JP3435698B2 - Cleaning liquid for semiconductor substrates - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cleaning liquid for semiconductor substrates. More specifically, it relates to an improved cleaning solution for cleaning a semiconductor substrate with a hydrogen peroxide-based cleaning solution.

[0002]

2. Description of the Related Art In a semiconductor element manufacturing process, a semiconductor substrate such as a silicon wafer is subjected to chemical cleaning for removing contaminants such as metals, organic substances and fine particles adhering to the surface. A cleaning solution containing hydrogen peroxide as a main component is often used in this cleaning solution, and for example, a mixed aqueous solution of hydrochloric acid and hydrogen peroxide, a mixed aqueous solution of sulfuric acid and hydrogen peroxide, a mixed aqueous solution of hydrofluoric acid and hydrogen peroxide, A mixed aqueous solution of ammonia and hydrogen peroxide is known.

The chemicals used in the cleaning liquid naturally need to be highly purified, and the metal impurities are usually controlled to 1 ppb or less. However, even if cleaning is performed using such highly purified chemicals, in reality, there is contamination from the environment, contamination from containers, etc., and reattachment contamination of the metal removed from the substrate, etc. It was unavoidable that a small amount of particles would be attached. The problematic metals are heavy metals such as iron, copper and nickel, and their adhesion changes the minority carrier lifetime and causes lattice defects in the substrate, which greatly affects the electrical properties of the semiconductor device. In particular, iron is a serious problem in that it adheres to the substrate in a basic cleaning solution such as a mixed aqueous solution of ammonia and hydrogen peroxide.
Although the amount of metal adhered decreases with an acidic cleaning liquid, copper still tends to adhere in a mixed aqueous solution of hydrofluoric acid and hydrogen peroxide, which poses a problem.

As described above, since the trace amount of metal attached to the surface of the substrate adversely affects the electrical properties of the semiconductor element, it is necessary to reduce the amount as much as possible. It has been pointed out that it is necessary to keep the value of 1 × 10 ¹⁰ atoms / cm ² or less, that is, below the lower limit of detection of a total reflection X-ray fluorescence analyzer, which is widely used as a method for analyzing the amount of deposited metal.

An attempt to reduce the amount of these metal impurities deposited by adding an additive to a hydrogen peroxide-based cleaning liquid is found in German Laid-Open Patent No. 3822350, in which a chelating agent ethylenediaminetetracarboxylic acid (EDTA) is used. ) Is proposed. However, the addition of EDTA had practically no effect. On the other hand, the present inventors have found that a phosphonic acid-based chelating agent is effective in suppressing metal adhesion, and have previously proposed it. The addition of the phosphonic acid-based chelating agent markedly reduced the amount of adhered metal and greatly improved the yield of semiconductor device production. However, even with the addition of the phosphonic acid-based chelating agent, the amount of metal deposited on the substrate was 1 ×.
Below 10 ¹⁰ atoms / cm ² has not been achieved, and more improved measures have been desired.

[0006]

SUMMARY OF THE INVENTION The object of the present invention is to solve the above-mentioned problems, and the amount of metal deposited on the substrate surface after cleaning is 1 ×.
It is to provide a new hydrogen peroxide-based semiconductor substrate cleaning liquid having a concentration of 10 ¹⁰ atoms / cm ² or less.

[0007]

Means for Solving the Problems As a result of intensive studies to achieve the above object, the present inventors have found that, in addition to a phosphonic acid-based chelating agent, an interface for improving the wettability of a cleaning liquid to the substrate surface. The inventors have found that the amount of metal deposited on the substrate surface can be reduced to 1 × 10 ¹⁰ atoms / cm ² or less by adding an activator, and the present invention has been completed. That is, the present invention is a semiconductor substrate cleaning liquid characterized by adding a phosphonic acid-based chelating agent and a surfactant to an acidic or basic hydrogen peroxide cleaning liquid.

The phosphonic acid type chelating agent used in the present invention is not particularly limited as long as it is a chelating agent having at least two phosphonic acid groups, and typical examples thereof include aminotri (methylenephosphonic acid) and 1-hydroxyethylidene. -1,1-diphosphonic acid, ethylenediaminetetra (methylenephosphonic acid), hexamethylenediaminetetra (methylenephosphonic acid), propylenediaminetetra (methylenephosphonic acid), diethylenetriaminepenta (methylenephosphonic acid), triethylenetetraminehexa (methylenephosphonic acid) Acid), triaminotriethylamine hexa (methylenephosphonic acid), trans-1,2-
Examples thereof include cyclohexanediaminetetra (methylenephosphonic acid), glycoletherdiaminetetra (methylenephosphonic acid), and tetraethylenepentaminehepta (methylenephosphonic acid). Among these, particularly preferable phosphonic acid-based chelating agents include ethylenediaminetetra (methylenephosphonic acid) and diethylenetriaminepenta (methylenephosphonic acid). These chelating agents used in the present invention are preferably used in the form of free acid, but when the solubility is insufficient, they may be used in the form of salt such as ammonium salt.

