CN113953969A - Method for optimizing polishing pressure on line - Google Patents

Method for optimizing polishing pressure on line Download PDF

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CN113953969A
CN113953969A CN202111313760.4A CN202111313760A CN113953969A CN 113953969 A CN113953969 A CN 113953969A CN 202111313760 A CN202111313760 A CN 202111313760A CN 113953969 A CN113953969 A CN 113953969A
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CN113953969B (en
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张康
李婷
吴燕林
崔凯
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Beijing Jingyi Precision Technology Co ltd
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Beijing Semicore Microelectronics Equipment Co Ltd
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
    • B24B37/00—Lapping machines or devices; Accessories
    • B24B37/04—Lapping machines or devices; Accessories designed for working plane surfaces
    • B24B37/07—Lapping machines or devices; Accessories designed for working plane surfaces characterised by the movement of the work or lapping tool
    • B24B37/10—Lapping machines or devices; Accessories designed for working plane surfaces characterised by the movement of the work or lapping tool for single side lapping
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
    • B24B37/00—Lapping machines or devices; Accessories
    • B24B37/005—Control means for lapping machines or devices
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
    • B24B49/00—Measuring or gauging equipment for controlling the feed movement of the grinding tool or work; Arrangements of indicating or measuring equipment, e.g. for indicating the start of the grinding operation
    • B24B49/16—Measuring or gauging equipment for controlling the feed movement of the grinding tool or work; Arrangements of indicating or measuring equipment, e.g. for indicating the start of the grinding operation taking regard of the load
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    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/02002—Preparing wafers
    • H01L21/02005—Preparing bulk and homogeneous wafers
    • H01L21/02008—Multistep processes
    • H01L21/0201—Specific process step
    • H01L21/02013—Grinding, lapping
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Abstract

The invention provides a method for optimizing polishing pressure on line, which comprises the following steps: acquiring a reference polishing curve, wherein the reference polishing curve is a curve of the change of the reference polishing removal rate along with the polishing position; obtaining a first reference normalization coefficient B according to the reference polishing curve1Normalization coefficient B to Nth referenceN(ii) a Polishing the w wafer by using a polishing head; obtaining the w waferThe kth characterization normalization coefficient beta (k) of the removal rate of the kth wafer area ofw(ii) a Providing a prediction model, wherein the prediction model is suitable for exerting pressure P (k) on a k wafer area of a w wafer according to a k pressure exerting areawAnd the pressure compensation coefficient alpha (k) of the kth wafer area of the w +1 th waferw+1Acquiring the predicted pressure P (k) exerted by the kth pressure exerting area on the kth wafer area of the w +1 waferw+1. The method can adjust the polishing pressure on line and is simplified.

Description

Method for optimizing polishing pressure on line
Technical Field
The invention relates to the technical field of semiconductors, in particular to a method for optimizing polishing pressure on line.
Background
With the development of semiconductor manufacturing technology, the requirements of Chemical Mechanical Planarization (CMP) of wafers with a thickness of 200mm or more on the control accuracy and real-time feedback of parameters such as the surface topography and non-uniformity (Nu) of an in-chip (WIW) surface are higher and higher. In the CMP Process, a method of fixing polishing parameters such as pressure and rotation speed and changing polishing duration is generally adopted to perform batch production, polishing duration (or polishing rate) of each batch (Lot to Lot) or each wafer (wafer to wafer) is optimized and calculated through a specific algorithm of an apc (advanced Process control) system and then sent to a machine end to perform a polishing Process, when the surface morphology of the removal rate DOEs not meet the requirement, the Process parameters are generally changed through manual intervention to adjust the surface morphology so that the surface morphology meets the requirement, or a WIWAPC system is adopted on a 300mm related machine to adjust the pressure in the wafer through a certain amount of experimental Design (DOE) parameters.
