JPH07307332A - Surface cleaning method and thin film forming method - Google Patents

Abstract

PURPOSE:To obtain a clean surface wherein surface irregularity due to vapor growth on a clean surface generated by the cleaning treatment of a substrate, is not generated, and reduction spots are not present. CONSTITUTION:A plasma generating chamber 1 and a reaction chamber 2 are connected via an aperture plate 3. The pressure in the reaction chamber 2 is set higher than or equal to about 0.1Pa. The pressure in the plasma generating chamber 1 is set 10-100 times the pressure in the reaction chamber 2. As the result, the plasma leaks from the plasma generating chamber 1 to the reaction chamber 2. A wafer 4 is set on a susceptor in the reaction chamber 2, and heated at about 600 deg.C or higher with a heater 8. After H2 is supplied to the reaction chamber 1 from a gas introducing port 9 and plasma is generated, a small amount of SiH4 is supplied to the reaction chamber 2 from a gas introducing port 10. The supplied SiH4 is decomposed and excited by the plasma in the reaction chamber 2, and reduces an oxide film on the wafer 4 surface.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cleaning the surface of a substrate or a film such as a semiconductor or a metal which is easily oxidized, and a thin film forming method for forming a thin film on the surface thereof, particularly in the manufacturing process of a semiconductor integrated circuit. The present invention relates to a surface cleaning method and a thin film forming method applied to form a clean semiconductor surface.

[0002]

2. Description of the Related Art There are some processes in the manufacturing process of semiconductor integrated circuits which require an extremely clean semiconductor surface.
Typical examples of the process are a process of epitaxially growing a semiconductor film of the same kind or different kinds or a metal film on the surface of a single crystal semiconductor substrate, a metal film is deposited on the surface of a semiconductor to which an impurity is added, and ohmic junction or Schottky There is a step of forming a bond. For example, silicon (Si), germanium (Ge), or a compound semiconductor is easily oxidized and forms an oxide film on the surface when exposed to moisture or oxygen. Since this oxide film hinders epitaxial growth and formation of ohmic contact, it is necessary to remove it before depositing the film. Whether the surface is cleaned or not is an important factor that determines the quality of epitaxial growth and ohmic junction.

As a method of cleaning the surface using a reducing gas, conventionally, a method of exposing the surface to hydrogen (H ₂ ) plasma or hydrogen radicals or heating the surface to produce silane (Si
A method of flowing H ₄ ) gas (Japanese Patent Laid-Open No. 3-224223) has been proposed. If the surface of silicon is oxidized to form silicon dioxide (SiO ₂ ), Si
The chemical reaction when reduction is caused by H ₄ is considered to be SiH ₄ (g) → Si + 2H ₂ (g) (1) SiO ₂ (s) + Si → 2SiO (g) (2). Note that in these equations,
s represents a solid and g represents a gas. Decomposition of SiH ₄ is not active at low pressures but only at relatively high temperatures. Further, silicon monoxide (SiO) is a solid at room temperature and sublimes at a relatively high temperature. Therefore (1)
The reaction of the equation becomes active when the substrate temperature is high to some extent (about 600 ° C. or higher). As a method very similar to the method using SiH ₄ described above, a method of supplying silicon vapor to the substrate surface in a high vacuum has been proposed. The reduction reaction on the surface in this case is represented by the formula (2).

[0004]

However, the method using hydrogen plasma has a problem that the plasma generation output must be increased in order to increase the concentration of active species and that cleaning takes time. was there. The generated output of large plasma destroys the thin gate oxide film used in a large scale integrated circuit. Further, the method using silane gas causes local unevenness in the reduction, so that a portion that is reduced early and a portion that is reduced later are generated. There is a problem that chemical vapor deposition (CVD) of silicon occurs in the formed portion, and since silicon grows at a relatively high deposition rate, unevenness occurs on the surface.

Further, in the method using silicon vapor, a resistance heating device, an electron beam heating device or a sputtering device for heating and evaporating silicon is installed in the reaction chamber of the CVD device or a vacuum chamber connected to the reaction chamber, and the substrate is used. If CVD is subsequently performed after cleaning the surface, there is a problem in that the source gas and its decomposition products are contaminated, and the above-mentioned silicon evaporation means does not operate normally. It is possible to solve the above-mentioned problem of contamination by installing a vacuum valve between the silicon evaporation means and the CVD device and closing the vacuum valve when performing CVD. In order to
A new evacuation device for maintaining the silicon evaporation means in a high vacuum is newly required, which causes a problem that the device becomes complicated and large. There is also a problem that particles are attached to the surface of the substrate by opening and closing the valve. Further, it is expected that it is extremely difficult to control the evaporation rate of silicon to a predetermined extremely small speed while maintaining spatial uniformity by the above-mentioned means for evaporating silicon.

