JPS62204575A - Thin film semiconductor device and manufacture thereof - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a thin film semiconductor device and a method for manufacturing the same.

BACKGROUND OF THE INVENTION Hydrogenation of a 7a film semiconductor layer using a silicon nitride film in a conventional thin film semiconductor device and its protection are described in IEEE, EDL-5: IEEE.

EDL-5, No. 11 ('84) P 468. Figure 4 shows a typical example of MOS F E
This will be explained by showing a cross-sectional configuration diagram of T. A thin film semiconductor layer 32 in which the source and drain are implanted into n-type is laminated on the insulator smell plate 31, three layers of PSG film 3 are deposited on the thin film semiconductor layer 32, and three layers are further deposited on the PSG film 33. A silicon nitride film 34 is laminated. When manufacturing it,
First, a thin film semiconductor layer 32 is laminated on a substrate 31 and patterned, and then a gate insulating film 35 is formed by thermal oxidation.
Furthermore, a thin film semiconductor layer 36 as a gate electrode is laminated thereon. After that, pattern out the gate part and PS
(JI33 is laminated at 6000A, contact holes are made, aluminum 37 is laminated, aluminum wiring is patterned, and heat treated at 450°C. After that, a silicon nitride film 34 containing a large amount of hydrogen is coated with Si, H4, NH3 ,N2 by plasma CVD at an acoustic intensity of 300°C, and then heat-treated in N2 at 450°C to thermally diffuse hydrogen in the silicon nitride 11i!34 into the film semiconductor layer. hydrogenation.

Problems to be Solved by the Invention However, hydrogenation of the sg semiconductor layer and its protection are difficult due to the mobility,
It is related to y th, on-off characteristics, etc. Hydrogenation improves their properties, but deterioration occurs due to the release of hydrogen from the thin film semiconductor layer.

In the silicon nitride film 34 having a conventional structure, hydrogenation is performed at 450° C.N after forming the silicon nitride film 34 containing a large amount of hydrogen.
It takes place in Z. During hydrogenation, silicon nitride WA3
The hydrogen in 4 is thermally diffused or released to the thin film semiconductor layer 32 and the outside, and disappears. Therefore, in the conventional configuration, only the silicon nitride Wi 34 from which the three elements on the PSG film 3 are removed is on the thin film semiconductor layer 32. The silicon nitride film 34 from which hydrogen has been removed is likely to have weak bonding inside, causing film cracks, and even as a protective film, it becomes weak due to the release of hydrogen and is easily immersed in water, etc., and is a thin film semiconductor. Since the ability to retain the release of hydrogen from the layer 32 is also weakened, there is a problem that the stability of the characteristics of the thin film semiconductor device is deteriorated. Furthermore, when a conventional thin film semiconductor device is used in a place where wear is likely to occur, such as in a contact image sensor, there is a problem that the silicon nitride film 34 in which hydrogen has been released becomes weak in mechanical strength such as wear resistance. there were. Furthermore, in conventional configurations, when hydrogenation is performed by heat treatment, hydrogen diffusion is insufficient if the heat treatment temperature is lower than 430°C, and conversely, if it is higher than 470°C, a large amount of hydrogen is released. A sufficient effect could not be expected unless it was within a narrow temperature range of 470″C.As a result of the above,
Thin film semiconductor devices with stable characteristics have not yet been put into practical use.

Therefore, an object of the present invention is to solve such problems.

Means for Solving the Problems In order to solve the above-mentioned problems, the device of the present invention uses a first silicon nitride film containing more than 5% hydrogen as an insulating film constituting a semiconductor device, and a first silicon nitride film containing more than 5% hydrogen. It is formed by an insulating film containing 5% or less hydrogen and laminated on the film.