The existing method for adjusting the surface morphology of the removal rate through manual intervention has certain hysteresis and certain dependence on the experience of engineers, and cannot perform optimized adjustment on abnormal wafers in time; the WIWAPC system algorithm adopted on the related machine is complex, and a certain amount of parameter experiment data accumulation is needed.
Disclosure of Invention
Therefore, the technical problem to be solved by the present invention is to overcome the problems of hysteresis and complexity of adjusting polishing pressure by a pressure monitoring system in the prior art, thereby providing a method for optimizing polishing pressure on line.
The invention provides a method for optimizing polishing pressure on line, which comprises the following steps: providing a polishing head, wherein the polishing head is suitable for polishing the wafer; for the polishing headPartitioning is carried out, wherein the polishing head comprises a first pressure application area to an Nth pressure application area which are arranged from inside to outside in the radial direction, N is an integer larger than or equal to 2, the wafer comprises a first wafer area to an Nth wafer area, the kth wafer area corresponds to the kth pressure application area, and k is an integer larger than or equal to 1 and smaller than or equal to N; acquiring a reference polishing curve, wherein the reference polishing curve is a curve of the change of the reference polishing removal rate along with the polishing position; obtaining a first reference normalization coefficient B according to the reference polishing curve1Normalization coefficient B to Nth referenceNK < th > reference normalization coefficient BkThe ratio of the average value of the reference polishing removal rate corresponding to the kth pressure application area to the average value of the reference polishing removal rate corresponding to each area of the polishing head is obtained; polishing the w wafer by using a polishing head; obtaining the kth characterization normalization coefficient beta (k) of the removal rate of the kth wafer area of the w waferw(ii) a Providing a prediction model, wherein the prediction model is suitable for exerting pressure P (k) on a k wafer area of a w wafer according to a k pressure exerting areawAnd the pressure compensation coefficient alpha (k) of the kth wafer area of the w +1 th waferw+1Acquiring the predicted pressure P (k) exerted by the kth pressure exerting area on the kth wafer area of the w +1 waferw+1；α(k)w+1＝λ(k)w*(β(k)w-Bk)+(1-λ(k)w)α(k)w；P(k)w+1＝P(k)w·(1+α(k)w+1) (ii) a Wherein, λ (k)wThe influence weight coefficient of the kth wafer area of the w wafer on the kth wafer area of the w +1 wafer is 0<λ(k)w<1；α(k)wAnd the pressure compensation coefficient of the w wafer is obtained.
Optionally, a kth characterization normalization coefficient β (k) for obtaining a removal rate of a kth wafer region of a w-th waferwComprises the following steps: respectively selecting a plurality of measuring points from a first wafer area to an Nth wafer area of a w wafer, and respectively obtaining a normalization coefficient of the removal rate of each measuring point of the w wafer; obtaining a kth characterization normalization coefficient beta (k) of the removal rate of the kth wafer area of the w wafer according to the normalization coefficient of the removal rate of each measurement point in the kth wafer area of the w waferw。
Optionally, the kth wafer area of the w wafer is divided intoThe mean value of the normalized coefficients of the removal rates of the measurement points in (b) is used as the kth characterization normalized coefficient beta (k) of the removal rate of the kth wafer area of the w waferw(ii) a Or taking the maximum value of the absolute difference value between the removal rate of the measuring point in the kth wafer area of the w wafer and 1 as the kth characterization normalization coefficient beta (k) of the removal rate of the kth wafer area of the w waferw。
Optionally, the influence weight coefficients corresponding to the first wafer area to the nth wafer area of the w wafer are all equal.
Optionally, the influence weight coefficients corresponding to the first wafer area to the nth wafer area of the w wafer are all at least partially unequal.
Optionally, the influence weight coefficients corresponding to the first wafer area to the nth wafer area of the w-th wafer are increased progressively.
