Grinding control method of chemical mechanical grinding process

Abstract

The invention provides a grinding control method of a chemical mechanical grinding process, which comprises the following steps of: setting a grinding rate compensation formula and compensating an ideal grinding rate of a current wafer by using the grinding rate compensation formula to obtain an expected grinding rate of a next wafer; and then the grinding time of the next wafer is obtained according to the expected grinding rate and the preset ground thickness of the next wafer, and CMP is conducted on the next wafer according to the grinding time of the next wafer. According to the method, the expected grinding rate of the next wafer is adjusted in real time by setting the grinding rate compensation formula, so that the actual ground thickness of the next wafer is the same as the preset ground thickness, the stability of the grinding thickness of the wafer is realized, the influence of the service life of consumables is solved, and the grinding efficiency is improved. And the problem that the actual grinding thickness of the wafer deviates from the preset grinding thickness due to abnormal IAPC adjustment is solved.

Description

Technical Field

[0001] The present application relates to the field of semiconductor manufacturing technology, and in particular to a polishing control method for a chemical mechanical polishing process. Background Art

[0002] The chemical mechanical polishing (CMP) process of a dielectric layer (such as silicon dioxide) on a wafer is difficult to control due to the uniform / single polishing medium, the polishing stop position and the polishing surface morphology. Therefore, an IAPC (integrated advanced process control) system is usually used for the CMP process. This system uses metrology methods to calculate the pre- and post-feedback values, and automatically adjusts the wafer polishing amount in real time to achieve a stable polishing thickness.

[0003] IAPC collects the grinding rate at the time of the production line coming off the assembly line. The grinding rate is not updated in real time. The grinding rate of the chemical mechanical polishing process of silica is affected by the service life of the consumables. The grinding rate accelerates sharply at the end of the service life of the polishing pad. At the end of the service life, the overstocked products are affected by the rapid change in the grinding rate. The actual grinding thickness of silica often deviates from the preset grinding thickness of silica (too thick or too thin) due to insufficient IAPC adjustment. Summary of the Invention

[0004] The present application provides a polishing control method for a chemical mechanical polishing process, which can solve the problem that the actual polishing thickness of a certain dielectric layer is too thick or too thin due to the influence of the service life of consumables and abnormal IAPC adjustment, and deviates from the preset polishing thickness of the dielectric layer.

[0005] The present invention provides a method for controlling a chemical mechanical polishing process, comprising:

[0006] Step 1: Set up a grinding rate compensation formula in the IAPC system;

[0007] Step 2: Using the grinding rate compensation formula, the ideal grinding rate of the current wafer is compensated to obtain the expected grinding rate of the next wafer;

[0008] Step 3: Obtaining a grinding time for the next wafer based on the expected grinding rate of the next wafer and the preset grinding thickness of the next wafer;

[0009] Step 4: performing chemical mechanical polishing on the next wafer using the IAPC system according to the polishing time of the next wafer;

[0010] Step 5: Determine whether there are wafers to be ground in this batch. If there are wafers to be ground in this batch, return to execute the second step to the fourth step until all wafers in this batch are ground.

[0011] Optionally, in the polishing control method of the chemical mechanical polishing process, the polishing rate compensation formula is as follows:

[0012] RR_Offset=x*Sign(THK_Target,THK_AvePost,THK_Offset_spec)*ABS(RR[n]-RR_Act);

[0013] Wherein, RR_Offset is the grinding rate compensation value; x is a coefficient to prevent sudden changes in grinding rate; THK_Target is the target thickness of any wafer in the same batch after grinding; THK_AvePost is the actual thickness of the current wafer after grinding; THK_Offset_spec is the thickness compensation value; RR[n] is the actual grinding rate of the current wafer; RR_Act is the ideal grinding rate of the current wafer.