The addition amount of the phosphonic acid type chelating agent is not particularly limited, but is usually 1 ppb to 1000 with respect to the total amount of the cleaning liquid.
It is added at a concentration of ppm. As for the addition method, the cleaning liquid may be added after preparation, or may be added in advance to hydrogen peroxide, water, ammonia, organic amine, hydrochloric acid, sulfuric acid, hydrofluoric acid, etc., and then mixed to prepare them. Is also good.

The surfactants used in the present invention include sulfonic acid type surfactants, sulfuric acid ester type surfactants, phosphoric acid ester type surfactants, fatty acid type surfactants, and polycarboxylic acid type surfactants. Such as anionic surfactants, amine surfactants, quaternary ammonium salt type surfactants and other cationic surfactants, ethylene oxide addition type surfactants, ethylene oxide propylene oxide copolymer type surfactants, Any nonionic surfactant such as glycerin ester type surfactant can be used. Further, a fluorine-based surfactant obtained by partially fluorinating these may be used. Among these, sulfonic acid type surfactants, polycarboxylic acid type surfactants, and ethylene oxide addition type surfactants are preferable. Further, any water-soluble organic additive that improves the wettability of the cleaning liquid on the substrate surface can be used as the surfactant of the present invention.

Examples of water-soluble organic additives which can be used as these surfactants include alcohols such as ethanol, isopropanol, triethylene glycol monomethyl ether and triethylene glycol monoethyl ether, ethylene glycol, propylene glycol and the like. Glycols, carboxylic acids such as acetic acid, propionic acid, and enanthate, hydroxycarboxylic acids such as glycolic acid, tartaric acid, and citric acid, and polyhydric alcohols such as glycerin, sorbit, and polyvinyl alcohol can be used.

The amount of these surfactants added is not particularly limited, but is added so that the surface tension of the cleaning liquid is 60 dyne / cm or less, or the contact angle of the cleaning liquid with the substrate surface is 50 degrees or less. Preferably.

The surfactant may be added after the cleaning liquid is prepared, or it may be added in advance to hydrogen peroxide, water, ammonia, organic amine, hydrochloric acid, sulfuric acid, hydrofluoric acid, etc. You may mix and prepare.

The present invention is particularly preferably used for a cleaning liquid composed of a mixed aqueous solution of ammonia and hydrogen peroxide.
Other than the mixed aqueous solution of ammonia and hydrogen peroxide, a mixed aqueous solution of choline (hydroxyltrimethylammonium hydroxide) and hydrogen peroxide, a mixed aqueous solution of TMAH (tetramethylammonium hydroxide) and hydrogen peroxide, hydrofluoric acid and hydrogen peroxide Can also be used as a mixed aqueous solution of, a mixed aqueous solution of hydrochloric acid and hydrogen peroxide, a mixed aqueous solution of sulfuric acid and hydrogen peroxide, and the like. The composition of a mixed aqueous solution of ammonia and hydrogen peroxide is usually such that the ammonia concentration is 0.1 to 1% by weight and the hydrogen peroxide concentration is 0.1 to 3%.
Used at 0% by weight.

[0015]

The present invention will be described in more detail with reference to Examples.

Example 1 A precleaned 3-inch silicon substrate was mixed with high-purity ammonia (28% by weight), high-purity hydrogen peroxide (30% by weight), and ultrapure water in a ratio of 1: 4: 20 (weight ratio). Was washed with the cleaning liquid containing the additives shown in Table 1 at 85 ° C. for 10 minutes. After rinsing with ultrapure water,
After air-drying, the amount of iron and copper deposited was analyzed by a total reflection X-ray fluorescence analyzer. At the same time, the surface tension of the cleaning liquid at 85 ° C. and the contact angle with the substrate were measured, and the contents of iron and copper in the cleaning liquid immediately after preparation were quantified by atomic absorption spectrometry.
For the measurement of the surface tension, an automatic surface tension meter CBVP-A3 type (Wilhelmy type) manufactured by Kyowa Interface Science Co., Ltd. was used. Further, a contact angle meter CA-D type (droplet method) manufactured by Kyowa Interface Science Co., Ltd. was used to measure the contact angle, and the contact angle was measured 10 seconds after applying the liquid. The results are shown in Table 1.

