JPH0395939A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To reduce the number of boundary levels and to improve electric characteristics of a semiconductor device such as a thin film transistor by forming first and second insulating films to become barriers against diffusion of hydrogen at both upper and lower sides of a thin crystalline semiconductor film, injecting hydrogen into the film, and then heat-treating it. CONSTITUTION:A silicon nitride film 12 containing hydrogen is first formed as a first insulating film to become a barrier against diffusion of hydrogen on an insulating board 11 made of glass or the like at 200-300 deg.C substrate temperature. Thereafter, a thin polycrystalline silicon film 13 is formed at the same temperature or temperature equal to or lower than the above temperature. Further, a second insulating film 14 to become a barrier against diffusion of hydrogen is formed thereon. Then, it is heat-treated at higher temperature (300-600 deg.C) than that for forming the first film in a N2, Ar, H2 or mixture gas atmosphere. Since the hydrogen is diffused in the polycrystalline silicon film during the heat-treating, it is trapped to the boundary level of a base boundary, defect level in the thin film or boundary level of grain boundary.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a thin film transistor formed on an insulating substrate.

[Prior Art] Conventionally, a thin film transistor on an insulating substrate (hereinafter referred to as TPT) is produced by forming a semiconductor thin film 32 on an insulating substrate 31 such as glass, and forming an element thereon, as shown in FIG. It was intricately structured.

Furthermore, in recent years, crystalline semiconductor thin films are often used as semiconductor thin films in order to improve the characteristics of TPT. The term "crystalline semiconductor" as used herein refers to a single-crystal semiconductor that has more defects than a normally used single-crystal wafer, or a polycrystalline semiconductor that has one or more internal crystal grain boundaries.

[Problems to be Solved by the Invention] However, in the above-mentioned conventional example, a large number of interface states 33 exist at the interface between the crystalline semiconductor thin film and the substrate, and due to the influence of these interface states, for example, When creating a MOSFET,
Carriers are trapped at a level in the channel part, forming a so-called back channel, causing fluctuations in threshold voltage and on/off
This resulted in deterioration of device characteristics such as a decrease in ff ratio.

Additionally, if an inexpensive material such as glass is used for the substrate, alkali ions such as Na contained in the substrate material will migrate due to heat treatment during the process and exist as mobile ions at the interface with the substrate or in the silicon thin film. This has caused problems with deterioration of device characteristics and reliability.

To solve these problems, it is possible to reduce the levels in the silicon thin film and increase the mobility by using hydrogen passivation using a silicon nitride film by plasma CVD as a protection film for the device after forming the device. It has been done. Further, in order to prevent alkali ion contamination, high-purity quartz, alkali-free glass, or the like may be used as the substrate.

However, even with the above method, the problem of the interface with the substrate has not been solved. In addition, substrates such as high-purity quartz and non-alkali glass are expensive, and TP can be used at low cost for large-area substrates.
There was a problem in forming the T. [Means for Solving the Problems] A first aspect of the present invention is a method for manufacturing a semiconductor device in which a crystalline conductor thin film is formed on an insulating substrate, in which hydrogen is formed on both the upper and lower sides of the crystalline semiconductor thin film. The method is characterized by comprising the steps of forming first and second insulating films that serve as barriers against diffusion of the semiconductor thin film, introducing hydrogen into the semiconductor thin film, and then performing heat treatment. A method of manufacturing a semiconductor device (existing in the past).

[Function] By heat-treating a crystalline semiconductor thin film into which hydrogen is introduced, hydrogen diffuses in the thin film, and the interface states existing at the interface between the crystalline semiconductor thin film and the substrate are trapped by hydrogen, and the interface states are It is expected that the electrical characteristics of semiconductor devices such as TFTs will be improved.

In addition, the hydrogen that has diffused through the thin film is trapped in defect levels in the thin film and interface levels at grain boundaries, causing the TFT to
It can be expected to improve the electrical characteristics of semiconductor devices such as.

Furthermore, by forming a silicon nitride film between the substrate and the semiconductor thin film as an insulating film that acts as a barrier against hydrogen diffusion, a blocking effect is produced against alkali ions such as Na+ from the substrate such as glass. , an improvement in reliability can be expected.

Furthermore, by forming an insulating film on the semiconductor thin film that acts as a barrier against hydrogen diffusion, it is expected that out-diffusion of hydrogen diffused into the thin film will be prevented and the above-mentioned effects will be obtained more stably. can.

Note that the amount of hydrogen introduced is preferably several percent to several tens of atm percent.