Optionally, N is an integer greater than or equal to 4, the wafer includes a central region and an edge region, the central region includes a first wafer region to an L-th wafer region, the edge region includes an L + 1-th wafer region to an N-th wafer region, and L is an integer greater than or equal to 2 and less than or equal to N-1; the change rate of the influence weight coefficient from the first wafer area to the L wafer area of the w wafer is smaller than the change rate of the influence weight coefficient from the L +1 wafer area to the N wafer area of the w wafer.
Optionally, the total area of the first wafer region to the lth wafer region occupies 68% to 72% of the total area of the wafer.
Alternative, λ (k)wThe value range of (A) is 0.5-0.8.
Alternative, λ (k)wThe value range of (A) is 0.6-0.7.
The technical scheme of the invention has the following beneficial effects:
the method for optimizing polishing pressure on line provided by the technical scheme of the invention is characterized in that a prediction model is arranged, and the prediction model is suitable for applying pressure P (k) to a kth wafer area of a w wafer according to a kth pressure application areawAnd the pressure compensation coefficient alpha (k) of the kth wafer area of the w +1 th waferw+1Acquiring the predicted pressure P (k) exerted by the kth pressure exerting area on the kth wafer area of the w +1 waferw+1；α(k)w+1＝λ(k)w*(β(k)w-Bk)+(1-λ(k)w)α(k)w；P(k)w+1＝P(k)w·(1+α(k)w+1) (ii) a The pressure compensation coefficient can comprehensively consider the influence of the current wafer and the previous wafer on the next wafer, so that the accuracy of the predicted value of the pressure on the next wafer is improved. The method can adjust the polishing pressure on line and is simplified.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.
FIG. 1 is a graph illustrating a trend of a removal rate change during a polishing process for a wafer;
fig. 2 is a flowchart of a method for online optimizing polishing pressure according to an embodiment of the present invention.
Detailed Description
As shown in fig. 1, the BL curve is a target curve of the removal rate. In the process of polishing the wafer, the wafer is measured at different stages, for convenience of description, a normalized curve of the removal rate measured at the initial polishing time (corresponding to 0hrs) is labeled as curve 1, a normalized curve of the removal rate measured after grinding for 20 hours along with the change of the polishing position is labeled as curve 2, and a normalized curve of the removal rate measured after grinding for 40 hours along with the change of the polishing position is labeled as curve 3. After normalization processing of measurement results, differences between actual curves and BL curves in different areas can be quantified. It can be found that, when the removal rate variation factor is excluded and the polishing time is changed, the removal rate corresponding to the center position of the wafer tends to be increased, and the removal rate corresponding to the edge of the wafer (area with coordinates of ± 85 mm) tends to be increased. The method for adjusting the surface morphology of the removal rate through manual intervention has certain hysteresis and certain dependence on the experience of engineers, and cannot perform optimized adjustment on abnormal wafers in time; the WIWAPC system algorithm adopted on the related machine is complex, and a certain amount of parameter experiment data accumulation is needed.
The invention provides a method for optimizing polishing pressure on line, which can adjust polishing pressure on line and is simplified.
The technical solutions of the present invention will be described clearly and completely with reference to the accompanying drawings, and it should be understood that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; the two elements may be directly connected or indirectly connected through an intermediate medium, or may be communicated with each other inside the two elements, or may be wirelessly connected or wired connected. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.
