JP3290189B2 - Polishing method of silicon wafer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a semiconductor manufacturing process .
Silicon wafer using a kick silicon wafer over Research Migakuzai
A polishing method .

[0002] The mirror polishing process of a silicon wafer for a semiconductor is intended for a lapping process for removing a cut strain layer and undulation generated when a silicon single crystal ingot is cut into a wafer by cutting, and a silicon wafer that has passed through the lapping process. There is a polishing step of finishing by polishing to a surface accuracy as described below. The polishing step is classified into a primary polishing step called coarse polishing and a final polishing called fine polishing. The process is further divided into two steps, which are called primary and secondary polishing steps.

The present invention specifically describes a primary polishing step or a primary and secondary polishing step in which the primary polishing step is further divided into two steps (hereinafter, these are collectively simply referred to as a primary polishing step). Polishing agent.

[0004]

2. Description of the Related Art In a primary polishing process, artificial leather in which a plurality of lapping silicon wafers are attached to a polishing block and the polishing block is bonded on a rotary table.
(Polisher) by applying appropriate pressure to pH 9-12
Addition of alkaline colloidal silica or silica powder dispersed in water causes the mechanochemical action between the polishing liquid and the silicon wafer, but the polishing agent used here is usually recycled due to cost reduction. It is generally used.

[0005]

However, when the conventional abrasive is used for this recycling, the polishing efficiency for the silicon wafer is greatly deteriorated upon recycling.
There is a disadvantage that the accuracy of the surface of the finished silicon wafer is deteriorated, and as a result, it is difficult to control the process in manufacturing the silicon wafer.

For example, US Pat. No. 3,170,273 describes polishing a silicon wafer using colloidal silica and silica gel. U.S. Pat. No. 4,169,337 discloses a method for improving polishing efficiency. Also, JP-A-58-2251
No. 77 discloses an improved method by adding quaternary ammonium and a salt thereof to a polishing liquid to be used.
Further, Japanese Patent Application Laid-Open No. Sho 62-30333 discloses a highly efficient method for polishing a silicon wafer by adding piperazine to alkaline colloidal silica.

However, in the above method, although the initial polishing efficiency of the polishing liquid is good, there is a common problem that when the polishing liquid is recycled, the polishing efficiency is greatly deteriorated, and it is difficult to control the polishing process. I have. Accordingly, an object of the present invention is to use a good silicon wafer polishing agent that has a small reduction in polishing efficiency during recycling and has a sufficient polishing amount .
To provide a polishing method for a silicon wafer .

[0008]

The silicon wafer abrasive used in the present invention is an alkaline colloidal silica solution containing silica having an average particle diameter of 7 to 100 nm, and 5 to 400% by weight based on the solid content of silica. % Of an organic water-soluble amine and 0.1 to 50% by weight based on silica solid content of a salt of a weak acid and an alkali metal.

The silica particle size in the alkaline colloidal silica solution used in the present invention is defined as follows: the alkaline colloidal silica solution is adjusted to pH 2-3 with an acid and dried at 120 ° C. The dried powder silica is sufficiently washed with distilled water to remove salts, dried at 105 ° C., and the specific surface area obtained by the nitrogen adsorption method is substituted into the following equation to obtain an average particle diameter.

## EQU1 ## Average particle diameter (nm) = 6 × 10 ³ / [specific surface area (m ² /
g) × density of amorphous silica (g / cm ³ )]

The alkaline colloidal silica solution used in the present invention has an average particle diameter of silica in the solution of 7 to 10%.
Any material can be used as long as it is 0 nm, and a commercially available product can also be used.

For example, Adelite AT-30S [Asahi Denka Kogyo Co., Ltd. average particle size 8.5 ± 1.5 nm: silica solid content 30]
Wt.], Adelaite AT-30 [Asahi Denka Kogyo Co., Ltd. average particle diameter 12.5 ± 2.5 nm: silica solid content 30 wt%], Adelaite AT-40 [Asahi Denka Kogyo Co., Ltd. average particle diameter 17. 5 ± 2.5 nm: silica solid content 40% by weight], Adelite AT-50 [Asahi Denka Kogyo Co., Ltd. average particle diameter 25 ±]
5 nm: silica solids content of 50% by weight], Adelite BT-
55 [Asahi Denka Kogyo Co., Ltd. average particle diameter 40 ± 10 nm: silica solid content 50% by weight], Adelaite BT-57 [Asahi Denka Kogyo Co., Ltd. average particle size 60 ± 10 nm: silica solid content 50]
Wt.], Adelite BT-59 [Asahi Denka Kogyo Co., Ltd. average particle diameter 85 ± 15 nm: silica solid content of 50 wt.%] And the like can be used.

