JP4326985B2 - Wafer polishing method - Google Patents

Description

  The present invention relates to a wafer polishing method for simultaneously polishing both surfaces of a wafer using a carrier between upper and lower surface plates, and more particularly to a wafer polishing method capable of accurately detecting the end point of polishing from vibrations of the surface plate.

  High integration of semiconductor devices is rapidly progressing, and flatness required for a semiconductor wafer (hereinafter simply referred to as a wafer), which is a material of the semiconductor device, is becoming increasingly severe. Further, from the viewpoint of reducing the manufacturing cost of semiconductor devices, since the diameter of the wafer is being increased, it is more difficult to improve the flatness. For this reason, in the wafer processing process, a process is proposed in which a grinding process is introduced after etching. In the mirror polishing process following grinding, a double-sided polishing method having processing accuracy superior to conventional single-side polishing is proposed. Attention has been paid.

  As a wafer double-side polishing apparatus, a planetary gear type is usually used. This double-side polishing apparatus includes a pair of upper and lower rotating surface plates, a sun gear provided at the center of rotation between the rotating surface plates, and an annular internal gear provided at the outer peripheral portion between the rotating surface plates. Yes. The upper rotary platen can be moved up and down, and is driven up and down by a cylinder that also serves as a pressurizing cylinder, and the rotation direction is set opposite to the rotation direction of the lower rotary platen. A polishing cloth is affixed to the opposing surfaces of the upper and lower rotating surface plates.

  In the polishing operation, a plurality of carriers are set around the rotation center on the lower rotating surface plate with the upper rotating surface plate raised, and a wafer is set on each carrier. A plurality of carriers that are planetary gears mesh with the inner sun gear and the outer internal gear, respectively, and rotatably accommodate the wafer in a wafer accommodation hole called a hole that is eccentric from the rotation center. Instead of setting the wafer on the carrier on the surface plate, the wafer may be combined with the carrier in advance and both may be set on the surface plate at the same time.

  When the setting of the carrier and the wafer is completed, the upper rotating surface plate is slowly lowered, and a plurality of semiconductor wafers are sandwiched between the upper and lower rotating surface plates with a predetermined pressure. Then, the rotating surface plate, the sun gear, and the internal gear are rotated while supplying the polishing liquid between the rotating surface plates. As a result, the plurality of carriers revolve around the sun gear while rotating between the rotating surface plates rotating in the opposite directions. Thus, both surfaces of the plurality of wafers are polished simultaneously.

  The thickness of the carrier used here is set sufficiently thinner than the final finished thickness (target thickness) of the wafer so that a predetermined pressure is reliably applied to the wafer throughout the polishing process. Specifically, in the case of a 12-inch wafer having a final finished thickness of 750 μm, the thickness of the carrier combined therewith is about 650 μm. Further, as the material of the carrier, stainless steel is mainly used in addition to a resin reinforced with glass fiber, for example, epoxy resin, phenol resin, nylon resin.

  In such a double-sided mirror polishing process for wafers, the polishing amount is an important management item not only for improving flatness but also for removing processing distortion and correcting surface roughness up to the previous process. Conventionally, the management is performed by managing the polishing time based on experience.

  That is, the polishing rate in the mirror polishing process varies greatly depending on the polishing conditions, and particularly depends greatly on changes in the condition due to the life of the polishing cloth and the deterioration of the polishing liquid. For this reason, before and after mirror polishing for each batch or process, the wafer thickness is measured with an automatic or manual thickness gauge provided outside the apparatus, and the polishing rate is calculated from the polishing amount and polishing time that are the difference between them. In order to ensure a predetermined polishing amount, feedback control is performed based on the results of setting the polishing time in the next batch or the next process.

  And by proposing a process that introduces a grinding process before the mirror polishing process, the thickness variation between the wafers after grinding has been dramatically improved. As a result, the wafer thickness data can be used as the known information for the mirror polishing process. Thus, the thickness measurement before polishing can be omitted.

