JPH06177102A - Method and equipment for cleaning surface of compound semiconductor - Google Patents

Abstract

(57) [Abstract] [Purpose] When cleaning the surface of a compound semiconductor, avoid formation of an altered layer near the crystal surface by conventional high-temperature treatment or high-energy treatment such as ion irradiation.
Forming a low-pollution compound semiconductor surface. [Structure] Ultrapure pure water having a high resistance value of 17 MΩ · cm or more in the atmosphere of high purity inert gas or high purity hydrogen gas, or the dissolved oxygen concentration of ultrapure water is substantially 0.
A method and an apparatus for cleaning a surface of a compound semiconductor, which cleans the surface of the compound semiconductor substrate after the chemical etching treatment by using pure water of 2 ppm or less, or simultaneously performs ultrasonic cleaning.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for cleaning a compound semiconductor surface (low defect, low oxide and low contamination).

[0002]

2. Description of the Related Art Conventionally, in order to remove oxides and contaminants remaining on the surface of a compound semiconductor and clean the surface of the substrate, high energy treatment such as electron beam, laser, ion irradiation, high temperature heating, or halogen-based gas is used. Techniques such as vapor-phase etching using s have been tried.

[0003]

However, since the formation energy of the crystal defects of the compound semiconductor is extremely small, these methods produce an altered layer containing many crystal defects in the vicinity of the crystal surface. For example, in the high temperature heating method, InP, G
The P or As atom in the aAs crystal is approximately 300 to 400 ° C.
Dissociates and evaporates at this temperature, and a heat-altered layer occurs near the surface. Further, the vapor phase etching method using a halogen gas (HCl etc.)
It is necessary to heat to a high temperature in order to remove the reaction product after etching, and the formation of a thermally deteriorated layer cannot be avoided.

A number of crystal defects are contained in the altered layer formed during the cleaning process of the surface of the substrate, and the crystal defects cause the formation of scatterers of surface conduction electrons, recombination centers, and surface levels, and thus compound semiconductors. There is a problem that the performance of the device using the surface is significantly deteriorated.

The method of cleaning a compound semiconductor surface of the present invention avoids the formation of an altered layer in the vicinity of the crystal surface by the conventional high temperature treatment, high energy treatment such as ion irradiation, and is a compound with low defects, low oxides and low contamination. Forming a semiconductor surface.

[0006]

In order to achieve the above object, the first invention is a super-purity having a high specific resistance value of 17 MΩ · cm or more in a high-purity inert gas or high-purity hydrogen gas atmosphere. A compound semiconductor characterized in that the natural oxide on the surface of the compound semiconductor is removed by cleaning the surface of the compound semiconductor substrate after the chemical etching treatment with running pure water, or simultaneously performing ultrasonic cleaning. The method of cleaning the surface is the subject of the invention.

The second aspect of the invention is to clean the surface of the compound semiconductor substrate after the chemical etching treatment with running pure water having a high specific resistance value of 18 MΩ · cm or more in a high purity gas atmosphere, or At the same time, ultrasonic cleaning is performed to remove natural oxides on the compound semiconductor surface,
In the method capable of forming a low-defect, low-oxide and low-contamination surface, the dissolved oxygen concentration of the ultrapure water is substantially 0.2.
The present invention is directed to a method for cleaning a compound semiconductor surface, which is characterized in that the content of the compound semiconductor is controlled to be at most ppm, thereby suppressing the oxidation of the compound semiconductor surface.

Further, according to the present invention, a chemical processing chamber having a solution tank for storing a chemical etching solution and capable of containing a substrate therein, a glove box chamber arranged via the chemical processing chamber and a gate valve are provided. The glove box chamber and an antechamber arranged via a gate valve are provided, and each of the chemical treatment chamber, the glove box chamber and the antecedent chamber has an inert gas or hydrogen gas line and an exhaust line. The subject of the invention is an apparatus for cleaning the surface of a compound semiconductor.

