KR101259315B1 - Method for polishing semiconductor wafer, and device for polishing semiconductor wafer - Google Patents

Abstract

<Task>
Provided are a method of polishing a semiconductor wafer and a polishing apparatus for a semiconductor wafer, which can accurately estimate the polishing progress when polishing both surfaces of a semiconductor wafer held in a carrier by an up and down rotating surface plate without increasing the work load.
[Solution]
Both surfaces of the wafer W are simultaneously polished by sandwiching the wafer W held by the carrier 6a by the upper and lower rotary plates 2 and 3 and rotating the upper and lower rotary plates 2 and 3. A wafer polishing method using the polishing apparatus 1, which monitors the surface load current value of the polishing apparatus 1 when simultaneously polishing both surfaces of the wafer W, and monitors the monitored surface load current value. Using this, the standard deviation of the surface load current value within a certain time is calculated for each reference time, and the progress of polishing of the wafer W is estimated from the calculated change of the standard deviation.

Description

TECHNICAL FOR POLISHING SEMICONDUCTOR WAFER, AND DEVICE FOR POLISHING SEMICONDUCTOR WAFER}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of polishing a semiconductor wafer and a polishing apparatus of a semiconductor wafer. For example, a method of polishing a semiconductor wafer and a semiconductor that simultaneously polish both surfaces of a semiconductor wafer by using a carrier between upper and lower plates. An apparatus for polishing a wafer.

In recent years, as the integration of semiconductor devices has progressed, the flatness required for semiconductor wafers (hereinafter, also referred to as "wafers") as their raw materials has become strict. In addition, from the viewpoint of manufacturing cost reduction, as the diameter of the wafer is increased, the flatness is more difficult to improve. Moreover, in the process of processing a wafer, the process which introduce | transduced the grinding process after etching is proposed, and the double-side polishing method which has the processing precision superior to the conventional one-side polishing in the mirror surface polishing process after grinding is attracting attention.

And patent document 1 discloses the polishing apparatus of the planetary gear system which performs both-side polishing of a wafer. Here, the structure of the planetary gear type polishing apparatus of the prior art described in patent document 1 is demonstrated, referring FIG.

As shown in FIG. 11, the grinding | polishing apparatus 100 is a disk-shaped lower surface plate 101 supported horizontally, the disk-shaped upper surface 102 which opposes the lower surface plate 101, and a disk shape. A sun gear 103 disposed inside the lower surface plate 101 is provided. In addition, the lower surface plate 101 is rotationally driven by a motor. In addition, the upper surface plate 102 is suspended from the cylinder via a joint, and is driven to rotate in the reverse direction by a motor different from the motor that drives the lower surface plate 101.

In addition, the upper surface plate 102 is provided with a polishing liquid supplying system including a tank for supplying the polishing liquid between the lower surface plate 101. On the opposing surfaces of the lower surface plate 101 and the upper surface plate 102, a polishing cloth made of a urethane resin impregnated with a urethane resin, a foamed urethane, or the like is attached. Moreover, the carrier 104 is set on the lower surface plate 101 so that the sun gear 103 may be enclosed, and the ring-shaped internal gear (not shown) is arrange | positioned on the outer side of this set carrier 104. This internal gear is independently driven to rotate by a motor different from the motor which drives the surface plate (the lower surface plate 101 and the upper surface plate 102).

Then, the polishing operation of the wafer proceeds with the following procedure. First, the upper surface plate 102 is raised to be spaced apart from the lower surface plate 101, and in this state, the plurality of carriers 104 are set on the lower surface plate 101 so as to surround the sun gear 103. Moreover, each set carrier 104 is meshed with the inner sun gear 103 and the internal gear not shown, respectively.

Next, when a predetermined number of carriers 104 are set on the lower surface plate 101, and the wafers 105 are set up in each carrier 104, the upper surface plate 102 is lowered to each wafer 105. A predetermined pressing force is added. Next, the lower surface plate 101, the upper surface plate 102, and the internal gear (not shown) are predetermined while supplying a polishing liquid between the lower surface plate 101 and the upper surface plate 102 in the state where the pressing force is applied. And rotate at a predetermined speed. By the above-described rotation operation, a so-called planetary motion is performed in which the plurality of carriers 104 revolve around the sun gear 103 while rotating the plurality of carriers 104 between the lower surface plate 101 and the upper surface plate 102. The wafers 105 held by the carriers 104 are in sliding contact with the upper and lower polishing cloths in the polishing liquid, so that both the upper and lower surfaces are polished simultaneously.

However, in the above-mentioned double-side polishing process of the wafer, not only the improvement of the flatness of the wafer but also the removal of the processing deformation and the correction of the surface roughness occurring up to the previous process of the double-side polishing process are important. It is a management item. In addition, the polishing amount management in the double-side polishing process of a wafer was generally performed by management of the polishing time based on experience.

Specifically, in the management of the polishing time based on the above-described experience, the experienced side was polished for a predetermined time, after which the finished thickness of the wafer was measured, and the polishing time was adjusted according to the measurement result (if necessary. Polishing). Moreover, in the management of grinding | polishing time based on said experience, the fixed grinding | polishing time is prescribed | regulated, and the method of grind | polishing only for the predetermined | prescribed grinding | polishing time only (polishing time fixing system) is also employ | adopted a lot. Moreover, it is also proposed by patent document 1 to estimate a grinding | polishing end time from the change of the surface vibration frequency in the wafer double-side polishing process, regardless of management of the grinding | polishing time based on the experience as mentioned above.

Japanese Patent Application Publication No. 2005-252000

However, the management of the polishing time based on the above-described experience is not only cumbersome but also cumbersome because the polishing time is adjusted by the measurement result (need to be further polished if necessary). There is a technical problem in that it is impossible to process the wafer while the determination is made. In addition, in the above-described polishing time fixing method, a phenomenon in which the polishing rate after the work is lowered after a work such as a water jet for dressing the polishing cloth or removing foreign matter between the blades occurs. Therefore, there is a technical problem that cannot be produced in the target thickness dimension. Specifically, during processing, such as dressing of the polishing cloth with a diamond dresser, water jet for removing foreign matter between the blades, and the like, the surface temperature of the polishing cloth is lowered and the polishing rate is lowered. . As a result, the finished thickness of the wafer was thicker than the target value. In addition, in the method of estimating the polishing end point from the change of the surface vibration frequency of Patent Document 1, it is difficult to select the optimal surface vibration frequency and the initial setting work of the apparatus is cumbersome. In addition, when the machining conditions were changed, the surface vibration frequency changed, and it was necessary to change the setting every time.

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above technical problem, and a polishing method of a semiconductor wafer capable of accurately estimating the progress of polishing when polishing both surfaces of a semiconductor wafer by an up and down rotating surface plate without increasing the work load, and It is an object to provide a polishing apparatus for a semiconductor wafer.

The present invention for solving the above problems is a semiconductor using a polishing apparatus for simultaneously polishing both surfaces of the semiconductor wafer by sandwiching the semiconductor wafer held in the carrier by the upper and lower rotating platen and rotating the upper and lower rotating platen. A method of polishing a wafer, the method comprising: monitoring a surface load current value of the polishing apparatus when simultaneously polishing both surfaces of the semiconductor wafer; Calculating the standard deviation of the surface load current value within a predetermined time for each reference time using the monitored surface load current value, and estimating the progress of polishing from the calculated change in the standard deviation; And a control unit.

Adopting the above-described configuration, the inventors of the present application, as a result of examining in detail the changes over time of the polishing apparatus with the progress of the double-side polishing of the semiconductor wafer in detail, the device changes due to the frictional resistance due to the polishing of the wafer or carrier This is because it was found that the surface load current value, which is a value, changes (deviation becomes small) reflecting the progress of polishing. In other words, it was found that the progress of polishing of the semiconductor wafer can be accurately estimated by examining the standard deviation of the plate load current values. Therefore, according to the present invention, the semiconductor wafer is completed without any work burden (because no adjustment work for polishing time based on the measurement result is required) compared to the method according to the conventional "management of polishing time based on experience". The thickness can be approximated to the "target thickness".

