JP2005288648A - Foreign matter sensing method for double-side polishing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method to work with a double-side polishing device used in polishing etc., for example, of a semiconductor wafer, capable of sensing whether a work and a carrier to be carried to outside a platen has been carried out certainly. <P>SOLUTION: The polishing device is configured so that the work inserted to and held by the carrier is interposed between an upper 1 and a lower rotary platen 2 whereto polishing pads 3 are affixed and the obverse and reverse surfaces of the work are polished simultaneously while slurry is supplied onto the pads 3, wherein a foreign matter sensing method to work with this polishing device is to put the rotary platens 1 and 2 in tight attachment after the work and carrier having finished polishing are carried out from upon the platens. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a double-side polishing apparatus used, for example, for polishing a semiconductor wafer, and more particularly to a method for detecting whether or not a workpiece and a carrier are reliably unloaded when the workpiece and a carrier are unloaded from the surface plate after polishing. .

  A silicon wafer, which is a material of a semiconductor device, is cut out from a silicon single crystal, is subjected to lapping or / and grinding, and is further subjected to a polishing process called polishing. As a polishing apparatus for performing this polishing process, a planetary gear type double-side polishing apparatus is frequently used. A schematic structure of a double-side polishing apparatus of this type will be described with reference to FIGS. 2 (a) and 2 (b). FIG. 2B is a view taken along line B-B in FIG.

  The planetary gear type double-side polishing apparatus is composed of a pair of upper and lower rotating surface plates 1 and 2 with a polishing pad 3 made of polyurethane, hard rubber or the like as the polishing plate, and the rotation center portion between the rotating surface plates 1 and 2 A plurality of carriers 4, 4... Arranged as planetary gears, a sun gear 5 disposed at the center of rotation between the rotating surface plates 1 and 2, and an outer peripheral portion disposed between the rotating surface plates 1 and 2. And a null gear 6.

  The upper rotary platen 1 can be moved up and down, and is placed on the lower rotary platen 2 with a predetermined weight with a plurality of carriers 4, 4. Each carrier 4 holds a wafer 7 such as silicon, which is a workpiece, eccentrically. The sun gear 5 and the internal gear 6 mesh with the plurality of carriers 4, 4... From the inside and the outside, and are normally driven to rotate in the same direction as the lower rotating platen 2. The rotation direction of the upper rotary platen 1 is opposite to the rotation direction of the lower rotary platen 2.

  With the upper rotary platen 1 raised, a plurality of carriers 4, 4... Are placed on the lower rotary platen 2 and the wafer 7 is set in the carrier hole 8 of each carrier 4. Board 1 is lowered. In this state, by rotating and driving the rotating surface plates 1, 2, the sun gear 5 and the internal gear 6, the plurality of carriers 4, 4... Rotate between the rotating surface plates 1, 2 rotating in the opposite direction. While revolving around the sun gear 5. Thereby, both surfaces of the plurality of wafers 7, 7,... Are uniformly polished simultaneously.

  Further, in Patent Document 1, as the silicon wafer has a larger diameter, the planetary gear type double-side polishing apparatus as described above has a larger carrier, and the scale of the apparatus increases (especially, the internal gear becomes larger). Since the cost increases and polishing accuracy decreases, or the large internal gear is formed only of metal, in order to suppress contamination of the wafer due to metal powder generation due to meshing with the carrier, the internal gear is eliminated, There has been proposed a double-side polishing apparatus in which each carrier is rotated at a fixed position by a small gear.

JP 2000-237953 A

  In the above-described double-side polishing apparatus, when the wafer and carrier are carried out of the surface plate after the polishing is completed, the wafer, the carrier, and their broken pieces remain on the surface plate without being reliably performed, and the next batch is polished. May not be performed properly. This is because the handler for loading and unloading onto the surface plate does not attract the entire wafer, and for example, when the wafer is broken in half, it is continued as it is. Further, since the detection of the removal of the handler is determined based on the suction level of the suction cup to the last, the variation in the degree of vacuum of the wafer adsorption with a lot of water is large and the reliability is low. Therefore, if the next batch is processed with such foreign matter remaining on the surface plate, the wafer will be detached from the carrier during processing and all the wafers and the carrier will be damaged, resulting in fatal damage to production. However, even if it does not go so far, problems such as introduction of grease into the wafer due to minute fragments will occur. The situation is particularly serious for devices that perform unattended operations by automatic transport because they cannot be confirmed by the operator.

  In order to improve these problems, the double-side polishing machine is placed in close contact with the vertical rotating surface plate with the wafer and carrier mounted before processing the next batch, and the displacement from the surface plate origin (upper and lower surface plate contact state) Is measured with a linear gauge equipped on the upper surface plate, and the displacement amount at that time is basically the thickness of the wafer because it is the thickest, but intentionally before processing In some cases, a carrier thicker than that of the wafer is used. In this case, the thickness of the carrier is used, and an interlock is provided that does not automatically start processing unless the amount of displacement is within a predetermined range.

  However, this amount of displacement is easily changed by the amount of material consumption of the polishing pad, the thickness before processing of the wafer, or the deflection due to the thermal expansion of the rotating surface plate. It was necessary to widen the range of interlock. In addition, there is a problem that the foreign matter is not detected by this method unless the wafer or carrier of the next batch is set on the foreign matter on the rotating surface plate.

  The present invention has been made in view of the above-described problems, and by detecting the presence or absence of foreign matters such as wafers, carriers and fragments thereof after the completion of polishing, it is possible to stabilize the apparatus after the next batch. The purpose is to reduce operation and generation of scratches.