[0009]

In the present invention, since the chemical etching treatment is a low energy process, the surface of the compound semiconductor after the treatment is a low defect surface, and the oxide of the constituent elements formed on the compound semiconductor surface is high purity pure water. It utilizes the fact that it is soluble or unstable in running water, and the surface of the substrate is cleaned by washing the surface of the compound semiconductor substrate after the chemical etching treatment with running water of ultrapure pure water having a high specific resistance value. It can completely escape the formation of oxides or surface contamination.

Further, in the present invention, the deterioration of the reproducibility of the clean surface formation by the ultrasonic-ultra pure water cleaning treatment is caused by the formation of oxides due to the dissolved oxygen concentration in the ultra-pure water during the ultrasonic-ultra pure water cleaning treatment. It is based on the fact that it is possible to suppress the formation of oxides during and after ultrasonic-ultra pure water cleaning treatment by reducing the dissolved oxygen concentration in ultra pure water based on the fact that According to the invention, it is possible to form a clean compound semiconductor surface free of oxide with good reproducibility.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the first invention will be described. FIG. 1 shows a processing apparatus for cleaning the surface of a compound semiconductor of the present invention.

This processing apparatus has a structure consisting of a front chamber 9, a glove box chamber 8 and a chemical treatment chamber 7, and each chamber is partitioned by a gate valve 10. Each chamber is provided with an inert gas (for example, nitrogen, argon, helium gas, etc.) line or hydrogen gas line 1, and further has a vacuum pump line 12 and an exhaust line 13 for forced exhaust. The inert gas or hydrogen gas passes through the adsorbent and the purification device and is highly purified to a residual oxygen concentration of several tens of ppb. If the inert gas, hydrogen gas line and forced exhaust line are used, the oxygen concentration remaining in the chemical treatment chamber 7, the glove box chamber 8 and the front chamber 9 can be reduced to several 1 in a short time of about 1 hour.
It can be reduced to about 0 ppm.

The glove box chamber 8 can be connected to a manufacturing apparatus such as an MBE apparatus, an analysis apparatus such as an XPS apparatus, or a transfer box for transportation via a gate valve, and the compound semiconductor substrate 5 is exposed to the atmosphere. It can be introduced into the above device without exposure.

A chemical etching solution and high-purity pure water having a specific resistance value of 17 mΩ · cm or more can be continuously introduced into the solution tank 4 in the chemical treatment chamber 7 through the introduction lines 2 and 3. is there. The solution tank 4 also has a cleaning function using ultrasonic waves of about 38 kHz. As the chemical etching solution, not only acids such as hydrochloric acid and nitric acid but also alkaline solutions such as ammonia solution can be used. These chemical etching solutions are designed to reduce the amount of dissolved oxygen by defoaming treatment under a low vacuum and prevent the inclusion of oxygen by enclosing an inert gas.

The compound semiconductor substrate 5 is placed in a cage 6 made of quartz or platinum and introduced into the antechamber 9, and the oxygen concentration in the antechamber 9 is about 100 ppm using a vacuum pump line and a forced exhaust line. After decreasing to several tens of ppm
Is introduced into the glove box chamber 8 and the chemical treatment chamber 7, which are kept in an extremely low oxygen concentration atmosphere. The compound semiconductor substrate 5 in the chemical processing chamber 7 is etched by the chemical etching solution in the solution tank 4 and then washed with running high-purity pure water. At this time, the defect layer, the altered layer and the oxide on the surface introduced during the polishing of the substrate are removed to form a low defect surface. After the chemical etching treatment, pure water with high purity and high resistance is continuously introduced into the solution tank 4 and washed under running water, so that not only the acid or alkali solution remaining on the surface of the compound semiconductor substrate 5 but also the surface remains. The oxide can be completely removed. By using the ultrasonic cleaning function of the solution tank 4 at the same time as the high-purity pure water cleaning, it is possible to more effectively remove the oxides remaining on the surface in a shorter time as compared with the pure water cleaning.

