JP2002299297A - Single-wafer polishing method for semiconductor wafer and apparatus therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a single-wafer polishing method for a semiconductor wafer and an apparatus therefore capable of enhancing the planarity of a semiconductor wafer. SOLUTION: When a silicon wafer W is polished on a single wafer basis, the distribution, between the load of an entire head applied to a carrier plate 16 by an air cylinder 22, and the load inside the head and the load outside the head applied to the center of the carrier plate 16 by a protruded rod 18a of the air cylinder 18, is controlled so that the load balance in the entire carrier plate 16 becomes uniform. In this way, a polishing amount is almost uniform over the entire of the silicon wafer W. As a result, the deformation of the silicon wafer W is controlled, and the planarity indicated by TTV on the surface of the wafer can be enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for single wafer polishing of a semiconductor wafer, and more particularly to a method and an apparatus for single wafer polishing of a semiconductor wafer for improving the flatness of a semiconductor wafer.

[0002]

2. Description of the Related Art An etched silicon wafer is subjected to mechanical and chemical polishing in the next polishing step. Here, a polishing apparatus is used to finish the surface of the wafer into a smooth and non-distorted mirror surface. 2. Description of the Related Art Conventionally, as one type of polishing apparatus, a single wafer type wafer polishing apparatus for polishing a surface of a silicon wafer one by one has been known. Hereinafter, this conventional single-wafer polishing apparatus will be described with reference to FIG. FIG. 3 is an enlarged sectional view of a main part showing a use state of a semiconductor wafer single wafer polishing apparatus according to a conventional means. The single wafer polishing apparatus 100 includes a polishing platen 102 on which a polishing cloth 101 is spread on an upper surface, and a polishing platen 1
The polishing head 103 includes a polishing head 103 opposed to the upper side of the polishing pad 02 and a disc-shaped carrier plate 104 which is detachably attached to the polishing head 103 and has a lower surface on which one silicon wafer W is adhered. At the time of single wafer polishing of the silicon wafer W, the polishing cloth 101 and the silicon wafer W are mixed with each other while supplying an abrasive (slurry) containing abrasive grains such as colloidal silica (silica sol) onto the polishing cloth 101 via the nozzle 105. A predetermined load and a relative speed are applied during the polishing of one silicon wafer W.

[0003]

The conventional single wafer polishing apparatus 100 for silicon wafers has the following drawbacks. That is, during single wafer polishing, a polishing load was applied from the polishing head 103 to the entire carrier plate 104 by air pressure. For this reason, at the time of this polishing, a portion of the carrier plate 104 was likely to be protruded and deformed toward the polishing platen 102 due to the concentration of load.
As a result, the silicon wafer W attached to the carrier plate 104 has, for example, a deformation in which the center of the plate is thinner and the outer peripheral side of the plate is thicker, that is, the so-called whole wafer has a concave cross-section, and conversely, the outer peripheral portion is thinner, A shape in which the central portion is thick, that is, the so-called whole wafer has a convex cross section has been generated. As a result, there is a problem that the flatness of the wafer such as TTV and SBIR is reduced.

Therefore, as a result of intensive research, the inventor has adjusted the external load acting on the outer peripheral portion of the carrier plate and the internal load acting on the central portion of the carrier plate to make the load uniform over the entire carrier plate. Then, the inventors have found that such wafer deformation during single wafer polishing is suppressed and the flatness of the wafer is increased, and the present invention has been completed.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method and an apparatus for polishing a single wafer of a semiconductor wafer capable of improving the flatness of the wafer.

[0006]

According to a first aspect of the present invention, a carrier plate attached to a polishing head is polished while a polishing agent is supplied to a polishing pad spread on a polishing platen. In a single wafer polishing method for polishing a semiconductor wafer by pressing a single semiconductor wafer detachably attached to a surface facing a surface plate, an external load of a polishing head acting on an outer peripheral portion of the carrier plate, This is a single wafer polishing method for a semiconductor wafer for polishing by controlling the load in the head acting on the center of the carrier plate.

As a single wafer polishing apparatus used in the single wafer polishing method for a semiconductor wafer, for example, a type in which one semiconductor wafer is attached to a carrier plate with wax may be used, or the semiconductor wafer may be bonded via a back pad. It may be of a type that is attached to a carrier plate by the surface tension of water. Examples of the semiconductor wafer include a silicon wafer and a gallium arsenide wafer. As a polishing cloth, for example, a nonwoven fabric pad, a hard urethane pad,
CeO ₂ pad and the like.

As abrasives, for example, calcined silica, colloidal silica (abrasive grains), amine (processing accelerator)
And a mixture of an organic polymer (haze suppressant) and the like. Colloidal silica is a transparent or opaque milky white colloid liquid in which fine silica particles are dispersed as primary particles in water. The external load and the internal load acting on the carrier plate need to be controlled so that the load becomes uniform over the entire carrier plate.

