finishing polishing process on a film-coated wafer Wa, or when performing a rough polishing process, a first finishing polishing process, or a second finishing polishing process on a bare wafer Wb, although the values ​​of base time A, coefficients Bb, Bp, Bq, Be, Bt, and adjustment times Cb, Cp, Cq, Ce, Ct differ from those corresponding to the rough polishing process on the film-coated wafer Wa, it can be inferred that polishing times T1, T2, T3, T4 can be calculated based on equations (1), (2), (3), and (4) to bring the polishing allowance of the film-coated wafer Wa or the bare wafer Wb to the target value.

[0047] [First Embodiment] Next, a first embodiment of the present invention will be described. <Configuration of a single-sided polishing device> First, the configuration of the single-sided polishing apparatus according to the first embodiment will be explained with reference to Figure 1. Figure 4 is a block diagram of the control device that constitutes the single-sided polishing machine.

[0048] As shown in Figure 1, the single-sided polishing apparatus 10 according to the first embodiment comprises a polishing processing unit 2 and a control device 11. As shown in Figure 4, the control device 11 includes an input unit 111, a display unit 112, a storage unit 113, and a control unit 114.

[0049] The input unit 111 is configured, for example, as a touch panel or physical buttons, and outputs a signal corresponding to the input operation to the control unit 114. The display unit 112 displays various information based on the control of the control unit 114. The storage unit 113 stores various information related to the polishing of the wafer W in a format readable by the control unit 114. The information related to the polishing of the wafer W includes formula (1), the cumulative usage time of the back pad 62 and the polishing pad 414 of the rough polishing unit 41. Formula (1) stored in the storage unit 113 is the formula corresponding to the film-coated wafer Wa or the bare wafer Wb to be polished.

[0050] The control unit 114 is equipped with a CPU, and various functions are realized by the CPU executing programs stored in the memory unit 113. The control unit 114 includes an acquisition unit 115, a determination unit 116, an update unit 117, and a polishing control unit 118. The acquisition unit 115, the determination unit 116, and the update unit 117 constitute a polishing condition determination device 12 that calculates the polishing time T1 to bring the polishing allowance of the wafer W in the rough polishing process to a target value based on formula (1).

[0051] The acquisition unit 115 acquires the cumulative usage time of the back pad 62 and the polishing pad 414 of the rough polishing unit 41, which are stored in the storage unit 113. The acquisition unit 115 may also acquire the cumulative usage time entered based on the operator's operation of the input unit 111.

[0052] The determination unit 116 calculates the polishing time T1 required to bring the polishing allowance of the wafer W to a target value, based on the cumulative usage time of the back pad 62 and polishing pad 414 acquired by the acquisition unit 115 and formula (1) stored in the storage unit 113.

[0053] The update unit 117 updates the cumulative usage time of the back pad 62 and polishing pad 414 stored in the memory unit 113. For example, if single-sided polishing is performed for the first time after the replacement of the back pad 62, the cumulative usage time of the back pad 62 stored in the memory unit 113 is 0 seconds. The setting of the cumulative usage time after the replacement of the back pad 62 may be performed, for example, based on the operation of the operator's input unit 111. When rough polishing is performed for a polishing time T1, the update unit 117 adds the polishing time T1 to the cumulative usage time of the back pad 62 and polishing pad 414 stored in the storage unit 113, and stores this time as a new cumulative usage time in the storage unit 113.

[0054] The polishing control unit 118 controls the rough polishing section 41 and the polishing unit 60 so that the rough polishing process is performed based on the polishing time T1 determined by the polishing condition determination device 12. The polishing control unit 118 also controls the first and second finishing polishing sections 42, 43 and the polishing unit 60 so that the first and second finishing polishing processes are performed under preset polishing conditions.

[0055] <Single side polishing method> Next, a single-sided polishing method using the single-sided polishing device 10 will be described. Figure 5 is a flowchart of the rough polishing process included in the single-sided polishing method.

