JP2000150901A - Manufacture of thin-film semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a silicon oxide film with high quality even when the surface of the semiconductor film is oxidized at a specified temperature below a significant level by depositing an amorphous semiconductor film using a high-order silane as a kind of material gas by the vapor deposition method and crystalizing it so as to form a semiconductor film. SOLUTION: A substrate 501 is made of quartz glass, and a silicon oxide film is deposited to form a base protection film 502 by the plasma chemical vapor deposition method, and then a semiconductor film made mainly of silicon is deposited thereon by using a high-order silane (SinH2n+2: n = integer of 2 or more) as a kind of material gas by the low-pressure chemical vapor deposition method. Next, a silicon oxide film 504 is formed on the surface of an island 503 as a semiconductor film patterned by the thermal oxidation method. In this case, the semiconductor film is oxidized at 1000 deg.C in an atmosphere with oxygen concentration of 5%, and the silicon film is changed into polycrystalline state. Thus, a thin-film semiconductor device excellent in characteristic can be manufactured easily without adding a special step.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a technique for forming a high-quality semiconductor oxide film on a polycrystalline or amorphous semiconductor film surface at a relatively low temperature of about 1070 ° C. or less by a thermal oxidation method. In particular, the present invention relates to a method for manufacturing a thin film semiconductor device typified by a polycrystalline thin film semiconductor device at a relatively low temperature while maintaining high performance.

[0002] The present invention also relates to a technique for forming a polycrystalline semiconductor film of extremely high quality. In particular, the present invention relates to a manufacturing method for significantly improving the performance of a thin film semiconductor device represented by a polycrystalline thin film semiconductor device by using this technique.

[0003]

2. Description of the Related Art Polycrystalline silicon thin film transistors (p-Si
At present, thin film semiconductor devices represented by TFTs are mainly manufactured by a so-called high-temperature process using a high temperature of about 1100 ° C. or more. The high-temperature process is based on a method of forming a silicon thin film on a substrate by a chemical vapor deposition method (CVD method) and then thermally oxidizing the surface of the silicon thin film at a high temperature of about 1100 ° C. or more. The polycrystalline silicon film and the silicon oxide film thus obtained are used as a semiconductor film and a gate oxide film of a metal-oxide-semiconductor (MOS) field effect transistor (FET).

[0004]

With the widespread use of such polycrystalline silicon thin film transistors, there is a demand for an improvement in productivity and a reduction in cost. These requirements are met by increasing the number of thin film semiconductor devices that can be obtained by enlarging the substrate and extending the life of the manufacturing apparatus. However, if the conventional technology using a high temperature process of about 1100 ° C. or higher is used, the deformation of the substrate due to heat, such as distortion and expansion and contraction, increases exponentially with the increase in the size of the substrate, and the size of the substrate can be increased. There is not. In general, the higher the operating temperature of the manufacturing apparatus is, the shorter its life is remarkably reduced. Under these circumstances, it is now strongly desired to lower the maximum process temperature in manufacturing thin film semiconductor devices.

The highest temperature at the time of manufacturing a polycrystalline thin film semiconductor device is the thermal oxidation step of forming an oxide film on the surface of the semiconductor film as described above. FIG. 1 shows what characteristics the thin film semiconductor device obtained when the thermal oxidation temperature is changed is shown by the results of experiments conducted by the applicant. In this experiment, an amorphous silicon film (a-Si) and a polycrystalline silicon film (p-Si) were respectively formed on a quartz substrate by low pressure chemical vapor deposition (LPCVD).
Method), and the surface of these silicon films is
To oxidize at various temperatures under an atmosphere of 1 atm. Thereafter, a polycrystalline N-type MOS thin film semiconductor device was manufactured according to a normal high-temperature process, and its electrical characteristics were measured. The horizontal axis in FIG. 1 indicates the temperature during thermal oxidation, and the vertical axis indicates the electron mobility of the completed transistor. Ox in the figure
“dation of a-Si” means “as-deposited” immediately after deposition.
ed) Oxidation of p-Si means that a MOSFET was fabricated by thermally oxidizing a polycrystalline silicon film immediately after deposition. I'm doing From this figure, it can be understood that the semiconductor characteristics deteriorate as the oxidation temperature decreases regardless of the type of the semiconductor film. This phenomenon becomes particularly noticeable when the oxidation temperature is about 1070 ° C. or lower, and this is the greatest factor that hinders the lowering of the manufacturing process. This is because in the prior art, lowering the temperature of the oxidation process immediately means lowering of the characteristics of the thin film semiconductor device.

Further, in the prior art, as can be seen from FIG. 1, even when the provisional oxidation temperature is as high as 1160 ° C., the maximum value of the mobility obtained is about 120 cm ² · V ^-1 · s ^-1 . At present, polycrystalline silicon thin film transistors are used only for simple shift register circuits. This is because a metal-oxide-semiconductor field-effect transistor (MOSFE) using single crystal silicon has the performance as a thin film semiconductor device.
This is because it is significantly inferior to T).

Accordingly, the present invention has been made in view of the above-mentioned circumstances, and has as its object the purpose of oxidizing a semiconductor film surface at a temperature lower than a singular point temperature which appears at about 1070 ° C. An object of the present invention is to provide a method for forming an interface between a semiconductor film and an oxide film, and to provide a method for manufacturing an excellent thin film semiconductor device at a relatively low temperature of about 1070 ° C. or less.

It is another object of the present invention to provide a method of manufacturing a thin and excellent semiconductor device comparable to a MOSFET using single crystal silicon.

[0009]

The present invention includes at least a first step of forming a semiconductor film mainly composed of silicon (Si) on a substrate, and a second step of thermally oxidizing the surface of the semiconductor film. In a method for manufacturing a thin film semiconductor device, the first step is to use a higher-order silane (Si _n H
_{2n + 2} : n = 2, 3, 4) is used as a source gas to deposit an amorphous semiconductor film, and then the amorphous film is crystallized so that the silicon (Si) is mainly used. The feature is achieved by forming a semiconductor film. First, prior to the first step, it is preferable to perform a first heat treatment on a substrate on which a silicon oxide film as a base protective film is formed or a high-purity quartz substrate. The temperature of the first heat treatment is between about 800 ° C. and 1100 ° C.

The vapor deposition method for forming a semiconductor film in the first step is preferably performed by a low pressure chemical vapor deposition method (LPCVD method). Among the low pressure chemical vapor deposition methods, a high vacuum type low pressure chemical vapor deposition method is also used. More preferably, it is performed in a vapor deposition apparatus. A high-vacuum low-pressure chemical vapor deposition apparatus typically refers to an apparatus having a background vacuum of 5 × 10 ⁻⁷ Torr or less immediately before semiconductor film deposition. When depositing an amorphous semiconductor film by a low pressure chemical vapor deposition method, the ratio the higher silane flow rate (Q _SiH) of a low pressure chemical vapor deposition apparatus in leak rate _{(Q L) (R = Q} L / Q _SiH ) is about 10 ppm or less (R ≦ 1
It is performed in a state with 0 ^-5). In the low pressure chemical vapor deposition method, the deposition temperature is less than about 430 ° C., and the deposition rate is 0.5
It is desirable to carry out in a state of about nm / min or more.

The crystallization of the amorphous semiconductor film in the first step is preferably carried out in a solid phase. As an example, crystallization in a solid phase is promoted by heat-treating an amorphous semiconductor film at a predetermined temperature between about 500 ° C. and 650 ° C.
A more preferable heat treatment temperature is a predetermined temperature between about 550 ° C and about 600 ° C.

The second step is performed at 1070 ° C. in an oxidizing atmosphere.
It is important to manufacture the excellent thin film semiconductor device at a temperature lower than the order and under the condition that the oxidation time of one atomic layer is longer than the stress relaxation time of the oxide film. Specifically, the second step is performed under an atmosphere containing oxygen (O ₂ ) and an inert gas.
Carried out at less than about 070 ° C. the temperature T (° C.), and at an oxygen partial pressure in the second step (P _O2) is _{t 1> τ t 1 = Δx} (Δx + 2x i + A) / B × 60 (s) Δx = 0.36 (nm) x _i = 5 (nm) A = A ₀ exp (α / (k (T + 273.15))) A ₀ = 0.2026 (nm) α = 0.666 (eV) k = 8 .617 × 10 ⁻⁵ (eV · K ⁻¹ ) B = B ₀ exp (−β / (k (T + 273.15))) · C _O2 B ₀ = 3.14 × 10 ⁸ (nm ² · min ⁻¹⁾ ) Β = 1.620 (eV) k = 8.617 × 10 ⁻⁵ (eV · K ⁻¹ ) C _O2 = P _O2 (atm) / 1 (atm) C _O2 is a dimensionless coefficient τ corresponding to the oxygen concentration. = Η / μ η = η ₀ exp (γ / (k (T + 273.15))) η ₀ = 2.3 × 10 ⁻⁶ (dyn · s · cm ⁻² ) γ = 4.85 (eV) k = 8.61 ^{× 10 -5 (eV · K -1} ) μ = 3.15 × 10 11 may be carried out under conditions satisfying the formula of (dyn · cm ^-2).

[0013]

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of forming a silicon film (S) on various substrates such as quartz glass, high heat resistant glass, and single crystal silicon substrate.
i) and silicon germanium film _{(Si x Ge 1-x:} 0 <x <
The present invention relates to a method for manufacturing a thin film semiconductor device including at least a first step of forming a semiconductor film represented by 1) and a second step of oxidizing the surface of the semiconductor film. In particular, the semiconductor film has silicon as its main constituent element (silicon atom composition ratio is about 80% or more), and therefore, the oxide film formed on the surface also has silicon oxide as its main constituent element. The semiconductor film is formed by a vapor deposition method such as a physical vapor deposition method (PVD method) or a chemical vapor deposition method (CVD method). As the PVD method, a sputtering method, an evaporation method, or the like can be considered. The CVD method includes atmospheric pressure chemical vapor deposition (APCVD) and low pressure chemical vapor deposition (LPCVD).
Method), plasma-enhanced chemical vapor deposition (PECVD) and the like. Immediately after deposition, a semiconductor film formed by a vapor deposition method is usually in a polycrystalline state, an amorphous state, or a mixed state thereof. A thin film in a polycrystalline state is called a polycrystalline film, and the thin film is composed of many crystal grains. A grain boundary exists at the boundary between the crystal grains. Similarly, a thin film in the amorphous state is called an amorphous film, and the thin film is composed of many amorphous grains or a mixture of amorphous grains and a small amount of crystal grains (M. Miyasaka, et al .: Jpn. J. Appl.
Phys. Vol. 36 (1997) p. 2049). An arrowhead grain boundary also exists between the amorphous grains or between the amorphous grains and the crystal grains. Semiconductor thin films formed by vapor deposition have more or less, in most cases, these grain boundaries. One of the aspects of the present invention relates to thermal oxidation of a semiconductor film in which these crystal grains and amorphous grains form a thin film alone or in a mixed state, and include a grain boundary in the thin film.