The average particle size of the silica in the alkaline colloidal silica solution is preferably 7 to 70 nm, more preferably 10 to 50 nm. If the average particle size is less than 7 nm, the storage stability of the alkaline colloidal silica deteriorates, and if the average particle size exceeds the above range, precipitation occurs when left to stand, and it is necessary to perform redispersion treatment in use. As a result, workability deteriorates.

The silica in the alkaline colloidal silica solution may have an average particle diameter within the above range,
Depending on the form of the particle size distribution, the particle size of each silica may exceed the above range.

As the organic water-soluble amine used in the present invention, any organic amine which exhibits alkalinity when dissolved in water can be used, but is preferably a linear amine having 1 to 6 nitrogen atoms. It is preferred that the amine is a branched, branched or cyclic amine. Specifically, for example, N, N-diethylethanolamine, N, N-dimethylethanolamine, aminoethylethanolamine, N-methyl-N,
Examples of N-diethanolamine, N, N-dibutylethanolamine, N-methylethanolamine, monoethanolamine, diethanolamine and alkylamine include 3,3′-diaminodipropylamine, iminobispropylamine, monoethylamine, diethylamine and
Ethoxypropylamine, 3-diethylaminopropylamine, dibutylaminopropylamine, propylamine, monomethylaminopropylamine, dimethylaminopropylamine, methyliminobispropylamine,
3-methoxypropylamine, hydrazine, ethylenediamine, diethylenetriamine, triethyltetramine, tetraethylpentamine, diethylamine, phenethylamine, benzylamine, 3-amino-1,2,4-
Examples include triazole, 1-aminoethylpiperazine, α-amino-ε-caprolactam, and the like.

From the viewpoint of solution stability, alkanolamines and alkylamines are more preferred as the organic water-soluble amine, and particularly preferred are aminoethylethanolamine, monoethanolamine, monoethylamine, hydrazine, ethylenediamine, diethylenetriamine. It is.

The organic water-soluble amine is added in an amount of 5 to 400% by weight, preferably 50 to 350% by weight, based on the solid content of silica. If the amount of the organic water-soluble amine is smaller than the above amount, the polishing amount is reduced and the efficiency is poor, and if the amount exceeds the above amount, the polishing efficiency cannot be improved, and the surface accuracy of the finished silicon wafer is rather improved. And the stability of the alkaline colloidal silica rapidly deteriorates.

The salt of a weak acid and an alkali metal used in the present invention is not particularly limited as long as it is a salt of an alkali metal. Specific examples include sodium, potassium, lithium and the like as alkali metal components. the component _{^{CO 3 2-, PO 4 3-,}} HCO 3 -, carboxylic acid (R-CO
^{O -, R = H, CH} 3, C 2 H 5), BO 3 3-, BO 3 -, HP
O ₄ ^2- , HPO _4- ^{and the} like can be exemplified, and particularly preferably, any of sodium and potassium,
_{^{O 3 2-, PO 4 3-,}} HCO 3 - Good salt with any of the.

The amount of the salt of a weak acid and an alkali metal is 0.1 to 50% by weight, preferably 1 to 4% by weight, based on the solid content of silica.
5% by weight. If the amount of the salt of the weak acid and the alkali metal is less than the above-mentioned amount relative to the silica solid content, the recycle performance aimed at by the present invention is insufficient, and if the amount is more than 50% by weight, the stability of the alkaline colloidal silica solution is increased. Is not suitable because it significantly worsens.

Further, the silicon wafer abrasive of the present invention requires the presence of an alkaline colloidal silica solution, an organic water-soluble amine, and a salt of a weak acid and an alkali metal. You can not demonstrate.