  However, unlike the lapping process in which both sides are processed directly between the upper and lower rotating surface plates made of a rigid body and the wafer thickness can be detected by the interval between the surface plates, both surfaces of the wafer are pressed through a polishing cloth made of a viscoelastic material. In the case of the mirror polishing process to be processed, it is impossible to detect the wafer thickness in-process by the surface plate interval, and it is impossible to perform fixed-size polishing. That is, it is difficult to accurately detect the polishing end point when the wafer thickness matches the target value.

  For this reason, various researches have been conducted in various fields regarding a technique for accurately estimating the polishing end point at which the wafer thickness matches the target value, one of which is the polishing end point by acoustic measurement as shown in Patent Document 1. The other is a method of detecting a change in the surface plate driving torque as shown in Patent Document 2.

Japanese Patent No. 3292243

JP 2002-254299 A

  In the case of the method based on acoustic measurement shown in Patent Document 1, since the wafer polishing operation is performed in various noises, it is difficult to find a frequency directly related to the wafer polishing. Even if it exists, the level change is small and the variation is large. For this reason, it is difficult to accurately determine the polishing end point. Moreover, in patent document 1, it is necessary to immerse an acoustic measuring device in the polishing liquid on polishing cloth, and the measurement operation itself is not easy.

  On the other hand, in the method based on torque change shown in Patent Document 2, a thicker carrier is used. Specifically, a carrier that is the same as or slightly thinner than the target thickness (finished thickness) of the wafer is used. That is, conventionally, the thickness of the carrier combined with the wafer is set to be sufficiently thinner than the target thickness of the wafer so as to ensure that a predetermined pressure is applied to the wafer throughout the polishing process. Thereby, even when the thickness of the wafer reaches the target value, the upper and lower polishing cloths are in pressure contact only with the wafer and do not substantially contact the upper and lower surfaces of the carrier. For this reason, a predetermined pressing force from the upper rotating surface plate is applied only to the wafer until the polishing is completed.

  Here, if the polishing is continued even after the wafer thickness reaches the target value, the wafer becomes thinner. When polishing progresses to approximately the same thickness as the carrier, the applied pressure from the upper rotating surface plate is applied to both the wafer and the carrier and dispersed. In addition, there is always no escape space for the polishing liquid supplied between the rotating surface plates via the upper rotating surface plate, and back pressure is generated in the direction of lifting the upper rotating surface plate. The pressure applied to the wafer is drastically reduced. As a result, polishing is substantially stopped. In addition, the torque of the motor that drives the upper and lower rotating surface plates is abruptly reduced. Further, in this state, although the polishing cloth is in contact with the upper and lower surfaces of the carrier, the damage that the carrier receives from the polishing cloth is surprisingly small due to hydroplane polishing.

  Focusing on these facts, using a carrier thickened to the same thickness as the finished wafer thickness, the polishing end point is detected from the rapid decrease in the surface plate drive torque that begins when the wafer thickness becomes equal to the carrier thickness. The method based on torque change shown in Patent Document 2 is used.

  However, this method often does not function sufficiently in actual operation. This is because in actual operation, the torque change of the motor that drives the rotating surface plate is not so large, and it is not easy to accurately determine the end point of polishing. For this reason, the situation where the wafer thickness does not reach the target value or the situation where the carrier is excessively polished occur. Although the carrier receives slight damage from the polishing cloth due to hydroplane polishing, it is inevitable that if the carrier is repeatedly excessively polished, the life of the carrier is shortened.

  An object of the present invention is to provide a wafer polishing method capable of accurately estimating the progress of polishing when simultaneously polishing both surfaces of a wafer using a carrier between upper and lower surface plates.

  In order to achieve the above object, the present inventors paid attention to the frequency distribution of the surface plate vibration, in particular, the change over time of the frequency distribution accompanying the progress of polishing. That is, when attention is paid to the frequency distribution of the surface plate vibration, vibrations of most frequencies do not show regularity and reproducibility with respect to the progress of polishing and do not reflect the progress of polishing. However, from various investigations, it has been found that there are frequencies that increase in level according to the progress of polishing, although there are only a few types. In particular, it has been found that when the above-described thickness-controlled carrier is used, this tendency becomes prominent, and there is a frequency that accurately corresponds to the progress of polishing.

