JPH04313224A - Silicon-wafer abrasives - Google Patents

Abstract

PURPOSE:To provide silicon-wafer abrasives whose drop in a polishing efficiency is small even when they are recycled and whose polishing amount is sufficiently good at a primary polishing process to manufacture a silicon wafer. CONSTITUTION:Silicon-wafer abrasives by this invention are featured by containing the following as essential components: an alkali colloidal silica solution which contains silica whose average particle size is at 7 to 100nm; 5 to 400wt.% of an organic water-soluble amine with reference to silica solid portion; and 0.1 to 50wt.% of a weak acid and an alkali metal salt with reference to the silica solid portion.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an abrasive for silicon wafers used in semiconductor manufacturing processes.

[0002] The mirror polishing process of silicon wafers for semiconductors includes a lapping process to remove cutting strain layers and undulations that occur when wafers are cut from a silicon single crystal ingot, and a silicon wafer that has undergone the lapping process. There is a polishing process that polishes and finishes the surface to a certain level of precision.The polishing process is divided into a primary polishing process called rough polishing and a final polishing process called precision polishing.In some cases, the primary polishing process is It is further divided into two steps, which are called primary and secondary polishing steps.

[0003] In detail, the present invention relates to the above-mentioned primary polishing process or primary and secondary polishing processes in which the primary polishing process is further divided into two processes (hereinafter these are collectively referred to simply as the primary polishing process). Regarding abrasives for use.

0004

[Prior Art] In the primary polishing process, a plurality of wrapped silicon wafers are attached to a polishing block, and the polishing block is placed on a rotary table with artificial leather (
Apply appropriate pressure to the polisher) to adjust the pH to 9-12.
The process progresses by adding a degree of alkaline colloidal silica or silica powder polishing liquid dispersed in water, which causes a mechanochemical effect between the polishing liquid and the silicon wafer, but the polishing agent used here is usually recycled to reduce costs. Commonly used.

[0005]

[Problems to be Solved by the Invention] However, when conventional abrasives are used for this recycling, the polishing efficiency for silicon wafers is significantly deteriorated, and furthermore,
This method has the disadvantage that the precision of the surface of the finished silicon wafer deteriorates, and as a result, it is difficult to control the process for manufacturing the silicon wafer.

For example, US Pat. No. 3,170,273 describes the use of colloidal silica and silica gel to polish silicon wafers. Further, US Pat. No. 4,169,337 discloses a method with improved polishing efficiency. Further, Japanese Patent Application Laid-Open No. 58-225177 discloses an improved method by adding quaternary ammonium and its salt to the polishing liquid used. Further, JP-A-62-30333 discloses a highly efficient silicon wafer polishing method by adding piperazine to alkaline colloidal silica.

However, the above methods have a common problem that although the initial polishing efficiency of the polishing liquid is good, the polishing efficiency deteriorates significantly when the polishing liquid is recycled and it is difficult to manage the polishing process. There is. Therefore, an object of the present invention is to minimize the decrease in polishing efficiency during recycled use.
It is an object of the present invention to provide a good silicon wafer polishing agent with a sufficient polishing amount.

[0008]

[Means for Solving the Problems] The silicon wafer polishing agent according to the present invention is an alkaline colloidal silica solution containing silica with an average particle size of 7 to 100 nm, and an organic water-soluble solution of 5 to 400% by weight based on the silica solid content. It is characterized by containing 0.1 to 50% by weight of a weak acid and an alkali metal salt as essential components based on the amine and silica solid content.

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 powdered silica was thoroughly washed with distilled water to remove salt, and dried at 105°C.
The specific surface area obtained by the nitrogen adsorption method is substituted into the following formula to determine the average particle diameter.

[Equation 1] Average particle diameter (nm) = 6 x 103/[specific surface area (m2/g) x density of amorphous silica (g/cm3)]

[
[0010] The alkaline colloidal silica solution used in the present invention has an average particle size of silica in the solution of 7 to 100.
Any material can be used as long as it is nm,
Commercially available products can also be used.