[0014] Optionally, in the polishing control method of the chemical mechanical polishing process, Sign(THK_Target, THK_AvePost, THK_Offset_spec) is configured as:

[0015] If (THK_Target - THK_AvePost) > THK_Offset_spec, then Sign(THK_Target, THK_AvePost, THK_Offset_spec) takes the value 1;

[0016] If (THK_Target - THK_AvePost) < (-THK_Offset_spec), then Sign(THK_Target, THK_AvePost, THK_Offset_spec) takes the value -1;

[0017] If (-THK_Offset_spec)≤(THK_Target-THK_AvePost)≤THK_Offset_spec, then Sign(THK_Target,THK_AvePost,THK_Offset_spec) takes the value 0.

[0018] Optionally, in the polishing control method of the chemical mechanical polishing process, the formula involved in the second step is:

[0019] RR_Model=RR_Act+RR_Offset;

[0020] Among them, RR_Model is the expected polishing rate of the next wafer; RR_Act is the ideal polishing rate of the current wafer; RR_Offset is the polishing rate compensation value.

[0021] Optionally, in the polishing control method of the chemical mechanical polishing process, the formula involved in the second step is:

[0022] RR_Model=RR_Act+x*Sign(THK_Target,THK_AvePost,THK_Offset_spec)*A BS(RR[n]-RR_Act);

[0023] Where RR_Model is the expected polishing rate of the next wafer, RR_Act is the ideal polishing rate of the current wafer, x is a coefficient to prevent sudden changes in the polishing rate; THK_Target is the target thickness of any wafer in the same batch after polishing; THK_AvePost is the actual thickness of the current wafer after polishing; THK_Offset_spec is the thickness compensation value; RR[n] is the actual polishing rate of the current wafer.

[0024] Optionally, in the polishing control method of the chemical mechanical polishing process, the thickness compensation value THK_Offset_spec is set to 0.

[0025] Optionally, in the polishing control method of the chemical mechanical polishing process, the formula involved in the third step is:

[0026] The grinding time of the next wafer = the preset grinding thickness of the next wafer ÷ the expected grinding rate of the next wafer.

[0027] Optionally, in the polishing control method of the chemical mechanical polishing process, the actual polishing rate RR[n] of the current wafer is calculated as follows:

[0028] RR[n]=(pre_measure-post_measure)÷t;

[0029] Among them, pre_measure is the thickness value of the current wafer before measurement; post_measure is the thickness value of the current wafer after measurement; t is the grinding time of the current wafer.

[0030] Optionally, in the polishing control method of the chemical mechanical polishing process, the calculation formula for the polishing time of the current wafer is:

[0031] t=(pre_measure-THK_Target)÷RR_Act;

[0032] Where pre_measure is the thickness of the current wafer before measurement; THK_Target is the target thickness of any wafer in the same batch after grinding; RR_Act is the ideal grinding rate of the current wafer.

[0033] Optionally, in the polishing control method of the chemical mechanical polishing process, the coefficient x for preventing a sudden change in polishing rate ranges from 0 to 1.

[0034] The technical solution of this application has at least the following advantages:

[0035] In the polishing control method of the chemical mechanical polishing process provided in the present application, a polishing rate compensation formula is set in the IAPC system and used to compensate the ideal polishing rate of the current wafer to obtain the expected polishing rate of the next wafer. Subsequently, the polishing time of the next wafer is obtained according to the expected polishing rate of the next wafer and the preset polished thickness, and CMP is performed on the next wafer according to the polishing time of the next wafer. The present application adjusts the expected polishing rate of the next wafer in real time by setting a polishing rate compensation formula, so that the actual polished thickness of the next wafer is the same as the preset polished thickness, thereby achieving the stability of the polishing thickness of each wafer in the same batch, and solving the problem of deviation (too thick or too thin) between the actual polishing thickness of the wafer and the preset polishing thickness of the wafer caused by abnormal IAPC adjustment due to the influence of the service life of consumables. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the specific implementation methods of the present application or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the specific implementation methods or the description of the prior art. Obviously, the drawings described below are some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0037] Figure 1 4 is a flow chart of a polishing control method for a chemical mechanical polishing process according to an embodiment of the present invention. DETAILED DESCRIPTION

[0038] The following is a clear and complete description of the technical solutions in this application in conjunction with the accompanying drawings. Obviously, the embodiments described are part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of this application.

