JP2003243341A - Polishing agent and method for polishing silicon wafer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a silicon wafer polishing agent and a method, which are capable of efficiently preventing a silicon wafer from being contaminated with metal ions in a polishing process and restraining the silicon wafer from deteriorating in quality. <P>SOLUTION: The silicon wafer polishing agent contains silica as polishing abrasive grains and an organic compound including thioketone groups or thiol radicals and amino groups. <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 polishing agent and a polishing agent for polishing a silicon wafer, particularly a semiconductor silicon wafer (hereinafter, may be simply referred to as a wafer, a silicon wafer or a semiconductor wafer), which is capable of preventing metal impurity contamination. Regarding the method.

[0002]

2. Description of the Related Art Generally, a method for manufacturing a semiconductor wafer comprises a slicing step for slicing a single crystal ingot to obtain a thin disk-shaped wafer, and a wafer obtained by the slicing step. Crack,
A chamfering step of chamfering the outer peripheral portion of the wafer to prevent chipping, a lapping step of flattening the chamfered wafer, an etching step of removing processing strain remaining on the chamfered and lapped wafer, and this etching. And a cleaning step of cleaning the polished wafer to remove the polishing agent and foreign matter adhering to the polished wafer.

In the polishing step, fine SiO 2 is generally used.
₂ abrasive silica-containing abrasive material dispersed colloidally in the alkaline aqueous solution of about pH = 9 to 12 and is used, Si
It is polished by the combined action of the mechanical action of O ₂ and the chemical action of etching silicon with an alkaline solution. In addition, a small amount of amine such as ethanolamine is often added to the silica-containing polishing agent for the purpose of improving the polishing rate.

However, the alkaline silica-containing polishing agent contains metal impurities, and examples of the metal impurities contained in the polishing agent include iron, copper, nickel and chromium.

The inventors of the present invention continued to study polishing processing of semiconductor silicon wafers using a silica-containing polishing agent containing these metal impurities. As a result, some of copper, nickel and the like present in the silica-containing polishing agent were found. It has been revealed that the metal ions of the above diffuse deeply inside the wafer during polishing, deteriorating the quality of the wafer and significantly deteriorating the characteristics of the semiconductor device formed by the wafer.

As a measure for preventing the deterioration of the wafer quality due to the silica-containing polishing agent as described above, it is conceivable to use a highly purified silica-containing polishing agent. However, a commercially available high-purity polishing agent is extremely expensive, and using it for polishing a silicon wafer is completely unacceptable in terms of cost.

In order to solve this problem, the present inventors have investigated the cause of metal contamination during polishing, and as a result,
An amine added for the purpose of improving the polishing rate (for example, an aliphatic alcohol or an aromatic hydrocarbon amine compound such as an alkane, an alkene, an arylamine, an aralkylamine containing an amino alcohol or an amino group) promotes metal contamination. It became clear.

From this, it can be considered to stop the addition of amine to the polishing agent as a measure for preventing metal contamination during polishing. However, when the addition of amine is stopped, the polishing rate is remarkably reduced, resulting in a decrease in productivity.

The present invention has been made in view of the above circumstances, and it is possible to efficiently prevent metal impurities from contaminating a wafer during polishing and to prevent the polishing rate from being affected. It is an object of the present invention to provide a polishing agent and a method for polishing a semiconductor silicon wafer, which makes it possible to perform polishing without deteriorating the quality of a semiconductor wafer using this polishing agent.

[0010]

Means for Solving the Problems and Modes for Carrying Out the Invention In view of the above-mentioned problems of the prior art, the inventors of the present invention can prevent metal contamination during polishing even if amine is added. As a result of continued earnest studies on polishing agents for wafer polishing, it is possible to prevent metal contamination during polishing by adding a compound having a thioketone group or a thiol group and an amino group to a silica-containing polishing agent. And has arrived at the present invention.

Therefore, according to the present invention, a polishing agent for polishing a silicon wafer, characterized in that silica is used as polishing abrasive grains and contains an organic compound having a thioketone group or a thiol group and an amino group, and a silicon wafer is polished. In doing so, there is provided a method for polishing a silicon wafer, which comprises polishing with the above-mentioned polishing agent for polishing a silicon wafer.

The present invention will be described in more detail below.
The polishing agent for polishing a silicon wafer according to the present invention uses silica as polishing abrasive grains, to which an organic (hydrocarbon-based) compound having a thioketone group or a thiol group and an amino group is added.

Here, as the silica as the abrasive grains, fine silica, particularly an average particle size of 5 to 100,000 n is used.
It is preferable to use silica having a particle size of m, particularly 10 to 1,000 nm, which may be commercially available as colloidal silica, fumed silica, precipitated silica or the like.

The organic compound having a thioketone group or a thiol group and an amino group is a hydrocarbon compound having these groups, which may contain other sulfur atom or nitrogen atom in the molecule. Any of these may be used, but a non-silane compound is preferable, and specifically, thiocarbohydrazide, thiocarbanilide, o-
Aminothiophenol, 1,2,4-triazole-3
-Thiol, 3-amino-1,2,4-triazole-
5-thiol, 2-amino-5-mercapto-1,3
4-thiadiazole, 4-amino-3-hydrazino-5
-Mercapto-1,2,4-triazole etc. can be mentioned, and these 1 type can be used individually or in combination of 2 or more types.