For example, Adelite AT-30S [Asahi Denka Kogyo Co., Ltd., average particle diameter 8.5±1.5 nm: silica solid content 30% by weight], Adelite AT-30 [Asahi Denka Kogyo Co., Ltd., average particle diameter 12. 5±2.5nm: Silica solid content 30
weight%], Adelite 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 solid content 50% by weight], Adelite BT-55 [Asahi Denka Kogyo Co., Ltd. average particle diameter 40 ± 1
0 nm: Silica solid content 50% by weight], Adelite BT-
57 [Asahi Denka Kogyo Co., Ltd., average particle diameter 60 ± 10 nm: silica solid content 50% by weight], Adelite BT-59 [Asahi Denka Kogyo Co., Ltd., average particle diameter 85 ± 15 nm: silica solid content 50% by weight], etc. Can be used.

The average particle diameter of 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 will deteriorate, and if the average particle size exceeds the above range, it will precipitate if left to stand, and it will be necessary to perform redispersion treatment before use. workability deteriorates.

[0013] Furthermore, the silica in the alkaline colloidal silica solution may have an average particle size within the above range,
Depending on the form of particle size distribution, the particle size of each silica may exceed the above range.

[0014] The organic water-soluble amine used in the present invention can be any organic amine that dissolves in water and exhibits alkalinity, but preferably a straight chain organic amine having 1 to 6 nitrogen atoms. The amine is preferably a branched, branched or cyclic amine. Specifically, for example, N,N-diethylethanolamine, N,N-dimethylethanolamine, aminoethylethanolamine, N-methyl-N,
N-diethanolamine, N,N-dibutylethanolamine, N-methylethanolamine, monoethanolamine, diethanolamine, and the alkylamine include 3,3'-diaminodipropylamine, iminobispropylamine, monoethylamine, diethylamine, 3
-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, and α-amino-ε-caprolactam.

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

The amount of the organic water-soluble amine added is 5 to 400% by weight, preferably 50 to 350% by weight, based on the solid content of the silica. If the amount of organic water-soluble amine added is less than the above amount, the polishing amount will be small and the efficiency will be poor, and if it is added in excess of the above amount, no improvement in polishing efficiency can be expected, and the surface precision of the finished silicon wafer will be reduced. The stability of the alkaline colloidal silica also deteriorates rapidly.

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. As a component, C
O32-, PO43-, HCO3-, carboxylic acid (R-
COO-, R=H, CH3, C2H5), BO33-,
Examples include BO3-, HPO42-, HPO4-, and particularly preferred are salts of either sodium or potassium and CO32-, PO43-, or HCO3-.

The amount of the weak acid and alkali metal salt added is 0.1 to 50% by weight, preferably 1 to 4% by weight based on the solid content of the silica.
It is 5% by weight. If the amount of weak acid and alkali metal salt added is less than the above amount based on the silica solid content, the recycling performance aimed at by the present invention will be insufficient, and if more than 50% by weight is added, the stability of the alkaline colloidal silica solution will be affected. This is inappropriate as it will significantly worsen the condition.

Furthermore, the silicon wafer polishing agent 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, and even if any one of them is missing, the desired performance will not be achieved. You won't be able to perform well.

[0020]

[Examples] The present invention will be further explained with reference to Examples below, but the present invention is not limited thereto. Example 1 An alkaline colloidal silica solution with an average silica particle diameter of 25 nm and a silica solid content of 30% by weight [Adelite AT-3
0: manufactured by Asahi Denka Kogyo Co., Ltd.] was diluted to have a silica solid content of 5% by weight. 150 parts by weight of N,N-dimethylethanolamine as an organic water-soluble amine (300% by weight based on the solid content of silica) and K2CO3 were added to 1000 parts by weight of this solution.
was added at a ratio of 20 parts by weight (40% by weight based on the solid content of silica) and sufficiently stirred until it became uniform to obtain an abrasive.

A silicon wafer was polished using this polishing agent under the following conditions. Polishing machine: Lapmaster LPH-15
Improved polishing disk diameter: 15 inches Polishing disk rotation speed: 70 rpm Silicon wafer: 4 inches in diameter (100) P type CZ method polishing pressure: 400 g/cm2 Polishing temperature: 40°C Polishing agent supply amount: 10 liters/hour Polishing time: Number of pieces polished per hour: 2 pieces

The used abrasive was filtered through a paper filter with a pore size of 6 μm and reused. The process from polishing to filtration was one cycle, and the polishing agent was recycled for a total of 20 cycles.

The amount removed by polishing the silicon wafer (the amount of decrease in the thickness of the silicon wafer) per cycle was measured to examine changes in polishing efficiency. As a result of this test, the amount removed by polishing in the first cycle was 65 μm, and the amount removed by polishing in the 20th cycle was 62 μm, and the reduction in the amount removed by polishing was about 4%.
It was found that the durability during recycled use is very good.