(Embodiment) FIG. 1 is a sectional view of a semiconductor device that characterizes the present invention.

In the first embodiment of the present invention, first, a first 8F18 film serving as a barrier against hydrogen diffusion is formed on an insulating substrate 11 made of glass or the like using, for example, a plasma CVO method at a substrate temperature of 200° C. Silicon nitride@12 is formed at 300°C. This silicon nitride @l2 contains several percent to several tens of atm percent hydrogen.

Thereafter, a crystalline silicon thin film 13 is formed at a temperature comparable to or lower than the temperature at which the silicon nitride film 12 was formed.

Crystalline silicon thin films include polycrystalline silicon formed by low pressure CVD, plasma CVD, and our t
In the proposed plasma CVfl method, large-grain polycrystalline silicon obtained by adding hydrogen halide gas such as HCfL to the film-forming atmosphere can be used. The large-grain polycrystalline silicon thin film proposed by us is most suitable for this example from the viewpoint of lowering the process temperature and electrical properties.

Next, a second insulating film l4 that acts as a barrier against hydrogen diffusion is formed on the crystalline silicon.

As an insulating film that acts as a barrier against hydrogen diffusion, a silicon nitride film formed by a low pressure CVD method, a silicon nitride film or a silicon nitride oxide film formed by a plasma CVD method in the same way as the first insulating film are used. A membrane can be used.

Next, in an atmosphere of N2, Ar%H2, or a mixture thereof, a temperature higher than the temperature at which the first insulating film, for example, a silicon nitride film, which acts as a barrier against hydrogen diffusion, is formed (300°C to 100°C) Heat treatment is performed in 'c).

During this heat treatment, the hydrogen present in the silicon nitride film is
By diffusing into the crystalline silicon thin film, it is trapped in the interface states existing at the underlying interface, defect levels in the crystalline silicon thin film, and interface states existing at the grain boundaries of the crystalline silicon, and the underlying interface is trapped. This suppresses the occurrence of back channels at the grain boundary, reduces the potential of grain boundaries, and increases mobility.

In addition, by forming a silicon nitride film between the substrate and the crystalline silicon GI film, Na"
It has a blocking effect against alkali ions such as, improving reliability.

In addition, by forming an insulating film that acts as a barrier against hydrogen diffusion on both sides of the crystalline silicon FiiM, it is possible to prevent out-diffusion from the surface of the crystalline silicon thin film when hydrogen diffuses through heat treatment. The passivation effect can be enhanced.

In the second embodiment of the present invention, first, a first containing insulating film that serves as a barrier against hydrogen diffusion is formed on an insulating substrate 11 such as glass by, for example, a plasma CVD method at a substrate temperature of 200°C. A silicon nitride film l2 is formed at ~300°C. This silicon nitride film i2 contains several percent to several +
Contains atm% hydrogen.

Thereafter, an amorphous silicon thin film 13 is formed at a temperature comparable to or lower than the temperature at which the silicon nitride film 12 was formed.

As the amorphous silicon thin film, amorphous silicon formed by low pressure CVD or plasma CVD, or polycrystalline silicon St" made amorphous by ion implantation, etc., are used.

Next, an insulating film 1 that acts as a barrier against hydrogen diffusion is formed.
4 is formed on amorphous silicon. As an insulating film that acts as a barrier against hydrogen diffusion, a silicon nitride film formed by low-pressure CVO 7, a silicon nitride film formed by a plasma CVD method similar to the first insulating film, or a nitride oxide film are used. A silicon film can be used. Next, N2, Ar, H. Alternatively, the hydrogen-containing insulating film 12, for example, a silicon nitride film, is formed at a temperature (300°C to 6°C) in a mixed gas atmosphere.
Heat treatment is performed at 00°C).

Regarding the temperature of this heat treatment, it is desirable to set the temperature at which the formed non-quality silicon undergoes solid phase crystal growth and crystallization, in order to produce a higher performance TPT.

During this heat treatment, at the same time as the amorphous silicon crystallizes, hydrogen present in the silicon nitride belly diffuses into the silicon where the amorphous silicon has been crystallized by the heat treatment, causing hydrogen to exist at the base interface. It is trapped by interface states, defect levels in crystalline silicon thin films, and interface states existing at grain boundaries of crystalline silicon, suppressing the generation of back channels at the underlying interface, and reducing the potential of grain boundaries. and increase mobility.

Further, by forming a silicon nitride film between the substrate, the crystalline silicon thin film, and q, a blocking effect is provided to alkali ions such as Na'' from the substrate such as glass, and reliability is improved.

