JP2005268330A - Polishing method of semiconductor wafer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide the polishing method of a semiconductor wafer whereby error and dispersion in a polishing amount can be reduced without being affected even though a new polishing cloth is used with no clogging caused therein or a polishing cloth causing a degree of clogging after the use of the new polishing cloth for several times. <P>SOLUTION: The polishing method of the semiconductor ware using a grinding apparatus comprises a rotatable surface plate onto the upper side of which the polishing cloth is adhered; and a rotatable polishing head located opposite to the surface plate and on the lower side of which the semiconductor wafer is supported and controls the polishing time, depending on an integrated value of detected temperature changes on the polishing cloth during the polishing in the case of polishing the surface of the bare wafer. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for polishing a semiconductor wafer.

  When finishing the surface of a semiconductor wafer into a mirror surface, CMP (Chemical Mechanical Polishing) is generally used. This is done by attaching a polishing cloth on the upper surface of a rotatable surface plate, pressing a semiconductor wafer held by a rotatable polishing head placed opposite to the polishing cloth against the polishing cloth, and supplying an abrasive. This is a method for polishing one surface of a semiconductor wafer by rotating a disk and a polishing head in the same direction.

  Incidentally, in such polishing of a semiconductor wafer, particularly patterning for device formation on the surface, and polishing of a bare wafer in which irregularities are not formed, management of the polishing amount is not particularly regarded as important. For this reason, bare wafers are polished by a method in which the polishing time is kept constant and the number of times the polishing cloth is used is managed.

  However, in such polishing, the polishing speed decreases due to the decrease in the polishing temperature due to clogging of the polishing cloth, resulting in a large error in the polishing amount, resulting in variations in the finish and a large product yield. Had an influence.

As a prior art for solving the above problems, an integral value of a current generated by an upper surface plate motor driver for feedback control of the upper surface plate is measured, and this integral value is measured in advance. There is a method of detecting the end point by comparing with the integral value in (Patent Document 1). In addition, it detects the drive current of at least one of the upper surface plate drive motor and the lower surface plate drive motor during polishing and the drive current during idling without polishing, and calculates the drive current during idling from the drive current during polishing. A method of detecting the polishing end point based on the result of comparing the integrated current value obtained by integrating the subtracted end point reversal current with a preset processing end point threshold (Patent Document 2), and a plurality of different materials There is a method (Patent Document 3) for detecting an end point of a polishing process based on a temperature change of a polishing portion that occurs when polishing a workpiece laminated in layers in a cutting direction.
JP-A-10-180625 (Claims) JP-A-9-70753 (Claims) JP-A-7-94452 (Claims)

  However, the inventions of Patent Document 1, Patent Document 2 and Patent Document 3 described above are all methods for detecting a polishing end point of a workpiece in which a step or a plurality of different materials are laminated. At this point, the change is detected by using the drive current, temperature change, etc., and no polishing method corresponding to the decrease in the polishing rate between the polishing use cycles targeted by the present invention is described. There is no suggestion.

  This invention can be applied to a new polishing cloth that is not clogged, or a polishing cloth that has been clogged to some extent by using this polishing cloth several times, regardless of the circumstances. An object of the present invention is to obtain a semiconductor wafer polishing method in which no error occurs.

  The present invention uses a polishing apparatus comprising a rotatable surface plate with a polishing cloth affixed to the upper surface, and a rotatable polishing head disposed opposite to the surface plate and holding a semiconductor wafer on the lower surface, In polishing a surface of a bare wafer, a temperature change during polishing on the polishing cloth is detected, and a polishing time is controlled by an integrated value of the temperature change (claim 1). 2. The semiconductor wafer polishing method (claim 2) and the polishing head according to claim 1, wherein the portion for detecting the temperature change is a surface opposite to a bare wafer polishing surface. A cavity, an elastic sheet stretched below to hold the semiconductor wafer, and an air supply hole for supplying air to the cavity, the elastic sheet having the semiconductor wafer It is a method for polishing a semiconductor wafer according to claim 1 or 2, characterized in that the sensor for measuring the temperature during polishing is provided (claim 3).

  According to this invention, in polishing a bare wafer, it is not affected by a change in polishing rate due to clogging of the polishing cloth, and an error or variation in the polishing amount can be reduced. The semiconductor wafer polishing method according to the present invention can be applied to batch polishing in addition to single-wafer single-side polishing, and can also be applied to double-side polishing depending on the location of the temperature sensor.

  An embodiment of the present invention will be described below with reference to the drawings.

