JPH11284202A - Thin film insulated gate semiconductor device and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly reliable thin film insulated gate semiconductor device by preventing the diffusion of impurities. SOLUTION: In a thin film insulated gate semiconductor device having an insulating layer composed of a plurality of insulating films provided on an insulating substrate 11 and a semiconductor layer formed on the insulating layer, the insulating film which is in contact with the semiconductor layer of the insulating layer is composed of a silicon oxide film containing phosphorus at a rate of 1×10<19> to 5×10<20> cm<-3> . The phosphorus suppresses the occurrence of fixed charges by preventing the diffusion of impurity ions, such as hydrogen ions, sodium ions, etc., by gettering (incorporating) the impurity ions.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gate insulating film of an insulated gate field effect transistor used as an element of a semiconductor integrated circuit or a driving element of a large area liquid crystal display device, and an insulating film of a thin film semiconductor device provided on a substrate. About the membrane.

[0002]

2. Description of the Related Art An active element or a semiconductor integrated circuit using an insulator film formed by a chemical vapor method or the like,
Alternatively, a capacitor using a dielectric film has attracted widespread attention.

This insulating film (which is simply referred to as an insulating film or an insulating film because a fusion film of a capacitor is also insulating) is conventionally formed by a chemical vapor deposition method or the like. Can be formed at a low temperature of 450 ° C. at the maximum, and inexpensive soda glass, borosilicate glass, or the like can be used as the substrate.

As another method for producing an insulator at such a low temperature, a silicon oxide film formed by a plasma CVD method or a sputtering method using 100% to 80% of Ar atoms as a sputtering gas is known.

Further, it has been attempted to form a silicon oxide film as a gate oxide film of an insulated gate field effect transistor by a photo-CVD method. In this case, there is no reaction damage with the underlying semiconductor or electrode material and an interface state density of about 2 × 10 ¹⁰ eV ^-1 cm ^-2 is obtained, but the time required for film formation is long (composition Film speed is very slow), which is not suitable for industrial applications. In addition, since hydrogen is used to induce a hot electron effect, there is a problem in long-term characteristics.

[0006]

As a problem of the conventional insulating film, there is a problem that impurities such as sodium and hydrogen become fixed charges at the interface of the semiconductor layer and an interface state is formed due to the presence of an unpaired bond. Was. As a result, the threshold voltage of the insulated gate field effect transistor is increased, and the electrical performance of the semiconductor device is reduced. In addition, if a fixed charge is present at the interface, the fixed charge moves every time a voltage is applied. As a result, there is a problem that the reliability of the semiconductor device is reduced.

Conventionally, a semiconductor layer is directly formed on a glass substrate. However, a problem arises in that impurities diffuse from the glass substrate into the semiconductor layer during a later step such as thermal annealing. In particular, when low-cost soda glass is used as the substrate, diffusion of sodium ions from the substrate becomes a serious problem. As a method for solving this problem, there is a method in which a silicon oxide film is formed as a buffer layer on a glass substrate, but diffusion of impurities cannot be completely prevented. Further, a new problem of formation of an interface state at the interface with the semiconductor layer has occurred.

It is an object of the present invention to provide a highly reliable semiconductor device having an insulating film which prevents diffusion of impurities and has a low interface state without fixed charges and dangling bonds. And

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A first aspect of the present invention is to provide a gate insulating film having a low interface state and excellent electrical stability in an insulating gate type semiconductor device provided on a substrate. Phosphorus in a film such as a silicon oxide film is 1 × 10 ¹⁹ to
It is characterized in that so-called phosphorus glass is formed in an amount of 5 × 10 ²⁰ cm ^−3, preferably 1 × 10 ^{20 to} 3 × 10 ²⁰ cm ⁻³ .

Impurities such as hydrogen ions and sodium ions which are impurities are gettered (taken in) by the presence of phosphorus, diffusion of these impurity ions is prevented, and generation of fixed charges is suppressed. In this case, boron, carbon nitrogen, boron, or the like can be used in addition to phosphorus, and the insulating film can be made of alumina to which the above impurities are added, instead of a silicon oxide film.

When boron, which is an impurity imparting one conductivity type, diffuses into the semiconductor layer, the semiconductor layer undesirably becomes one conductivity type. Therefore, contamination of the semiconductor layer with impurities must be avoided as much as possible.

Therefore, it is desirable that phosphorus or boron in the insulating film is 5 × 10 ²⁰ cm ⁻³ or less.

It is needless to say that the configuration of the present invention can be used for a capacitor which is a dielectric film such as a DRAM (dynamic memory).

According to a second aspect of the present invention, in the insulating gate type semiconductor device provided on the substrate, the gate insulating film is constituted by a plurality of layers in order to realize a gate insulating film having a lower interface state.

For example, when the gate oxide film is composed of two layers, the first layer in contact with the semiconductor layer forming the channel formation region uses a silicon oxide film to which no impurity is added artificially. The second silicon oxide film provided over the silicon film contains phosphorus at 1 × 10 ²⁰ cm ⁻³ or more.