Therefore, the present invention has been made in order to solve the above-mentioned conventional problems, and its purpose is to prevent the unevenness of the surface due to the occurrence of CVD on the clean surface such as generated in the cleaning processing of the substrate. It is an object of the present invention to provide a surface cleaning method and a thin film forming method that can generate a clean surface without generation of reduction spots.

[0007]

In order to achieve such an object, the present invention generates a plasma of a discharge assisting gas composed of one of hydrogen and a rare gas or a combination of these gases, and generates plasma in the plasma. The substrate surface is cleaned by supplying a reducing gas to the substrate. In another aspect of the present invention, after performing surface cleaning, a gas for vapor phase growth of metal or semiconductor is continuously supplied, and the metal or semiconductor is selectively grown only on the semiconductor or metal surface of the substrate. is there.

[0008]

In the present invention, the case of SiH ₄ will be described as an example of the reducing gas. When an appropriate amount of SiH ₄ is supplied into the plasma of the discharge assisting gas, SiH ₄ is decomposed or excited by the plasma, so SiO ₂
Reaction with becomes active. Therefore, the reduction effect can be obtained even if the supply amount of SiH ₄ gas is extremely small. Si
When the partial pressure of H ₄ is lowered, the deposition rate of Si due to thermal decomposition on the surface of SiH ₄ becomes extremely small, so that Si is hardly deposited on the portion where the reduction of oxide on the surface is completed. Therefore, no large unevenness is generated on the surface. Furthermore, if a substrate with a thick SiO ₂ film partially formed on the surface and a thinly oxidized silicon surface partially exposed is used, the decomposition rate of SiH ₄ by plasma is appropriately reduced, If all the Si attached to the thick SiO ₂ film is gasified by the reaction of the above-mentioned equation (2), Si will not be deposited on the thick oxide film even when all the thin oxide film is reduced. You can also do it.

[0009]

Embodiments of the present invention will now be described in detail with reference to the drawings. To carry out the present invention, a plasma CVD apparatus capable of heating a substrate is used. An example in which the apparatus having the configuration shown in FIG. 1 is used as the plasma CVD apparatus will be described. In the plasma apparatus of FIG. 1, the plasma generation chamber 1 and the reaction chamber 2 are connected by an aperture plate 3, and the plasma generated in the plasma generation chamber 1 leaks to the reaction chamber 2 so that a low-density plasma is formed on the wafer 4. It is possible to stably generate. 5 and 6 are exhaust ports,
Reference numeral 7 is a high frequency power source, 8 is a heater, and 9 and 10 are gas inlets. In order to carry out the present invention, it suffices that a CVD apparatus capable of generating plasma is used, and the present invention is not limited to the apparatus shown in FIG. Various plasma generators such as a parallel plate type, an electron cyclotron resonance (ECR) type, and an induction coil type can be used for generating plasma.
The apparatus of FIG. 1 was devised as an apparatus suitable for depositing a metal film by plasma CVD in particular.

In this CVD apparatus, a discharge assisting gas such as hydrogen or a rare gas is supplied into the plasma generating chamber 1 from the gas introducing port 9 to generate plasma, and the gas introducing port 1 is introduced into the reaction chamber 2.
This is an apparatus for supplying a source gas from 0 to perform plasma CVD. A gas that does not deposit solids when decomposed and excited by plasma is used as a discharge auxiliary gas, and the conductance of the aperture of the aperture plate 3 is appropriately narrowed to make the pressure in the plasma generation chamber 1 higher than that in the reaction chamber 2. By using this apparatus so that the source gas does not enter the plasma generation chamber 1, the metal film can be deposited relatively stably by the plasma CVD method. The surface of the aperture plate 3 on the reaction chamber 2 side may be contaminated by the decomposition products of the source gas. In this case, a cleaning gas containing chlorine or fluorine is supplied from the gas inlet 10 to generate plasma. Adopt it and clean it.