  FIG. 1 is an explanatory view showing a side surface of an apparatus for carrying out the semiconductor wafer polishing method of the present invention. In FIG. 1, reference numeral 1 denotes a surface plate disposed on the lower side, and a polishing cloth 2 is held on the upper surface thereof. Reference numeral 3 denotes a polishing head disposed on the upper side facing the surface plate 1.

  The semiconductor wafer W is held on the polishing head 3 and the surface plate 1 and the polishing head 3 are rotated in the same direction while being pressed against the polishing cloth 2 to supply the polishing agent from the polishing agent supply nozzle 4. The polishing process is started. When polishing of the semiconductor wafer is started, the temperature on the polishing cloth rises due to frictional heat between the polishing cloth and the semiconductor wafer or reaction heat with the abrasive. Reference numeral 5 denotes a temperature detection means for detecting a temperature change on the polishing pad.

Next, the polishing end determination means 6 will be described. The temperature change of the polishing pad detected by the temperature detecting means 5, taken as a temperature change with respect to the polishing time, and calculates the integral values S ₁ of the temperature change. By this means, an integrated value S ₀ of the temperature change with respect to the polishing time in a state where the target polishing amount to be removed in polishing is grasped in advance or the temperature change with respect to the polishing time within the number of times of use of the polishing cloth is calculated and recorded. The integral values S ₁ and S ₀ are compared. If S ₀ > S ₁ , the processing is continued, and if S ₀ ≦ S ₁ , the processing is terminated, and each signal is transmitted to the polishing apparatus control means 7 to determine whether processing is continued.

  Note that if the value varies slightly depending on the polishing conditions (polishing head pressing load, polishing head, surface plate rotation speed, etc.), or if the quality differs from one polishing cloth to another, multiply either integral value by the correction value (α). Also good. In this way, the temperature during polishing is detected by the surface temperature on the polishing cloth, this temperature change is regarded as a temperature change with respect to the polishing time, and the polishing time is controlled by the integrated value, thereby causing clogging of the polishing cloth. It is possible to reduce polishing amount errors and variations without being affected by a decrease in polishing rate.

  A second embodiment of the present invention is shown in FIG. The polishing head 3 is provided with a cavity portion 8 inside and an air supply hole 9 communicating with the cavity portion 8 at the upper portion. The air supply hole 9 includes an air supply source and an air supply pipe (not shown). It is connected.

  Further, the lower side of the cavity 8 of the polishing head 3 is opened, and an elastic sheet 10 such as silicon rubber is stretched in an airtight manner using an annular seal 11. As a result, the cavity 8 of the polishing head 3 can be a sealed air chamber 12.

  Furthermore, a temperature sensor 13 is attached to the cavity 8 side of the elastic sheet 10 so that the temperature change of this portion during polishing can be measured in real time. A wafer W to be polished is held on the lower surface of the elastic sheet 10. The wafer W is held, for example, so as to engage with the lower opening of the polishing head 3. The wafer W is pressed against the polishing cloth 2 on the surface plate 1 by supplying air from an air supply hole 9 provided in the upper part of the polishing head 3. The surface plate 1 and the polishing head 3 are each rotated in the direction of the arrow by a driving source (not shown).

  In order to polish the wafer using the above apparatus, the wafer W is held on the lower surface of the elastic sheet 10 below the polishing head 3 as shown in FIG. Next, air is supplied from an air supply source (not shown) to the air chamber 12 through the supply hole 9. As a result, the wafer W under the polishing head 3 is always pressed onto the polishing cloth 2 via the elastic sheet 10. In this state, when the surface plate 1 and the polishing head 3 are rotated in the directions of the arrows, the surface of the wafer W is polished. By polishing the wafer W, the wafer W generates frictional heat, and the heat is transmitted to the elastic sheet 10 in contact therewith to raise the temperature of the elastic sheet 10. When this temperature rises, the state is detected by a temperature sensor 13 attached to the back surface of the elastic sheet 10, and it is determined whether or not processing is continued by a polishing end determination unit similar to that shown in FIG. The description after the temperature detecting means is as described above.

  That is, the temperature change during the polishing temperature is detected as the temperature change of the elastic sheet, that is, the temperature change of the opposite surface of the wafer W through the elastic sheet, and this temperature change is regarded as the temperature change with respect to the polishing time. Thus, by controlling the polishing time based on the integral value, it becomes possible to reduce errors and variations in the polishing amount without being affected by a decrease in polishing speed due to clogging of the polishing cloth.