Further, when the standard deviation reaches a predetermined value, it is preferable to estimate the end point of polishing. In addition, when the time-varying pattern of the standard deviation satisfies a predetermined relationship, it is preferable to estimate the end point of polishing. This is because, as described above, the surface load current value changes to reflect the progress of polishing (the deviation is small). That is, the end point of grinding | polishing can be estimated correctly by the value of the standard deviation of a plate load current value, or a change pattern.

Moreover, this invention for solving the said subject is a semiconductor wafer which grind | polishes both surfaces of the said semiconductor wafer simultaneously by clamping the semiconductor wafer hold | maintained by the carrier by the up-and-down rotation plate, and rotating the said up-and-down rotation plate. A polishing unit comprising: a detecting unit for monitoring a plate load current value when simultaneously polishing both surfaces of the semiconductor wafer; Polishing progress estimating section which calculates the standard deviation of the surface load current value within a predetermined time for each reference time using the monitored plate load current value, and estimates the progress of polishing from the change of the calculated standard deviation. Wow; Characterized in having a. As described above, according to the polishing apparatus of the semiconductor wafer of the present invention, the surface load current value that changes (deviation becomes small) reflecting the progress of polishing is monitored, and the polishing surface is changed by the standard deviation of the monitored surface load current value. Since the progress is estimated, the progress of polishing of the semiconductor wafer can be estimated accurately.

In addition, the carrier is preferably formed of a material having a smaller coefficient of friction than the semiconductor wafer. The carrier is preferably formed by coating the surface of the substrate with a material having a smaller coefficient of friction than the semiconductor wafer. The carrier preferably has a thickness dimension equal to the completion target thickness of the semiconductor wafer or a thickness dimension within a range of ± 6 μm from the center value of the target thickness. By the above configuration, the progress of the polishing process of the semiconductor wafer can be estimated with high accuracy.

In the polishing method of the semiconductor wafer which concerns on the said subject, the semiconductor wafer hold | maintained in the carrier by the up-and-down rotational platen is clamped, and the said upper and lower rotational platen is rotated simultaneously, and both surfaces of the said semiconductor wafer are simultaneously operated. A method of polishing a semiconductor wafer using a polishing apparatus for polishing, comprising the steps of: monitoring a surface load current value of the polishing apparatus when both surfaces of the semiconductor wafer are simultaneously polished; Using the monitored platen load current value, the standard deviation of the platen load current value within a predetermined time is calculated for each reference time period, and the polishing is terminated when the hourly variation pattern of the standard deviation satisfies a predetermined relationship. Estimating with a viewpoint; Characterized in that it comprises a.

Adopting the above-described configuration, the inventors of the present application in detail investigated the change over time of the polishing apparatus according to the progress of the double-side polishing of the semiconductor wafer in detail, the device detection changes due to the frictional resistance caused by the polishing of the wafer or carrier This is because it was found that the surface load current value, which is a value, changes (deviation becomes small) reflecting the progress of polishing. In other words, it was found that the progress of polishing of the semiconductor wafer can be accurately estimated by examining the standard deviation of the plate load current values. Therefore, according to the present invention, compared to the method according to the "management of polishing time based on the experience" of the prior art, the completion thickness of the semiconductor wafer can be reduced without any work (because the adjustment work of polishing time based on the measurement result is not necessary). It is possible to approach the "target thickness".

In particular, the present invention is characterized by estimating the end point of polishing when the hourly variation pattern of the standard deviation satisfies a predetermined relationship. As described above, since the surface load current value changes to reflect the progress of polishing (the deviation becomes smaller), the end point of polishing can be accurately estimated by the standard deviation value or the change pattern of the surface load current value. have.

Here, the step of estimating the end point of polishing calculates the standard deviation of the surface load current value within a predetermined time period for each reference time, and Y = mX + b with respect to the standard deviation calculated in the predetermined time period. From the linear approximation represented by the formula (where X: elapsed time, Y: standard deviation (σ), m: slope, b: intercept), the slope (m) is calculated and the change pattern of the slope (m) It is preferable to estimate the end point of the polishing when the inclination m satisfies the condition of " above a predetermined threshold value ".

In addition, the step of estimating the end point of polishing calculates the standard deviation of the surface load current value within a predetermined time for each reference time, and calculates the difference between the recent standard deviation calculated and the standard deviation calculated before the predetermined time. It is preferable to calculate and calculate the change pattern of the difference, and to estimate it as the end point of polishing when the difference satisfies the condition of "above a predetermined threshold value".

In addition, in the semiconductor wafer polishing apparatus according to the present invention for solving the above problems, the semiconductor wafer held by the carrier is held by an upper and lower rotating platen to rotate the upper and lower rotating platen to rotate both surfaces of the semiconductor wafer. A polishing apparatus for a semiconductor wafer for simultaneously polishing the polishing apparatus, the apparatus comprising: a driving control section for controlling a rotation operation of the upper and lower rotary tables; A detection unit for monitoring a surface load current value when both surfaces of the semiconductor wafer are polished simultaneously; Polishing progress estimating section which calculates the standard deviation of the surface load current value within a predetermined time for each reference time using the monitored plate load current value, and estimates the progress of polishing from the change of the calculated standard deviation. Wow; And the polishing progress estimating unit transmits a polishing end signal to the drive control unit when the hourly change pattern of the standard deviation calculated for each reference time satisfies a predetermined relationship, thereby rotating the rotating platen. It stops and stops grinding, It is characterized by the above-mentioned. According to such a polishing apparatus for a semiconductor wafer of the present invention, the surface load current value that changes (deviation becomes small) reflecting the progress of polishing is monitored, and the polishing progresses based on the standard deviation of the monitored surface load current value. Since the degree can be estimated, the progress of polishing of the semiconductor wafer can be accurately estimated, and the completed thickness of the semiconductor wafer is referred to as the target thickness without incurring a work burden (no need to adjust the polishing time based on the measurement result). "To close.

Here, the polishing progress estimating unit calculates the standard deviation of the surface load current value within a predetermined time period for each reference time period, and, with respect to the standard deviation calculated in the predetermined period, a formula of Y = mX + b ( However, from the linear approximation represented by X: elapsed time, Y: standard deviation (σ), m: slope, and b: intercept, the slope m is calculated to obtain a change pattern of the slope m, When the inclination m satisfies the condition of "more than a predetermined threshold", it is preferable to estimate it as the end time of grinding | polishing.

The polishing progress estimating unit calculates the standard deviation of the surface load current value within a predetermined time for each reference time, and calculates the difference between the latest standard deviation calculated and the standard deviation calculated before the predetermined time. It is preferable to obtain a pattern of change of the difference and to estimate the end point of polishing when the difference satisfies the condition of "at least a predetermined threshold value".

According to the present invention, it is possible to provide a semiconductor wafer polishing method and a semiconductor wafer polishing apparatus capable of accurately estimating the polishing progress situation when polishing both surfaces of a semiconductor wafer by the up and down rotating surface plate without increasing the work load. Can be.