The oxidation of the surface of the semiconductor film in the second step can be performed on the polycrystalline film or the amorphous film obtained by the vapor deposition method in the first step as it is, It can also be performed after the film is recrystallized or the amorphous film is crystallized into a polycrystalline state. Even when crystallization or recrystallization is performed, the polycrystalline thin film is composed of many crystal grains, and a grain boundary is always recognized between the crystal grains. The recrystallization of the polycrystalline film and the crystallization of the amorphous film are performed by changing the temperature of the semiconductor film from about 500 ° C. to 1 °.
It may be carried out in a solid state at an appropriate temperature of about 200 ° C., or may be carried out through a molten state and a cooling and solidifying process. An example of a simple means of performing recrystallization or crystallization is to irradiate a polycrystalline film or an amorphous film obtained by a vapor deposition method or the like with an electromagnetic wave or a particle stream having high energy such as laser light. It is considered as.

In the present invention, the semiconductor film thus obtained in the first step is subjected to the second step of thermal oxidation in an oxidizing atmosphere at a temperature of less than about 1070 ° C. At this time, the time spent for oxidizing one atomic layer of a semiconductor film constituent element such as silicon (one atomic layer oxidation time) is spent for relaxing the stress of the oxide film resulting from the oxidation (oxide film). Oxidation proceeds under conditions longer than the stress relaxation time). Since the oxide film stress relaxation time is a function only of the temperature at which the oxide film is exposed, the stress relaxation time is automatically determined when the oxidation temperature is determined. Therefore, the present invention specifies the oxidation conditions so that the oxidation time is longer than the stress relaxation time thus determined, in other words, the oxidation rate is lower than the stress relaxation rate. This oxidation condition cannot be satisfied by the oxidation in which the oxygen partial pressure is 1 atm (the oxygen concentration is 100% under the atmospheric pressure), which has been performed in the prior art, and nitrogen (N ₂ ), argon (Ar), helium (He), etc. Under an atmosphere containing an inert gas and oxygen (O ₂ ) or water (H ₂ O), or an inert gas and nitrous oxide (N
It is satisfied by promoting the oxidation in an atmosphere containing ₂ O) or an atmosphere containing such an inert gas and carbon dioxide (CO ₂ ). In addition, the oxidation in the second step may be advanced in an atmosphere containing water, nitrous oxide, and carbon dioxide alone. What is important is most of the oxidation progression time except for the very beginning of oxidation (the time when the oxide film thickness is less than about 5 nm), and the oxidation time of one atomic layer becomes longer than the stress relaxation time. Oxidation is performed in a state where the stress accompanying the above is always relaxed.

In order to make the monoatomic layer oxidation time longer than the oxide film stress relaxation time in the thermal oxidation step performed at a temperature of less than about 1070 ° C., the second step must be performed with oxygen (O ₂ ) and the above-mentioned inert gas. There is also recognized a method of performing the reaction in an atmosphere containing oxygen or under a low pressure containing oxygen alone to thereby delay the oxidation rate. At this time, since the oxidation rate is uniquely determined as a function of the oxygen partial pressure (P _O2 ), the stress can be relaxed at the oxidation progress interface only by adjusting the oxygen partial pressure. Now, set the oxidation temperature to 1070
The temperature is set to a temperature T (° C.) lower than about ° C. Deal on thermal oxidation
-Grove's classical theory (BE Deal, et al .: J. App. Phy
s. vol. 36 (1965) p. 3770), the atomic layer oxidation time t _{1 at the very} beginning of oxidation is calculated as t ₁ = Δx (Δx + 2x _i + A) / B × 60 (s) Is done. Here, Δx is the thickness of the semiconductor atomic layer, and its value is approximately 0.36 nm. The x _i in oxide film thickness obtained very early oxidation classical theory of Deal-Grove is effective when the oxide film has more thickness. The value of _xi is approximately 5 nm. The monolayer oxidation time increases with the growth of the oxide film. This condition will always be met in the period. That is, the monoatomic layer oxidation time t ₁ obtained by substituting the value of Δx = 0.36 (nm) x _i = 5 (nm) into the above equation
Should be longer than the oxide film stress relaxation time. The coefficient B is called a parabolic rate constant, and is proportional to the product of the diffusion coefficient of oxygen in the oxide film and the oxygen concentration in the oxidizing atmosphere.
The coefficient B / A is called a linear rate constant, and is proportional to the oxidation reaction rate at the oxidation progress interface. These coefficients A and B are a function of the oxidation temperature T (° C.) and are described as follows, according to precise measurements made by the applicant.

A = A ₀ exp (α / (k (T + 273.15))) A ₀ = 0.226 (nm) α = 0.666 (eV) k = 8.617 × 10 ⁻⁵ (eV · K ⁻¹ ) B = B ₀ exp (−β / (k (T + 273.15))) · C _O2 B ₀ = 3.14 × 10 ⁸ (nm ² · min ⁻¹ ) β = 1.620 (eV) k = 8.617 × 10 ⁻⁵ (eV · K ⁻¹ ) C _O2 = P _O2 (atm) / 1 (atm) Here, P _O2 indicates the oxygen partial pressure at the time of oxidation. When performed under low pressure, it indicates the pressure in the thermal oxidation furnace. C _O2 is a dimensionless coefficient corresponding to the oxygen concentration in a thermal oxidation atmosphere. For example, oxygen in argon
% And the oxidation at atmospheric pressure, the value of this dimensionless coefficient is 0.05. Similarly, 0.05 atm (38 Torr) at an oxygen concentration of 100% without using a diluted inert gas.
If oxidation is performed under low pressure, this value is 0.05. On the other hand, it is known that a silicon oxide film behaves as a viscoelastic material when the temperature is about 700 ° C. or higher.
Using the stress relaxation model, the oxide film stress relaxation time τ is expressed as follows depending on the rigidity η and the viscosity μ (A. Farge
ix, et al .: J. Phys. D: Appl. Phys. vol.17 (1984)
p.2331).

Τ = η / μ η = η ₀ exp (γ / (k (T + 273.15))) η ₀ = 2.3 × 10 ⁻⁶ (dyn · s · cm ⁻² ) γ = 4.85 ( eV) k = 8.617 × 10 ⁻⁵ (eV · K ⁻¹ ) μ = 3.15 × 10 ¹¹ (dyn · cm ⁻² ) Thus, the monoatomic layer oxidation time t ₁ is the oxide film stress relaxation time τ.
The requirement that the length be longer than the above is to be oxidized so as to satisfy the equation of t ₁ > τ. Specifically, when the thermal oxidation temperature is determined, a dimensionless coefficient corresponding to the oxygen concentration is determined so as to satisfy the above inequality, and oxidation is performed at the oxygen partial pressure. Since it is confirmed that the oxide film behaves as a viscoelastic body at about 700 ° C. or higher, the above inequality can be applied only when the oxidation temperature is about 700 ° C. or higher. If the oxidation rate becomes too slow, it takes several tens of hours to obtain an oxide film having a thickness of about 5 nm, where the theory of Deal-Grove oxidation starts to be established, which is not practical. It takes about 14 hours and 30 minutes to obtain an oxide film of about 5 nm at 900 ° C. in accordance with the present invention.
A temperature of about 0 ° C. or higher is desired.

The phenomenon that the mobility decreases as the oxidation temperature lowers, and especially deteriorates sharply at about 1070 ° C. or less, is explained as follows according to the study of the applicant. In the oxidation of a semiconductor (eg, Si) film, in an oxide film (eg, in SiO ₂ )
Is diffused by an oxidation reactant (eg, O ₂ ) such as oxygen, and after the reactant reaches the interface between the oxide film and the semiconductor film, the reactant converts oxygen atoms (O) between semiconductor constituent atoms (eg, Si—Si).
) And a new oxide layer (e.g., Si-OS)
forming i). For this reason, the distance between adjacent semiconductor atoms (for example, the distance between Si-Si) in the semiconductor and the distance between semiconductor atoms (for example, Si-O-
The distance between Si and Si in Si) naturally differs. This difference in interatomic distance causes tensile stress in the semiconductor film,
A compressive stress is generated in the oxide film. Oxidation temperature is 10
When the temperature is about 70 ° C. or more, the compressive stress relaxation time of the oxide film is shorter than the monoatomic layer oxidation time, so that the stress generated by the oxidation is immediately relaxed and no stress remains at the oxidation progress interface. However, when the oxidation temperature is lower than about 1070 ° C., the stress relaxation time is longer than the one-atomic layer oxidation time, so that the oxidation always proceeds in the presence of stress. FIG. 2 shows these relationships. The horizontal axis is the oxidation temperature and the vertical axis is the time. There are three lines in the monolayer oxidation time, 20nm and 60n respectively.
m, 120 nm means that the oxide film thickness is 20 nm or 60 nm.
This indicates the time required to further oxidize a monolayer of semiconductor from the state of nm or 120 nm. Oxidation is carried out at 100% oxygen and 1 atm.
Is analyzing the oxidation phenomenon of the prior art. When the oxidation temperature is 1100 ° C. or 1160 ° C., the line for the monolayer oxidation time is above the line for the stress relaxation time, and it can be seen that the oxidation time is longer than the stress relaxation time. The line for the monolayer oxidation time and the line for the relaxation time intersect at about 1070 ° C., and at lower temperatures, the stress relaxation time is longer. 1070
At a temperature lower than about ° C., the time during which the stress of the oxide film is relaxed is longer than the time during which the monoatomic layer of the semiconductor is oxidized, and therefore, the oxidative stress always remains at the oxidation progress interface.