In this case, the first silicon oxide film containing no artificial impurities has a blocking effect on the diffusion of phosphorus, and the second silicon oxide film containing a high concentration of phosphorus or boron has an impurity. Since a strong gettering effect is generated, electrical stability and reliability of the insulated gate semiconductor device can be realized.

The first silicon oxide film contains fluorine element.
Mixing 0.05 to 5 atomic% neutralizes dangling bonds of silicon and hydrogen separated from silicon during thermal annealing, and hydrogen bonded to silicon forms a hydrogen bond with fluorine, so that silicon has a fixed charge. And lowering the interface state density to obtain a low threshold voltage.

Further, in this specification, what is simply expressed as silicon oxide means one to which no impurity is added artificially.

A third aspect of the present invention uses a silicon oxide film containing phosphorus as an insulating film provided on a substrate.

For example, in a semiconductor device provided on a glass substrate, when a silicon oxide film containing phosphorus is provided as a buffer layer on the glass substrate in order to prevent impurities from the glass substrate from diffusing into the semiconductor layer, phosphorus is reduced. Since the impurity ions, particularly sodium ions, diffused from the glass substrate are gettered to prevent the diffusion, diffusion of these impurity ions into the semiconductor layer can realize a highly reliable semiconductor device.

According to a fourth aspect of the present invention, there is provided a semiconductor device comprising an insulating layer composed of a plurality of layers provided on a substrate and a semiconductor layer provided on the insulating layer. At least one layer in contact with a semiconductor layer is silicon oxide, and at least another layer is a silicon oxide film containing phosphorus.

For example, in an insulating gate type field effect semiconductor device provided on a glass substrate, a first silicon oxide film containing 1 × 10 ²⁰ cm ⁻³ or more of phosphorus on a glass substrate and an impurity containing no impurities When an insulating layer made of a second silicon oxide film not provided is provided, and an insulating gate type field effect semiconductor device is provided on this insulating layer, the insulating layer serves as a barrier against diffusion of impurities from the glass substrate into the semiconductor layer. The first silicon oxide film containing phosphorus acts, and the second silicon oxide film acts as a barrier so that the phosphorus in the first silicon oxide film containing phosphorus does not diffuse into the semiconductor layer. .

This second silicon oxide film is doped with fluorine
The addition of 5 atomic% is effective in neutralizing dangling bonds and lowering the interface state as in the case of the second invention. In addition, other than the fluorine element, any halogen element can be used, and it is effective to mix the element with any silicon oxide film which is an insulating film.

It goes without saying that the configuration of the present invention described above can be applied to a dielectric film such as a capacitor.

In all the structures of the present invention, the silicon oxide film is made of boron glass using boron, nitrogen or carbon instead of phosphorus, or the silicon oxide film is doped with carbon or nitrogen to form a Si—C bond. In addition, even if a Si—N bond is formed, the effect is the same as when phosphorus is used. Further, alumina may be used instead of silicon oxide.

In the following, the structure of the present invention, the production method,
Show the effect. Note that a thin film device such as a photoelectric conversion device can be used as the semiconductor device.

[0027]

[Embodiment 1] This embodiment is directed to an insulating gate type semiconductor device provided on a substrate according to the first structure of the present invention, wherein phosphorus is added to a gate insulating film of the insulating gate type semiconductor device. It is characterized by being included. Is a DR consisting of an insulated gate semiconductor device and a capacitor.
This is an example in which the present invention is applied to a metal oxide film such as a dielectric such as tantalum oxide and titanium oxide and a ferroelectric such as barium titanate used as a capacitor of an element of an integrated circuit such as AM.

In this embodiment, such an insulating film is formed by a sputtering method. 0.001 The PH ₃ gas in order to include phosphorus (P) in the insulating film used for the sputtering 30
Vol%, preferably comprises from 0.1 to 5 vol%, and oxides, for example, oxygen, more preferably more than 75 vol% relative to the inert gas such as argon not a for any inert gas, a PH ₃ 0.
001-30 vol%, preferably 0.1 to 5% by volume inclusive oxide gas, a metal oxide or metal other particularly in an oxygen atmosphere containing PH ₃ 0.1 to 5% by volume - perform sputtering target, the oxide insulating It is characterized in that the film is produced by a lamination method.

In sputtering, a sputter gas is deposited.
Gas as part of the components of the coated film, such as tantalum oxide film
, The oxygen content is more than 95%, PH_ThreeIs P 1 × 10¹⁹~Five
× 10 ²⁰cm^-3Preferably 1 × 10²⁰~ 3 × 10²⁰cm^-3Included in the film
0.1 to 5% by volume of tantalum oxide
Get is performed using a radio frequency (RF) sputtering method. Then ta
The oxygen being the sputter gas during the flight of the get material
And the oxidation reaction can be performed more completely.
P (phosphorus) mixed into the film prevents intrusion of impurities such as Na
A highly reliable oxide insulating film.
Wear. To further promote this, in addition to this, halogen
Simultaneously 0.2 to 20% by volume of gas containing element to oxide gas
To the silicide at the same time
Neutralization of incoming alkali ions and neutralization of unpaired bonds
Can be possible. The spatter used in the present invention
Any of the sputtering methods such as RF sputtering and DC sputtering
Method can be used, but the sputtering target is conductive
Oxides with poor rates, such as Ta _TwoO_FiveIn the case of metal oxides such as
13.56MHz high-frequency RF magnet to maintain stable discharge
It is preferable to use a netron sputtering method.