The wafer surface condition in the first cycle was measured using a minute area measuring device (Tal) made by Rank Taylor Hobson.
Rmax=6.9nm/
It was 1.5 mm, which was good. Furthermore, there was almost no change in the surface condition at the 20th cycle.

Example 2 An alkaline colloidal silica solution with an average silica particle diameter of 12 nm and a silica solid content of 30% by weight [Adelite AT-3
0: manufactured by Asahi Denka Kogyo Co., Ltd.] was diluted to have a silica solid content of 5% by weight. To 1000 parts by weight of this solution, 150 parts by weight of aminoethylethanolamine (300% by weight based on the silica solid content) as an organic water-soluble amine and CH3COONa were added.
The method of Example 1 was followed except that 20 parts by weight (40% by weight based on the solid content of silica) were added and thoroughly stirred until uniform to obtain a polishing agent.

As a result of this test, the amount removed by polishing in the first cycle was 72 μm, and the amount removed by polishing in the 20th cycle was 68 μm.
The reduction in the amount removed by polishing was about 6%, and it was found that the durability during recycling was very good.

The wafer surface condition in the first cycle was Rmax=4.2 nm/1.5 mm, which was good. Furthermore, there was almost no change in the surface condition at the 20th cycle.

Example 3 An alkaline colloidal silica solution with an average silica particle diameter of 25 nm and a silica solid content of 50% by weight [Adelite AT-5
0: manufactured by Asahi Denka Kogyo Co., Ltd.] was diluted to have a silica solid content of 5% by weight. To 1000 parts by weight of this solution was added 150 parts by weight of N,N-dibutylethanolamine as an organic water-soluble amine (
300% by weight based on silica solid content) and 20 parts by weight (40% by weight based on silica solid content) of K3PO4 were added and sufficiently stirred until uniform to obtain a polishing agent. The method of Example 1 was followed.

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

The wafer surface condition in the first cycle was Rmax=5.8 nm/1.5 mm, which was good. Furthermore, there was almost no change in the surface condition at the 20th cycle.

Example 4 An alkaline colloidal silica solution with an average silica particle diameter of 25 nm and a silica solid content of 50% by weight [Adelite AT-5]
0: manufactured by Asahi Denka Kogyo Co., Ltd.] was diluted to have a silica solid content of 5% by weight. To 1000 parts by weight of this solution, 150 parts by weight of monoethanolamine (300% by weight based on the silica solid content) as an organic water-soluble amine and 20 parts by weight (40% by weight based on the silica solid content) were added. ,
The method of Example 1 was followed except that the abrasive was sufficiently stirred until uniform.

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

The wafer surface condition in the first cycle was Rmax=7.3 nm/1.5 mm, which was good. Furthermore, there was almost no change in the surface condition at the 20th cycle.

Example 5 An alkaline colloidal silica solution with an average silica particle diameter of 45 nm and a silica solid content of 50% by weight [Adelite BT-5]
5: manufactured by Asahi Denka Kogyo Co., Ltd.] was diluted to have 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 the silica solid content) as an organic water-soluble amine and 20 parts by weight (40% by weight based on the silica solid content) were added, The method of Example 1 was followed except that the abrasive was sufficiently stirred until uniform.

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

The wafer surface condition in the first cycle was Rmax=9.5 nm/1.5 mm, which was good. Furthermore, there was almost no change in the surface condition at the 20th cycle.

Example 6 An alkaline colloidal silica solution with an average silica particle diameter of 45 nm and a silica solid content of 50% by weight [Adelite BT-5]
5: manufactured by Asahi Denka Kogyo Co., Ltd.] was diluted to have a silica solid content of 5% by weight. To 1000 parts by weight of this solution, 150 parts by weight of monomethylaminopropylamine (300% by weight based on the silica solid content) as an organic water-soluble amine and KHCO320 were added.
The method of Example 1 was followed, except that parts by weight (40% by weight based on the silica solid content) were added and thoroughly stirred until uniform to obtain a polishing agent.

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

The wafer surface condition in the first cycle was Rmax=6.1 nm/1.5 mm, which was good. Furthermore, there was almost no change in the surface condition at the 20th cycle.

