JPH09139371A - Method for cleaning semiconductor substrate and cleaning device used for the method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cleaning method of the surface of a semiconductor substrate, which is easier and safer and effective. SOLUTION: In a final cleaning process, a gas component including 10<-6> to 100% of gas giving reducing ability is brought into contact with pure water or the mixed solution of pure water and acid or alkali at more than 0.1 atmospheric pressure and the substrate is cleaned, or dissolved oxygen quantity is controlled in cathode water in which an oxidation-reduction potential obtained by electrolyzing pure water or the mixed solution of pure water and acid or alkali is negative and the pH value is 7 to 3, and the substrate is cleaned, otherwise the substrate is cleaned in the atmosphere of inactive gas at one atmosphere pressure, which includes 10<-6> to 100% of gas giving reducing ability by using the cathode water.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique of cleaning a semiconductor substrate, particularly a bare pattern formed by partially exposing the surface of a semiconductor substrate covered with an oxide film.

[0002]

2. Description of the Related Art In semiconductor processes, residual impurities on the surface of a semiconductor crystal have an extremely large effect on the quality of a semiconductor device to be subsequently manufactured. Taking the case of a silicon (Si) crystal surface as an example, residual impurities such as a natural oxide film, organic contaminants, and heavy metals present on the surface make it difficult to control the thin gate oxide film with high accuracy, and the dielectric breakdown voltage. It causes deterioration of electrical characteristics such as. Further, such impurities act as a process impeding factor and a device performance deteriorating factor such as an increase in series resistance and deterioration of rectification characteristics in the production of a metal ohmic contact. Therefore, it is indispensable in the process of manufacturing a semiconductor manufacturing apparatus to sufficiently clean the crystal surface and form a clean semiconductor substrate surface without residual impurities.

However, in the conventional cleaning of the surface of the semiconductor substrate, it cannot be said that the residual impurities on the surface of the substrate have been sufficiently reduced. For example, deterioration of device performance, which is considered to be caused by contamination of the crystal surface of the substrate, is often observed as process dependence.

As a solution to this problem, RCA cleaning (W. Kern RCA Review Vol.31 (1970)) etc.
A method of covering the i surface with an oxide film may be applied. Generally, when an oxide film is formed on a Si substrate, residual impurities on the Si substrate before forming the oxide film, that is, carbon, oxygen, etc., are taken into the oxide film. Therefore, if the adhesion of residual impurities to the surface of the Si substrate can be suppressed in the next step of removing the oxide film after forming the oxide film, a cleaned Si surface can be obtained.

In the case of the above-mentioned RCA cleaning, after forming an oxide film having a thickness of 1 nm or more on a Si substrate, the oxide film is introduced into a vacuum device capable of heating the substrate, for example, Si of about 10 ⁻⁸ Pa.
By heating at a temperature of 800 ° C. or higher in a high vacuum that is unlikely to contaminate the substrate, it is possible to detach the oxide film and obtain a cleaned surface. Further, according to this method, the process of forming the oxide film is relatively simple, and the interface is protected by the oxide film even if it is left in the atmosphere, and thus the handling is easy.

[0006] Here, the above-mentioned vacuum exhaust under high vacuum poses problems such as an increase in the size of the device and an increase in the cost of the device, especially when a large-diameter substrate of 6 inches or more is processed by the above method. Is coming. In some cases, the complexity of the processing method may contribute to the increased opportunity for substrate contamination during processing.

Further, in such a treatment method, the number of steps is complicated and enormous, and as a result, the amount of chemicals and pure water used for cleaning and the like is large, and the reduction in the number of steps and the cost are further reduced. There is a demand for a more simplified method from the viewpoint of global environment conservation by reducing the use amount of the above chemicals.

In addition, recent ICs, which have been remarkably miniaturized in recent years,
For example, a semiconductor manufacturing process for forming a different semiconductor device on a substrate on which a semiconductor device or the like is already formed is becoming indispensable. In such a process, a bare pattern is formed in the vicinity of the already formed semiconductor device, for example, by partially exposing the oxide film on the surface of the semiconductor substrate covered with the oxide film, and the bare pattern is formed on the bare pattern. Further, semiconductor layers are stacked. In such a process, it is possible to realize a semiconductor device forming process at a lower temperature without using the above high vacuum heating process, specifically,
It is becoming necessary to perform the entire semiconductor manufacturing process at a temperature of, for example, 800 ° C. or lower, and to obtain a clean Si surface at a lower temperature even in substrate cleaning. Nevertheless, at present, no effective method for Si surface cleaning, which can be expected to realize the above-mentioned low temperature process, has been shown.

In the process to which the high temperature treatment cannot be applied as described above, it is necessary to remove the oxide film immediately before the process. Generally, HF solution or N
A treatment using a hydrofluoric acid-based solution such as an H ₄ F solution is performed.
The natural oxide film is removed in this solution, and the surface terminated with hydrogen is
It is one of the advantages of using the above solution that it is relatively stable in the atmosphere. The Si surface after the treatment in the above solution is
Usually, treatment with pure water is also performed from the viewpoint of ensuring safety.
However, it has been reported that a silicon oxide class called water glass remains on the Si surface after this process and deteriorates the electrical characteristics of the device fabricated thereon, and removal of it is reported. There is a long-felt need for a method that can be realized.

As described above, although the surface control technology for realizing the cleaning of the semiconductor crystal has been studied as indispensable, the number of steps in the conventional processing method is complicated and enormous, and as a result, the chemicals used for cleaning or the like. And the amount of pure water used is large,
From the viewpoints of reducing the number of processes and costs due to these reductions, and also from the viewpoint of global environmental conservation by reducing the amount of chemicals used, it is essential to realize a more simplified method.