BRIEF DESCRIPTION OF THE DRAWINGS The block diagram which shows typically the structure of the grinding | polishing apparatus which concerns on embodiment of this invention.
Fig. 2 is a graph showing an upper plate load current value corresponding to polishing time when a polishing apparatus for simultaneously polishing both surfaces of a semiconductor wafer is polishing a wafer;
Fig. 3 is a graph showing a value calculated for each reference time of the standard deviation within a predetermined time of the upper surface load current value when the polishing apparatus for simultaneously polishing both sides of the wafer is polishing the wafer, corresponding to the polishing time of the wafer. .
4 shows a standard deviation within a predetermined time period for a predetermined period of time for a predetermined time period of the upper surface load current value when the polishing apparatus for simultaneously polishing both sides of the wafer is polishing the wafer, and the standard deviation calculated within the predetermined period. For the reference time, the slope m is calculated for each reference time from a linear approximation expressed by the formula Y = mX + b (where X: elapsed time, Y: standard deviation (σ), m: slope, and b: intercept). And a graph showing the change pattern of the slope m in correspondence with the polishing time of the wafer.
Fig. 5 shows the standard deviation within a predetermined time of the upper surface load current value when the polishing apparatus for simultaneously polishing both sides of the wafer is polishing the wafer for each reference time, and the latest standard deviation calculated and before the predetermined time. A graph showing a difference pattern calculated by calculating the difference between the calculated standard deviations, and corresponding the polishing time of the wafer.
Fig. 6 is a schematic diagram showing the correlation between the completed thickness of the wafer and the standard deviation of the upper surface load current value, which is a threshold value for specifying the completed thickness.
Fig. 7 is a schematic diagram showing the correlation between the finished thickness of the wafer and the standard deviation of the upper surface load current value immediately before the end of polishing specifying the finished thickness.
8 is a flowchart illustrating a processing procedure for estimating the progress of a wafer polishing process performed by the polishing apparatus according to the first embodiment of the present invention.
Fig. 9 is a flowchart showing a processing procedure for estimating the progress of the wafer polishing process performed by the polishing apparatus according to the second embodiment of the present invention from the inclination of the standard deviation of the upper surface load current value.
10 is a flowchart showing a processing procedure for estimating the progress of the wafer polishing process performed by the polishing apparatus according to the second embodiment of the present invention from the difference of the standard deviation of the upper surface load current value.
It is a schematic diagram which shows the structure of the planetary gear type polishing apparatus of a prior art.

EMBODIMENT OF THE INVENTION Hereinafter, the grinding | polishing method of the semiconductor wafer which concerns on embodiment of this invention, and the grinding | polishing apparatus (henceforth a "polishing apparatus") of a semiconductor wafer are demonstrated with reference to drawings. First, the structure of the grinding | polishing apparatus which concerns on embodiment of this invention is demonstrated with reference to FIG. Here, FIG. 1 is a block diagram which shows typically the structure of the grinding | polishing apparatus which concerns on embodiment of this invention.

As shown in the drawing, the polishing apparatus 1 is an apparatus for simultaneously mirror-polishing both surfaces of a semiconductor wafer W (hereinafter referred to as "wafer W") which is a substrate to be processed, and a plurality of semiconductor wafers W It is a device structure for batch processing. Moreover, the grinding | polishing apparatus 1 is equipped with the surface load current detection part 12 and the control part 20, The apparatus at the time of the grinding | polishing of the wafer W by the said surface load current detection part 12 and the control part 20. The detection value (value indicating the state of the polishing device 1) is monitored, and the standard deviation (σ) of the detected device detection value within a predetermined time (for example, 60 seconds) from the monitored device detection value is referred to as the reference time. It calculates every time (for example, every 1 second), and estimates the progress of the wafer W grinding | polishing process from the calculated standard deviation (sigma). In addition, among the structures of the polishing apparatus 1 according to the embodiment of the present invention, the same technique as that in the known art is used except for the structure (the plate load current detection unit 12 and the control unit 20) for estimating the progress of the wafer W polishing process. Do. Therefore, below, the structure of the polishing apparatus 1 other than "the surface load current detection part 12 and the control part 20" is simplified and demonstrated.

Specifically, the polishing apparatus 1 includes an upper surface plate (upper rotation plate) 2 and a lower surface plate (lower rotation plate) 3, and on both surfaces thereof, to polish both surfaces of the wafer W. Polishing cloths 4 and 5 are attached, respectively. In addition, a plurality of carriers 6a holding the plurality of wafers W are disposed between the upper surface plate 2 and the lower surface plate 3, respectively. In addition, the upper and lower surfaces of the wafers W held by the carriers 6a are in a state facing the polishing cloths 4 and 5.

In addition, the upper surface plate 2 is provided by the elevating drive unit 7 so as to move up and down, and at the time of polishing, the elevating drive unit 7 moves the upper surface plate 2 downward to move each carrier 6a. Is fitted to the upper and lower surface plates and is pressed at a predetermined pressure. On the other hand, at the time of carrying in / out of the wafer W, maintenance, etc., the upper surface plate 2 is moved up and down with respect to the lower surface plate 3 by the elevating drive unit 7. In addition, the drive of the lift driver 7 is controlled based on the command signal from the controller 20.

Moreover, the upper shaft 2 is provided with the rotating shaft 2a which rotates about an axis by the upper rotation drive part 8a. And the upper surface plate 2 is made to rotate with the rotating shaft 2a driven (rotated) by the upper rotation drive part 8a. In addition, the lower surface plate 3 is provided with a rotating shaft 3a that is rotated about the axis by the lower rotation driving unit 8b. And the lower surface plate 3 is made to rotate (rotate in the opposite direction to the upper surface plate 2) with the rotating shaft 3a driven (rotated) by the lower rotation drive part 8b. Moreover, the operation | movement of the upper rotation drive part 8a and the lower rotation drive part 8b is controlled based on the command signal from the control part 20. As shown in FIG.

Moreover, the some carrier 6a is arrange | positioned on the same circumference centering on the rotating shaft (not shown) arrange | positioned coaxially with the said rotating shaft 2a and the rotating shaft 3a, and each side part is the said rotating shaft ( It is made to engage with the sun gear (not shown) provided around the not shown. In addition, an annular internal gear 6c is provided outside the plurality of carriers 6a around the rotating shaft (not shown) so as to surround the entirety thereof, and on the side of each carrier 6a. It is supposed to be engaged. The internal gear 6c is independently driven by a motor different from a mechanism (upper rotation driver 8a, lower rotation driver 8b) that drives the surface plate (upper surface plate 2, lower surface plate 3). It is supposed to be.

In addition, the upper surface plate 2 is provided with a polishing liquid supply pipe 10 for supplying a polishing liquid to the polishing surface of the carrier 6a, and the polishing liquid supply pipe 10 includes a polishing liquid storage tank, a pump, or the like. The polishing liquid is supplied by the polishing liquid supply unit 11. In addition, the operation | movement of the polishing liquid supply part 11 is controlled based on the command signal from the control part 20. FIG.

Moreover, the polishing apparatus 1 is provided with the surface load current detection part 12 connected (electrically connected) to the upper rotation drive part 8a which drives the upper surface plate 2 to rotate. The platen load current detection unit 12 monitors (detects) an "upper platen load current value" while the upper rotary drive unit 8a is rotating the upper platen 2, and acquires the platen load current of the control unit 20. The unit 22 is configured to transmit the monitored "upper plate load current value".

In addition, the polishing apparatus 1 includes a control unit 20 that controls the operation of the entire apparatus and estimates the progress of the wafer W polishing process. The control unit 20 includes a drive control unit 21 for controlling the operation of the entire apparatus, a plate load current acquisition unit 22 for receiving an "upper plate load current value" transmitted by the plate load current detection unit 12, and And a polishing progress state estimating section 23 for estimating the polishing progress state (progression) of the wafer W by using the "upper plate load current value" received by the surface load current acquiring unit 22.

In addition, although the hardware structure of the control part 20 is not specifically limited, For example, the control part 20 can be comprised by the computer provided with a CPU and a memory. In this case, the memory stores a program for realizing the functions of the "drive control unit 21, the surface load current acquisition unit 22, and the polishing progress status estimation unit 23." The functions of the "drive control unit 21, the surface load current acquisition unit 22, and the polishing progress status estimation unit 23" are realized by the CPU executing the program stored in the memory. Hereinafter, the function of each part of the control part 20 is demonstrated in detail.

