Substrate polishing method and substrate polishing device

Abstract

To provide a substrate polishing method capable of suppressing occurrence of variance in quality of a substrate following polishing. A substrate polishing method according to the present disclosure includes: a first step (S1) in which a plurality of substrate shape indices indicating the shape of a substrate, and polishing log data for when the substrate is polished, are acquired in association with each other, and a substrate shape estimation function is generated by using these; a second step (S2) in which polishing of the substrate to be processed is started under initial polishing conditions; a third step (S3) in which polishing log data of the substrate to be processed is acquired, and the substrate shape of the substrate to be processed is estimated by using the acquired polishing log data and the substrate shape estimation function; and a fourth step (S4) for feedback-controlling a polishing machine in accordance with a difference ∆a between the estimated substrate shape of the substrate to be processed and a previous-time estimated substrate shape of the substrate to be processed, and an amount of deviation ∆b between the estimated substrate shape of the substrate to be processed and a target substrate shape, with the third step and the fourth step being repeated such that the substrate shape of the substrate to be processed approaches the target substrate shape.

Description

Substrate polishing method and substrate polishing apparatus

[0001] The present disclosure relates to a substrate polishing method and a substrate polishing apparatus.

[0002] In recent years, with the increasing integration and functionality of semiconductor integrated circuits, the development of microfabrication technologies for miniaturizing and densifying semiconductor elements has been progressing. Conventionally, in the manufacture of semiconductor integrated circuit devices, chemical mechanical polishing (hereinafter referred to as CMP) has been used to planarize interlayer insulating films, buried wiring, etc., in order to prevent problems such as unevenness (steps) on layer surfaces exceeding the depth of focus of lithography, making it impossible to obtain sufficient resolution. As the demand for higher definition and miniaturization of elements becomes stricter, the demand for substrate flatness and thickness variation has become even greater.

[0003] Patent Document 1 discloses a technique relating to a double-side polishing method for semiconductor substrates that suppresses variations in polishing quality by adapting to changes in the polishing environment during polishing.

[0004] International Publication No. 2018 / 083931

[0005] In recent years, as the demand for higher definition and miniaturization of semiconductor elements has become stricter, the demand for flatness and thickness variation of the substrates used has also increased. When substrates are polished using a polishing machine, variations in quality may occur from batch to batch even when polished under the same polishing conditions. Such variations in substrate quality can lead to variations in the quality of semiconductor elements fabricated using those substrates.

[0006] The present disclosure has been made in consideration of the above-described circumstances, and aims to provide a substrate polishing method and a substrate polishing apparatus that can suppress variations in the quality of substrates after polishing.

[0007] A substrate polishing method and a substrate polishing apparatus according to one aspect of the present disclosure are as follows.

[0008] [1] A substrate polishing method comprising: a first step of acquiring a plurality of substrate shape indices indicating the shape of a substrate after polishing the substrate using a polishing machine and polishing log data when the substrate is polished, each in correspondence with the other, and generating a substrate shape estimation function using the acquired substrate shape indices and polishing log data; a second step of starting polishing of a workpiece substrate under initial polishing conditions using the polishing machine; a third step of acquiring polishing log data for the workpiece substrate and estimating the substrate shape of the workpiece substrate using the acquired polishing log data and the substrate shape estimation function; and a fourth step of feedback-controlling the polishing machine in accordance with a difference Δa between the estimated substrate shape of the workpiece substrate and a previously estimated substrate shape of the workpiece substrate, and a deviation Δb between the estimated substrate shape of the workpiece substrate and a target substrate shape, wherein the third step and the fourth step are repeated so that the substrate shape of the workpiece substrate approaches the target substrate shape.

[0009] [2] The substrate polishing method according to [1], wherein a control variable table relating to control variables of the polishing machine corresponding to each of the differences Δa and each of the deviation amounts Δb is created in advance, and in the fourth step, the control variables of the polishing machine corresponding to each of the differences Δa and each of the deviation amounts Δb are determined by referring to the control variable table, and the polishing machine is feedback-controlled using the determined control variables.

[0010] [3] The substrate polishing method according to [1], wherein in the fourth step, the polishing machine is PID controlled in accordance with the difference Δa and the deviation amount Δb so that the substrate shape of the workpiece substrate approaches the target substrate shape.

[0011] [4] The substrate polishing method according to any one of [1] to [3], wherein the substrate shape estimation function is generated by acquiring a plurality of substrate shape indices indicating the shape of the substrate after polishing and polishing log data when the substrate is polished, each of which is associated with the other, and performing multiple regression analysis on the acquired substrate shape indices and polishing log data.