  There is a certain relationship between the polishing amount of the wafer and the polishing temperature. However, this relationship changes depending on the clogging of the polishing cloth for polishing the wafer. That is, in the polishing of a wafer, usually, a large number of wafers are polished with one polishing cloth, and when the polishing cloth is clogged or worn out, the polishing cloth is replaced with a new one. Start polishing the wafer. Polishing with a new polishing cloth just replaced has naturally good polishing performance, and polishing is completed in a relatively short time. In this case, the polishing temperature rises significantly during polishing. However, if the wafer is repeatedly polished with the same polishing cloth, the polishing cloth naturally becomes clogged and the polishing efficiency of the wafer also decreases.

  In this state, the temperature rise accompanying the polishing is lower than that when a new polishing cloth is used, and the polishing amount is reduced unless the polishing time is lengthened. That is, this state is a relationship between the polishing time and the polishing temperature. As shown in FIG. 3, when the polishing cloth is not clogged 14, the temperature rises remarkably, while when the polishing cloth is clogged 15 Temperature rise is low. In this case, since the polishing efficiency is poor, it is necessary to lengthen the polishing time.

FIG. 4 illustrates this state in relation to the polishing end point. The polishing end point shown here is the polishing end time corresponding to the target polishing amount. In FIG. 4, considering the case 16 where the polishing cloth is not clogged, the temperature rise during the polishing process is remarkable, but the polishing time to the polishing end point A where the integrated value of the temperature rise becomes a predetermined value is short. On the other hand, when the polishing cloth is clogged, the temperature rise during the polishing process is low, but the polishing time to the polishing end point B where the integrated value of the temperature rise in that case becomes a predetermined value is the above clogging. It needs to be longer than if none. Therefore, an integral value S ₀ of the temperature rise corresponding to a desired polishing amount (for example, an integrated value when there is no clogging) is obtained in advance, and the integrated value S ₁ associated with the temperature change during polishing is S ₀ = by continuing the polishing until S _1, when no case or clogging the polishing cloth with a clogging, or in any case where the intermediate, may terminate polished at an appropriate polishing amount It becomes possible.

  According to this method, even when the polishing pressure or the like is changed, the evaluation is performed with the integrated value of the temperature change, so that the polishing end point can be easily confirmed. In addition, when calculating | requiring the integrated value of the temperature change of the elastic body sheet 10 which is pressing the wafer, either one of the temperature sensors provided in the back surface of the polishing head is used, or a plurality thereof is used. be able to. In addition, the semiconductor wafer used by this invention is applicable suitably for the wafer in which the patterning for device formation, the unevenness | corrugation, etc. are not formed in the surface. When the present invention is applied to a polishing process of a product (discrete device semiconductor substrate such as a diffusion wafer or an epitaxial wafer) whose finish thickness is strictly controlled, a remarkable effect such as an improvement in yield by reducing the finish thickness can be obtained.

Explanatory drawing which shows the apparatus of 1st Embodiment of the wafer grinding | polishing method of this invention. Explanatory drawing which shows the principal part side cross section of the apparatus of 2nd Embodiment of the wafer grinding | polishing method of this invention. The diagram which shows the relationship between grinding | polishing time and grinding | polishing temperature during grinding | polishing of a semiconductor wafer. Explanatory drawing which shows the grinding | polishing end point in case there is no clogging by the relationship between grinding | polishing time and grinding | polishing temperature during grinding | polishing of a semiconductor wafer.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Surface plate, 2 ... Polishing cloth, 3 ... Polishing head, 4 ... Abrasive supply nozzle, 5 ... Temperature detection means, 6 ... Polishing completion determination means, 7 ... Polishing apparatus control means, 8 ... Cavity, 9 ... Air Supply hole, 10 ... elastic sheet, 11 ... annular seal, 12 ... air chamber, W ... wafer, 13 ... sensor.

Claims (3)

Using a polishing apparatus comprising a rotatable surface plate with a polishing cloth affixed to the upper surface and a rotatable polishing head disposed opposite to the surface plate and holding a semiconductor wafer on the lower surface, the surface of the bare wafer In polishing a semiconductor wafer, a temperature change during polishing on the polishing cloth is detected, and a polishing time is controlled by an integral value of the temperature change. The method for polishing a semiconductor wafer according to claim 1, wherein the portion for detecting the temperature change is a surface opposite to a bare wafer polishing surface. The polishing head has a cavity formed inside, an elastic sheet stretched below to hold a semiconductor wafer, and an air supply hole for supplying air to the cavity, and the elastic sheet The method for polishing a semiconductor wafer according to claim 1 or 2, further comprising a sensor for measuring a temperature during polishing of the semiconductor wafer.

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