Further, the first method of the present invention is to form a first silicon nitride film by high-frequency excited CVD using a mixed gas of a gaseous silicon compound and a gas containing at least nitrogen atoms, when forming an insulating film constituting a semiconductor device. A film is formed, an insulating film containing 5% or less hydrogen is laminated on top of the first silicon nitride film, and then heat treated at a temperature of 350° C. or more and 550° C. or less.

Further, in the second method of the present invention, when forming an insulating film constituting a semiconductor device, the first silicon nitride is formed by high-frequency excited CVD using a mixed gas of a gaseous silicon compound and a gas containing at least nitrogen atoms. A film is formed, and an insulating film is laminated on the first silicon nitride film at a substrate temperature of 350° C. or more and 500° C. or less.

action The effects of the present invention are as follows.

That is, by covering the first silicon nitride film containing a large amount of hydrogen, which serves as a hydrogen diffusion source, with an insulating film containing a small amount of hydrogen, hydrogen can be extracted from the silicon nitride film containing a large amount of hydrogen by hydrogenation. Even after the hydrogen is released and diffused into the thin film semiconductor layer, it protects the surface of the first silicon nitride film from which hydrogen has been released, supplements the mechanical strength of the first silicon nitride film, and prevents hydrogen from flowing out from the thin film semiconductor layer. Emissions are suppressed to improve the stability of characteristics and mechanical strength of thin film semiconductor devices.

Furthermore, since hydrogen is suppressed from being released to the outside during the heat treatment for hydrogenation, conditions such as the temperature for the heat treatment for hydrogenation can be widened, making production easier.

Example Examples of the present invention will be described below.

FIG. 1 shows an N-channel board HM of the first embodiment of the present invention.
FIG. 2 is a cross-sectional configuration diagram of an O8FET. A polycrystalline Si film is laminated as a thin film semiconductor layer 2 on a quartz substrate 1 . The source and drain portions of the polycrystalline Si thin film semiconductor layer 2 are made N-type by implanting As, and the channel portion is not diffused.

A gate insulating film 3 is provided on the channel portion, and a polycrystalline Si film 4 serving as a gate electrode is laminated thereon. The thin film semiconductor layer 2 is covered with a thermal oxide film 5. A contact hole is formed in the thermal oxide film 5 for contacting the aluminum electrode 6 and the thin film semiconductor layer. Furthermore, a first silicon nitride curtain 7 containing a large amount of hydrogen, which serves as an interlayer insulating film and a protective film and serves as a hydrogen diffusion source, is laminated on top of these. A second silicon nitride film 8 is laminated thereon.

Next, the manufacturing method will be described. A thin film semiconductor layer 2 of polycrystalline or amorphous Si is formed on a quartz substrate 1 with a thickness of 11 by low pressure CVD at Si H4/He = 0.2, degree of vacuum 0.5 Torr, and temperature 550°C to 650°C. 300 people to 1
μm stacked and etched into an island-like pattern (the S
i's? 79 Even if the non-semiconductor layer 2 is amorphous by X-rays immediately after lamination, it becomes a polycrystalline Si film after heat treatment.)
. Next, the gate insulating film 3 is thermally oxidized with water vapor for 500 to 20 minutes.
A polycrystalline Si film 4 of the gate electrode is formed on the polycrystalline Si film 4 of the gate electrode.
are laminated by low-pressure CVD, and the gate portion is patterned by etching.

Then, the source and drain parts AS are 3×1 at 120kV.
0"/cir implantation, and heat treatment for 5 to 20 minutes at 950°C in N2 to activate. (When performing ion implantation, there is no oxidation Next, a thermal oxide film 5 of 500 to 2000 layers is formed on the entire surface by steam oxidation, a contact hole is formed in this thermal oxide film 5, and an aluminum electrode 6 is laminated. The silicon nitride film 7 containing a large amount of hydrogen, which serves as a diffusion source, is made of SiH4.

