JP2008068372A - Apparatus and method for polishing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus and a method for polishing, wherein the yield of a semiconductor device to be formed on the peripheral portion of a wafer is improved by uniformly flattening the whole surface of the wafer by preventing the over-polishing to be produced on the peripheral portion of the wafer. <P>SOLUTION: The polishing apparatus 10 is composed of a platen 11, a platen turning means, such as a motor, a polishing pad 14 sticking to the surface of the platen, a nozzle 13 for supplying polishing fluid on the surface of the polishing pad, and a polishing head 12 which holds the wafer 15 and presses the surface of the wafer against the surface of the polishing pad. The polishing head includes a retainer ring 16 having a ring portion 16' to be arranged outside the peripheral portion of the wafer. The compressibility of the retainer ring is within 95 to 101% of that of the polishing pad, preferably within 99.4 to 100.6%. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a polishing apparatus and method for polishing a surface of a wafer such as a semiconductor wafer (a material wafer and a device wafer).

  In electronic devices such as telephones, cameras, and computers, semiconductor devices are used as main components for controlling functions and storing or displaying information.

  The surface of a semiconductor device wafer (or workpiece) used for such electronic components is subjected to various processes required in the manufacturing process of various electronic components such as a multilayer wiring process and a coating process after a polishing process, and an inspection process. It is commercialized through.

  Such a series of processes required in the wafer manufacturing stage must be performed with nanometer precision in order to exert the planned component performance and functions in the design stage. High accuracy is required, and even in the polishing process, it is required to highly planarize the surface of the wafer.

  Wafer polishing in such a polishing process that requires high precision is performed on the surface of the polishing pad that is affixed to the surface of the platen while rotating the platen (or platen) that has the polishing pad affixed to the surface. A polishing liquid (for example, slurry in which abrasive grains are dispersed) is supplied, and the surface of the wafer (processed surface) held on the polishing head is pressed onto the polishing liquid, and the wafer is rotated.

  In such polishing, in order to prevent the wafer from jumping out of the polishing head due to lateral stress generated during polishing, a retainer ring having a ring portion disposed on the outer periphery of the wafer held by the polishing head is polished. It is attached to the head (see, for example, Patent Documents 1 to 4).

This retainer ring functions to press the polishing pad with the pressure applied to the ring portion during polishing, prevent over-polishing that tends to occur at the peripheral portion of the wafer, and more evenly planarize the surface of the wafer. .
JP-A-8-148453 JP-A-8-187657 JP-A-10-217109 JP 2000-52241 A

  In recent years, in order to improve the production efficiency of semiconductor devices, the size of wafers to be processed has been increased, and for this reason, improving the yield of the peripheral portion of the wafer has become a technical issue.

  The conventional retainer ring is manufactured from a material different from the polishing pad generally used for polishing. Compared with the polishing pad, a hard material with a low compressibility is used. The surface of the polishing pad rises locally along the inner peripheral edge of the portion pressed against the retainer ring, and the peripheral portion of the wafer on which the surface of the raised polishing pad acts is overpolished.

  As described above, overpolishing at the peripheral portion of the wafer causes distortion of a semiconductor circuit manufactured at the peripheral portion, thereby reducing the yield of the semiconductor device.

  On the other hand, in the conventional technology, since the retainer ring is also pressed against the surface of the polishing pad during polishing, it wears with the progress of polishing, so the wear resistance is improved and the replacement frequency of the retainer ring is reduced. By producing retainer rings using low-priced materials, the polishing cost is only reduced, and the focus is on such low cost, and the above-described over-polishing can be solved. Can not.

  Therefore, an object of the present invention is to improve the yield of a semiconductor device manufactured on the peripheral portion of the wafer by preventing over-polishing generated at the peripheral portion of the wafer and uniformly flattening the entire surface of the wafer. It is providing the grinding | polishing apparatus and method which can be performed.

  The polishing apparatus of the present invention that achieves the above object holds a platen, a means for rotating the platen, a polishing pad attached to the surface of the platen, a nozzle for supplying a polishing liquid to the surface of the polishing pad, and a wafer And a means for rotating the polishing head, further comprising a polishing head configured to press the surface of the wafer against the surface of the polishing pad.

  The polishing head includes a retainer ring having a ring portion disposed on the outer periphery of the wafer. When the wafer is held and the surface of the wafer is pressed against the surface of the polishing pad, the ring portion of the retainer ring is pressed against the surface of the polishing pad.

  The compressibility of the retainer ring is in the range of 95% to 101% of the compressibility of the polishing pad, and preferably in the range of 99.4% to 100.6% of the compressibility of the polishing pad.