Next, an example of carrying out the present invention using the plasma device of FIG. 1 will be described. First, the wafer 4 is set on the susceptor in the reaction chamber 2 and heated by the heater 8 to generate plasma of the discharge auxiliary gas. As the discharge auxiliary gas, for example, only argon (Ar), a mixed gas of H ₂ and Ar, or only H ₂ is used. Since H ₂ is difficult to discharge, it is necessary to increase the input power of high frequency or increase the pressure of hydrogen in the plasma generation chamber 1 in order to generate plasma only by H ₂ . In order to generate a weak plasma of the discharge auxiliary gas in the reaction chamber 2, the pressure in the reaction chamber 2 is set to about 0.1 Pa or more, and the diameter of the aperture opened in the aperture plate 3 is set to an appropriate size. The internal pressure is set to be 10 to 100 times higher than the internal pressure of the reaction chamber 2, and the plasma is sized to leak from the plasma generation chamber 1 to the reaction chamber 2. The larger the aperture diameter of the aperture plate 3 is, the easier the plasma leaks, but on the other hand, in order to prevent the source gas from entering the plasma generation chamber 1 by increasing the pressure difference between the plasma generation chamber 1 and the reaction chamber 2. The smaller the diameter of the aperture, the better the size of the two.

After the plasma of the discharge auxiliary gas is generated in this manner, SiH is introduced into the reaction chamber 2 through the gas inlet 10.
Supply a small amount of ₄ . The supplied SiH ₄ is decomposed and excited by the plasma generated in the reaction chamber 2, and reduces the oxide film on the surface of the wafer 4. Si as a reducing gas
When H ₄ is used, the heating temperature of the wafer 4 is about 600.
It is necessary to heat at a temperature of not less than 0 ° C, more preferably about 700 ° C or more. If the amount of SiH ₄ supplied is increased or the plasma generation output is increased to accelerate decomposition more than necessary, Si
Are deposited, the oxide film is confined in silicon, and SiO cannot be evaporated. The decomposition rate of SiH ₄ can be easily controlled by the supply flow rate and the plasma generation output (changing the plasma density). Also, S
The decomposition rate of iH ₄ can also be controlled by a method of intermittently and repeatedly generating plasma or a method of intermittently and repeatedly supplying SiH ₄ .

According to such a method, since the amount of SiH ₄ supplied is small, the rate of thermal decomposition of SiH _{4 on} the surface of the wafer 4 is small. Therefore, even if the oxide film on the surface of the wafer 4 is reduced and the silicon surface comes out, Si decomposed by plasma is slowly deposited on that portion, and thermal CVD with a high deposition rate hardly occurs. Therefore, the rough surface unevenness due to the local thermal CVD caused by the reduction unevenness, which is caused by the conventional surface cleaning method by the thermal decomposition of SiH ₄ , is not generated.

The effect of reducing the oxide film according to the present embodiment could be confirmed by the experiment described below and the measurement of secondary ion mass spectrometry (SIMS). First, a 4-inch diameter silicon single crystal wafer is immersed in a mixed solution of sulfuric acid (H ₂ SO ₄ ) and hydrogen peroxide (H ₂ O ₂ ) for cleaning, rinsed thoroughly with pure water, and diluted with dilute hydrofluoric acid. Dip to remove the natural oxide film on the wafer surface, rinse with pure water, and then immerse again in the H ₂ SO ₄ / H ₂ O ₂ mixed solution to form a thin oxide film on the wafer surface and rinse it thoroughly with pure water. Finally, it was dried to obtain an evaluation wafer.

Using the CVD apparatus shown in FIG. 1, the first evaluation wafer was set on the susceptor in the reaction chamber 2, and
It is heated to 10 to 730 ° C., and SiH _{4 is} introduced from the gas inlet 10.
Was supplied at a rate of about 50 cc / min, and the exhaust port 5 was throttled to set the pressure in the reaction chamber 2 to about 40 Pa. As soon as SiH ₄ was supplied and the pressure increased, thermal CVD of silicon started. This state was maintained for about 1 minute to grow a silicon film having a thickness of about 130 nm, and the wafer was taken out of the reaction chamber 2 to obtain a first sample. This first sample is a reference sample in which the cleaning treatment of the wafer surface is not performed, and the thin oxide film formed on the evaluation wafer surface is confined between the substrate and the deposited silicon film. Has been.