[0012] [5] The substrate polishing method according to any one of [1] to [4], wherein the polishing log data is at least one of the temperature of at least one of an upper platen and a lower platen of the polishing machine, the rotation speed of at least one of an upper platen and a lower platen of the polishing machine, the temperature of a slurry, and the flow rate of a slurry.

[0013] [6] The substrate polishing method according to any one of [1] to [5], wherein the control variable of the polishing machine is at least one of the temperature of at least one of an upper platen and a lower platen of the polishing machine, the rotation speed of at least one of an upper platen and a lower platen of the polishing machine, the temperature of the slurry, and the flow rate of the slurry.

[0014] [7] The substrate polishing method according to any one of [1] to [6], wherein the cycle of repeating the third step and the fourth step is 100 seconds or more and 300 seconds or less.

[0015] [8] The substrate polishing method according to [7], wherein the polishing log data of the workpiece substrate is an average value within a range going back a predetermined period based on the timing of feedback control of the polishing machine.

[0016] [9] A substrate polishing apparatus comprising: a polishing machine including a double-sided polishing mechanism that sandwiches a workpiece substrate between an upper platen and a lower platen and rotates at least one of the upper platen and the lower platen to polish both sides of the workpiece substrate with a slurry; a slurry supply unit that supplies the slurry to the double-sided polishing mechanism; and a motor that rotates at least one of the upper platen and the lower platen; a polishing log data acquisition unit that acquires polishing log data when the workpiece substrate is polished using the double-sided polishing mechanism; and a control unit that controls the polishing machine, wherein the control unit repeats the following steps so that the substrate shape of the workpiece substrate approaches the target substrate shape: a process of estimating a substrate shape of the workpiece substrate using the polishing log data of the workpiece substrate acquired by the polishing log data acquisition unit; and a process of feedback-controlling the polishing machine in accordance with a difference Δa between the estimated substrate shape of the workpiece substrate and a previously estimated substrate shape of the workpiece substrate, and a deviation amount Δb between the estimated substrate shape of the workpiece substrate and a target substrate shape, so that the substrate shape of the workpiece substrate approaches the target substrate shape.

[0017]

[10] The substrate polishing apparatus described in [9], wherein the control unit pre-stores a substrate shape estimation function generated using a substrate shape index indicating the shape of the substrate after polishing the substrate using the polishing machine and polishing log data when the substrate is polished, and the control unit estimates the substrate shape of the workpiece substrate using the polishing log data of the workpiece substrate acquired by the polishing log data acquisition unit and the pre-stored substrate shape estimation function.

[0018]

[11] The substrate polishing apparatus according to [9] or

[10] , wherein the control unit pre-stores a control variable table relating to control variables of the polishing machine corresponding to each of the differences Δa and each of the deviation amounts Δb, and the control unit determines the control variables of the polishing machine corresponding to the differences Δa and the deviation amounts Δb by referring to the control variable table, and feedback-controls the polishing machine using the determined control variables.

[0019] The present disclosure provides a substrate polishing method and a substrate polishing apparatus that can suppress variations in the quality of polished substrates.

[0020] FIG. 1 is a diagram showing an example of the configuration of a substrate polishing apparatus according to an embodiment; FIG. 2 is a flowchart for explaining a substrate polishing method according to an embodiment; FIG. 3 is a graph showing the relationship between a substrate shape estimated from polishing log data and an actual measurement value of the substrate shape; FIG. 4 is a diagram for explaining the timing of feedback control of a substrate polishing apparatus; FIG. 5 is a diagram showing an example of a control variable table; FIG. 6 is a graph showing the transition of a substrate shape when a substrate is polished (control off); FIG. 7 is a graph showing the transition of a substrate shape when a substrate is polished (control on); and FIG. 8 is a diagram showing the variation in substrate shape of a substrate after polishing.

[0021] Hereinafter, an embodiment will be described with reference to the drawings. FIG. 1 is a diagram showing an example of the configuration of a substrate polishing apparatus according to an embodiment. As shown in FIG. 1, the substrate polishing apparatus 1 according to this embodiment includes a polishing machine 20, a polishing log data acquisition unit 21, and a control unit 22. The substrate polishing apparatus 1 according to this embodiment is an apparatus for polishing substrates such as semiconductor substrates and glass substrates. Typically, the substrate polishing apparatus 1 is a double-sided polishing apparatus that polishes both sides of the substrate. Note that the substrates to be processed in this embodiment are not limited to semiconductor substrates and glass substrates, and may be used to polish other types of substrates.