Specifically, the drive control unit 21 is used for various parts of the polishing apparatus 1 (lift drive unit 7, upper rotation drive unit 8a, lower rotation drive unit 8b, polishing liquid supply unit 11, and the like). A command signal (control signal) is transmitted to control the operation of each part. In addition, the surface load current acquisition unit 22 receives the "upper surface load current value" transmitted from the surface load current detection unit 12 and stores it in a predetermined area of the memory of the control unit 20.

The polishing progress estimating unit 23 employs the upper surface load current value stored in the memory, and the standard deviation σ of the upper surface load current value monitored within a predetermined time (for example, 60 seconds). Is calculated every reference time (for example, every second), and the progress of the wafer W polishing process is estimated from the calculated standard deviation σ. When the thickness of the semiconductor wafer being polished is estimated to be the "target thickness", a polishing end signal is sent to the drive control unit 21 to stop the rotation operation of the rotating surface plate and terminate the polishing. Consists of. In addition, in order to be able to estimate the progress of the wafer W polishing process with high accuracy, the thickness (thickness dimension) of the carrier 6a of the polishing apparatus 1 is the target thickness of the wafer W (wafer ( A thickness dimension (preferably, a thickness dimension within a range of ± 6 μm from the center value of the completion thickness dimension of the wafer W) in the same dimension as the completed thickness dimension of W).

In addition, in order to be able to estimate the progress of the wafer W polishing process with high precision, the carrier 6a is formed of a material whose friction coefficient of the surface is smaller than the friction coefficient of the surface of the wafer W. desirable. For example, the carrier 6a may be formed by coating a DLC (Diamond Like Carbon) film having a low coefficient of friction on the surface of the base material based on stainless steel, titanium, resin, or the like. Thus, the structure which estimates the progress of the wafer W grinding | polishing process using the monitored upper surface load current value is employ | adopted for the following reason.

Specifically, the inventors of the present application have investigated in detail the changes over time of the polishing apparatus 1 according to the progress of polishing of the wafer W, which is attributable to the frictional resistance caused by the polishing of the wafer W and the carrier 6a. Device detection value (e.g., upper surface load current value) that is changed to reflect the progress of polishing Based on finding change. In addition, the inventor of the present application, if the thickness of the carrier 6a of the polishing apparatus 1 is equal to or slightly thinner (or slightly thicker) than the target thickness of the wafer W, and the wafer W is polished, It is based on finding out that the deviation of the apparatus detection value (upper surface load current value etc.) of the polishing apparatus 1 becomes small by the decrease of the thickness dimension of the wafer W with progress.

Specifically, the inventor of the present application performed a single-sided polishing process once in a general double-side polishing apparatus to monitor the upper surface load current value at the time of polishing the wafer W every second. As a result of creating two-dimensional coordinates in which "polishing elapsed time" is taken on the X-axis, and "upper plate load current value" is taken on the Y-axis, and plotting the monitored value on the two-dimensional coordinates, The result shown in FIG. 2 was obtained. Referring to FIG. 2, it can be seen that the deviation of the upper platen load current decreases with passage of the polishing time.

Using the monitored upper surface load current value, the standard deviation (σ) of the upper surface load current value for 60 seconds is calculated every second, and the "elapsed time of polishing" is taken on the X axis, and the Y axis is applied to the Y axis. The two-dimensional coordinate which took "standard deviation (sigma) of the upper platen load current value for 60 second" was created, and the calculated value was plotted on the two-dimensional coordinate, and the result shown in FIG. 3 was obtained. Referring to FIG. 3, it can be seen that the standard deviation σ of the upper surface load current value decreases with the progress of the polishing time to become the minimum value (the point at which the X-axis in the drawing is 1330 seconds) and then returns to the rise.

This is caused by the fact that the subject to be polished changes with the progress of polishing (the polishing object shifts from "wafer W" to "wafer W and carrier 6a" to "carrier 6a"). I think. That is, as described above, when the thickness of the wafer W is thicker than the carrier 6a, the addition of polishing by the polishing cloths 4 and 5 is applied to the wafer W, and then the wafer ( If the thickness of W) and the thickness of the carrier 6a are the same, the addition is dispersed in both the wafer W and the carrier 6a, and further, the thickness of the wafer W is then the thickness of the carrier 6a. When it becomes thinner, it is thought that the said addition arises by moving to the carrier 6a. Therefore, the minimum value of the standard deviation? Shown in FIG. 3 is considered to be the point in time at which the thickness dimension of the wafer W and the thickness dimension of the carrier 6a are the same.

Therefore, using the phenomenon shown in FIG. 3, the standard deviation (σ) (the standard deviation (σ) of the plate load current value within a predetermined time period) of the upper plate load current value monitored within the predetermined elapsed time for each reference time. The calculation was made (every a second), and the time point at which the standard deviation σ reached a predetermined threshold value (minimum value) was estimated as the end point of polishing. The change pattern refers to an index of change of the slope of the standard deviation within a predetermined time or the difference between the latest standard deviation calculated and the standard deviation calculated before the predetermined time.

For example, with respect to the result of the standard deviation of the upper surface load current value for 60 seconds calculated every second shown in FIG. 3, the slope of the standard deviation for 150 seconds is calculated every second, and the "axis of polishing" is plotted on the X axis. Time ", a two-dimensional coordinate having" 150 degrees of inclination of the standard deviation of the upper surface load current value for 60 seconds "on the Y-axis was created, and the calculated value was plotted on the two-dimensional coordinates. The result shown in FIG. 4 was obtained. Further, with respect to the result of the standard deviation of the upper plate load current value for 60 seconds calculated for each second shown in FIG. 3, the difference from the standard deviation of 150 seconds before is calculated every second, and the "Elapsed time of polishing" is plotted on the X axis. ", And the two-dimensional coordinates which took" the difference from 150 second of the upper surface load current standard deviation for 60 second "on the Y-axis were created, and the said calculated value was plotted on the two-dimensional coordinates, FIG. The result shown to was obtained.

4 and 5, it can be seen that the slope or the difference in both figures is rapidly changing around 1400 seconds. That is, the polishing end point can be estimated by setting the threshold value for the value indicating the change in the standard deviation.

Moreover, the inventor of this application verified the relationship between the value of the standard deviation ((sigma)) used as a threshold, and the thickness of the completed wafer (W). Specifically, the standard deviation σ of the upper surface load current value for 60 seconds at the time of polishing the wafer W is calculated every second, and the polishing point is the end of polishing at which the standard deviation σ becomes the threshold value set. The correlation between " thickness of the finished wafer W " and " threshold value (standard deviation? Of upper plate load current value for 60 seconds at the time of wafer W polishing) was verified by the least square method. Specifically, the correlation between the standard deviation and the center thickness of the wafer (1 sheet per batch) processed at that time is irradiated for 20 batches, and the approximate equation is the least square method for the plotted result. According to the above verification, the result shown in Fig. 6 (approximate expression (y = 0.1393x-107.67), crystal coefficient (R2 = 0.9336)) was obtained.

And from the result shown in FIG. 6, it turns out that the thickness of a completed wafer W and a threshold value have a big correlation, and adjusts the said threshold value to the target value aimed at the thickness of the completed wafer W. We found out that we could get close. Moreover, in embodiment of this invention, although the time point which the said standard deviation (sigma) reached predetermined value (threshold value) is estimated as grinding | polishing end time, it is not specifically limited to this. For example, when the above-described change pattern of time of the standard deviation σ satisfies a predetermined relationship (for example, when the slope of a certain section of the upper surface load current standard deviation becomes zero, etc.), You may presume polishing completion. In addition, when it is desired to make the target thickness of the wafer W thinner than the thickness of the carrier 6a, polishing is performed for a predetermined time when the standard deviation σ reaches a predetermined value (minimum value). It can also be the end point. Moreover, the inventor of this application verified the relationship between the value of the standard deviation ((sigma)) just before completion | finish of processing, and the thickness of the completed wafer (W). Specifically, the standard deviation σ of the upper surface load current value for 60 seconds at the time of polishing the wafer W is calculated every second, and the processing time is divided into eleven conditions, so that the wafer thicknesses before polishing are almost equal ( W) was polished to verify the relationship between the "thickness of the finished wafer W" and the "standard deviation (?) Of the upper plate load current value for 60 seconds immediately before the polishing W was finished." The correlation between the standard deviation σ and the finished wafer thickness is shown in FIG. 7.