The wafer polishing method of the present invention has been developed based on such knowledge and has the following configuration.
The wafer polishing method of the present invention is a wafer polishing method for polishing both surfaces of the semiconductor wafer simultaneously by holding the wafer to be polished on a carrier and moving it between upper and lower rotating surface plates.
Set the thickness of the carrier to be the same as the target thickness of the wafer or less than the target thickness within the range of 6 μm or less.
One or a plurality of specific frequencies whose vibration level changes reflecting the progress of polishing are selected in advance from the surface plate vibration accompanying polishing of the wafer, and the vibration level change of the specific frequency is detected during polishing. Then, the progress of polishing is estimated from the vibration level change,
The specific frequency is a vibration caused by wafer motion in a carrier.
In the present invention, a point in time when the vibration level of the specific frequency reaches a predetermined level can be regarded as a polishing end point.
The present invention provides a wafer polishing method for simultaneously polishing both surfaces of the semiconductor wafer by holding the wafer to be polished on a carrier and moving the wafer between upper and lower rotating surface plates.
Set the thickness of the carrier to be the same as the target thickness of the wafer or less than the target thickness within the range of 6 μm or less.
One or a plurality of specific frequencies whose vibration level changes reflecting the progress of polishing are selected in advance from the surface plate vibration accompanying polishing of the wafer, and the vibration level change of the specific frequency is detected during polishing. Then, the progress of polishing is estimated from the vibration level change,
The specific frequency is caused by friction between the carrier and the polishing pad and by the friction between the wafer and the polishing pad.
In the present invention, the time point when the vibration level ratio of both the specific frequencies becomes constant can be regarded as the polishing end point.
The present invention provides a wafer polishing method for simultaneously polishing both surfaces of the semiconductor wafer by holding the wafer to be polished on a carrier and moving the wafer between upper and lower rotating surface plates.
Set the thickness of the carrier to be the same as the target thickness of the wafer or less than the target thickness within the range of 6 μm or less.
One or a plurality of specific frequencies whose vibration level changes reflecting the progress of polishing are selected in advance from the surface plate vibration accompanying polishing of the wafer, and the vibration level change of the specific frequency is detected during polishing. Then, the progress of polishing is estimated from the vibration level change,
The specific frequency is assumed to gradually increase from the beginning of polishing and to increase rapidly in the latter half of polishing,
A point in time when both of them become the same level or a point at which a specific ratio is satisfied is regarded as a polishing end point.
In the present invention, a maximum polishing time is set in advance, and polishing can be ended when the maximum polishing time is reached even if the vibration level does not reach the polishing end level.
The present invention provides a wafer polishing method in which a semiconductor wafer to be polished is held on a carrier and moved between upper and lower rotating surface plates to simultaneously polish both surfaces of the semiconductor wafer. Therefore, one or a plurality of specific frequencies whose vibration level changes reflecting the progress of the polishing is selected in advance, and the vibration level change of the specific frequency is detected during polishing, and the polishing level is detected based on the vibration level change. It is for estimating the degree of progress.

  A detailed investigation of the frequency distribution of the platen vibration, especially the time-dependent change accompanying the progress of polishing, reveals that there are several types of frequencies that increase the vibration level reflecting the progress of polishing. What is characteristic is that there are two to three frequencies that are at a low level at the beginning of polishing but rapidly increase in the latter half of polishing. These frequencies are considered to be due to the phenomenon that the main subject of polishing by the polishing cloth shifts from the wafer to the carrier due to a decrease in the wafer thickness as the polishing progresses. The carrier thickness is equal to or slightly less than the target thickness of the wafer. It becomes very noticeable when it is made thinner. From this, it is considered that the frequency that sharply increases in the second half of the polishing is due to the fact that the movement of the wafer starts to become noticeable in the wafer accommodation hole of the carrier in addition to the vibration due to the friction with the carrier.