Example 7 An alkaline colloidal silica solution with an average silica particle diameter of 45 nm and a silica solid content of 50% by weight [Adelite BT-5]
5: manufactured by Asahi Denka Kogyo Co., Ltd.] was diluted to have a silica solid content of 5% by weight. To 1000 parts by weight of this solution, 150 parts by weight of diethylenetriamine (300% by weight based on the solid content of silica) and 20 parts by weight of CHCOONa (40% by weight based on the solid content of silica) were added as an organic water-soluble amine,
The method of Example 1 was followed except that the abrasive was sufficiently stirred until uniform.

As a result of this test, the amount removed by polishing in the first cycle was 71 μm, and the amount removed by polishing in the 20th cycle was 67 μm.
The reduction in the amount removed by polishing was about 6%, and it was found that the durability during recycling was very good.

The wafer surface condition in the first cycle was Rmax=4.1 nm/1.5 mm, which was good. Furthermore, there was almost no change in the surface condition at the 20th cycle.

Example 8 An alkaline colloidal silica solution with an average silica particle size of 9 nm and a silica solid content of 30% by weight [Adelite AT-30
S: manufactured by Asahi Denka Kogyo Co., Ltd.] was diluted to have a silica solid content of 5% by weight. To 1000 parts by weight of this solution, 5 parts by weight of N-methyl-N,N-diethanolamine (10% by weight based on the silica solid content) as an organic water-soluble amine and Na2CO3
The method of Example 1 was followed except that 1 part by weight (2% by weight based on the silica solid content) was added and thoroughly stirred until uniform to obtain a polishing agent.

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

The wafer surface condition in the first cycle was Rmax=4.9 nm/1.5 mm, which was good. Furthermore, there was almost no change in the surface condition at the 20th cycle.

Example 9 An alkaline colloidal silica solution with an average silica particle size of 9 nm and a silica solid content of 30% by weight [Adelite AT-30
S: manufactured by Asahi Denka Kogyo Co., Ltd.] was diluted to have a silica solid content of 5% by weight. To 1000 parts by weight of this solution were added 5 parts by weight of N-methylethanolamine (10% by weight based on the silica solid content) as an organic water-soluble amine and 31 parts by weight KHCO (2% by weight based on the silica solid content). The method of Example 1 was followed except that the abrasive was sufficiently stirred until uniform.

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

The wafer surface condition in the first cycle was Rmax=6.0 nm/1.5 mm, which was good. Furthermore, there was almost no change in the surface condition at the 20th cycle.

Example 10 An alkaline colloidal silica solution with an average silica particle size of 17 nm and a silica solid content of 40% by weight [Adelite AT-4
0: manufactured by Asahi Denka Kogyo Co., Ltd.] was diluted to have a silica solid content of 5% by weight. To 1000 parts by weight of this solution, 5 parts by weight of hydrazine (10% by weight based on the solid content of silica) and 1 part by weight of KH2PO4 (2% by weight based on the solid content of silica) are added as organic water-soluble amines, and the mixture is made uniform. The method of Example 1 was followed except that the abrasive was prepared by stirring until it reached 100 mL.

As a result of this test, the amount removed by polishing in the first cycle was 48 μm, and the amount removed by polishing in the 20th cycle was 45 μm.
The reduction in the amount removed by polishing was about 6%, and it was found that the durability during recycling was very good.

The wafer surface condition in the first cycle was Rmax=3.9 nm/1.5 nm, which was good. Furthermore, there was almost no change in the surface condition at the 20th cycle.

Example 11 Alkaline colloidal silica solution [Adelite BT-5] having an average silica particle diameter of 65 nm and a silica solid content of 50% by weight.
7: manufactured by Asahi Denka Kogyo Co., Ltd.] was diluted to have a silica solid content of 5% by weight. To 1000 parts by weight of this solution, 5 parts by weight of ethylenediamine (10% by weight based on the solid content of silica) and 41 parts by weight of Na2HPO (2% by weight based on the solid content of silica) are added as organic water-soluble amines, and the mixture becomes uniform. The method of Example 1 was followed except that the abrasive was prepared by thoroughly stirring the mixture.

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

The wafer surface condition in the first cycle was Rmax=5.5 nm/1.5 nm, which was good. Furthermore, there was almost no change in the surface condition at the 20th cycle.