In addition, the technical features involved in the different embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
An embodiment of the present invention provides a method for optimizing polishing pressure on line, which includes the following steps, with reference to fig. 2:
step S1, providing a polishing head, wherein the polishing head is suitable for polishing the wafer;
step S2, the polishing head is partitioned, the polishing head comprises a first pressure application area to an Nth pressure application area which are arranged from inside to outside in the radial direction, N is an integer larger than or equal to 2, the wafer comprises a first wafer area to an Nth wafer area, the kth wafer area corresponds to the kth pressure application area, and k is an integer larger than or equal to 1 and smaller than or equal to N;
step S3, acquiring a reference polishing curve, wherein the reference polishing curve is a change curve of the reference polishing removal rate along with the polishing position;
step S4, obtaining a first reference normalization coefficient B according to the reference polishing curve1Normalization coefficient B to Nth referenceNK < th > reference normalization coefficient BkThe ratio of the average value of the reference polishing removal rate corresponding to the kth pressure application area to the average value of the reference polishing removal rate corresponding to each area of the polishing head is obtained;
step S5, polishing the w wafer by using a polishing head;
step S6, obtaining the k-th representation normalization coefficient beta (k) of the removal rate of the k-th wafer area of the w-th waferw；
Step S7, providing a prediction model, wherein the prediction model is suitable for applying pressure P (k) to the kth wafer area of the w wafer according to the kth pressure application areawAnd the pressure compensation coefficient alpha (k) of the kth wafer area of the w +1 th waferw+1Acquiring the predicted pressure P (k) exerted by the kth pressure exerting area on the kth wafer area of the w +1 waferw+1。
In step S1, the polishing head is used for polishing and grinding the wafer, specifically, during the process of polishing and grinding the wafer, the wafer is fixed by the polishing surface of the polishing head and is pressed against the polishing pad.
In step S2, different types of polishing heads corresponding to different polishing machines are zoned, for example, for a polishing head having a polishing surface with a diameter of 200mm, the polishing heads are divided into a first pressure applying region, a second pressure applying region, and a third pressure applying region arranged from inside to outside in the radial direction, and for a polishing head having a polishing surface with a diameter of 300mm, the polishing heads are divided into a first pressure applying region, a second pressure applying region, a third pressure applying region, a fourth pressure applying region, a fifth pressure applying region, a sixth pressure applying region, and a seventh pressure applying region arranged from inside to outside in the radial direction. In this embodiment, the case where N is equal to 5 is taken as an example, and accordingly, the polishing head is divided into a first pressure applying region, a second pressure applying region, a third pressure applying region, a fourth pressure applying region, and a fifth pressure applying region arranged from inside to outside in the radial direction. It should be noted that the zoning of the polishing head can be performed as required in actual situations, and is not limited by the diameter of the polishing surface. Generally, the larger the diameter of the polishing surface is, the larger the number of divisions of the polishing head is.
In step S3, a reference polishing curve is obtained, which is a curve of the reference polishing removal rate with the polishing position, and specifically, a database is provided, which stores data of the removal rates of different positions of each test wafer that has been polished in an actual process, where the removal rates of different positions of each test wafer that has been polished refer to: thickness variation of the test wafer before polishing and after polishing at a non-test location; and filtering the data in the database to obtain a plurality of reference data points, averaging the removal rates of the reference data points at the same position, and then drawing a reference polishing curve according to the reference data. The filtering process of the data in the database refers to: and eliminating the data exceeding the upper process line and the lower process limit.
In step S4, the kth reference normalization coefficient BkIs the ratio of the average value of the reference polishing removal rates corresponding to the kth pressure application area to the average value of the reference polishing removal rates corresponding to the areas of the polishing head. In particular, N is equal to 5, a first reference normalization factor B1A second reference normalization coefficient B is the ratio of the average value of the reference polishing removal rates corresponding to the first pressure application area to the average value of the reference polishing removal rates corresponding to the areas of the polishing head2Average value of the reference polishing removal rates corresponding to the second pressure applying regionsThe ratio of the average values of the reference polishing removal rates corresponding to the regions of the polishing head, and a third reference normalization coefficient B3A fourth reference normalization coefficient B is the ratio of the average value of the reference polishing removal rate corresponding to the third pressure application area to the average value of the reference polishing removal rate corresponding to each area of the polishing head4A fifth reference normalization coefficient B is the ratio of the average value of the reference polishing removal rates corresponding to the fourth pressure application area to the average value of the reference polishing removal rates corresponding to the areas of the polishing head5Is the ratio of the average value of the reference polishing removal rates corresponding to the fifth pressing zone to the average value of the reference polishing removal rates corresponding to the respective zones of the polishing head.