  According to the first aspect of the present invention, a work inserted and held in a carrier is interposed between a pair of upper and lower rotating surface plates to which a polishing pad is attached, and the front and back surfaces of the work are simultaneously applied while supplying slurry onto the pad. In the polishing apparatus for polishing, the foreign object detection method of the double-side polishing apparatus, wherein after the workpiece and the carrier are unloaded from the surface plate after the polishing is finished, the vertical rotation surface plate is brought into close contact.

  In this way, when the workpiece and carrier are discharged from the rotating surface plate after polishing, in other words, the surface platen is brought into close contact with the rotating surface plate (polishing pad) in a state where nothing basically exists. For example, by measuring the amount of displacement with a linear gauge as a position detection means, it is possible to automatically determine whether the amount of deviation from the origin is within the allowable range. Moreover, it has become possible to detect without using a high-cost detector such as a sensor.

  In addition, it is a foreign object detection method for a double-side polishing machine characterized in that when the vertical rotating surface plate is brought into close contact, the origin of the upper surface plate position is detected at the same time. The value of (origin position) changes over time mainly due to the influence of the polishing pad wear amount and the deflection due to thermal expansion of the surface plate. In order to cope with this, when no foreign object is detected, the contact state at that time is reset as the origin.

Examples of the polishing pad include polyurethane and hard rubber, and the slurry may be a colloidal silica-containing alkaline solution.
In addition, it detects foreign matter such as wafers, carriers, or fragments of them by bringing the vertical rotating surface plate into close contact, and as it detects the upper surface plate position at that time, a linear gauge or the like is used as in the prior art. However, the present invention is not limited to this as long as the position of the surface plate is detected.

  These methods are desirably performed every time the workpiece after polishing is collected, if possible. However, in consideration of productivity and the like, it may be performed once in several batches and may be set as appropriate. These series of operations are fully automatic until an abnormality is detected, and when an abnormality occurs, an operator call is made and this is the first system in which the operator intervenes.

  According to the present invention, it is possible to detect the presence or absence of a foreign substance such as a wafer, a carrier, and fragments thereof after polishing, and the wafer is detached from the carrier during processing, and all the wafers and the carrier are damaged. There will be no fatal damage to production or problems such as the introduction of grease into the wafer due to minute debris, and stable operation for unmanned operation with automatic transfer will be possible.

  Hereinafter, an embodiment of a double-side polishing apparatus according to the present invention will be described with reference to FIGS. 1 (a) and 1 (b). Note that FIG. 1 shows a state in which the wafer as a workpiece and the carrier for holding the workpiece are discharged from the surface plate after being processed. The linear gauge 9 used as the panel position measuring means is simplified as long as it is known at a minimum. The other rotating mechanisms and the like are basically the same as those in FIG. The linear gauge 9 for detecting the position of the upper rotating surface plate is fixed to the frame of the apparatus main body (not shown) and is installed so as to contact the contact 10 provided on the upper rotating surface plate. The distance from the origin (at the time of close contact with the vertical rotating surface plate) can be measured finely with respect to the vertical movement of the upper rotating surface plate. The linear gauge is connected to a control system not shown separately.

  FIG. 1A shows a state in which the upper rotating surface plate 1 is raised to the upper limit position in the pair of upper and lower rotating surface plates 1 and 2 to which the polishing pad 3 of the present invention is attached. (B) shows a state in which the vertical rotating surface plates 1 and 2 are brought into close contact with each other in order to detect foreign matter between the upper rotating surface plate 1 and the lower rotating surface plate 2. The value of the linear gauge 9 at this time is 0 ± 10 μm because the origin is determined at the previous batch processing if there is no foreign matter such as a wafer crack between the vertical rotating surface plates. .

  Using the present invention and the prior art, about 1800 batches of wafers each having a diameter of 200 mm and subjected to processing necessary for double-side polishing such as lapping and etching were tried. The results are shown below in terms of operator intervention rate and scratch rate. Note that the interlock range at this time was set to a range of 30 μm or more of the displacement obtained from the measurement result of the linear gauge 8 with some safety, for the purpose of preventing malfunction.

  As a result, in the method according to the prior art, the operator intervention rate was 0.8% and the scratch occurrence rate was 4.0%, whereas in the method according to the present invention, the operator intervention rate was 0.5% and the scratch occurrence rate was 2.0%. %. In addition, when the upper and lower rotating surface plates 1 and 2 are brought into close contact with each other, the origin of the upper surface plate position is simultaneously reset (zero reset), resulting in an operator intervention rate of 0.08% and a scratch rate of 0.5%. With very good results.

(A) It is a schematic block diagram when the upper rotating surface plate of the double-side polishing apparatus of this invention raises, (b) It is a schematic block diagram when the vertical rotation surface plate of the double-side polishing apparatus of this invention closely_contact | adhered. (A) The schematic block diagram of the conventional double-side polish apparatus, (b) It is a BB line arrow figure of Fig.2 (a).

Explanation of symbols

1 Upper rotating surface plate 2 Lower rotating surface plate 3 Polishing pad 4 Carrier 5 Sun gear 6 Internal gear 7 Work 8 Carrier hole 9 Linear gauge 10 contacts

Claims (2)

  In a polishing apparatus for interposing a work inserted and held in a carrier between a pair of upper and lower rotating surface plates to which a polishing pad is attached, and simultaneously polishing the front and back surfaces of the work while supplying slurry onto the pad, after polishing is completed. A method for detecting foreign matter in a double-side polishing apparatus, wherein a workpiece and a carrier are unloaded from a surface plate and then the upper and lower surface plates are brought into close contact with each other.   2. The foreign object detection method for a double-side polishing apparatus according to claim 1, wherein when the upper and lower surface plates are brought into close contact with each other, the origin of the upper surface plate position is simultaneously determined.

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