JPH11186202A - Abrasive for polishing semiconductor silicon wafer and method of polishing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an abrasive used to polish semiconductor silicon wafers, the main ingredient of which is a silica-containing abrasive and which efficiently prevents metal contamination, in particular, copper contamination, in the wafers during the polishing, and furthermore enables to enhance the polishing rate, by adding inorganic oxoacid compound(s) to the abrasive. SOLUTION: Inorganic oxoacid compound(s), such as silicate compound(s) or aluminate compound(s) is (are) added to a silica-containing abrasive. Under a polishing condition, sample wafers are polished using a polishing machine, and the polishing rate is measured by changing the added amount of sodium silicate, of sodium aluminate, and of an amine, to the colloidal-silica-containing abrasive to specified concentrations, respectively. The obtained result indicates that, by just adding a small amount of sodium silicate or of sodium aluminate, the polishing rate increases remarkably as compared to the case of not adding them, yielding the effect that is equal to or more than that in the case of adding the amine.

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 method for a semiconductor silicon wafer (hereinafter sometimes simply referred to as "wafer", "silicon wafer" or "semiconductor wafer") capable of improving a polishing rate and preventing metal contamination. About.

[0002]

2. Related Art In general, a method for manufacturing a semiconductor wafer includes a slicing step of slicing a single crystal ingot to obtain a thin disk-shaped wafer, and a slicing step for preventing cracking and chipping of the wafer obtained by the slicing step. A chamfering step for chamfering the outer peripheral portion, a lapping step for flattening the chamfered wafer, an etching step for removing processing strain remaining on the chamfered and wrapped wafer, and mirroring the etched wafer surface The polishing process includes a polishing process and a cleaning process for cleaning the polished wafer and removing abrasives and foreign substances attached to the wafer.

In the polishing step, generally, fine SiO 2
₍₂₎ A silica-containing abrasive in which abrasive grains are colloidally dispersed in an alkaline aqueous solution having a pH of about 9 to 12 is used.
Polishing is performed by a combined action of the mechanical action of O ₂ and the chemical action of etching silicon with an alkaline solution. In addition, this silica-containing polishing agent is often used by adding several percent of an amine for the purpose of improving the polishing rate.

[0004]

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

The inventors of the present invention have continued to study the polishing of semiconductor silicon wafers using a silica-containing abrasive containing these metal impurities, and have found that some of the copper, nickel, etc. present in the silica-containing abrasive are present. It has been clarified that the metal ions diffuse deep into the wafer during polishing, degrade the quality of the wafer, and significantly reduce the characteristics of the semiconductor device formed by the wafer.

As a countermeasure for preventing the deterioration of wafer quality caused by the above-mentioned silica-containing abrasive, it is conceivable to use a highly purified silica-containing abrasive. However, commercially available high-purity abrasives are extremely expensive, and using them for polishing silicon wafers is not worth the cost.

To solve this problem, the present inventors
Investigation of the cause of metal contamination during polishing revealed that amine added for the purpose of improving the polishing rate promoted metal contamination.

From this, it is conceivable to stop the addition of amine to the polishing agent as a measure for preventing metal contamination during polishing. However, when the addition of the amine is stopped, the polishing rate is remarkably reduced, and the productivity is lowered.

In view of the above-mentioned problems of the prior art, the present inventors have proposed a semiconductor silicon wafer polishing method capable of improving a polishing rate without adding an amine and preventing metal contamination during polishing. As a result of intensive studies on polishing agents for polishing, it has been found that by adding an oxo acid compound to a silica-containing polishing agent, metal contamination during polishing can be prevented and the polishing rate can be further improved. The present invention has been reached.

The present invention provides a polishing agent for polishing a semiconductor silicon wafer and a semiconductor using the polishing agent, which can efficiently prevent metal impurities, particularly copper contamination, on a wafer during polishing and can further improve the polishing rate. It is an object of the present invention to provide a method for polishing a semiconductor silicon wafer that enables polishing without deteriorating the wafer quality.