On the other hand, a problem in the cleaning treatment process as one of the actual device manufacturing processes is that the surface residual impurities after the treatment may not be sufficiently removed, and a complete treatment method has not been realized. Is. Therefore, in the future semiconductor crystal surface cleaning process, further simplification of the process and sufficient removal of impurities after the treatment are both desired.

[0012]

SUMMARY OF THE INVENTION The object of the present invention was made in view of the above circumstances, and it is possible to realize cleaning of the surface of a semiconductor substrate more easily and safely, and to carry out more effective cleaning. To provide a method.

Another object of the present invention is to provide a cleaning device for a semiconductor substrate which can more easily and safely realize cleaning of the surface of the semiconductor substrate and can perform more effective cleaning. Still another object of the present invention is to manufacture a high-performance semiconductor device at low cost by using such a cleaning method.

[0014]

According to a first aspect of the present invention, a bare pattern formed by partially exposing a surface of a semiconductor substrate coated with an oxide film is formed with pure water, acid and pure water. In the method for cleaning a semiconductor substrate, the method comprises the step of surface-treating with at least one cleaning solution selected from the group consisting of a mixed solution of 1. and a mixed solution of alkali and pure water,
In the final cleaning step in the surface treatment step, among the solutions obtained by electrolyzing the cleaning solution, cathode water having a negative oxidation-reduction potential and a pH of 7 to 13 was dissolved oxygen concentration of 300 ppb or less. There is provided a method for cleaning a semiconductor substrate, which is characterized in that it is used while being maintained.

According to a second aspect of the present invention, a bare pattern formed by partially exposing the surface of an oxide film-covered semiconductor substrate is formed by using pure water, a mixed solution of acid and pure water, and an alkali. In the method of cleaning a semiconductor substrate, which includes a step of performing a surface treatment with a cleaning solution selected from the group consisting of a mixed solution of pure water and a mixed solution of pure water, in the final cleaning step of the surface treatment step, a gas that imparts a reducing property is used. ^A method for cleaning a semiconductor substrate is performed using a final cleaning solution added by bringing a gas component containing ⁻⁶ to 100% at 10 ⁻³ atm or more into contact with the cleaning solution. .

According to a third aspect of the present invention, means for supplying a cleaning solution selected from the group consisting of pure water, a mixed solution of pure water and an acid, and a mixed solution of pure water and an alkali, A means for introducing a gas component containing 10 ⁻⁶ to 100% of a reducing-providing gas into the cleaning solution at 10 ⁻³ atm or more, and adding the reducing-providing gas to the cleaning solution, the reducing property A cleaning solution to which a gas for imparting is added, is provided with a means for surface-treating a bare pattern formed by partially exposing the surface of the oxide film-covered semiconductor substrate. A cleaning device is provided.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION After removing an oxide film with an HF solution,
The method of finishing by washing with pure water enables reliable removal of the oxide film at low temperature (room temperature). However, fine silicon oxide is generated on the Si surface by the subsequent cleaning with pure water. Less than,
This minute silicon oxide is called water glass. This is HF
It is not observed immediately after the treatment, but it exists after washing with pure water,
This may cause deterioration of the electrical characteristics of the device.

It is difficult to transfer the Si substrate immediately after the HF solution treatment to the next process in terms of safety to the human body due to residual fluorine remaining on the SI substrate and corrosion of the apparatus. It is indispensable to remove fluorine by washing with pure water.

The inventor of the present invention can remove fluorine by using a solution of electrolyzed water obtained by electrolyzing water and having a pH value higher than that of Si. It has been found that it is possible to perform a treatment that does not generate water glass, unlike ordinary pure water, without the formation of the above.

According to a first aspect of the present invention, a bare pattern formed by partially exposing the surface of a semiconductor substrate coated with an oxide film is formed by using pure water, a mixed solution of acid and pure water, and an alkali. In the method of cleaning a semiconductor substrate, the method comprises the step of surface-treating with at least one cleaning solution selected from the group consisting of: and a mixed solution of pure water. Of the solution obtained by electrolysis, the redox potential is negative,
Cathode water having a pH of 7 to 13 is dissolved in a dissolved oxygen concentration of 3
A method for cleaning a semiconductor substrate is provided, which is used while being kept at 00 ppb or less.

According to a preferred embodiment of the first aspect of the present invention, the bare pattern formed by partially exposing the surface of the semiconductor substrate coated with the oxide film is mixed with pure water and acid and pure water. In the method for cleaning a semiconductor substrate, which has a step of performing a surface treatment using a cleaning solution selected from the group consisting of a solution and a mixed solution of alkali and pure water, the final cleaning step in the surface treatment step is a closed system. A solution obtained by electrolyzing the cleaning solution, which is carried out in an inert gas atmosphere containing 10 ⁻⁶ to 100% of a reducing gas at 10 ⁻³ atm or more, preferably 1 atm or more, A method for cleaning a semiconductor substrate is provided, which uses negative electrode water having a negative redox potential and a pH of 7 to 13.

According to the first aspect and the preferred embodiment of the first aspect of the present invention, pure water, or pure water and, for example, hydrochloric acid, hydrofluoric acid, sulfuric acid, nitric acid, hydrogen peroxide, aqueous ammonia,
In the step of performing the Si surface treatment using a mixed solution of an acid and an alkali such as an organic alkali, in the final washing step, the solution has a negative redox potential and a pH of 7 to 13
By using the cathodic water, it is possible to perform a treatment that does not generate water glass and can be expected to have the same cleaning effect as that obtained by the conventional mixed liquid treatment of various kinds of acid / alkali water. Further, it is possible to reduce the amount of chemicals used as compared with the conventional method. From this viewpoint, it is possible to ensure process safety, reduce the amount of chemicals used, and simplify the process.