In addition, by forming an insulating film that acts as a barrier against hydrogen diffusion on both sides of the amorphous silicon thin film, when hydrogen diffuses during heat treatment, out from the crystalline silicon surface
-diffusion can be prevented, and the passivation effect due to hydrogen can be greatly enhanced.

As a third embodiment of the present invention, first, an insulating substrate ll
A first insulating film that acts as a barrier against hydrogen diffusion is formed on the top by, for example, a plasma CVD method or a low pressure CVT+ film. e
Then, a silicon nitride film l2 is formed.

Thereafter, the crystalline silicon thin film 13 is shaped. Crystalline silicon thin films include polycrystalline silicon formed by low-pressure CVD and plasma CVD, non-quality silicon that is annealed and recrystallized, and our proposed plasma CVD method. Large-grain polycrystalline silicon obtained by the effect of adding hydrogen halide gas such as HCi to the atmosphere, and the present applicant's patent application No. 82-7362
No. 9, the large-grain polycrystalline silicon proposed in Japanese Patent Application No. 62-73630, and the present applicant's patent application No. 63-1
Single crystal silicon formed on a non-quality substrate as proposed in No. 07016 is used.

Next, hydrogen gas is introduced into the chamber using a plasma CVD apparatus, and then a discharge is generated to introduce hydrogen into the crystalline silicon thin film using hydrogen plasma.

Next, a second insulating film l is formed which acts as a barrier against hydrogen diffusion.
4 on crystalline silicon. As an insulating film that acts as a barrier against hydrogen diffusion, a silicon nitride film formed by a low pressure CVD method, a silicon nitride film or a silicon nitride oxide film formed by a plasma CVD method can be used.

Next, heat treatment is performed in an atmosphere of N2, Ar, H2, or a mixed gas thereof.

During this heat treatment, hydrogen introduced from the plasma diffuses into the crystalline silicon thin film. is trapped by the interface states existing at the grain boundaries, suppressing the generation of back channels at the underlying interface, reducing the potential at the grain boundaries, and increasing mobility.

Further, by forming a silicon nitride film between the substrate and the crystalline silicon thin film, a blocking effect is provided to alkali ions such as Na'' from the substrate such as glass, and reliability is improved.

In addition, by forming an insulating film on both sides of the crystalline silicon thin film that acts as a barrier against hydrogen sales, it is possible to prevent out-diffusion from the surface of the crystalline silicon thin film when hydrogen is diffused by heat treatment. The vacibation effect can be enhanced.

As a fourth embodiment of the present invention, first, a first insulating film that serves as a barrier against hydrogen diffusion is formed on an insulating substrate 11 such as glass by, for example, plasma CVD.
A silicon nitride film l2 is formed by a method or a low pressure CVD method.

Thereafter, a crystalline silicon thin film 13 is formed. Crystalline silicon thin films include polycrystalline silicon formed by low-pressure CVD or plasma CVD, amorphous silicon that is annealed and recrystallized, and crystalline silicon formed by our proposed plasma CVD method. HC42 into the membrane atmosphere
Large grain size polycrystalline silicon obtained by the addition effect of hydrogen halide gas such as
No. 3629, the large-grain polycrystalline silicon proposed in Japanese Patent Application No. 82-73630, and the present applicant's patent application No. 5
Single crystal silicon formed on a non-quality substrate as proposed in No. 3-107016 is used.

Next, the second insulation @l acts as a barrier against hydrogen diffusion.
4 is formed on crystalline silicon. As an insulating film that acts as a barrier against hydrogen diffusion, a silicon nitride film formed by a low pressure CVD method, a silicon nitride film or a silicon nitride oxide film formed by a plasma CVD method can be used.

Next, hydrogen is introduced into the crystalline silicon thin film by conventional ion implantation.

Next, heat treatment is performed in an atmosphere of N2, A', H2, or a mixed gas thereof.

During this heat treatment, hydrogen introduced by ion implantation diffuses into the crystalline silicon thin film, causing the interface states existing at the underlying interface, the defect levels in the crystalline silicon thin film, and the crystalline silicon It is trapped by the interface states existing at the grain boundaries of the substrate, suppresses the generation of back channels at the underlying interface, reduces the potential of the grain boundaries, and increases the mobility.

In addition, by forming a silicon nitride film between the substrate and the crystalline silicon thin film, Na''' from the substrate such as glass can be removed.
It has a blocking effect against alkali ions such as, improving reliability.