Next, the second evaluation wafer is set on the susceptor and heated to the same temperature, Ar is supplied from the gas inlet 9 at about 40 cc / min, and H ₂ is supplied from the gas inlet 10 at about 100.
cc / min to supply the pressure in the reaction chamber 2 to about 0.8 Pa,
About 300 W of high frequency power was applied to generate plasma. After maintaining this state for about 5 minutes, the application of high frequency is stopped, the supply of Ar and H ₂ is stopped, and the gas inlet 10
SiH ₄ is supplied at about 50 cc / min from the above, the exhaust port 5 is throttled to set the pressure in the reaction chamber 2 to about 40 Pa, and the heat CV of silicon is set.
D was performed for about 1 minute to grow a silicon film, and the wafer was taken out of the reaction chamber 2 to obtain a second sample. This second
The second sample is a sample that has been subjected to a surface cleaning treatment using only hydrogen plasma.

Next, the third evaluation wafer is set on the susceptor and heated to the same temperature, Ar is supplied from the gas inlet 9 at about 40 cc / min, and H ₂ is supplied from the gas inlet 10 at about 100.
cc / min to supply the pressure in the reaction chamber 2 to about 0.8 Pa,
About 300 W of high frequency power is applied to generate plasma,
After maintaining this state for about 5 minutes, stop applying high frequency,
Gas supply port 10 while maintaining the supply of Ar and H _{2 as} they are
SiH ₄ is supplied at a rate of about 2 cc / min, a high frequency power of about 300 W is applied to generate plasma for about 20 seconds, and then the application of high frequency is stopped for about 40 seconds. The plasma on / off cycle is repeated three times. , Ar and H ₂ are stopped, SiH ₄ is supplied from the gas inlet 10 at about 50 cc / min, the exhaust port 5 is throttled to set the pressure in the reaction chamber 2 to about 40 Pa, and the thermal CVD of silicon is performed at about 1 This was performed for 3 minutes to grow a silicon film, and the wafer was taken out from the reaction chamber 2 to obtain a third sample. The third sample is a sample that has been subjected to the surface cleaning treatment of this embodiment with hydrogen plasma.

The above three samples were subjected to SIMS analysis to measure the degree of reduction of the thin oxide film formed on the surface of the evaluation wafer. In SIMS analysis, cesium ion (Cs ⁺ ) was used as the primary ion. The measurement results are shown in FIGS. In these figures, the horizontal axis represents the depth from the surface, and the vertical axis represents the concentration. Compared to the peak concentration of oxygen (2.7 × 10 ²¹ atoms / cc) of the reference sample that was not subjected to the cleaning treatment shown in FIG. 2, the cleaning treatment using hydrogen plasma shown in FIG. 3 was performed. Peak oxygen concentration of the second sample (1.9 × 10 ²¹ atoms / cc)
Indicates that the hydrogen plasma treatment reduced the oxide film. The peak concentration of oxygen (8 × 10 ²⁰ atoms / cc) of the sample subjected to the cleaning treatment of this embodiment in the hydrogen plasma treatment shown in FIG. 4 is further decreased, and the cleaning treatment of this embodiment is It can be seen that has a remarkable effect on reducing the oxide film.

The oxygen amount obtained by the integrated concentration is 4.
5 × 10 ^15, a 2.3 × 10 ¹⁵ and 1.1 × 10 ¹⁵ atoms / cm ^2, which are each in the form of SiO ₂ 2.
It corresponds to a thickness of 9, 1.5 and 0.7 ML (monolayer). From these values, the cleaning effect of this embodiment is clear. Note that the oxygen peak depths of the SIMS analysis data in FIGS. 2 to 4 are different not due to the difference in the sputtering rate of the sample at the time of measurement but due to the difference in the film thickness of the deposited silicon. Despite performing the CVD for the same time under the same conditions, the smaller the residual oxygen amount, the thicker the silicon is grown. This is because polycrystalline silicon with a small crystal grain size has grown on the reference sample with a large amount of oxygen on the surface, and epitaxial silicon has grown on the third sample with a small amount of oxygen. This is because the difference in speed caused the difference in film thickness.

