JP2003309093A - Semiconductor wafer polishing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wafer polishing device which can easily collect the slurry of a polishing agent which comes to stay in a polishing pad and discharge to the outside, and is detached from the polishing pad without permitting to deform a wafer after the wafer which becomes large-sized recently is finished polishing. <P>SOLUTION: In the polishing device, a semiconductor wafer 13 is sucked by a vacuum pressure passing a back pad 3 from a conduit line formed inside a polishing head 1, and the slurry 18 as a polishing agent is dropped down from a nozzle 17 on a surface plate 15 to which a polishing pad 16 is adhered and which rotates in one direction. Simultaneously, a semiconductor wafer 13 is pressed along with the polishing head 1. The pipe line formed inside the polishing head 1 is independently formed in two systems, and one system is connected to an air pressure source 6 and the other system is connected to a vacuum pressure source 8, and a trap 10 for collecting the slurry 18 is disposed in the middle of the pipe line connected to the vacuum pressure source 8, and occasionally the slurry 18 can be discharged to the outside. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polishing apparatus for polishing the surface of a semiconductor wafer for flattening irregularities on the surface of a semiconductor wafer used as a semiconductor substrate.

[0002]

2. Description of the Related Art A polishing apparatus used for polishing a semiconductor wafer is a CMP (Chemical Mechanical Pol).
is a device for polishing semiconductor wafers (hereinafter referred to as "wafers") onto a rotating surface plate to which a polishing pad made of a polishing cloth is attached while dropping a processing liquid containing fine particles. is there. Then, the solid surface reaction between the particles contained in the processing liquid and the wafer surface produces a foreign substance at the interface, and the chemical polishing means for removing the foreign substance is used to mirror-finish the wafer surface.

In such a CMP apparatus, it is necessary to collect the slurry, which is the polishing liquid that stays, and to remove the slurry, which has become large in size in recent years, from the polishing pad after the completion of polishing while suppressing the deformation of the wafer. Becomes Therefore, Japanese Patent Laid-Open No. 9-85617 discloses a technique for solving this problem.

FIG. 2 is a schematic diagram of this conventional wafer polishing apparatus. In FIG. 2, 101 is a polishing head, which is rotated by a motor 102. A back pad 103 is fixed to the end surface of the polishing head 101. A pipe line 104 is formed inside the polishing head 101, and is connected to an air source 107 and a vacuum source 108 via open / close valves 105 and 106. The wafer 109 has an opening / closing valve 10
5 is closed and the on-off valve 106 is opened, and adsorption is performed by the vacuum pressure of the vacuum source 108 passing through the back pad 103.

On the other hand, a polishing pad 112 is attached on a surface plate 111 driven by the rotary shaft 110. A nozzle 113 for dropping the polishing liquid is arranged near the center of the rotary shaft 110 on the side of the polishing head 101. The slurry 114, which is a polishing liquid, gradually diffuses in the outer peripheral direction of the surface plate 111 due to centrifugal force.

An air hole 115 is formed inside the surface plate 111 and is connected to an air source 117 via an opening / closing valve 116. The air holes 115 are branched, and one of them is the polishing pad 11
2 reaches the outlet 118, and the other reaches the leak valve 119. After the polishing of the wafer is completed, the on-off valve 105 is closed and the on-off valve 106 is opened to adsorb the wafer 109 by the vacuum pressure from the vacuum source 108, and the polishing head 1 as indicated by arrow A.
When 01 is raised, the wafer 109 is easily deformed toward the polishing pad 112 side by the surface tension of the slurry 114 as shown in the figure. Therefore, by opening the on-off valve 116 and supplying air pressure from the air source 117 to the space 120, this deformation is prevented and the separation of the wafer 109 from the polishing pad 112 is assisted. Further, the slurry 114 can be discharged to the outside of the machine by opening the leak valve 119 as appropriate.

In the configuration of FIG. 2, since the vacuum pressure line for adsorbing the wafer 109 and the air pressure line 104 for forcibly releasing the wafer 109 are shared, a small amount of the slurry 114 remains in the line 104. That causes the back surface of the wafer 109 to be oxidized and causes color unevenness. Also, the wafer 109
When removing the wafer from the polishing pad 112, the space 120
Must be supplied with air pressure and requires extra steps and equipment.