[0039] In the description of this application, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate the description of this application and simplify the description. They do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0040] In the description of this application, it should be noted that, unless otherwise expressly specified or limited, the terms "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; they can refer to internal connections between two components; they can refer to wireless connections or wired connections. Those skilled in the art will understand the specific meanings of the above terms in this application based on the specific circumstances.

[0041] In addition, the technical features involved in the different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0042] An embodiment of the present application provides a polishing control method for a chemical mechanical polishing process, which is used at least to control the chemical mechanical polishing of a current wafer and a next wafer in a batch.

[0043] Specifically, the control method is at least used to control the chemical mechanical polishing of the same medium on the current wafer and the same medium on the next wafer. The same medium on the wafer can be a single medium layer or a stack of multiple medium layers of the same material.

[0044] In this embodiment, the same medium on the current wafer and the same medium on the next wafer are silicon dioxide layers on the wafers.

[0045] refer to Figure 1 , Figure 1 1 is a flow chart of a polishing control method for a chemical mechanical polishing process according to an embodiment of the present invention, wherein the polishing control method for the chemical mechanical polishing process comprises:

[0046] The first step S1: setting a polishing rate compensation formula in the IAPC system;

[0047] Second step S2: using the grinding rate compensation formula, compensating the ideal grinding rate of the current wafer to obtain the expected grinding rate of the next wafer;

[0048] Step S3: obtaining a grinding time for the next wafer according to the expected grinding rate of the next wafer and the preset grinding thickness of the next wafer;

[0049] Step S4: performing chemical mechanical polishing on the next wafer using the IAPC system according to the polishing time of the next wafer;

[0050] The fifth step S5: determine whether there are wafers to be ground in this batch. If there are wafers to be ground in this batch, return to the second step S2 to the fourth step S4 and execute until all wafers in this batch are ground.

[0051] Specifically, the polishing control method of the chemical mechanical polishing process includes:

[0052] First, perform the first step S1: set a grinding rate compensation formula in the IAPC system. Specifically, the grinding rate compensation formula is as follows:

[0053] RR_Offset=x*Sign(THK_Target,THK_AvePost,THK_Offset_spec)*ABS(RR[n]-RR_Act);

[0054] Wherein, RR_Offset is the grinding rate compensation value; x is a coefficient to prevent sudden changes in grinding rate; THK_Target is the target thickness of any wafer in the same batch after grinding; THK_AvePost is the actual thickness of the current wafer after grinding; THK_Offset_spec is the thickness compensation value; RR[n] is the actual grinding rate of the current wafer; RR_Act is the ideal grinding rate of the current wafer.

[0055] Furthermore, the actual polishing rate RR[n] of the current wafer is calculated as follows:

[0056] RR[n]=(pre_measure-post_measure)÷t;

[0057] Among them, pre_measure is the thickness value of the current wafer before measurement; post_measure is the thickness value of the current wafer after measurement; t is the grinding time of the current wafer.

[0058] Furthermore, the calculation formula for the grinding time of the current wafer is:

[0059] t=(pre_measure-THK_Target)÷RR_Act;

[0060] Where pre_measure is the thickness of the current wafer before measurement; THK_Target is the target thickness of any wafer in the same batch after grinding; RR_Act is the ideal grinding rate of the current wafer.

[0061] In this embodiment, the coefficient x for preventing a sudden change in the polishing rate ranges from 0 to 1.

[0062] Then, a second step S2 is performed: using the grinding rate compensation formula, compensating the ideal grinding rate of the current wafer to obtain the expected grinding rate of the next wafer, wherein the obtained expected grinding rate of the next wafer is the ideal grinding rate of the next wafer.

[0063] The formula involved in the second step S2 is:

[0064] RR_Model=RR_Act+RR_Offset;

[0065] Among them, RR_Model is the expected polishing rate of the next wafer; RR_Act is the ideal polishing rate of the current wafer; RR_Offset is the polishing rate compensation value.