The surface of the compound semiconductor substrate 5 cleaned by the chemical etching treatment and the ultrapure water cleaning is a low defect surface and a low oxide surface, and is handled in an atmosphere with an extremely low oxygen concentration of several tens of ppm. Oxidation can be avoided. When a hydrogen gas atmosphere is used, it becomes possible to perform passivation to prevent surface contamination due to adsorption of hydrogen molecules on the cleaned surface. The compound semiconductor substrate 5 after the cleaning process is directly connected to the glove box chamber 8 without being exposed to air.
It is used by being installed in a manufacturing apparatus such as a BE apparatus, a MOCVD apparatus, a CVD apparatus or an analyzing apparatus such as XPS.

Next, the cleaning effect on the surface of the compound semiconductor substrate according to the present invention will be specifically described by taking a GaAs crystal as an example. 2 (a) and 2 (b) show an etching process using a sulfuric acid-based etching solution {a mixed solution of sulfuric acid, hydrogen peroxide and water (5: 1: 1)} and a cleaning with dilute hydrochloric acid.
It is the measurement result of the angle-resolved X-ray photoelectron spectroscopy analysis (AR-XPS: the angle between the analysis tube and the GaAs substrate is 15 °) of the GaAs crystal surface exposed to the air. (A) shows As, and (b) shows Ga.

FIGS. 2 (c) to 2 (f) show G cleaned using the processing apparatus shown in FIG. 1 after the etching treatment with the above etching solution, followed by cleaning with dilute hydrochloric acid and running with high resistance pure water.
The result of AR-XPS analysis of aAs surface is shown. The analysis depth is a few Å from the surface. The pure water cleaning time is shown in Fig. 2 (c).
(D) is 1 hour, (e), (f) is 3 hours.
(C) and (e) are As, and (d) and (f) are Ga.
The results of analysis are shown below. As shown in FIGS. 2A and 2B, in addition to the Ga and As peaks of the substrate, the XPS signal on the surface of the GaAs crystal exposed to the air also contains Ga ₂ O ₃ and As.
An oxide peak of ₂ O ₃ is recognized, and it can be seen that the surface oxide is composed of Ga and As oxides. The intensity of the As oxide peak was reduced by washing with high-purity pure water (Fig. 2).
(C)) After 3 hours of cleaning (FIG. 2 (e)), it becomes almost zero. On the other hand, the Ga ₂ O ₃ oxide peak gradually decreases as the pure water cleaning time increases. The above facts are based on As ₂ O ₃
It is shown that the oxide is soluble in water and can be removed by washing with pure water, and Ga oxide is also unstable in pure water.

As and Ga oxides on the GaAs surface are
By performing the ultrasonic cleaning at the same time as the ultrapure water cleaning, the removal can be performed more efficiently and in a short time. Figure 3 (a),
(B) is an AR-XPS signal on the GaAs crystal surface when ultrasonic cleaning at 38 kHz was performed for 20 minutes in addition to ultrapure water cleaning. 3C and 3D show the case where ultrasonic cleaning is performed for 1 hour. Note that (a) and (c) show As, and (b) and (d) show Ga. By ultrasonic cleaning, the As oxide is completely removed in about 20 minutes, and the Ga oxide is also completely removed in about 1 hour.

However, when the compound semiconductor is washed with running pure water having a low resistance value, the oxide remaining on the surface cannot be completely removed after the chemical treatment. Specific examples are shown in FIGS. Figures (a) and (b) show As ₃ d (a) and Ga ₃ d (b) after cleaning a GaAs substrate with running pure water having a resistance value of 15 MΩ · cm for about 1 hour.
XPS signal (angle between beverage and detector: θ ~ 1
5). Also, (c) and (d) are resistance values of 9 MΩ · c.
When the substrate is washed with running pure water of m for 1 hour,
(C) shows As and (d) shows Ga. Clearly from the figure, unlike the case of cleaning with pure water due to the high resistance value, even if the cleaning is performed for 1 hour, in addition to Ga oxide (Ga ₂ O ₃ ), A
It can be seen that the s oxide (As ₂ O ₃ ) also remains on the surface. When pure water having a low resistance value is used, this As oxide is
It cannot be removed even by washing for a long time of 1 hour or more.

