JP2002018705A - Method of double-face simultaneous polishing for semiconductor wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of double-face simultaneous polishing for a semiconductor wafer, considerably shortening working time for polishing the semiconductor wafer and remarkably improving the quality, yield and productivity of the semiconductor wafer polished into a mirror finished surface obtained by the polishing. SOLUTION: In this method for double-face simultaneous polishing of the semiconductor wafer, the semiconductor wafer is set between an upper surface table and a lower surface table of a mirror finished surface polishing device provided with the upper surface table with abrasive cloth bonded to the lower face side, and the lower surface table with abrasive cloth bonded to the upper face side, and the upper surface table and the lower surface table are rotated reversely to each other while supplying the semiconductor wafer with a polishing solution containing abrasive grains, to simultaneously polish both faces of the semiconductor wafer. Double-face simultaneous polishing is performed being divided in the former half double-face simultaneous polishing performed with a polishing solution containing abrasive grains large in grain diameter and the latter half double-face simultaneous polishing performed with a polishing solution containing abrasive grains small in grain diameter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for simultaneously polishing both surfaces of a semiconductor wafer.

[0002]

2. Description of the Related Art A semiconductor device is obtained by applying a fine circuit pattern to a surface of a base semiconductor wafer.

The degree of integration of this semiconductor device is increasing year by year, and its circuit wiring is also becoming thinner.

In order to apply a highly miniaturized circuit pattern to the surface of a semiconductor wafer, the surface must have a high degree of flatness and a high degree of mirror surface.

[0005] A two-stage polishing method has been used as a polishing method for increasing the flatness of a semiconductor wafer and making it a mirror surface. The two-stage polishing method is a polishing method performed in two stages of a primary polishing and a secondary polishing.

That is, in the first polishing, the semiconductor wafer is subjected to mechanochemical polishing in order to obtain a high degree of flatness.
In the second polishing, chemical polishing is performed to make the surface of the semiconductor wafer a high quality mirror surface.

(Primary polishing) First, the primary polishing will be described.

In the first polishing, both surfaces of the semiconductor wafer are simultaneously subjected to mechanochemical polishing in order to increase the flatness of the semiconductor wafer.

FIG. 1 is a partial schematic cross-sectional explanatory view showing a state in which a semiconductor wafer is mounted on a mirror polishing apparatus and both surfaces thereof are simultaneously subjected to mechanochemical polishing.

In FIG. 1, 1 is an upper surface plate, 2 is a lower surface plate, and 3 is an upper surface plate.
Is a polishing cloth, 4 is a carrier, 5 is a semiconductor wafer to be polished, 6 is a sun gear, 7 is an internal gear, and 8 is a polishing liquid supply hole.

As can be seen from FIG. 1, the mirror polishing apparatus has an upper surface plate 1 on the upper side and a lower surface plate 2 on the lower side. A polishing cloth 3 is bonded to the lower surface of the upper platen 1, and the polishing cloth 3 is bonded to an upper surface of the lower platen 2. A carrier 4 and a semiconductor wafer 5 to be polished are held between the polishing cloth 3 bonded to the lower surface of the upper platen 1 and the polishing cloth 3 bonded to the upper surface of the lower platen 2. . The upper platen 1 and the lower platen 2 rotate in directions opposite to each other by a driving mechanism (not shown).
Is configured to revolve on its own (planetary motion) due to the difference in the number of revolutions between the sun gear 6 and the internal gear 7. A polishing liquid is supplied to the semiconductor wafer 5 from a polishing liquid supply hole 8 passing through the upper platen 1.

In the first polishing, a hard non-woven cloth polishing cloth is used as a polishing cloth in order to increase the high flatness of the semiconductor wafer 5, and a chemical polishing liquid containing abrasive grains is used as a polishing liquid, thereby performing mechanochemical polishing. It has become.

(Secondary Polishing) Next, the secondary polishing will be described.

The semiconductor wafer 5, both surfaces of which are mechanochemically polished by the primary polishing, is subjected to a secondary polishing for making a high-quality mirror surface on one side on which a circuit pattern is applied.

In this secondary polishing, first, a semiconductor wafer 5 whose both surfaces are mechanochemically polished by the primary polishing is adhered to a polishing plate (not shown), and then a single-side polishing is performed.

In the second polishing, a polishing cloth made of a soft nonwoven fabric having a foamed layer is used as a polishing cloth in order to make one side of the semiconductor wafer 5 a high quality mirror surface, and a chemical polishing liquid containing no abrasive grains is used as a polishing liquid. , So that they are chemically polished.

The polishing operation cost of this type is largely affected by the removal speed of the semiconductor wafer 5, the polishing operation time, the amount of polishing liquid used, and the like. That is, the polishing operation cost can be reduced as the removal speed of the semiconductor wafer 5 is increased, the polishing operation time is shorter, and the amount of the polishing liquid used is smaller.