NH:! , H2, and the temperature of the substrate 1 is kept from the lowest temperature to 350 DEG C. or less, and the layers are stacked to a thickness of 5008 to 2 .mu.m by plasma CVD. On top of that, silicon nitride V8, which does not contain much hydrogen, is applied to the substrate at a temperature of 350°C or higher and 550°C using a mixed gas of SiH4°N2 and H2.
℃ or less, 200 to 2 μm layers are laminated. Thereafter, contact holes corresponding to the pads of the aluminum electrodes 6 are made in the silicon nitride films 7 and 8.

Among the prototype N-channel thin film MO8FETs, one with channel tw = iooμm and one channel length = 10μm, the relationship between its mobility and the hydrogenation heat treatment temperature is shown in Figure 2 compared with the conventional one. .

It can be seen that the decrease in mobility is smaller in this example even when the heat treatment temperature is higher, and the characteristics are improved overall.

Moreover, the results of the stability test also showed that the present example was more stable and more resistant to the environment than the conventional one.

Furthermore, in this embodiment, by using the same silicon nitride film 8 as the silicon nitride film 7 that is a hydrogen diffusion source as an insulating film that does not contain much hydrogen, the same silicon nitride film 7
, 8 are laminated, it is possible to eliminate cracks that occur in the silicon nitride film 7 due to differences in thermal expansion coefficients.

Furthermore, the surface is made of silicon nitride WA8 which does not contain much hydrogen.
Since the silicon nitride film 8 is covered with hydrogen, there is no deterioration of the silicon nitride film 8 itself due to the release of hydrogen, and the release of hydrogen from the thin film semiconductor @2 is suppressed. Furthermore, since the silicon nitride film 8 has particularly good water resistance, the stability and water resistance of the thin film semiconductor device of this example were improved. In addition, silicon nitride de-8 can be laminated using the same plasma CVD method as the silicon nitride bladder 7, which is a hydrogen diffusion source, by changing only the gas and substrate 1 temperatures, so the manufacturing process can be shortened, especially when using plasma in two or more chambers. (It is convenient to have a CVD device), the silicon nitride film 7, which is a hydrogen diffusion source, is hydrogenated without being exposed to the surrounding air, and a silicon nitride de-8 film, which is a protective film with good properties, is layered on top of it. did it.

Furthermore, since hydrogenation can be performed simultaneously with the stacking of silicon nitride 1198, there is no need for subsequent heat treatment. Further, at this time, the aluminum electrode 6 and the contact portion of the T'l film semi-film conductor layer 2 are heat-treated at the same time (there is no particular problem if only the contact portion of the aluminum electrode is heat-treated first). Moreover, there is no problem even if the aluminum electrode 6 is formed after the nitride film 8 is laminated. Further, the silicon nitride film 8 is made of silicon nitride WA7.
Since there is no need to supply a large amount of hydrogen to the thin film semiconductor layer as shown in FIG. A ratio of about 1:3 is still effective from the viewpoint of mechanical strength. In addition, in this example, higher than 350℃<550℃
Silicon nitride W is an insulating film with low hydrogen content at high temperatures below ℃:! 8 was laminated, it was found to be effective because it had good crystallinity and a dense protective film was formed.

In order to form a highly crystalline insulating film with low hydrogen content at such high temperatures, other materials such as BN, Ti, etc.
Nitride films such as N, Si C, Ag2O3, Ta 2
An oxide film such as 05 is also effective. The way they are formed is
Money f! ! Films (B, Ti, A!2.Ta, etc.) may be laminated first and then nitrided or oxidized, sputtering, plasma CV
D. There are many methods such as cluster ion beam, CVD, vapor deposition, and plasma spraying.

Silicon nitride v7 which is a hydrogen diffusion source as in this example
By forming the thermal oxide film 5 before forming the 1119 semiconductor layer, there is no plasma damage to the 1119 semiconductor layer, so a thin film semiconductor device with good characteristics can be obtained.