[0011]

In order to solve the above-mentioned problems, an abrasive for polishing a semiconductor silicon wafer according to the present invention comprises:
It is characterized by comprising a silica-containing abrasive as a main component and adding an inorganic oxoacid compound.

Examples of the oxo acid compound include silicic acid compounds and aluminate compounds such as sodium silicate and sodium aluminate. These may be used alone or in a mixed state.

The amount of the above additives depends on the type of the additives, and is not particularly limited as long as the effects of the present invention are achieved. In the case of sodium silicate or sodium aluminate, the ability to suppress Cu contamination and accelerate the polishing rate is achieved. From the viewpoint of action and cost, it is preferable to add the abrasive so as to be 2.5 to 5 wt% with respect to the total amount of the abrasive. Specifically, the addition amount may be adjusted with respect to the abrasive supply tank or the total amount of the abrasive before being put into the tank.

The method for polishing a semiconductor silicon wafer of the present invention is characterized in that the polishing rate is improved and metal contamination on the semiconductor silicon wafer during polishing is prevented by using the above-mentioned polishing agent for semiconductor silicon wafer. Is what you do.

[0015]

In the present invention, by adding an inorganic oxo acid compound, for example, a silicon compound or an aluminate compound, to a silica-containing abrasive, metal ions present in the silica-containing abrasive can be converted to an inorganic oxo acid compound. In addition to using an additive to capture and prevent adsorption to the wafer, the chemical-mechanical action of the polishing process on the semiconductor silicon wafer is promoted, and the polishing rate can be improved.

[0016]

The present invention will be described more specifically with reference to the following examples.

FIG. 3 is a side view showing a polishing apparatus used in the embodiment of the present invention. In FIG. 3, the polishing apparatus 10 includes:
It comprises a rotating platen 12, a wafer holder 13, and an abrasive supply device 14. The rotary platen 12 is a rotary platen body 15
And a polishing pad 16 is attached to the upper surface thereof.
The rotating platen 12 is rotated by a rotating shaft 17 at a predetermined rotation speed. The wafer holder 13 holds the wafer W on its lower surface by vacuum suction or the like, and is rotated by the rotating shaft 18 and simultaneously presses the wafer W against the polishing pad 16 with a predetermined load. The abrasive supply device 14 supplies an abrasive 19 onto the polishing pad 16 at a predetermined flow rate.
9 is supplied between the wafer W and the polishing pad 16 so that the wafer W is polished.

Examples 1 and 2 and Comparative Example 1 (Measurement of polishing rate by adding sodium silicate, sodium aluminate and amine) Sample wafer: p-type, crystal orientation <100> manufactured by Czochralski (CZ) method , 150 mmφ, silicon wafer Polishing pad: non-woven fabric (Bearo type), hardness 70 (Asker C hardness) Abrasive: Commercially available colloidal silica stock solution containing ₂ wt% SiO ₂ (so that the stock solution becomes 10 wt% based on the total amount of the abrasive) Sodium silicate, sodium aluminate or an amine (in the comparative example, N- (β-aminoethyl) ethanolamine was used as the amine) in the following amount:
A colloidal silica abrasive, the remainder of which was diluted with pure water, was used. Polishing load: 350 g / cm ² Polishing time: 10 minutes

Under the above polishing conditions, the addition amounts of sodium silicate (Example 1), sodium aluminate (Example 2) and amine (Comparative Example 1) to the colloidal silica abrasive were 0.5, 0.75, and 1. 25, 2.5, 5 wt%
Then, the sample wafer (two each) was polished using the polishing apparatus shown in FIG. 3, and the polishing rate during polishing was measured.
The result is shown in FIG.

As is clear from FIG. 1, the addition of a small amount of sodium silicate or sodium aluminate significantly increases the polishing rate as compared with the case where no addition is performed, and can obtain an effect equal to or higher than that when the amine is added. . As Comparative Example 1, the polishing rate when an amine is added is also described, but the additive の of the present invention (sodium silicate (Example 1),
It can be seen that the polishing rate of the polishing agent to which 1% by weight or more of sodium aluminate (Example 2) was added was more stable than that of the polishing agent to which amine (Comparative Example 1) was added. .