Further, according to the first aspect of the present invention, the final cleaning step is preferably performed in a closed system. According to the first aspect of the present invention, by using the cathode water used while maintaining the dissolved oxygen concentration at 300 ppb or less, the semiconductor substrate by oxygen dissolved in the cleaning solution, such as S, is used.
It is also possible to prevent oxidation of the i substrate.

Further, according to the preferred embodiment of the first aspect of the present invention, the cleaning solution is prevented from being unnecessarily dissolved in oxygen by cleaning in an inert gas atmosphere of 1 atm or more. it can. As a result, it is possible to prevent the Si substrate from being oxidized by oxygen dissolved in the cleaning solution. Further, a gas that imparts reducibility is 10 ⁻⁶ to 100
%, The reduction action suppresses the generation of silicon oxide, does not generate water glass, and is equivalent to the treatment effect obtained by the conventional mixed liquid treatment of various acid / alkaline water. A cleaning effect can be expected. It is preferable to use, for example, hydrogen or hydrogen radicals having a different energy state from hydrogen in pure water as the gas that imparts the reducing property. As the inert gas, nitrogen, helium, argon or the like can be used.

Further, according to the first aspect of the present invention and the preferred embodiment of the first aspect, the anode water can be further added to the cathode water used. Anode water can be used to mainly dissolve and remove metal contaminants such as copper.

FIG. 1 is a diagram showing the relationship between the pH of the solution and the redox potential. In the figure, the area surrounded by the solid line 101 represents the range of the cathode water, and the solid line 102
The area surrounded by represents the range of anode water. It is effective to suppress the generation of water glass that the redox potential is about -0.1 to -1 V and the pH is 7 to 13 in the region surrounded by 101. Further, the anode water has a redox potential of 1 V ± about 0.5 V.

The drying method after the treatment may be a conventionally used method such as heating, nitrogen, ultrasonic wave or rotation, but according to the present invention, the electrolytic ionized water droplets remain in the atmosphere. Sufficient cleaning can be performed even when natural drying is performed inside.

By the way, when the anode water and the cathode water are taken out from the electrolytic ionized water production apparatus and filled in a container and kept in the atmosphere, this effect lasts for about 2 days for the anode water and several hours for the cathode water. To do. This corresponds to the time until the oxidation / reduction potential in each solution returns to zero.

FIG. 2 shows the results of examining the cleaning ability of the substrate after mixing the anode water and the cathode water. According to FIG.
It was found that the cleaning effect of the anodic water and the cathodic water continued until about 10 minutes after mixing. Generally, it is sufficient to perform the substrate pretreatment in the solution for about several minutes, and the substrate treatment can be surely performed if the processing capacity holding time of the mixed solution is secured.

FIG. 3 is a partial flow chart showing an example of a process in which cathode water and anode water are mixed and treated. Furthermore, for comparison, a partial flow chart of the conventional processing,
FIG. 4 and FIG. 5 are partial flow charts in the case of separately supplying anode water and cathode water for processing.

According to FIG. 3, it is possible to obtain the cleaning effect of the anode water and the cleaning effect of the cathode water at the same time by using the solution obtained by mixing the anode water and the cathode water for the treatment. As a result, anode water +
The surface treatment for cleaning is completed by performing the pure water treatment only once after the treatment with the mixed solution of cathode water. Therefore, as is clear from comparison with FIG. 5, according to this process, the steps of the anode water treatment and the pure water treatment are substantially different from those of the method of separately supplying the anode water and the cathode water. It can be reduced by one time. Further, in the process shown in FIGS. 3 and 5 using electrolytic ionized water, at least one pure water treatment process can be shortened as compared with the process shown in FIG. Further, in some cases, the HF process can be deleted.

The method according to the first aspect of the present invention is, for example, at least one cleaning selected from the group consisting of pure water, a mixed solution of acid and pure water, and a mixed solution of alkali and pure water. Means for electrolyzing the solution to separate cathode water having a negative redox potential and having a pH of 7 to 13, means for controlling the dissolved oxygen amount of the cathode water to 300 ppb or less,
And a cleaning system including means for surface-treating a bare pattern formed by partially exposing the surface of the semiconductor substrate coated with an oxide film, using the cathode water in which the amount of dissolved oxygen is controlled. be able to.

The method according to the preferred embodiment of the first aspect of the present invention is at least selected from the group consisting of pure water, a mixed solution of acid and pure water, and a mixed solution of alkali and pure water. A means for electrolyzing one washing solution to separate cathode water having a negative oxidation-reduction potential and having a pH of 7 to 13, a means for supplying a gas that imparts a reducing property to the cathode water, and the gas were supplied. It can be carried out by using a closed cleaning system equipped with a means for surface-treating a bare pattern formed by partially exposing the surface of the semiconductor substrate coated with an oxide film using cathode water.

According to a second aspect of the present invention, a bare pattern formed by partially exposing a surface of a semiconductor substrate coated with an oxide film is formed by using pure water, a mixed solution of acid and pure water, and an alkali. In the method of cleaning a semiconductor substrate, which includes a step of performing a surface treatment with a cleaning solution selected from the group consisting of a mixed solution of pure water and a mixed solution of pure water, in the final cleaning step of the surface treatment step, a gas that imparts a reducing property is used. ^The semiconductor substrate is characterized in that it is carried out by using a final cleaning solution added by bringing a gas component containing ⁻⁶ to 100% at 10 ⁻³ atm or more, preferably 0.1 atm or more into contact with the cleaning solution. A cleaning method is provided.

According to the second aspect of the present invention, pure water, or a solution obtained by mixing pure water with an acid or alkali such as hydrochloric acid, hydrofluoric acid, sulfuric acid, nitric acid, hydrogen peroxide, aqueous ammonia, organic alkali, etc. In the step of performing the Si surface treatment by using, by adding a gas that imparts a reducing property to the cleaning solution in the final cleaning step, the reducing action causes
Generation of silicon oxide is suppressed, water glass is not generated, and a cleaning effect equivalent to the treatment effect obtained by the conventional mixed liquid treatment of various kinds of acid / alkali water can be expected. Further, it is possible to reduce the amount of chemicals used as compared with the conventional method. From this viewpoint, it is possible to ensure process safety, reduce the amount of chemicals used, and simplify the process.