[0056] First, the polishing control unit 118 controls the unit transport unit 5 and the polishing unit 60 to hold the wafer W before polishing with each polishing head 61 and move it above the polishing pad 414 of the rough polishing unit 41. The acquisition unit 115 acquires the cumulative usage time of the back pad 62 and the polishing pad 414 before, during, or after the wafer W is moved above the polishing pad 414, as shown in Figure 5 (step S1).

[0057] The determination unit 116 determines the polishing time T1 based on the cumulative usage time obtained in step S1 and equation (1) (step S2).

[0058] The polishing control unit 118 controls the rough polishing unit 41, the unit transport unit 5, and the polishing unit 60 to perform rough polishing for a polishing time T1 based on preset polishing conditions (step S3). The preset polishing conditions are the polishing conditions other than polishing time T1 that were used when deriving equation (1).

[0059] When the processing in step S3 is completed, the update unit 117 updates the cumulative usage time of the back pad 62 and polishing pad 414 stored in the storage unit 113 (step S4). The wafer W, which has undergone rough polishing, is then subjected to first and second finish polishing processes under pre-set polishing conditions.

[0060] <Effects of the First Embodiment> The control device 11 determines the polishing time T1 to bring the amount of material removed from the wafer W to a target value, based on the cumulative usage time of the back pad 62 and polishing pad 414, whose characteristics change as the number of polishing cycles increases. Therefore, by performing polishing for only a polishing time T1 based on polishing conditions other than the pre-set polishing time, variations in the amount of material removed during polishing from batch to batch can be suppressed. In particular, since the polishing time T1 is determined as a polishing condition based on the cumulative usage time of the back pad 62 and the polishing pad 414, it is possible to easily change the polishing conditions for each batch compared to when other polishing conditions such as polishing rotation speed and polishing pressure are determined.

[0061] [Second Embodiment] Next, a second embodiment of the present invention will be described. <Configuration of a single-sided polishing device> First, the configuration of the single-sided polishing apparatus according to the second embodiment will be described with reference to Figures 1 and 4.

[0062] As shown in Figure 1, the single-sided polishing apparatus 10A according to the second embodiment comprises a polishing processing unit 2, a thickness measuring unit 13 and a flatness measuring unit 14, indicated by dashed lines, and a control device 15.

[0063] The thickness measuring unit 13 measures the thickness of the wafer W using a well-known method and outputs the measurement result to the control device 15. The flatness measurement unit 14 measures the ESFQD of the wafer W and outputs the measurement result to the control device 15. As shown in Figure 4, the control device 15 differs from the control device 11 of the first embodiment in that it includes a control unit 154 instead of a control unit 114. The control unit 154 differs from the control unit 114 of the first embodiment in that it has different information regarding the polishing of the wafer W stored in the storage unit 113, and that it includes an acquisition unit 155 and a determination unit 156 instead of an acquisition unit 115 and a determination unit 116.

[0064] The information stored in the memory unit 113 regarding the polishing of wafer W includes formula (2), the cumulative usage time of the back pad 62 and the polishing pad 414 of the rough polishing unit 41, the thickness of the retainer ring 63, and the target value of ESFQD. Formula (2) stored in the memory unit 113 is the formula corresponding to the film-coated wafer Wa or the bare wafer Wb to be polished.

[0065] The acquisition unit 155, the determination unit 156, and the update unit 117 constitute a polishing condition determination device 16 that calculates the polishing time T2 to bring the polishing allowance of the wafer W in the rough polishing process to a target value based on formula (2).

[0066] The acquisition unit 155 acquires the cumulative usage time of the back pad 62 and the polishing pad 414 of the rough polishing unit 41, which are stored in the storage unit 113. The acquisition unit 155 acquires the thickness of the wafer W before polishing from the thickness measuring unit 13 for each batch. The acquisition unit 155 acquires the ESFQD of the wafer W before polishing from the flatness measuring unit 14 for each batch. The acquisition unit 115 may also acquire the cumulative usage time, the thickness of the wafer W before polishing, and the ESFQD, which are entered based on the operator's operation of the input unit 111.