[0066] Preferably, Sign(THK_Target,THK_AvePost,THK_Offset_spec) is configured as:

[0067] If (THK_Target - THK_AvePost) > THK_Offset_spec, then Sign(THK_Target, THK_AvePost, THK_Offset_spec) takes the value 1;

[0068] If (THK_Target - THK_AvePost) < (-THK_Offset_spec), then Sign(THK_Target, THK_AvePost, THK_Offset_spec) takes the value -1;

[0069] If (-THK_Offset_spec)≤(THK_Target-THK_AvePost)≤THK_Offset_spec, then Sign(THK_Target,THK_AvePost,THK_Offset_spec) takes the value 0.

[0070] In this embodiment, the thickness compensation value THK_Offset_spec is set to 0.

[0071] Preferably, according to the specific configuration of the Sign(THK_Target,THK_AvePost,THK_Offset_spec) function, the formula involved in the second step S2 is:

[0072] RR_Model=RR_Act+x*Sign(THK_Target,THK_AvePost,THK_Offset_spec)*A BS(RR[n]-RR_Act);

[0073] Where RR_Model is the expected polishing rate of the next wafer, RR_Act is the ideal polishing rate of the current wafer, x is a coefficient to prevent sudden changes in the polishing rate; THK_Target is the target thickness of any wafer in the same batch after polishing; THK_AvePost is the actual thickness of the current wafer after polishing; THK_Offset_spec is the thickness compensation value; RR[n] is the actual polishing rate of the current wafer.

[0074] When the first wafer of this batch undergoes the chemical mechanical polishing process, the parameters of the current wafer can be collected by the IAPC system during the chemical mechanical polishing process of the first wafer. The parameters of the current wafer include at least: actual polishing rate, ideal polishing rate, etc.

[0075] Next, a third step S3 is performed: obtaining the grinding time of the next wafer according to the expected grinding rate of the next wafer and the preset grinding thickness of the next wafer.

[0076] Preferably, the formula involved in the third step S3 is: grinding time of the next wafer = preset grinding thickness of the next wafer ÷ expected grinding rate of the next wafer.

[0077] Furthermore, a fourth step S4 is performed: chemical mechanical polishing is performed on the next wafer using the IAPC system based on the polishing time of the next wafer, wherein the actual polishing rate of the next wafer = (actual thickness value before measurement - actual thickness value after measurement) / polishing time of the next wafer.

[0078] Finally, execute the fifth step S5: determine whether there are wafers to be polished in this batch. If there are still wafers to be polished in this batch, return to execute the second step S2 to the fourth step S4 until all the wafers in this batch are polished; if all the wafers in this batch are polished, stop the chemical mechanical polishing process.

[0079] It is worth noting that if there are wafers remaining in the batch to be polished, it is necessary to return to step S2 through step S4. In the second step S2 of the new round of steps S2 through S4, the next wafer in step S4 of the previous round is automatically replaced with the current wafer in step S2 of the new round. In this embodiment, in step S2 of the new round, the ideal polishing rate RR_Act of the current wafer is equal to the expected polishing rate RR_Model of the next wafer in step S4 of the previous round; the actual polishing rate RR[n] of the current wafer is equal to the actual polishing rate of the next wafer in step S4 of the previous round.

[0080] In the present application, a grinding rate compensation formula is set in the IAPC system and used to compensate for the ideal grinding rate of the current wafer to obtain the expected grinding rate of the next wafer. Subsequently, the grinding time of the next wafer is obtained based on the expected grinding rate of the next wafer and the preset grinding thickness, and the next wafer is subjected to CMP based on the grinding time of the next wafer. The present application adjusts the expected grinding rate of the next wafer in real time by setting a grinding rate compensation formula, so that the actual grinding thickness of the next wafer is the same as the preset grinding thickness, thereby achieving the stability of the grinding thickness of each wafer in the same batch, and solving the problem of deviation (too thick or too thin) between the actual grinding thickness of the wafer and the preset grinding thickness of the wafer caused by abnormal IAPC adjustment due to the influence of the service life of consumables.

[0081] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of this application.