In order to increase the removal speed of the semiconductor wafer 5 in the primary polishing and to shorten the polishing operation time, it is effective to enhance the mechanical polishing property. Here, in order to enhance the mechanical polishing property of the primary polish, it is effective to make the abrasive grains contained in the polishing liquid large abrasive grains.

[0019]

However, when the semiconductor wafer 5 is primarily polished using a polishing liquid containing large-diameter abrasive grains, the removal speed of the semiconductor wafer is increased as intended, and the polishing operation time is greatly reduced. However, the semiconductor wafer 5 has a large number of scratch defects and a potential damage factor is accumulated in the semiconductor wafer 5,
As a result, there is a problem that the quality, yield and productivity of the mirror-polished semiconductor wafer are reduced.

The present invention has been made in view of such a point, and an object of the present invention is to solve the above-mentioned disadvantages of the prior art and to greatly reduce the polishing time of the semiconductor wafer. Moreover, it is an object of the present invention to provide a method for simultaneously polishing both surfaces of a semiconductor wafer, which can significantly improve the quality, yield and productivity of a mirror-polished semiconductor wafer obtained by the polishing.

[0021]

SUMMARY OF THE INVENTION The gist of the present invention is to provide a mirror polishing machine comprising an upper surface plate having a polishing cloth adhered to a lower surface and a lower surface plate having a polishing cloth adhered to an upper surface. A semiconductor wafer is set between the upper stool and the lower stool of the apparatus, and the upper stool and the lower stool are rotated in opposite directions while supplying a polishing liquid containing abrasive grains to the semiconductor wafer. In the method for simultaneously polishing both surfaces of the semiconductor wafer by simultaneously polishing both surfaces of the semiconductor wafer, the first half simultaneous double polishing in which the double-side simultaneous polishing is performed with a polishing liquid containing abrasive grains having a large particle diameter,
The present invention provides a method for simultaneously polishing both surfaces of a semiconductor wafer, wherein the polishing is performed separately from the latter half simultaneous polishing performed with a polishing liquid containing abrasive grains having a small particle diameter.

In the present invention, the particle size of the abrasive grains contained in the polishing liquid used for the first half simultaneous polishing is a (μm), and the particle diameter of the abrasive grains contained in the polishing liquid used for the second half simultaneous polishing is b (μm). In this case, it is preferable that the abrasive particles contained in the polishing liquid used for the first-half double-sided simultaneous polishing be abrasive particles having a particle diameter satisfying 3b ≦ a ≦ 6b (1).

This is because the polishing time cannot be remarkably shortened when 3b ≦ a, and on the other hand, when a ≦ 6b, scratch failures occur rapidly and frequently.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of a method for simultaneously polishing both surfaces of a semiconductor wafer according to the present invention will be described with reference to the drawings.

The polishing apparatus, materials and polishing conditions used in one embodiment of the method for simultaneously polishing both surfaces of a semiconductor wafer according to the present invention are as follows.

A. Mirror surface polishing device ... 16B type mirror surface polishing device (carrier diameter φ40 mm) b. Semiconductor wafer: GaAs wafer having an outer diameter of 4 inches c. Wafer removal amount: 50 μm d. Abrasive grains of polishing liquid: abrasive grains used in comparative example: 0.02
Abrasive particles of μm Abrasive particles used in Examples; Abrasive particles of 0.10 μm (5 times as large as abrasive particles of Comparative Example) (Comparative Example 1) First, 40 GaAs wafers were set in a 16B type mirror polishing machine.

Next, using a chemical polishing solution containing abrasive grains having a particle size of 0.02 μm and a polishing cloth made of hard non-woven fabric, the amount of both-side removal of 40 GaAs wafers set in a 16B mirror polishing machine was measured. 50 μm was first polished.

The removal rate was 0.5 μm / min.

The polishing time was 100 minutes.

Next, in order to obtain a high-quality mirror surface on one side of the double-side polished semiconductor wafer 5, a polishing cloth made of a soft non-woven fabric having a foamed layer is used as a polishing cloth, and a polishing liquid containing no abrasive grains is used. The solution was used for secondary polishing (chemical polishing).

Next, degreasing treatment, washing treatment, ultrapure water washing,
By performing a drying treatment, a mirror-polished GaAs wafer of Comparative Example 1 was obtained.

(Comparative Example 2) First, 40 GaAs wafers were set in a 16B type mirror polishing apparatus.

Next, using a chemical polishing solution containing abrasive grains having a particle diameter of φ0.10 μm and a polishing cloth made of hard non-woven fabric, the amount of removal of both sides of 40 GaAs wafers set in a 16B mirror polishing machine was measured. 50 μm was first polished.

The removal rate was 0.5 μm / min.

The polishing time was 100 minutes.

Next, a polishing cloth made of a soft non-woven fabric having a foamed layer is used as a polishing cloth in order to make one side of the semiconductor wafer 5 which has been polished on both sides a high quality mirror surface, and a chemical polishing which does not contain abrasive grains is used as a polishing liquid. The solution was used for secondary polishing (chemical polishing).