Oxygen (O ₂ ), ozone (O ₂ )
₃ ) and nitrous oxide (N ₂ O). In particular, when ozone or oxygen is used, there is no unnecessary atom incorporated in the oxide insulating film, so that an insulating film having no pinholes, having little dielectric damage, and having a large variation in withstand voltage is formed. Could get on the surface.

Since boron may be used instead of phosphorus, B ₂ H ₆ can be used instead of PH ₃ .

Tantalum oxide and titanium oxide are typical examples of the oxide insulating film. Barium titanate and lead titanate are mainly used as ferroelectric oxides. Nitrogen fluoride (NF ₃ , N ₂ F ₄ ), hydrogen fluoride (HF), fluorine
(F ₂ ), Freon gas may be used. Easily decomposed chemically,
NF ₃ is easy to use as a fluoride gas which is easy to handle. As chloride gas, carbon tetrachloride (CCl ₄ ), chlorine (C
l ₂ ), hydrogen chloride (HCl) and the like can be used.

The amount of these nitrogen fluorides is, for example, 0.2 to 20% by volume based on the oxide gas such as oxygen. These halogen elements are effective in heat treatment for neutralization with alkali ions such as sodium in the oxide insulator and neutralization with unpaired metal bonds. It is not good because there is a possibility to do it. Generally, a halogen element of 0.01 to 5 atomic% of the total number of elements was mixed in the coating.

The use of ozone as a gas for sputtering easily decomposed ozone into O radicals, generated a large amount of O radicals per unit area, and contributed to an improvement in film forming speed.

What has been described above is in the atmosphere at the time of sputtering.
PH_ThreeEtc., but the atmosphere is an oxidizing gas
For example, in an atmosphere of 100% oxygen, P (phosphorus) or
1 x 10 boron¹⁹~ 5 × 10²⁰cm^-3Added at a concentration of
Can be used to form an oxide insulating film.
You. This means that phosphorus or boron is 1 × 10
¹⁹~ 5 × 10²⁰cm^-3Preferably 1 × 10²⁰~ 3 × 10²⁰cm^-3Including
To avoid.

The details of the embodiment will be described below. First, a tantalum oxide film was formed on a silicon semiconductor by a sputtering method in an oxygen atmosphere to which PH ₃ was added, and an aluminum electrode of 1 mmφ was formed thereon by electron beam evaporation, and the electrical characteristics were examined. As shown in FIG.

FIG. 1 shows a BT (bias-temperature) process.
And apply a negative bias voltage of 2 × 10 to the gate electrode side.⁶V
/ cm 2 at 150 ° C for 30 minutes, and add a positive
The difference between them when the
Voltage deviation (ΔVFB) and PH _Three% By volume and PH_Three/ O_Twoconnection of
FIG. What is a flat band voltage?
The voltage required to cancel the effect of the fixed charge inside,
The lower this voltage is, the better the electrical stability and reliability of the insulating film
Will be higher.

When a voltage is applied, the flat band voltage V _FB
Fluctuating indicates that it is electrically unstable.

As is clear from FIG. 1, ΔVFB was 3 V when PH ₃ was 0% by volume. However, when this film was formed in an atmosphere containing 5% by volume of PH _{3 and} 95% by volume of oxygen, the value was only 0.5 V or less. Furthermore, when a small amount of a halogen element was added, the value was sharply reduced by a few minutes.

The above effect is considered to be due to the fact that P has a gettering effect on impurities such as Na which are inevitably mixed into the insulating film, thereby suppressing generation of fixed charges.

If PH ₃ is increased to more than 5%, when the present invention is applied to a semiconductor device, phosphorus (P) diffuses into the semiconductor layer and the silicon substrate becomes N-type. This causes a problem such as leakage between elements, which makes the semiconductor device unsuitable.

[Embodiment 2] In this embodiment, as in Embodiment 1, the first configuration of the present invention is used for a capacitor of an insulated gate semiconductor device provided on a silicon substrate.

FIG. 2 shows a process for forming the insulating film of this embodiment. In this embodiment, glass is used as the substrate material.
Used as (1). On the substrate (1), the lower electrode (2) is formed in an island shape by the sputtering method using only O ₂ , and FIG.
Get the state of.

The manufacturing conditions are as follows. A substrate temperature of 350 ° C. The reaction pressure during 0.06 Torr Rf power - (13.56 MHz) 100 W data - target tantalum metal using gas O ₂ thickness 2000Å

In forming the island shape, a metal mask is used in the embodiment, but a known photolithography technique may be used.

On this, an insulating film (3) of tantalum oxide was formed by the method of the present invention. The conditions are shown below.

Next, Al was formed as an upper electrode (4) by electron beam evaporation to complete a capacitor.