  That is, when a carrier whose thickness is the same as or slightly thinner than the target finish thickness of the wafer (preferably thin within a range of 6 μm or less) and whose thickness is controlled is used, the polishing cloth is used as the carrier in the second half of polishing. The wafer in the carrier is released from the restraint by the polishing cloth and starts to move relatively freely in the carrier, due to the movement of the wafer in the carrier. Vibration increases. This frequency is specific to the polishing equipment, polishing conditions, etc. If this is investigated in advance to understand the relationship between the vibration level and the degree of polishing, and the vibration level is measured during polishing, the vibration level changes. From this, it is possible to accurately estimate the polishing end point at which the progress of polishing, and consequently the wafer thickness, matches the target value.

  When such a thickness-controlled carrier is used, the movement of the wafer in the carrier is saturated when the wafer in the carrier becomes the same thickness as the carrier. As a result, the increase in the vibration level caused by the movement of the wafer in the carrier is saturated. By grasping this saturation, it is possible to grasp the polishing end point.

  Another type of frequency is a frequency that maintains a relatively high level from the beginning of polishing and gradually increases. This is presumed to be vibration due to polishing of the wafer held by the carrier. A change in level between this frequency and a frequency that rapidly increases in the latter half of the polishing is detected, and even when the two satisfy a specific relationship (for example, when the same level or a specific ratio is satisfied) It is possible to accurately estimate the polishing end point at which the degree of progress, and thus the wafer thickness, matches the target value.

  In addition to this, detection of surface plate vibration is very easy in terms of work. In any case, when the carrier thickness is sufficiently thick with respect to the finished thickness of the wafer and the main body of friction is from the start to the end of polishing in the carrier, a characteristic frequency hardly appears. From this point, It is desirable that the carrier thickness is the same as the finished thickness (target thickness) of the wafer and slightly smaller than this (specifically, it is thin within a range of 6 μm or less).

  In the wafer polishing method of the present invention, the distance between the polishing cloth and the carrier is smaller than that of the conventional one, and the contact pressure between the polishing cloth and the carrier is also increased. The finished thickness is also reduced by the amount of wear, which hinders sizing accuracy. Carrier wear occurs due to friction with the polishing cloth affixed to the surface plate, so the carrier material is a material that has high wear resistance and a low friction coefficient with the polishing cloth, and an alkaline pH 8-12. Those having high chemical resistance in the polishing liquid are preferred. Examples of the carrier material satisfying such conditions include stainless steel, FRP in which a reinforcing fiber such as glass fiber, carbon fiber, or aramid fiber is combined with a resin such as epoxy resin, phenol resin, or polyimide.

  In the wafer polishing method of the present invention, one or a plurality of specific frequencies whose levels reflect the progress of polishing are selected in advance from the surface plate vibration accompanying the polishing of the wafer, and the specific frequency is determined during polishing. By detecting this level change and estimating the progress of polishing from the level change, the finished thickness of the wafer can be accurately matched with the target value. As a result, it is possible to avoid a reduction in wafer flatness due to excessive or insufficient polishing, and it is possible to avoid shortening the carrier life due to excessive polishing, and it is possible to economically manufacture a high-quality wafer.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of a double-side polishing apparatus for explaining an embodiment of the present invention, FIG. 2 is a graph showing a frequency distribution in a platen vibration and its change with time, and FIG. 3 is a graph showing a change in level of a specific frequency over time. It is a graph to show.

  As shown in FIG. 1, the double-side polishing apparatus is disposed inside an annular lower surface plate 1 that is horizontally supported, an annular upper surface plate 2 that faces the lower surface plate 1 from above, and an annular lower surface plate 1. The sun gear 3 is provided.

  The lower surface plate 1 is rotationally driven by a motor. The upper surface plate 2 is suspended from a cylinder via a joint and is rotationally driven in a reverse direction by a motor different from the motor that drives the lower surface plate 1. The upper surface plate 2 is equipped with a polishing liquid supply system including a tank for supplying the polishing liquid between the upper surface plate 2 and the lower surface plate 1. The sun gear 3 is also rotationally driven independently by a motor different from the motor that drives the surface plate.

  On the opposing surfaces of the lower surface plate 1 and the upper surface plate 2, a polishing cloth made by impregnating a urethane resin into a nonwoven fabric or a polishing cloth made of foamed urethane or the like is affixed.