[0067] Based on the information acquired by the acquisition unit 155, the determination unit 156 calculates the average value of the wafer W thickness before polishing and the average value of the ESFQD for each batch. Based on the cumulative usage time of the back pad 62 and polishing pad 414 acquired by the acquisition unit 155, the average values ​​of the wafer W thickness and ESFQD, the thickness of the retainer ring 63, the target value of the ESFQD, and formula (2) stored in the storage unit 113, the determination unit 156 calculates the polishing time T2 required to bring the polishing allowance of the wafer W to the target value.

[0068] <Single side polishing method> Next, we will explain a single-sided polishing method using the single-sided polishing device 10A. Figure 6 is a flowchart of the rough polishing process included in the single-sided polishing method. Processes similar to those in the first embodiment are denoted by the same reference numerals, and their explanations are simplified.

[0069] First, the polishing control unit 118 moves the wafer W before polishing above the polishing pad 414 of the rough polishing unit 41. The acquisition unit 155 acquires the thickness of each wafer W before, during, or after the wafer W is moved above the polishing pad 414, as shown in Figure 6 (step S11). The acquisition unit 155 acquires the ESFQD of each wafer W (step S12). The acquisition unit 155 acquires the cumulative usage time of the back pad 62 and the polishing pad 414 (step S1). The order in which the acquisition unit 155 performs steps S11, S12, and S1 is not particularly limited and does not have to be in the order shown in Figure 6.

[0070] The determination unit 156 determines the polishing time T2 based on the information obtained in steps S11, S12, and S1, and equation (2) (step S13).

[0071] The polishing control unit 118 performs rough polishing for a polishing time T2 based on preset polishing conditions (step S14). The preset polishing conditions are the polishing conditions other than polishing time T2 that were used when deriving equation (2).

[0072] When the processing in step S14 is completed, the update unit 117 updates the cumulative usage time of the back pad 62 and the polishing pad 414 (step S4). The wafer W, which has undergone rough polishing, is then subjected to first and second finish polishing processes under pre-set polishing conditions.

[0073] <Effects of the second embodiment> The control device 15 determines the polishing time T2 to bring the polishing allowance of the wafer W to the target value, based on the cumulative usage time of the back pad 62 and the polishing pad 414, the thickness of the wafer W before polishing, and the target values ​​of the ESFQD of the wafer W before polishing and the ESFQD after polishing. In this way, by determining the polishing time T2 based on the cumulative usage time of the back pad 62 and polishing pad 414, as well as the thickness of the wafer W before polishing, the target values ​​of the ESFQD before polishing and the ESFQD after polishing, variations in the amount of material removed by polishing from batch to batch can be further suppressed.

[0074] [Differentiation] Although embodiments of the present invention have been described in detail above with reference to the drawings, the specific configuration is not limited to these embodiments, and various improvements and design changes that do not depart from the spirit of the present invention are also included.

[0075] In the first and second embodiments, the polishing time determination process T1 and T2 was performed for each batch, but the polishing time determination process T1 and T2 may also be performed for each batch. In the first embodiment, the polishing time T1 may be determined based on the cumulative usage time of the back pad 62 and the polishing pad 414, without using formula (1). In the second embodiment, the polishing time T2 may be determined without using equation (2), based on the cumulative usage time of the back pad 62 and the polishing pad 414, the thickness of the film-coated wafer Wa before polishing, and the target values ​​of the ESFQD before and after polishing.