FIG. 3 shows PH ₃ in the atmosphere at the time of sputtering.
Shows the relationship between the volume% of the and the withstand voltage. The dielectric breakdown voltage was measured by setting the voltage at which the leak current measured by a 1 mm φ Al electrode exceeded 1 μA as the dielectric breakdown voltage.

Since there is variation among samples, X (marked at the center) and σ (dispersion sigma value) (upper and lower limits) are shown in the figure. This pressure resistance is the volume% of PH ₃ in the atmosphere at the time of film formation.
Is more than 1%, the value rapidly increases, and the σ value also decreases. Therefore, it is understood that the addition of PH ₃ should be 1% by volume or more in an oxygen atmosphere at the time of film formation.

In addition to this, NF ₃ etc.
The addition of 0.2 to 20% by volume further improves the electrical stability and reliability.

However, if the addition amount of PH ₃ is set to 5% by volume or more, when this insulating film is applied to a semiconductor device, a problem of phosphorus diffusion into the semiconductor layer occurs, and the electrical characteristics and reliability of the semiconductor device are deteriorated. There was an invitation problem.

It is preferable that all materials used for sputtering have high purity. For example, sputtering
The get is most preferably 4N or more of tantalum oxide, titanium oxide, barium titanate, and lead titanate. Similarly, the gas used for sputtering was of high purity (5N or more), and the mixing of impurities into the insulating film was minimized.

[Embodiment 3] This embodiment is an example in which the first structure of the present invention is obtained by a sputtering method. In this embodiment, an oxide insulating film of an insulating gate type semiconductor device is formed by a sputtering method using no hydrogen by using a target to which phosphorus is added.

FIG. 4 shows this embodiment. This embodiment uses 1Tr
The present invention is used for manufacturing one cell of DRAM (dynamic memory) of / Cell. In the drawing, one insulated gate field effect transistor (40) is provided on the semiconductor substrate.
Is the source or drain (48), the drain or source (4
9), a gate electrode (47), and a gate insulating film (46). In addition, one drain or source (49) of this transistor has a lower electrode (410) and a tantalum oxide dielectric.
(411), a capacitor (421) composed of an upper electrode (412) is provided in series. A buried insulating film (45) is provided around these outer periphery. This structure is a stacked DRAM
Of the memory cell of FIG. In this drawing, the dielectric film of the capacitor (411) is a phosphorous film of tantalum oxide.
Using a target added with 1 × 10 ^{19 to} 5 × 10 ²⁰ cm ^-3 ,
A film was formed by a sputtering method using 100% oxygen.

This tantalum oxide has a relative dielectric constant of 27,
Silicon oxide coating due to excellent frequency characteristics up to high frequencies
(Relative dielectric constant: 3.8), a large storage capacity can be obtained.

The gate insulating film of the insulated gate field effect transistor (40) was made of silicon oxide by thermal oxidation or silicon oxide by sputtering using 100% oxygen of silicon oxide. However, even if this protective film was made of tantalum oxide, the interface state with the silicon semiconductor was only 2 × 10 ¹⁰ cm ⁻² , which was good.

The lower electrode (41) of the capacitor (421)
0) was formed using a silicon semiconductor to which phosphorus was added. However, this electrode material may be metal tantalum, tungsten, titanium, molybdenum, or a silicide thereof.

In this embodiment, the tantalum oxide film (411) on the lower electrode (410) is coated with phosphorus at a concentration of 1 × 10 ^{19 to} 5 × 10 ²⁰ cm ^−3.
Was formed by a sputtering method in a 100% oxygen atmosphere using a target added at a concentration of 1%. Furthermore, an upper electrode (41
2) was formed of aluminum or a multilayer film of tantalum metal and aluminum to form a capacitor (421). The thickness of tantalum oxide was 300 to 3000 mm. Typically 50
0 to 1500 °, for example, 1000 °. However, since the relative permittivity of silicon oxide or the like is small, the thickness of the memory cell must be reduced to about 30 °. However, since tantalum oxide formed by the method of the present invention has a large relative dielectric constant, its thickness can be, for example, 1000 °. As a result, the insulating properties were excellent, and the presence of pinholes could be reduced.

Therefore, in FIG. 4, the channel length of the insulated gate field effect transistor is set to 0.1 to 1 μm, for example, 0.1 μm.
5 μm, 20 μm for 1Tr / Cell size
One memory (1 bit) could be manufactured in the box.

In forming the tantalum oxide, the tantalum oxide is formed by a sputtering method containing no hydrogen, and the upper and lower electrodes are formed by the sputtering method containing no hydrogen.
It is also possible to prevent hydrogen during the film formation from drifting (diffusing) to the gate insulating film by the subsequent heat treatment and becoming a hot carrier trap center.

It goes without saying that boron can be used instead of phosphorus.

According to the method of the present invention, a thin film transistor having very good characteristics can be easily formed only by a low-temperature process.

Further, since the generation of hot carriers and fixed charges existing in the gate insulating film can be reduced, it is possible to provide a highly reliable transistor and capacitor with little characteristic change in long-term use. became.