The resistance value of pure water itself is determined by the contribution of electrons of water molecules and impurity ions in pure water. In the ideal case where impurity ions are not included, the resistance value of pure water is 25 ° C.
Is about 18.2 MΩ · cm. When impurities are included, the resistance value of pure water is due to conduction of impurities.
It is lower than this value. When pure water is left in the air, the pure water mainly absorbs CO ₂ gas in the air, so that the resistance value of the pure water decreases. The absorbed carbon dioxide gas increases the oxidation reaction on the surface of the compound semiconductor. In the case of cleaning with pure water having a low resistance value, since this oxidation reaction coexists with the effect of removing oxides, even if cleaning is performed for a long time, the oxides on the surface cannot be completely removed.

As described above, according to the present invention, unlike the conventional surface cleaning method, it is possible to form a compound semiconductor surface having low defects, low oxides and low contamination. Although a GaAs crystal has been taken up and described as a specific example of the present invention, other InP, InSb, InAs forming a soluble oxide may be used.
III-V compound semiconductors such as GaInP and GaInAs of these mixed crystal materials can also achieve low defects, low oxides, and low contamination surfaces.

Next, the second invention will be described. As a method of forming a clean surface on a compound semiconductor and reducing the number of crystal defects in the vicinity of the surface, a method of performing ultrasonic (˜38 kHz) cleaning in flowing water of ultrapure water having a high resistance value (hereinafter ultrasonic wave -It is called ultrapure water cleaning and abbreviated as U-RDIW) is proposed. Since this method uses only the etching treatment with a chemical etchant and the treatment with running ultrapure water under the application of ultrasonic waves to clean the surface of the compound semiconductor, the formation of crystal defects during the treatment is small and low. It is possible to form a defect density surface. Since the surface is washed with ultrapure water having a high resistance value, that is, an extremely low impurity ion concentration, it is possible to form a clean surface with extremely low contamination. By applying ultrasonic waves, the effect of removing impurity ions and oxides is increased, and a clean surface can be formed in a shorter time. It has features such as.

As described above, the U-RDIW cleaning has a major feature of forming a clean surface having a low defect density, as compared with the conventional cleaning method using high temperature heating and high energy treatment such as plasma. . This reflects that the U-RDIW process essentially uses only low energy processes. However, this U-RDIW treatment has poor reproducibility in terms of forming a clean surface on which no oxide remains.
When the U-RDIW cleaning for several hours is applied to the III-V group compound semiconductor, the oxide containing the V group element among the III-V group containing the III group and V group elements formed on the surface is exposed on the semiconductor surface. Although not remaining, the oxide containing the group III element may remain on the surface for a fraction of the atomic layer in terms of the average film thickness. As a specific example, in FIG. 6, GaAs crystal is subjected to U-RDIW cleaning {Pure water resistivity: 18.0 MΩ · c
m, flow rate per unit area: 0.5 L / cm ² · min, dissolved oxygen concentration (DO) of pure water: 4 to 5 ppm}, angle-resolved X-ray photoelectron spectroscopy analysis (AR-XPS:
The angle between the analysis tube and the GaAs substrate is 15 °, and the analysis depth is several Å).