According to a second aspect of the present invention, there is provided a polishing platen on which a polishing pad is spread, a polishing head disposed opposite to the polishing platen, and a semiconductor wafer attached to the polishing head. A carrier plate to be attached to the polishing pad, while supplying an abrasive to the polishing cloth, a load from the polishing head, by pressing the semiconductor wafer against the polishing cloth to polish the semiconductor wafer, in the single wafer polishing apparatus, the carrier 1 is a semiconductor wafer single wafer polishing apparatus provided with a load control means for controlling an external load of a polishing head acting on an outer peripheral portion of a plate and an internal load acting on a central portion of the carrier plate.

According to a third aspect of the present invention, in the load control means, a rod is provided at a center portion of the carrier plate, and the loading and unloading of the rod allows distribution of the load inside the head and the load outside the head of the semiconductor wafer. 3. The single wafer polishing apparatus for semiconductor wafers according to claim 2, wherein the apparatus is an air cylinder for controlling the pressure. The rod may or may not be fixed to the center of the carrier plate.

[0011]

According to the present invention, during the single wafer polishing of a semiconductor wafer, the external load acting on the outer peripheral portion of the carrier plate and the internal load acting on the central portion of the carrier plate are reduced by the load applied to the entire carrier plate. Is controlled to be uniform. In claim 2, such control is performed by the load control means. As a result, the polishing amount becomes substantially equal over the entire area of the semiconductor wafer. As a result, the deformation of the semiconductor wafer is suppressed, and the flatness of the wafer such as TTV is increased.

In particular, according to the third aspect of the invention, the control of the external load on the head and the internal load on the head acting on the carrier plate is performed by moving the rod of the air cylinder in and out. As described above, since the air cylinder is employed as the load control means, the cost of the semiconductor wafer single wafer polishing apparatus can be reduced, and the control operation thereof is simple.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is an enlarged sectional view of a main part showing a use state of a semiconductor wafer single wafer polishing apparatus according to one embodiment of the present invention. FIGS. 2A to 2C are enlarged cross-sectional views of a semiconductor wafer after single-wafer polishing by a single-wafer polishing apparatus for a semiconductor wafer according to one embodiment of the present invention. In FIG. 1, reference numeral 10 denotes a single wafer polishing apparatus for a semiconductor wafer (hereinafter, referred to as a polishing apparatus)
The polishing apparatus 10 includes a polishing platen 12 having a polishing pad 11 made of a hard urethane pad spread on a surface thereof.
And a polishing head 13 disposed above the polishing head. The polishing head 13 has a disk-shaped head main body 14. On the lower surface of the outer peripheral portion of the head main body 14, a thick annular flange 14a is integrally formed. On the lower end surface of the annular flange 14a, a ring groove 14b having a rectangular cross section is formed in a single annular shape. An O-ring 15 is fitted in the ring groove 14b. A ceramic carrier plate 16 is detachably supported by the head body 14 via the O-ring 15.

As shown in FIG. 1, the carrier plate 16
A single silicon wafer W is stuck on the back surface (lower surface) of the substrate with wax. On the other hand, a disc-shaped pressure plate 17 is detachably fixed to the upper surface of the central portion of the plate 16 via a pyramid-shaped silicone rubber (not shown). An air cylinder (load control means) 18 for controlling the distribution of the load inside the head and the load outside the head of the silicon wafer W is mounted on the central portion of the head main body 14. The pressure plate 17 is fixed to the lower end of the rod 18a. When the rod 18a is projected, the pressing plate 17
Moves downward, and the entire central portion of the carrier plate 16 is pushed downward. On the other hand, the entire outer peripheral portion of the carrier plate is lifted upward. Therefore, the silicon wafer W stuck on the carrier plate 16 is pressed against the polishing pad 11 of the polishing platen 12 by the pressing force from the load in the head. An air cylinder 2 for controlling the overall head load, which controls the overall head load of the polishing head 13, is provided on a central portion of the head body 14 via a connection block 19.
Two rods 21 are connected. The connection block 19 has a thick disk shape, and has a central portion on the lower surface thereof depressed to form a storage space for the air cylinder 18. By changing the protruding length of the rod 21 of the air cylinder (load control means) 22, the overall head load of the polishing head 13 can be arbitrarily controlled.

At the time of single wafer polishing of the silicon wafer W, O
Through the ring 15, the pressing force of the rod 21 of the air cylinder 22 is applied to the carrier plate 1 from the annular flange 14a.
6 acts on the outer periphery. At this time, when a large external load is applied to the outer peripheral portion of the carrier plate 16, only the outer peripheral portion of the plate 16 is pushed and bent toward the polishing platen 12. As a result, the carrier plate 16 is warped and deformed, but this is reduced by the load in the head on the center of the carrier plate 16 by the air cylinder 18. In other words, while maintaining the balance between the external load and the internal load, the silicon wafer W
Is polished. Specifically, the polishing cloth 11 and the silicon wafer W are supplied onto the polishing cloth 11 on the polishing platen 12 through the nozzle 20 while supplying an abrasive containing abrasive grains such as calcined silica or colloidal silica. This is performed by applying a predetermined load and a relative speed between the two.