[0022] As shown in Fig. 1, the polishing machine 20 includes a double-sided polishing mechanism 10, a slurry supply unit 15, and a motor 16. The double-sided polishing mechanism 10 includes an upper surface plate 11 and a lower surface plate 12. A polishing pad 13 is provided on the lower surface of the upper surface plate 11. A polishing pad 14 is provided on the upper surface of the lower surface plate 12. At least one of the upper surface plate 11 and the lower surface plate 12 is rotated by a motor 16. Typically, two motors 16 are provided independently for the upper surface plate 11 and the lower surface plate 12.

[0023] The slurry supply unit 15 is configured to supply slurry to the double-sided polishing mechanism 10. Specifically, the slurry supply unit 15 supplies slurry between the upper surface plate 11 and the lower surface plate 12. A substrate 18 to be polished (hereinafter also referred to as the workpiece substrate 18) is disposed between the upper surface plate 11 and the lower surface plate 12. In the substrate polishing apparatus 1 according to this embodiment, the double-sided polishing mechanism 10 is configured to sandwich the workpiece substrate 18 between the upper surface plate 11 and the lower surface plate 12, rotate at least one of the upper surface plate 11 and the lower surface plate 12, and polish both sides of the workpiece substrate 18 with the slurry.

[0024] The grinder 20 shown in FIG. 1 is an example, and a grinder having a different configuration may be used as the grinder 20 in this embodiment.

[0025] The polishing log data acquiring unit 21 acquires polishing log data when the polishing machine 20 polishes the workpiece substrate 18 using the double-sided polishing mechanism 10. Here, the polishing log data is at least one of the temperature of at least one of the upper surface plate 11 and the lower surface plate 12 of the polishing machine 20, the rotation speed of at least one of the upper surface plate 11 and the lower surface plate 12 of the polishing machine 20, the temperature of the slurry, and the flow rate of the slurry.

[0026] For example, the temperatures of the upper surface plate 11 and the lower surface plate 12 can be obtained from thermometers provided on each of the upper surface plate 11 and the lower surface plate 12. The rotation speeds of the upper surface plate 11 and the lower surface plate 12 can be obtained from rotary encoders provided on each of the upper surface plate 11 and the lower surface plate 12. The temperature of the slurry can be obtained from thermometers provided in a slurry tank that stores the slurry or in a pipe for transporting the slurry. The flow rate of the slurry can be obtained from a flow meter provided in a pipe for transporting the slurry from the slurry tank to the double-side polishing mechanism 10.

[0027] These pieces of polishing log data are merely examples, and in this embodiment, polishing log data other than these may be acquired from the polishing machine 20 as the polishing log data.

[0028] The control unit 22 controls the polishing machine 20. Specifically, the control unit 22 repeats a process of estimating the substrate shape of the workpiece substrate 18 using the polishing log data of the workpiece substrate 18 acquired by the polishing log data acquisition unit 21, and a process of feedback-controlling the polishing machine 20 in accordance with a difference Δa between the estimated substrate shape of the workpiece substrate 18 and the previously estimated substrate shape of the workpiece substrate 18, and a deviation Δb between the estimated substrate shape of the workpiece substrate 18 and the target substrate shape, so that the substrate shape of the workpiece substrate 18 approaches the target substrate shape.

[0029] The operation of the control unit 22 (substrate polishing method) will be described in detail below. Fig. 2 is a flowchart for explaining the substrate polishing method according to this embodiment, and is a flowchart for explaining the operation of the control unit 22.

[0030] In this embodiment, first, a substrate shape estimation function is generated (step S1). Specifically, a plurality of substrate shape indices indicating the shape of the substrate 18 after polishing the substrate 18 using the polishing machine 20 and polishing log data when the substrate 18 is polished are acquired in association with each other. Then, the acquired substrate shape indices and polishing log data are used to generate the substrate shape estimation function. For example, the substrate shape estimation function may be generated by performing multiple regression analysis on the acquired substrate shape indices and polishing log data. Here, the polishing log data can be acquired by the polishing log data acquisition unit 21. Furthermore, the substrate shape indices can be acquired by actually measuring the thickness of the substrate 18 after polishing.