According to the second aspect, the final washing step is preferably performed in a closed system. In addition, a gas component containing 10 ⁻⁶ to 100% of a reducing property-imparting gas is
By contacting with the cleaning solution at 0 ^-3 atm or more, preferably 0.1 atm or more, the gas component can be sufficiently dissolved in the cleaning solution.

In the second aspect of the present invention, as a cleaning solution, further, pure water or an electrolytic ionized water obtained by electrolyzing a solution in which pure water and an acid or an alkali are mixed is oxidized. It is also possible to use cathodic water having a negative reduction potential and to add a gas that imparts reducibility to obtain a final cleaning solution. This makes it possible to use the characteristics of the anode water and the cathode water, and to expect the same effect as the treatment effect obtained by the conventional mixed liquid treatment of various kinds of acid / alkali water. For example, of the electrolytic ionic water obtained by electrolyzing pure water, if cathode water is used, generation of silicon oxide can be suppressed by its reducing action. Alternatively, even if a solution having a pH value higher than that of Si is used, it is possible to perform the treatment without forming an oxide film or the like on the Si surface and further without generating silicon oxide such as pure water.

Specifically, it is possible to remove the metal remaining on the Si surface with the anode water and the particles with the cathode water. As a result, the amount of chemicals used can be reduced as compared with the conventional method.

From the above, by using the present invention, it is possible to ensure process safety, reduce the amount of chemicals used, and simplify the process. Since no chemicals are used, it can be used as the final finish of the Si surface.

Further, in the present invention, it is preferable to use, for example, hydrogen or hydrogen radicals having an energy state different from that of hydrogen in pure water as the reducing property-imparting gas. Hydrogen radicals having an energy state different from that of hydrogen are generated when hydrogen is decomposed by photolysis, electron impact, heating, or when pure water is electrolyzed. By using the excited species whose energy state is excited in this way or the mixed gas in which the excited species are mixed in the hydrogen gas in the present invention, a further effect can be expected as compared with using only the hydrogen gas.

In particular, when hydrogen and hydrogen radicals having different energy states from hydrogen are dissolved in pure water, the cleaning time is shortened and the S by OH ⁻ ions of the field ion water is reduced.
Since the surface roughness of i (100) can be suppressed, it may be possible to reduce the processing cost and obtain a more flat and clean bare surface at the same time.

A normal processing container is opened to the atmosphere, and oxygen or the like from the atmosphere is taken into the solution as dissolved oxygen, and this oxygen contributes to the oxidation of the Si surface. Even if the treatment liquid is a reducing solution, if the oxygen is not suppressed, the treatment effect may be considerably reduced. For this reason,
In the present invention, the dissolved gas concentration in the processing container is preferably controlled. As the method, for example, by reducing the gas concentration in the treatment liquid, introducing the treatment liquid to the treatment container while maintaining the reduced concentration, and sealing the container, or controlling the gas atmosphere in contact with the container, The effect can be maximized.

The drying of the substrate cleaned according to the invention is
Although it is possible to use a conventionally used method such as heating, nitrogen, ultrasonic waves, or rotation, the effect of the present invention can be obtained even when natural drying is performed in the atmosphere while the electrolytic ion water droplets remain. May be

The method according to the second aspect of the present invention can be carried out by using the following apparatus, for example. According to a third aspect of the present invention, means for supplying a cleaning solution selected from the group consisting of pure water, a mixed solution of pure water and an acid, and a mixed solution of pure water and an alkali, to the cleaning solution. 1
A means for introducing a gas component containing 10 ⁻⁶ to 100% of a reducing-providing gas at 0 ⁻³ atm or higher, preferably 0.01 atm or higher, and adding the reducing-providing gas to the cleaning solution; A means for surface-treating a bare pattern formed by partially exposing the surface of a semiconductor substrate coated with an oxide film by using a cleaning solution to which a gas that imparts the reducing property is added is provided. It can be implemented using a semiconductor substrate cleaning apparatus.

The apparatus according to the third aspect of the present invention preferably further comprises a pressurizing means for pressurizing at least the gas component to dissolve it in the cleaning solution. The device according to the third aspect is preferably a closed system.

Hereinafter, the present invention will be described more specifically with reference to the drawings. First, an example of a processing system used in a preferred embodiment according to the first and first aspects of the present invention will be described.

FIG. 6 is a schematic diagram showing an example of a treatment system for performing treatment with cathode water according to the first aspect of the present invention. As shown in FIG. 6, pure water 6 supplied from the pure water producing apparatus 1 is electrolyzed through the ion exchange membrane 5 by applying a voltage to the anode 3 and the cathode 4 in the electrolytic cell 2. , Electrolyzed water 61, 62. The obtained electrolyzed water 61 and 62 are introduced into the treatment tanks 801 and 802, respectively. The processing tanks 801 and 802 on the anode side and the cathode side, respectively.
In the inside, the wafer 71 is placed in the wafer case 91 and the wafer 72 is placed.
Are held in the wafer cases 92, respectively. In addition, each processing layer 801, 802 can be hermetically sealed with a lid 231, 232.
By providing each of them, it is possible to prevent dust, oxygen, carbon dioxide, and the like mixed from the atmosphere.

According to the present invention, the surface treatment of a wafer having a bare pattern formed by partially exposing a silicon wafer coated with an oxide film is performed by this cathode water side treatment tank 802.
Then, the electrolyzed water 62 supplied is used. If necessary, the surface treatment of the wafer can be further performed in the anode side treatment tank 801 using the electrolyzed water 61.