  In the polishing operation, first, the upper surface plate 2 is raised and separated from the lower surface plate 1, and in this state, a plurality of carriers 4 are set on the lower surface plate 1 so as to surround the sun gear 3. Each set carrier 4 meshes with an inner sun gear 3 and an outer ring-shaped internal gear (not shown). Each carrier 4 is a thickness control type that is set to be equal to or slightly thinner than the target value of the final finished thickness of the wafer 5, and the hole that accommodates the wafer 5 is formed at an eccentric position.

  When a predetermined number of carriers 4 are set on the lower surface plate 1 and the wafers 5 are set in the carriers 4, the upper surface plate 2 is lowered and a predetermined pressure is applied to each wafer 5. In this state, the lower surface plate 1, the upper surface plate 2, the sun gear 3, and the internal gear are rotated in a predetermined direction at a predetermined speed while supplying a polishing liquid between the lower surface plate 1 and the upper surface plate 2.

  As a result, a so-called planetary motion in which the plurality of carriers 4 revolve around the sun gear 3 while rotating between the lower surface plate 1 and the upper surface plate 2 is performed. The wafer 5 held by each carrier 4 is in sliding contact with upper and lower polishing cloths in the polishing liquid, and both upper and lower surfaces are polished simultaneously. The polishing conditions are set so that both surfaces of the wafer 5 are uniformly polished.

  During the polishing operation, the vibration level of the rotating upper platen 2 is measured by the acceleration sensor 6 which is a vibration sensor. The measurement band is, for example, 1 to 10 kHz. Here, the acceleration sensor 6 is fixed to the upper surface of the upper surface plate 2, and the measurement data is transmitted through the DC-DC converter 8 using the battery 7 fixed to the upper surface of the upper surface plate 2 as a driving source. Call from. The DC-DC converter 8 and the transmitter 9 are also fixed to the upper surface of the upper surface plate 2 together with the acceleration sensor 6 and the battery 7, and thereby the vibration level of the upper surface plate 2 is adjusted from above the rotating upper surface plate 2, for example. Continuously measure and continue to transmit in the 1 to 10 kHz band.

  The vibration data transmitted from the transmitter 9 is received by the receiver 10 installed on the fixed side of the polishing apparatus. The receiver 10 is driven by an AC adapter 11 and transmits received data to a personal computer 12 that is also installed on the fixed side of the polishing apparatus. The personal computer 12 also serves as a control device for the polishing apparatus, and exchanges signals with the control sequencer 14 in accordance with instructions from the keyboard 13. As a part of the control, vibration data transmitted from the transmitter 9 is analyzed, and automatic determination of the polishing end point is performed. This sequence will be described below.

  As shown in FIG. 2, the vibration characteristics of the upper surface plate 2 measured by the acceleration sensor 6 range from a low frequency of 1 kHz or less to a high frequency of 10 kHz or more. Among these, as the polishing proceeds, the vibration level gradually increases, and there are three frequencies that show peaks at the end of polishing. The first frequency is 2.26 kHz and the second frequency is 5.18 kHz. The third frequency is 6.56 kHz. Among these, the level gradually increases with the progress of polishing, and in particular, 5.18 kHz is picked up which shows a remarkable increase in the latter half and, as a result, shows a remarkable peak at the end of polishing.

  FIG. 3 shows the change with time of the vibration level of this frequency. It has been found from various analyzes in the past that this frequency mainly depends on the rotational motion of the wafer 5 in the carrier 4. That is, when the polishing of the wafer 5 in the carrier 4 progresses and the wafer thickness reaches the target value, the upper surface of the wafer 5 is at the same level as or slightly above the upper surface of the carrier 4, and the friction caused by the polishing cloth is increased. From the wafer receiving hole of the carrier 4 so as to move relatively freely. If this motion is reflected in the vibration of 5.18 kHz and the vibration level is the same, the upper surface level of the wafer 5 relative to the upper surface of the carrier 4 is also substantially the same.

