JPH04291723A - Polishing agent for silicon wafer - Google Patents

Abstract

PURPOSE:To suppress generation of haze by adding the specified amount of particular anionic surface-active agent to alkali colloidal silica having mean grain size within the particular range. CONSTITUTION:The alkali colloidal silica used preferentially as pH value from 8.5 to 11.0 and also has a mean grain size, for example, of 7 to 100mmu measured by the nitrogen absorption method (BET method). As the anionic surface-active agent, the sulfonic acid salt type, sulfuric acid ester salt type, calboxylic acid salt type and phosphoric acid ester salt type agents are used. The amount of anionic surface-active agent to be added is 1ppm to 1.0wt.% in terms of the effective total component amount of a kind or several kinds of anionic surface-active agent for the solid matter of alkali colloidal silica. Thereby, haze-free silicon wafer can be obtained.

Description

[Detailed description of the invention]

0001

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

0002

[Prior Art and Problems to be Solved by the Invention] The mirror polishing process of silicon wafers for semiconductors includes a lapping process (a lapping process) in which cut strain layers and surface waviness that occur when the silicon ingot is cut into wafers are removed. There is a polishing process (precision polishing process) that finishes the wrapped silicon wafer that has undergone the lapping process to the desired surface precision. In addition, the polishing process is divided into a primary polishing process (primary polishing process) that finishes the surface to a rough level of accuracy, and a final polishing process (final polishing process) that finishes the surface to the desired surface accuracy.In some cases, the primary polishing process The polishing process is divided into two parts and is sometimes referred to as a primary polishing process and a secondary polishing process. The present invention relates to an abrasive for the aforementioned final polishing process.

[0003] The final polishing process refers to the process of finishing a silicon wafer, which has been generally finished to a surface roughness of about 4 to 20 nm through the primary or secondary polishing process, to the desired surface roughness. The polishing process completes the silicon wafer as a semiconductor substrate. In the actual final polishing process, multiple silicon wafers that have undergone the primary polishing process are attached to a polishing block, and appropriate pressure is applied to the soft artificial leather (soft polisher) that is attached to the polishing block on a rotary table. The wafer is brought into close contact with the silicon wafer, and a polishing solution of alkaline colloidal silica or silica powder dispersed in water with a pH of about 8 to 12 is poured over the silicon wafer, and the polishing solution and the silicon wafer undergo a mechanochemical action to polish the silicon wafer.

However, when conventional alkaline colloidal silica polishing liquid is used in the final polishing process, haze (cloudiness) occurs on the silicon wafer surface at the end of the polishing process.
It was in a state where it could not be used as it was.

[0005] Furthermore, if a polishing liquid in which powdered silica is dispersed in any aqueous solution is used for polishing, haze does not occur, but
It tends to cause fine scratches on the silicon wafer surface, and it precipitates if left standing, so it must be constantly stirred, and furthermore, the dispersion process itself is difficult. Ta.

[0006] JP-A-2-125413 describes an anti-fogging device for semiconductor wafers, but it requires special equipment, and the introduction of new equipment increases the burden on the manufacturer, making it impractical. It is true. JP-A-61-209
No. 909 and No. 61-209910 disclose a method for synthesizing colloidal silica for polishing silicon wafers, but the cost is high and furthermore, the prevention of haze, which is the gist of the present invention, is not improved in any way. do not have. Also, JP-A-62-285976, JP-A-1-297487, JP-A-63-272458, JP-A-63-272459,
For the same reason, JP-A-1-177969 and other publications do not have the haze prevention ability for this purpose. Further, although compositions of abrasives for silicon wafers are disclosed in US Pat.

[0007]

[Means for Solving the Problems] As a result of intensive studies to solve the above problems, the present inventors have found that the average particle diameter is 7 to 100 mμ.
A sulfonate type, sulfate ester salt type, carboxylate type, or phosphate ester salt type anionic surfactant is added to the alkaline colloidal silica in an amount of 1 ppm to 1.0% by weight based on the silica solid content contained in the colloidal silica. By doing so, they succeeded in developing an abrasive that can suppress the occurrence of haze without any special treatment, and completed the present invention.

That is, the present invention has an average particle diameter of 7 to 100 mμ.
A sulfonate type, sulfate ester salt type, carboxylate type or phosphate ester salt type anionic surfactant is added to alkaline colloidal silica in an amount of 1 ppm to 1.0% by weight based on the silica solid content contained in the colloidal silica. To provide an abrasive for silicon wafers which does not generate haze.