If necessary, the valves 191, 19
The oxide film on Si can be removed by arbitrarily adding the hydrofluoric acid solutions 121 and 122 in the hydrofluoric acid containers 111 and 112 prepared in advance to the electrolyzed water 61 and 62 via the step 2 above.

Further, the electrolytic bath 2 and the treatment baths 801, 802
And a gas-liquid separator 2 each having a valve 221 between
11. By disposing the gas-liquid separation device 212 having the valve 222, the undesired gas generated in the electrolytic cell 2 is
They can be removed via the valves 221 and 222, respectively.

According to the first aspect of the present invention, the dissolved oxygen amount is controlled to be below a predetermined level by providing degassing means 261 and 262 on the gas-liquid separation devices 211 and 212, respectively. You can The level of dissolved oxygen is 0
When it is up to 300 ppb, the oxidation of the Si wafer due to the action of oxygen can be prevented.

FIG. 7 is a schematic diagram showing an example of the processing system according to the preferred embodiment of the first aspect of the present invention. As shown in FIG. 7, this apparatus has a gas addition means 120 through a valve 141 between the electrolytic cell 2 and the processing tanks 801 and 802 instead of the degassing means 261 on the gas-liquid separation apparatus 211. 6 except that is provided
It has the same configuration as the device shown in FIG. This gas addition means 1
20 to provide a purge gas 1 containing a reducing gas having a desired concentration
By pressurizing at 30, a higher antioxidation effect of the Si wafer can be expected. Here, the purge gas pressure is 10
^{At a} pressure of ^-3 atm or higher, the concentration of reducing gas is 10 ^-6 % to 100%. If necessary, degassing means 261 can be provided.

FIG. 8 is a graph showing the surface residual water glass amount after cleaning the Si surface with the cathode water according to the first aspect of the present invention. HF in the figure for comparison
The amount of residual water glass on the surface after the treatment and the ordinary treatment of pure water and the amount of residual water glass on the surface immediately after the HF treatment are shown. Referring to FIG. 8, according to the present invention, the surface of a bare pattern formed by partially exposing a silicon wafer coated with an oxide film using cathode water having a negative redox potential and having a pH of 7 to 13. When the treatment is performed, the amount of water glass that could not be removed on the surface after the conventional pure water treatment was not removed without heating in a vacuum or complicated wet treatment, and the residual amount was the same as that on the Si surface after the HF treatment. Can be reduced to

Specifically, after the natural oxide film in the pattern of the Si substrate surrounded by the oxide film is treated with the HF solution and then washed with normal pure water and then dried, the natural oxide film surrounded by the oxide film is removed. Bare S of 5 × 5 μm ² with oxide film removed
Over 10 oxides were observed on the i pattern.

When this Si substrate was treated with an HF solution and immediately dried, no post oxide was observed on a pattern having the same size as the pattern. Finally, when a treatment similar to this Si substrate was performed with the cathode water according to the present invention, there was no oxide in the pattern, or only one oxide at maximum was observed. As described above, the cleaning treatment according to the present invention has an effect of removing the water glass remaining on the Si substrate after the cleaning step and the water glass generated during the process of cleaning to drying after cleaning. As a result, a Si cleaning process having a higher cleaning effect than in the conventional case can be obtained only by performing a treatment with cathode water including the treatment method of the present invention.

FIG. 9 shows the structure of a bipolar transistor element manufactured for explaining an application example of the cleaning method according to the first aspect of the present invention. p epi base layer 83 and n ⁺
The present invention was applied to the surface treatment with the layer 82. An n ⁺ collector layer 82 was formed on the n-type Si substrate 81, and a p epi base layer 83 was formed. After that, ap ⁺ poly lead layer 84, an n ⁺ poly lead layer 89, and an n ⁺ poly lead layer 85 were formed via an oxide film 86, and finally a collector electrode 87, a base electrode 88, and an emitter electrode 90 were formed.
Here, the surface treatment according to the present invention was applied to the surface treatment on the n ⁺ collector layer 82 immediately before the formation of the p-epi base layer 83.

FIG. 10 is an IV characteristic diagram showing the electric characteristics of the element shown in FIG. 9 when the Si surface between the base and the collector is treated according to the present invention. In FIG. 10, curves 901 and 902 show the cases where the collector-base voltage is high and low, respectively.

For comparison, FIG. 11 shows a conventional S
i − represents the electrical characteristics of the element when subjected to HF treatment and ordinary pure water treatment, which is a surface cleaning process
A V characteristic diagram is shown. A plurality of curves in FIG. 11 are respectively shown in FIG.
When the collector-base voltage is high as in 0 (90
3) and low (904).

In FIG. 11, deterioration of electrical characteristics, which is considered to be caused by leakage caused by surface residual contamination due to imperfect cleaning treatment between the base and the collector, is observed. The defective operation characteristic of the element caused by this deterioration causes the defective operation of the circuit configured using this element. on the other hand,
As shown in FIG. 10, when the cleaning process using the method according to the present invention is performed, this deterioration is significantly suppressed,
The effect of the present invention is shown.

Next, FIG. 12 is a schematic view showing an example of a treatment system in which cathode water and anode water according to a preferred embodiment of the present invention are mixed and used. As shown in FIG. 12, pure water 6 supplied from the pure water producing apparatus 1 is electrolyzed through the ion exchange membrane 5 by applying a voltage to the anode 3 and the cathode 4 in the electrolytic cell 2, Electrolyzed water 61, 62 respectively
Becomes

By disposing the gas-liquid separation device 211 on the anode side and the gas-liquid separation device 212 on the cathode side between the electrolytic cell 2 and the treatment tank 8, unnecessary gas generated in the electrolytic cell 2 is removed. be able to. In particular, oxygen generated by electrolysis makes the subsequent treatment incomplete. Therefore, although the degassing device 261 is provided on the gas-liquid separation device 211 on the anode side or is not shown in this figure, the gas-liquid separation device 211 is not shown. By appropriately disposing the degassing device and the degassing device between the electrolytic bath 2 and the treatment bath 8, respectively, the amount of dissolved oxygen can be controlled so as to be below a predetermined level. The level of dissolved oxygen is 0-300
When it is ppb, the oxidation of the Si wafer due to the action of oxygen can be prevented.