[0076] In the first and second embodiments, when a film-coated wafer Wa is subjected to a first or second finishing polishing step, or when a rough polishing step, a first finishing polishing step, or a second finishing polishing step is performed on a bare wafer Wb, the polishing time T1 or polishing time T2 to bring the polishing allowance to a target value may be calculated based on formula (1) or formula (2). In the second embodiment, when performing a rough polishing step, a first finish polishing step, or a second finish polishing step on a film-coated wafer Wa or a bare wafer Wb, the polishing time T3 or polishing time T4 to bring the polishing allowance to a target value may be calculated based on equation (3) or equation (4). Furthermore, in the first and second embodiments, the finishing polishing process is configured to be performed in two stages: a first finishing polishing process and a second finishing polishing process. However, the finishing polishing process may also be performed in a single stage.

[0077] In the second embodiment, ESFQD was used as an index representing flatness, but ESFQR (Edge flatness metric, Sector based, Front surface referenced, least squares fit reference plane, Range of the data within sector), ZDD (Z-height Double Differentiation), ESBID (Edge Site flatness Back reference Ideal Deviation), or ESBIR (Edge Site flatness Back reference Ideal Range) may also be used. [Examples]

[0078] Next, embodiments of the present invention will be described. However, the present invention is not limited to these embodiments.

[0079] An experiment was conducted to confirm the effect of adjusting the polishing time according to the cumulative usage time of the back pad 62 and the polishing pad 414. In the following experiment, the single-sided polishing apparatus 10 of the first embodiment and a wafer Wa with a polysilicon film formed on the surface to be polished W1 were used. The thickness of each wafer Wa and the thickness of each polysilicon film were the same.

[0080] [Example 1] As shown in Table 1 below, rough polishing of multiple batches of 60 coated wafers Wa was started when the cumulative usage time of the polishing pad 414 was 50.8% and the cumulative usage time of the back pad 62 was 1.5%. In Example 1, the cumulative usage time of the polishing pad 414 was in the mid-use state, which is about half of its lifespan, and the cumulative usage time of the back pad 62 was in the early use state, which is less than 2% of its lifespan. When performing the initial rough polishing of the batch, the cumulative usage time corresponding to the cumulative usage time ratio of the polishing pad 414 and the back pad 62 was substituted into equation (1) to determine the polishing time T1 required to bring the polishing allowance to the target value. Using the polishing conditions other than the polishing time T1 among the polishing conditions used to derive equation (1), the polysilicon film of each coated wafer Wa was roughly polished for a polishing time T1. In each subsequent batch, the cumulative usage time of the polishing pad 414 and back pad 62 at the start of rough polishing was substituted into equation (1) to re-determine the polishing time T1. Then, under the same polishing conditions as the first batch, except for the polishing time T1, the polysilicon film was rough polished for a polishing time T1.

[0081] [Example 2] At the start of rough polishing of multiple batches of 60 film-coated wafers Wa, as shown in Table 1, the cumulative usage time percentage of the polishing pad 414 was 51.7% and the cumulative usage time percentage of the back pad 62 was 48.1%, but otherwise, the rough polishing of the polysilicon film was performed in the same manner as in Example 1. In Example 2, the polishing pad 414 and the back pad 62 were in the mid-use state.

[0082] [Comparative Example 1] As shown in Table 1, when the cumulative usage time percentage of the polishing pad 414 was 53.3% and the cumulative usage time percentage of the back pad 62 was 1.66%, rough polishing of multiple batches of 60 coated wafers Wa was started. In Comparative Example 1, the polishing pad 414 was used middle period In this state, back pad 62 is being used. initial That was the situation. In all batches, the same polishing time was set to achieve the same target value for the amount of material removed by polishing as in Examples 1 and 2. Except for the polishing time, the same polishing conditions as in Example 1 were used for rough polishing of the polysilicon film.

[0083] [Comparative Example 2] At the start of rough polishing of multiple batches of 60 film-coated wafers Wa, as shown in Table 1, the rough polishing of the polysilicon film was performed under the same conditions as in Comparative Example 1, except that the cumulative usage time percentage of the polishing pad 414 was 54.2% and the cumulative usage time percentage of the back pad 62 was 48.6%. In Comparative Example 2, the polishing pad 414 and back pad 62 were in the mid-use state.