[0020]

EXAMPLES The present invention will be further described below with reference to examples, but the present invention is not limited to these examples. Example 1 An alkaline colloidal silica solution having an average silica particle diameter of 25 nm and a silica solid content of 30% by weight [Adelite AT-3]
0: Asahi Denka Kogyo Co., Ltd.] was diluted to 5% by weight of silica solids. To 1,000 parts by weight of this solution, 150 parts by weight of N, N-dimethylethanolamine as an organic water-soluble amine (300% by weight based on silica solids) and 20 parts of K ₂ CO ₃ were added.
It was added at a ratio of 40 parts by weight (40% by weight based on the solid content of silica) and sufficiently stirred until the mixture became uniform to obtain an abrasive.

Using this abrasive, a silicon wafer was polished under the following conditions. Polishing machine: LPH-15 manufactured by Lapmaster
Improved polishing machine diameter: 15 inches Polishing machine rotation speed: 70 rpm Silicon wafer: 4 inches in diameter (100) P-type CZ method Polishing pressure: 400 g / cm ² Polishing temperature: 40 ° C. Abrasive supply amount: 10 liter / hour Polishing time 1 hour Polishing number: 2

The used abrasive was filtered through a paper filter having a pore size of 6 μm and reused. One cycle from the polishing to the filtration step was performed, and a total of 20 cycles of the abrasive were recycled.

The removal amount of the silicon wafer by polishing (the amount of reduction in the thickness of the silicon wafer) in each cycle was measured, and the change in the polishing efficiency was examined. As a result of this test, the polishing removal amount in the first cycle was 65 μm, the polishing removal amount in the 20th cycle was 62 μm, the reduction in the polishing removal amount was about 4%, and the durability during recycling use was very good. I found it.

In the first cycle, the surface condition of the wafer was measured using a minute area measuring device (Talysteel Hobson).
When measured in p), R _max = 6.9 nm / 1.5 mm, which was good. Also, the surface condition at the 20th cycle was almost unchanged.

Example 2 An alkaline colloidal silica solution having an average silica particle diameter of 12 nm and a silica solid content of 30% by weight [Adelite AT-3]
0: Asahi Denka Kogyo Co., Ltd.] was diluted to 5% by weight of silica solids. To 1000 parts by weight of this solution, 150 parts by weight of aminoethylethanolamine (300% by weight based on silica solid content) and CH ₃ COONa as organic water-soluble amines were added.
The procedure of Example 1 was followed, except that 0 parts by weight (40% by weight based on the solid content of silica) was added and the mixture was sufficiently stirred until it became uniform to form an abrasive.

As a result of this test, the polishing removal amount in the first cycle was 72 μm, and the polishing removal amount in the 20th cycle was 68 μm.
The decrease in the amount of polishing removal was about 6%, indicating that the durability during recycling was very good.

The surface condition of the wafer in the first cycle was R _max = 4.2 nm / 1.5 mm, which was good.
Also, the surface condition at the 20th cycle was almost unchanged.

Example 3 An alkaline colloidal silica solution having an average silica particle diameter of 25 nm and a silica solid content of 50% by weight [Adelite AT-5]
0: Asahi Denka Kogyo Co., Ltd.] was diluted to 5% by weight of silica solids. 40 weight To this solution 1000 parts by weight of N as the organic water-soluble amine, N- dibutyl ethanolamine 150 parts by weight (300% by weight with respect to the silica solids) and K ₃ PO ₄ to 20 parts by weight (silica solids %), And the mixture was sufficiently stirred until it became uniform to obtain an abrasive.
According to the method of Example 1.

As a result of this test, the polishing removal amount in the first cycle was 66 μm, and the polishing removal amount in the 20th cycle was 63 μm.
The decrease in the removal amount by polishing was about 5%, and it was found that the durability during recycling was very good.

The surface condition of the wafer in the first cycle was R _max = 5.8 nm / 1.5 mm, which was good.
Also, the surface condition at the 20th cycle was almost unchanged.

Example 4 An alkaline colloidal silica solution having an average silica particle diameter of 25 nm and a silica solid content of 50% by weight [Adelite AT-5]
0: Asahi Denka Kogyo Co., Ltd.] was diluted to 5% by weight of silica solids. A ratio of 150 parts by weight of monoethanolamine (300% by weight based on silica solids) and 20 parts by weight of Na ₂ CO ₃ (40% by weight based on silica solids) as an organic water-soluble amine to 1000 parts by weight of the solution. In the same manner as in Example 1 except that the slurry was sufficiently stirred until it became uniform to obtain an abrasive.