[0008]

SUMMARY OF THE INVENTION According to the present invention, it is possible to easily collect the slurry, which is the polishing liquid accumulated on the polishing pad, and discharge it to the outside of the machine. Provided is a wafer polishing apparatus for removing a wafer from a polishing pad without allowing the deformation of the wafer.

[0009]

A semiconductor wafer is adsorbed by a vacuum pressure passing through a back surface pad from a conduit formed inside a polishing head, and a polishing plate is attached to a surface plate that rotates in one direction. In a polishing apparatus that presses a semiconductor wafer together with a polishing head while dropping a slurry as a polishing liquid from the polishing head, two channels are formed independently inside the polishing head, one is an air pressure source and the other is a vacuum pressure source. A trap for collecting the slurry is disposed in the middle of a pipe line connected to the vacuum pressure source so that the slurry can be appropriately discharged to the outside of the machine.

Of the conduits formed inside the polishing head,
By forming the other pipeline connected to the vacuum pressure source closer to the outer peripheral surface side of the polishing head than the one pipeline connected to the air pressure source, while suppressing the deformation of the wafer after the polishing of the wafer is completed. It can be detached from the polishing pad.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of a semiconductor wafer polishing apparatus according to the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a conceptual diagram of the structure of a polishing apparatus. In FIG. 1, reference numeral 1 is a polishing head, which is rotated by a motor 2. The back surface pad 3 is provided at the lower end of the polishing head 1.
Is fixed. In between the motor 2 and the polishing head 1, a rotary joint 4 connected to two independent pipelines of air pressure and vacuum pressure is arranged.

An opening / closing valve 5 is attached to the rotary joint 4.
One pipeline 7 that supplies air pressure from the air source 6 via a and 5b is connected to the other pipelines 9a and 9b that are connected to the vacuum source 8. Rotary joint 4 to open / close valve 5
A trap 10 for collecting the slurry 18 is arranged in the middle of the other pipeline reaching b. Among the other pipelines, the pipeline 9a is temporarily stored in the space 10a of the trap 10 for the slurry 1
8 is discharged, and the tip of the separately provided conduit 9b is exposed to the void 10a, so that the slurry 18 does not flow into the opening / closing valve 5b side. Then, by appropriately operating the on-off valve 11, the slurry 18 accumulated below the discharge tank 12 is discharged.

One of the conduits 7 for supplying air pressure, which is connected to the rotary joint 4, communicates with an air hole 3a passing through the back surface pad 3 through the center of the inside of the polishing head 1. The other pipeline 9a for supplying a vacuum pressure is disposed near the outer circumference inside the polishing head 1 via the ring groove 4a, communicates with the vacuum hole 3b passing through the back surface pad 3, and sucks the wafer 13. Become. A guide ring 3c is formed on the outer periphery of the back surface pad 3, and the wafer 13 being polished
To prevent the slurry 18 from entering the back surface pad 3 and the non-polished surface of the wafer 13.

On the other hand, a polishing pad 16 made of a polishing cloth is attached on a surface plate 15 driven by the rotary shaft 14. A nozzle 17 for dropping a polishing liquid is arranged near the center of the rotary shaft 14 on the side of the polishing head 1. The slurry 18 as the polishing liquid gradually diffuses in the outer peripheral direction of the surface plate 15 due to the centrifugal force.

Next, the procedure for polishing the wafer 13 in the polishing apparatus configured as shown in FIG. 1 will be described. First,
In the standby position of the polishing head 1, the discharge tank 1
With the on-off valve 11 of the trap 10 connected to No. 2 closed, the on-off valve 5b communicating with the vacuum source 8 opens, and the vacuum hole arranged near the outer circumference of the back surface pad 3 from the other pipeline 9a, 9b. Guide ring 3c of the backside pad 3 via 3b
The wafer 13 is attracted to the inside of the. In the prior art in FIG. 2, since the vacuum pressure and the air pressure supply pipeline 104 are shared, a small amount of slurry remains in the pipeline 104,
Although the back surface of the wafer was oxidized and the color unevenness was caused, by forming the one pipeline 7 and the other pipelines 9a and 9b independently as shown in FIG. Even if the slurry 18 is sucked, the air pressure for separating the wafer 13 does not cause the slurry 18 to flow back and contaminate the non-polished surface of the wafer 13.