In addition, by forming an insulating film that acts as a barrier against hydrogen diffusion on both sides of the crystalline silicon thin film, it is possible to prevent out-diffusion from the surface of the crystalline silicon thin film when hydrogen diffuses through heat treatment. The passivation effect can be enhanced.

[Example code] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 2 is a cross-sectional view of a MOSFET made using the present invention.

[First Example] SiH4 was deposited on the glass substrate 21 by plasma CVD as a first insulating film to act as a barrier against hydrogen diffusion.
The silicon nitride film 22 is exposed to IO using a 7MHI mixed gas system.
OOA deposited. The deposition conditions were as follows: a parallel plate plasma CVO device was used, SiH4 (100 H2 dilution) flow rate was 15 sccm, NH3 flow rate was 10 seconds, and pressure was 0.1.
Deposition was performed for 35 minutes under the conditions of 6 Torr, discharge power of 3.5 W, and substrate temperature of 300°C. As a result of IR (infrared spectroscopy) analysis, it was found that the silicon nitride film deposited under these conditions contained about 10 atm % F of hydrogen.

Next, by RF Blaze 7 CVD method, Si}l21
A thin polycrystalline silicon film @23 was deposited in an IQOOA manner on the silicon nitride film 22 using a mixed gas system of 12/HCj2/Hz. The deposition conditions were Si}I. C fL 20.
! l sccm, HCf! ．． 130sccm, H
2 200 sccm, pressure 2. O Torr, R
The test was conducted at Fpower 60W and substrate temperature 230°C.

Under these conditions, the grain size on the silicon nitride film 22 is approximately 1
．． A 0 μm polycrystalline silicon thin film was deposited.

Next, using the sputtering method, the gate insulating film was made of Sin2.
After depositing the film 24 to a thickness of 50 OA, the gate electrode 25 was formed.

Next, P1 was implanted by ion implantation to form a source train region 26.

Next, as a second insulating film that acts as a barrier against hydrogen diffusion, a plasma carbon
A silicon nitride film 27 was deposited at a thickness of 5000 Å using the VD method.

Next, heat treatment was performed at 550° C. in a N2 atmosphere.

Next, a contact hole is opened in a desired region, and the AfL electrode 2
8 was formed.

In this example, a comparison of the electrical characteristics of a MOSFET formed on a glass substrate with a polycrystalline silicon thin film formed directly on the glass substrate and a MOSFET created according to this example revealed that the electron mobility was more than twice as high and the threshold voltage The fluctuation range of is 1
/2 or less.

This means that hydrogen diffuses from the silicon nitride film 22 into the polycrystalline silicon thin film 23 due to the heat treatment, is trapped in the interface states existing at the base interface and the grain boundaries in the polycrystalline silicon thin film 23, and is This is thought to be because the number decreased, the generation of back channels at the base interface was suppressed, and the potential barrier at the grain boundary was lowered. This can be seen from the results of ESR ('H-son spin co@) measurements.
The density of dangling bonds in a polycrystalline silicon thin film is
This is clear from the fact that the heat treatment caused a decrease of more than one digit.

In addition, silicon nitride, which acts as a barrier against hydrogen diffusion,
Regarding the effects of 22 and 27, for example, depending on the presence or absence of the silicon nitride film 27, the density of hydrogen present in the polycrystalline silicon film 23 is reduced from the order of IE20 cm-' to the order of lE19 cm"" or less. This indicates that this film acts as a barrier against hydrogen out-diffusion.

In addition, in reliability tests, there was almost no change in electrical characteristics even in high-temperature tests, and the reliability was sufficient.

This is considered to be because the silicon nitride film 22 blocks the diffusion of alkali ions from the glass substrate.

Furthermore, measurements of electrical characteristics have revealed that heat treatment at 550° C. allows hydrogen to diffuse into polycrystalline silicon and at the same time activates the source/drain regions.

[Second Example] SiH47 was deposited on the glass substrate 21 by plasma CVD method.
The silicon nitride film 22 is heated to 100% by NH3 mixed gas system.
OA was deposited. Is the deposition condition parallel plate type plasma?
Using CVD equipment, SiH4 (IOX H2 dilution)
Flow rate 15sccm% NH3 flow JiLiOsccm, pressure 0.15Torr, discharge power 3.5W, substrate temperature 30
Deposition was carried out for 35 minutes at 0°C. As a result of IR (infrared spectroscopy) analysis, it was found that the silicon nitride film deposited under these conditions contained about 10 ata+t of hydrogen.