[0031] The substrate 18 polished in step S1 is a substrate 18 for generating a substrate shape estimation function, and is different from the workpiece substrate 18 polished in steps S2 to S4. In other words, the substrate 18 polished in step S1 is a substrate used to set the conditions for the polishing machine 20. The same type of substrate as the workpiece substrate 18 is used.

[0032] An example of a method for generating a substrate shape estimation function will be described in detail below. First, a plurality of substrate shape indices (shape data) indicating the shape of the substrate 18 after the substrate 18 has been polished using the polishing machine 20 and a plurality of pieces of polishing log data when the substrate 18 is polished are prepared. At this time, the number of data and the data resolution for each are prepared at a level that is statistically significant.

[0033] The substrate shape index (shape data) of the substrate 18 can be the total thickness value (TTV), which evaluates the thickness unevenness of the substrate 18. However, since the TTV is an index that expresses the absolute value of the thickness unevenness of the substrate, it cannot express the uneven shape of the substrate. For this reason, a regression analysis is performed on the substrate thickness data using Zernike polynomials, and if the Z4 term indicating the focus component is negative, the TTV is expressed as a positive value, and if the Z4 term is positive, the TTV is expressed as a negative value, thereby making it possible to express the substrate shape using the numerical value of the TTV. This data is referred to as "TTV (in plus / minus notation)."

[0034] The substrate shape index (shape data) indicating the shape of the substrate after polishing may be the TTV itself, or a TTV (notated as plus or minus) that reflects the unevenness of the substrate. Alternatively, a regression analysis may be performed on the substrate thickness data using Zernike polynomials, and the coefficients of each term obtained may be used as is. The substrate shape index (shape data) is also an index indicating the quality of the substrate after polishing. In this embodiment, an index based on the thickness of the substrate is used to represent the shape of the substrate, but other indices may be used as long as they express the polishing quality of the substrate, such as a reflected wavefront or a transmitted wavefront.

[0035] In this embodiment, for example, the objective index is set to Y, and one of the above-mentioned substrate shape indexes is used, and the explanatory variable is set to X (X １ , X ２ , X ３ ,,,X ｎ (n is a positive integer) and polishing log data corresponding to each substrate shape index is used to perform multiple regression analysis. Here, it is preferable to use polishing log data immediately before the end of polishing as the polishing log data to be used, and for example, it is preferable to use an average value within a range going back 5 to 15 minutes from the timing of the end of polishing. The polishing log data acquired by the polishing log data acquisition unit 21 is used as the explanatory variable, and the following derivation formula is obtained by multiple regression analysis.

[0036] Y=A ０ +A １ X １ +A ２ X ２ +...+A ｎ X ｎ

[0037] Here, A ０ is a constant, and (A １ , A ２ , A ３ ...A ｎ (n is a positive integer) is a regression coefficient. Each value of A can be calculated using a general statistical method such as the least squares method or by using the know-how of an engineer.

[0038] The substrate shape index indicates the magnitude relationship between the thickness at the center position of the substrate and the average thickness of the substrate. For example, if the substrate shape index is positive, it indicates that the center position of the substrate is convex. On the other hand, if the substrate shape index is negative, it indicates that the center position of the substrate is concave.

[0039] 3 is a graph showing the relationship between the substrate shape estimated from the polishing log data and the actual measurement value of the substrate shape. The substrate shape estimated from the polishing log data is a value (TTV (notated with plus or minus)) obtained by estimating the substrate shape from the polishing log data using the substrate shape estimation function described above. The actual measurement value of the substrate shape is a value (TTV (notated with plus or minus)) obtained by actually measuring the thickness of the substrate after polishing.

[0040] As shown in Fig. 3, there is a correlation between the substrate shape estimated from the polishing log data and the actual measured value of the substrate shape. In the graph shown in Fig. 3, the correlation coefficient of each data is R ２ = 0.4315. Therefore, in this embodiment, by using the polishing log data acquired by the polishing log data acquisition unit 21, the substrate shape index (shape data) of the workpiece substrate 18 being polished can be calculated in real time. Therefore, the current substrate shape of the workpiece substrate 18 can be predicted in real time without removing the workpiece substrate 18 from the polishing machine 20.

[0041] 3, the quality tolerance based on the actual measurement value of the substrate shape corresponds to the range to be controlled for the substrate shape estimated from the polishing log data. Therefore, by controlling the polishing machine 20 so that the substrate shape estimated from the polishing log data falls within the range to be controlled, the workpiece substrate 18 can be polished so as to satisfy the quality tolerance.