  The compression ratio of the retainer ring is in the range of 0.6% to 1.2%.

  The polishing pad and the retainer ring are each made of the same type of synthetic resin, and preferably the polishing pad and the retainer ring are each made of a polyurethane resin.

  The polishing pad and the retainer ring are each made of the same type of non-foamed synthetic resin.

  The surface of the wafer is polished using the polishing apparatus of the present invention.

  The wafer is held by the polishing head, and the surface of the wafer is pressed against the surface of the polishing pad attached to the surface of the platen. At this time, the ring portion of the retainer ring of the polishing head is pressed against the surface of the polishing pad.

  The platen is rotated and the polishing liquid is supplied to the surface of the polishing pad through the nozzle. Then, the polishing head is rotated.

  Since this invention is comprised as mentioned above, there exist the following effects.

  By preventing over-polishing that occurs at the peripheral portion of the wafer and uniformly flattening the entire surface of the wafer, the yield of semiconductor devices manufactured at the peripheral portion of the wafer can be improved.

<Polishing Apparatus> As shown in FIG. 1, the polishing apparatus 10 of the present invention has a platen 11, means (not shown) such as a motor for rotating the platen 11 (in the direction of arrow R), and a surface of the platen 11. The polishing pad 14 is affixed, a nozzle 13 for supplying a polishing liquid to the surface of the polishing pad 14, and a polishing head 12 that holds the wafer 15 and presses the surface of the wafer 15 against the surface of the polishing pad 14. It further includes means (not shown) such as a motor for rotating the polishing head 12 (in the direction of arrow r).

  As shown in FIG. 2, the polishing head 12 includes a retainer ring 16 having a ring portion 16 ′ disposed outside the peripheral portion of the wafer 15.

  When the polishing head 12 holds the wafer 15 and presses the surface of the wafer 15 against the surface of the polishing pad 14 on the platen 11, the ring portion 16 ′ of the retainer ring 16 is pressed against the surface of the polishing pad 14.

  The compressibility of the retainer ring is in the range of 95% to 101% of the compressibility of the polishing pad, and preferably in the range of 99.4% to 100.6% of the compressibility of the polishing pad ( That is, when the compression rate of the polishing pad is 100, the compression rate of the retainer ring is in the range of ± 0.6, and this range is the range of measurement error of the compression rate. In this case, the compression rate of the retainer ring is It is substantially the same as the compressibility of the polishing pad). The compression rate measurement method is shown in Table 1 below, and the compression rate calculation method is shown in Equation 1 below.

  When the compressibility of the retainer ring is in the range of less than 95% of the compressibility of the polishing pad, the polishing pad is deformed too much, so that the polishing pad cannot act uniformly on the surface of the wafer, and the surface of the wafer cannot be made uniform. On the other hand, if the compression ratio of the retainer ring is in a range exceeding 101% of the polishing pad, the retainer ring is deformed too much and the problem that the wafer jumps out of the polishing head during polishing occurs.

  The compression ratio of the retainer ring is in the range of 0.6% to 1.2%.

  The polishing pad and the retainer ring are each made of the same type of synthetic resin. The synthetic resin includes one or two or more selected from polyurethane, polyethylene, polystyrene, polyvinyl chloride, and acrylic resins. Preferably, the polishing pad and the retainer ring are each made of a polyurethane resin.

  The polishing pad and the retainer ring are each made of a non-foamed material of the same type of synthetic resin. In the case of foam, since the voids are dispersed inside, the compressibility of each of the polishing pad and the retainer ring becomes locally different, and the deformation of the polishing pad and the retainer ring causes the wafer to be popped out during polishing. This is a cause of overpolishing.

<Polishing Method> The surface of the wafer is polished using the polishing apparatus of the present invention.

  Please refer to FIG. 1 and FIG. The wafer 15 is held by the polishing head 12 so that the wafer 15 is disposed inside the retainer ring 16, and the surface of the wafer 15 is pressed against the surface of the polishing pad 14 attached to the surface of the platen 11. At this time, the ring portion 16 ′ of the retainer ring 16 of the polishing head 12 is pressed against the surface of the polishing pad 14.

  The platen 11 is rotated in the direction of arrow R, and the polishing liquid is supplied to the surface of the polishing pad 14 through the nozzle 13. The polishing head 12 is also rotated in the direction of the arrow r.

  The polishing liquid includes a polishing slurry in which abrasive grains are dispersed in water or a water-based aqueous solution.

  As the abrasive grains, one kind or two or more kinds of particles made of a material selected from diamond, alumina, ceria and the like are included.