[0084] [evaluation] The thickness of the polysilicon film after polishing was measured for a total of 240 film-coated wafers Wa from Examples 1 and 2 and Comparative Examples 1 and 2. Figure 7 shows a box plot representing the measurement results. As shown in Figure 7, the maximum thickness of the polysilicon film in Examples 1 and 2, where the polishing time T1 is linked to the cumulative usage time of the polishing pad 414 and back pad 62, was thinner than the maximum thickness in Comparative Examples 1 and 2, where the polishing time is constant regardless of the cumulative usage time of the polishing pad 414 and back pad 62. The minimum thickness of the polysilicon film in Examples 1 and 2 was thicker than the minimum thickness in Comparative Examples 1 and 2. Furthermore, as shown in Table 1, the standard deviation of the polysilicon film thickness in Examples 1 and 2 was 0.18 μm, while the standard deviation of the polysilicon film thickness in Comparative Examples 1 and 2 was 0.30 μm. From the above, it was confirmed that variations in the amount of material removed during polishing can be suppressed by linking the polishing time T1 to the cumulative usage time of the polishing pad 414 and the back pad 62.

[0085] [Table 1] [Explanation of symbols]

[0086] 2... Polishing processing unit, 10, 10A... Single-sided polishing device, 12, 16... Polishing condition determination device, 61... Polishing head, 62... Back pad, 63... Retainer ring, 115, 155... Acquisition unit, 116, 156... Determination unit, 118... Polishing control unit, 414, 424, 434... Polishing pad, W... Wafer (wafer).

Claims

1. A polishing condition determination device for determining the polishing time when polishing a wafer, which is held in a polishing head via a back pad, and is pressed against a polishing pad, using a polishing liquid supplied to the polishing pad through the gap between a retainer ring surrounding the wafer and the polishing pad, wherein the polishing time is determined when polishing the wafer, An acquisition unit that acquires the cumulative usage time of the back pad and the cumulative usage time of the polishing pad, A polishing condition determination device comprising: a determination unit that determines the polishing time of the wafer based on a correlation between the cumulative usage time of the back pad and the decrease in the amount of material removed per unit time, and a correlation between the cumulative usage time of the polishing pad and the increase in the amount of material removed per unit time.

2. In the polishing condition determination apparatus according to claim 1, The determination unit is a polishing condition determination device that determines the polishing time based on the following formula (1). T1=A+Bb×Tb+Cb+Bp×Tp+Cp… (1) T: Polishing time (seconds) Tb: The cumulative usage time (seconds) of the back pad. Tp: The cumulative usage time (seconds) of the polishing pad. A: Base time (seconds) obtained by performing a linear regression analysis on the actual values ​​of single-sided polishing of the wafer. Bb: A coefficient corresponding to the back pad obtained by performing a linear regression analysis on the actual values ​​of single-sided polishing of the wafer. Cb: Adjustment time (seconds) corresponding to the back pad, obtained by performing a linear regression analysis on the actual values ​​of single-sided polishing of the wafer. Bp: A coefficient corresponding to the polishing pad obtained by performing a linear regression analysis on the actual values ​​of single-sided polishing of the wafer. Cp: ​​The adjustment time (seconds) corresponding to the polishing pad, obtained by performing a linear regression analysis on the actual values ​​of single-sided polishing of the wafer.

3. In the polishing condition determination apparatus according to claim 1, The acquisition unit acquires the thickness of the wafer before polishing, The determination unit determines the polishing time of the wafer based on the cumulative usage time of the back pad and the polishing pad and the thickness of the wafer before polishing.