Suppose a single wafer polished silicon wafer W
Is deformed such that the central portion of the plate is thinner and the outer peripheral portion of the plate is thicker, that is, the so-called entire wafer has a concave cross section (FIG. 2A).
6 is applied to the carrier plate 1
6 is larger than the external load acting on the head. Therefore, the rod 18a of the air cylinder 18 is slightly retracted, and control is performed so that the load becomes uniform over the entire carrier plate 16. Conversely, when the shape of the silicon wafer W is deformed so that the center of the plate is thicker and the outer periphery of the plate is thinner, that is, the so-called whole wafer has a convex cross section (FIG. 2B), Plate 1
The load inside the head of No. 6 is smaller than the load outside the head of the carrier plate 16. Therefore, the rod 18a of the air cylinder 18 is slightly protruded to control the entire load of the carrier plate 16 to be balanced.
That is, the overall load W of the polishing head 13, the external load Wo, and the internal load Wi are defined as Wo = AW and Wi = BW.
Then, W = AW + BW. Therefore, A + B =
The air cylinder 18 controls the distribution of the load inside the head and the load outside the head while adjusting the ratio of A and B that satisfies this equation. By performing such control, an increase or decrease in the amount of partial polishing of the silicon wafer W can be suppressed. As a result, the deformation of the silicon wafer W is suppressed, and the flatness of the wafer such as TTV and SBIR can be increased (FIG. 2C). Also, in this embodiment,
Since the air cylinder 18 is employed as the load control means for controlling the load outside the head and the load inside the head of the carrier plate 16, the load control means and, consequently, the single wafer polishing apparatus 10 are used.
Cost can be reduced.

[0017]

According to the present invention, the external load applied to the carrier plate and the internal load applied to the carrier plate are controlled when the semiconductor wafer is polished, and the load is made uniform over the entire carrier plate. Is suppressed, and wafer flatness such as TTV and SBIR can be increased.

In particular, according to the third aspect of the present invention, an air cylinder is employed as a load control means for controlling the distribution of the load inside the head and the load outside the head of the carrier plate. Cost can be reduced.

[Brief description of the drawings]

FIG. 1 is an enlarged sectional view of a main part showing a use state of a semiconductor wafer single wafer polishing apparatus according to one embodiment of the present invention.

FIGS. 2A to 2C are enlarged cross-sectional views of a semiconductor wafer after single-wafer polishing by a single-wafer polishing apparatus according to one embodiment of the present invention;

FIG. 3 is an enlarged sectional view of a main part showing a use state of a semiconductor wafer single wafer polishing apparatus according to a conventional means.

[Explanation of symbols]

 Reference Signs List 10 single wafer polishing apparatus for semiconductor wafer, 11 polishing cloth, 12 polishing platen, 13 polishing head, 16 carrier plate, 18 air cylinder (load control means), 18a rod, 22 air cylinder, W silicon wafer (semiconductor wafer).

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Katsumi Kiriyama 1-5-1, Otemachi, Chiyoda-ku, Tokyo F-term in Mitsubishi Materials Silicon Co., Ltd. 3C058 AA07 AA12 CA01 CB02 DA12 DA17

Claims (3)

[Claims] 1. A polishing pad, which is provided on a polishing plate spread on a polishing plate while being supplied with an abrasive to the polishing pad, is removably attached to a surface of a carrier plate attached to a polishing head, which is opposed to the polishing plate. In a single wafer polishing method for polishing a semiconductor wafer by pressing a single semiconductor wafer, an external load of a polishing head acting on an outer peripheral portion of the carrier plate, and an internal load acting on a central portion of the carrier plate, Wafer polishing method for polishing a semiconductor wafer by controlling polishing. 2. A polishing platen on which a polishing cloth is spread, a polishing head arranged opposite to the polishing platen, and a carrier plate attached to the polishing head and having one semiconductor wafer adhered thereto. In a single wafer polishing apparatus for polishing a semiconductor wafer by pressing the semiconductor wafer against a polishing cloth by a load from the polishing head while supplying an abrasive to the polishing cloth, the semiconductor wafer acts on an outer peripheral portion of the carrier plate. A single wafer polishing apparatus provided with a load control means for controlling a load outside the head of a polishing head and a load inside the head acting on a center portion of the carrier plate. 3. The load control means is an air cylinder in which a rod is provided at the center of the carrier plate, and the distribution of the load inside the head and the load outside the head of the semiconductor wafer is controlled by inserting and removing the rod. Claim 2
2. The single wafer polishing apparatus for a semiconductor wafer according to claim 1.