JP2003218066A - Polishing method for semiconductor wafer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polishing method for semiconductor wafers for maintaining the cleanliness of wafers, without causing marks due to polishing abrasive on the surface of the wafers. <P>SOLUTION: In the polishing method for semiconductor wafers, a polishing roller 14 where polishing cloth is extended on the surface to made to face a chamfer surface 10 of a semiconductor wafer 10, and the polishing roller is rotated, while an abrasive 13 is being supplied, to come into contact with the chamfer surface of the wafer, thus allowing the chamfered surface to be subjected to mirror-surface polishing. Such a characteristic configuration can be achieved by setting the abrasive to be an etching liquid. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for polishing a semiconductor wafer in which chuck marks are prevented from being formed in a chamfering mirror polishing (PCR) process.

[0002]

2. Description of the Related Art Generally, a semiconductor silicon wafer is manufactured by chamfering, mechanical polishing (lapping), etching, PCR, mirror polishing (polishing) and cleaning of a wafer obtained by slicing a pulled silicon single crystal ingot. And is manufactured as a wafer having a highly accurate flatness. Depending on the purpose, some of these steps are replaced with each other, repeated a plurality of times, or other steps such as heat treatment and grinding are added or replaced to perform various steps.

In the conventional PCR process, a wafer is sucked and held by a chuck, and in this state, a drum-shaped polishing roller having a polishing cloth spread on its surface is rotated to supply an abrasive agent made of a slurry containing abrasive grains. However, the chamfered surface is mirror-polished by bringing the chamfered surface of the wafer into contact with the polishing action surface of the rotating polishing roller.

[0004]

However, in the above-mentioned conventional method, as shown in FIG. 4, the abrasive grains contained in the slurry are solidified on the wafer contact surface of the chuck, and the solidification is caused by the contact between the wafer and the chuck. There is a problem that the object scratches the wafer surface and leaves the chuck mark 2 on the surface of the wafer 1. In addition, by using a slurry containing abrasive grains as a polishing agent, impurity metals such as transition metals dissolved in the slurry are adsorbed on the wafer, and the pressure and temperature generated when the polishing machine is subsequently driven are driven. There is also a problem that the cleanliness of the wafer is lowered due to diffusion into the wafer as a force.

An object of the present invention is to provide a method for polishing a semiconductor wafer which does not cause scratches on the surface of the wafer due to abrasive grains. Another object of the present invention is to provide a method for polishing a semiconductor wafer capable of maintaining the cleanliness of the wafer.

[0006]

The invention according to claim 1 is
As shown in FIG. 1, a polishing roller 14 having a polishing cloth spread on the surface thereof is opposed to the chamfered surface 10a of the semiconductor wafer 10, and the polishing roller 14 is rotated while supplying the polishing agent 13 to rotate the chamfered surface 10a of the wafer 10. This is an improvement of the polishing method for a semiconductor wafer, in which the chamfered surface 10a is mirror-polished by contacting with the. This characteristic constitution is that the polishing agent 13
Is composed of an etching solution.

According to the first aspect of the present invention, the solidification product of the polishing abrasive grains formed on the wafer contact surface of the chuck is not generated when the conventional abrasive containing the slurry containing the polishing abrasive grains is used. . Therefore, scratches caused by the solidified matter are not generated on the wafer surface, and chuck marks are not formed on the wafer surface. In addition, since it is possible to suppress the contamination by the transition metal that is conventionally dissolved in the slurry containing the abrasive grains, the cleanliness of the wafer surface can be maintained.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the drawings. The polishing method of the present invention is a method performed by a PCR step, and a wafer is processed by performing the following steps before this PCR step.

First, the grown silicon single crystal ingot is cut into a block shape by cutting the tip and the end, and the outer diameter of the ingot is ground into a block body to make the diameter of the ingot uniform. Orientation flats and orientation notches are applied to this block body to show a specific crystal orientation. Orientation flats and notches are used as reference positions for mask alignment in the device process. After this process, the block body is sliced into a plurality of wafers by a blade at a predetermined angle with respect to the rod axis direction. The sliced wafer is chamfered around the wafer in order to prevent chips and chips at the peripheral portion of the wafer. By carrying out this chamfering, for example, when epitaxially growing on a surface of a silicon wafer which is not chamfered, it is possible to suppress the crown phenomenon in which abnormal growth occurs in the peripheral portion and rises annularly.