In particular, when the material of the wafer 13 is gallium arsenide type, it is more sensitive to contamination by the slurry 18 than silicon type. The guide ring 3c formed on the outer periphery of the back surface pad 3 has a function of preventing the wafer 13 from jumping out during polishing and preventing the slurry 18 from entering the non-polished surfaces of the back surface pad 3 and the wafer 13.

After the suction of the wafer 13 is completed, the polishing head 1 is moved to above the rotating surface plate 15 by a separate means. Next, the slurry 1 is sprayed from the nozzle 17 onto the upper surface of the polishing pad 16.
8 is dropped, the polishing head 1 is rotated by the motor 2, the wafer 13 is lowered as indicated by arrow C, and mirror polishing is performed by chemical polishing under a predetermined surface pressure. During the polishing process, the on-off valve 5b communicating with the vacuum source 8 is closed in order to prevent the non-uniform suction force from acting on the wafer 13. The wafer 13 is gripped by the guide ring 3c formed on the outer periphery of the back surface pad 3.

After the polishing of the wafer 13 is completed, the vacuum source 8 is again provided.
The opening / closing valve 5b leading to the valve is opened to adsorb the wafer 13, and the polishing head 1 is raised as indicated by arrow B to stop the rotation of the polishing head 1. In the present invention, since the vacuum holes 3a passing through the back surface pad 3 are arranged near the outer periphery of the polishing head 1 in the present invention, even if the wafer is thin and has a large diameter and is easily deformed, the surface of the slurry described in the prior art is described. The air source 117 that prevents the deformation of the wafer due to the tension is unnecessary.

After that, the polishing head 1 is separately moved to the initial standby position to close the open / close valve 5b communicating with the vacuum source 8 and the open / close valve 5a communicating with the air source 6. The air pressure is supplied from the conduit 7 to the central portion of the wafer 13 to store the wafer 13 at a predetermined position. Then, the opening / closing valve 11 is appropriately opened to collect the slurry 18 accumulated below the trap 10 in the discharge tank 12.

[0020]

According to the present invention, the pipeline formed inside the polishing head, which is involved in the attachment and detachment of the wafer, is independent of the two systems of the vacuum pressure pipeline for adsorbing the wafer and the pneumatic circuit for opening the wafer. A trap for collecting the slurry is arranged in the middle of the vacuum pressure pipe for adsorbing, and the slurry can be appropriately discharged to the outside of the machine, so that the non-polishing surface of the wafer is not contaminated by the slurry when the wafer is attached and detached. It is possible to prevent oxidation and uneven color generation.

Further, among the pipe lines formed inside the polishing head, the pipe line connected to the vacuum pressure source is formed closer to the outer peripheral surface side of the polishing head than the pipe line connected to the air pressure source.
After the polishing of the wafer is completed, the wafer can be detached from the polishing pad while suppressing the deformation of the wafer.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing the configuration of a polishing apparatus of the present invention.

FIG. 2 is a schematic diagram of a conventional polishing apparatus.

[Explanation of symbols]

1 polishing head 2 motor 3 Back pad 4 rotary joint 5a, 5b open / close valve 6 Air source 7 One pipeline 8 vacuum source 9a, 9b The other conduit 10 traps 11 on-off valve 13 wafers 14 rotation axis 15 surface plate 16 polishing head 17 nozzles 18 slurry

Claims (2)

[Claims] 1. A semiconductor wafer is adsorbed by a vacuum pressure passing through a backside pad from a conduit formed inside a polishing head, and a polishing plate is attached to a surface plate that rotates in one direction. In a polishing apparatus that presses the semiconductor wafer together with the polishing head while dropping a certain slurry, the pipe lines formed inside the polishing head are separated into two systems, one as an air pressure source and the other as a vacuum pressure source. A semiconductor wafer polishing apparatus, characterized in that a trap for collecting the slurry is arranged in the middle of a pipe line connected to and connected to the vacuum pressure source so that the slurry can be appropriately discharged to the outside of the machine. 2. The outer peripheral surface of the polishing head, of the conduits formed inside the polishing head, the other conduit connected to the vacuum pressure source is more than the one conduit connected to the air pressure source. The semiconductor wafer polishing apparatus according to claim 1, which is formed on the side.