JP3039372B2 - Semiconductor substrate cleaning processing apparatus and cleaning processing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to electrolytic ionic water generation and electrolytic ionic water generation mechanisms, and more particularly to a semiconductor substrate cleaning apparatus and a semiconductor substrate cleaning method.

[0002]

2. Description of the Related Art With the miniaturization of VLSI, the demand for cleaning the surface of a semiconductor substrate has become more and more intense. In particular, metal impurities are fatal if attached to the surface of a semiconductor substrate, and significantly deteriorate the electrical characteristics of a semiconductor device. Generally, the surface metal contamination concentration of a semiconductor substrate is 1 × ^{10 10} at.
It is said that the level needs to be oms / cm ² or less. Further, in recent years, it has been found that organic matter in a clean room deteriorates electrical characteristics of a semiconductor device. For controlling these contaminations, wet cleaning using ultrapure water and high-purity chemicals is indispensable.

[0003] Wet processing currently performed in the VLSI manufacturing process can be broadly divided into three types: cleaning, etching, and rinsing. These contents include: (1) Contaminants (metal contaminants, organic contaminants, organic and inorganic particles, resist residues, ionic residues, etc.) adhering to a substrate (semiconductor layer, metal wiring, insulating film, etc.)
And (2) a process of etching the substrate, and (3) a process of etching and removing a natural oxide film and an organic film formed on the surface of the substrate. It is. For example, in the process (1), H
PM (HCl / H ₂ O ₂ / H ₂ O = 1: 1: 6) or SP
M (H ₂ SO ₄ / H ₂ O ₂ = 5: 1) and the like are often used. In the process (2), the APM (NH ₄ OH / H ₂ O)
₂ / H ₂ O = 1: 4: 20). (3)
In the process (1), DHF (HF / H ₂ O = 1: 50 to 40
0) and the like are often used. As described above, since the wet cleaning process is performed using a large amount of various chemicals in the manufacturing process of the VLSI, large amounts of equipment and running costs are required for the drainage process. Pure water is used as the substrate for the wet treatment.

[0004] Used pure water is regenerated and used many times. Chemicals are also recycled and reused, but when their life has expired and their effects have ceased, they are disposed of after appropriate treatment for environmental conservation, such as decomposition and neutralization. However, there is a limit to reducing the amount of chemicals used by recycling and reuse. In addition, the current cleaning method has been developed for several decades, and it has become impossible to satisfy the recent demand for high cleanliness and low cost. Therefore, development of a new wet cleaning technology is strongly demanded. Therefore, the applicant has invented an innovative wet treatment apparatus and method capable of greatly reducing the amount of chemicals used, and has already filed an application (Japanese Patent Application No. 5-10).
5991, Japanese Patent Application No. 6-56107, Japanese Patent Application No. 6-5610
6, hereinafter referred to as prior application). This is a small amount of electrolyte (chemical solution)
Is a special water obtained by electrolysis of pure water to which is added, wet processing of semiconductors using this electrolyzed water, and it is possible to quickly generate electrolyzed water, thus reducing the use of chemicals, This means that waste can be reduced and the cost of collecting and processing waste can be reduced.

Conventionally, a high-purity Pt electrode (99.999%) has been used as an electrode material for electrolyzing pure water to which a chemical solution has been added, and on the anode side, an electrolyte represented by NH ₄ Cl has been used. A halogen-based substance was used. N
The electrochemical reaction on the anode side when H ₄ Cl is used as the electrolyte is shown.

2H ₂ O → O ₂ + 4H ⁺ 4e ⁻ (1) or 3H ₂ O → O ₃ + 6H ⁺ 6e ⁻ (2) and NH ₄ Cl → NH ₄ ⁺ + Cl ⁻ (3) and 2Cl ⁻ → Cl ₂ + 2e ⁻ (4) and Cl ₂ + 2H ₂ O → 2H ⁺ + 2HClO + 2e ⁻ (5) Cl ₂ + 4H ₂ O → 6H ⁺ + 2HCl ₂ + 6e ⁻ (6) or Cl ₂ + 6H ₂ O → 12H ⁺ + 2HCl ₃ + 10e ^- (7) or, _{^{and, 3HClO → 3H + + ClO 3}} - + 2Cl - (8) in the anode side, oxygen gas, ozone gas, at the same time hydrogen ions when the chlorine gas is generated, chlorine acids (chlorine and oxygen are combined ions), Chloride ions are generated. Of these, chloric acids and ozone gas have very high oxidizing power, and the conventional HPM
It is possible to remove trace amounts of metal impurities and organic impurities that could not be completely removed by cleaning of SPM or SPM.