Next, an IOOQA non-quality silicon thin film 23 was deposited on the silicon nitride film 22 using a SiH4/H2 mixed gas system by plasma CVD. The deposition conditions are S
in4 flow rate 2sec 2}1zl8sec, pressure 0
．． Deposition was carried out for 30 minutes at l2 Torr and discharge power of 5 W.

Next, by sputtering, Si0 is used as the gate isolation Jlj.
After depositing the second film 24 to a thickness of 50 OA, a gate electrode 8i25 was formed.

Next, P0 was implanted by ion implantation to form source/drain regions 26.

Next, as a second insulating film serving as a barrier against hydrogen diffusion, a silicon nitride film 27 with a thickness of 5000 Å was deposited by plasma CVD.

Next, heat treatment was performed at 600° C. in a N2 atmosphere.

Next, contacts were opened in desired regions to form Aj2 electrodes 28.

In this example, it was confirmed by cross-sectional TEM (transmission-A electron microscopy) that the amorphous silicon thin film 23 underwent solid phase crystal growth and became polycrystalline due to the heat treatment at 600°C.

In this example, a comparison of the electrical characteristics of a MOSFET formed on a glass substrate with a polycrystalline silicon thin film formed directly on the glass substrate and a MOSFET created according to this example revealed that the electron mobility was 15 times higher and the dark value voltage was 15 times higher. The fluctuation range of is 17
reduced to less than 2.

In addition, we also developed a MOSFET in which an amorphous silicon thin film was directly formed on a glass substrate, and a MOSFET made using this example.
Comparison of electrical property measurements with T shows that the electron mobility is 10
It has increased more than 00 times.

This means that due to the heat treatment, hydrogen diffuses from the silicon nitride film 22 into the polycrystalline silicon thin film 23, and the interface level C existing at the base interface and the grain boundaries in the polycrystalline silicon thin film 23 is traversed, and the level This is thought to be because the number decreased, the generation of back channels at the base interface was suppressed, and the potential barrier at the grain boundary was lowered. This is also clear from the results of ESR (electron spin resonance) measurements, where the density of dangling bonds in the polycrystalline silicon thin film was reduced by more than one digit due to the heat treatment.

Regarding the effect of the silicon nitride films 22 and 27 that act as a barrier against hydrogen diffusion, for example, depending on the presence or absence of the silicon nitride film 27, the density of hydrogen existing in the polycrystalline silicon film 23 can be reduced by IE20cm-' It was found that this film acts as a barrier against the out-diffusion of hydrogen.

In addition, in reliability tests, there was almost no change in electrical characteristics even in high-temperature tests, and the reliability was sufficient.

This is considered to be because the silicon nitride film 22 blocks the diffusion of alkali ions from the glass substrate.

In addition, in this example, hydrogen is diffused into polycrystalline silicon by heating at 600°C, and at the same time, the source
Measurements of electrical properties revealed that activation of the drain region is also possible.

[Third Example] SiH4/
The silicon nitride film 22 is heated to 100% by NH3 mixed gas system.
OA was deposited. As for the deposition conditions, a parallel plate plasma CVD apparatus was used, Si84 (1 volume) diluted with 12, flow rate 1
5s ccm, NH3 flow rate 10sccm,
Deposition was performed for 35 minutes under the conditions of a pressure of 0.16 Torr, a discharge power of 3.5 W, and a substrate temperature of 300°C. As a result of IR (infrared spectroscopy) analysis, it was found that the silicon nitride film deposited under these conditions contained about 10 yen of hydrogen.

Next, by RF plasma CVD method, SiH2C fL
A polycrystalline silicon thin film 23 was deposited to a thickness of 1000^ on the silicon nitride film 22 using a/t[J2/Hz mixed gas system. The deposition conditions are: SiH2Cu, 0.9
secm, HCI+30sccm, H2200
sccm, pressure 2. O Torr, RF power6
0W1 The temperature of the substrate was 230°C. Under these conditions, a polycrystalline silicon thin film with a grain size of about 1.0 μm was deposited on the silicon nitride film 22.

? First, as a gate electrode insulating film, a SiO2 film of 200A was deposited by a sputtering method, and then a silicon nitride film of 300AiI was deposited by a plasma CVD method as an insulating film to serve as a barrier against hydrogen diffusion. 25
was formed. The reason why the Si02 film was deposited first was to prevent the deterioration of the electrical characteristics of the MOSFET because, as is well known, if the gate insulating film is made of only a silicon nitride film, the electrical characteristics of the MOSFET will deteriorate due to polarization in the middle. It is.