As a result of this test, the polishing removal amount in the first cycle was 70 μm, and the polishing removal amount in the 20th cycle was 68 μm.
The decrease in the removal amount by polishing was about 3%, and it was found that the durability at the time of recycling was very good.

The surface condition of the wafer in the first cycle was R _max = 7.3 nm / 1.5 mm, which was good.
Also, the surface condition at the 20th cycle was almost unchanged.

Example 5 An alkaline colloidal silica solution having an average silica particle diameter of 45 nm and a silica solid content of 50% by weight [Adeleite BT-5
5: Asahi Denka Kogyo Co., Ltd.] was diluted to a silica solid content of 5% by weight. To 1000 parts by weight of this solution, 150 parts by weight of monoethylamine (300% by weight based on silica solids) and 20 parts by weight of NaBO ₃ (40% by weight based on silica solids) were added as organic water-soluble amines. The method of Example 1 was followed except that the slurry was sufficiently stirred until it became uniform.

As a result of this test, the polishing removal amount in the first cycle was 76 μm, and the polishing removal amount in the 20th cycle was 70 μm.
With m, the reduction in the amount of polishing removed was about 8%, indicating that the durability during recycling use was very good.

The surface condition of the wafer in the first cycle was R _max = 9.5 nm / 1.5 mm, which was good.
Also, the surface condition at the 20th cycle was almost unchanged.

Example 6 An alkaline colloidal silica solution having an average silica particle diameter of 45 nm and a silica solid content of 50% by weight [Adeleite BT-5]
5: Asahi Denka Kogyo Co., Ltd.] was diluted to a silica solid content of 5% by weight. To 1,000 parts by weight of this solution, 150 parts by weight of monomethylaminopropylamine (300% by weight based on silica solids) and 20 parts by weight of KHCO ₃ (40% by weight based on silica solids) are added as organic water-soluble amines. And
The method of Example 1 was followed except that the slurry was sufficiently stirred until it became uniform.

As a result of this test, the polishing removal amount in the first cycle was 69 μm, and the polishing removal amount in the 20th cycle was 66 μm.
The decrease in the removal amount of the polishing was about 4%, and it was found that the durability at the time of recycling was very good.

The surface condition of the wafer in the first cycle was Rmax = 6.1 nm / 1.5 mm, which was good.
Also, the surface condition at the 20th cycle was almost unchanged.

Example 7 An alkaline colloidal silica solution having an average silica particle diameter of 45 nm and a silica solid content of 50% by weight [Adeleite BT-5]
5: Asahi Denka Kogyo Co., Ltd.] was diluted to a silica solid content of 5% by weight. To 1,000 parts by weight of this solution, 150 parts by weight of diethylenetriamine (300% by weight based on silica solids) and 20 parts by weight of CHCOONa (40% by weight based on silica solids) are added as organic water-soluble amines to make them uniform. The procedure of Example 1 was followed except that the slurry was sufficiently stirred until the abrasive was obtained.

As a result of this test, the polishing removal amount in the first cycle was 71 μm, and the polishing removal amount in the 20th cycle was 67 μm.
The decrease in the amount of polishing removal was about 6%, indicating that the durability during recycling was very good.

The surface condition of the wafer in the first cycle was R _max = 4.1 nm / 1.5 mm, which was good.
Also, the surface condition at the 20th cycle was almost unchanged.

Example 8 An alkaline colloidal silica solution having an average silica particle diameter of 9 nm and a silica solid content of 30% by weight [Adelite AT-30]
S: Asahi Denka Kogyo Co., Ltd.] was diluted to a silica solid content of 5% by weight. 5 parts by weight of N-methyl-N, N-diethanolamine (10% by weight based on silica solids) and 1 part by weight of Na ₂ CO ₃ (2 parts by weight based on silica solids) % By weight) and thoroughly stirred until uniform to obtain an abrasive.
Method.

As a result of this test, the polishing removal amount in the first cycle was 48 μm, and the polishing removal amount in the 20th cycle was 47 μm.
The decrease in the removal amount by polishing was about 2%, and it was found that the durability at the time of recycling was very good.