Next, the work-affected layer formed on the front and back surfaces of the wafer by mechanical processing such as slicing or chamfering is mechanically polished (lapping) to increase the flatness of the wafer surface and the parallelism of the wafer. The lapped wafer is cleaned and sent to the next step. Next, etching is performed to remove the work-affected layer on the front and back surfaces of the wafer. The etching solution for etching may be an acid etching solution or an alkaline etching solution and is not particularly limited.

The wafer after etching is subjected to a PCR process so that the chamfered surface of the wafer is mirror-polished. FIG. 1 shows a chamfered mirror polishing device. The chamfered mirror polishing apparatus is composed of upper and lower chucks 11 and 12 for sandwiching a wafer 10 from above and below and horizontally rotating the wafer, a pipe 13a for supplying a polishing agent 13, and a polishing roller 14 for polishing the wafer chamfered surface to a mirror surface. It

Support shafts 11a and 12a are provided on the upper and lower chucks 11 and 12, respectively, and a rotary motor (not shown) is further connected thereto. The upper and lower chucks 11 and 12 are formed to have a diameter smaller than the wafer diameter, and have a size such that only the chamfered surface 10a of the wafer is exposed by sandwiching the wafer 10 from above and below. The polishing roller 14 is formed in a drum shape, and a polishing cloth is spread on the surface thereof. Polyester felt, laminate, etc. are used for the polishing cloth. The polishing roller 14 is provided with a support shaft 14a, which is rotated by a rotation motor (not shown) so that the chamfered surface of the wafer and the surface of the polishing roller 14 face each other. The pipe 13a is provided at a position where the polishing agent 13 is supplied to the chamfered surface of the wafer.

A characteristic feature of the present invention is that the abrasive 13 is composed of an etching solution. Examples of the etching solution used for the polishing agent include an alkali etching solution having an ability to etch silicon, and potassium hydroxide, sodium hydroxide, an amine compound, and tetramethylammonium hydroxide are selected as the alkali etching solution. The pH of the alkaline etching solution is 9-11. The preferred pH is 9.5 to 10.5. If the pH of the etching solution is less than the lower limit value, the polishing rate becomes small, and mirror polishing takes time, resulting in a decrease in throughput. If the upper limit is exceeded, the surface roughness of the wafer is likely to occur.

Although it depends on the structure and size of the processing apparatus, the supply amount of the abrasive is 200 to 1500 ml / min. If it is less than the lower limit, scratches are likely to occur on the wafer surface, and cracks or chips may occur. If it exceeds the upper limit, there is a problem that the wafer surface is eroded by the polishing agent.
The rotation speed of the polishing roller is not particularly limited, but is usually 1
It is from 00 to 1000 rpm. If the rotation speed is less than the lower limit value, the polishing rate decreases, and if it exceeds the upper limit value, uneven polishing occurs. The polishing pressure when the polishing roller is brought into contact with the chamfered surface of the wafer is not particularly limited, but is 1 to 2 kg. If it is less than the lower limit, the polishing rate is lowered, and if it is more than the upper limit, scratches are likely to occur on the wafer surface, and cracks or chips may occur.

The abrasive of the present invention may further contain abrasive grains in addition to the etching liquid. The content of the abrasive grains at this time is 1% by weight or less relative to 100% by weight of the abrasive. . If the amount of the polishing abrasive grains is within the above range, the polishing abrasive grains contained in the polishing agent will not solidify and scratch the wafer surface, and the polishing rate can be further increased.

When polishing a wafer with this chamfered mirror polishing apparatus, the wafer 10 is moved to the upper and lower chucks 1
It is sandwiched by 1 and 12 and horizontally rotated by a rotation motor (not shown). The chamfered surface is mirror-polished by rotating the polishing roller 14 while contacting the chamfered surface of the wafer while dropping the polishing liquid 13 from the pipe 13a. By performing chamfered surface mirror polishing using an abrasive composed of an etching solution, the polishing abrasive grains that are the base of the solidified product that was formed on the wafer contact surface of the chuck due to the conventional polishing abrasive grains are not included. No scratches are formed on the wafer surface even when the wafer and the chuck are in contact with each other.

Next, the PCR-finished wafer surface is subjected to mirror-polishing, which is a combination of mechanical or physical polishing and chemical polishing, to form a mirror-polished wafer having optical gloss and no processing distortion. . The wafer after the surface mirror polishing is cleaned and sent to a device manufacturing process.