[0007] When producing such electrolytic ionic water, the electrode uses high-purity Pt (99.999%). Since Pt has the property of dissolving a small amount in a strongly oxidizing solution containing chlorine (for example, hot aqua regia) on the acidic side, active chloric acid or ozone gas is present in a state where these hydrogen ions are large. If so, it is considered that the Pt electrode naturally dissolves. Pt is eluted by electrolysis due to the presence of a dissolving region in the acidic and oxidizing regions. During the electrolysis, Pt (Cl) ₄ ^2- exists in a stable state, but after the electrolysis is stopped, the oxidizing power (redox potential = OR)
Since P) rapidly decreases, it is considered that an unstable state exists. Since Pt is present in the solution in an unstable state in the anode water after the electrolysis is stopped, Pt is adsorbed on the silicon substrate when the silicon substrate is cleaned. Therefore, the anode water after the electrolysis is stopped (about 500 mV) having a low ORP and the anode water immediately after the electrolysis cannot be used, and very strict standards for the control of the oxidation-reduction potential and the pH were required (ORP ≧ 1000 mV, pH ≦ 2).

[0008]

SUMMARY OF THE INVENTION The object of the present invention is to solve the above-mentioned problems, reduce the contamination from the electrodes, increase the running cost, and improve the electrolytic ionized water immediately after electrolysis or after stopping electrolysis. The purpose of the present invention is to achieve a desired cleaning effect even when the cleaning is performed by using the method, and to significantly reduce pure water usage and power consumption.

[0009]

The above object is achieved by the following means.

That is, the present invention relates to a semiconductor substrate cleaning apparatus for supplying pure water to which an electrolyte has been added to an electrolytic cell and applying a voltage between electrodes provided in the electrolytic cell to generate electrolytic water. The present invention proposes an apparatus for cleaning a semiconductor substrate, wherein the electrode material is at least 99.999% of high-purity iridium or high-purity osmium.
The electrolyte is HCl, HBr, HI, Cl, Br, I
And the concentration range of the electrolyte is 5 mM to 100 mM.

Further, the present invention provides a method for cleaning a semiconductor substrate as described above.
The present invention proposes a method for cleaning a semiconductor substrate , wherein the processing apparatus cleans the semiconductor substrate at room temperature.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The method for producing electrolytic ionic water according to the present invention is very stable in an acidic and oxidizing region and has almost no dissolving region as a new electrode material in place of Pt used as a conventional electrode material. High-purity I with a purity of 99.999% or more
In this method, pure water to which an electrolyte is added is electrolytically decomposed using r or Os to generate electrolytic ionic water. Ir and Os can reduce power consumption more than Pt, and can also generate electrolytic ion water having the same composition as that obtained at the Pt electrode at the Ir electrode or the Os electrode (ORP ≧ 1000 mV, pH ≦ 2). In addition, a strong oxidizing substance such as Cl ₂ → ClOx is likely to be selectively generated at the Ir electrode or the Os electrode. In addition, elution of the electrode material as seen in the Pt electrode can be prevented. Therefore, not only during the electrolysis, but also with the ionic water immediately after the electrolysis or after the electrolysis is stopped, the desired cleaning can be sufficiently performed. That is,
The electrolytic ion water on the anode side obtained by using the Ir electrode or the Os electrode can remove metal contamination and organic substance contamination. That is, the ORP becomes sufficiently high with low power, and a strong oxidizing substance such as ClOx is easily generated. Therefore, the processing temperature may be room temperature, and when the temperature is increased, the strongly acidic substance which is deeply involved in cleaning is decomposed. It is not preferable because it diffuses into the atmosphere. In addition, the concentration range of the electrolyte added for increasing the electrolysis efficiency and for generating the strongly acidic substance involved in the cleaning ranges from a concentration sufficient to cause electrolysis to an overcurrent, and a concentration before the electrolysis does not occur, from 5 mN to 10
A range of 0 mM is preferred.

As an electrolyte added to pure water, HCl,
Examples include ammonium salts containing HBr, HI, Cl, Br, and I.

As described above, the running cost and the power consumption can be suppressed at the same time, and the cleaning performance is improved.

[0015]

The present invention will be described below in more detail with reference to examples. First Embodiment Next, a first embodiment of the present invention will be described with reference to a schematic configuration diagram of a wet processing apparatus of FIG. The electrolytic cell 1 is divided into two cells by a diaphragm composed of an ion exchange resin,
An anode 3a and a cathode 3b are arranged on both sides of the DC electrode 5a.
It is connected to the. As the ion exchange resin, a mixture of an anion exchange resin and a cation exchange resin is used. Iridium was used for the electrode materials 3a and 3b. Iridium used had a purity of 99.999%. Pure water or regenerated water is supplied to the anode side, and the anode water subjected to the electrolysis treatment is supplied to the wet treatment step in the treatment tank 6a.
This embodiment does not consider the use of electrolytic ion water on the cathode side.