From the results shown in FIG. 7, it is known that the change in the standard deviation σ reflects the thickness of the finished wafer W, the process is treated as an index of the change pattern, and the time when the predetermined relationship is satisfied is the polishing end point. By estimating, it turned out that the thickness of the completed wafer W can be approached to the target value made into the objective. In addition, when the completion target thickness of the wafer W is to be made thinner than the thickness of the carrier 6a, the polishing end point may be a polishing point for a predetermined time when the index of the change pattern satisfies a predetermined relationship. It may be.

Next, the operation of the polishing apparatus 1 will be described. In the polishing apparatus 1 comprised as mentioned above, when the wafer W before grinding | polishing is provided in each carrier 6a, the upper surface plate 2 will move down by the control of the control part 20. FIG. Then, the wafer W held by the carrier 6a is sandwiched by the upper surface plate 2 and the lower surface plate 3, and is pressed into a predetermined load. Subsequently, the rotation shafts 2a and 3a are driven to rotate, the polishing liquid is supplied from the polishing liquid supply pipe 10, and each carrier 6a rotates while rotating around the rotation shaft (not shown). As a result, both surfaces of the wafer W are simultaneously polished by the polishing cloths 4 and 5.

Moreover, when the grinding | polishing process of the wafer W is started, the control part 20 performs the process steps of FIG. 8, 9, or 10, monitoring the upper surface load current value via the surface load current detection part 12. FIG. Then, the polishing end time of the wafer W is estimated, and the polishing process of the wafer W by the polishing apparatus 1 is completed.

[First Embodiment]

Next, the process of estimating the progress of the wafer W polishing process performed by the polishing apparatus 1 according to the first embodiment of the present invention will be described with reference to FIG. 8. 8 is a flowchart showing a processing procedure for estimating the progress of the wafer polishing process performed by the polishing apparatus according to the present embodiment, and is performed by the polishing progress status estimating unit 23 constituting the control unit 20. The processing shown is shown. In addition, in parallel to the processing step of FIG. 8, the surface load current detection unit 12 and the surface load current acquisition unit 22 monitor the "upper surface load current value", and are stored in a predetermined area of the memory of the control unit 20. Processing is performed.

Specifically, the polishing progress estimating unit 23, when the polishing process of the wafer W is started, until the elapsed time T from the polishing start becomes "A (for example, 60 seconds)". When it waits and the elapsed time T becomes "A second", it will transfer to the process of S2 (S1).

Next, the polishing progress state estimating unit 23 uses the "upper plate load current value" stored in the memory to "A second ago" based on "elapsed time T from the start of polishing". The standard deviation σ of the "upper plate load current value" monitored during (constant time) is calculated (S2).

Next, the polishing progress state estimating unit 23 compares the standard deviation σ calculated in S2 with a predetermined threshold value, so that the standard deviation σ of the "upper plate load current value" is equal to or less than the threshold value ( If the standard deviation σ is a threshold value, the process proceeds to S5, and if the standard deviation σ is greater than the threshold value (standard deviation σ> threshold value), the process proceeds to S4 (S3).

Specifically, in the step S3, the polishing progress estimating unit 23, when the standard deviation sigma is equal to or less than the threshold (that is, the deviation of the "upper plate load current value" is less than or equal to the predetermined level). It is assumed that the wafer W is polished to the completion target thickness, and the processing proceeds to S5. On the other hand, in the step S3, the polishing progress estimating unit 23 performs a wafer if the standard deviation σ is larger than the threshold value (that is, the deviation of the "upper plate load current value" is larger than the predetermined level). It is assumed that (W) has not been polished to the completion target thickness, and the flow advances to S4. In S5, the polishing progress estimating unit 23 estimates the polishing end time, and terminates the polishing process of the wafer W through the drive control unit 21. Specifically, the polishing progress estimating unit 23 supplies the drive control unit 21 with the standard deviation σ being lower than or equal to the threshold (that is, when the deviation of the "upper plate load current value" becomes small to a predetermined level). A signal indicating that the polishing finish point is transmitted. Moreover, when the drive control part 21 receives the signal which shows that it is the completion | finish time of grinding | polishing, each part (lift drive part 7, the upper rotation drive part 8a, the lower rotation drive part 8b, and grinding | polishing) of the grinding | polishing apparatus 1 is polished. Various command signals (control signals) are sent to the liquid supply unit 11 and the like to terminate the polishing process.

On the other hand, in S4, the polishing progress state estimating unit 23 waits until the elapsed time elapses from "T (second)" to "a (for example, 1 second) second", and then "T". After incrementing "a" to (T ← T + a), the process proceeds to the above-described S2, and S2, S3, S4 until S3 becomes "standard deviation (σ) ≤ threshold value". Repeat the process.

In this way, by repeating the processing of "S2, S3, S4", the standard deviation of the "upper plate load current value" monitored in the last A second (constant time A) is referred to as the reference time (a second). It can calculate every time. For example, when A is "60 seconds" and a is "1 second", the polishing progress estimating unit 23 performs the wafer in the first processing of S2 which proceeds immediately after the processing of S1. The standard deviation σ of the "upper plate load current value" monitored for 60 seconds from the polishing start of (W) is calculated. In addition, the polishing progress estimating unit 23 performs the second process S2 that proceeds immediately after the first process S4 until the end of 61 seconds elapses from 1 second after the polishing start of the wafer W. Calculate the standard deviation σ of the "upper plate load current value" monitored during 60 seconds of. In addition, the polishing progress estimating unit 23 performs the second S2 processing immediately after the second S4, until 62 seconds have elapsed after 2 seconds have elapsed from the polishing start of the wafer W. Calculate the standard deviation σ of the "upper plate load current value" monitored during 60 seconds of.

As described above, in the present embodiment, the standard deviation of the "upper plate load current value" monitored within the latest predetermined elapsed time (constant time (A second)) is calculated for each reference time (every a second), and Since the progress of polishing of the wafer W is determined based on the standard deviation, the progress of polishing can be estimated in real time.

As described above, according to the polishing method of the wafer (see FIG. 8) and the polishing apparatus 1 of the present embodiment, the labor of the operator is compared with the method by the "management of polishing time based on the experience" of the prior art. Without increasing, the completed thickness of the wafer W can be brought close to the "target thickness", and deterioration in flatness of the wafer W due to lack of polishing can be suppressed. In addition, this invention is not limited to embodiment mentioned above, A various change is possible within the range of the summary.

For example, in the above-described embodiment, the "upper plate load current value" is monitored in order to estimate the progress of the wafer W polishing process, but is not particularly limited thereto. The "upper plate load current value" is only one example of a signal that changes due to the frictional resistance caused by the polishing of the wafer W and the carrier 6a. Any device detection value that changes due to the frictional resistance can be used to estimate the progress of the wafer W polishing process. Specifically, the "bottom plate load current value", not "top plate load current value" is monitored, and the standard deviation σ of the monitored "bottom plate load current value" is calculated for each reference time, and the calculation is performed. The progress of the wafer W polishing process may be estimated from one standard deviation σ.

In the above-described embodiment, the standard deviation of the "upper plate load current value" monitored within the predetermined elapsed time (constant time (A second)) is calculated for each reference time (a second). The time (constant time (A second)) and the reference time (a second) can be appropriately set according to the size of the wafer W as a target. For example, it is preferable that the predetermined elapsed time (constant time (A second)) is "10 to 300 seconds" and the reference time (a second) is "0.1 second to 10 seconds". If the predetermined elapsed time A is 10 seconds or less, the deviation of the standard deviation is large, and there is a fear that the accuracy is lowered, such as incorrectly detecting the end point. On the other hand, when the predetermined elapsed time A is 300 seconds or more, there is a fear that a delay occurs in end point detection. In addition, since the reference time (a) detects the end point in real time, the smaller one is preferable. However, if the reference time (A) is 0.1 seconds or less, high processing capacity of the controller is required, and the reference time (A) is 10. If it is more than a second, there exists a possibility that delay may arise in endpoint detection.