In step S5, during the process of polishing the w wafer by the polishing head, the kth pressing area polishes the kth wafer area of the w wafer. When the N is equal to 5, the first pressure application area polishes a first wafer area of a w wafer, the second pressure application area polishes a second wafer area of the w wafer, the third pressure application area polishes a third wafer area of the w wafer, the fourth pressure application area polishes a fourth wafer area of the w wafer, and the fifth pressure application area polishes a fifth wafer area of the w wafer.
In step S6, a kth characterization normalization coefficient β (k) of the removal rate of the kth wafer area of the w-th wafer is obtainedwComprises the following steps: respectively selecting a plurality of measuring points from a first wafer area to an Nth wafer area of a w wafer, and respectively obtaining a normalization coefficient of the removal rate of each measuring point of the w wafer; obtaining a kth characterization normalization coefficient beta (k) of the removal rate of the kth wafer area of the w wafer according to the normalization coefficient of the removal rate of each measurement point in the kth wafer area of the w waferw。
In one embodiment, the mean value of the normalized coefficients of the removal rate of each measurement point in the kth wafer area of the w wafer is used as the kth characterization normalized coefficient beta (k) of the removal rate of the kth wafer area of the w waferw。
In another embodiment, the maximum value of the absolute difference between the removal rate of the measurement point in the kth wafer area of the w wafer and 1 is taken as the kth wafer area of the w waferKth characterization normalization coefficient of removal rate beta (k)w。
The removal rate of each measuring point in the kth wafer area of the w wafer refers to: the ratio of the thickness difference of each measuring point in the kth wafer area of the w wafer before and after polishing to the polishing time.
The method for obtaining the normalization coefficient of the removal rate of each measuring point in the kth wafer area of the w wafer comprises the step of taking the ratio of the removal rate of any measuring point in the kth wafer area to the average removal rate of the whole w wafer as the normalization coefficient of the removal rate of the measuring point in the kth wafer area of the w wafer. The average removal rate of the whole wafer of the w-th wafer is as follows: the average removal of the entire w wafer divided by the polishing time.
In step S7, α (k)w+1＝λ(k)w*(β(k)w-Bk)+(1-λ(k)w)α(k)w；P(k)w+1＝P(k)w·(1+α(k)w+1) (ii) a Wherein, λ (k)wThe influence weight coefficient of the kth wafer area of the w wafer on the kth wafer area of the w +1 wafer is 0<λ(k)w<1；α(k)wPressure compensation coefficient for w wafer, P (k)wThe pressure applied to the kth wafer area of the w wafer by the kth pressure application area, alpha (k)w+1Pressure compensation coefficient of kth wafer area for w +1 th wafer, P (k)w+1And (4) applying the predicted pressure to the kth wafer area of the w +1 th wafer for the kth pressure applying area.
In one embodiment, the influence weight coefficients corresponding to the first wafer area to the Nth wafer area of the w wafer are all equal, so that the calculation process is simplified.
In another embodiment, the influence weight coefficients corresponding to the first wafer area to the nth wafer area of the w wafer are all at least partially unequal, thereby improving the prediction accuracy.
In a specific embodiment, the influence weight coefficients corresponding to the first wafer area to the nth wafer area of the w-th wafer are increased progressively, further improving the prediction accuracy.
In a specific embodiment, N is an integer greater than or equal to 4, the wafer includes a central region and an edge region, the central region includes a first wafer region to an L-th wafer region, the edge region includes an L + 1-th wafer region to an N-th wafer region, L is an integer greater than or equal to 2 and less than or equal to N-1; the change rate of the influence weight coefficient from the first wafer area to the L wafer area of the w wafer is smaller than the change rate of the influence weight coefficient from the L +1 wafer area to the N wafer area of the w wafer, and the prediction precision is further improved.
The total area of the first wafer area to the L-th wafer area occupies 68-72% of the total area of the wafer.
λ(k)wThe value range of (A) is 0.5-0.8. Lambda (k)wThe value range of (A) is 0.6-0.7.