FIGS. 6A and 6B show the results of AR-XPS analysis of the etching treated surface before the U-RDIW treatment. The GaAs crystal after the U-RDIW treatment was AR-treated through a nitrogen atmosphere in order to avoid surface oxidation in the atmosphere.
-I brought it to XPS. 6 (c), (d),
(E), (f) and (g), (h) are U after etching (sulfuric acid, hydrogen peroxide, water (mixed solution of 5: 1: 1)).
It is the result of AR-XPS analysis of the GaAs surface that has been subjected to -RDIW treatment.

The processing time of U-RDIW is 20 minutes in (c) and (d) of FIG. 6, 40 minutes in (e) and (f), and 60 minutes in (g) and (h). From the figure, As oxide (As ₂ O ₃ ) formed during chemical etching
And Ga oxide (Ga ₂ O ₃ ) ((a) and (b) of FIG. 6).
As) oxide, U-RDIW of 20 minutes or more
It can be seen that it can be completely removed by the treatment (see (c) of FIG. 6). However, in the U-RDIW treatment for 60 minutes (see (h) of FIG. 6), Ga oxide remains on the surface in an amount of 0.2 to 0.5Å in terms of the average film thickness. This G
The a-oxide is a fraction of the number even after several hours of U-RDIW treatment.
While it may remain on the surface in the order of atomic layer, it may be completely removed by the U-RDIW treatment within 1 hour. Therefore, when the U-RDIW process is actually used as a method for cleaning the surface of a compound semiconductor, improvement of reproducibility of clean surface formation has been a serious problem.

Ultrapure water contains about several ppm (maximum dissolved oxygen amount at 25 ° C. is about 8 ppm) of oxygen.
In the -RDIW treatment, an oxidation process by dissolved oxygen in ultrapure water and an oxide removal process by the U-RDIW treatment coexist. Generally, the oxide containing the group V element is soluble, and the removal rate of the oxide by the U-RDIW treatment is higher than the oxide formation rate by the dissolved oxygen. Therefore, V
The oxide containing a group element can be removed from the surface in a short time. On the other hand, the oxide containing the group III element is hardly soluble, and the removal rate by the U-RDIW treatment is low. The formation rate of an oxide containing a group III element by dissolved oxygen is UR
When the removal rate is less than that of the DIW treatment, the oxide containing the group III element on the surface gradually decreases. But,
When the amount of oxide on the surface decreases and the ultrapure water comes into direct contact with the semiconductor surface, the oxide formation rate due to dissolved oxygen competes with the removal rate, so the oxide is not removed and remains on the surface. Become. Furthermore, even on cleaned surfaces, U
-After completion of the RDIW treatment, a state of being held in static ultrapure water occurs, so that the surface is oxidized by dissolved oxygen.

The problem of reproducibility of clean surface formation by the U-RDIW treatment is caused by the variation in the amount of dissolved oxygen in the ultrapure water. Therefore, if it is possible to reduce the amount of dissolved oxygen in ultrapure water and suppress the surface oxidation reaction due to dissolved oxygen, it is considered possible to improve the reproducibility of clean surface formation.

Ultrapure water is obtained by passing through a filter containing an ion exchange resin in an ultrapure water production apparatus. At this time, non-ionized oxygen molecules are removed even if they pass through the ion exchange resin. Not done. 4 for ultrapure water at room temperature
About 5 ppm of oxygen is still dissolved in pure water even after passing through the ion exchange resin. As a method for reducing the amount of dissolved oxygen in the ultrapure water, bubbling with an inert gas (or hydrogen gas), vacuum deaeration, heating, or reaction of dissolved oxygen in pure water with active hydrogen to form water molecules A method of removing it can be considered. Here, bubbling of an inert gas, which is a simple method, is taken up and U-RDIW of GaAs crystal is taken up.
The effect of reducing the dissolved oxygen concentration on the treatment is shown. The details will be described below.