The alkaline colloidal silica used in the present invention preferably has a pH of 8.5 to 11.0, and has an average particle diameter of 7 to 1, for example, as measured by the nitrogen adsorption method (BET method).
A commercially available product having a diameter of 00 mμ can be used. For example, Adelite AT-30S (Asahi Denka Kogyo Co., Ltd., average particle size 7 to 10 mμ, silica solid content 30% by weight), Adelite AT-30 (Asahi Denka Kogyo Co., Ltd., average particle size 10 to 15 mμ, Silica solid content 3
0% by weight), Adelite AT-40 (Asahi Denka Kogyo Co., Ltd.)
, average particle size 15-20 mμ, silica solid content 40% by weight), Adelite AT-50 (Asahi Denka Kogyo Co., Ltd., average particle size 20-30 mμ, silica solid content 50% by weight),
Adelite BT-55 (Asahi Denka Kogyo Co., Ltd., average particle size 30 to 50 mμ, silica solid content 50% by weight), Adelite BT-57 (Asahi Denka Kogyo Co., Ltd., average particle size 50 to 50%)
70 mμ, silica solid content 50% by weight), Adelite B
T-59 (Asahi Denka Kogyo Co., Ltd., average particle size 70-100)
mμ, silica solid content 50% by weight), etc. are optimal.

[0010] The anionic surfactants that can be used in the present invention include sulfonate types, sulfate ester salt types, carboxylate salt types, and phosphate ester salt types. Among the sulfonate types, alkyl sulfonate salts, alkyl benzene salts, Examples include sulfonates, alkylnaphthalenesulfonates, sulfosuccinates, N-acylsulfonates, and the like. Examples of the sulfate ester salt type include alkyl sulfates, alkyl ether sulfates, alkylaryl ether sulfates, and alkylamide sulfates. Examples of carboxylic acid salts include N-acylamino acid salts, alkyl ether carboxylic acid salts, and acylated peptide salts. Examples of phosphoric acid ester salts include alkyl phosphates, alkyl ether phosphates, and alkylaryl ether phosphates. Note that any counterion may be used, but Na, K, Li, amine, ammonium, etc. are preferable. The amount added is 1 ppm to 1.0% by weight of the total amount of active ingredients of one or more types of anionic surfactants based on the silica solid content of the alkaline colloidal silica. If the amount added is less than 1 ppm, the desired performance will not be achieved, and if it is added in excess of 1.0% by weight, no improvement in performance can be expected, and a slipping phenomenon will occur, making it difficult to polish and process silicon wafers. becomes difficult.

The abrasive for silicon wafers of the present invention is a combination of alkaline colloidal silica and anionic surfactant, with a silica concentration of 0.5 to 20% by weight,
More preferably, it is used diluted with water to a concentration of 1 to 10% by weight for economical reasons, but is not limited thereto.

0012

[Examples] Various examples will be described below, but the present invention is not limited to the following examples.

Example 1 Adelite AT-30S (manufactured by Asahi Denka Kogyo Co., Ltd., average particle size 7 to 10 mμ, silica solid content 30%) was diluted to a silica solid content of 5.0% by weight. To this diluted Adelite AT-30S, sodium lauryl sulfonate (sulfonate type) was added at 2 ppm based on the silica solid content,
The mixture was thoroughly stirred and homogenized to obtain a diluted polishing liquid. This diluted polishing solution was flowed under the conditions described below to polish the primary polished wafer that had undergone the primary polishing process.

Polishing machine: LPH-15 improved machine manufactured by Lap Master Co., Ltd. Polishing machine diameter: 15 inches Processing pressure: 100g/cm2 Processing temperature: 30°C Processing fluid supply amount: 10 liters/hr Processing time: 1 hour Number of sheets processed: 1-sheet polisher: SUPREME RN-H Manufactured by Rodel Nitta Co., Ltd. Perform final polishing under the above conditions, and after finishing,
RCA cleaning was performed in a hydrogen peroxide-ammonia solution at 80° C., being careful not to dry the wafer surface. After washing,
QDR (quick dump cleaning) was performed and drying was performed using a spin dryer. After completion of drying, the reflection of parallel halogen light (ultra-high brightness inspection illumination device U1H-1H, Intec Corporation) was visually measured in a clean bench to observe the occurrence of haze. As a result of the measurement, the obtained silicon wafer was free of haze (haze-free) and was in good condition.