  In order to chemically and mechanically polish the surface of the wafer, the water-based aqueous solution may contain a chemical solution that chemically reacts with the surface of the wafer. Such a chemical solution can be appropriately selected according to the material constituting the surface (surface to be polished) of the wafer. For example, when the material constituting the surface to be polished is silicon dioxide, potassium hydroxide, tetramethylammonium hydroxide, hydrofluoric acid, fluoride, or the like is used. When the surface to be polished is tungsten, iron nitrate, potassium iodate, or the like is used. When the surface to be polished is copper, glycine, quinaldic acid, hydrogen peroxide, benzotriazole, or the like is used.

<Polishing test 1> A polishing pad as shown in FIG. 1 is used in combination with a polishing pad having a predetermined compressibility and a retainer ring, and a polishing test is performed on the surface of the wafer, and the polishing amount of the peripheral portion of the wafer The difference was measured.

  As shown in FIG. 3, the difference in the polishing amount at the peripheral portion of the wafer means the difference between the maximum value and the minimum value of the polishing amount at the peripheral portion of the wafer before and after polishing. The smaller the difference, the flatter the peripheral portion. It can be seen that it is. In the illustrated example, the difference in the polishing amount indicated by reference numeral Δ2 is smaller than the difference in the polishing amount indicated by reference numeral Δ1, so that the peripheral portion of the polishing amount profile indicated by reference numeral 18 is larger than the peripheral portion of the polishing amount profile indicated by reference numeral 17. Is flatter.

  The polishing apparatus, polishing liquid and wafer used in the polishing test were as follows.

  As a polishing apparatus, a commercially available CMP apparatus (product number: MAT-ARW681S, MTI Corporation) was used. The polishing conditions were as shown in Table 2 below.

  As a polishing liquid, a commercially available polishing slurry (product name: SemiSperse 25, Cabot Microelectronics Japan Co., Ltd.) diluted twice with pure water was used.

  As the wafer, a test wafer generally used in the flatness evaluation test was used. This test wafer was a wafer with a P-TEOS film (direct line 200 mm) having a plasma oxide film (thickness: 10,000 mm) having no pattern on the surface. The film thicknesses of the test wafer before and after polishing were compared, and the difference was defined as the polishing amount, and the difference in the polishing amount at the peripheral portion of the wafer (in the range of 90 mm to 97 mm from the center of the wafer) was determined. A commercially available optical interference type film thickness measuring device (product number: Nanospec 9200, Nanometrics Co., Ltd.) was used for the film thickness measurement performed for the measurement of the polishing amount.

<Polishing pad 1> The polishing pad 1 was manufactured as follows. 3,3′-dichloro-4,4 ′ heated to 120 ° C. as a curing agent to a TDI (tolylene diisocyanate) polyurethane prepolymer (100 parts) having an average molecular weight of 900-1000 heated to 70 ° C. A resin solution prepared by adding diamino-diphenylmethane (26.5 minutes) is put into a mold, this is cured in the mold, a resin block is formed, the block is cut into a circular shape, and the thickness is increased. A polishing pad 1 was manufactured by grinding to 1.5 mm and using a lathe to form a spiral groove (pitch 2 mm, depth 0.5 mm, width 1 mm) on the surface. The compression rate of the polishing pad 1 was 0.84%.

<Polishing Pad 2> As the polishing pad 2, a commercially available polishing pad (product name: IC1000, Rohm and Haas Electronic Materials, CMP Holdings, Inc.) generally used for polishing semiconductor device wafers. Incorporated) was used. The compressibility of the polishing pad 2 was 4.2%.

<Retainer ring 1> The retainer ring 1 was manufactured as follows. 3,3′-dichloro-4,4 ′ heated to 120 ° C. as a curing agent to a TDI (tolylene diisocyanate) polyurethane prepolymer (100 parts) having an average molecular weight of 900-1000 heated to 70 ° C. A resin solution prepared by adding diamino-diphenylmethane (26.5 minutes) is put into a mold, cured in the mold, a resin block is formed, and the block is cut into a ring of a predetermined size. Thus, the retainer ring 1 was manufactured. The compression ratio of the retainer ring 1 was 0.84%.

<Retainer ring 2> As the retainer ring 2, a commercially available hard retainer ring having a compression rate of 0.1% was used.

<Combination of Polishing Pad and Retainer Ring> Combinations of the polishing pad and the retainer ring were as shown in Table 3 below. (Here, test D in Table 3 is an example according to the present invention.)

<Test Result 1> The results of the polishing test 1 are shown in Table 4 below and FIG.

