Chemical mechanical polishing method

Abstract

A chemical mechanical polishing method comprises: obtaining a set value of a polishing liquid flow rate of a current nth wafer and a set value of a polishing time of the nth wafer; obtaining actual polishing liquid flow rates of first to (n-1)th wafers; obtaining a polishing liquid predicted flow rate of the nth wafer according to an autoregressive model and the actual polishing liquid flow rates of the first to (n-1)th wafers; if the polishing liquid predicted flow rate of the nth wafer is greater than the set value of the polishing liquid flow rate of the nth wafer, setting a polishing liquid predicted time of the nth wafer to be less than the set value of the polishing time of the nth wafer; if the polishing liquid predicted flow rate of the nth wafer is less than the set value of the polishing liquid flow rate of the nth wafer, setting the polishing liquid predicted time of the nth wafer to be greater than the set value of the polishing time of the nth wafer; and polishing the nth wafer according to the set value of the polishing liquid flow rate of the nth wafer and the polishing liquid predicted time of the nth wafer.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and more specifically to a chemical mechanical polishing method. Background Technology

[0002] Chemical mechanical polishing (CMP) equipment is used to planarize semiconductor wafers using abrasive slurry and mechanical polishing. With the development of integrated circuit manufacturing technology, CMP equipment needs to be able to control the amount of thin film removed from the wafer surface. During the polishing process, the polishing head picks up the wafer and applies downward pressure, ensuring full contact between the wafer and the polishing pad attached to the polishing disk. Simultaneously, abrasive slurry is injected between the wafer and the polishing disk. The combined effect of etching and polishing removes the thin film from the wafer surface, thus planarizing the wafer.

[0003] Existing chemical mechanical polishing (CMP) equipment typically uses pre-set, fixed process parameters, such as slurry flow rate and polishing time, based on experience during planarization. These parameters, set empirically, do not account for variations in equipment and wafer conditions during operation. Differences in equipment condition can cause instability in the slurry flow rate, resulting in discrepancies from the set values. This easily leads to under-polishing or over-polishing of the wafer surface film. Therefore, the precision of slurry flow rate control needs to be improved. Summary of the Invention

[0004] This invention provides a chemical mechanical polishing method, comprising: step S1: obtaining set values ​​for the polishing slurry flow rate and polishing time of the nth wafer, where n is an integer greater than or equal to 2; step S2: obtaining the actual polishing slurry flow rate from the first wafer to the (n-1)th wafer; step S3: obtaining the predicted polishing slurry flow rate of the nth wafer based on an autoregressive model and the actual polishing slurry flow rates from the first wafer to the (n-1)th wafer, wherein the autoregressive model is... Where x(n) is the predicted flow rate of the polishing slurry for the nth wafer, p is the order of the autoregressive model, and x(ni) is the actual flow rate of the polishing slurry for the nith wafer; w(n) is the white noise coefficient for the nth wafer; p is an integer greater than or equal to 1 and less than or equal to n-1; i is an integer greater than or equal to 1 and less than or equal to p; α iHere are the autoregressive coefficients for the ni-th wafer in the autoregressive model; Step S4: If the predicted flow rate of the polishing slurry for the n-th wafer is greater than the set value of the polishing slurry flow rate for the n-th wafer, then the predicted time of the polishing slurry for the n-th wafer is set to be less than the set value of the polishing time for the n-th wafer; If the predicted flow rate of the polishing slurry for the n-th wafer is less than the set value of the polishing slurry flow rate for the n-th wafer, then the predicted time of the polishing slurry for the n-th wafer is set to be greater than the set value of the polishing time for the n-th wafer; Step S5: Polish the n-th wafer according to the set value of the polishing slurry flow rate for the n-th wafer and the predicted time of the polishing slurry for the n-th wafer.

[0005] Optionally, for the predicted flow rate of the polishing slurry on the nth wafer, the coefficient is... to The steps for obtaining w(n) include: providing a matrix equation, wherein the matrix equation is:

[0006] ;

[0007] R xx The expression for (m) is m is an integer greater than or equal to 0 and less than or equal to p, and E[x(n)x(nm)] represents the mean of x(n)x(n) to x(n)x(np) corresponding to m taking values ​​from 0 to p; the Levinson-Durbin iterative algorithm is used to obtain the matrix equation. to , ;Will As w(n).

[0008] Optionally, the product of the predicted flow rate of the polishing slurry for the nth wafer and the predicted time of the polishing slurry for the nth wafer is equal to the product of the set value of the flow rate of the polishing slurry for the nth wafer and the set value of the polishing time for the nth wafer.