Next, degreasing treatment, washing treatment, ultrapure water washing,
By performing the drying treatment, a mirror-polished GaAs wafer of Comparative Example 2 was obtained.

(Example 1) First, 40 GaAs wafers were set in a 16B type mirror polishing apparatus.

Next, using a chemical polishing solution containing abrasive grains having a particle diameter of 0.10 μm and a polishing cloth made of hard nonwoven fabric, GaAs
The both sides of the wafer were polished on both sides for the first half removal amount of 25 μm.

The removal rate at this time was 1.0 μm / min.

Next, using a chemical polishing liquid containing abrasive grains having a particle diameter of 0.02 μm and a hard nonwoven polishing cloth,
A 25 μm portion of the aAs wafer, which was removed in the latter half on both sides, was subjected to primary polishing.

The removal rate is 0.5 μm / min.

The total polish time of the first half polish and the second half polish was 75 minutes. This total polishing time of 75 minutes was reduced by 25 minutes from the polishing time of Comparative Example 1.

Next, in order to make one side of the semiconductor wafer 5 which has been polished on both sides a high quality mirror surface, a polishing cloth made of a soft non-woven fabric having a foam layer is used as a polishing cloth, and a chemical polishing containing no abrasive grains is used as a polishing liquid. The solution was used for secondary polishing (chemical polishing).

Next, degreasing treatment, washing treatment, ultrapure water washing,
By performing a drying treatment, a mirror-polished GaAs wafer of Example 1 was obtained.

(Test Method and Test Results) Next, forty semiconductor mirror-polished GaAs wafers obtained by the double-sided simultaneous polishing method of the semiconductor wafer of Comparative Example 1 thus obtained,
Example 1 40 mirror-polished GaAs wafers obtained by the double-sided simultaneous polishing method for the semiconductor wafer of Comparative Example 2
For 40 mirror-polished GaAs wafers obtained by the double-sided simultaneous polishing method for the semiconductor wafers, the polishing time was measured and the presence / absence of scratches was measured with a 100,000 lux collector.

No scratch defect was found on 40 mirror-polished GaAs wafers obtained by the double-sided simultaneous polishing method of the semiconductor wafer of Comparative Example 1, but the half-side polishing time required 100 minutes.

Out of 40 mirror-polished GaAs wafers obtained by the double-sided simultaneous polishing method of the semiconductor wafer of Comparative Example 2, 10 of the polished GaAs wafers had defective scratches (defective rate: 25%). Moreover, the polishing time took 100 minutes.

On the other hand, the mirror polishing G obtained by the double-sided simultaneous polishing method for the semiconductor wafer according to the first embodiment of the present invention.
No scratch defects were found on 40 aAs wafers, and the polishing time was as short as 75 minutes.

[0050]

According to the method for simultaneously polishing both surfaces of a semiconductor wafer of the present invention, the polishing time can be remarkably reduced, and the quality, yield and productivity of the mirror-polished semiconductor wafer finally obtained can be remarkably improved. And is industrially useful.

[Brief description of the drawings]

FIG. 1 is a partial schematic cross-sectional explanatory view showing a state where a semiconductor wafer is mounted on a mirror polishing apparatus and both surfaces thereof are simultaneously subjected to mechanochemical polishing.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Upper surface plate 2 Lower surface plate 3 Polishing cloth 4 Carrier 5 Semiconductor wafer to be polished 6 Sun gear 7 Internal gear 8 Polishing liquid supply hole

Claims (2)

[Claims] 1. A mirror polishing apparatus comprising: an upper surface plate having a polishing cloth adhered to a lower surface thereof; and a lower surface plate having a polishing cloth adhered to an upper surface thereof. A semiconductor wafer for simultaneously polishing both surfaces of the semiconductor wafer by rotating the upper platen and the lower platen in opposite directions while setting a semiconductor wafer on the semiconductor wafer and supplying a polishing liquid containing abrasive grains to the semiconductor wafer. In the double-sided simultaneous polishing method, the two-sided simultaneous polishing in which the two-sided simultaneous polishing is performed with a polishing liquid containing abrasive grains having a large particle diameter, and the second-half simultaneous polishing in which the two-sided simultaneous polishing is performed with a polishing liquid containing abrasive particles having a small particle diameter A method for simultaneously polishing both surfaces of a semiconductor wafer, which is performed separately. 2. The particle size of the abrasive grains contained in the polishing liquid used for the first half simultaneous polishing is a (μm), and the particle size of the abrasive grains contained in the polishing liquid used for the second half simultaneous polishing is b (μm).
Wherein the abrasive grains contained in the polishing liquid used for the first half simultaneous polishing are abrasive grains having a particle diameter satisfying 3b ≦ a ≦ 6b (1 formula). 1
A method for simultaneously polishing both surfaces of a semiconductor wafer as described in the above.