Next, P'' was implanted by ion implantation to form source/drain regions 21t.

Next, heat treatment was performed at 550° C. in a N2 atmosphere.

Next, as a protective film, plasma CVD? At the same time, a silicon nitride film of 5000A was deposited.

Next, a contact hole is drilled in the desired area, and the AJ2 electric F
J2B was formed.

In this example, even if the thickness of the silicon nitride film is 300A as an insulating film that has burrs 7 against hydrogen diffusion, the density of hydrogen in the polycrystalline silicon thin film is the same as when the silicon nitride film thickness is 5000A. There was no change at all.

Further, even when the Sin2 film 5000A was used as the barrier film, there was no change in the hydrogen density, indicating that the silicon nitride film 3008 also sufficiently acted as a barrier.

In addition, a two-layer structure of a silicon nitride film and a silicon oxide film was used as the gate insulating film;
Compared to the case where a membrane was used, almost no change in electrical properties was observed.

In addition, in this example, plasma CVO was used as the barrier film.
Although a silicon nitride film prepared by the method No. 7 was used, a similar effect could be obtained by using a silicon nitride film deposited by low-pressure CVD.

[Fourth Example] SjHa/
The silicon nitride film 22 is heated to 100% by NHsm mixture gas system.
OA was deposited. As for the deposition conditions, a parallel plate plasma CVD device was used, and SiH4 (to!k }12 dilution) was used.
Flow i155CCIll% NTo? 1jt i 10
sccm, pressure 0.16 Torr, discharge power 3.5
Deposition was performed for 35 minutes under the conditions of W and a substrate temperature of 300°C. In the silicon nitride film deposited under these conditions, IR (
As a result of analysis (infrared spectroscopy), it was found that approximately 1O'36 of hydrogen was contained.

Next, by RF plasma CVD method, SiH, CIL2
/HCfL/H2 mixed gas system, silicon nitride film 22
A polycrystalline silicon thin film 23 was IOOOA deposited thereon.

The deposition conditions were SiH. Cfl 2Q. 9scc
m, l{Cj2 130SCCIIl1H2200
SCCm1 pressure2. O Torr, RF power
The test was conducted at a temperature of 60W and a substrate temperature of 230°C. Under this condition,
On the silicon nitride film 22, grains with a diameter of about 1. Ol. A polycrystalline silicon thin film of tm was deposited.

Next, as the gate insulating film 24, a silicon nitride oxide film 500A was deposited by plasma CVD as an insulating film to serve as a barrier against hydrogen diffusion, and then the gate electrode 25 was formed. As is well known, a silicon nitride oxide film can have the properties of both a silicon nitride film and a silicon oxide film by appropriately selecting the composition ratio of nitrogen and oxygen in the film. Here, S.I.
By optimizing the deposition conditions using a mixed gas system of OH4/NH3/N20, the composition ratio of the film was made such that the atomic ratio of N to St was 3 and the atomic ratio of 0 to 2.

Next, P+ was implanted by ion implantation to form source/drain regions 26.

Next, heat treatment was performed at 600° C. in a N2 atmosphere.

Next, a silicon nitride film of 5QOOA was deposited as a protective film by plasma CVD.

Next, a contact hole is opened in a desired area, and the AA electrode 2
8 was formed.

In this example, even if a silicon nitride oxide film is used as the second insulating film that acts as a barrier against hydrogen diffusion, the density of hydrogen in the polycrystalline silicon thin film is completely the same as when a silicon nitride film is used. There was no change.

Furthermore, although a silicon nitride oxide film was used as the gate insulating film, almost no deterioration of the electrical characteristics was observed compared to the case where a Si02 film was used. On the substrate 21, SiH4/
The silicon nitride film 22 is heated to 100% by NH mixed gas system.
OA was deposited. The deposition conditions were parallel plate type Blaz 7.
Using a CVD device, SiH4 (10 x 12 dilution) flow rate was 15 sccm, NH. Flow rate 10 sccm, pressure 0.
16 tons orr, discharge power 3.5W, substrate temperature 400℃
Deposition was carried out for 20 minutes under these conditions.

Next, by RF plasma CVD method, SiH2C Il
A thin polycrystalline silicon layer [23] was deposited on the silicon nitride film 22 using an I/H2 mixed gas system.

The deposition conditions are: SiH2Cj2, 0.9sc
cm, HCl130sccm, H. 200
sccm, pressure 2.0 Torr. RFpower6
0W1 The temperature of the substrate was 230°C. Under these conditions, nitrogen
A polycrystalline silicon thin film having a grain size of approximately 1.0 μm was deposited on the hissilicon film 22.