The predictive model is explained below in a specific iterative process.
Setting N equal to 5, and obtaining a first reference normalization coefficient B according to the reference polishing curve1Normalization coefficient B to Nth referenceNIn particular, B1＝0.85,B2＝1.1，B3＝1.05，B4＝1，B5＝1.05。
The pressure applied when the first wafer is polished is taken as the reference pressure PBLThe reference pressure at each time of the regions of the first wafer is the same, i.e., P (1)1＝P(2)1＝P(3)1＝P(4)1＝P(5)1In one particular embodiment, with P (1)1＝P(2)1＝P(3)1＝P(4)1＝P(5)15psi is illustrated as an example.
After the first wafer is polished, acquiring the kth characterization normalization coefficient beta (k) of the first waferwWherein, the first characterization normalization coefficient beta (1) of the first wafer10.95, second characteristic normalization factor β (2) of the first wafer1Third characterization normalization factor β (3) for the first wafer ═ 1.051The fourth characteristic normalization factor β (4) of the first wafer, 11The fifth characterization normalization factor β (5) for the first wafer, 11＝1。
Pressure compensation coefficient alpha (k) of first wafer1Is zero. Influence weight coefficient lambda (k) of kth wafer area of the first wafer on kth wafer area of the second wafer1Is 0.7. Specifically, the influence weight coefficient lambda (1) of the first wafer area of the first wafer on the first wafer area of the second wafer10.7, the second wafer area of the first wafer has an influence weight coefficient lambda (2) on the second wafer area of the second wafer10.7, the weight factor λ (3) of the influence of the third circular area of the first wafer on the third circular area of the second wafer10.7, the fourth wafer area of the first wafer has an influence weight coefficient lambda (4) on the fourth wafer area of the second wafer10.7, the fifth wafer area of the first wafer has an influence weight coefficient lambda (5) on the fifth wafer area of the second wafer1Is 0.7.
According to the formula α (k)w+1＝λ(k)w*(β(k)w-Bk)+(1-λ(k)w)α(k)wObtaining the pressure compensation coefficient alpha (k) of the kth wafer area of the second wafer2The pressure supplement coefficient alpha (1) of the first wafer area of the second wafer is obtained through calculation20.7 x (0.95-0.85) 0.07, pressure supplement coefficient α (2) of the second wafer region of the second wafer20.7 x (1.05-1.1) 0.035, pressure supplement coefficient α (3) of the third wafer area of the second wafer20.7 x (1-1.05) 0.035, pressure supplement coefficient α (4) of the fourth wafer area of the second wafer20.7 x (1-1) 0, pressure supplement coefficient alpha (5) of the fifth wafer area of the second wafer2＝0.7*(1-1.05)＝-0.035。
According to the formula P (k)w+1＝P(k)w·(1+α(k)w+1) Obtaining the predicted pressure P (k) exerted by the kth pressure exerting area on the kth wafer area of the second wafer2The predicted pressure P (1) applied to the first wafer area of the second wafer is calculated2＝P(1)1*(1+α(1)2) Predicted pressure P (2) applied to the second wafer region of the second wafer at 5psi (1+0.07) ═ 5.35psi2＝P(2)1*(1+α(2)2) Predicted pressure P (3) applied to third wafer region of second wafer at 5psi (1-0.035) 4.825psi2＝P(3)1*(1+α(3)2) Predicted pressure P (4) applied to the fourth wafer area of the second wafer at 4.825psi2＝P(4)1*(1+α(4)2) Predicted pressure P (5) applied to fifth wafer area of second wafer 5psi2＝P(5)1*(1+α(5)2)＝4.825psi。
For the first wafer region of the second wafer at the predicted pressure P (1)2Polishing the second wafer area to a predicted pressure P (2)2Polishing the third wafer area of the second wafer at the predicted pressure P (3)2Polishing to a fourth wafer region of the second wafer at the predicted pressure P (4)2Polishing to obtain a fifth wafer region of the second wafer at the predicted pressure P (5)2And then polishing is carried out. After polishing the second wafer, obtaining a kth characterization normalization coefficient beta (k) of the removal rate of the kth wafer area of the second wafer2Measuring and calculating to obtain beta (1) through the measuring point in the second wafer2＝0.8，β(2)2＝1.2，β(3)2＝1.05，β(4)2＝1.1，β(5)2＝1。
Influence weight coefficient lambda (k) of kth wafer area of the second wafer on kth wafer area of the third wafer2Is 0.7. Specifically, the influence weight coefficient lambda (1) of the first wafer area of the second wafer on the first wafer area of the third wafer20.7, the second wafer area of the second wafer has an influence weight coefficient lambda (2) on the second wafer area of the third wafer20.7, the third wafer region of the second wafer has a weight factor λ (3) on the third wafer region of the third wafer20.7, the fourth wafer area of the second wafer has an influence weight coefficient lambda (4) on the fourth wafer area of the third wafer20.7, the fifth wafer area of the second wafer has an influence weight coefficient lambda (5) on the fifth wafer area of the third wafer2Is 0.7.