[0042] The step of generating the substrate shape estimation function (step S1) is performed before the subsequent steps S2 to S4 are performed. In other words, the substrate shape estimation function is generated in advance before steps S2 to S4 are performed. For example, the generated substrate shape estimation function may be stored in advance in control unit 22.

[0043] Next, the control unit 22 starts polishing the workpiece substrate 18 under initial polishing conditions using the polishing machine 20 (step S2). The workpiece substrate 18 is a substrate to be processed, and is a substrate different from the substrate used in step S1. The initial polishing conditions can be any polishing conditions. For example, the initial polishing conditions may be the same as the polishing conditions used when the substrate shape estimation function was generated in step S1, or these polishing conditions may be fine-tuned. Note that even after step S2, the polishing log data acquisition unit 21 continues to acquire polishing log data at all times (at a constant interval).

[0044] Next, the control unit 22 estimates the substrate shape of the workpiece substrate 18 currently being processed (step S3). Specifically, the control unit 22 acquires polishing log data of the workpiece substrate 18 from the polishing log data acquisition unit 21, and estimates the substrate shape of the workpiece substrate 18 using the acquired polishing log data and the substrate shape estimation function generated in step S1. Note that estimating the substrate shape of the workpiece substrate 18 means, in other words, determining a substrate shape index.

[0045] Next, the control unit 22 performs feedback control of the polishing machine 20 in accordance with the difference Δa between the estimated substrate shape of the workpiece substrate 18 and the previously estimated substrate shape of the workpiece substrate 18, and the deviation Δb between the estimated substrate shape of the workpiece substrate 18 and the target substrate shape (step S4). The control unit 22 then repeats steps S3 and S4 so that the substrate shape of the workpiece substrate 18 approaches the target substrate shape. The control unit 22 also terminates polishing of the workpiece substrate 18 when a predetermined condition is satisfied. For example, the control unit 22 may terminate polishing when a predetermined polishing time has elapsed. Alternatively, the control unit 22 may terminate polishing when the estimated substrate shape of the workpiece substrate 18 reaches the target shape.

[0046] 4 is a diagram for explaining the timing of feedback control of the substrate polishing apparatus. The control unit 22 feedback-controls the polishing machine 20 at timings t1, t2, t3, ... shown in FIG. 4. At this time, the control unit 22 may use an average value within a range going back a predetermined period Δt from the timings t1, t2, t3, ... at which the polishing machine 20 is feedback-controlled as the reference, as polishing log data for the workpiece substrate 18. For example, the control unit 22 may use an average value within a range going back a predetermined period Δt from the timings t1, t2, t3, ... at which the polishing machine 20 is feedback-controlled, as the ... ｎ＋１ -t ｎ The feedback control period (n is an integer of 0 or more) may be set to 100 seconds or more and 300 seconds or less. Δt may be set to 10 seconds or more and 30 seconds or less. Note that these values ​​are merely examples, and the feedback control period and Δt value can be set arbitrarily.

[0047] The feedback control of step S4 will be specifically described below. The control unit 22 feedback-controls the polishing machine 20 in accordance with the difference Δa between the estimated substrate shape of the workpiece substrate 18 and the previously estimated substrate shape of the workpiece substrate, and the deviation Δb between the estimated substrate shape of the workpiece substrate 18 and the target substrate shape.

[0048] Here, the difference Δa is the difference between the substrate shape of the workpiece substrate 18 estimated this time and the substrate shape of the workpiece substrate estimated at the immediately previous timing. Note that the estimated "substrate shape" of the workpiece substrate 18 is synonymous with the "substrate shape index" calculated using the acquired polishing log data and the substrate shape estimation function.

[0049] 4, for example, if the current timing is t3 and the previous timing is t2, the difference Δa is the difference between the substrate shape of the workpiece substrate 18 estimated at timing t3 and the substrate shape of the workpiece substrate estimated at timing t2. Furthermore, the deviation Δb is the amount of deviation of the estimated substrate shape of the workpiece substrate 18 from the target substrate shape. The control unit 22 determines a control amount using the difference Δa and the deviation Δb, and feedback-controls the polishing machine 20 using the determined control amount.

[0050] For example, the control variables of the polishing machine 20 are at least one of the temperature of at least one of the upper and lower plates 11 and 12 of the polishing machine 20, the rotation speed of at least one of the upper and lower plates 11 and 12 of the polishing machine 20, the temperature of the slurry, and the flow rate of the slurry.