The amount of the organic compound having a thioketone group or thiol group and an amino group used is silica 100
The amount is preferably 0.001 to 100 parts by weight, more preferably 0.01 to 50 parts by weight, and particularly preferably 0.1 to 10 parts by weight. If the amount used is too small, a sufficient effect for preventing metal contamination may not be obtained depending on the amount of contamination, and if it is too large, the polishing rate may be reduced.

The method for polishing a silicon wafer, particularly a semiconductor silicon wafer, of the present invention is characterized by using the above-mentioned polishing agent for polishing a silicon wafer to prevent metal impurities from contaminating the silicon wafer during polishing. is there.

In the present invention, a compound having a thioketone group or a thiol group and an amino group is added to the silica-containing polishing agent so that the metal ions present in the silica-containing polishing agent are mixed with the thioketone group or the thiol group. It is possible to prevent the adsorption to the wafer by capturing with a compound having an amino group.

As a method of polishing a silicon wafer using the above-mentioned polishing agent, a conventional method can be adopted. In this case, as the polishing agent, the silica polishing abrasive grains are mixed with water, alcohol such as methanol or the like or a mixed solvent thereof in an amount of 0.1 to 2
Dispersed and diluted to a concentration of 0% by weight, particularly 0.5 to 5% by weight,
And it is preferable to use it in the state adjusted to pH 8-12.5, especially pH 10-12.

[0019]

EXAMPLES The present invention will be specifically described below by showing Examples and Comparative Examples, but the present invention is not limited to the following Examples.

In the following examples, parts indicate parts by weight. rpm indicates the number of rotations per minute. As the polishing device, the device shown in FIG. 1 was used. Here, the polishing apparatus 1 of FIG. 1 includes a rotary platen 2, a wafer holder 3,
And an abrasive supply device 4. It has a rotary platen 2 and a rotary platen body 5, and a polishing pad 6 is attached to the upper surface thereof. It is what is done.
The wafer holder 3 holds the wafer W on its lower surface by vacuum suction or the like, and is rotated by the rotating shaft 8 and simultaneously presses the wafer W against the polishing pad 6 with a predetermined load. Further, the polishing agent supply device 4 supplies the polishing agent 9 onto the polishing pad 6 at a predetermined flow rate, the polishing agent 9 is supplied between the wafer W and the polishing pad 6, and the wafer W is polished. Is.

[Examples, Comparative Examples] Sample wafer: p-type manufactured by Czochralski (CZ) method, crystal orientation <100>, 150 mmφ, silicon wafer polishing pad: nonwoven fabric (bearo type), hardness 70 (Asker C Hardness) Abrasive: A colloidal silica stock solution AJ-1325 [trade name of Nissan Chemical Industries, Ltd.] containing 20% by weight of SiO ₂ was dispersed in an alkaline aqueous solution (the above colloidal silica stock solution contained 12 parts based on the total amount of the abrasive). 0.5% by weight (adjusted to 2.5% by weight of SiO ₂ ), 5 parts of amino alcohol (ethanolamine) was added to 95 parts of the colloidal silica stock solution, and thiocarbohydrazide was added to 0.5 parts by weight in the examples. Addition of 01 mol / l, Fe, Cu, Ni, C
A colloidal silica abrasive which was intentionally contaminated by adding 100 ppb of each r ion was used. In the comparative example, one without addition of thiocarbohydrazide was used. Polishing load: 400 g / cm ² Polishing time: 10 minutes Rotating surface plate (polishing pad) rotation speed: 160 rpm Wafer holder rotation speed: 160 rpm

Under the above polishing conditions, sample wafers (10 wafers each) were polished using the polishing apparatus shown in FIG. 1, and Fe, Cu, Ni and Cr contamination amounts of the polished wafers were investigated.

The polished sample wafer was evaluated as follows. After the polished sample wafer was heat-treated at 650 ° C., the thermal oxide film on the polished surface was vapor-phase decomposed with hydrofluoric acid vapor, and this was recovered as droplets containing hydrochloric acid and analyzed by atomic absorption spectrometry. According to this analysis method, Cu diffused inside the wafer can also be evaluated.

The results are shown in Table 1. As is clear from Table 1, it was found that the addition of a small amount of thiocarbohydrazide significantly improved the metal contamination on the wafer.

[0025]

[Table 1] * The polishing rate ratio is a ratio based on a comparative example (a conventional compounding system of amino alcohol alone).

[0026]

According to the present invention, it is possible to very effectively prevent the contamination of the wafer by metal ions during polishing and to prevent the deterioration of the wafer quality.

[Brief description of drawings]

FIG. 1 is a schematic side view of a polishing apparatus used in an example.

[Explanation of symbols]

1 Polishing device 2 rotating surface plate 3 Wafer holder 4 Polishing agent supply device 5 rotating surface plate body 6 polishing pad 7 rotation axis 8 rotating shafts 9 Abrasive W wafer

Claims (2)

[Claims] 1. A polishing agent for polishing a silicon wafer, which comprises silica as abrasive grains and contains an organic compound having a thioketone group or a thiol group and an amino group. 2. A method of polishing a silicon wafer, which comprises polishing the silicon wafer using the polishing agent for polishing a silicon wafer according to claim 1.