FIG. 7 shows a method for producing ultrapure water having a low dissolved oxygen concentration when bubbling with an inert gas is used. The inert gas (for example, nitrogen, argon, helium) or hydrogen gas is passed through the filter 15 and the oxygen adsorbent 16 connected to the inert gas line 14 to have a low particle concentration and a low oxygen concentration, and thus an ultra pure gas. It is introduced into a water tank 17 provided immediately before the water producing device 19.
The primary pure water in the water tank 17 is bubbled by this gas to have a low dissolved oxygen concentration. Gas check valve 18 at the top of the tank
Is installed to prevent the release of inert gas caused by bubbling and the backflow of air into the aquarium. The primary pure water having a low dissolved oxygen concentration in the water tank is provided with high resistance and high purity by passing through an ultrapure water producing apparatus that is closed to the atmosphere.

FIG. 8 shows the relationship between the dissolved oxygen concentration value (DO) and resistance value (ρ) of ultrapure water obtained by the above method and the bubbling time of nitrogen gas. The flow rate of nitrogen gas and the amount of primary pure water in the water tank are each about 10L.
It is about 170 L / min. As is clear from FIG. 8, the dissolved oxygen value in the ultrapure water is about 30% from the initial value of 4 to 5 ppm.
It can be seen that the bubbling of nitrogen gas for a minute drastically reduces it to 1 ppm or less, and to 60 ppm or more, it is reduced to about 0.2 ppm or less. This is because oxygen in the ultrapure water is taken into the nitrogen gas by the partial pressure of the gas and is discharged together with the nitrogen gas. At this time, the resistance value of the ultrapure water was a substantially constant value (up to 18.0 M) despite the rapid decrease in the dissolved oxygen concentration value.
Ω · cm), and shows that ultrapure water does not largely depend on the dissolved oxygen concentration value of about several ppm or less when it has a high resistance value of 18 MΩ · cm or more. This is considered to be because the resistance value of ultrapure water is mainly due to ionized impurities and the contribution of ionization of dissolved oxygen is small.

Ultrapure water (DO
≦ 0.2 ppm, 18.0 MΩ · cm, 0.5 L / cm
In the case of performing U-RDIW treated with ^2-minute) AR-
The XPS analysis result is shown in FIG. 5 (a) and 5 (b) are AR-X of the etched surface before U-RDIW processing.
It is a result of PS analysis. (C) and (d) are U-RDIW
Processing time is 20 minutes, (e), (f) is 40 minutes,
(G) and (h) are 60 minutes. In this (a),
(C), (e), (g) are As, (b),
(D), (f), (h) are shown for Ga.
From this result, the soluble As oxide (As ₂ O ₃ ) was
It was removed by U-RDIW treatment within about 20 minutes (Fig. C), and the insoluble Ga oxide (Ga ₂ O ₃ ) was removed by about 60.
It can be seen that it is completely removed by the U-RDIW treatment within minutes (Fig. H). This clean surface from which As oxides and Ga oxides have been removed can be formed with good reproducibility, unlike the conventional case of using ultrapure water containing several ppm of dissolved oxygen.

If the dissolved oxygen concentration in pure water exceeds 0.2 ppm, it is not preferable from the viewpoint of reproducibility to obtain a compound semiconductor surface with low defects, low oxides and low contamination.

As described above, when the concentration of dissolved oxygen in ultrapure water is reduced and the ultrapure water-ultrasonic cleaning treatment is applied to the compound semiconductor as in this embodiment, low defects, low oxides,
It is possible to form a cleaned surface with low contamination with good reproducibility. Although a GaAs crystal has been taken up and described as a specific example of the present invention, the effect of an oxide on reducing the dissolved oxygen concentration is III-V of other InP, InSb, InAs and the like.
Group compound semiconductors, GaInP of these mixed crystal materials,
The same applies to GaInAs and the like, and by using the method of the present invention, a low-defect, low-oxide, low-contamination surface can be formed on the compound semiconductor surface with good reproducibility.