Example 2 Example 1 was followed except that the amount of sodium lauryl sulfonate added was changed to 0.6% by weight based on the silica solid content. The obtained silicon wafer was haze-free and good.

Example 3 The alkaline colloidal silica used was Adelite AT-
50 (Asahi Denka Kogyo Co., Ltd.), average particle size 20-30 mμ
, silica solid content 50%), the anionic surfactant to be added was changed to sodium dodecylbenzenesulfonate (sulfonate type), and the amount added was 3p based on the silica solid content.
Example 1 was followed except that pm was changed. The obtained silicon wafer was haze-free and good.

Example 4 Example 3 was followed except that the amount of sodium dodecylbenzenesulfonate added was changed to 0.8% by weight based on the silica solid content. The obtained silicon wafer was haze-free and good.

Example 5 The alkaline colloidal silica used was Adelite BT-
59 (Asahi Denka Kogyo Co., Ltd.), average particle size 70-100 mμ
, silica solid content 50%), silica concentration 2.0
% by weight. The procedure of Example 1 was followed except that the anionic surfactant added was changed to sodium dodecylnaphthalene sulfonate (sulfonate type) and the amount added was changed to 10 ppm based on the silica solid content. The obtained silicon wafer was haze-free and good.

Example 6 Example 5 was followed except that the amount of sodium dodecylnaphthalene sulfonate added was changed to 0.9% by weight based on the silica solid content. The obtained silicon wafer was haze-free and good.

Example 7 The alkaline colloidal silica used was Adelite AT-
40 (Asahi Denka Kogyo Co., Ltd.), average particle size 15-20 mμ
, silica solid content 40%), silica concentration 8.0
% by weight. The procedure of Example 1 was followed except that the anionic surfactant added was changed to sodium lauryl sulfate (sulfate ester salt type) and the amount added was changed to 5 ppm based on the silica solid content. The obtained silicon wafer was haze-free and good.

Example 8 Example 7 was followed except that the amount of sodium lauryl sulfate added was changed to 1.0% by weight based on the silica solid content. The obtained silicon wafer was haze-free and good.

Example 9 The alkaline colloidal silica used was Adelite AT-
50 (Asahi Denka Kogyo Co., Ltd.), average particle size 20-30 mμ
, silica solid content 50%), silica concentration 3.0
% by weight. The procedure of Example 1 was followed, except that the anionic surfactant to be added was changed to sodium sulfate (sulfate ester salt type), which is an adduct of Dovanol with 3 mol of ethylene oxide, and the amount added was changed to 10 ppm based on the silica solid content. The obtained silicon wafer was haze-free and good.

Example 10 The amount of sodium sulfate added as an adduct of 3 mol of ethylene oxide to Dovanol was 0.8 based on the silica solid content.
Example 9 was followed except that the weight percentage was changed. The obtained silicon wafer was haze-free and good.

Example 11 The alkaline colloidal silica used was Adelite BT-
55 (Asahi Denka Kogyo Co., Ltd.), average particle size 30-50 mμ
, silica solid content 50%), silica concentration 4.0
% by weight. Example 1 was followed except that the anionic surfactant added was changed to potassium lauryl ether carboxylate (carboxylate type) and the amount added was changed to 4 ppm based on the silica solid content. The obtained silicon wafer was haze-free and good.

Example 12 Example 1 except that the amount of potassium lauryl ether carboxylate added was changed to 0.7% by weight based on the silica solid content.
I followed 1. The final polished silicon wafer obtained was haze-free and of good quality.

Example 13 The alkaline colloidal silica used was Adelite AT-
30 (Asahi Denka Kogyo Co., Ltd.), average particle size 10-15 mμ
, silica solid content 30%), and the silica concentration was 7.0.
% by weight. The anionic surfactant to be added is
Example 1 was followed, except that the amount of sodium phosphate (phosphate ester salt type) of the ethylhexyl ethylene oxide adduct was changed to 10 ppm based on the silica solid content. The obtained silicon wafer was haze-free and good.

Example 14 Example 13 was followed except that the amount of sodium phosphate added to the 2-ethylhexylethylene oxide adduct was changed to 0.8% by weight based on the silica solid content. The obtained silicon wafer was haze-free and good.

Comparative Example 1 Adelite AT-50 (manufactured by Asahi Denka Kogyo Co., Ltd., average particle size 20-30 mμ, silica solid content 50%) was diluted to a silica solid content of 5.0% by weight. The conditions of Example 1 were followed except that this diluted working fluid was used directly for polishing. The obtained silicon wafer was defective due to haze.