The obtained electrolyzed water 61, 62 is mixed through the switching valves 131, 132, and mixed electrolyzed water 63
And is introduced into the processing tank 8. In this processing tank 8,
The wafer 7 is held in the wafer case 9 and processed. In FIG. 12, the processing tank 8 is sealed by a lid 14,
It is discharged from the drain 15 provided in the processing tank 8 through the drain valve 16. Valves 131, 171, 132, and 172 of the switching valves 13, 17 respectively
By independently controlling the degree of opening and closing, the mixed electrolyzed water 63 supplied to the treatment tank 8 is mixed from both the anode water 61 and the cathode water 62 by an arbitrary amount in the range of 0 to 100%. Can be supplied.

If necessary, the hydrofluoric acid solution 12 in the hydrofluoric acid container 11 prepared in advance may be added to the electrolyzed water 6 via the valve 10 to remove the oxide film on Si in a desired step. However, the dissolved oxygen in the hydrofluoric acid solution 12 can also be removed, preferably by providing the degassing device 262 on the hydrofluoric acid container 11.

Further, by providing the treatment tank 8 with the lid 14 which can be sealed, it is possible to prevent dust, oxygen, carbon dioxide, etc. mixed from the atmosphere. In addition, the wafer 7 is treated in the processing tank 8
It is possible to carry out continuous processing without taking it out from.

The gas-liquid separator 2 on the anode side is used here.
Although the deaerator 261 is provided on the upper part 11, a gas adding means (not shown) may be provided between the electrolytic bath 2 and the processing bath 8 instead.

According to a preferred embodiment of the present invention, surface treatment of a wafer having a bare pattern formed by partially exposing an oxide film-coated silicon wafer is performed by using such a system, and anodic water 61 is used. By appropriately mixing the cathode water with the cathode water 62, it is possible to perform cleaning without generating water glass with the cathode water and remove residual impurities containing metal such as copper with the anode water at the same time. it can.

As described above, according to the preferred embodiments of the first and first aspects of the present invention, the semiconductor substrate can be effectively cleaned sufficiently by a more simplified method. As a result, the surface treatment of the bare pattern of the semiconductor substrate having the oxide film can be realized in a shorter number of steps than the conventional one. In addition to shortening the time required for the process,
It is possible to simplify the processing line, such as reducing the number of installation facilities and piping. Further, since the amount of chemicals used can be reduced, it is also effective from the viewpoint of environmental protection.

Furthermore, according to the preferred embodiments of the first and first aspects of the present invention, the cost of the processing apparatus can be reduced,
It is also possible to realize a higher performance element, and finally it is possible to reduce the manufacturing cost of the semiconductor device.

FIG. 13 is a schematic view showing an embodiment of a cleaning system to which the cleaning method according to the second aspect of the present invention can be applied. As shown in FIG. 13, this cleaning system mainly includes a pure water producing apparatus 301 and a pure water producing apparatus 301.
A pure water supply line 401 connected to the pure water supply line, a gas addition means 402 for adding a gas to the pure water provided on the pure water supply line 401, and a gas addition means 402 provided downstream and excessively added. A gas-liquid separator 304 for separating gas, an outlet 306 provided on the gas-liquid separator 304 for discharging the separated gas, and a gas-liquid separator 3
A line 403 connected to 04 for supplying a cleaning solution to which a gas is added, and a semiconductor substrate surface treatment apparatus 307 connected to the downstream side of the cleaning solution supply line 403.

In this apparatus, first, the pure water generator 301
The gas 303 introduced through the valve 302 provided in the gas addition means 402 is added to the pure water supplied from the pure water supply line 401 to dissolve the gas in the pure water to form a cleaning solution. . Next, the cleaning solution added with the gas is supplied to the gas-liquid separation device 304, so that the unnecessary gas 303 is discarded from the gas outlet 306 via the valve 305. After that, the cleaning solution from which the unnecessary gas is separated and removed passes through the supply line 403 and the surface treatment device 307.
It is led to. In the surface treatment apparatus 307, the wafer 309 in the wafer holder 308 installed therein is covered with the lid 31.
By 0, processing is performed while cutting off unwanted gas from the atmosphere. The used cleaning solution is the surface treatment device 30.
7 is discharged from the drain 311.

In this cleaning apparatus, the processing apparatus 307 is preliminarily charged with hydrofluoric acid-added water, and the wafer 309 is immersed therein to remove the natural oxide film on the wafer 309, and then the present invention is continuously applied. Performing a process is the process that can be expected to have the most reliable effect.

Hydrogen is suitable as the gas to be introduced. The dissolved hydrogen amount is ideally dissolved to a supersaturated concentration, but if 50 ppb or more is added, its effect can be expected, and it is actually preferable to dissolve it in the ppm order.

Instead of the pure water producing apparatus 301, an electric field ion water producing apparatus may be connected. The gas 303 is
It is sufficient to introduce a desired gas, but if the required amount is dissolved in the solution without containing air bubbles that may interfere with the process, or by optimizing the position of the wafer 309 in the surface treatment apparatus 307, etc. If a structure in which hydrogen gas is not supplied to the gas is realized, the gas-liquid separation device 30
4 is unnecessary. On the other hand, if the remaining hydrogen that cannot be completely dissolved in the solution diffuses in the solution and is supplied onto the wafer to adhere to the wafer surface and interfere with the cleaning process,
It is preferable to install a gas-liquid separator regardless of the amount of residual hydrogen. As for the amount of the gas 303, it is desirable to use a valve capable of adjusting the introduction flow rate in advance.