The semiconductor film dealt with in the present application is formed by a vapor deposition method or the like, and the semiconductor film necessarily has grain boundaries. This is recognized regardless of whether the semiconductor film to be oxidized is a polycrystalline film or an amorphous film. When the semiconductor film having such a grain boundary is oxidized in a state where the stress remains, the stress is concentrated on the grain boundary and the semiconductor constituent atoms and the oxide constituent atoms are violently moved. As a result, the unevenness of the interface becomes severe, and the interface becomes rough. This interface roughness leads to a decrease in mobility and an increase in surface state, which is a main cause of deteriorating the characteristics of the thin film semiconductor device. The roughness of the interface due to oxidation depends on the strength of the stress and the smoothness of the semiconductor film. As mentioned earlier, stress is determined by the relationship between stress relaxation time and oxidation time,
When the stress relaxation time is shorter than the monoatomic layer oxidation time, a smooth interface between the polycrystalline semiconductor film and the oxide film is obtained. on the other hand,
The degree of smoothness of a semiconductor film as an oxidation target substance is determined by a method for forming the semiconductor film. The semiconductor film can be directly formed by vapor deposition if an amorphous film formed by vapor deposition or a polycrystalline film obtained by crystallizing the amorphous film in a solid phase is used as the substance to be oxidized. There is a tendency that a smoother surface can be easily obtained than when the obtained polycrystalline film is oxidized.

Such a function does not operate when the semiconductor film as the substance to be oxidized is a single crystal film. This is because, by definition, a grain boundary cannot exist in a single crystal film, and therefore, even if the oxidation is performed under residual stress, the oxidative stress cannot concentrate on the grain boundary. When the single crystal film is oxidized at a processing temperature of about 1070 ° C. or less at an oxygen concentration of 100%, an oxidative stress similarly occurs, but the stress is uniformly applied to the entire interface. Moreover, since the surface of the single crystal semiconductor film is flat, local stress concentration cannot occur, and it will be understood that interface roughness during oxidation does not occur. Although only the stress is generated even at the low temperature oxidation of the single crystal film, this stress can be completely released by the heat treatment in an inert gas atmosphere after the oxidation. In low-temperature oxidation of a single crystal film, if heat treatment under an inert atmosphere after oxidation is properly performed,
This means that all the adverse effects of low-temperature oxidation can be eliminated. On the other hand, in low-temperature oxidation of a semiconductor film having grain boundaries, heat treatment after oxidation is not as effective as that of a single crystal film. Certainly, the stress remaining after the completion of the oxidation can be released by the post-oxidation heat treatment, but it is impossible to suppress the roughened and finished interface during the oxidation period. What is important in the oxidation of the non-single-crystal film is to perform the oxidation under such a condition that stress does not concentrate on the interface during the oxidation period.

FIG. 3 shows an example of oxidation in which stress is not concentrated on the interface during the oxidation period (an example of the present invention). 3 is the same as FIG. The only difference is that in FIG.
% In that oxygen was diluted with an inert gas and oxidized. Since the oxidation is performed at atmospheric pressure, the value of the dimensionless coefficient corresponding to the oxygen concentration is 0.05. As can be seen from FIG. 3, the oxygen supply rate to the oxidation progressing interface was reduced by dilution, so that the monolayer oxidation time shifted upward, and at any temperature above 940 ° C., the stress relaxation was more than that of the monolayer oxidation time. Time is short. In other words, if the temperature is about 940 ° C. or higher, even if the semiconductor film having the grain boundaries is oxidized, stress concentration on the grain boundaries and the resulting interface roughness do not occur, and the semiconductor characteristics are also good. It is a thing. Of course, if the value of the dimensionless coefficient corresponding to the oxygen concentration is further reduced,
The intersection of the line of the monoatomic layer oxidation time and the line of the stress relaxation time shifts to a lower temperature side, thereby achieving a lower temperature of oxidation.

As shown in the example of FIG. 3, the simplest method of oxidation in which stress is not concentrated on the interface is a method of adjusting the oxygen partial pressure (dimension coefficient corresponding to the oxygen concentration) at the time of oxidation. How to make this adjustment will be described. Here, as an example, the oxidation temperature is 1
Consider the case of 070 ° C. The oxidation coefficients A and B are calculated as the following numerical values according to the above-mentioned equations.

A = 63.930 (nm) B = 261.889 × C _O2 (nm ² · min ⁻¹ ) Using this, the monoatomic layer oxidation time t ₁ is expressed as follows.

T ₁ = 1604.66 / (261.889 × C _O2 ) (s) On the other hand, the rigidity η and viscosity μ of the oxide film at 1070 ° C. are η = 3.636 × 10 ¹² (dyn · s · cm ⁻² ) μ = 3.15 × 10 ¹¹ (dyn · cm ⁻² ), the oxide film stress relaxation time τ is τ = 3.636 × 10 ¹² /(3.15×10 ¹¹ ) = 111. 543 (s). When connecting the此of t ₁ and τ in the preceding _{inequality, 1604.66 / (261.889 × C O2} )> 11.543 is obtained by solving此against C _O2, C _O2 <0.53 Is obtained. After all, when the oxidation temperature is 1070 ° C,
It is understood that the oxidation may be performed by adjusting the oxygen concentration and the pressure so that the dimensionless coefficient corresponding to the oxygen concentration is less than 0.53. In this way, stress is not concentrated on the grain boundaries, and a smooth interface between the polycrystalline semiconductor film and the oxide film is formed. FIG.
Shows the maximum oxygen concentration at each oxidation temperature calculated in this way. If oxidation is performed at a desired oxidation temperature at an oxygen partial pressure lower than the curve in FIG. 4, the monoatomic layer oxidation time will always be longer than the oxide film stress relaxation time, thereby producing an excellent thin film semiconductor device. There is.

In order to make a thin film semiconductor device typified by a polycrystalline silicon thin film transistor an excellent thin film semiconductor device comparable to a MOSFET using single crystal silicon, the oxidation method described so far is of course. The method of forming a semiconductor film in the first step also plays an important role. The formation of the semiconductor film in the first step determines the size of the crystal grains constituting the polycrystalline semiconductor film after thermal oxidation and the purity of the semiconductor film. Because it has an effect on

In the first step, a semiconductor film mainly composed of silicon (Si) is formed on the substrate. As the substrate, a semiconductor substrate such as single crystal silicon or an insulating substrate such as quartz glass or ceramic is used. On the surface of such a substrate, a silicon oxide film as a base protective film for the semiconductor film is formed from about 100 nm to 1 nm.
About 0 μm is deposited. The silicon oxide film as a base protective film not only provides electrical insulation between the semiconductor film and the substrate, or prevents diffusion of impurities contained in the substrate into the semiconductor film, but also prevents the base oxide film from being crystalline. The interface with the semiconductor film is of good quality. In the present invention, the semiconductor film of the thin film semiconductor device has a thickness of about 10 nm to about 150 nm, and the energy band is bent over the entire area of the semiconductor film in the thickness direction (corresponding to a fully depleted model of SOI). Conceivable. In addition, the semiconductor film of the present invention has a very small trap level density of about 3 × 10 ¹⁶ cm ⁻³ or less. In such a situation, the interface between the underlying protective film and the semiconductor film, as well as the interface between the gate insulating film and the semiconductor film, has a considerable effect on electric conduction. Since a silicon oxide film is a substance that can reduce the interface trap level when forming an interface with a semiconductor film, it is suitable as a base protective film.
The semiconductor film is formed on the underlying protective film. Therefore, a silicon oxide film having an interface state of about 10 ¹² cm ⁻² or less at the interface with the semiconductor film is desired as the base protective film. A silicon oxide film satisfying these conditions has a solution temperature of 25 ± 5 ° C. and a concentration of 1.
The etching rate in an aqueous solution of 6 ± 0.2% hydrofluoric acid (HF) is 1.5 nm / s or less. Usually, the underlayer protective film is formed by plasma enhanced chemical vapor deposition (PECVD).
), A low-pressure chemical vapor deposition (LPCVD) method, or a vapor deposition method such as a sputtering method or a thermal oxidation method. Among them, in order to form a base protective film particularly suitable for the present invention, the electron cyclotron resonance P
ECVD (ECR-PECVD) and Helicon PEC
It is preferable to use the VD method and the remote PECVD method. In order to obtain a silicon oxide film suitable for the present invention by a general-purpose PECVD method using an industrial frequency (13.56 MHz) or an integer multiple thereof, TEOS must be used as a raw material.
_{(Si- (O-CH 2 CH} 3) 4) and using oxygen (O _2), the oxygen flow rate is set to more than five times the TEOS flow rate may be deposited silicon oxide film. Alternatively, monosilane (SiH ₄ ) and nitrous oxide (N ₂ O) are used as raw materials, and a rare gas such as helium (He) or argon (Ar) is used as a diluent gas. The silicon oxide film may be deposited at a gas ratio of about 90% or more (that is, a raw material ratio in the total gas flow rate of less than about 10%).
At that time, the substrate temperature is desired to be 280 ° C. or higher. When the substrate is made of high-purity quartz, the underlying protective film and the quartz substrate can be used in combination. It is preferable to form a base protective film. The simplest method of forming a base protective film suitable for the present invention by any other method is to perform a heat treatment on an oxide film formed by a vapor deposition method or a thermal oxidation method. Under an almost inert atmosphere containing nitrogen, argon, etc. as a main component, from about 800 ° C. to 11
By performing a heat treatment in a temperature range of about 00 ° C. for about 10 minutes to 2 hours, a silicon oxide film having a low interface state can be formed. By doing so, the thickness of the semiconductor film constituting the active layer of the thin film semiconductor device is finally reduced from about 10 nm to 150
Even if the thickness is as thin as about nm, an excellent thin film semiconductor device having a low threshold voltage and a sharp subthreshold region (sub-threshold hold) characteristic is manufactured. This is also applicable to a case where the substrate is a high-purity quartz substrate, and the base protective film and the quartz substrate are also used. This is because the quartz substrate is also subjected to the heat treatment under the above conditions, so that the stress generated during the manufacture of the quartz substrate is relaxed, or the interface state is reduced by viscous flow in the quartz substrate.