Comparative Example 2 The alkaline colloidal silica used was Adelite AT-
30S (Asahi Denka Kogyo Co., Ltd., average particle size 7-10 mμ)
, silica solid content 30%), silica solid content 5.0
% by weight. The conditions of Example 1 were followed except that this diluted working fluid was used directly for polishing. The obtained silicon wafer was defective due to haze.

Comparative Example 3 The alkaline colloidal silica used was Adelite BT-
59 (Asahi Denka Kogyo Co., Ltd.), average particle size 70-100 mμ
, silica solid content 50%), silica concentration 2.0
% by weight. The conditions of Example 1 were followed except that this diluted working fluid was used directly for polishing. The obtained silicon wafer was defective due to haze.

Comparative Example 4 Adelite AT-30S (manufactured by Asahi Denka Kogyo Co., Ltd., average particle size 7 to 10 mμ, silica solid content 30%) was diluted to a silica solid content of 10% by weight. This diluted Adelite AT
-30S contains sodium lauryl sulfonate (sulfonate type) at 1.1% of the silica solid content in terms of active ingredient.
Example 1 except that % by weight was added and homogenized by stirring well.
I followed. Although there was no haze on the silicon wafer after polishing, it was found that the same polishing arc as that during the primary polishing remained, and a slipping phenomenon appeared, indicating that the processing was not progressing. The obtained silicon wafer was defective for the above reasons.

Comparative Example 5 Example 1 was followed except that the amount of sodium lauryl sulfonate (sulfonate salt type) was changed to 0.5 ppm based on the silica solid content in terms of active ingredient. The obtained silicon wafer was defective with slight haze.

Comparative Example 6 Adelite AT-40 (manufactured by Asahi Denka Kogyo Co., Ltd., average particle size 15-20 mμ, silica solid content 40%) was diluted to a silica solid content of 6.0% by weight. The procedure of Example 7 was repeated, except that sodium lauryl sulfate (sulfate ester salt type) was added to the diluted Adelite AT-40 in an amount of 1.2% by weight based on the silica solid content in terms of active ingredient, and the mixture was thoroughly stirred and homogenized. I obeyed. Although there was no haze on the silicon wafer after polishing, it was found that the same polishing arc as that during the primary polishing remained, and a slipping phenomenon appeared, indicating that the processing was not progressing. The obtained silicon wafer was defective for the above reasons.

Comparative Example 7 Example 7 was followed except that sodium lauryl sulfate (sulfonate type) was changed to 0.8 ppm based on the silica solid content in terms of active ingredient. The obtained silicon wafer was defective with slight haze.

Comparative Example 8 Adelite BT-55 (manufactured by Asahi Denka Kogyo Co., Ltd., average particle size 30-50 mμ, silica solid content 50%) was diluted to a silica solid content of 4.0% by weight. Potassium lauryl ether carboxylate (carboxylate salt type) was added to the diluted Adelite BT-55 in an amount of 1.1% by weight based on the silica solid content in terms of active ingredient, and the mixture was homogenized by stirring well.
Example 11 was followed. Although there was no haze on the silicon wafer after polishing, it was found that the same polishing arc as that during the primary polishing remained, and a slipping phenomenon appeared, indicating that the processing was not progressing. The obtained silicon wafer was defective for the above reasons.

Comparative Example 9 Potassium lauryl ether carboxylate (carboxylate type) was added in an amount of 0.9 ppm based on the silica solid content in terms of active ingredient.
Example 11 was followed except for the following changes. The obtained silicon wafer was defective with slight haze.

[0037]

Effect of the invention: Adding a sulfonate type, sulfate ester salt type, carboxylate type or phosphate ester salt type anionic surfactant to alkaline colloidal silica with an average particle size of 7 to 100 mμ, the silica solid content contained in the colloidal silica When an abrasive containing 1 ppm to 1.0% by weight of abrasives is used for final polishing of silicon wafers, haze can be easily removed using the same method as in conventional polishing processes, without any special operations or modification of the equipment. We were able to obtain free silicon wafers.

Claims (1)

[Claims] Claim 1: A sulfonate type, sulfate ester salt type, carboxylate type or phosphate ester salt type anionic surfactant is added to alkaline colloidal silica having an average particle diameter of 7 to 100 mμ, and the silica solid content contained in the colloidal silica is An abrasive for silicon wafers, which is added in an amount of 1 ppm to 1.0% by weight.