[0009] The technical solution of the present invention has the following beneficial effects:

[0010] The chemical mechanical polishing method provided by this invention uses an autoregressive model to predict the predicted flow rate of the polishing slurry for the nth wafer. If the predicted flow rate of the polishing slurry for the nth wafer is greater than the set value of the polishing slurry flow rate for the nth wafer, then the predicted polishing time for the nth wafer is set to be less than the set value of the polishing time for the nth wafer; if the predicted flow rate of the polishing slurry for the nth wafer is less than the set value of the polishing slurry flow rate for the nth wafer, then the predicted polishing time for the nth wafer is set to be greater than the set value of the polishing time for the nth wafer. The nth wafer is polished according to the set value of the polishing slurry flow rate for the nth wafer and the predicted polishing time for the nth wafer. This makes the product of the predicted flow rate of the polishing slurry for the nth wafer and the product of the actual flow rate and the actual polishing time before the polishing, thus avoiding the phenomenon of insufficient or excessive polishing of the thin film on the surface of the nth wafer, thereby improving the accuracy of controlling the polishing amount of the nth wafer. Attached Figure Description

[0011] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0012] Figure 1 This is a flowchart of a chemical mechanical grinding method. Detailed Implementation

[0013] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0014] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0015] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can also refer to the internal connection of two components; and they can refer to a wireless connection or a wired connection. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0016] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0017] One embodiment of the present invention provides a chemical mechanical grinding method, referencing Figure 1 This includes the following steps:

[0018] Step S1: Obtain the setting value of the polishing slurry flow rate and the setting value of the polishing time for the nth wafer, where n is an integer greater than or equal to 2;

[0019] Step S2: Obtain the actual flow rate of polishing slurry from the first wafer to the (n-1)th wafer;

[0020] Step S3: Obtain the predicted polishing slurry flow rate for the nth wafer based on the autoregressive model and the actual polishing slurry flow rates from the first wafer to the (n-1)th wafer. The autoregressive model is as follows: Where x(n) is the predicted flow rate of the polishing slurry for the nth wafer, p is the order of the autoregressive model, and x(ni) is the actual flow rate of the polishing slurry for the nith wafer; w(n) is the white noise coefficient for the nth wafer; p is an integer greater than or equal to 1 and less than or equal to n-1; i is an integer greater than or equal to 1 and less than or equal to p; α i represents the autoregressive coefficient for the ni-th wafer in the autoregressive model;

[0021] Step S4: If the predicted flow rate of the polishing slurry for the nth wafer is greater than the set value of the polishing slurry flow rate for the nth wafer, then the predicted polishing time for the nth wafer is set to be less than the set value of the polishing time for the nth wafer; if the predicted flow rate of the polishing slurry for the nth wafer is less than the set value of the polishing slurry flow rate for the nth wafer, then the predicted polishing time for the nth wafer is set to be greater than the set value of the polishing time for the nth wafer.

[0022] Step S5: Grind the nth wafer according to the set value of the polishing slurry flow rate and the predicted polishing slurry time of the nth wafer.

[0023] In this embodiment, an autoregressive model is used to predict the slurry flow rate of the nth wafer. If the predicted slurry flow rate of the nth wafer is greater than the set value of the slurry flow rate of the nth wafer, then the predicted slurry time of the nth wafer is set to be less than the set value of the grinding time of the nth wafer; if the predicted slurry flow rate of the nth wafer is less than the set value of the slurry flow rate of the nth wafer, then the predicted slurry time of the nth wafer is set to be greater than the set value of the grinding time of the nth wafer. The nth wafer is then ground according to the set value of the slurry flow rate of the nth wafer and the predicted slurry time of the nth wafer. This makes the product of the predicted slurry flow rate and the predicted slurry time of the nth wafer similar to the product of the actual flow rate and the actual grinding time, thus avoiding insufficient or excessive polishing of the thin film on the surface of the nth wafer, thereby improving the accuracy of controlling the amount of grinding on the nth wafer.

[0024] The settings for the polishing slurry flow rate of the first wafer are equal to the settings for the polishing slurry flow rate of the nth wafer, and the settings for the polishing time of the first wafer are equal to the settings for the polishing time of the nth wafer.

[0025] (Formula 1), where p is an integer greater than or equal to and less than or equal to n-1.

[0026] In the process of obtaining the predicted flow rate of the polishing slurry for the nth wafer, optimization is required. to And the value of w(n).

[0027] according to Get , where m is an integer greater than or equal to 0 and less than or equal to p;

[0028] according to Get ;

[0029] according to Get ;

[0030] according to Get R xx The expression for (m) is R xw (m) is represented as R xx (mi) is represented as ;

[0031] according to The first equation is obtained:

[0032] ;

[0033] Based on the first equation, the matrix equation is obtained as follows:

[0034] ;

[0035] Using the Levinson-Durbin iterative algorithm to obtain the matrix equation to ,as well as The value of; will As the value of w(n).

[0036] Multiplying both sides of Equation 1 by x(nm) yields (Formula 2), where m is an integer greater than or equal to 0 and less than or equal to p.

[0037] According to Formula 2, we get (Formula 3), where x(n)x(nm) is represented as x(n)x(n) when m is 0, and x(n)x(nm) is represented as x(n)x(np) when m is p. Let x(n) represent the mean of x(n) to x(np) as m takes values ​​from 0 to p; when m is 0... Represented as When m is p Represented as , For the values ​​of m from 0 to p, the corresponding values ​​are... to The mean.