The surface condition of the wafer in the first cycle was R _max = 4.9 nm / 1.5 mm, which was good.
Also, the surface condition at the 20th cycle was almost unchanged.

Example 9 An alkaline colloidal silica solution having an average silica particle diameter of 9 nm and a silica solid content of 30% by weight [Adelite AT-30]
S: Asahi Denka Kogyo Co., Ltd.] was diluted to a silica solid content of 5% by weight. To 1000 parts by weight of this solution, 5 parts by weight of organic water-soluble amine (10% by weight based on silica solids) and 1 part by weight of KHCO ₃ (2% by weight based on silica solids) were used. The procedure of Example 1 was followed except that the slurry was added and sufficiently stirred until it became uniform to obtain an abrasive.

As a result of this test, the polishing removal amount in the first cycle was 43 μm, and the polishing removal amount in the 20th cycle was 41 μm.
The decrease in the removal amount by polishing was about 5%, and it was found that the durability during recycling was very good.

The surface condition of the wafer in the first cycle was R _max = 6.0 nm / 1.5 mm, which was good.
Also, the surface condition at the 20th cycle was almost unchanged.

Example 10 An alkaline colloidal silica solution having an average silica particle diameter of 17 nm and a silica solid content of 40% by weight [Adelite AT-4]
0: Asahi Denka Kogyo Co., Ltd.] was diluted to 5% by weight of silica solids. To 1,000 parts by weight of this solution, 5 parts by weight of hydrazine (10% by weight based on silica solids) and 1 part by weight of KH ₂ PO ₄ (2% by weight based on silica solids) were added as organic water-soluble amines. The procedure of Example 1 was followed except that the slurry was stirred until it became uniform.

As a result of this test, the polishing removal amount in the first cycle was 48 μm, and the polishing removal amount in the 20th cycle was 45 μm.
The decrease in the amount of polishing removal was about 6%, indicating that the durability during recycling was very good.

The surface condition of the wafer in the first cycle was R _max = 3.9 nm / 1.5 nm, which was good.
Also, the surface condition at the 20th cycle was almost unchanged.

Example 11 An alkaline colloidal silica solution having an average silica particle diameter of 65 nm and a silica solid content of 50% by weight [Adeleite BT-5
7: Asahi Denka Kogyo Co., Ltd.] was diluted to a silica solid content of 5% by weight. 5 parts by weight of ethylenediamine as an organic water-soluble amine (1 part by weight based on silica solid content)
0% by weight) and 1 part by weight of Na ₂ HPO ₄ (2% by weight based on the solid content of silica), and thoroughly stirred until uniform to obtain an abrasive. According to.

As a result of this test, the polishing removal amount in the first cycle was 44 μm, and the polishing removal amount in the 20th cycle was 41 μm.
The decrease in the removal amount by polishing was about 7%, and it was found that the durability at the time of recycling was very good.

The surface condition of the wafer in the first cycle was R _max = 5.5 nm / 1.5 nm, which was good.
Also, the surface condition at the 20th cycle was almost unchanged.

Comparative Example 1 An alkaline colloidal silica solution having an average silica particle diameter of 12 nm and a silica solid content of 30% by weight [Adelite AT-3]
0: Asahi Denka Kogyo Co., Ltd.] was diluted to 5% by weight of silica solids. To 1000 parts by weight of this solution, 250 parts by weight of aminoethylethanolamine (500% by weight based on the solid content of silica) and CH ₃ COONa as organic water-soluble amine were added.
0 parts by weight (60% by weight based on the solid content of silica) was added, and the mixture was sufficiently stirred until the mixture became uniform to obtain an abrasive. When this abrasive was stored at room temperature, it became thickened in about 10 days, which proved to be poor in stability, and was not suitable for use.

Comparative Example 2 An alkaline colloidal silica solution having an average silica particle diameter of 25 nm and a silica solid content of 50% by weight [Adelite AT-5]
0: Asahi Denka Kogyo Co., Ltd.] was diluted to 5% by weight of silica solids. To 1,000 parts by weight of this solution was added 150 parts by weight of N, N-dibutylethanolamine (200% by weight based on silica solids) as an organic water-soluble amine, and without adding a salt of a weak acid and an alkali metal, The procedure of Example 1 was followed except that the mixture was sufficiently stirred to obtain an abrasive.