The shape of the capacitor or the insulated gate transistor used in the present invention does not need to be a staggered type, but may be an inverted staggered type or a vertical channel type transistor. Further, an insulated gate field effect transistor used as a part of a monolithic IC using single crystal instead of non-single crystal for silicon of the transistor may be used.

Also, the capacitor may be a multilayered multilayer structure instead of a single-layer dielectric capacitor, or may be a side-by-side system in which electrodes are sandwiched between left and right instead of vertically. It goes without saying that these can be applied to all the embodiments in this specification.

[Embodiment 5] This embodiment is a third embodiment of the present invention, wherein a silicon oxide film containing phosphorus which is an insulating film provided on a substrate and a silicon oxide film containing the phosphorus A semiconductor device including a semiconductor layer provided on a film is applied to an insulated gate semiconductor device provided on a glass substrate.

This embodiment relates to a silicon oxide film containing phosphorus provided on an insulating substrate and an insulated gate field effect transistor provided on the silicon oxide film. What is claimed is: 1. An insulating gate type semiconductor device, wherein a halogen element and phosphorus are mixed in at least one of a gate insulating film of an insulating gate type field effect transistor, wherein the substrate is in an atmosphere of hydrogen or an inert gas containing hydrogen. A step of forming a semiconductor film by a sputtering method thereon, and containing a fluoride gas, PH ₃ and an oxide gas or a fluoride gas, an oxide gas and PH ₃ before or after forming the semiconductor film obtained by the sputtering method. A silicon oxide film is formed by a sputtering method in an atmosphere of the inert gas thus formed, and a part of the semiconductor film is formed as a channel formation region of an insulating gate type semiconductor device, and the oxidation is performed. Some of Motomaku is obtained by the gate insulating film.

As an example of a method of forming a part of the semiconductor film as a channel formation region, an amorphous material (amorphous or extremely amorphous) obtained by sputtering in hydrogen or an inert gas atmosphere containing hydrogen is used. near)
A semiconductor film (hereinafter referred to as a-Si) at 450 ° C. to 700 ° C.
Typically, by applying a temperature of 600 ° C. to the semiconductor film to crystallize at least the channel formation region, the insulated gate semiconductor device of the present invention can be obtained.

The semiconductor film after the crystallization has an average crystal grain size of about 5 to 400 ° and a hydrogen content in the semiconductor film of 5 atomic% or less. In addition, the semiconductor film having this crystallinity has lattice distortion, and the interfaces of the crystal grains are in close contact with each other microscopically, and have an effect of eliminating a barrier for carriers at the crystal grain boundaries. For this reason, impurity atoms such as oxygen segregate and form barriers (barriers) at the polycrystalline grain boundaries having no lattice distortion and hinder the movement of carriers, but have lattice distortion as in the present invention. In this case, a barrier was not formed or its existence was negligible, so that the electron mobility also had very good characteristics of 5 to 300 cm ² / V · S.

Further, the semiconductor film obtained by the plasma CVD method has a large proportion of an amorphous component, and the amorphous component is naturally oxidized to form an oxide film to the inside. On the other hand, the sputtered film is dense and natural oxidation does not proceed to the inside of the semiconductor film, and is oxidized only near the surface. Due to the denseness, crystal grains having lattice distortion are strongly pressed against each other, and there is a feature that an energy barrier for carriers is not formed near the crystal grain interface.

FIG. 5 shows a manufacturing process of the thin film transistor manufactured in this embodiment. First, a SiO ₂ film (12) containing phosphorus was formed on a glass substrate (11) by a magnetron type RF sputtering method under the following conditions to a thickness of 100 nm to 2 μm and 200 nm in this embodiment. Uses silicon as target

The PH ₃ concentration can be added in the range of 0.01% to 10%, and NF ₃ can be added in the range of 0 to 20%.

Further, an a-Si film (13) serving as a channel formation region is further deposited on the film by a magnetron type RF sputtering apparatus.
A film having a thickness of 0 nm was formed to obtain the shape shown in FIG. The deposition conditions were as follows: H ₂ / (H ₂ + Ar) = 80% (partial pressure ratio) in an atmosphere of inert gases such as argon, hydrogen, and PH _3. Deposition temperature 150 ° C RF (13.56 MHz) output 400 W The pressure was 0.5 Pa, and a single crystal silicon target was used as the target.

Thereafter, a temperature range of 450 ° C. to 700 ° C., especially 60 ° C.
At a temperature of 0 ° C. for a period of 10 hours in a hydrogen or inert gas, in this example, in a 100% nitrogen atmosphere, a-
The thermal crystallization of the Si film (13) was performed to produce a silicon semiconductor layer having high crystallinity. Note that the a-Si film (1
When 3) is formed by a sputtering method, a non-single-crystal silicon target is used, and when the input power is reduced, a dense crystal state having a negligible particle size and lattice distortion can be obtained.