An amorphous semiconductor film is deposited on the underlying protective film by physical vapor deposition or chemical vapor deposition. Dust and dirt on the underlying protective film reduce the purity of the semiconductor, and further become an amorphous nucleus when depositing an amorphous film, or a crystal nucleus when growing an amorphous film. It is necessary to sufficiently clean the substrate before film deposition. Accordingly, a polycrystalline semiconductor film having high purity and large crystal grains can be obtained later. The substrate provided with the base protective film is washed with an aqueous solution containing a surfactant such as soap, an aqueous solution containing an acid, an aqueous solution containing an alkali, or an organic solvent such as an alcohol such as ethanol or a ketone such as acetone. Examples of the aqueous solution containing an acid include sulfuric acid (H ₂ SO ₄ ), hydrochloric acid (HCl), and nitric acid (HN
O ₃ ), an aqueous solution such as hydrofluoric acid (HF), or a mixed solution of sulfuric acid, hydrogen peroxide (H ₂ O ₂ ) and pure water (H ₂ O) (hereinafter abbreviated as “sulfuric peroxide” in the present specification) ), A mixture of hydrochloric acid, hydrogen peroxide and pure water (abbreviated as hydrochloric / hydrogen peroxide), a mixture of nitric acid, hydrogen peroxide and pure water (abbreviated as nitric peroxide), sulfuric acid, hydrofluoric acid and pure water Particularly suitable are a mixture of water (H ₂ O), a mixture of hydrochloric acid, hydrofluoric acid and pure water, a mixture of nitric acid, hydrofluoric acid and pure water, and a mixture of ammonia, hydrofluoric acid and pure water. I have As the aqueous solution containing an alkali, an ammonia (NH ₃ ) aqueous solution or a mixed solution of ammonia, hydrogen peroxide and pure water (abbreviated as ammonia peroxide) is suitable. Before the semiconductor film is deposited, it is necessary to appropriately combine these various types of cleaning, and finally to sufficiently wash away with pure water. As an example of preferable cleaning of a substrate made of quartz or the like, there is a method of performing the following four types of cleaning: an organic solvent cleaning, an alkali cleaning, an acid cleaning, and a surface layer removing step.

(1) Washing of organic solvent (1-1) Washing of ketone such as acetone (removal of organic matter) (0 to 30 ° C. for about 1 to 10 minutes) (1-2) Washing of alcohol such as ethanol (removal of organic matter) (1 to 10 minutes at 0 ° C to 30 ° C) (1-3) Pure water washing (ketone and alcohol removal) (1 to 10 minutes at 0 ° C to 30 ° C) (2) Alkaline washing (2-1) Ammonia peroxide washing (metal removal) (1 to 10 minutes at 50 to 100 ° C) (2-2) Pure water washing (ammonia removal) (1 to 10 minutes at 0 to 50 ° C) (3) Acid Cleaning (3-1) Sulfuric acid peroxide cleaning (metal removal) (1 to 10 minutes at 50 to 100 ° C) (3-2) Pure water cleaning (sulfuric acid removal) (1 to 10 minutes at 0 to 50 ° C) (3-3) Cleaning with hydrochloric acid / hydrogen peroxide (metal removal) (5 (3-4) Pure water washing (removal of hydrochloric acid) (0 to 50 ° C for about 1 to 10 minutes) (4) Surface oxide film removal step (4-1) Hydrofluoric acid aqueous solution cleaning (removal of oxide film surface and hydrogen termination of oxide film surface) (from 0 ° C. to 30 ° C. for about 1 second to 1 minute) (4-2) Pure water cleaning (removal of hydrofluoric acid) (0 ° C. to 30 ° C.) The most important of these four-step cleaning is the cleaning in the surface oxide film removing step. This is because if the surface layer of the oxide film forming the base protective film is removed, metal, dust, and the like adhering to the surface layer are automatically removed. Therefore, when it is desired to minimize the cleaning process before depositing the semiconductor film in response to a request for process simplification or the like, the cleaning process may be set so as to include at least cleaning for removing the surface oxide film. The hydrofluoric acid aqueous solution cleaning is performed so as to remove about 1 nm to about 20 nm of the surface layer portion of the base oxide film. If the thickness is about 1 nm or less, the cleaning effect is not the same in the substrate from the viewpoint of uniformity, and if the thickness is about 20 nm or more, the function of preventing impurities from being mixed in the base oxide film may be impaired when the base oxide film is thin. Yes. Performing the hydrofluoric acid aqueous solution cleaning immediately before depositing the semiconductor film means terminating the surface of the underlying oxide film with hydrogen atoms. Since this hydrogen is relatively easily separated, it reacts chemically with silane at the very beginning of the semiconductor film deposition process, thereby improving the adhesion between the underlying oxide film and the silicon film. In addition, there is an effect of reducing the interface state between the base oxide film and the semiconductor film. Therefore, as shown in the present application, a system in which the thickness of the active layer semiconductor film is less than about 100 nm and the energy band of the semiconductor film is bent over the entire thickness direction (a system corresponding to complete depletion of SOI).
In this case, improvement in transistor characteristics such as improvement of sub-threshold swing, reduction of threshold voltage, and reduction of off-state current are observed. The hydrofluoric acid aqueous solution is basically a solution in which hydrofluoric acid is dissolved in pure water so that the concentration of hydrofluoric acid becomes about 0.1% to about 10%, but ammonia may be added to this solution.

After the above-described washing and the final washing with pure water, an amorphous semiconductor film is deposited on the underlying protective film. Various vapor deposition methods are possible for semiconductor film deposition,
From the standpoint that high-purity semiconductor films are easily deposited,
Among them, low pressure chemical vapor deposition (LPCVD) is particularly suitable. After the substrate has been rinsed with pure water,
It should be installed immediately (within at most about 2 hours) in the vapor deposition apparatus. The low pressure chemical vapor deposition method is performed in a high vacuum type low pressure chemical vapor deposition apparatus. The high vacuum type means that the background vacuum degree immediately before the deposition of the amorphous semiconductor film is 5 × 10 ⁻⁷ Torr.
In the apparatus, the leakage flow rate from the outside of the apparatus to the film formation chamber is specifically, the maximum total degassing flow rate from the cleaned substrate (the maximum total degassing flow rate for 17 glass substrates of 300 mm × 300 mm is: The device has airtightness of about one tenth or less (about 1 × 10 ⁻² (sccm)) (leakage flow from the outside of the apparatus is about 1 × 10 ⁻³ (sccm) or less according to the above example). . If the airtightness of the film formation chamber is less than about one-tenth of the inevitable maximum degassing flow rate from the substrate, the total impurity flow rate (to the The sum of the leakage flow rate from the outside of the apparatus and the degassing flow rate from the substrate is not significantly affected.
Such a high-vacuum type low-pressure chemical vapor deposition apparatus not only has excellent airtightness in the film forming chamber, but also has a pumping speed in the film forming chamber of 100 sccm / mTorr (inert gas of 100 sccm).
The equilibrium pressure obtained when flowing into the sccm deposition chamber is 1 mT
It is further desired to have an evacuation capacity of about (or the evacuation speed of orr). In such a device having a high pumping capacity, in a relatively short time of about one hour, the degassing flow rate of water or the like from the sufficiently cleaned substrate is reduced to the same level as the leak flow rate of the device, This is because productivity can be significantly increased.

A semiconductor film mainly composed of silicon typified by an amorphous silicon film is deposited using high-order silane (Si _n H _{2n + 2} : n is an integer of 2 or more) as a source gas. Considering price and safety, the higher silane is disilane (Si
₂ H ₆ ) is most suitable. To deposit a high-purity, high-quality semiconductor film, the ratio (R = Q) of the leakage flow rate (Q _L ) from the outside of the apparatus to the high-order silane flow rate (Q _SiH ) in the low-pressure chemical vapor deposition apparatus. _L / Q _SiH ) 10ppm
Or less (R ≦ 10 ⁻⁵ ). (In the case where the leakage flow rate is about 1 × 10 ⁻³ (sccm), the disilane flow rate is about 100 sccm or more.) As described above, in the present invention, the substrate is formed by using a high vacuum type low pressure chemical vapor deposition apparatus. leakage flow rate of de-gas flow rate from the outside from (Q _L)
Attempts are made to deposit a semiconductor film when the temperature is less than about the same. Therefore, the total impurities flow rate is at a level comparable with the leakage flow rate (Q _L) from the outside. The substance leaking from the outside of the apparatus to the film formation chamber is mainly air. Since nitrogen, which makes up 80% of the air, is inert, no major problem is caused with respect to semiconductor quality, and oxygen which makes up the remaining 20% as an impurity is a problem. On the other hand, among the higher order silanes introduced into the film formation chamber, those actually involved in the reaction and taken into the semiconductor film vary slightly depending on the film formation conditions, but are about 20%. Yes. Thus, even assuming a worst reality, not impossible in the impurity such as oxygen present in the if the film formation chamber is taken all in the semiconductor film, a high leakage rate from the outside (Q _L) The ratio (R) to the secondary silane flow rate (Q _SiH )
= Q _L / Q _SiH ) is about 10 ppm or less (R ≦ 10 ⁻⁵ ), the concentration of unnecessary impurities such as oxygen atoms with respect to silicon atoms in the deposited semiconductor film is at most about 10 ¹⁷ cm ^−3. (Actually, about 10 ¹⁶ cm ⁻³ or less), and a high-purity semiconductor film can be obtained. When a high-purity polycrystalline semiconductor film is used as an active layer of a thin-film semiconductor device (source-drain region or channel formation region of a field-effect transistor, or emitter-base-collector region of a bipolar transistor), a semiconductor film forbidden band is used. This has the effect of reducing the trapping level inside and minimizing the decrease in mobility due to the impurity element.