Here, a supplementary explanation will be given on the effect of hydrogen plasma which is revealed by another SIMS analysis. The oxide film reduction effect of hydrogen plasma when treated under the conditions described above using the apparatus of FIG. 1 depends on the high frequency power and the treatment time,
When the high frequency power is less than about 300 W, the reduction effect becomes small, and even when the high frequency power is about 300 W, the reduction effect becomes greater as the treatment time is longer. For example, the integrated concentration of oxygen in the sample when the treatment time is about 10 minutes is about half that when the treatment time is about 5 minutes, and the treatment time and the residual oxygen amount are in inverse proportion to each other. Absent. From this result, it is understood that a large plasma generation output is required in order to obtain a large reduction rate by the effect of reducing the oxide film by hydrogen plasma. The use of a large plasma generation power in a wafer surface cleaning process causes a large problem depending on the application target. For example, when a gate electrode such as a MOS transistor is formed on a wafer, the gate insulating film may be destroyed by the influence of plasma as is well known.

On the other hand, the cleaning method of this embodiment is
Since it is based on the decomposition of SiH ₄ , it does not require a large plasma density. An example in which a sufficient effect is obtained even with a small plasma density will be described below. A silicon single crystal wafer with a plane orientation (100) in which a thick oxide film is partially formed is immersed in dilute hydrofluoric acid to remove the thin oxide film on the surface, then washed with water and dried, and then the CVD shown in FIG. It was set on the susceptor of the apparatus and heated to 710 to 730 ° C. Only Ar is supplied from the gas inlet 9 at about 30 cc / min, and the gas inlet 10
SiH ₄ is supplied at about 2 cc / min from the above to generate a plasma for about 20 seconds by applying a high frequency power of about 50 W, and the high frequency on / off cycle of stopping the high frequency power application for about 40 seconds is repeated three times. From the gas inlet 10 to SiH ₄
Was supplied for about 20 cc / min and this state was maintained for about 5 minutes.
The pressure in the reaction chamber 2 is about 0.2 when only Ar is supplied.
It was about 0.4 Pa when 7 Pa and SiH ₄ were added.

When observing the surface and cross section of the wafer with a scanning electron microscope (SEM), no film was grown on the thick oxide film, and the thin oxide film was removed by the dilute hydrofluoric acid treatment. The silicon film was grown to a thickness of about 45 nm in which the surface was extremely flat and smooth only in the portion. A facet surface appeared near the edge of the thick oxide film, indicating that the film was formed by selective epitaxial growth of silicon. In the process described above for comparison, if silicon is grown without applying high frequency power, 2-3
After a lapse of a minute incubation time (time from the supply of the source gas to the start of film growth), the silicon film is selectively grown. However, the growing silicon film is not flat, but has a surface in which nuclei of square pyramids are connected. SiH ₄ during the incubation time
Oxygen is reduced on the surface of the wafer after the treatment with dilute hydrofluoric acid, but it is considered that unevenness was caused by the generation of spots and the growth of silicon starting from the cleaned portion earlier.

Next, a method for cleaning the surface of the semiconductor substrate will be described. As is well known, carbon (C) is likely to be attached to the surface of a semiconductor substrate like oxygen. Carbon is often attached as hydrocarbon due to evaporation of oil in air or in a CVD apparatus. The reduction process of the previous example does not have the ability to remove this carbon. Therefore, if oxygen plasma is first generated to evaporate carbon in the form of CO ₂ or CO, and then the oxide film on the surface is removed by a reduction treatment in which SiH ₄ or the like is added to Ar / H ₂ gas plasma. Both carbon and oxygen can be removed from the substrate surface.

There are two methods for generating oxygen plasma in the plasma apparatus of FIG. The first method is
Oxygen (O ₂ ) gas is supplied from the gas inlet 9 to, for example, 10 to 10
It is supplied at 0 cc / min and high-frequency power of 50 to 500 W is applied to generate it. As a second method, argon gas is supplied from the gas inlet 9 at, for example, 10 to 100 cc / min, and 50
A high frequency power of up to 500 W is applied to generate plasma, and oxygen gas is supplied from the gas inlet 10 to, for example, 10 to 100.
It is a method of supplying cc / min and exciting oxygen gas with argon gas plasma. Since the first method excites the oxygen gas more strongly, a stronger oxidation effect can be obtained, but when the oxygen gas is not desired to be introduced into the plasma generation chamber 1, the second method described above is used. Since the effect of this oxidation treatment can be obtained even if the substrate temperature is not so high, it can be performed while heating the substrate to a predetermined temperature. When the oxidation treatment is completed and the reduction treatment is subsequently performed, oxygen gas is sufficiently exhausted before hydrogen gas is supplied in order to prevent generation of water.