Here, the method for reducing the concentration of dissolved oxygen in ultrapure water by bubbling the inert gas once has been described. However, "bubbling is performed in multiple stages by connecting water tanks" or "inert gas and water". It is possible to further reduce the oxygen concentration in the ultrapure water by taking measures such as "increasing the contact area with". Also, other low dissolved oxygenation methods, for example, “vacuum degassing” or “method of reducing dissolved oxygen by reacting dissolved oxygen in pure water with active hydrogen to form water molecules” and the like can be used. Similar to the bubbling method, it is possible to form a clean surface with good reproducibility.

[0036]

As described above, according to the present invention, by using ultrapure pure water, the surface of the compound semiconductor substrate after the chemical etching treatment is cleaned, or ultrasonic cleaning is performed at the same time. Since the semiconductor surface is cleaned only by the surface treatment and the cleaning process with ultrapure water, and the substrate is handled in a low oxygen atmosphere, it is possible to form a compound semiconductor surface with low defects, low oxides, and low contamination. .

The compound semiconductor surface cleaned according to the present invention has the following advantages. That is, since the surface has low defects, low oxide, and low contamination, the process of forming the insulator and cleaning the surface before the crystal growth is unnecessary, and the formation of the crystal defect by the conventional method can be avoided. For example, GaA
In the s crystal, it was necessary to raise the temperature of the substrate to 600 ° C. or higher in order to remove the oxide, and the formation of crystal defects was unavoidable. In addition, since the surface has low defects, low oxides, and low contamination, it is possible to suppress surface roughness such as hillrock and lower the growth temperature.

Further, in a high purity gas atmosphere, 1
By cleaning the surface of the compound semiconductor substrate after the chemical etching treatment with flowing pure water having a high specific resistance value of 8 mΩ · cm or more, or simultaneously performing ultrasonic cleaning,
In a method capable of removing a natural oxide on the surface of a compound semiconductor to form a surface having low defects, low oxide and low contamination, the dissolved oxygen concentration of the ultrapure water is reduced to substantially 0.2 ppm or less, By suppressing the oxidation of the surface,
Since it is possible to suppress the formation of oxides during the ultrasonic-ultra pure water cleaning process, it is possible to form a compound semiconductor surface with low defects, low oxides, and low contamination with good reproducibility.

In other words, since it is possible to reproducibly form a low-defect, low-oxide, low-contamination surface on the compound semiconductor surface cleaned by the present invention, it is possible to clean the compound semiconductor surface by U-RDIW treatment. It can be expected to improve reliability. Regarding crystal growth, it suppresses surface roughness such as hillocks and improves reproducibility of decrease in crystal growth temperature.

When the method of the present invention is applied to a field effect device such as a MISFET or HEMT, a surface (or an interface) having few interface state densities, recombination centers and scatterers due to the surface oxide is removed. It is possible to form with good reproducibility. Also in an optical element such as a semiconductor laser, there is an advantage that the surface state density due to the surface oxide is reduced to prevent the reduction of the surface dark current, and the improvement of the element characteristic can be achieved with good reproducibility.

[Brief description of drawings]

FIG. 1 shows an apparatus used in the first invention.

FIG. 2 is a diagram for explaining the effect of the first invention,
(A) and (b) are XPS of GaAs crystal surface exposed to the atmosphere after etching with a mixed solution of sulfuric acid, hydrogen peroxide and water.
As a result of the analysis, (c) and (d) show A of the GaAs crystal surface 1 hour after the cleaning treatment with running water of high-purity pure water.
As a result of R-XPS analysis, (e) and (f) show G after 3 hours.
The result of AR-XPS analysis of the aAs crystal surface is shown.

FIG. 3 is a diagram for explaining the effect of the present invention, in which ultrasonic cleaning at 38 kHz is performed simultaneously with high-purity pure water cleaning (a) and (b).
For 20 minutes and (c) and (d) for 1 hour.
The result of AR-XPS analysis of the s crystal surface is shown.