After the predetermined processing is completed, the surface treatment device 30
Draining the processing solution from the drain 311 provided in 7.
The wafer is dried. By adopting a structure in which the wafer processing solution is discharged to the drain 311 via the conductance valve 315, the hermeticity can be increased and the dissolved hydrogen gas concentration of the entire apparatus can be increased. Although the amount of dissolved hydrogen in the open air type processing apparatus without the lid 310 is on the order of ppm, it is possible to increase the dissolved concentration to twice the normal level by providing the conductance valve 315. As the dissolved concentration of hydrogen gas increases, the cleaning ability also improves.

Further, by opening the valve 313 separately provided in the surface treatment apparatus 307 and introducing the purge gas 314, it is possible to prevent the atmospheric air from being mixed and to suppress unnecessary oxidation from atmospheric oxygen. The pressure inside the processing container 317 is 10
^A pressure of ^-3 atm or higher is desirable, and the desired pressure is adjusted by the conductance valve 315, the valve 313, and the purge gas pressure. Highly pure hydrogen, nitrogen, argon, and helium are suitable as the purge gas. Pipes, processing vessels, etc. are made of glass (including quartz), PVC (hard vinyl chloride), PEEK (polyether ether ketone),
Can clean and clean the atmosphere from the outside such as PVDF (polyvinylidene fluoride), PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer), PVF (polyvinyl fluoride), PTFE (polytetrafluoroethylene), etc. It is preferable to manufacture it with a material that can secure the degree.

FIG. 14 is a graph showing the dependency of the amount of residual water glass on the Si surface treated by the cleaning method according to the second aspect of the present invention on the Si surface cleaning method. After the natural oxide film in the pattern of the Si substrate surrounded by the oxide film was treated with the HF solution, washed with pure water and then dried, the natural oxide film surrounded by the oxide film was removed. For example, 5x5
More than 10 oxides were observed on the bare Si pattern of μm ² . When this Si substrate was treated with an HF solution and immediately dried, a similar pattern was obtained.
No such oxide was observed. Finally, when the treatment of the present invention was performed on the same substrate, there was no oxide in the pattern, or only one oxide was observed.

As is clear from FIG. 14, according to the present invention, the amount of water glass that could not be removed on the surface after the conventional pure water treatment was removed without heating in a vacuum or complicated Wet treatment. , It is possible to reduce the residual amount to the same level as the Si surface after the HF treatment.

As described above, when the treatment according to the present invention is performed, it is possible to remove the oxides remaining on the Si substrate after the cleaning step, and the oxides generated during the process of cleaning to drying after cleaning.

FIG. 15 is a diagram showing another embodiment of a cleaning system to which the cleaning method according to the second aspect of the present invention can be applied. In this device, instead of the gas addition means 402 and the gas-liquid separation device 304, a gas supply port provided with a valve 322 and a gas discharge port 32 provided with a valve 325.
1 except that a bubbling device 324 having 6 is provided.
It has substantially the same configuration as the device shown in FIG.

Pure water supplied from the pure water producing device 321 is introduced into a bubbling device 324 which introduces a desired gas with a gas 323 introduced through a valve 322. By bubbling, the desired gas can be more reliably dissolved in the treatment liquid than in FIG. The unnecessary gas is discharged from the gas discharge port 326 via the valve 325. The treatment liquid thus prepared is treated in the same treatment solution as that shown in FIG. Instead of directly connecting the pure water producing device 321, an electric field ion water producing device may be connected. In this case, it is necessary to install a gas-liquid separator instead of the bubbling device 324 to remove unnecessary bubbles. There is.

FIG. 16 is a schematic view showing an example of a surface treatment apparatus to which the cleaning method according to the second aspect of the present invention can be applied. This surface processing apparatus has a wafer holder 341 on which a wafer 342 is installed, and an internal processing apparatus 343 connected to a cleaning solution supply line and an internal processing apparatus 343.
It is mainly configured by an external processing device which is provided in the vicinity of the above, a gas introduction port is provided in the upper part through a valve 346, and a drain 348 is provided in the lower part.

The wafer 342 stored in the wafer holder 341 is an internal processing container 343 capable of overflowing.
It is stored in and processed. This internal processing container 343
Is an external processing container 344 and a lid 34, which are arranged on the outside thereof.
It is cut off from the outside world by 5. In this figure, this lid 3
The purge gas 347 is introduced into the valve 45 through the valve 346, and the processing liquid and the purge gas are discharged from the drain 348. The same purge gas as that used in the apparatus shown in FIG. 13 can be used. In this configuration,
It is easy to replace pure water, and even if the degree of sealing of the apparatus itself is lower than that in FIG. 13, it is easier to structurally maintain the sealing function, and it can be said that this is a more practical processing apparatus. This device configuration is suitable when configuring an automated line or the like.

As described above, according to the cleaning method of the second aspect of the present invention, almost no silicon oxide is formed on the substrate by cleaning, and the surface treatment process of the semiconductor substrate at a low temperature is performed more than before. It can be performed in a short number of steps. As a result, not only the number of processing steps and time can be shortened, but also the number of installed facilities and the number of processing lines such as piping can be reduced by simplifying the processing lines themselves.

As described above, according to the present invention, cleaning of the surface of the semiconductor substrate can be realized more easily and safely, and a more effective cleaning method can be provided. Further, according to the present invention, a high-performance semiconductor device can be manufactured at low cost by using such a cleaning method.