In addition to the above conditions, the present invention further provides
The amorphous semiconductor film is deposited at a relatively low temperature of less than about 30 ° C. At this time, the deposition rate of the semiconductor film is 0.5 nm / m.
The pressure in the film forming chamber, the flow rate of the higher order silane, or the number of inserted substrates is set so as to be about in or more. Such low temperature (4
When the amorphous semiconductor film is deposited at a relatively high deposition rate at a temperature lower than about 30 ° C.), the amorphous grains constituting the amorphous film obtained by the deposition generally become large. The crystal grains of the polycrystalline film obtained when crystallizing are significantly increased. A polycrystalline film composed of crystal grains having a large grain size has a high mobility value, and a thin-film semiconductor device using this as an active layer exhibits excellent performance. As can be seen from this description, one important requirement for realizing a high performance thin film semiconductor device is the conditions for depositing an amorphous film. Low temperature of less than about 430 ° C and 0.5 nm / mi
When an amorphous semiconductor film is deposited at a deposition rate of about n or more,
The generation rate of nuclei (amorphous nuclei) from which the amorphous grains grow is slower than the growth rate of the amorphous film, and therefore the amorphous grains constituting the deposited amorphous film become larger. . However, if the cleaning of the substrate is insufficient during the deposition of the semiconductor film, the impurities attached to the substrate act as amorphous nuclei, so that the amorphous grains are reduced to a small size. Similarly, if there is insufficient sensitivity of the vapor deposition apparatus (e.g., _{R = Q L / Q SiH>} 10 -5), adhering impurity gas leaked from outside the film forming chamber is on the substrate arrows clad non As a result, an excellent amorphous film composed of large-sized amorphous grains cannot be obtained. Also, if the substrate is not sufficiently dried in the film forming chamber (at this time, the background vacuum degree immediately before the deposition of the semiconductor film is not lower than about 5 × 10 ⁻⁷ Torr), the amorphous particles are formed on the same principle. Become smaller. In order to obtain a high performance thin film semiconductor device, the substrate is sufficiently cleaned (at least a cleaning step of removing a surface oxide film),
A film forming apparatus (R
= Q _L / Q _SiH ≦ 10 ⁻⁵ ), and after the substrate is thoroughly dried in the film forming chamber (the background vacuum degree immediately before the deposition of the semiconductor film is 5 × 1).
0 ^-7 Torr or less), and then depositing the amorphous semiconductor film at a deposition temperature of less than about 430 ° C. and at a deposition rate of about 0.5 nm / min or more using a higher-order silane such as disilane as a source gas. It is important to deposit.

After the amorphous semiconductor film is thus obtained, the amorphous semiconductor film is crystallized to form a polycrystalline semiconductor film. It is preferable that the crystallization of the amorphous film be performed in a solid phase by heat-treating the amorphous film at a predetermined temperature between about 500 ° C. and about 650 ° C. This is because in the solid-phase crystallization, the correlation between the size of the amorphous grains constituting the amorphous film and the size of the crystal grains constituting the polycrystalline film is extremely strong. In other words, when an amorphous film composed of large amorphous grains is crystallized in a solid phase, a polycrystalline film composed of large crystal grains is obtained. The lower the heat treatment temperature during crystallization is, the lower the temperature is, the more the generation of crystal nuclei is suppressed, so that a polycrystalline film composed of larger crystal grains can be obtained, but the time required for completing the crystallization is correspondingly longer. The heat treatment temperature is as low as possible between about 500 ° C. and about 650 ° C., ideally about 550 ° C. to 6 ° C.
The temperature is set to a predetermined temperature between about 00 ° C.

After the polycrystalline semiconductor film is formed in the first step, the surface of the polycrystalline semiconductor film is thermally oxidized in the second step to form an active semiconductor layer and an oxide film of the field-effect thin film transistor. To form The oxide film may be used as it is as a gate insulating film, or another insulating film may be formed on the crystalline semiconductor film which is an active layer by a certain method after being separated once. The second step is 1070 in an oxidizing atmosphere.
It is performed at a temperature of less than about ° C. and under the condition that the oxidation time of one atomic layer is longer than the stress relaxation time of the oxide film. Hydroxyl groups in the oxide film (-
OH) and water, the second step is performed at a temperature T (° C.) of less than about 1070 ° C. in an atmosphere containing oxygen (O ₂ ) and an inert gas. partial pressure (P _O2) is _{t 1> τ t 1 = Δx} (Δx + 2x i + A) / B × 60 (s) Δx = 0.36 (nm) x i = 5 (nm) A = A 0 exp (α / (K (T + 273.15))) A ₀ = 0.226 (nm) α = 0.666 (eV) k = 8.617 × 10 ⁻⁵ (eV · K ⁻¹ ) B = B ₀ exp (−β /(K(T+273.15)))·C _O2 B ₀ = 3.14 × 10 ⁸ (nm ² · min ⁻¹ ) β = 1.620 (eV) k = 8.617 × 10 ⁻⁵ (eV · ^{_{K -1) C O2 = P O2}} (atm) / 1 (atm) C O2 is the dimensionless coefficient corresponding to the oxygen concentration τ = η / μ η = η 0 exp (γ / (k (T + 273.1 _{))) Η 0 = 2.3 ×} 10 -6 (dyn · s · cm -2) γ = 4.85 (eV) k = 8.617 × 10 -5 (eV · K -1) μ = 3. The thermal oxidation is performed under the condition of 15 × 10 ¹¹ (dyn · cm ⁻² ). These are as described in detail above.

(Embodiment 1) FIGS. 5A to 5D show MOS transistors.
FIG. 4 is a cross-sectional view showing a manufacturing process of a thin-film semiconductor device for forming a field-effect transistor. In the first embodiment, the substrate 5
01 is quartz glass. However, the type and size of other substrates are not limited as long as they can withstand the maximum temperature during the thin film semiconductor device manufacturing process. First, a semiconductor film of silicon or the like which will eventually become an active layer is deposited on a substrate 501. If the substrate is a conductive material such as a single-crystal silicon substrate doped with impurities, or if a ceramic substrate or the like contains undesired impurities in a semiconductor film, a silicon dioxide film or a silicon dioxide film is deposited before the semiconductor film is deposited. It is preferable to deposit a base protective film 502 such as a silicon nitride film. In the first embodiment, the substrate 5
A silicon oxide film having a thickness of about 200 nm was deposited on the substrate 01 by plasma enhanced chemical vapor deposition (PECVD) to form a base protective film 502. After depositing the base protective film, the substrate is heated at 1000 ° C. in nitrogen.
A first heat treatment of 20 minutes was applied. The etching rate of the silicon oxide film after the first heat treatment in an aqueous solution of hydrofluoric acid (HF) having a liquid temperature of 25 ° C. and a concentration of 1.67% is 0.2 nm.
/ S. On this underlying protective film, an intrinsic amorphous silicon film was deposited to a thickness of about 100 nm by LPCVD. L
The PCVD apparatus is a hot wall type and has a capacity of 184.5.
1, the total reaction area after insertion of the substrate is about 44000 cm ² . The deposition temperature is 425 ° C. and the purity is 99.
Using disilane (Si ₂ H ₆ ) of 99% or more, 200 sc
cm reactor. Deposition pressure is about 1.1 Torr
Under these conditions, the deposition rate of the silicon film is 0.77 nm.
/ Min. The amorphous silicon film thus obtained was patterned to form a semiconductor film island 503.
(FIG. 5-a) Next, a silicon oxide film 504 was formed on the surface of the island 503 of the semiconductor film patterned by the thermal oxidation method. Oxidation is 10
1 atmosphere and 1 atmosphere in an atmosphere with an oxygen concentration of 5%
It took 4 hours and 15 minutes. The thermal oxidation furnace is a hot wall type having a volume of about 46 l. In the thermal oxidation furnace when the substrate is inserted, oxygen (O ₂ ) having a purity of about 99.999% or more is 250.
Nitrogen (N ₂ ) with sccm and purity of about 99.999% or more
Was introduced at 4750 sccm, and the oxygen concentration inside the thermal oxidation furnace was maintained at 5.0%. The furnace temperature when inserting the substrate is 80
0 ° C. When oxidizing at atmospheric pressure, air (oxygen concentration about 20.9%) enters the oxidation furnace when the substrate is inserted.
It is preferable to keep the temperature of the oxidation furnace at about 800 ° C. or lower so that the initial oxidation does not proceed significantly in the unadjusted state. When a substrate provided with a semiconductor film having a grain boundary formed by a vapor deposition method or the like is inserted into an inert atmosphere at about 700 ° C. or higher, atom migration such as recrystallization and crystallization occurs rapidly, and Since these semiconductor films have a lower density than the single crystal film, a large number of holes are formed in the semiconductor film as a result of the rapid atom transfer. Of course, this is not preferable for producing a good thin film semiconductor device. This problem is solved by placing the substrate in an oxidizing atmosphere. This is because an oxide film is formed on the surface of the semiconductor film and the movement (crystallization) of semiconductor atoms proceeds simultaneously.
This is probably because oxygen atoms replenish small voids generated between the semiconductor atoms at the stage before the generation of the huge atom movement that causes a hole in the semiconductor film. In any case, the substrate must be inserted in an oxidizing atmosphere so that no hole is formed in the semiconductor film. Moreover, in order to accurately control the oxidation process so as to obtain an oxide film thickness and film quality and a smooth interface, there is a problem even if the oxygen concentration is too high. It is desirable that they are substantially the same. After the substrate is inserted, the temperature of the oxidation furnace is increased at a rate of 10 ° C./min, and the oxidation temperature is increased to 1000 ° C. in about 20 minutes. After reaching the oxidation temperature, this state (referred to as an oxidation process) is maintained for 14 hours and 15 minutes to perform oxidation. During the period of the oxidation process from the time of substrate insertion, the above-described oxygen and nitrogen are continuously introduced into the reaction furnace, and the inside of the oxidation furnace is maintained at a desired constant atmosphere. Immediately after the completion of the oxidation process, the supply of oxygen is stopped, and 5000 sccm of nitrogen is introduced into the reaction furnace (referred to as post-oxidation treatment). At this time, the oxidation furnace temperature was still 10% of the oxidation temperature.
Keep at 00 ° C. In thermal oxidation of single crystal silicon, this post-oxidation treatment had its purpose in releasing the stress of the oxide film. In the present application, since the stress of the oxide film is completely released during the oxidation period, the main purpose is not to release the stress but to prevent unnecessary low-temperature oxidation. After the oxidation is completed, the substrate is eventually taken out of the reaction furnace. At this time, the quality of the interface between the polycrystalline semiconductor film and the oxide semiconductor film is prevented from deteriorating. The post-oxidation treatment is therefore continued until the inside of the reactor becomes inactive with respect to the semiconductor film (the residual ratio of gas introduced into the oxidation process is less than about 5%). Assuming a complete mixing system in which fluid mixing is the slowest, the post-oxidation treatment time (30 in this embodiment 1) is set to the inert gas flow rate (5 slm of nitrogen in this embodiment 1).
Min) and the total amount of inert gas multiplied by 5 min.
slm × 30 minutes = 150 l) is the reactor volume (Example 1)
In this case, it is preferable to set the flow rate and time of the inert gas in the post-oxidation treatment so as to be about three times or more of 46 l). This is because if the ratio is about three times or more, the remaining ratio becomes less than about 5%. After the atmosphere in the reactor is replaced, the temperature of the reactor is lowered to about 800 ° C. at a rate of about 5 ° C./min.
Thereafter, the substrate is taken out of the reactor. The temperature when the substrate comes into contact with air is desirably about 800 ° C. or less to prevent low-temperature oxidation. In this way, the oxidation of the surface of the semiconductor film is completed, the silicon film changes to a polycrystalline state, and its film thickness is reduced to about 68 nm. The silicon oxide film 5 formed on the surface of the semiconductor film
04 has a thickness of about 58 nm. Next, in order to adjust the threshold voltage of the thin film semiconductor device, ¹¹ B ⁺ was implanted into the semiconductor film at an acceleration voltage of 20 kV and a concentration of 1.2 × 10 ¹² cm ⁻² .