Next, using a sputtering method, SiO2 was used as a gate insulating film.
After depositing the film 24 to a thickness of 50 OA, the gate electrode 25 was formed. Next, hydrogen plasma was irradiated using a parallel plate plasma device. Hydrogen plasma conditions include a pressure of 0.16T.
orr, a discharge output of 600 W, a substrate temperature of 300° C., and an irradiation time of 30 tnin.

Next, P was implanted by ion implantation to form source/drain regions 26.

Next, as a second insulating film serving as a barrier against hydrogen diffusion, a silicon nitride film 27 having a thickness of 5000 Å was deposited using the same method as the first insulating film 22 by plasma CVD.

Next, heat treatment was performed at 550° C. in a N2 atmosphere.

Next, a contact hole is opened in a desired area, and the Afl electrode 2
8 was formed.

In this example, a comparison of the electrical characteristics of a MOSFET fabricated on a glass substrate with a polycrystalline silicon thin film formed directly on the substrate and a MOSFET fabricated according to this example revealed that the electron mobility was more than twice that of the threshold value. The voltage fluctuation range is 1
/2 or less.

This means that due to the heat treatment, hydrogen from the hydrogen plasma diffuses into the polycrystalline silicon thin film 23, is trapped in the interface states existing at the base interface and the grain boundaries in the polycrystalline silicon thin film 23, and the level This is thought to be because the number decreased, the generation of back channels at the base interface was suppressed, and the potential barrier at the grain boundaries was lowered. This is also clear from the results of EsR (i-son spin resonance) measurements, where the density of dangling bonds in the polycrystalline silicon thin film was reduced by more than one digit due to the heat treatment.

Regarding the effect of the silicon nitride films 22 and 27 that act as a barrier against hydrogen diffusion, for example, depending on the presence or absence of the silicon nitride film 27, the density of hydrogen existing in the polycrystalline silicon film 23 is It was found that this film acts as a barrier against out-diffusion of hydrogen because it decreased from the order of 1El9cl' to below the order of 1El9cl'.

In addition, in reliability tests, there was almost no change in electrical characteristics even in high-temperature (high-temperature) tests, and the reliability was sufficient.

This is considered to be because the silicon nitride film 22 is blocking against the diffusion of alkali ions from the glass substrate.

[Sixth Example] SiH4/
N.H. By using a mixed gas system, the silicon nitride film 22 is
OA was deposited. As for the deposition conditions, parallel plate type Blaz v
Using a cvo device, SiH4 (10% i82 dilution)
Flow rate l5s c cm, NH3 flow rate 10sc
cm. Deposition was performed for 20 minutes under the conditions of a pressure of 0.16 Torr, a discharge power of 3.5 W, and a substrate temperature of 400°C.

Next, by RF plasma [:VD method, SiH2C j
A polycrystalline silicon thin film 23 was deposited on silicon nitride@22 using a mixed gas system of 2 2 /HCJZ/th.

The deposition conditions were: SiH2C IL 20.9scc
m, HCj2130sccm. H2200s
ccm, pressure 2.0 orr, RFpo*er60W
, and the substrate temperature was 230°C. Under these conditions, a polycrystalline silicon thin film with a grain size of about 1.0 μm was deposited on the silicon nitride film 22.

Next, the gate insulating film was made of Si02 by the sputtering method.
After depositing the film 500^, the gate electrode 25 was formed.

Next, by ion implantation, hydrogen was added to IEl6Cl'',
Polycrystalline silicon thin film 23 under the condition of acceleration voltage 20 keV
Injected all over.

Next, P0 was implanted using an ion implantation method to form source/drain regions 26.

Next, as a second insulating film that acts as a barrier against hydrogen diffusion, a plasma carbon
5000 silicon nitride films 27 were deposited by VD method.

Next, heat treatment was performed at 550° C. in a N2 atmosphere.

Next, a contact hole is opened in the desired area, and the AJl electrode i2
8 was formed.

In this example, a comparison of the electrical characteristics of a MOSFET formed on a glass substrate with a polycrystalline silicon thin film formed directly on the glass substrate and a MOSFET prepared according to this example revealed that the electron mobility was more than twice as high as the threshold value. The voltage fluctuation range is l
/2 or less.