Although SiH ₄ was used as the reducing gas in the above-mentioned embodiments, disilane (Si ₂ H ₆ ) or trisilane (Si ₃ H ₈ ) is used as a gas that is decomposed by plasma to produce Si. Furthermore, Si _n H _{2n + 2} (n = 4,
5, ...) is used instead of SiH ₄ , the same effect can be obtained. Also, germane (GeH ₄ ) and Ge _n H
_{Since 2n + 2} (n = 2, 3, ...) Has a similar reducing effect on the oxide film, it can be used instead of SiH ₄ . When GeH ₄ or the like is used as the reducing gas, the wafer temperature can be lower than when SiH ₄ or the like is used.

Further, as the material of the wafer or film suitable for applying the cleaning treatment method according to the present invention, single crystal,
Polycrystalline and amorphous silicon and semiconductor devices in which these silicons are doped with impurities and single crystals, polycrystalline and amorphous germanium and semiconductor devices in which these germaniums are doped with impurities and single crystal, polycrystalline and amorphous SiGe There is a semiconductor element in which these SiGe are doped with impurities. In addition to the above-mentioned materials, the present invention can be applied to improve the effect as long as the material can generate SiO or GeO to reduce the oxide. For example, it is known that silicides and germanides of various metals form SiO ₂ and GeO ₂ on the surface thereof in an oxidizing atmosphere, and the present invention is useful for reducing these oxides.

Further, in the above-mentioned embodiment, the case where the silicon film is epitaxially grown after the cleaning treatment according to the present invention has been described. However, the present invention can obtain a remarkable effect when a film other than silicon is formed. For example, after performing the cleaning treatment according to the present invention, Ga on the silicon substrate
It is also useful when epitaxially growing a III-V group semiconductor film such as As or when growing a Si / SiGe / Si heteroepitaxial structure. Further, it is also suitable when a titanium silicide film is grown by a CVD method or a plasma CVD method using titanium tetrachloride (TiCl ₄ ) and silane. CVD by this source gas system
It is possible to solve the problem that occurs in step 2, that is, the growth is inhibited even by a small amount of the oxide on the surface, a long incubation time is likely to occur, and island growth is likely to occur.

In this case, the plasma CVD method is used and the Ti
By appropriately selecting the flow rate of Cl ₄ / SiH ₄ and the plasma generation output, a TiSi ₂ film having a C49 structure can be selectively epitaxially grown on a (001) single crystal Si substrate (Japanese Patent Application No. 4-262784). No.). According to such a method, there is an effect of improving the quality of epitaxial growth. Furthermore, on the silicon surface of the silicon substrate, S
Since the unevenness due to the growth of i is hardly formed, for example, M
A titanium silicide film can be thinly grown on silicon of the source / drain electrodes of the OS transistor to form an ohmic contact with low resistance. In addition, when Ge is selectively grown by using germane, TiC
The same effect can be obtained by the present invention when titanium germanide is selectively grown using l ₄ and germane.

Further, using an organoaluminum gas, Al
The surface cleaning method according to the present invention is also useful when selectively growing or selectively epitaxially growing silicon on the surface of silicon or the surface of titanium silicide. Furthermore, the same effect can be obtained by using the present invention when the W film is selectively grown using WF ₆ , H ₂ and SiH ₄ gas. When the reduction temperature of the oxide layer on the substrate surface and the growth temperature of the film deposited thereon are different, the process may be advanced by changing the substrate temperature to the optimum one. Needless to say, the substrate must be placed in an atmosphere free of moisture and oxygen so that the surface of the substrate is not reoxidized after the surface cleaning until the next process. However, in these selective growths, if the decomposition products of the reducing gas decomposed by plasma remain on the surface of the insulating film, the result is likely to impair the selectivity, so the decomposition products react with the insulating film. It is necessary to sufficiently reduce the decomposition rate of the reducing gas by the plasma so that all of the gas is vaporized.