The amount of oxygen impurities present in the semiconductor film formed by such a method is 2 × by SIMS analysis.
10 ²⁰ cm ^-3 , carbon was 5 × 10 ¹⁸ cm ^-3 , and the content of hydrogen was 5% or less. Since the value of the impurity concentration using the SIMS changes in the depth direction in the semiconductor film, the concentration in the depth direction was examined and described with the minimum value. This is because a natural oxide film exists near the surface of the semiconductor film. Further, the value of the impurity concentration did not change even after the crystallization treatment.

This impurity concentration is naturally a low value.
Is advantageous when used as a semiconductor device
It is clear that the semiconductor film of the present invention has crystallinity.
At the same time as having lattice distortion, barrier at the crystal grain boundary
Is not formed and 2 × 10²⁰cm ^-3About oxygen impurity concentration
Even if present, low degree of hindrance to carrier movement
No practical problems occurred.

As can be seen from the laser Raman analysis data shown in FIG. 6, the position of the peak indicating the presence of crystals in this semiconductor film has a lower wave number than the position of the peak (520 cm ^-1 ) of normal single crystal silicon. Side, and the existence of lattice distortion was suppressed.

In FIG. 6, (64) represents (6) when H ₂ / (H ₂ + Ar) = 80% when the film of FIG.
3) In the case of _{H 2 / (H 2 + Ar} ) = 50%, (62) is _{H 2 / (H 2 + Ar} ) = 20%
In the case of (61), (61) is the case where H ₂ / (H ₂ + Ar) = 0%.

In the present embodiment, the present invention is described using a silicon semiconductor. However, it is also possible to use a germanium semiconductor or a semiconductor in which silicon and germanium are mixed. It was possible to reduce the temperature added during crystallization by about 100 ° C.

In order to form a still more dense semiconductor film or silicon oxide film, the substrate or the flying target particles in flight are sputtered in the above-mentioned hydrogen atmosphere or an atmosphere of hydrogen and an inert gas. 1000nm
The following intense light or laser irradiation may be applied continuously or in pulses.

The thermally crystallized silicon semiconductor film is subjected to device isolation patterning to obtain the shape shown in FIG.
A part of this semiconductor film was formed as a channel formation region of an insulating gate type semiconductor device.

Next, a silicon oxide film (SiO ₂ ) (15) is
m In this embodiment, a magnetron type R
A film was formed by the F sputtering method under the following conditions. Oxygen 92% by volume NF ₃ 5% by volume PH ₃ 3% by volume Pressure 0.5pa Film forming temperature 100 ° C RF (13.56MHz) output 400W As the target, a silicon target or a synthetic quartz target was used.

In this case as well, when the input power is reduced by using an amorphous silicon target, a dense silicon oxide film in which fixed charges do not easily exist can be obtained.

Further, phosphorus is added to the target in an amount of 1 × 10 ^{19 to} 5
× 10 ²⁰ cm ^{-3 can be} mixed in advance and formed by sputtering in an atmosphere of 100% oxygen, whereby hydrogen can be prevented from being mixed into the formed silicon oxide film, and Can be prevented from becoming a hot carrier trap center in the subsequent thermal annealing step.

Further, by mixing a gas containing a halogen element with 0.2 to 20% by volume of the oxide gas at the same time, neutralization of alkali ions simultaneously and reluctantly introduced into silicide oxide, Sum can also be possible.

As the sputtering method used to obtain the structure of the present invention, any method such as RF sputtering and DC sputtering can be used. However, when the sputtering target is an oxide having low conductivity, for example, SiO ₂ or the like, stable sputtering can be performed. It is preferable to use the RF magnetron sputtering method to maintain the discharge.

As the oxide gas, oxygen, ozone,
Nitrous oxide and the like can be mentioned.

As the gas containing a halogen element, nitrogen fluoride (NF ₃ , N ₂ F ₄ ), hydrogen fluoride (HF), fluorine (F ₂ ), or chlorofluorocarbon can be used as the fluoride gas.

In general, a halogen element of 0.1 to 5 atomic% with respect to silicon is mixed in the film.

It is preferable that all materials used for sputtering have high purity. For example, the sputtering target is most preferably a synthetic quartz of 4N or more, or silicon having a high purity enough to be used for an LSI substrate, and when phosphorus is added, it is preferable to add phosphorus to these high-purity targets.

Similarly, the gas used for sputtering was of high purity (5N or more), and contamination of the silicon oxide film with impurities was avoided as much as possible.

Note that a silicon oxide film as a gate insulating film formed by a sputtering method in an oxygen atmosphere to which a fluoride gas is added as in this embodiment is irradiated with excimer laser light.
It is effective to perform flash annealing to activate halogen elements such as fluorine introduced into the film, to neutralize it with incomplete bonds of silicon, and to remove the cause of generation of fixed charges in the film.

At this time, the activation of the halogen element and the activation of the semiconductor layer under the gate insulating film can be simultaneously performed by appropriately selecting the power and the number of shots of the excimer laser.

In this embodiment, a semiconductor layer containing phosphorus as an impurity imparting one conductivity type is formed on the silicon oxide film (15) by photolithography, and a photolithography process is performed using a predetermined mask pattern. Then, the doped semiconductor film is formed as a gate electrode (20), and FIG.
Was obtained.