Comparative Example 1 An alkaline colloidal silica solution with an average silica particle diameter of 12 nm and a silica solid content of 30% by weight [Adelite AT-3
0: manufactured by Asahi Denka Kogyo Co., Ltd.] was diluted to have a silica solid content of 5% by weight. To 1000 parts by weight of this solution, 250 parts by weight of aminoethylethanolamine (500% by weight based on the silica solid content) as an organic water-soluble amine and CH3COONa were added.
was added at a ratio of 30 parts by weight (60% by weight based on the solid content of silica) and thoroughly stirred until uniform, thereby preparing an abrasive. When this abrasive was stored at room temperature, approximately 1
It became viscous in 0 days, indicating poor stability.
It was not suitable for use.

Comparative Example 2 An alkaline colloidal silica solution with an average silica particle diameter of 25 nm and a silica solid content of 50% by weight [Adelite AT-5]
0: manufactured by Asahi Denka Kogyo Co., Ltd.] was diluted to have a silica solid content of 5% by weight. To 1000 parts by weight of this solution was added 150 parts by weight of N,N-dibutylethanolamine as an organic water-soluble amine (
200% by weight based on the solid content of silica,
The method of Example 1 was followed except that a weak acid and an alkali metal salt were not added and the polishing agent was sufficiently stirred until uniform.

As a result of this test, the amount removed by polishing in the first cycle was 70 μm, which was good, but the amount removed by polishing in the 20th cycle was 30 μm, and the reduction in the amount removed by polishing was about 57%. The durability was found to be very poor.

The wafer surface condition in the first cycle was Rmax=6.8 nm/1.5 mm, which was good, but the surface condition in the 20th cycle was Rmax=15.9.
nm/1.5 mm. Further, when this abrasive is recycled, a large amount of sticky gelled material is generated, making it extremely difficult to filter.

Comparative Example 3 An alkaline colloidal silica solution with an average silica particle diameter of 45 nm and a silica solid content of 50% by weight [Adelite BT-5]
5: manufactured by Asahi Denka Kogyo Co., Ltd.] was diluted to have a silica solid content of 5% by weight. To 1000 parts by weight of this solution, 2 parts by weight of diethylenetriamine (4% by weight based on the solid content of silica) and 20 parts by weight of CH3COONa (40% by weight based on the solid content of silica) are added as organic water-soluble amines, and the mixture becomes uniform. The method of Example 1 was followed except that the abrasive was prepared by thoroughly stirring the mixture.

As a result of this test, the amount removed by polishing in the first cycle was 21 μm, and the amount removed by polishing in the 20th cycle was 20 μm.
The reduction in the amount removed by polishing was about 5%, and it was found that the durability during recycling was very good. However, it was found that the amount removed by polishing was small, making it unsuitable for use.

Comparative Example 4 Alkaline colloidal silica solution [Adelite BT-5] having an average silica particle diameter of 65 nm and a silica solid content of 50% by weight.
7: manufactured by Asahi Denka Kogyo Co., Ltd.] was diluted to have a silica solid content of 5% by weight. To 1000 parts by weight of this solution were added 5 parts by weight of ethylenediamine (10% by weight based on the solid content of silica) and 40.03 parts by weight of Na2HPO (0.06% by weight based on the solid content of silica) as organic water-soluble amines. , Example 1 except that the polishing agent was sufficiently stirred until uniform.
According to the method of

As a result of this test, the amount removed by polishing in the first cycle was 43 μm, which was good, but the amount removed by polishing in the 20th cycle was 24 μm, and the reduction in the amount removed by polishing was very large, about 47%. It was found that the durability during use was very poor.

The wafer surface condition in the first cycle was Rmax=5.8 nm/1.5 mm, which was good, but the surface condition in the 20th cycle was Rmax=18.0.
nm/1.5 mm.

[0064] Furthermore, when this processing liquid was recycled, a large amount of sticky gelled material was generated, making it extremely difficult to filter it.

[0065]

The effect of the present invention is to provide a good silicon wafer polishing slurry that exhibits little drop in polishing efficiency during recycled use and has a sufficient polishing amount.

Claims (1)

[Claims] Claim 1. An alkaline colloidal silica solution containing silica with an average particle size of 7 to 100 nm, an organic water-soluble amine in an amount of 5 to 400% by weight based on the silica solid content, and 0.1 to 50% by weight based on the silica solid content. A silicon wafer polishing agent characterized by containing % by weight of a weak acid and an alkali metal salt as essential components.