In the present invention, the decomposition rate can be easily controlled by controlling the plasma generation output or the reducing gas supply flow rate. The types of insulating films that can be selectively grown by applying the present invention include SiO and GeO that react with Si and Ge that are decomposition products of reducing gas.
An insulating film that generates is required. Therefore, selective growth is possible by using an insulating film whose main component is SiO ₂ or GeO ₂ . For example, phosphosilicate glass (PS
G), borophosphosilicate glass (BPSG), spin-on glass (SOG) or the like can also be used for selective growth.

[0031]

As described above, according to the surface cleaning method of the present invention, plasma is generated by the discharge auxiliary gas, and the reducing gas is supplied into the plasma to decompose the reducing gas.
Since it excites and reduces the surface, there is no unevenness on the surface due to the occurrence of vapor phase growth on the clean surface that occurred in the conventional cleaning treatment using only reducing gas, and a clean surface without reduction spots is obtained. It has an extremely excellent effect of being obtained.

According to the thin film forming method of the present invention,
When a semiconductor is deposited on the surface of a cleaned semiconductor substrate by a vapor phase epitaxy method, a flat and smooth thin semiconductor thin film can be obtained, which is an extremely excellent effect. Further, by performing the cleaning treatment according to the present invention, the cause of the incubation time can be removed even when the metal film is formed by the vapor phase growth method.
It has an extremely excellent effect that a device with high yield and high reliability can be manufactured.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of the configuration of a CVD apparatus used to carry out a surface cleaning method according to the present invention.

FIG. 2 is a diagram showing SIMS analysis data of a reference sample.

FIG. 3 is a diagram showing SIMS analysis data of a sample subjected to hydrogen plasma treatment.

FIG. 4 is a diagram showing SIMS analysis data of a sample subjected to hydrogen plasma treatment and the cleaning treatment of the present invention.

[Explanation of symbols]

1 ... Plasma generating chamber, 2 ... Reaction chamber, 3 ... Aperture plate,
4 ... Wafer, 5, 6 ... Exhaust port, 7 ... High frequency power source, 8 ... Heater, 9, 10 ... Gas inlet port.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display location H01L 21/304 341 D 21/31 H01L 21/31 C

Claims (8)

[Claims] 1. A reducing gas selected from hydrides of group IV semiconductors is added to a gas plasma of a discharge auxiliary gas selected from hydrogen and a rare gas to decompose and excite the reducing gas, and heating is performed. A surface cleaning method characterized by reducing and removing oxides on the surface of the substrate by exposing it to the surface of the substrate. 2. The surface cleaning method according to claim 1, wherein prior to cleaning the surface of the substrate, the surface of the substrate is exposed to oxygen gas plasma to oxidize the surface of the substrate. 3. The method according to claim 1 or 2, wherein
The hydride of the group IV semiconductor is Si _n H _{2n + 2} (n = 1, 2,
3, ...) or Ge _n H _{2n + 2} (n = 1, 2, 3, ...) And the surface of the substrate is one of Si, Si-Ge, Ge, metal silicide and metal germanide. A surface cleaning method characterized by: 4. The gas plasma according to claim 1, wherein the substrate has an insulating film surface containing Si and O or Ge and O, and a semiconductor or metal surface. Or reducing the supply flow rate of the reducing gas to reduce the decomposition rate of the reducing gas, and vaporize all the reaction products of the decomposition products of the reducing gas and the insulating film. As a result, the surface cleaning method is characterized in that the oxide of the semiconductor or metal surface of the substrate is reduced and removed without depositing the decomposition product of the reducing gas on the surface of the insulating film. 5. The surface cleaning method according to claim 4, wherein the gas plasma is intermittently generated when reducing the decomposition rate of the reducing gas. 6. After the surface cleaning according to claim 1, claim 2, claim 3, claim 4 or claim 5, a metal or semiconductor vapor phase growth gas is subsequently supplied to supply the metal or A method of forming a thin film, which comprises selectively growing a semiconductor only on the semiconductor or metal surface of the substrate. 7. The semiconductor according to claim 6, wherein the semiconductor is Si,
It is composed of one of Si-Ge, Ge, and III-V semiconductors, and the metal is titanium silicide, W, and Al.
The surface of the substrate is made of Si, Si-G.
A method of forming a thin film, wherein e, Ge, and metal are one of silicide and metal germanide. 8. The thin film forming method according to claim 6 or 7, wherein the semiconductor surface is a single crystal, and the metal or semiconductor is selectively epitaxially grown on the single crystal semiconductor surface.