[0051] In this embodiment, for example, a control variable table may be created in advance regarding the control variables of the grinder 20 corresponding to each difference Δa and each deviation amount Δb. In this case, the control unit 22 may refer to the control variable table to determine the control variable of the grinder 20 corresponding to the difference Δa and the deviation amount Δb, and feedback-control the grinder 20 using the determined control variable.

[0052] 5 is a diagram showing an example of a control variable table, which stores control variables of the polishing machine 20 corresponding to a difference Δa between the previously estimated substrate shape and the currently estimated substrate shape and a deviation Δb between the estimated substrate shape of the workpiece substrate and a target substrate shape, in association with each other.

[0053] For example, the control amount in the region indicated by symbol A in the control amount table shown in Fig. 5 has a large difference Δa and a large deviation Δb, so the current control amount is determined to be inappropriate and the control amount (processing condition) is changed to a larger value. Also, the control amount in the region indicated by symbol B in the control amount table shown in Fig. 5 has a large difference Δa and a small deviation Δb, so the current control amount will deviate from the target substrate shape and the control amount is changed to a smaller value from the current control amount (processing condition).

[0054] Furthermore, for the control amount in the region indicated by symbol C in the control amount table shown in Fig. 5, the difference Δa is a negative value and the deviation Δb is large, so the current control amount is determined to be appropriate and the current control amount (machining conditions) is maintained. Furthermore, for the control amount in the region indicated by symbol D in the control amount table shown in Fig. 5, the difference Δa is close to zero and the deviation Δb is also small, so the current control amount is determined to be appropriate and the current control amount (machining conditions) is maintained.

[0055] Specifically, for example, if the difference Δa is +1 and the deviation Δb is +3.0, the control unit 22 references the control variable table to determine the control variable as -3.0, and feedback-controls the polisher 20 with the determined control variable of -3.0. In other words, in this case, the difference Δa is +1, and the substrate shape (substrate shape index) has not decreased even with the previous feedback control. Also, the deviation Δb is +3.0, and the deviation from the target substrate shape is large on the positive side. In this case, the control variable of the polisher is set to -3.0 so that the substrate shape index of the workpiece substrate 18 approaches 0.

[0056] Furthermore, for example, if the difference Δa is -1.0 and the deviation Δb is -3.0, the control unit 22 references the control amount table, determines the control amount to be +1.5, and feedback-controls the polisher 20 with the determined control amount of +1.5. In other words, in this case, the difference Δa is -1.0, and the substrate shape (substrate shape index) has decreased due to the previous feedback control. Furthermore, the deviation Δb is -3.0, and the deviation from the target substrate shape is large on the negative side. In this case, the control amount of the polisher is set to +1.5 so that the substrate shape index of the workpiece substrate 18 approaches 0.

[0057] The numerical values ​​of the control amounts (-3.0 to +3.0) listed in the control amount table correspond to the amount of change for changing the substrate shape (substrate shape index) of the substrate being polished. For example, a control amount of "0" indicates that the control amount of the polishing machine 20 is to be maintained at the current level. A control amount of "+3.0" indicates that the control amount (control parameter) of the polishing machine 20 is to be changed so that the substrate shape (substrate shape index) becomes "+3.0". A control amount of "-3.0" indicates that the control amount (control parameter) of the polishing machine 20 is to be changed so that the substrate shape (substrate shape index) becomes "-3.0".

[0058] As described above, the control variables of the polishing machine 20 are at least one of the temperature of at least one of the upper surface plate 11 and the lower surface plate 12 of the polishing machine 20, the rotation speed of at least one of the upper surface plate 11 and the lower surface plate 12 of the polishing machine 20, the temperature of the slurry, and the flow rate of the slurry. The control unit 22 changes these parameters of the polishing machine 20 so as to achieve the control variables listed in the control variable table.

[0059] For example, when the control amount is "-3.0", the current substrate shape (substrate shape index) is assumed to be positive and the central position of the substrate is assumed to be convex, so the polishing machine 20 changes the control parameters of the polishing machine 20 so that the thickness of the substrate at the central position becomes smaller.

[0060] For example, if the control amount is "+3.0", the current substrate shape (substrate shape index) is assumed to be negative and the center position of the substrate is assumed to be concave, so the polishing machine 20 changes the control parameters of the polishing machine 20 so that the thickness of the peripheral side of the substrate becomes smaller.