4A and 4B show a resistance value of 15 MΩ · cm,
(C) and (d) show the results of XPS signal analysis after the GaAs substrate was washed with running pure water having a resistance value of 9 MΩ · cm for 1 hour.

FIG. 5 is a diagram for explaining the effect of the second invention, (a),
(B) shows the result of XPS analysis of the GaAs crystal surface exposed to the atmosphere after etching, and (c) to (h) show ultrapure water whose dissolved oxygen concentration value was 0.2 ppm or less by bubbling nitrogen gas. G after performing U-RDIW processing using
The results of AR-XPS analysis on the surface of aAs show that (c),
U-RDIW processing time of (d) is 20 minutes, (e),
(F) shows the case of 40 minutes, (g), (h) shows the case of 1 hour.

FIG. 6 shows the results of AR-XPS analysis of the surface of a GaAs crystal that has been cleaned using conventional ultrasonic-ultra pure water cleaning. (A) and (b) show sulfuric acid before U-RDIW treatment. ，
After the etching with the mixed solution of hydrogen peroxide and water, the result of XPS analysis of the GaAs crystal surface exposed to the atmosphere, (c),
(D) is an etching process, followed by washing with pure water for 20 minutes, (e) and (f) for 40 minutes, and (g) and (h) for 60 minutes.
It is a result of AR-XPS analysis of the GaAs crystal surface after the minute. In this case, the dissolved oxygen concentration in the ultrapure water is about 4-5 pp.
m.

FIG. 7 shows a method for producing ultrapure water having a low dissolved oxygen concentration when bubbling with an inert gas is used.

FIG. 8 shows the relationship between the dissolved oxygen concentration (DO) value and the resistance value (ρ) of ultrapure water with respect to bubbling time when nitrogen gas is used as an inert gas.

[Explanation of symbols]

1 High-purity inert gas, hydrogen gas line 2 High-purity pure water supply line 3 Chemical etching solution supply line 4 Solution tank 5 Compound semiconductor substrate 6 Quartz or platinum cage 7 Chemical treatment chamber 8 Glove box chamber 9 Front chamber 10 Gate valve 11 Ejection Plug 12 Vacuum Pump Line 13 Exhaust Line 14 Inert Gas (eg Nitrogen, Argon, Helium) or Hydrogen Gas Line 15 Gas Filter 16 Oxygen Adsorbent 17 Primary Pure Water Tank 18 Gas Check Valve 19 Ultra Pure Water Production apparatus

Claims (3)

[Claims] 1. A surface of a compound semiconductor substrate after chemical etching treatment is performed in a high-purity inert gas or high-purity hydrogen gas atmosphere by using running water of ultra-pure pure water having a high specific resistance value of 17 MΩ · cm or more. A method for cleaning a surface of a compound semiconductor, comprising removing natural oxides on the surface of the compound semiconductor by cleaning or simultaneously performing ultrasonic cleaning. 2. In a high purity gas atmosphere, 18 MΩ
・ Natural oxides on the compound semiconductor surface can be removed by cleaning the surface of the compound semiconductor substrate after the chemical etching treatment with flowing pure water having a high specific resistance value of cm or more, or by simultaneously performing ultrasonic cleaning. In a method capable of removing and forming a low-defect, low-oxide and low-contamination surface, the dissolved oxygen concentration of the ultrapure water is substantially reduced to 0.2 ppm or less,
A method for cleaning a surface of a compound semiconductor, characterized in that the oxidation of the surface of the compound semiconductor is thereby suppressed. 3. A chemical processing chamber having a solution tank for storing a chemical etching liquid and capable of containing a substrate therein, a glove box chamber arranged via the chemical processing chamber and a gate valve, and the glove box. A chamber and an antechamber arranged via a gate valve, and each of the chemical treatment chamber, the glove box chamber and the antechamber has an inert gas or hydrogen gas line and an exhaust line. Semiconductor surface cleaning equipment.