As a method for forming the semiconductor layer into which the impurity imparting one conductivity type is mixed, a film forming method such as a sputtering method or a CVD method can be used.

The gate electrode is not limited to the doped semiconductor layer, and other materials can be used. Next, using the gate electrode (20) or the mask used for etching the gate electrode (20) as a mask, the impurity regions (14) and (14 ') were formed in a self-aligned manner by ion implantation. .

As a result, the semiconductor layer (17) under the gate electrode (20) was formed as a channel region of the insulating gate type semiconductor device.

Next, an interlayer insulating film is formed covering all of these upper surfaces.
After forming (18), a hole for contact of the source and drain electrodes is made, metal aluminum is formed on the upper surface by sputtering, and predetermined patterning is performed, and the source and drain electrodes (16) and (16 ′) To complete an insulated gate semiconductor device.

In the case of this embodiment, the semiconductor layer (17) forming the channel region and the semiconductor layer forming the source (14) and the drain (14 ^' ) are made of the same material. To be peeled off. In addition, since the same semiconductor layer is used, the source and drain semiconductor layers also have crystallinity and the mobility of carriers is high, so that an insulated gate semiconductor device having higher electric characteristics can be realized.

Finally, at 375 ° C. in a 100% hydrogen atmosphere.
At this temperature, hydrogen thermal annealing was performed for 30 minutes to complete this example.

This hydrogen thermal annealing is for reducing the grain boundary potential in the polycrystalline silicon semiconductor and improving the device characteristics.

The size of the channel portion (17) of the thin film transistor manufactured in this example in FIG.
The size is 0 μm.

As the characteristics of the thin film transistor using the polycrystalline silicon semiconductor layer manufactured in this example, ID-VD characteristics as shown in FIG. 7 and various characteristics as shown in Table 1 below were obtained.

[0104]

[Table 1]

The S value refers to the relationship between the gate voltage (VG) and the drain current (ID) at the drain voltage (VD) = 10 V, which indicates the characteristics of the device. ) / d (VG)], and the smaller this value is, the steeper the slope of the curve showing the (VG-ID) characteristics is, and the higher the electrical characteristics of the device are. VT indicates a threshold voltage. μ is the carrier mobility and the unit is (cm ² / Vs)
It is.

The on / off characteristics are shown in FIG. 7 (VG-I
D) The logarithmic value of the ratio between the ID value and the minimum ID value at VG = 30 volts in the characteristic curve.

FIG. 8 shows the mobility μ and the a-Si film ((13) in FIG. 5 (a)) which becomes the channel formation region ((17) in FIG. 5 (d)).
FIG. 8 shows the relationship with the hydrogen partial pressure of the atmosphere when producing the same by the magnetron type RF sputtering method. It is apparent from FIG. 8 that the hydrogen partial pressure is preferably set to 100%.

[Embodiment 6] This embodiment is an embodiment in which the second and fourth configurations of the present invention are employed. In this embodiment, the base insulating film and the gate insulating film provided on the glass substrate in Embodiment 3 are used. It is composed of two layers of a silicon oxide film and a silicon oxide film containing phosphorus.

FIG. 9 shows a manufacturing process of this embodiment. The manufacturing method of this example is the same as that of Example 5, except that PH ₃ is 0.1 volume% or more so that phosphorus is contained at least 1 × 10 ²⁰ cm ⁻³ on the glass substrate (11). In
In an oxygen atmosphere containing 10% by volume, the phosphor glass (21) was coated with a magnetron type RF sputtering method under the following conditions at a thickness of 100 mm to 2 μm.
A film was formed to a thickness of μm.

Deposition temperature 150 ° C RF (13.56MHz) output 400W Pressure 0.5 Pa Using molten silicon substrate as target

At this time, if a target in which phosphorus is mixed in at least 1 × 10 ²⁰ cm ⁻³ without using PH ₃ is used, hydrogen does not enter the insulating film and hydrogen is trapped in the insulating film. This is effective because it can be prevented from becoming a center. Further, an amorphous silicon ingot may be used as a target.

Then, a silicon oxide film (12) was formed on the phosphor glass (21) to a thickness of 0.5 to 2 μm in this embodiment by a magnetron type RF sputtering method under the following conditions. O ₂ 100 _0% film-forming temperature 150 ℃ RF (13.56MHz) used in the target output 400W pressure 0.5 Pa monocrystalline silicon

At this time, as in Example 5, the NF
A gas containing a halogen element such as ₃ may be added in an amount of 0.2 to 20%.

When an amorphous silicon substrate target is used as the target, a dense and electrically stable silicon oxide film can be obtained.

The manufacturing method of the semiconductor layer (13) is the same as that of the fifth embodiment. Here, the state shown in FIG. 9A was obtained, and device separation patterning was performed to obtain the shape shown in FIG. 9B.

Next, a silicon oxide film is first formed as a gate insulating film in the same manner as the silicon oxide film (12).

Next, as the second gate oxide film, the phosphor glass was so formed as to contain 1 × 10 ²⁰ cm ⁻³ or more of phosphorus.
A film (22) was formed in the same manner as (21), and through the same steps as in Example 5, the shape shown in FIG. 9 (c) was obtained.