As a result of this test, the polishing removal amount in the first cycle was as good as 70 μm, but the polishing removal amount in the 20th cycle was 30 μm, and the reduction in the polishing removal amount was about 57%. Was found to have very poor durability.

[0058] Also, the first cycle of the wafer surface state is R _max = 6.8nm / 1.5mm, but there was good, the surface condition of the 20th cycle is R _max = 15.9nm /
It was 1.5 mm. In addition, this abrasive produced a large amount of sticky gel with the recycling use, and it was very difficult to perform a filtration treatment.

Comparative Example 3 An alkaline colloidal silica solution having an average silica particle diameter of 45 nm and a silica solid content of 50% by weight [Adeleite BT-5
5: Asahi Denka Kogyo Co., Ltd.] was diluted to a silica solid content of 5% by weight. To 1,000 parts by weight of this solution, 2 parts by weight of diethylenetriamine (4% by weight based on silica solids) and 20 parts by weight of CH ₃ COONa (40% by weight based on silica solids) were added as organic water-soluble amines, and the mixture was uniformly mixed. The procedure of Example 1 was followed except that the mixture was sufficiently stirred to obtain an abrasive.

As a result of this test, the polishing removal amount in the first cycle was 21 μm, and the polishing removal amount in the 20th cycle was 20 μm.
The decrease in the removal amount by polishing was about 5%, and it was found that the durability during recycling was very good. However, it was found that the removal amount of polishing was small and not suitable for use.

Comparative Example 4 An alkaline colloidal silica solution having an average silica particle diameter of 65 nm and a silica solid content of 50% by weight [Adeleite BT-5]
7: Asahi Denka Kogyo Co., Ltd.] was diluted to a silica solid content of 5% by weight. 5 parts by weight of ethylenediamine as an organic water-soluble amine (1 part by weight based on silica solid content)
0% by weight) and 0.03% by weight of Na ₂ HPO ₄ (0.06% by weight based on the solid content of silica), and sufficiently stirred until uniform to obtain an abrasive. Method 1 was followed.

As a result of this test, the polishing removal amount in the first cycle was as good as 43 μm, but the polishing removal amount in the 20th cycle was 24 μm, and the reduction in the polishing removal amount was as large as about 47%. The durability during use was found to be very poor.

The surface condition of the wafer at the first cycle was R _max = 5.8 nm / 1.5 mm, which was good. However, the surface condition at the 20th cycle was R _max = 18.0 nm / R.
It was 1.5 mm.

In addition, this processing liquid produced a large amount of sticky gelled substances with recycling, making it extremely difficult to carry out a filtration treatment.

[0065]

The effect of the present invention is that polishing of a silicon wafer using a good silicon wafer polishing agent with a small reduction in polishing efficiency during recycling and a sufficient polishing amount is achieved.
In providing a polishing method .

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Shuichi Tada 7-2-35 Higashiogu, Arakawa-ku, Tokyo Asahi Denka Kogyo Co., Ltd. (72) Inventor Junichi Kuno 7-2-35 Higashiogu, Arakawa-ku, Tokyo Asahi Inside the Denka Kogyo Co., Ltd. (72) Inventor Takayoshi Azumi 7-35, Higashiogu, Arakawa-ku, Tokyo Asahi Denka Kogyo Co., Ltd. (72) Masanori Konishi 7-35, Higashiogu, Arakawa-ku, Tokyo Asahi Denka Kogyo (56) References JP-A-2-158684 (JP, A) JP-A-2-257627 (JP, A) JP-A-62-68276 (JP, A)

Claims (1)

(57) [Claims] 1. An alkaline colloidal silica solution containing silica having an average particle diameter of 7 to 100 nm, an organic water-soluble amine of 5 to 400% by weight based on silica solids, and 0.1 to 50 based on silica solids. Silicon wafer containing, as an essential component, a weight percent salt of a weak acid and an alkali metal
-Polishing and polishing silicon wafers with abrasives
Process of filtering the used silicon wafer abrasive, filtration
Reuse over-processed silicon wafer abrasive
Polishing con-wafer, silicon wafer
Silicon, characterized by recycling abrasives
Wafer polishing method .