Claims

1. A polishing control method for a chemical mechanical polishing process, characterized in that: include: Step 1: Set up a grinding rate compensation formula in the IAPC system; Step 2: Using the grinding rate compensation formula, the ideal grinding rate of the current wafer is compensated to obtain the expected grinding rate of the next wafer; Step 3: Obtaining a grinding time for the next wafer based on the expected grinding rate of the next wafer and the preset grinding thickness of the next wafer; Step 4: performing chemical mechanical polishing on the next wafer using the IAPC system according to the polishing time of the next wafer; Step 5: Determine whether there are wafers to be ground in this batch. If there are wafers to be ground in this batch, return to execute the second step to the fourth step until all wafers in this batch are ground.

2. The polishing control method of the chemical mechanical polishing process according to claim 1, characterized in that: The grinding rate compensation formula is as follows: RR_Offset=x*Sign(THK_Target,THK_AvePost,THK_Offset_spec)*ABS(RR[n]-RR_Act); Wherein, RR_Offset is the grinding rate compensation value; x is a coefficient to prevent sudden changes in grinding rate; THK_Target is the target thickness of any wafer in the same batch after grinding; THK_AvePost is the actual thickness of the current wafer after grinding; THK_Offset_spec is the thickness compensation value; RR[n] is the actual grinding rate of the current wafer; RR_Act is the ideal grinding rate of the current wafer.

3. The polishing control method of the chemical mechanical polishing process according to claim 2, characterized in that: Sign(THK_Target,THK_AvePost,THK_Offset_spec) is configured as: If (THK_Target - THK_AvePost) > THK_Offset_spec, then Sign(THK_Target, THK_AvePost, THK_Offset_spec) takes the value 1; If (THK_Target - THK_AvePost) < (-THK_Offset_spec), then Sign(THK_Target, THK_AvePost, THK_Offset_spec) takes the value -1; If (-THK_Offset_spec)≤(THK_Target-THK_AvePost)≤THK_Offset_spec, then Sign(THK_Target,THK_AvePost,THK_Offset_spec) takes the value 0.

4. The polishing control method of the chemical mechanical polishing process according to claim 1, characterized in that: The formula involved in the second step is: RR_Model=RR_Act+RR_Offset; Among them, RR_Model is the expected polishing rate of the next wafer; RR_Act is the ideal polishing rate of the current wafer; RR_Offset is the polishing rate compensation value.

5. The polishing control method of the chemical mechanical polishing process according to claim 3, characterized in that: The formula involved in the second step is: RR_Model=RR_Act+x*Sign(THK_Target,THK_AvePost,THK_Offset_spec)*ABS(RR[n]-RR_Act); Where RR_Model is the expected polishing rate of the next wafer, RR_Act is the ideal polishing rate of the current wafer, x is a coefficient to prevent sudden changes in the polishing rate; THK_Target is the target thickness of any wafer in the same batch after polishing; THK_AvePost is the actual thickness of the current wafer after polishing; THK_Offset_spec is the thickness compensation value; RR[n] is the actual polishing rate of the current wafer.

6. The polishing control method of the chemical mechanical polishing process according to claim 2, wherein: The thickness compensation value THK_Offset_spec is set to 0.

7. The polishing control method of the chemical mechanical polishing process according to claim 1, characterized in that: The formula involved in the third step is: The grinding time of the next wafer = the preset grinding thickness of the next wafer ÷ the expected grinding rate of the next wafer.

8. The polishing control method of the chemical mechanical polishing process according to claim 2, characterized in that: The calculation formula for the actual polishing rate RR[n] of the current wafer is: RR[n]=(pre_measure-post_measure)÷t; Among them, pre_measure is the thickness value of the current wafer before measurement; post_measure is the thickness value of the current wafer after measurement; t is the grinding time of the current wafer.

9. The polishing control method of the chemical mechanical polishing process according to claim 8, characterized in that: The calculation formula for the grinding time of the current wafer is: t=(pre_measure-THK_Target)÷RR_Act; Where pre_measure is the thickness of the current wafer before measurement; THK_Target is the target thickness of any wafer in the same batch after grinding; RR_Act is the ideal grinding rate of the current wafer.

10. The polishing control method of the chemical mechanical polishing process according to claim 2, characterized in that: The coefficient x for preventing a sudden change in the grinding rate ranges from 0 to 1.

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