In addition, although the progress of the grinding | polishing process was estimated by the standard deviation of the monitored apparatus detection value (upper surface load current value etc.) in the above-mentioned embodiment, it is not limited to this in particular. If it is an index (for example, "maximum value-minimum value") which shows the deviation of the monitored apparatus detection value other than standard deviation, it can apply to this invention.

Next, the polishing method (and polishing apparatus) which concerns on this embodiment is further demonstrated based on Example 1. FIG. In the present Example 1, the double-side polishing process of the wafer W was processed according to the said 1st Embodiment, and the effect of this invention was verified.

Example 1 In Example 1, using the polishing apparatus 1 described above, double-side polishing of a silicon wafer W having a diameter of 300 mm was carried out for 20 cycles under the following conditions. In addition, in Example 1, the thickness target value of the completed wafer W was made "776 micrometers." In addition, the carrier 6a used the stainless steel as a base material, and coat | covered the DLC film | membrane on the surface of the base material, and the thing of thickness "775 micrometers" was used.

In addition, as the apparatus detection value for estimating the polishing completion point, the standard deviation is calculated for 60 seconds every 1 second using the "upper plate load current value" as in the first embodiment described above. The time point when the deviation became "0.3 (threshold)" or less was estimated as the end time of polishing. In addition, the grinding | polishing apparatus 1 uses the type which simultaneously polishes five wafers W (one wafer W per carrier 6a) between the upper surface plate 2 and the lower surface plate 3. It was. As the polishing cloths 4 and 5, those made of hard polyurethane were used. In addition, the abrasive | polishing agent used the colloidal silica aqueous solution, and performed supply amount control, supply temperature control, and pH control. In addition, the working pressure was "150g / cm <2>". Moreover, the grinding | polishing time was the average value: 24.9 minutes, the maximum value: 25.8 minutes, the minimum value: 24.0 minutes, and the standard deviation: 0.42 minutes in the result of 20 cycles.

Then, for each of the "center thickness" and "GBIR (Global Backside Ideal-reference-plane Range") of the 100 wafers W polished by the conditions mentioned above, "average value", "standard deviation", "maximum Value "and" minimum value "were measured, and the result shown in following Table 1 was obtained.

Center thickness (㎛)

GBIR (nm)

medium

776.0

186

Standard Deviation

0.21

22

Value

776.4

231

Minimum value

775.7

136

COMPARATIVE EXAMPLE 1 In this comparative example 1, by double-sided polishing which made polishing time constant, double-sided polishing of the silicon wafer W of (phi) 300mm is carried out similarly to Example 1, under the following conditions. Cycle proceeded. Specifically, the thickness target value of the finished wafer W was set to "776 micrometers" similarly to Example 1 mentioned above. In addition, the carrier 6a used the stainless steel as a base material, and coat | covered the DLC film | membrane on the surface of the base material, and used the thing of thickness "775 micrometers."

In the same manner as in the first embodiment, the polishing apparatus simultaneously drives five wafers W (one wafer W for one carrier 6a) between the upper surface plate 2 and the lower surface plate 3. Polishing type was used. In addition, the polishing cloths 4 and 5 were made of hard polyurethane in the same manner as in Example 1 above. In addition, the abrasive | polishing agent carried out supply quantity management, supply temperature management, and pH management similarly to Example 1 using the colloidal silica aqueous solution. In addition, the working pressure was "150g / cm <2>". In addition, grinding | polishing time was made into "25 minutes."

Then, for each of the "center thickness" and "GBIR (Global Backside Ideal-reference-plane Range") of 100 wafers W polished by the conditions mentioned above, "average value", "standard deviation", "maximum Value "and" minimum value "were measured, and the result of Table 2 shown below was obtained.

Center thickness (㎛)

GBIR (nm)

medium

776.1

208

Standard Deviation
0.27

44

Value
776.8

341

Minimum value
775.7

138

From the said Example 1 and the comparative example 1, it was confirmed that according to the grinding | polishing method which concerns on this invention, the dispersion | variation in the thickness and flatness of a finished wafer can be reduced compared with the method of making double-side grinding | polishing by making polishing time constant.

[Second Embodiment]

Next, the process of estimating the progress of the wafer W polishing process performed by the polishing apparatus 1 according to the second embodiment of the present invention will be described with reference to FIG. 9. 9 is a flowchart showing a processing procedure for estimating the progress of the wafer polishing process performed by the polishing apparatus according to the present embodiment, and is performed by the polishing progress status estimating unit 23 constituting the control unit 20. The processing shown is shown. In addition, similarly to the first embodiment, in parallel to the processing step of FIG. 9, the platen load current detection unit 12 and the platen load current acquisition unit 22 monitor the "upper platen load current value" to control the controller 20. Is stored in a predetermined area of the memory.

Specifically, when the polishing progress estimation unit 23 starts the polishing process of the wafer W, when the elapsed time T from the polishing start becomes "A second (for example, 60 seconds)". When it waits until the elapsed time T becomes "A second", it transfers to the process of S12 (S11).

Next, the polishing progress state estimating unit 23 uses the "upper plate load current value" stored in the memory to "A second ago" based on "elapsed time T from the start of polishing". The standard deviation standard deviation (σ) of the "upper plate load current value" monitored during (constant time) is calculated (S12). In parallel to the processing step of FIG. 9, the standard deviation? Calculated in S12 is stored in a predetermined area of the memory of the control unit 20.

Next, the polishing progress estimating unit 23 advances to the process of S15 when the elapsed time T from the polishing start is "B (for example, 150 seconds) or more", and the elapsed time T is If it is "less than B second", the process proceeds to S14 (S13). Next, if the elapsed time T from the polishing start is "C (e.g., 900 seconds) seconds or more", the polishing progress state estimating unit 23 proceeds to the process of S16, and the elapsed time T is increased. If it is "less than C second", the process proceeds to S14 (S15). In S15, while ensuring the minimum time of polishing time, it is possible to suppress misdetection of polishing completion due to a change in inclination due to the deviation of the standard deviation in the first half of polishing (Fig. 4). Since it does not detect the deviation of the slope up to 900 seconds). In S16, the polishing progress state estimating unit 23 is based on the standard deviation σ calculated during the period (predetermined period) until "B second ago" on the basis of "elapsed time T from the start of polishing". On the other hand, the slope m is calculated from the linear approximation represented by the formula Y = mX + b (where X: elapsed time, Y: standard deviation (σ), m: slope, and b intercept). Next, the polishing progress estimating unit 23 proceeds to S18 when the slope m is "threshold value (for example, 0 or more)", and when the slope m is "less than the threshold value", the process proceeds to S14. To proceed (S17).

Specifically, in the polishing progress state estimating unit 23, in this step S17, the slope m is equal to or greater than the threshold value (that is, the variation in the deviation of the "upper plate load current value" is greater than or equal to the predetermined level). Then, it is estimated that the wafer W has been polished to the completion target thickness, and the process proceeds to S18. That is, the inclination m changes from a negative inclination to a positive inclination, for example, as shown in FIG. 4. Therefore, by making the slope m "threshold (for example, 0 or more)", the thickness dimension of the wafer W being polished is the thickness (thickness) of the carrier 6a of the polishing apparatus 1. Can be estimated to be almost the same as the dimension), and can be estimated to be polished to the target thickness of the wafer W. On the other hand, in the step S17, in the polishing progress state estimating unit 23, if the slope m is equal to or less than the threshold value (that is, the variation in the deviation of the "upper plate load current value" is less than or equal to the predetermined level), the wafer is used. It is assumed that (W) has not been polished to the completion target thickness, and the flow advances to S14.