Examples 3 and 4 and Comparative Example 2 (Confirmation of Prevention of Copper Contamination by Addition of Sodium Silicate, Sodium Aluminate and Amine) Colloidal silica intentionally contaminated with 100 ppb of Cu ions under the same polishing conditions as in Examples 1 and 2. The amount of addition of sodium silicate (Example 3), sodium aluminate (Example 4) and amine (Comparative Example 2) to the abrasive was 0.
5, 0.75, 1.25, 2.5, and 5 wt%, and the sample wafers (2 each) using the polishing apparatus shown in FIG.
Were polished, and the amount of Cu contamination of the polished wafer was investigated.

The polished sample wafer was evaluated as follows. After heat treatment of the polished sample wafer at 650 ° C., the thermally oxidized film on the polished surface was vapor-phase decomposed with hydrofluoric acid vapor, collected as droplets containing hydrochloric acid, and analyzed by atomic absorption spectrometry. By this analysis method, it is possible to evaluate Cu diffused inside the wafer.

FIG. 2 shows the results. As is clear from FIG. 2, it was found that the addition of a small amount of sodium silicate (Example 3) and sodium aluminate (Example 4) greatly improved metal contamination on the wafer. As Comparative Example 2, the amount of metal contamination on the wafer when an amine is added is also described. In the case of a polishing agent to which an amine (Comparative Example 2) is added, as described above, Cu contamination accelerates as the addition amount increases. It turns out that it is done.

In particular, when sodium silicate or sodium aluminate is added in an amount of 2.5 wt% or more, the difference in Cu contamination from the case where an amine is added becomes remarkable. The upper limit of the amount of sodium silicate or sodium aluminate to be added is about 5 wt% in consideration of the amount of contamination and the polishing rate.

[0025]

As described above, according to the present invention, the contamination of a wafer by metal ions during polishing can be prevented very efficiently, the deterioration of the wafer quality can be eliminated, and the polishing rate for a semiconductor silicon wafer can be improved. The effect is achieved.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the additive concentration and the polishing rate when various additives shown in Examples 1 and 2 and Comparative Example 1 are added to a silica-containing abrasive.

FIG. 2 shows a Cu contamination level of a semiconductor silicon wafer with respect to a change in additive concentration when various additives shown in Examples 3 to 4 and Comparative Example 2 were added and polished with a silica-containing abrasive intentionally contaminated with Cu. FIG.

FIG. 3 is a side view showing a polishing apparatus used in Examples and Comparative Examples of the present invention.

[Explanation of symbols]

10: Polishing device, 12: Rotary platen, 13: Wafer holder, 14: Abrasive supply device, 15: Rotary platen body, 1
6: polishing pad, 17: rotating shaft, 18: rotating shaft,
19: abrasive, W: wafer

Continued on the front page (72) Inventor Kenji Yamagishi 150 Odakura Odaikura, Nishigo-mura, Nishishirakawa-gun, Fukushima Prefecture Semiconductor Shirakawa Research Center, Shin-Etsu Semiconductor Co., Ltd.

Claims (6)

[Claims] An abrasive for polishing semiconductor silicon wafers comprising a silica-containing abrasive as a main component and an inorganic oxo acid compound added thereto. 2. An abrasive for polishing a semiconductor silicon wafer according to claim 1, wherein said inorganic oxo acid compound is a silicate compound or an aluminate compound. 3. An abrasive for polishing a semiconductor silicon wafer according to claim 1, wherein said inorganic oxo acid compound is an oxo acid salt. 4. An abrasive for polishing a semiconductor silicon wafer according to claim 3, wherein said inorganic oxo acid salt is a silicate or an aluminate. 5. The semiconductor silicon wafer according to claim 1, wherein the amount of the inorganic oxo acid compound is 2.5 to 5% by weight based on the total amount of the polishing agent. Polishing abrasive. 6. An abrasive for polishing a semiconductor silicon wafer according to any one of claims 1 to 5,
A method for polishing a semiconductor silicon wafer, wherein the polishing speed is improved and metal contamination on the semiconductor silicon wafer during polishing is prevented.