4. In the polishing condition determination apparatus according to claim 3, The acquisition unit acquires target values ​​for the flatness of the wafer before polishing and after polishing. The determination unit determines the polishing time of the wafer based on the cumulative usage time of the back pad and the polishing pad, and the target values ​​of the wafer's thickness before polishing, flatness before polishing, and flatness after polishing.

5. In the polishing condition determination apparatus according to claim 1, The acquisition unit acquires target values ​​for the flatness of the wafer before polishing and after polishing. The determination unit determines the polishing time of the wafer based on the cumulative usage time of the back pad and the polishing pad, and the target values ​​of the flatness of the wafer before polishing and the flatness after polishing.

6. A polishing processing unit polishes a wafer, which is held by a polishing head via a back pad, by pressing the wafer against a polishing pad, and using a polishing liquid supplied to the polishing pad through the gap between the retainer ring surrounding the wafer and the polishing pad. A polishing condition determination apparatus according to any one of claims 1 to 5, which determines the polishing time when polishing the wafer in the polishing processing unit, A single-sided polishing apparatus comprising: a polishing control unit that controls the polishing processing unit based on the polishing time determined by the polishing condition determination device; and

7. A method for determining polishing conditions, which involves determining the polishing time when polishing a wafer held by a polishing head via a back pad, using a polishing liquid supplied to the polishing pad through the gap between a retainer ring surrounding the wafer and the polishing pad, while pressing the wafer against the polishing pad. The cumulative usage time of the back pad and the cumulative usage time of the polishing pad are obtained. A method for determining polishing conditions, which determines the polishing time of the wafer based on a correlation between the decrease in the amount of material removed per unit time as the cumulative usage time of the back pad increases, and a correlation between the increase in the amount of material removed per unit time as the cumulative usage time of the polishing pad increases.

8. In the method for determining polishing conditions according to claim 7, A method for determining polishing conditions, which determines the polishing time based on the following formula (1). T1=A+Bb×Tb+Cb+Bp×Tp+Cp… (1) T: Polishing time (seconds) Tb: The cumulative usage time (seconds) of the back pad. Tp: The cumulative usage time (seconds) of the polishing pad. A: Base time (seconds) obtained by performing a linear regression analysis on the actual values ​​of single-sided polishing of the wafer. Bb: A coefficient corresponding to the back pad obtained by performing a linear regression analysis on the actual values ​​of single-sided polishing of the wafer. Cb: Adjustment time (seconds) corresponding to the back pad, obtained by performing a linear regression analysis on the actual values ​​of single-sided polishing of the wafer. Bp: A coefficient corresponding to the polishing pad obtained by performing a linear regression analysis on the actual values ​​of single-sided polishing of the wafer. Cp: ​​The adjustment time (seconds) corresponding to the polishing pad, obtained by performing a linear regression analysis on the actual values ​​of single-sided polishing of the wafer.

9. In the method for determining polishing conditions according to claim 7, Furthermore, the thickness of the wafer before polishing is obtained. A method for determining polishing conditions, which determines the polishing time of a wafer based on the cumulative usage time of the back pad and the polishing pad and the thickness of the wafer before polishing.

10. In the method for determining polishing conditions according to claim 9, Furthermore, target values ​​for the flatness of the wafer before polishing and after polishing are obtained. A method for determining polishing conditions, which determines the polishing time of a wafer based on the cumulative usage time of the back pad and the polishing pad, and target values ​​for the wafer's thickness before polishing, flatness before polishing, and flatness after polishing.

11. In the method for determining polishing conditions according to claim 7, Furthermore, target values ​​for the flatness of the wafer before polishing and after polishing are obtained. A method for determining polishing conditions, which determines the polishing time of a wafer based on the cumulative usage time of the back pad and the polishing pad, and target values ​​for the flatness of the wafer before polishing and after polishing.

12. The polishing time is determined by the polishing condition determination method described in any one of claims 7 to 11. A single-sided polishing method for polishing the wafer based on the aforementioned polishing time.

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