Lastly, the present embodiment was completed in the same manner as in the fifth embodiment. (Fig. 9 (d))

The electrical characteristics of this thin film transistor were as shown in Table 2 below.

[0120]

[Table 2]

As can be seen from Table 2, although the characteristics, S value and mobility of Example 5 do not change so much, the threshold voltage VT is much smaller than that of Example 5.
It can be seen that the on / off characteristics have been improved. In addition, in Example 5, there were many cases of breakage during the last hydrogen annealing, but in this example, the number was very small.

This is because, in the present embodiment, the fixed charge of sodium or the like which causes electrical instability is gettered by phosphorus and the phosphorus does not diffuse into the semiconductor layer, so that the electrical stability is further increased. It is considered that it is.

Needless to say, the above-mentioned boron or the like may be used instead of phosphorus used in this embodiment.

[Brief description of the drawings]

FIG. 1 is a graph showing electrical characteristics in Example 1.

FIG. 2 is a view showing a manufacturing process of a second embodiment.

FIG. 3 is a graph showing electrical characteristics according to a third embodiment.

FIG. 4 is a diagram showing a structure of a fourth embodiment.

FIG. 5 is a view showing a manufacturing process of a fifth embodiment.

FIG. 6 is a graph showing Raman spectra of a polycrystalline semiconductor layer of Example 5 and a comparative example.

FIG. 7 is a graph showing ID-VD characteristics of the fifth embodiment.

FIG. 8 is a graph showing a change in a value of (μ) mobility when a hydrogen partial pressure during sputtering is changed in Example 5;

FIG. 9 is a view showing a manufacturing process of the sixth embodiment.

[Explanation of symbols]

 (1), (11) ... glass substrate (3), (45), (21) ... insulating film (41) ... semiconductor substrate (46), (15), (22) ... Gate insulating film (48), (49). (16), (16 ') ・ ・ ・ Source electrode, drain electrode (20), (47) ・ ・ ・ Gate electrode (40) ・ ・ ・ Insulated gate type semiconductor device

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI H01L 27/04 H01L 29/78 301G 21/822 626C 29/78 627G

Claims (8)

[Claims] 1. A thin-film insulated gate semiconductor device comprising: an insulating layer formed of a plurality of insulating films provided on an insulating substrate; and a semiconductor layer provided on the insulating layer. The insulating film in contact with the semiconductor layer of
A thin-film insulated gate semiconductor device characterized by being a silicon oxide film containing from × 10 ^{19 to} 5 × 10 ²⁰ cm ⁻³ . 2. A thin film comprising: an insulating layer composed of a plurality of insulating films provided on an insulating substrate; a semiconductor layer provided on the insulating layer; and a gate insulating film in contact with the semiconductor layer In the insulated gate semiconductor device, the insulating film of the insulating layer that is in contact with the semiconductor layer has phosphorus of 1%.
A silicon oxide film containing × 10 ^{19 to} 5 × 10 ²⁰ cm ⁻³ , and the gate insulating film contains 1 × 10 ^{19 to} 5 × 10 ²⁰ cm of phosphorus.
^3. A thin-film insulating gate-type semiconductor device, characterized by being a silicon oxide film containing ^-3 . 3. The thin film insulating gate type semiconductor device according to claim 1, wherein said semiconductor layer is obtained by polycrystallizing an amorphous silicon film formed by a sputtering method. 4. The thin-film insulating gate type according to claim 1, wherein the semiconductor layer is obtained by polycrystallizing a mixed film of amorphous silicon and amorphous germanium formed by a sputtering method. Semiconductor device. 5. The thin-film insulated gate semiconductor device according to claim 1, wherein nitrogen is added to said silicon oxide film. 6. A step of forming a plurality of insulating films on an insulating substrate, a step of forming a semiconductor layer on the plurality of insulating films, and a step of forming a gate insulating film on the semiconductor layers. In the method for manufacturing a thin film insulated gate semiconductor device, the insulating film in contact with the semiconductor layer of the plurality of insulating films is a silicon oxide film containing 1 × 10 ^{19 to} 5 × 10 ²⁰ cm ^{−3 of} phosphorus. A method for manufacturing a thin film insulated gate semiconductor device, comprising: 7. A step of forming a plurality of insulating films on an insulating substrate, a step of forming a semiconductor layer on the plurality of insulating films, and a step of forming a gate insulating film on the semiconductor layers. In the method for manufacturing a thin film insulated gate semiconductor device, the insulating film in contact with the semiconductor layer of the plurality of insulating films is a silicon oxide film containing 1 × 10 ^{19 to} 5 × 10 ²⁰ cm ^{−3 of} phosphorus; The gate insulating film has a phosphorous content of 1 × 10 ^{19 to} 5 × 10 ²⁰ cm.
^{3. A} method for manufacturing a thin-film insulated gate semiconductor device, comprising a silicon oxide film containing ^-3 . 8. The method according to claim 6, further comprising a step of irradiating the gate insulating film with excimer laser light.