[0061] As explained above, in this embodiment, for example, if the substrate shape index is positive, the center position of the substrate is convex, and therefore the processing conditions are corrected so that the center position of the substrate becomes concave. In other words, if the substrate shape index can be moved in the negative direction, the substrate shape can be made closer to flat. In this case, if the amount of change in the corrected processing conditions is excessive, the center position of the substrate will become the opposite, concave. On the other hand, if the amount of change in the processing conditions is too small, it will take a long time to make the substrate shape closer to flat.

[0062] In this embodiment, as described above, feedback control is performed to improve the quality of the substrate and shorten the processing time. For example, when the control variable table shown in Figure 5 is used, the difference Δa between the previously estimated substrate shape and the currently estimated substrate shape is calculated, and if the difference Δa is small even after the processing conditions have been corrected, it is determined that the amount of change in the previous processing conditions was insufficient, and a decision is made to make a larger change to the processing conditions. Furthermore, if the deviation Δb between the estimated substrate shape of the workpiece substrate and the target substrate shape is sufficiently small and the difference Δa is almost zero, it is determined that the current processing conditions are appropriate, and a decision is made not to change the processing conditions.

[0063] As described above, in this embodiment, the substrate shape of the workpiece substrate 18 is estimated using the acquired polishing log data and the substrate shape estimation function, and the polishing machine 20 is feedback-controlled in accordance with the difference Δa between the estimated substrate shape of the workpiece substrate 18 and the previously estimated substrate shape of the workpiece substrate 18, and the deviation Δb between the estimated substrate shape of the workpiece substrate 18 and the target substrate shape. Therefore, it is possible to provide a substrate polishing method and substrate polishing apparatus that can suppress variations in the quality of the substrates after polishing.

[0064] In this embodiment, when performing the feedback control in step S4, the polishing machine 20 may be PID (Proportional-Integral-Differential) controlled in accordance with the difference Δa and the deviation Δb so that the substrate shape of the workpiece substrate 18 approaches the target substrate shape. That is, the control unit 22 may PID control the polishing machine 20 so that the substrate shape of the workpiece substrate 18 approaches the target substrate shape by previously setting the parameters of the P gain, I gain, and D gain.

[0065] 6 and 7 are graphs showing the transition of the substrate shape when the substrate is polished. Fig. 6 shows the transition of the substrate shape when the feedback control according to this embodiment is turned off, and Fig. 7 shows the transition of the substrate shape when the feedback control according to this embodiment is turned on.

[0066] As shown in Fig. 6, when feedback control was turned off, processing ended before the substrate shape (substrate shape index) reached the target value, and a substrate of good quality was not obtained. On the other hand, as shown in Fig. 7, when feedback control was turned on, feedback control was performed several times during polishing, and the substrate shape (substrate shape index) reached the target value, resulting in a substrate of good quality.

[0067] Fig. 8 is a diagram showing the variation in substrate shape of a substrate after polishing. The left diagram of Fig. 8 shows the variation in substrate shape when feedback control is turned off, and the right diagram of Fig. 8 shows the variation in substrate shape when feedback control is turned on. The vertical axis of Fig. 8 represents TTV.

[0068] As shown in the left diagram of Figure 8, when feedback control was turned off, the variation in substrate shape (substrate shape index) was large. On the other hand, as shown in the right diagram of Figure 8, when feedback control was turned on, the variation in substrate shape (substrate shape index) was small. Therefore, it can be said that turning on feedback control significantly improved substrate quality.

[0069] According to the present disclosure described above, it is possible to provide a substrate polishing method and a substrate polishing apparatus that can suppress variations in the quality of polished substrates.

[0070] The present invention has been described above in accordance with the above-mentioned embodiment, but the present invention is not limited to the configuration of the above-mentioned embodiment, and naturally includes various modifications, alterations, and combinations that a person skilled in the art can make within the scope of the invention as defined in the claims of this application.

[0071] This application claims priority based on Japanese Patent Application No. 2024-150528, filed September 2, 2024, the disclosure of which is incorporated herein by reference in its entirety.