In the present embodiment, not only the upper and lower chucks but either one-sided chuck may be used. Also,
Although the polishing roller has a drum shape, it may be a ring-shaped polishing roller as shown in FIG. The polishing roller 20 is a polishing roller for chamfering, the inner peripheral surface of which serves as a polishing working surface, and a groove 21 for chamfering is engraved over the entire circumference of this working surface. Reference numeral 22 is a chuck, 23 is a support shaft, and 24 is a rotary motor.

[0019]

EXAMPLES Next, examples of the present invention will be described together with comparative examples. <Example> First, a wafer after chamfering, lapping and etching was prepared. Then, 2w as an abrasive
t% piperazine, 0.2 wt% KOH and 0.1 w
It was prepared by mixing each t% chelating agent and further diluting it 20 times with water. Next, this wafer was held on a chuck of a PCR processing machine (SCP-200 manufactured by Fujikoshi Machinery Co., Ltd.), and the chamfered surface of the wafer was subjected to PCR processing while dripping an abrasive near the PCR processing surface.

Comparative Example A wafer was subjected to PCR processing in the same manner as in Example except that an edge mirror IV (manufactured by Speedfam) diluted 20 times with water was used as an abrasive containing abrasive grains. went.

<Comparison Test and Evaluation> The wafers subjected to the PCR processing in the examples and the comparison examples were washed with alkali. The appearance of the cleaned wafer was visually inspected under a halogen lamp. In the pass / fail judgment, those recognized as chuck marks were judged to be unacceptable. The inspection result is shown in FIG.

As is clear from FIG. 3, in the comparative examples using the abrasives containing the abrasive grains which have been conventionally used, many marks of contact points with the chuck remain on the wafer surface. % Was judged to be unacceptable due to poor appearance. On the other hand, in the example using the abrasive-free abrasive,
It was found that scratches recognized as chuck marks were scarcely recognized, and only 4% was judged to be unacceptable as a defective appearance, and the defective appearance rate was significantly reduced.

[0023]

As described above, according to the method for polishing a semiconductor wafer of the present invention, the polishing roller having a polishing cloth spread on the surface is opposed to the chamfered surface of the semiconductor wafer, and the polishing roller is supplied while supplying the polishing agent. This is an improvement in a method of mirror-polishing a chamfered surface by rotating the chamfered surface so that the chamfered surface is brought into contact with the chamfered surface, and the polishing agent is an etching solution. Since the slurry containing the abrasive grains is not used, the solidified substance of the abrasive grains is not formed at the contact portion between the wafer and the chuck, and the scratches caused by the solidified substance on the wafer surface are not generated. . Further, since the slurry containing polishing abrasive grains is not used, the cleanliness of the wafer can be maintained without being contaminated by impurity metals such as transition metals.

[Brief description of drawings]

FIG. 1 is a cross-sectional configuration diagram of a chamfered mirror polishing device used in a PCR process.

FIG. 2 is a perspective view of another chamfered mirror polishing device.

FIG. 3 is a diagram showing a defective appearance rate after PCR processing in Examples and Comparative Examples.

FIG. 4 is a plan view of a wafer having chuck marks formed on its surface by performing a conventional PCR process.

[Explanation of symbols]

10 wafers 10a Chamfer 13 Abrasive 14,20 Polishing roller

Claims (4)

[Claims] 1. A polishing roller (1) having a polishing cloth spread on the surface thereof.
4,20) is opposed to the chamfered surface (10a) of the semiconductor wafer (10), the polishing roller (14,20) while supplying the polishing agent (13).
In the method for polishing a semiconductor wafer in which the chamfered surface (10a) of the wafer (10) is brought into contact with the chamfered surface (10a) by mirror polishing, the polishing agent (13) is composed of an etching solution. A characteristic method for polishing a semiconductor wafer. 2. The polishing method according to claim 1, wherein the etching solution is an alkali etching solution, and the alkali etching solution contains potassium hydroxide, sodium hydroxide, an amine compound or tetramethylammonium hydroxide. 3. The pH of the alkaline etching solution is 9-11.
The polishing method according to claim 1 or 2. 4. The abrasive (13) further contains abrasive grains in addition to the etching liquid, and the content of the abrasive grains is 1% by weight or less relative to 100% by weight of the abrasive. 4. The polishing method according to any one of 3 to 3.