According to the formula α (k)w+1＝λ(k)w*(β(k)w-Bk)+(1-λ(k)w)α(k)wObtaining the pressure compensation coefficient alpha (k) of the kth wafer area of the third wafer3The pressure supplement coefficient alpha (1) of the first wafer area of the third wafer is obtained through calculation3＝λ(1)2*(β(1)2-B1)+(1-λ(1)2) 0.7 x (0.8-0.85) +0.3 x 0.07 x-0.014, pressure supplement coefficient α (2) of the second wafer area of the third wafer3＝λ(2)2*(β(2)2-B1)+(1-λ(2)2) 0.0595, pressure supplement factor α (3) for the third wafer region of the third wafer3-0.0105, pressure supplement coefficient α (4) of fourth wafer zone of third wafer30.07, pressure supplement coefficient alpha (5) of the fifth wafer area of the third wafer3＝-0.0455。
According to the formula P (k)w+1＝P(k)w·(1+α(k)w+1) Obtaining the predicted pressure P (k) exerted by the kth pressure exerting area on the kth wafer area of the third wafer3Predicted pressure P (1) applied to first wafer area of third wafer3＝P(1)2*(1+α(1)3) 5.2751psi, predicted pressure P (2) applied to the second wafer area of the third wafer3＝P(2)2*(1+α(2)3) Predicted pressure P (3) applied to third wafer region of third wafer at 5.11psi3＝P(3)2*(1+α(3)3) Predicted pressure P (4) applied to the fourth wafer area of the third wafer at 4.77psi3＝P(4)2*(1+α(4)3) Predicted pressure P (5) applied to fifth wafer area of third wafer at 5.35psi3＝P(5)2*(1+α(5)3)＝4.61psi。
And the like, and obtaining the predicted pressure of each area of the fourth wafer to the predicted pressure of each area of the Nth wafer.
The embodiment provides a method for optimizing polishing pressure on line, which obtains a pressure compensation coefficient, wherein the pressure compensation coefficient can comprehensively consider the influence of a current wafer and a previous wafer on a next wafer, and can effectively adjust the difference between the surface morphology and a reference polishing curve caused by trend change, so that the accuracy of a predicted value of the pressure on the next wafer is improved. The method can adjust the polishing pressure on line and is simplified.
It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications therefrom are within the scope of the invention.