In S18, the polishing progress estimating unit 23 estimates the polishing end time, and terminates the polishing process of the wafer W through the drive control unit 21. Specifically, the polishing progress estimating unit 23 supplies the drive control unit 21 when the slope m is equal to or greater than the threshold value (that is, when the variation in the deviation of the "upper plate load current value" is larger than the predetermined level). A signal indicating that the polishing finish point is transmitted. Moreover, when the drive control part 21 receives the signal which shows that it is the completion | finish time of grinding | polishing, each part (lift drive part 7, the upper rotation drive part 8a, the lower rotation drive part 8b, and grinding | polishing) of the grinding | polishing apparatus 1 is polished. Various command signals (control signals) are sent to the liquid supply unit 11 and the like to terminate the polishing process.

On the other hand, in S13, the grinding | polishing progress estimation part 23 increments "a" to "T" until it becomes "T≥B" in S13 (T ← T + a), S12 mentioned above The process shifts to S12, S13, and S14, and repeats the process. In addition, in S15, the grinding | polishing progress estimation part 23 increments "a" to "T" until it becomes "T≥C" in S15 (T ← T + a), and is mentioned above. The process proceeds to one S12, and the processes of S12, S13, S14, and S15 are repeated. On the other hand, when it progresses from S15 to S16, the grinding | polishing progress estimation part 23 increments "a" to "T" until it becomes "tilt (m) ≥ threshold value" in S17, (T? T + a), the process proceeds to S12 described above, and the processes of S12, S13, S14, S15, S16, and S17 are repeated until S17 becomes " tilt m &gt;

Thus, by repeating the processing of "S12, S13, S14, S15, S16, S17", the standard deviation of the "upper plate load current value" monitored in the last A second (constant time A) is measured. The inclination in B second (predetermined period B) can be calculated for every reference time (a second).

Thus, in this embodiment, the standard deviation (sigma) of the "upper plate load current value" monitored in the recent predetermined elapsed time (constant time (A second)) is calculated for each reference time (every a second). Since the progress of polishing of the wafer W is determined by the slope of the linear approximation of the standard deviation σ within the predetermined elapsed time (predetermined period (B seconds)), the progress of polishing near the carrier thickness is performed in real time. It can be estimated as

As described above, according to the polishing method of the wafer (see FIGS. 9 and 10) and the polishing apparatus 1 according to the present embodiment, as compared with the method by the "management of polishing time based on experience" of the prior art, The completed thickness of the wafer W can be brought close to the "target thickness" without increasing the labor of the operator, and the deterioration of the flatness of the wafer W due to the lack of polishing can be suppressed. In addition, this invention is not limited to embodiment mentioned above, A various change is possible within the range of the summary.

For example, in the above-described embodiment, the "upper plate load current value" is monitored in order to estimate the progress of the wafer W polishing process, but is not particularly limited thereto. The "upper plate load current value" is only one example of a signal that changes due to the frictional resistance caused by the polishing of the wafer W and the carrier 6a. Any device detection value that changes due to the frictional resistance can be used to estimate the progress of the wafer W polishing process. Specifically, the "bottom plate load current value", not "top plate load current value" is monitored, and the standard deviation σ of the monitored "bottom plate load current value" is calculated for each reference time, and the calculation is performed. The progress of the wafer W polishing process may be estimated from the change pattern of the transition of the standard deviation σ.

In the above-described embodiment, the standard deviation of the "upper plate load current value" monitored within the predetermined elapsed time (constant time (A second)) is calculated for each reference time (a second), and within the predetermined elapsed time. The slope by linear approximation of (predetermined period (B seconds)) was calculated, but the target within this predetermined elapsed time (constant time (A seconds), predetermined period (B seconds)) or reference time (a seconds) It can set suitably according to the magnitude | size of the wafer W etc. which are used. For example, within a predetermined elapsed time (constant time (A second)) becomes "10 to 300 seconds", and the reference time (a second) becomes "0.1 second to 10 seconds", and within a predetermined elapsed time ( It is preferable that the predetermined period (B seconds) is set to "10 to 300 seconds".

In addition, in the above-mentioned embodiment, although the progress of the grinding | polishing process was estimated by the slope by the linear approximation of the standard deviation of the monitored apparatus detection value (upper surface load current value etc.), it is not limited to this in particular. Even if it is other than the slope by linear approximation, if it is an index (for example, the difference between the standard deviation calculated in real time and the standard deviation before a predetermined time), it is applicable to this invention. Specifically, as shown in Fig. 10, S16 in Fig. 9 is " calculated inclination m by linear approximation of? Before B seconds based on T " The difference in the standard deviation is calculated by substituting "d (difference) ≥ threshold value?" Of S17 with "d (difference) ≥ threshold value" in S17 "to calculate the difference d of? It can be set as the flowchart which shows the processing procedure of estimating polishing progress by displaying a pattern by difference. The flow of the flowchart is the same as that of the flowchart (Fig. 9) in the case where the change pattern of the standard deviation is indicated by the slope.

Next, the grinding | polishing method (and grinding | polishing apparatus) which concerns on this embodiment is further demonstrated based on an Example. In the present Example, the double-side polishing process of the wafer W was progressed according to the said 2nd Embodiment, and the effect of this invention was verified.

EXAMPLE 2 In Example 2, 20 cycles of double-side polishing of the φ300 mm silicon wafer W were carried out using the polishing apparatus 1 (flow chart of FIG. 9) described above under the following conditions. It was. In addition, in the present Example 2, the thickness target value of the completed wafer W was made "775 micrometers." In addition, the carrier 6a used the stainless steel as a base material, and coat | covered the DLC film | membrane on the surface of the base material, and the thing of thickness "775 micrometers" was used.

In addition, in the apparatus detection value for estimating the polishing completion point, the standard deviation of 60 seconds per second is used in the same manner as in the above-described second embodiment (flow chart of FIG. 9) using the "upper plate load current value". Was calculated, and the slope by linear approximation was calculated from the standard deviation before 150 seconds, and the time point at which the slope calculated at the polishing time of 900 seconds or more became "0 (threshold)" or more was estimated as the end time of polishing. In addition, the grinding | polishing apparatus 1 uses the type which simultaneously polishes five wafers W (one wafer W per carrier 6a) between the upper surface plate 2 and the lower surface plate 3. It was. As the polishing cloths 4 and 5, those made of hard polyurethane were used. In addition, the abrasive | polishing agent used the colloidal silica aqueous solution, and performed supply amount control, supply temperature control, and pH control. In addition, the working pressure was "150g / cm <2>".

Then, "average value", "standard deviation", "maximum value" and "minimum value" for the "center thickness", "GBIR" and "SFQR maximum value" of each of the 100 wafers W polished by the above-described conditions. ", The result shown in Table 1 was obtained.

Example 3 In Example 3, using the polishing apparatus 1 (flow chart of FIG. 10) described above, 20 cycles of double-side polishing of a φ300 mm silicon wafer W were performed under the following conditions. It was. Specifically, the thickness target value of the finished wafer W was set to "775 micrometers" similarly to Example 2 mentioned above. In addition, the carrier 6a used the stainless steel as a base material, and coat | covered the DLC film | membrane on the surface of the base material, and the thing of thickness "775 micrometers" was used. In addition, the device detection value for estimating the polishing completion point is 60 seconds per second using the "upper plate load current value" as in the second embodiment (the flowcharts in FIGS. 8 and 10) described above. The standard deviation was calculated, the difference with the standard deviation of 150 seconds ago was calculated, and the time point at which the difference calculated at the polishing time of 900 seconds or more became "0 (threshold)" or more was estimated as the end point of polishing. In addition, the polishing apparatus 1 is similarly to the second embodiment, between the upper surface plate 2 and the lower surface plate 3, five wafers W (one wafer W for one carrier 6a). ) Was used to simultaneously polish. As the polishing cloths 4 and 5, those made of hard polyurethane were used. In addition, the abrasive | polishing agent used the colloidal silica aqueous solution, and performed supply amount control, supply temperature control, and pH control. In addition, the working pressure was "150g / cm <2>". Then, "average value", "standard deviation", "maximum value" and "minimum value" for the "center thickness", "GBIR" and "SFQR maximum value" of each of the 100 wafers W polished by the above-described conditions. ", The result shown in Table 3 was obtained.