[0085]

According to the present invention, almost no silicon oxide is formed on a substrate by cleaning, and the surface treatment process of a semiconductor substrate at a low temperature can be performed in a shorter number of steps than in the past. As a result, not only the number of processing steps and time can be shortened, but also the number of installed facilities and the number of processing lines such as piping can be reduced by simplifying the processing lines themselves.

As described above, according to the present invention, cleaning of the surface of the semiconductor substrate can be realized more easily and safely, and a more effective cleaning method can be provided. Further, according to the present invention, a high-performance semiconductor device can be manufactured at low cost by using such a cleaning method.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between solution pH and redox potential.

FIG. 2 is a graph showing the substrate cleaning ability after mixing anode water and cathode water.

FIG. 3 is a partial flow chart showing an example of a process in the case of treating by mixing cathode water and anode water.

FIG. 4 is a partial flowchart of conventional processing.

FIG. 5 is a partial flow chart when the anode water and the cathode water are separately supplied and treated.

FIG. 6 is a schematic diagram showing an example of a processing system according to a first aspect of the present invention.

FIG. 7 is a schematic diagram showing an example of a processing system according to a preferred embodiment of the first aspect of the present invention.

FIG. 8 is a graph showing the amount of residual water glass on the surface after cleaning the Si surface using the method of the present invention.

FIG. 9 is a schematic diagram showing the structure of a bipolar transistor device manufactured to explain an application example of the method according to the present invention.

10 is a graph showing the electrical characteristics of the bipolar transistor device shown in FIG.

FIG. 11 is a graph showing the electrical characteristics of a bipolar transistor element when HF treatment and normal pure water treatment are performed.

FIG. 12 is a schematic diagram showing an example of a processing system according to a preferred embodiment of the present invention.

FIG. 13 is a schematic diagram showing an example of a processing system according to a second aspect of the present invention.

FIG. 14 is a graph showing the dependency of the amount of residual water glass on the Si surface on the Si surface cleaning method.

FIG. 15 is a schematic diagram showing a part of another example of the processing system according to the second aspect of the present invention.

FIG. 16 is a schematic diagram showing a part of another example of the processing system according to the second aspect of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Pure water production apparatus 2 ... Electrolyte tank 3 ... Anode 4 ... Cathode 5 ... Ion exchange membrane 6 ... Pure water 61, 62 ... Electrolyzed water 71, 72 ... Wafer 91, 92 ... Wafer case 10 ... 0 ... 101 ... Cathodic water Range 102 ... range of anode water 111, 112 ... hydrofluoric acid container 121, 122 ... hydrofluoric acid solution 191, 192 ... valve 211, 212 ... gas-liquid separation device 221, 222 ... valve 231, 232 ... lid 261, 262 ... Deaeration means 801, 802 ... Treatment tank

Claims (12)

[Claims] 1. A bare pattern formed by partially exposing the surface of a semiconductor substrate coated with an oxide film is composed of pure water, a mixed solution of acid and pure water, and a mixed solution of alkali and pure water. In the method for cleaning a semiconductor substrate, which comprises a step of surface-treating with at least one cleaning solution selected from the group, the final cleaning step in the surface-treatment step is a solution obtained by electrolyzing the cleaning solution. Out of
A method for cleaning a semiconductor substrate, which is performed by using cathode water having a negative redox potential and having a pH of 7 to 13 while maintaining a dissolved oxygen concentration of 300 ppb or less. 2. The method according to claim 1, wherein an anode water obtained by electrolyzing the cleaning solution is further added to the cathode water. 3. The method according to claim 1, wherein the final cleaning step is performed in an inert gas atmosphere of 10 ⁻³ atm or more containing 10 ⁻⁶ to 100% of a reducing property-imparting gas. . 4. The method according to claim 3, wherein the reducing property-imparting gas is hydrogen or a hydrogen radical having an energy state different from that of hydrogen. 5. The method according to claim 3, wherein the inert gas is at least one selected from the group consisting of nitrogen, helium, and argon. 6. A bare pattern formed by partially exposing the surface of a semiconductor substrate coated with an oxide film is composed of pure water, a mixed solution of acid and pure water, and a mixed solution of alkali and pure water. In the method of cleaning a semiconductor substrate, which comprises a step of surface-treating with a cleaning solution selected from the group, in the final cleaning step of the surface treatment step, a reducing-imparting gas is used.
A method for cleaning a semiconductor substrate, which is performed by using a final cleaning solution added by bringing a gas component containing 0 ^-6 to 100% at 10 ^-3 atm or more into contact with the cleaning solution. 7. The method according to claim 6, wherein hydrogen and hydrogen radicals having an energy state different from that of hydrogen are used alone or as a mixture as the reducing property imparting gas. 8. The method according to claim 6, wherein cathode water having a negative redox potential obtained by electrolyzing the cleaning solution is used in the final cleaning step. 9. The method of manufacturing a semiconductor device according to claim 8, wherein anode water obtained by electrolyzing the cleaning solution is further added to the cathode water. 10. The dissolved oxygen concentration of the cleaning solution is set to 300.
The method according to claim 6, which is used while being maintained at ppb or less. 11. A means for supplying a cleaning solution selected from the group consisting of pure water, a mixed solution of pure water and an acid, and a mixed solution of pure water and an alkali, wherein the cleaning solution is at least 10 ⁻³ atm. Means for introducing a gas component containing 10 ⁻⁶ to 100% of a reducing property-imparting gas, and adding the reducing property-imparting gas to the cleaning solution, and cleaning to which the reducing property-imparting gas is added An apparatus for cleaning a semiconductor substrate, comprising means for surface-treating a bare pattern formed by partially exposing the surface of the semiconductor substrate coated with an oxide film using a solution. 12. The apparatus according to claim 11, further comprising pressurizing means for pressurizing at least the gas component to dissolve it in the cleaning solution.