[0038] Formula 4 is derived from Formula 3: When m is 0, w(n)x(nm) is represented as w(n)x(n) and w(n)x(nm); when m is p, w(n)x(nm) is represented as w(n)x(np). This represents the mean of w(n)x(n) to w(n)x(np) as m takes values ​​from 0 to p. express The mean value of m as it takes values ​​from 0 to p.

[0039] According to Formula 4, we obtain... (Formula 5). When m is 0 Represented as When m is p Represented as , This represents the value of m from 0 to p. to The mean.

[0040] Based on the even symmetry property of the autocorrelation function of the output signal, Equation 5 is transformed using the autocorrelation function. (Formula 6). R xx The expression for (m) is R xw (m) is represented as R xx (mi) is represented as .

[0041] Based on formula 6, the following first equation is derived:

[0042] ,in This represents the noise variance.

[0043] Transform the first equation above into a matrix equation:

[0044] ;

[0045] According to the matrix equation, to ,as well as A set of possible values. As the value of w(n).

[0046] Specifically, for a given n, when m equals 1, the matrix equation yields:

[0047] ;

[0048] When m equals 1 . When m equals 1 .

[0049] get: ; .

[0050] For a given n, when m equals 2, we can obtain the following from the matrix equation:

[0051] ;

[0052] When m equals 2 , When m equals 2 . When m equals 2 .

[0053] get: ;

[0054] ;

[0055] ;

[0056] Furthermore, we can deduce that:

[0057] ,

[0058] ,

[0059] ,

[0060] By recursion, we get:

[0061] (Formula 7),

[0062] (Formula 8),

[0063] (Formula 9),

[0064] For the value of order m, the corresponding , For the value of order m, the corresponding .

[0065] Given the actual flow rate of the polishing slurry for the nth wafer, the following formulas are used to obtain the desired result: (Formula 7) to (Formula 9) , to and .

[0066] Obtain the predicted flow rate of the polishing slurry for the (n+1)th wafer. .

[0067] Where x(n+1) is the predicted flow rate of the polishing slurry for the (n+1)th wafer, p is the order of the autoregressive model, and x(n-i+1) is the actual flow rate of the polishing slurry for the x(n-i+1)th wafer. For order p . for For order p .

[0068] In one embodiment, the product of the predicted flow rate of the polishing slurry for the nth wafer and the predicted time of the polishing slurry for the nth wafer is equal to the product of the set value of the flow rate of the polishing slurry for the nth wafer and the set value of the polishing time for the nth wafer.

[0069] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A chemical mechanical grinding method, characterized in that, include: Step S1: Obtain the setting value of the polishing slurry flow rate and the setting value of the polishing time for the nth wafer, where n is an integer greater than or equal to 2; Step S2: Obtain the actual flow rate of polishing slurry from the first wafer to the (n-1)th wafer; Step S3: Obtain the predicted polishing slurry flow rate for the nth wafer based on the autoregressive model and the actual polishing slurry flow rates from the first wafer to the (n-1)th wafer. The autoregressive model is as follows: , where x(n) is the predicted flow rate of the polishing slurry for the nth wafer, p is the order of the autoregressive model, x(ni) is the actual flow rate of the polishing slurry for the nith wafer; w(n) is the white noise coefficient for the nth wafer; p is an integer greater than or equal to 1 and less than or equal to n-1; i is an integer greater than or equal to 1 and less than or equal to p; αi is the autoregressive coefficient for the nith wafer in the autoregressive model; Step S4: If the predicted flow rate of the polishing slurry for the nth wafer is greater than the set value of the polishing slurry flow rate for the nth wafer, then the predicted polishing time for the nth wafer is set to be less than the set value of the polishing time for the nth wafer; if the predicted flow rate of the polishing slurry for the nth wafer is less than the set value of the polishing slurry flow rate for the nth wafer, then the predicted polishing time for the nth wafer is set to be greater than the set value of the polishing time for the nth wafer; the product of the predicted flow rate of the polishing slurry for the nth wafer and the predicted polishing time for the nth wafer is equal to the product of the set value of the polishing slurry flow rate for the nth wafer and the set value of the polishing time for the nth wafer. Step S5: Grind the nth wafer according to the set value of the polishing slurry flow rate and the predicted polishing slurry time of the nth wafer.

2. The chemical mechanical grinding method according to claim 1, characterized in that, For the predicted flow rate of the polishing slurry on the nth wafer, the coefficient is... to The steps for obtaining w(n) include: providing a matrix equation, wherein the matrix equation is: The expression for Rxx(m) is E[x(n)x(nm)]; m is an integer greater than or equal to 0 and less than or equal to p, and E[x(n)x(nm)] represents the mean of x(n)x(n) to x(n)x(np) corresponding to m taking values ​​from 0 to p; Using the Levinson-Durbin iterative algorithm to obtain the matrix equation to , ; Will As w(n).

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