In the electrolytic cell shown in FIG.
140 mM HC was added. Before electrolysis, immediately after electrolysis, electrolysis 1
After an hour, the washing water after the electrolysis was stopped was prepared. The wafers to be cleaned with these cleaning waters were subjected to natural oxide film removal (DHF) and acid cleaning as pre-cleaning. Then, there were two levels with and without DHF treatment. This is because noble metal elements tend to be more easily adsorbed on the silicon surface than on the natural oxide film. Ion water produced using an Ir electrode (immediately after electrolysis,
One hour after the electrolysis and after the electrolysis was stopped), the above-described two-level wafer was washed. The liquid temperature during washing was normal temperature. At this time, the reference is DHF only after pre-cleaning or after pre-cleaning.
The level was treated.

Table 1 shows the results of measurement of total reflection X-ray fluorescence of metal impurities remaining on the wafer surface after various cleaning treatments.
Shown in

[0018]

[Table 1] FIG. 2 shows the result of measurement of the minority carrier lifetime of the wafer after the cleaning process after the heat treatment at 950 ° C. and O ₂ .
Shown in

The measurement results of the metal impurities have DHF treatment,
The levels without Ca, Ti, Cr, Fe, Ni, Cu,
Zn, Pt and Ir are almost below the detection limit or 10 ¹⁰
The level was 〜１０10 ⁹ atmos / cm ² . The result of the minority carrier lifetime is 500-600μ which is almost the same as the pure water cleaning level in both cases with and without DHF treatment.
sec. The pH at this time is before electrolysis, immediately after electrolysis,
One hour after electrolysis, it was 1.5 together with after electrolysis was stopped,
ORP showed 500 V or less before and after electrolysis stopped, and 1000 V or more during electrolysis.

As a comparative example, Table 2 shows the results obtained by using Pt as the electrode material of FIG. The electrolyte is the same as for Ir,
HC was 140 mM. The type of wafer was also determined to be with or without DHF treatment. The washed wafer is 950 as described above.
FIG. 3 shows the result of the measurement of the minority carrier lifetime after the heat treatment at 0 ° C. and O ₂ . At the level without the DHF treatment, the values of the lifetime were almost the same at the level of only the cleaning, the level of the pure water cleaning, the level before the anode electrolysis, during the electrolysis, and the level after the electrolysis was stopped. On the other hand, in the level with the DHF treatment, a decrease in the lifetime by one digit or two digits was confirmed before and after the electrolysis was stopped. It can be seen that the lifetime does not decrease when a natural oxide film is present on the wafer surface, and that the lifetime decreases when the natural oxide film is removed from the wafer surface. What can be considered from this phenomenon is DHF
Noble metal (Cu,
Etc.) are considered to have adhered. The following experiment was conducted to elucidate the cause. Metal impurities in the ionic water on the anode side produced with the Pt electrode were measured by ICP-MS. The measurement levels are shown below.

Approximately 1 hour of pure water flow (for pipe cleaning) ↓ Electrolysis OFF Chemical solution addition ON (HCl, 40m
M) Sampling after 5 minutes ↓ Electrolysis ON Chemical solution addition ON (HCl, 40m)
M) ・ ・ ・ Sampling after 5 minutes ↓ Electrolysis OFF Chemical solution addition ON (HCl, 40m)
M) ・ ・ Sampling after 5 minutes ↓ Pure water flow Chemical liquid addition ON (HCl, 40m
M) After 5 minutes, Table 1 shows the results of evaluation by sampling ICP-MS. From this result, it was found that Pt was eluted by electrolysis at the Pt electrode. It is very likely that the lifetime is reduced due to the eluted Pt.

[0022]

[Table 2] Second Embodiment Next, a second embodiment of the present invention will be described. Using the wet processing apparatus shown in FIG. 1, Ir was used as an electrode material (purity: 99.999%) to produce electrolytic ion water on the anode side. 40m as electrolyte from mass transport system 9
M HCl was added to generate electrolytic ionized water on the anode side. As a comparative experiment, an electrode material Pt and an electrolyte of 4 were used.
0 mM HCl was added to generate electrolytic ionized water on the anode side. Then, the wafer after the removal of the natural oxide film was washed. The temperature of the cleaning liquid at this time was normal temperature. Normal AP
Cleaning with M + HPM and APM + SPM respectively was also performed.