  Therefore, as shown in FIG. 3, the vibration level when the upper surface level of the wafer 5 relative to the upper surface of the carrier 4 corresponds to the target thickness of the wafer 5 is obtained in advance, and this is set as the polishing end level. During the polishing, the vibration level of 5.18 kHz is monitored, and the time when this reaches the polishing end level is defined as the polishing end time when the wafer thickness matches the target value. The vibration level change of 5.18 kHz (FIG. 3) is displayed on the display 15 and can be visually observed at any time by the operator.

  The 5.18 kHz vibration corresponding to the movement of the wafer 5 in the carrier 4 has a significant increase in the vibration level, and accurately corresponds to the upper surface level of the wafer 5 relative to the upper surface of the carrier 4. For this reason, it is possible to accurately estimate the polishing end point from the monitoring of the vibration level of 5.18 kHz. Incidentally, the thickness of the carrier 4 is managed with high accuracy.

  In order to make a more accurate determination, it is effective to change the polishing end level in accordance with a change in polishing conditions with time, for example, the deterioration degree of the polishing cloth, the deterioration degree of the polishing liquid, and the like. In addition, it is effective to set a maximum polishing time and end polishing when the maximum polishing time is reached even if the vibration level does not reach the polishing end level. It is also effective to accumulate past results and predict and correct the polishing end level based on the tendency.

  Furthermore, it is also effective to use it together with a method for estimating the polishing degree from the increase in the torque of the motor that drives the lower surface plate 1 or the torque of the motor that drives the upper surface plate 2.

A 12-inch silicon wafer was actually polished on both sides by the method shown in FIG. The finished target thickness is 750 μm. The double-side polishing apparatus is as shown in FIG. 1, and is a multi-type that simultaneously polishes five wafers between upper and lower surface plates. The polishing cloth was a hard polyurethane plate, the polishing liquid was an aqueous colloidal silica solution, and the polishing pressure was 300 g / cm ² . The carrier used was made of an epoxy resin and had a thickness control type of 747 μm which was only 3 μm thinner than the target thickness of the finished wafer.

  As a result of polishing for 10 consecutive cycles, the variation in the finished thickness is GBIR (Global Backside Ideal-reference-plane Range), which is one of the methods for measuring the variation in thickness. The difference was controlled to 0.2 μm. Incidentally, the variation in the finished thickness when the polishing stop time is managed by the change in the surface plate driving torque is about 0.3 μm under the same polishing conditions. Further, when a carrier having a normal thickness (about 650 μm) is used and the polishing stop time is managed by time management based on an empirical rule, the variation in the finished thickness is about 0.6 μm.

  Here, the frequency used for estimating the polishing degree is 5.18 kHz, but this is a value specific to the polishing apparatus and polishing conditions, and therefore needs to be changed according to the polishing apparatus and polishing conditions. Needless to say.

  FIG. 4 is a graph showing the level change with time of another specific frequency.

  Here, the level change with time of two kinds of frequencies is shown. One is 2.26 kHz, and the other is 1.43 times the vibration level of 6.56 kHz. Both 2.26 kHz and 6.56 kHz are specific frequencies showing the peaks in FIG. Here, 2.26 kHz is considered to be mainly attributable to the friction between the carrier and the polishing cloth, and is at a low level at the start of polishing, but increases rapidly with the progress of polishing, and the degree of increase accompanying the progress of polishing. Is big. On the other hand, the vibration level at 6.56 kHz is higher overall as compared to 2.26 kHz, and the degree of increase accompanying the progress of polishing is small. This is considered to be mainly caused by the friction between the wafer and the polishing pad.

  It should be noted that the vibration level ratio of both frequencies is constant (1.43 here) at the end of polishing when the wafer thickness matches the target thickness. This means that the upper surface level of the wafer is aligned with the upper surface level of the carrier, and they are rubbed with an abrasive cloth in the same manner. Therefore, if the time when the vibration level of 2.26 kHz and the vibration level of 5.56 kHz satisfy a certain ratio is regarded as the polishing end point, it is possible to accurately determine the end.