COMPARATIVE EXAMPLE 2 In this comparative example 2, by double-sided polishing which made polishing time constant, double-sided polishing of the silicon wafer W of (phi) 300mm is carried out 20 cycles under the following conditions similarly to the Example mentioned above. Proceeded.

Specifically, the thickness target value of the finished wafer W was set to "775 micrometers" similarly to the above-mentioned embodiment. In addition, the carrier 6a used the stainless steel as a base material, and coat | covered the DLC film | membrane on the surface of the base material, and the thing of thickness "775 micrometers" was used.

In the same manner as in the above embodiment, the polishing apparatus simultaneously polishes five wafers W (one wafer W for one carrier 6a) between the upper surface plate 2 and the lower surface plate 3. Type was used. As the polishing cloths 4 and 5, those made of hard polyurethane were used in the same manner as in the above examples. In addition, the abrasive | polishing agent carried out supply quantity management, supply temperature management, and pH management using the colloidal silica aqueous solution similarly to the said Example. In addition, the working pressure was "150g / cm <2>". In addition, the grinding | polishing time was made into "1500 second."

Then, "average value", "standard deviation", "maximum value" and "minimum value" for the "center thickness", "GBIR" and "SFQR maximum value" of each of the 100 wafers W polished by the above-described conditions. ", And the result of Table 3 was obtained.

Example 1

Example 2
Comparative Example




Center thickness
(Μm)
medium

774.9
774.9
775.4
Standard Deviation

0.19
0.17
0.27
Value

775.4
775.3
775.8
Minimum value

774.7
774.8
774.7




GBIR
(Nm)
medium

144
140
171
Standard Deviation

20
18
47
Value

187
195
301
Minimum value

96
94
98




SFQR
(Nm)
medium

22
21
24
Standard Deviation

2
2
4
Value

27
25
36
Minimum value

19
19
18

From Examples 2, 3 and Comparative Example 2 described above, according to the polishing method according to the present invention, it was confirmed that the variation of the finished wafer thickness and flatness can be reduced as compared to the method of polishing both sides with a constant polishing time. .

Claims (13)

It is a grinding | polishing method of the semiconductor wafer using the grinding | polishing apparatus which grind | polishes both surfaces of the said semiconductor wafer simultaneously by clamping the semiconductor wafer hold | maintained by the carrier by the up-down rotation plate, and rotating the said up-down rotation plate,
Monitoring the surface load current value of the polishing apparatus when both surfaces of the semiconductor wafer are polished simultaneously;
Calculating the standard deviation of the surface load current value within a predetermined time for each reference time using the monitored surface load current value, and estimating the progress of the polishing from the change of the calculated standard deviation. A polishing method of a semiconductor wafer. The method of claim 1,
And when the standard deviation reaches a predetermined value, estimating the end point of polishing. delete It is a polishing device of a semiconductor wafer which simultaneously polishes both surfaces of the said semiconductor wafer by pinching the semiconductor wafer hold | maintained by the carrier by the up-and-down rotation plate, and rotating the said up-and-down rotation plate,
A detection unit for monitoring a plate load current value when both surfaces of the semiconductor wafer are polished simultaneously;
A polishing progress estimating unit which calculates the standard deviation of the plate load current value within a predetermined time for each reference time using the monitored plate load current value, and estimates the progress of polishing from the change of the calculated standard deviation. A polishing apparatus for a semiconductor wafer, comprising: 5. The method of claim 4,
The carrier is formed of a material having a friction coefficient smaller than that of the semiconductor wafer. 5. The method of claim 4,
The carrier is formed by coating a surface of a substrate with a material having a smaller coefficient of friction than the semiconductor wafer. delete delete It is a grinding | polishing method of the semiconductor wafer using the grinding | polishing apparatus which grind | polishes both surfaces of the said semiconductor wafer simultaneously by clamping the semiconductor wafer hold | maintained by the carrier by the up-and-down rotation plate, and rotating the said up-and-down rotation plate,
Monitoring the surface load current value of the polishing apparatus when both surfaces of the semiconductor wafer are polished simultaneously;
Using the monitored platen load current value, the standard deviation of the platen load current value within a predetermined time is calculated for each reference time period,
From the linear approximation represented by the formula of Y = mX + b (where X: elapsed time, Y: standard deviation (σ), m: slope, b: intercept) with respect to the standard deviation calculated in the predetermined period, The slope m is calculated to obtain a change pattern of the slope m,
And a step of estimating the end point of polishing when the inclination m satisfies the condition of " above a predetermined threshold value &quot;. It is a grinding | polishing method of the semiconductor wafer using the grinding | polishing apparatus which grind | polishes both surfaces of the said semiconductor wafer simultaneously by clamping the semiconductor wafer hold | maintained by the carrier by the up-and-down rotation plate, and rotating the said up-and-down rotation plate,
Monitoring the surface load current value of the polishing apparatus when both surfaces of the semiconductor wafer are polished simultaneously;
Using the monitored platen load current value, the standard deviation of the platen load current value within a predetermined time is calculated for each reference time,
The difference between the latest standard deviation calculated and the standard deviation calculated a predetermined time is calculated, and the change pattern of the difference is obtained.
And a step of estimating the end point of polishing when the difference satisfies the condition of "at least a predetermined threshold value". delete It is a polishing device of a semiconductor wafer which simultaneously polishes both surfaces of the said semiconductor wafer by pinching the semiconductor wafer hold | maintained by the carrier by the up-and-down rotation plate, and rotating the said up-and-down rotation plate,
A drive control unit for controlling a rotation operation of the upper and lower rotating platens;
A detection unit for monitoring a plate load current value when both surfaces of the semiconductor wafer are polished simultaneously;
A polishing progress estimating unit which calculates the standard deviation of the plate load current value within a predetermined time for each reference time using the monitored plate load current value, and estimates the progress of polishing from the change of the calculated standard deviation. Equipped,
The polishing progress state estimating unit calculates the standard deviation of the surface load current value within a predetermined time period for each reference time period,
From the linear approximation represented by the formula of Y = mX + b (where X: elapsed time, Y: standard deviation (σ), m: slope, b: intercept) with respect to the standard deviation calculated in the predetermined period, The slope m is calculated to obtain a change pattern of the slope m,
When the inclination m satisfies the condition of " above a predetermined threshold value, " a polishing end signal is transmitted to the drive control section to stop the rotation operation of the rotating surface plate and finish polishing. A polishing apparatus for a semiconductor wafer. It is a polishing device of a semiconductor wafer which simultaneously polishes both surfaces of the said semiconductor wafer by pinching the semiconductor wafer hold | maintained by the carrier by the up-and-down rotation plate, and rotating the said up-and-down rotation plate,
A drive control unit for controlling a rotation operation of the upper and lower rotating platens;
A detection unit for monitoring a plate load current value when both surfaces of the semiconductor wafer are polished simultaneously;
A polishing progress estimating unit which calculates the standard deviation of the plate load current value within a predetermined time for each reference time using the monitored plate load current value, and estimates the progress of polishing from the change of the calculated standard deviation. Equipped,
The polishing progress state estimating unit calculates the standard deviation of the surface load current value within a predetermined time for each reference time,
Calculate the difference between the latest standard deviation calculated and the standard deviation calculated a predetermined time, and obtain the change pattern of the difference;
When the difference satisfies the condition of " more than a predetermined threshold value, " a semiconductor end signal is transmitted to the drive control section to stop the rotation operation of the rotating surface plate and terminate the polishing. Wafer Polishing Device.

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