Subsequently, a gate electrode 505 is formed by a silicon film containing a donor or an acceptor. In the first embodiment, the gate electrode is formed of 500 nm polycrystalline silicon containing phosphorus. The sheet resistance of the gate electrode at this time is 15
Ω / □. Next, using the gate electrode as a mask, an impurity ion 506 serving as a donor or an acceptor is implanted to form a source / drain region 507 and a channel formation region 508 in a self-aligned manner with respect to the gate electrode. In the first embodiment, a CMOS thin film semiconductor device was manufactured. NM
When an OS transistor is manufactured, a PMOS transistor portion is covered with a resist, and phosphorus ( ^{31) is used} as an impurity element.
P ⁺ ) was implanted into the source / drain region of the NMOS transistor at an acceleration voltage of 50 kV to a concentration of 5 × 10 ¹⁵ cm ⁻² . Conversely, when fabricating a PMOS transistor, cover the NMOS transistor part with resist,
Accelerating voltage 20k select boron ⁽¹¹ B ⁺⁾ as the impurity element
V was implanted into the source / drain region of the PMOS transistor at a concentration of 3 × 10 ¹⁵ cm ⁻² . (FIG. 5-c) Next, an interlayer insulating film 509 was deposited by a PECVD method or the like. The interlayer insulating film is composed of a silicon dioxide film, and its film thickness is about 50.
It was 0 nm. After the deposition of the interlayer insulating film, a heat treatment was performed at 1000 ° C. for 20 minutes in a nitrogen atmosphere for the purpose of both baking the interlayer insulating film and activating the impurity element added to the source / drain regions. Finally, a contact hole was opened, and a wiring 510 was formed with aluminum or the like, whereby a thin film semiconductor device was completed. (FIG. 5-d) The transfer characteristics of the thin-film semiconductor device thus prepared were measured. The length and width of the channel forming region of the thin film semiconductor device measured were 8 μm and 10 μm, respectively, and the measurement was performed at room temperature. FIG. 6 shows the obtained transfer characteristics. NMOS transistor ON state (source / drain voltage (Vd
s) and the gate voltage (Vgs) are both 3.3 V), the source / drain current (Ids: referred to as on-current) is 2
7.6 μA, and Ids (referred to as off-state current) when the transistor was turned off at Vds = 3.3 V and Vgs = 0 V was 2.26 pA. The mobility of this transistor obtained from the saturation region at Vds = 5 V is 1
It was 60 cm ² · V · s ^-1 and the threshold voltage was 1.07 V. Furthermore, the ON current of the PMOS transistor (Vds
= Vgs = -3.3V) is 1.92 μA, and the off current (Vds = -3.3V, Vgs = 0V) is 0.134p
A. The mobility and threshold voltage of the PMOS transistor were 81 cm ² · V · s ^-1 and -2.92 V, respectively.
Gate voltage 3.3V for both N-type and P-type thin film semiconductor devices
The on / off ratio with respect to the modulation was actually 7 digits or more, and a very good thin film semiconductor device having a high mobility and a low threshold voltage was obtained. As shown in this example, according to the present invention, even when the maximum process temperature is about 1000 ° C., it is very excellent only by strictly adjusting the thermal oxidation process without adding a special process. This makes it possible to easily and easily produce a thin film semiconductor device having the above characteristics.

(Comparative Example 1) In order to clearly show that the present invention is superior to the prior art, the prior art for Example 1 will be described here.

In Comparative Example 1, a thin film semiconductor device was manufactured in the same manner as in Example 1 except for all steps except for the thermal oxidation step. The oxidation was performed at 1000 ° C. in an atmosphere having an oxygen concentration of 100% at 1 atm for 1 hour and 3 minutes. The thermal oxidation furnace is the same as that used in Example 1. Oxygen (O ₂ ) having a purity of about 99.999% or more is introduced into the thermal oxidation furnace when the substrate is inserted at 5000 sccm. The furnace temperature at the time of substrate insertion is 1000 ° C. Therefore, oxidation starts immediately after the substrate is inserted. Oxygen is constantly introduced at 5000 sccm into the reactor during the oxidation process from the time of substrate insertion. 1 hour 3
Immediately after the oxidation process for one minute is completed, the supply of oxygen is stopped, and 5000 sccm of nitrogen is introduced into the reaction furnace (post-oxidation treatment). The post-oxidation treatment time was 15 minutes. After the post-oxidation treatment is completed, the substrate is taken out of the reaction furnace. The temperature of the reactor was maintained at 1000 ° C. throughout the period from substrate insertion to substrate removal. In Comparative Example 1, the oxidation of the semiconductor film surface was completed in this manner. The oxidized polycrystalline silicon film had a thickness of 72 nm, and the thickness of the silicon oxide film formed on the surface of the polycrystalline silicon film was 60 nm. Hereinafter, a CMOS thin film semiconductor device was manufactured in the same steps as in Example 1.

FIG. 7 shows the transfer characteristics of the thin film semiconductor device obtained in Comparative Example 1. The ON current of the NMOS transistor was 17.6 μA, and the OFF current was 1.59 pA. On the other hand, the ON current of the PMOS transistor is 1.04 μA
And the off-state current was 0.359 pA. The mobility and the threshold voltage are entered in FIG. The superiority of Example 1 of the present invention is likely to be clearer than Comparative Example 1.

Embodiment 2 Another embodiment of the present invention is shown here.

In Example 2, a thin-film semiconductor device was manufactured in the same manner as in Example 1 except that all the steps were the same except for the step of forming a semiconductor film which was a substance to be oxidized. As the semiconductor film, an intrinsic polycrystalline silicon film having a thickness of about 100 nm was formed on the underlying protective film by the LPCVD method. The LPCVD apparatus is the same as that used in the first embodiment. The deposition temperature is 615 ° C., and monosilane (Si
H ₄ ) and fed to a 70 sccm reactor. The deposition pressure was approximately 70 mTorr, and under these conditions, the deposition rate of the polycrystalline silicon film was 3.4 nm / min. Hereinafter, a CMOS thin film semiconductor device was manufactured in the same steps as in Example 1. The polycrystalline silicon film after the thermal oxidation had a thickness of 60 nm, and the thickness of the silicon oxide film formed on the surface of the polycrystalline silicon film was 68 nm.

FIG. 8 shows the transfer characteristics of the thin film semiconductor device obtained in Example 2. The ON current of the NMOS transistor was 4.34 μA, and the OFF current was 0.622 pA.
On the other hand, the ON current of the PMOS transistor is 1.02 μA
The off-state current was 2.21 pA. The mobility and the threshold voltage are entered in FIG. The characteristics of a thin-film semiconductor device obtained by subjecting a polycrystalline silicon film to thermal oxidation at 1000 ° C. according to the present invention are as follows. It was almost equivalent to the characteristics. As shown in Example 2, the present invention has an excellent effect of substantially lowering the oxidation temperature by about 200 ° C. or more.

(Comparative Example 2) In order to clearly show that the present invention of Example 2 is superior to the prior art, the prior art for Example 2 will be presented here as Comparative Example 2.

In Comparative Example 2, a thin film semiconductor device was manufactured in the same manner as in Example 2 except for all the steps except for the thermal oxidation step. A semiconductor film to be oxidized was formed by the method described in Example 2, and thermal oxidation was performed by the method described in Comparative Example 1. That is, in Comparative Example 2, the polycrystalline silicon film obtained by the LPCVD method is thermally oxidized in an atmosphere of 1000 ° C. and an oxygen partial pressure of 1 atm to produce a thin film semiconductor device.
The thermal oxidation time was 1 hour and 3 minutes. The polycrystalline silicon film after the thermal oxidation had a thickness of 65 nm, and the thickness of the silicon oxide film formed on the surface of the polycrystalline silicon film was 56 nm. Except for this, a CMOS thin film semiconductor device was manufactured in the same steps as in Example 2.

FIG. 9 shows the transfer characteristics of the thin film semiconductor device obtained in Comparative Example 2. The ON current of the NMOS transistor was 0.568 μA, and the OFF current was 1.14 pA.
On the other hand, the ON current of the PMOS transistor is 0.100 μ
At A, the off-state current was 0.972 pA. The mobility and the threshold voltage are entered in FIG. If this Comparative Example 2 is compared with Example 2, the advantage of the present invention will be obvious.

(Embodiment 3) FIGS. 10A to 10D show MOs.
FIG. 5 is a cross-sectional view illustrating a manufacturing process of the thin-film semiconductor device for forming the S-type field-effect transistor. In the third embodiment, quartz glass was used as the substrate 1001. However, the type and size of other substrates are not limited as long as they can withstand the maximum temperature during the thin film semiconductor device manufacturing process. First, a silicon oxide film serving as a base protective film 1002 is deposited on a substrate 1001. If the substrate is made of a conductive material such as a single-crystal silicon substrate doped with impurities at a high concentration, or if a ceramic substrate or the like contains undesired impurities in a semiconductor film, before depositing the silicon oxide film, A first underlying protective film such as a tantalum oxide film or a silicon nitride film may be deposited. In the third embodiment, a plasma enhanced chemical vapor deposition (PE)
A silicon oxide film was deposited to a thickness of about 200 nm by a CVD method to form a base protective film 1002.

After depositing the underlayer protective film, the substrate was washed in the following procedure.

(1) Isopropyl alcohol cleaning by ultrasonic irradiation (27 ° C., 5 minutes) (2) Nitrogen bubbling pure water cleaning (27 ° C., 5 minutes) (3) Ammonia / hydrogen cleaning (80 ° C., 5 minutes) (4) Cleaning with pure water with nitrogen bubbling (27 ° C., 5 minutes) (5) Cleaning with sulfuric acid and peroxide (97 ° C., 5 minutes) (6) Cleaning with nitrogen bubbling and pure water (27 ° C., 5 minutes) (7) Washing with diluted hydrofluoric acid aqueous solution (hydrofluoric acid concentration 1.67%)
(8 ° C., 20 seconds) (8) Nitrogen-bubbled pure water cleaning (27 ° C., 5 minutes) The surface layer portion of the base oxide film is removed by about 10 nm by the seventh diluted hydrofluoric acid aqueous solution cleaning. An intrinsic amorphous silicon film was deposited to a thickness of about 100 nm by LPCVD on the thus-washed base protective film. The time from completion of the eighth pure water cleaning until the substrate was set in the film forming chamber of the LPCVD apparatus was about 25 minutes.