Claims (10)

1. A method of optimizing polishing pressure on-line, comprising:
providing a polishing head, wherein the polishing head is suitable for polishing the wafer;
partitioning the polishing head, wherein the polishing head comprises a first pressure application area to an Nth pressure application area which are distributed from inside to outside in the radial direction, N is an integer larger than or equal to 2, the wafer comprises a first wafer area to an Nth wafer area, the kth wafer area corresponds to the kth pressure application area, and k is an integer larger than or equal to 1 and smaller than or equal to N;
acquiring a reference polishing curve, wherein the reference polishing curve is a curve of the change of the reference polishing removal rate along with the polishing position;
obtaining a first reference normalization coefficient B according to the reference polishing curve1Normalization coefficient B to Nth referenceNK < th > reference normalization coefficient BkThe ratio of the average value of the reference polishing removal rate corresponding to the kth pressure application area to the average value of the reference polishing removal rate corresponding to each area of the polishing head is obtained;
polishing the w wafer by using a polishing head;
obtaining the kth characterization normalization coefficient beta (k) of the removal rate of the kth wafer area of the w waferw；
Providing a prediction model, wherein the prediction model is suitable for exerting pressure P (k) on a k wafer area of a w wafer according to a k pressure exerting areawAnd the pressure compensation coefficient alpha (k) of the kth wafer area of the w +1 th waferw+1Acquiring the predicted pressure P (k) exerted by the kth pressure exerting area on the kth wafer area of the w +1 waferw+1；
α(k)w+1＝λ(k)w*(β(k)w-Bk)+(1-λ(k)w)α(k)w；P(k)w+1＝P(k)w·(1+α(k)w+1)；
Wherein, λ (k)wThe influence weight coefficient of the kth wafer area of the w wafer on the kth wafer area of the w +1 wafer is 0 < lambda (k)w＜1；α(k)wAnd the pressure compensation coefficient of the w wafer is obtained.
2. The method of claim 1, wherein a kth characterization normalization coefficient β (k) of a removal rate of a kth wafer area of a w wafer is obtainedwComprises the following steps: respectively selecting a plurality of measuring points from a first wafer area to an Nth wafer area of a w wafer, and respectively obtaining a normalization coefficient of the removal rate of each measuring point of the w wafer; obtaining a kth characterization normalization coefficient beta (k) of the removal rate of the kth wafer area of the w wafer according to the normalization coefficient of the removal rate of each measurement point in the kth wafer area of the w waferw。
3. The method of claim 2, wherein the k-th characterization normalization coefficient β (k) of the removal rate of the kth wafer area of the w-th wafer is the mean of the normalization coefficients of the removal rate of each measurement point in the kth wafer area of the w-th waferw(ii) a Or taking the maximum value of the absolute difference value between the removal rate of the measuring point in the kth wafer area of the w wafer and 1 as the kth characterization normalization coefficient beta (k) of the removal rate of the kth wafer area of the w waferw。
4. The method of claim 1, wherein the first wafer region to the Nth wafer region of the w wafer have the same impact weight coefficients.
5. The method of claim 1, wherein the first wafer region to the Nth wafer region of the w wafer have at least partially unequal impact weight coefficients.
6. The method of claim 5, wherein the impact weighting coefficients corresponding to the first wafer region to the Nth wafer region of the w wafer are increased progressively.
7. The method of claim 5, wherein N is an integer greater than or equal to 4, the wafer comprises a central region and an edge region, the central region comprises a first wafer region to an Lth wafer region, the edge region comprises an L +1 th wafer region to an Nth wafer region, L is an integer greater than or equal to 2 and less than or equal to N-1; the change rate of the influence weight coefficient from the first wafer area to the L wafer area of the w wafer is smaller than the change rate of the influence weight coefficient from the L +1 wafer area to the N wafer area of the w wafer.
8. The method of claim 7, wherein the total area of the first to Lth wafer regions occupies 68-72% of the total area of the wafer.
9. The method of optimizing polishing pressure on line according to any one of claims 1 to 8, wherein λ (k)wThe value range of (A) is 0.5-0.8.
10. The method of on-line optimizing polishing pressure as recited in claim 9, wherein λ (k)wThe value range of (A) is 0.6-0.7.
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JP2000269195A (en) * 1999-03-19 2000-09-29 Toshiba Corp Manufacturing apparatus for semiconductor substrate
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