  From the results shown in Table 4 and FIG. 4, in a polishing pad having the same compression ratio, in a retainer ring having a higher compression ratio (see tests A and B and tests C and D) or in a retainer ring having the same compression ratio, It can be seen that when polishing pads with lower compression ratios (see tests A and C and tests B and D) are combined, the difference in polishing amount becomes smaller and the peripheral portion of the wafer becomes more flat. Further, it can be seen that when the polishing pad and the retainer ring each having substantially the same compression ratio are combined, the difference in the polishing amount becomes the smallest (Test D).

<Polishing Test 2> The polishing pad 1 and the retainer rings 1 and 2 used in the polishing test 1 were combined, and the polishing pressure and the retainer ring pressure were changed to measure the difference in the polishing amount at the peripheral portion of the wafer.

  The polishing apparatus, polishing liquid, and wafer used in the polishing test 2 were the same as those in the polishing test 1 except that the polishing pressure and the retainer ring pressure were changed under the polishing conditions.

The combinations of the polishing pad and the retainer ring were as shown in Table 5 below. (Here, test F in Table 5 is an example according to the present invention.)

<Test Result 2> The results of the polishing test 2 are shown in Table 6 below.

  Increasing the retainer ring pressure (and increasing the polishing pressure) reduces the risk of the wafer jumping out of the polishing head. However, as shown in Table 6, when the retainer ring pressure (or polishing pressure) is increased, The difference in polishing amount becomes large. However, test F (example) according to the present invention (combining a polishing pad and a retainer ring with substantially the same compression ratio) is a test E (hard one having a lower compression ratio than the retainer ring of test F). The difference in the polishing amount at the peripheral portion of the wafer is remarkably low.

  Therefore, by using a combination of a polishing pad and a retainer ring having substantially the same compression rate, the difference in polishing amount at the peripheral portion of the wafer can be reduced.

FIG. 1 is a partial side view of the polishing apparatus. FIG. 2 is a partial cross-sectional view of the polishing head. FIG. 3 shows the difference in polishing amount at the peripheral portion of the wafer. FIG. 4 is a graph showing the results of the polishing test.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Polishing apparatus 11 ... Platen 12 ... Polishing head 13 ... Nozzle 14 ... Polishing pad 15 ... Wafer 16 ... Retainer ring 16 '... Ring part 17, 18, ..Polishing amount profiles [Delta] 1, [Delta] 2 ... Difference in polishing amount R ... Platen rotation direction r ... Polishing head rotation direction

Claims (9)

A polishing apparatus comprising:
Platen,
Means for rotating the platen;
A polishing pad affixed to the surface of the platen,
A nozzle for supplying a polishing liquid to the surface of the polishing pad; and a polishing head for holding a wafer and pressing the surface of the wafer against the surface of the polishing pad;
Consisting of
The polishing head comprises:
A retainer ring having a ring portion disposed outside the peripheral portion of the wafer, wherein the wafer is held, and when the surface of the wafer is pressed against the surface of the polishing pad, the ring portion of the retainer ring is polished. Retainer ring, pressed against the surface of the pad
Including
The compression ratio of the retainer ring is in the range of 95% or more and 101% or less of the compression ratio of the polishing pad.
However, polishing equipment. The polishing apparatus according to claim 1,
The compressibility of the retainer ring is in the range of 99.4% or more and 100.6% or less of the compressibility of the polishing pad.
However, polishing equipment. The polishing apparatus according to claim 1,
The compression ratio of the retainer ring is in the range of 0.6% or more and 1.2% or less,
However, polishing equipment. The polishing apparatus according to claim 1,
The polishing pad and the retainer ring are each made of the same type of synthetic resin.
However, polishing equipment. The polishing apparatus according to claim 1,
The polishing pad and the retainer ring are each made of a polyurethane resin,
However, polishing equipment. The polishing apparatus according to claim 1,
The polishing pad and the retainer ring are each made of a non-foamed material of the same type of synthetic resin.
However, polishing equipment. The polishing apparatus according to claim 1,
Means for rotating the polishing head;
A polishing apparatus further comprising: A method for polishing a surface of a wafer using the polishing apparatus according to claim 1,
Holding the wafer and pressing the surface of the wafer against the surface of the polishing pad, wherein the ring portion of the retainer ring is pressed against the surface of the polishing pad;
Rotating the platen with the polishing pad affixed to the surface; and supplying the polishing liquid to the surface of the polishing pad through the slip;
A method consisting of: 9. The method of claim 8, wherein
Rotating the polishing head;
A method further comprising:

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