The LPCVD apparatus is a hot wall type, has a volume of 184.5 l, and has a total reaction area of about 4 after the substrate is inserted.
4000 cm ² . The maximum pumping speed in the film forming chamber is 120 sccm / mTorr. Deposition temperature is 425
The substrate was heated and dried at this temperature for 1 hour and 15 minutes at this temperature. During the drying heat treatment, helium (He) with a purity of 99.9999% or more was set to 200 (sccm) and the purity was 99.99999 in the film formation chamber in which the substrate was installed.
% Or more of hydrogen (H ₂ ) was introduced at 100 (sccm), and the pressure in the film forming chamber was maintained at about 2.5 mTorr. The pressure rise in the film formation chamber when the film formation chamber is isolated after the drying treatment is 9.7.
Since it was × 10 ⁻⁶ Torr / min, the total impurity leakage flow rate (Q _TL ), which is the sum of the leakage flow rate (Q _L ) from the outside of the apparatus to the film formation chamber and the degassing flow rate from the substrate, was Boyle Charles Q _TL (sccm) = 273.15 (K) /698.15
(K) × 9.7 × 10 ^-6 (Torr / min) / 760
(Torr) × 184.5 × 10 ³ (cm ³ ) = 9.21
× 10 ^-4 (sccm). Disilane (Si ₂ H ₆ ) having a purity of 99.99% or more, which is a raw material gas, was supplied to the film formation chamber at a flow rate of 200 sccm. Therefore, the ratio of the higher order silane to the total impurity leakage flow rate (Q _TL ) (Q _TL / Q) _SiH ) is 4.605 × 10 ^-6 . Therefore, naturally the ratio the higher silane flow rate (Q _SiH) of leak rate _{(Q L) (R = Q} L / Q SiH) is 4.605
ppm or less. The background vacuum in the film forming chamber immediately before the deposition of the semiconductor film after the completion of the drying process was 2.4 × 10 ⁻⁷ Torr under the temperature equilibrium condition of 425 ° C. The deposition pressure during the deposition of the amorphous silicon film is about 1.1 Torr, and under these conditions, the deposition rate of the silicon film is 0.77 nm /
min.

Next, the thus obtained amorphous semiconductor film was subjected to a heat treatment to crystallize the amorphous film in a solid phase. The heat treatment was performed at a temperature of 600 ° C. for 24 hours in a mixed gas atmosphere of 99% nitrogen and 1% oxygen at atmospheric pressure. By this heat treatment, the semiconductor film is modified from an amorphous state to a polycrystalline state. The crystalline silicon film thus obtained was patterned to form a semiconductor film island 1003. (Fig. 10-
a) Next, a silicon oxide film 1004 was formed on the surface of the island 1003 of the semiconductor film patterned by the thermal oxidation method. Oxidation was performed at a temperature of 1000 ° C. in an atmosphere with an oxygen concentration of 5% at 1 atm for 14 hours and 15 minutes. The thermal oxidation furnace is a hot wall type having a volume of about 46 l. Oxygen (O ₂ ) with a purity of about 99.999% or more is contained in the thermal oxidation furnace when the substrate is inserted.
Nitrogen (N) having a flow rate of 50 sccm and a purity of about 99.999% or more
₂ ) was introduced at 4750 sccm, and the oxygen concentration inside the thermal oxidation furnace was maintained at 5.0%. The furnace temperature at the time of substrate insertion is 800 ° C. When oxidizing at atmospheric pressure, air (oxygen concentration about 20.9%) is mixed into the oxidizing furnace when the substrate is inserted. It is preferable to keep When a substrate provided with a semiconductor film having a grain boundary formed by a vapor deposition method or the like is inserted into an inert atmosphere at about 700 ° C. or higher, atom migration such as recrystallization and crystallization occurs rapidly, and Since these semiconductor films have a lower density than the single crystal film, a large number of holes are formed in the semiconductor film as a result of the rapid atom transfer. Of course, this is not preferable for producing a good thin film semiconductor device. This problem is solved by placing the substrate in an oxidizing atmosphere. This is because the oxide film is formed on the surface of the semiconductor film and the movement (crystallization) of the semiconductor atoms proceeds at the same time. It is presumed that the small voids generated in the above are supplemented by oxygen atoms. In any case, the substrate must be inserted in an oxidizing atmosphere so that no hole is formed in the semiconductor film. Moreover, in order to accurately control the oxidation process so as to obtain an oxide film thickness and film quality and a smooth interface, there is a problem even if the oxygen concentration is too high. It is desirable that they are substantially the same. After the substrate is inserted, the temperature of the oxidation furnace is increased at a rate of 10 ° C./min, and the oxidation temperature is increased to 1000 ° C. in about 20 minutes.
After reaching the oxidation temperature, this state (referred to as oxidation process)
The oxidation is carried out for 4 hours and 15 minutes. During the period of the oxidation process from the time of substrate insertion, the above-described oxygen and nitrogen are continuously introduced into the reaction furnace, and the inside of the oxidation furnace is maintained at a desired constant atmosphere. Immediately after the completion of the oxidation process, the supply of oxygen is stopped, and 5000 sccm of nitrogen is introduced into the reaction furnace (referred to as post-oxidation treatment). At this time, the oxidation furnace temperature is still maintained at the oxidation temperature of 1000 ° C. In thermal oxidation of single crystal silicon, this post-oxidation treatment had its purpose in releasing the stress of the oxide film. In the present application, since the stress of the oxide film is completely released during the oxidation period, the main purpose is not to release the stress but to prevent unnecessary low-temperature oxidation. After the oxidation is completed, the substrate is eventually taken out of the reaction furnace. At this time, the quality of the interface between the polycrystalline semiconductor film and the oxide semiconductor film is prevented from deteriorating. The post-oxidation treatment is therefore continued until the inside of the reactor becomes inactive with respect to the semiconductor film (the residual ratio of gas introduced into the oxidation process is less than about 5%). Assuming a complete mixing system in which fluid mixing is the slowest, an inert gas flow rate (Example 3
5 slm of nitrogen) multiplied by the post-oxidation treatment time (30 minutes in the third embodiment), the total amount of inert gas (5 slm of nitrogen x 30 minutes = 150 l in the third embodiment) is equal to the reactor volume (the third embodiment). It is preferable to set the flow rate and time of the inert gas in the post-oxidation treatment so as to be about 3 times or more of 46 l). This is because if the ratio is about three times or more, the remaining ratio becomes less than about 5%. After the replacement of the atmosphere in the reaction furnace is completed, the temperature of the reaction furnace is lowered to about 800 ° C. at a rate of about 5 ° C./min, and then the substrate is taken out of the reaction furnace. The temperature when the substrate comes into contact with air is desirably about 800 ° C. or less to prevent low-temperature oxidation. In this way, the oxidation of the semiconductor film surface ends,
The film thickness is reduced to about 71 nm. The thickness of the silicon oxide film 1004 formed on the surface of the semiconductor film is about 57 nm. (FIG. 10-b) Next, in order to adjust the threshold voltage of the thin film semiconductor device, ¹¹ B ⁺ was implanted into the semiconductor film at an acceleration voltage of 20 kV and a concentration of 1.2 × 10 ¹² cm ⁻² .

Subsequently, a gate electrode 1005 is formed using a silicon film containing a donor or an acceptor. In the third embodiment, a gate electrode was formed of 500 nm polycrystalline silicon containing phosphorus. At this time, the sheet resistance of the gate electrode is 1
It was 5Ω / □. Next, using the gate electrode as a mask, an impurity ion 1006 serving as a donor or an acceptor is implanted to form a source / drain region 1007 and a channel formation region 1008 in a self-aligned manner with respect to the gate electrode. In the third embodiment, a CMOS thin film semiconductor device was manufactured. When fabricating an NMOS transistor, after covering the PMOS transistor portion with a resist, phosphorus ( ³¹ P ⁺ ) is selected as an impurity element and 5 × 10 ¹⁵ at an acceleration voltage of 50 kV.
Implanted into the source / drain region of the NMOS transistor at a concentration of cm ⁻² . On in making the PMOS transistor Contrary to cover the NMOS transistor portion in the resist, as the impurity element, boron ⁽¹¹ B ⁺⁾ to select the acceleration voltage of the PMOS transistor to a concentration of 3 × 10 ¹⁵ cm ^-2 at 20kV Implanted in source / drain region. (Figure 1
0-c) Next, an interlayer insulating film 1009 was deposited by a PECVD method or the like.
The interlayer insulating film is composed of a silicon dioxide film, and its film thickness is about 5
00 nm. After the deposition of the interlayer insulating film, a heat treatment was performed at 1000 ° C. for 20 minutes in a nitrogen atmosphere for the purpose of both baking the interlayer insulating film and activating the impurity element added to the source / drain regions. Finally, a contact hole was opened, and a wiring 1010 was formed with aluminum or the like, whereby a thin film semiconductor device was completed. (FIG. 10-d) The transfer characteristics of the thin-film semiconductor device thus manufactured were measured. The length and width of the channel forming region of the thin film semiconductor device measured were 8 μm and 10 μm, respectively, and the measurement was performed at room temperature. FIG. 11 shows the obtained transfer characteristics. NMOS
Transistor ON state (source-drain voltage (Vd
s) and the gate voltage (Vgs) are both 3.3 V), the source / drain current (Ids: referred to as on-current) is 6
8.5 μA, and Ids (referred to as off-state current) when the transistor was turned off at Vds = 3.3 V and Vgs = 0 V was 0.12 pA. The mobility of this transistor obtained from the saturation region at Vds = 5 V is 3
It was 95 cm ² · V · s ^-1 and the threshold voltage was 1.07 V. Furthermore, the ON current of the PMOS transistor (Vds
= Vgs = -3.3V) is 7.92 μA, and the off current (Vds = -3.3V, Vgs = 0V) is 11.1 pA
It was. The mobility and threshold voltage of the PMOS transistor were 102 cm ² · V · s ^-1 and -1.95 V, respectively.
Both N-type and P-type thin-film semiconductor devices obtained good thin-film semiconductor devices having small sub-threshold swing, high mobility and low threshold voltage. NMO
S thin film semiconductor devices have shown incredibly excellent properties comparable to field effect transistors made on single crystal silicon substrates.