[0017](Table 1) Experiment additive In cleaning solution Surface of cleaning solution Adhesion of cleaning solution to substrate surface No. metal amount Tension contact angle Metal amount                   (ppb) (dyne / cm) (degree) (10^Tenatoms / cm²) Fe Cu Fe Cu (1) None 0.4 0.1 65 59 120 5 (2) EDTMP 0.4 0.1 64 59 5 3         10 ppb (3) EDTMP 0.4 0.1 65 58 4 3         10 ppm    (4) EDTMP 0.6 0.2 61 <5 <1 <1         10 ppb        Alkyl fens        Acid        100ppm (5) EDTMP 0.5 0.1 62 51 3 2         10 ppb        Alkyl fens        Acid        10 ppm (6) EDTMP 0.7 0.1 60 49 <1 <1         10 ppm        Polyacrylic acid         100ppm

[0018](Continued from Table 1) Experiment additive In cleaning solution Surface of cleaning solution Adhesion of cleaning solution to substrate surface No. metal amount Tension contact angle Metal amount                   (ppb) (dyne / cm) (degree) (10^Tenatoms / cm²) Fe Cu Fe Cu (7) EDTMP 0.5 0.1 58 45 <1 <1         10 ppm      2-ethyl-1,3      Hexanediol         500ppm (8) 2-Ethyl-1,3 0.5 0.1 58 44 95 4       Hexanediol         500ppm (Note) EDTMP in Table 1 is ethylenediaminetetra (me)
(Tylene phosphonic acid). Also, alkylbenzenes
Lyphon LH-500 from Lion Corp.
For Polyacrylic acid, use Poise 520 from Kao Corporation.
I used it.

Example 2 A pre-cleaned 3-inch silicon substrate was treated with high-purity hydrofluoric acid (50% by weight) and high-purity hydrogen peroxide (30% by weight).
And ultrapure water were mixed at a ratio of 1:15:85 (weight ratio), and the cleaning liquid containing the additives shown in Table 2 was used to prepare 3
It was immersed and washed at 0 ° C. for 10 minutes. After further rinsing with ultrapure water, it was air dried and analyzed for the amount of iron and copper deposited by a total reflection X-ray fluorescence analyzer. At the same time, the surface tension of the cleaning liquid at 30 ° C. and the contact angle with the substrate were measured, and the contents of iron and copper in the cleaning liquid immediately after preparation were quantified by atomic absorption spectrometry. The results are shown in Table 2.

[0020](Table 2) Experimental additive Surface of cleaning liquid in cleaning liquid Adhesion of cleaning liquid to substrate surface No. Metal amount Tension Contact angle Metal amount                   (ppb) (dyne / cm) (degree) (10^Tenatoms / cm²) Fe Cu Fe Cu (9) None 0.3 0.1 70 81 1 3 (10) DTPMP 0.3 0.1 70 80 1 1         1 ppm (11) DTPMP 0.5 0.1 28 <5 <1 <1         1 ppm        PEG alkyl       Phenyl ether         100ppm (Note) DTPMP in Table 2 is diethylenetriamine penta
(Methylenephosphonic acid) is shown. Also, PEG alkyl
Phenyl ether is polyethylene glycol alkyl group
Emulgen 147 from Kao Corporation
It was used.

[0021]

By using the cleaning solution of the present invention, it is possible to effectively clean a semiconductor substrate such that the metal deposition amount on the substrate surface is 1 × 10 ¹⁰ atoms / cm ² or less.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-275405 (JP, A) JP-A-3-53083 (JP, A) JP-A-3-70800 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) H01L 21/304 B08B 3/00 C11D 1/00-19/00

Claims (3)

(57) [Claims] 1. A semiconductor substrate cleaning liquid, wherein propylenediaminetetra (methylenephosphonic acid) and a surfactant are added to a basic hydrogen peroxide cleaning liquid. 2. The surface tension of the cleaning liquid is 60 dyne / cm or less, or the contact angle of the cleaning liquid with respect to the substrate surface is 5
The semiconductor substrate cleaning liquid according to claim 1, which is 0 degrees or less. 3. The semiconductor substrate cleaning liquid according to claim 1, wherein the basic hydrogen peroxide cleaning liquid is a mixed aqueous solution of ammonia and hydrogen peroxide.