This means that hydrogen from the hydrogen plasma diffuses into the polycrystalline silicon thin film 23 and is trapped in the interface states existing at the base interface and the grain boundaries in the polycrystalline silicon thin film 23, according to the *jI'A principle. This is thought to be because the number of levels decreased, the generation of back channels at the base interface was suppressed, and the potential barrier at the grain boundaries was lowered. This is also clear from the results of ESR (electron spin co-Oi) measurements, where the density of dangling bonds in the polycrystalline silicon thin film was reduced by more than one order of magnitude due to the heat treatment.

In addition, silicon nitride I, which acts as a barrier to hydrogen diffusion,
As for the effects of lN22 and 27, for example, due to the presence or absence of this silicon nitride film 27, the density of hydrogen existing in the polycrystalline silicon film 23 decreases from the order of IE20c+n-' to below the order of IE19cm-', resulting in Therefore, the Kono membrane is an out-diffusio of hydrogen.
It was found that it acts as a barrier against n.

In addition, in reliability tests, there was almost no change in electrical characteristics even in high-dry/high-temperature tests, and the reliability was sufficient.

This is considered to be because the silicon nitride film 22 blocks the diffusion of alkali ions from the glass substrate.

As described above, in this example, the crystalline semiconductor thin film is
Formed using the plasma CVD method proposed by the applicant.
Although this effect was demonstrated for polycrystalline silicon with a small grain size and polycrystalline silicon formed by heat treatment of amorphous silicon formed by plasma CVD, it is not possible to apply this effect to other crystalline semiconductor thin films, such as those formed by low pressure CVD. Polycrystalline silicon obtained by implanting Si0 into polycrystalline silicon, amorphous silicon made amorphous by annealing and recrystallization, and Showa 6
Large-grain polycrystalline silicon as proposed in No. 2-73630, single crystal silicon formed on an amorphous substrate as proposed by the present applicant in JP-A-63-107016, etc. Needless to say, the same effect was obtained when using the same method.

[Effect of the invention] An insulating film that acts as a barrier against hydrogen diffusion is formed between the silicon thin film and the substrate and in the silicon thin film, and further,
By heat treatment, it is possible to reduce the interface states at the interface with the silicon thin film base, suppress the back channel effect, and improve the electrical characteristics of TPT, such as reducing the fluctuation width of the threshold voltage and improving carrier mobility. was completed.

Also, as an insulating film that acts as a barrier against hydrogen diffusion,
By using a silicon nitride film, Na” from the substrate can be removed.
It was possible to block the intrusion of alkali ions such as, and improve the reliability of TPT.

As a result, it has become possible to easily form TPT with excellent electrical characteristics and reliability on an inexpensive glass substrate.

[Brief explanation of drawings]

FIG. 1 is a sectional view for explaining the features of the present invention. FIG. 2 is a cross-sectional view of a MOSFET formed using the present invention. FIG. 3 is a sectional view for explaining the problems of the prior art. l1, 2l, 3l... Substrate 12, 22, 32... First insulating film serving as a barrier against hydrogen diffusion l3, 23, 33... Semiconductor thin film 14, 24, 34... Hydrogen a second insulating film that acts as a barrier to diffusion of

Claims (8)

[Claims] (1) In a method for manufacturing a semiconductor device in which a crystalline semiconductor thin film is formed on an insulating substrate, a first layer, which serves as a barrier against hydrogen diffusion, is provided on both upper and lower sides of the crystalline semiconductor thin film.
A method for manufacturing a semiconductor device, comprising the steps of respectively forming second insulating films, introducing hydrogen into the semiconductor thin film, and then performing heat treatment. (2) A silicon nitride film formed by a low pressure CVD method or a plasma CVD method is used as the insulating film that acts as a barrier against hydrogen diffusion. A method for manufacturing a semiconductor device. (3) A method for manufacturing a semiconductor device according to claim 1, characterized in that a silicon nitride oxide film formed by a plasma CVD method is used as the insulating film that acts as a barrier against hydrogen diffusion. . (4) The method for manufacturing a semiconductor device according to claim 1, wherein the crystalline semiconductor thin film material is silicon. (5) The method for manufacturing a semiconductor device according to claim 1, wherein the hydrogen is introduced by diffusion of hydrogen from the insulating film containing hydrogen. (6) The method for manufacturing a semiconductor device according to claim 1, wherein the hydrogen is introduced by using plasma containing hydrogen. (7) The method for manufacturing a semiconductor device according to claim 1, wherein the hydrogen is introduced by ion implantation. (8) The temperature of the heat treatment is a temperature at which amorphous silicon becomes polycrystalline.
5. A method for manufacturing a semiconductor device according to item 4, item 5, or item 5.