[0052]

As described above in detail, the present invention can easily lower the temperature of a manufacturing process of a thin-film semiconductor device, which could not be lowered conventionally, while maintaining excellent characteristics. As a result, an excellent thin film semiconductor device can be stably manufactured with high mass productivity.

Further, according to the present invention, it is possible to easily manufacture a thin film semiconductor device having a performance comparable to a field effect type thin film semiconductor device formed on a single crystal silicon substrate.

[Brief description of the drawings]

FIG. 1 is a diagram showing a relationship between an oxidation temperature and mobility in a conventional technique.

FIG. 2 is a view for explaining the principle of oxidation in the prior art.

FIG. 3 is a diagram illustrating the principle of oxidation in the present invention.

FIG. 4 is a diagram showing a maximum value of a dimensionless coefficient for implementing the present invention.

FIG. 5 is a diagram illustrating a manufacturing process of the present invention.

FIG. 6 is a diagram showing the effect of the present invention.

FIG. 7 is a view showing a comparative example.

FIG. 8 is a diagram showing the effect of the present invention.

FIG. 9 is a view showing a comparative example.

FIG. 10 is a diagram illustrating a manufacturing process of the present invention.

FIG. 11 is a diagram showing the effect of the present invention.

[Description of Reference Numerals] 501: substrate 502: base protective film 503: semiconductor film 504: gate oxide film 505: gate electrode 506: impurity ion 507: source / drain region 508: channel formation region 509: interlayer insulating film 510: wiring 1001 : Substrate 1002: base protective film 1003: semiconductor film 1004: gate oxide film 1005: gate electrode 1006: impurity ion 1007: source / drain region 1008: channel formation region 1009: interlayer insulating film 1010: wiring

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference) GG34 GG37 GG42 GG43 GG44 GG45 GG47 HJ01 HJ04 HJ13 HJ23 HL03 NN02 NN23 PP10 PP13

Claims (23)

[Claims] 1. A method for manufacturing a thin film semiconductor device, comprising: a first step of forming a semiconductor film mainly composed of silicon (Si) on a substrate; and a second step of thermally oxidizing a surface of the semiconductor film. In the first step, an amorphous film is deposited by vapor phase deposition (CVD) using higher order silane (Si _n H _{2n + 2} : n = 2, 3, 4) as a source gas. A method of manufacturing a thin film semiconductor device, wherein a semiconductor film is formed by crystallizing the amorphous film. 2. The method according to claim 1, wherein the vapor deposition is a low pressure chemical vapor deposition (LPCVD). 3. The low-pressure chemical vapor deposition method according to claim 2, wherein the low-pressure chemical vapor deposition method is performed in a high-vacuum type low-pressure chemical vapor deposition apparatus.
A manufacturing method of the thin film semiconductor device according to the above. 4. The thin film semiconductor device according to claim 3, wherein the high vacuum type low pressure chemical vapor deposition apparatus has a background vacuum of 5 × 10 ⁻⁷ Torr or less immediately before semiconductor film deposition. Production method. Wherein said low-pressure chemical vapor deposition method ratio higher silane flow rate _{(Q SiH) (R = Q} L / Q SiH) is 10ppm for in leak rate to a low pressure chemical vapor deposition apparatus (Q _L)
3. The method for manufacturing a thin film semiconductor device according to claim 2, wherein the method is performed in a state of about (R ≦ 10 ⁻⁵ ) or less. 6. The low pressure chemical vapor deposition method has a deposition temperature of 4 ° C.
Less than about 30 ° C. and a deposition rate of 0.5 nm / min
6. The method for manufacturing a thin film semiconductor device according to claim 2, wherein the method is performed in a state of about or more. 7. The method for manufacturing a thin film semiconductor device according to claim 1, wherein the crystallization of the amorphous film in the first step proceeds in a solid phase. 8. The crystallization of the amorphous film in the first step is performed by heat-treating the amorphous film at a predetermined temperature between about 500 ° C. and 650 ° C. The method for manufacturing a thin film semiconductor device according to claim 1. 9. The crystallization of the amorphous film in the first step is performed by heat-treating the amorphous film at a predetermined temperature between about 550 ° C. and about 600 ° C. The method for manufacturing a thin film semiconductor device according to claim 1. 10. The method according to claim 1, wherein the second step is performed under an oxidizing atmosphere.
The method of manufacturing a thin film semiconductor device according to claim 1, wherein the method is performed at a temperature of less than about 070 ° C. and under a condition that a monoatomic layer oxidation time is longer than an oxide film stress relaxation time. 11. The method according to claim 1, wherein the second step is performed under an atmosphere containing oxygen (O ₂ ) and an inert gas at a temperature T of less than about 1070 ° C.
(℃) carried by, and in the oxygen partial pressure in said second step (P _O2) is _{t 1> τ t 1 = Δx} (Δx + 2x i + A) / B × 60 (s) Δx = 0.36 (nm) x _i = 5 (nm) A = A ₀ exp (α / (k (T + 273.15))) A ₀ = 0.226 (nm) α = 0.666 (eV) k = 8.617 × 10 ⁻⁵ (EV · K ⁻¹ ) B = B ₀ exp (−β / (k (T + 273.15))) · CO ₂ B ₀ = 3.14 × 10 ⁸ (nm ² · min ⁻¹ ) β = 1.620 (EV) k = 8.617 × 10 ⁻⁵ (eV · K ⁻¹ ) CO ₂ = PO ₂ (atm) / 1 (atm) CO ₂ is a dimensionless coefficient τ = η / μη = corresponding to the oxygen concentration. η ₀ exp (γ / (k (T + 273.15))) η ₀ = 2.3 × 10 ⁻⁶ (dyn · s · cm ⁻² ) γ = 4.85 (eV) k = 8.617 × 10 ^{− 5} (eV · K ^-1 method of manufacturing a thin film semiconductor device according to any one of claims 1 to 8, characterized in that performing under conditions satisfying the formula of ^{μ = 3.15 × 10 11 (dyn} · cm -2). 12. A method for manufacturing a thin film semiconductor device, comprising at least a first step of forming a semiconductor film mainly composed of silicon (Si) on a substrate and a second step of thermally oxidizing the surface of the semiconductor film. Prior to the first step, the substrate is subjected to a first heat treatment. Thereafter, in the first step, a higher order silane (Si _n H _{2n + 2} : n = 2,3) is formed by a vapor deposition method (CVD method). And 4) forming a semiconductor film by depositing an amorphous film as a kind of source gas and crystallizing the amorphous film to form a semiconductor film. 13. The method according to claim 12, wherein the first heat treatment is performed at a predetermined temperature between about 800 ° C. and about 1100 ° C. 14. The method according to claim 12, wherein the vapor deposition is a low pressure chemical vapor deposition (LPCVD). 15. The method according to claim 14, wherein the low-pressure chemical vapor deposition is performed by a high-vacuum low-pressure chemical vapor deposition apparatus. 16. The thin film semiconductor device according to claim 15, wherein said high vacuum type low pressure chemical vapor deposition apparatus has a background vacuum of 5 × 10 ⁻⁷ Torr or less immediately before semiconductor film deposition. Production method. 17. The low-pressure chemical vapor deposition method ratio higher silane flow rate _{(Q SiH) (R = Q} L / Q SiH) is 10ppm for in leak rate to a low pressure chemical vapor deposition apparatus (Q _L)
^{15. The} method for manufacturing a thin film semiconductor device according to claim 14, wherein the method is performed in a state where the degree is not more than about (R ≦ 10 ⁻⁵ ). 18. The low pressure chemical vapor deposition method has a deposition temperature of less than about 430 ° C. and a deposition rate of 0.5 nm / mi.
15. The method according to claim 14, wherein the step is performed in a state of about n or more.
18. The method for manufacturing a thin film semiconductor device according to any one of claims 17 to 17. 19. The method of manufacturing a thin film semiconductor device according to claim 12, wherein the crystallization of the amorphous film in the first step proceeds in a solid phase. 20. A method according to claim 1, wherein the crystallization of the amorphous film in the first step is performed by heat-treating the amorphous film at a predetermined temperature between about 500 ° C. and 650 ° C. The method for manufacturing a thin-film semiconductor device according to claim 12. 21. The crystallization of the amorphous film in the first step is performed by subjecting the amorphous film to a heat treatment at a predetermined temperature between about 550 ° C. and about 600 ° C. The method for manufacturing a thin-film semiconductor device according to claim 12. 22. The method according to claim 1, wherein the second step is performed under an oxidizing atmosphere.
22. The method of manufacturing a thin film semiconductor device according to claim 12, wherein the temperature is lower than about 070.degree. C. and the time for oxidizing the monoatomic layer is longer than the time for relaxing the oxide film stress. 23. The method according to claim 23, wherein the second step is performed under an atmosphere containing oxygen (O ₂ ) and an inert gas at a temperature T of less than about 1070 ° C.
(℃) carried by, and in the oxygen partial pressure in said second step (P _O2) is _{t 1> τ t 1 = Δx} (Δx + 2x i + A) / B × 60 (s) Δx = 0.36 (nm) x _i = 5 (nm) A = A ₀ exp (α / (k (T + 273.15))) A ₀ = 0.226 (nm) α = 0.666 (eV) k = 8.617 × 10 ⁻⁵ (EV · K ⁻¹ ) B = B ₀ exp (−β / (k (T + 273.15))) · CO ₂ B ₀ = 3.14 × 10 ⁸ (nm ² · min ⁻¹ ) β = 1.620 (EV) k = 8.617 × 10 ⁻⁵ (eV · K ⁻¹ ) CO ₂ = PO ₂ (atm) / 1 (atm) CO ₂ is a dimensionless coefficient τ = η / μη = corresponding to the oxygen concentration. η ₀ exp (γ / (k (T + 273.15))) η ₀ = 2.3 × 10 ⁻⁶ (dyn · s · cm ⁻² ) γ = 4.85 (eV) k = 8.617 × 10 ^{− 5} (eV · K ^-1 claim, characterized in that performing under conditions satisfying the formula of ^{μ = 3.15 × 10 11 (dyn} · cm -2) 12
21. The method for manufacturing a thin-film semiconductor device according to any one of claims 20 to 20.