At this time, the temperature of the cleaning liquid was 65 ° C. The wafer surface after cleaning is decomposed with hydrofluoric acid vapor, and the recovered liquid (D
After collecting by scanning with HF + H ₂ O ₂ ), metal impurities after various washing treatments were measured by atomic absorption analysis. Table 3 shows the measurement results.
Shown in In the existing APM + HPM and APM + SPM cleaning, contamination of Ca, Cu, Al and the like was observed. In contrast, the electrolytic ionic water was generally good regardless of the difference between the electrodes. The Pt electrode tended to contain a large amount of Cu. This is considered to be a phenomenon in which oxidizing ozone gas and chloric acids are selectively generated more easily in the Ir electrode than in the cleaning effect.

[0024]

[Table 3] Third Embodiment Next, a third embodiment of the present invention will be described. Using the wet processing apparatus of FIG. 1, electrolytic ionized water on the anode side was generated. 40m as electrolyte from mass transport system
M HCl was added to generate electrolytic ionized water on the anode side. Electrode materials used were high-purity Ir (99.999%) and Ir (99.9%). The cleaning treatment was performed at room temperature. Table 4 shows the measurement results of the amount of metal impurities remaining on the wafer surface after treatment with two types of ionized water. Ir
When the purity of the electrode was low, the level was substantially below the detection limit without DHF treatment, but elution was observed with DHF treatment. Elution of Cr, Ti, etc. was also observed. On the other hand, when the purity of the Ir electrode is high, D
Regardless of the HF treatment, the measured metal was below the detection limit. FIG. 4 shows the measurement results of the lifetime after heat treatment of the same level wafer. At both levels with and without DHF, the purity was reduced by about one third when the purity of the Ir electrode was low.

[0025]

[Table 4]

[0026]

As described above, according to the present invention,
Desired electrolyzed water can be generated promptly. Also,
Energy wasted to obtain the desired electrolyzed water can be significantly reduced. Further, the efficiency of electrolytic water generation can be increased without increasing the applied voltage. The temperature at the time of the cleaning process can be performed at room temperature. Furthermore, since elution of impurities from the electrode material or the like can be eliminated, cleaning performance is improved, and strict management of ORP is reduced. As a result, it is possible to reduce costs while reducing environmental impact by reducing the amount of chemicals used, reducing waste, and simplifying equipment for collecting and treating waste.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a semiconductor cleaning processing apparatus of the present invention.

FIG. 2 is a graph showing a measurement result of a minority carrier lifetime after various cleaning processes in Example 1 of the present invention.

FIG. 3 is a graph showing a measurement result of a minority carrier lifetime after various cleaning processes of a comparative example of Example 1 of the present invention.

FIG. 4 is a graph showing measurement results of a small number of carrier lifetimes after various cleaning processes according to the third embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electrolysis tank 2 Diaphragm 3a Anode (anode) 3b Cathode (cathode) 4a Processing tank (anode side) 4b Processing tank (cathode side) 5 DC power supply 6 Waste liquid processing tank 7 Pure water supply port 8 Ion exchanger 9 Material addition system 10 Between pure water introduction

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-8-309357 (JP, A) JP-A-6-260480 (JP, A) JP-A-7-256259 (JP, A) JP-A-7-256 263391 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) H01L 21/304 C02F 1/46 C25B 11/08

Claims (5)

(57) [Claims] 1. A cleaning apparatus for a semiconductor substrate, wherein pure water to which an electrolyte is added is supplied to an electrolytic cell, and a voltage is applied between electrodes provided in the electrolytic cell to generate electrolytic water. An apparatus for cleaning a semiconductor substrate, which is made of high-purity iridium of 99.999% or more. 2. A cleaning apparatus for a semiconductor substrate, wherein pure water to which an electrolyte is added is supplied to an electrolytic cell, and a voltage is applied between electrodes provided in the electrolytic cell to generate electrolytic water. A cleaning apparatus for a semiconductor substrate, characterized in that it is high purity osmium of 99.999% or more. 3. The electrolyte of claim 1, wherein the electrolyte is HCl, HBr, HI,
The semiconductor substrate cleaning apparatus according to claim 1, wherein the apparatus is any one of ammonium salts containing Cl, Br, and I. 4. 4. The concentration range of the electrolyte is from 5 mM to 100 mM.
4. The apparatus for cleaning a semiconductor substrate according to claim 3, wherein the concentration is mM. 5. The method according to claim 1, wherein:
A method for cleaning a semiconductor substrate, comprising cleaning the semiconductor substrate at room temperature using the apparatus for cleaning a semiconductor substrate according to any one of the preceding claims.