[0072] REFERENCE SIGNS LIST 1 Substrate polishing apparatus 10 Double-side polishing mechanism 11 Upper surface plate 12 Lower surface plate 13, 14 Polishing pad 15 Slurry supply unit 16 Motor 18 Substrate (substrate to be processed) 20 Polishing machine 21 Polishing log data acquisition unit 22 Control unit

Claims

1. A substrate polishing method comprising: a first step of acquiring a plurality of substrate shape indices indicating the shape of a substrate after polishing the substrate using a polishing machine, each corresponding to a corresponding piece of polishing log data when the substrate was polished, and generating a substrate shape estimation function using the acquired substrate shape indices and polishing log data; a second step of starting polishing of a workpiece substrate under initial polishing conditions using the polishing machine; a third step of acquiring polishing log data for the workpiece substrate, and estimating the substrate shape of the workpiece substrate using the acquired polishing log data and the substrate shape estimation function; and a fourth step of feedback-controlling the polishing machine in accordance with a difference Δa between the estimated substrate shape of the workpiece substrate and a previously estimated substrate shape of the workpiece substrate, and a deviation Δb between the estimated substrate shape of the workpiece substrate and a target substrate shape; and repeating the third step and the fourth step so that the substrate shape of the workpiece substrate approaches the target substrate shape.

2. A substrate polishing method as described in claim 1, wherein a control variable table is created in advance regarding control variables of the polishing machine corresponding to each of the differences Δa and each of the deviation amounts Δb, and in the fourth step, the control variables of the polishing machine corresponding to each of the differences Δa and each of the deviation amounts Δb are determined by referring to the control variable table, and the polishing machine is feedback-controlled using the determined control variables.

3. A substrate polishing method as described in claim 1, wherein in the fourth step, the polishing machine is PID controlled so that the substrate shape of the workpiece substrate approaches the target substrate shape in accordance with the difference Δa and the deviation amount Δb.

4. A substrate polishing method according to any one of claims 1 to 3, wherein the substrate shape estimation function is generated by acquiring a plurality of substrate shape indices indicating the shape of the substrate after polishing and polishing log data when the substrate is polished, each of which is associated with the other, and performing multiple regression analysis of the acquired substrate shape indices and polishing log data.

5. A substrate polishing method according to any one of claims 1 to 3, wherein the polishing log data is at least one of the temperature of at least one of the upper and lower plates of the polishing machine, the rotation speed of at least one of the upper and lower plates of the polishing machine, the temperature of the slurry, and the flow rate of the slurry.

6. A substrate polishing method according to any one of claims 1 to 3, wherein the control variable of the polishing machine is at least one of the temperature of at least one of the upper and lower plates of the polishing machine, the rotation speed of at least one of the upper and lower plates of the polishing machine, the temperature of the slurry, and the flow rate of the slurry.

7. A substrate polishing method according to any one of claims 1 to 3, wherein the cycle of repeating the third step and the fourth step is 100 seconds or more and 300 seconds or less.

8. A substrate polishing method according to claim 7, wherein the polishing log data for the substrate to be processed is an average value within a range going back a predetermined period from the timing of feedback control of the polishing machine.

9. A substrate polishing apparatus comprising: a polishing machine including a double-sided polishing mechanism that sandwiches a workpiece substrate between an upper platen and a lower platen and rotates at least one of the upper platen and the lower platen to polish both sides of the workpiece substrate with slurry; a slurry supply unit that supplies the slurry to the double-sided polishing mechanism; and a motor that rotates at least one of the upper platen and the lower platen; a polishing log data acquisition unit that acquires polishing log data when the workpiece substrate is polished using the double-sided polishing mechanism; and a control unit that controls the polishing machine, wherein the control unit repeats the following steps so that the substrate shape of the workpiece substrate approaches the target substrate shape: estimating a substrate shape of the workpiece substrate using the polishing log data of the workpiece substrate acquired by the polishing log data acquisition unit; and feedback-controlling the polishing machine in accordance with a difference Δa between the estimated substrate shape of the workpiece substrate and a previously estimated substrate shape of the workpiece substrate, and a deviation amount Δb between the estimated substrate shape of the workpiece substrate and a target substrate shape.

10. A substrate polishing apparatus as described in claim 9, wherein the control unit pre-stores a substrate shape estimation function generated using a substrate shape index indicating the shape of the substrate after polishing the substrate using the polishing machine and polishing log data when the substrate is polished, and the control unit estimates the substrate shape of the substrate to be processed using the polishing log data of the substrate to be processed acquired by the polishing log data acquisition unit and the pre-stored substrate shape estimation function.

11. A substrate polishing apparatus as described in claim 9 or 10, wherein the control unit pre-stores a control variable table relating to control variables of the polishing machine corresponding to each of the differences Δa and each of the deviation amounts Δb, and the control unit determines the control variable of the polishing machine corresponding to each of the differences Δa and each of the deviation amounts Δb by referring to the control variable table, and feedback-controls the polishing machine using the determined control variable.

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