  Further, as shown in FIG. 5, there may be a frequency at which the increase in the vibration level is saturated and the rising curve becomes flat at the end of polishing due to the relationship between the finished thickness of the wafer and the carrier thickness. This is because, as described above, when the wafer in the carrier becomes almost the same thickness as the carrier, the movement of the wafer in the carrier is saturated. The polishing end point can also be detected from the phenomenon that the rising curve of the vibration level becomes flat.

  In the above embodiment, acceleration is used as the vibration level. However, it can be integrated to obtain an amplitude. In actual operation, it is preferable to use acceleration.

  In the above embodiment, the double-side polishing apparatus is a multi-type that simultaneously polishes a plurality of wafers between the upper and lower surface plates on both sides at the same time. Further, a type in which the carrier is rotated at a fixed position may be used, or a single wafer type in which one wafer is polished on both sides between upper and lower surface plates may be used.

It is a lineblock diagram of a double-side polish device for explaining one embodiment of the present invention. It is a graph which shows the frequency distribution in a surface plate vibration, and its time-dependent change. It is a graph which shows the level change over time of a specific frequency. It is a graph which shows the level change over time of another frequency. It is a graph which shows the level change over time of another frequency.

Explanation of symbols

1 Lower surface plate 2 Upper surface plate 3 Sun gear 4 Carrier 5 Wafer 6 Vibration sensor (acceleration sensor)
7 Battery 8 DC-DC Converter 9 Transmitter 10 Receiver 11 AC Adapter 12 Personal Computer 13 Keyboard 14 Control Sequencer 15 Display

Claims (6)

In the wafer polishing method for polishing both surfaces of the semiconductor wafer simultaneously by holding the wafer to be polished on a carrier and moving it between the upper and lower rotating surface plates,
Set the thickness of the carrier to be the same as the target thickness of the wafer or less than the target thickness within the range of 6 μm or less.
One or a plurality of specific frequencies whose vibration level changes reflecting the progress of polishing are selected in advance from the surface plate vibration accompanying polishing of the wafer, and the vibration level change of the specific frequency is detected during polishing. Then, the progress of polishing is estimated from the vibration level change ,
The specific frequency, wafer polishing and wherein the vibration der Rukoto caused by wafer movement within the carrier. 2. The wafer polishing method according to claim 1, wherein a time point when the vibration level of the specific frequency reaches a predetermined level is regarded as a polishing end time point. In the wafer polishing method for polishing both surfaces of the semiconductor wafer simultaneously by holding the wafer to be polished on a carrier and moving it between the upper and lower rotating surface plates,
Set the thickness of the carrier to be the same as the target thickness of the wafer or less than the target thickness within the range of 6 μm or less.
One or a plurality of specific frequencies whose vibration level changes reflecting the progress of polishing are selected in advance from the surface plate vibration accompanying polishing of the wafer, and the vibration level change of the specific frequency is detected during polishing. Then, the progress of polishing is estimated from the vibration level change ,
2. The wafer polishing method according to claim 1, wherein the specific frequency is caused by friction between the carrier and the polishing pad and by friction between the wafer and the polishing pad. 4. The wafer polishing method according to claim 3, wherein a point in time when the vibration level ratio of both of the specific frequencies becomes constant is regarded as a polishing end point. In the wafer polishing method for polishing both surfaces of the semiconductor wafer simultaneously by holding the wafer to be polished on a carrier and moving it between the upper and lower rotating surface plates,
Set the thickness of the carrier to be the same as the target thickness of the wafer or less than the target thickness within the range of 6 μm or less.
One or a plurality of specific frequencies whose vibration level changes reflecting the progress of polishing are selected in advance from the surface plate vibration accompanying polishing of the wafer, and the vibration level change of the specific frequency is detected during polishing. Then, the progress of polishing is estimated from the vibration level change ,
The specific frequency is assumed to gradually increase from the beginning of polishing and to increase rapidly in the latter half of polishing,
A wafer polishing method characterized in that a point in time when both are at the same level or a point at which a specific ratio is satisfied is regarded as a polishing end point. 6. The polishing apparatus according to claim 1 , wherein a maximum polishing time is set in advance, and polishing is terminated when the maximum polishing time is reached even if the vibration level does not reach the polishing end level. Wafer polishing method.

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