Furthermore, since the oxide film is a thermal oxide film, it has better density than PSG, prevents release of hydrogen from the thin film semiconductor layer, and provides a thin film semiconductor device with good stability of characteristics. In addition, these thermal oxide films 5 and nitride F! By stacking 7.8, the difference in thermal expansion coefficient is large when the thin film semiconductor layer 2 below is a Si thin film, and cracks are likely to occur in this Siiff film when only a nitride film is used. 5 and nitride film 7.
Since the thermal expansion coefficient of the Si thin film is around the middle of 8,
Thermal oxide film 5 alleviates the difference in thermal expansion coefficients and prevents cracks from occurring.

In addition, the hydrogen concentration in the silicon nitride film 7 containing a large amount of hydrogen, which is a hydrogen diffusion source, is still more than 5% even after the hydrogenation heat treatment, and on the contrary, the hydrogen concentration in the silicon nitride film 8, which does not contain a large amount of hydrogen, is more than 5% even after the hydrogenation heat treatment. It was found by SIMs, infrared absorption, etc. measurements that it was 5% or less. In addition, silicon nitride film 8 that does not contain much hydrogen
If the amount of hydrogen is more than 5%, the release of hydrogen from the silicon nitride film itself, which is laminated as a protective film, becomes significant and the film begins to deteriorate, which is not good. If the silicon nitride film 7, which is a hydrogen diffusion source, is removed in such a way that more than 5% of hydrogen remains even after hydrogenation, the effect of hydrogenation will be weak.

A second embodiment of the present invention is shown in FIG. 3 and will be described. 1st
Same as the example of
The difference from the first embodiment is that a thermal oxide film is not formed after ion implantation. That is, the first silicon nitride film 22 containing a large amount of hydrogen is directly stacked on the thin film semiconductor layer 21, and then plasma sprayed onto the first silicon nitride film 22 to form an insulating film 23 that does not contain a large amount of hydrogen on the BN'i substrate 24. Lamination was carried out at a temperature ranging from room temperature to 350°C. And then inert gas or H2, or their mixture if soot at 350℃
Hydrogenation was performed by heat treatment at temperatures above and below 550°C.

Then, since there is no oxide film between the thin film semiconductor layer 21 and the silicon nitride film 22, which is the hydrogen diffusion source, 7! Membrane semiconductor layer 2
Hydrogenation of 1 could be done quickly and at a relatively low temperature. Additionally, the manufacturing process has been shortened. Also, BN.

Nitride films such as TiN, MoN, SiC, and i-C have strong wear resistance, so they can be used as silicon nitride patterns 22 for thin film semiconductor devices that require wear resistance, such as contact image sensors and IC cards. The insulating film 23, which is most suitable for covering on top, can also be formed using a silicon nitride film formed by ECR. The silicon nitride film produced by ECR has a low hydrogen content, is dense and hard, and has strong chemical resistance.
Effective as a protective film.

In the above embodiment, the thin film semiconductor layers 2 and 21 are formed by LPCVD.
We have explained the hydrogenation of polycrystalline Si films using electron beams, lasers, lamp heat radiation, etc. It is also effective for Silly. In other words, it has the effect of terminating defects at grain boundaries that exist in polycrystalline Si films and recrystallized $1 films and dangling bonds that exist inside the bulk. Furthermore, since it has the effect of reducing defects and dangling bonds at the interface between the Si film and the gate insulating film, single-crystal SiRC! It is also effective for Furthermore, in the above embodiments, only the insulation film or interlayer insulation film of the MOSFET was described as the insulation film constituting the thin film semiconductor device.
It goes without saying that the present invention is also effective for gate insulating films. It goes without saying that the present invention can also be used for parts and devices whose characteristics change depending on the hydrogen content inside the material. In particular, materials such as magnetic materials whose saturation magnetic field constant and Hc change depending on hydrogen, such as sensors, magnetic semiconductors, magnetic recording materials, etc.
Effective for magnetoresistive elements, etc. Furthermore, the technical means of the present invention can be effectively applied to hydrogen storage alloys and the like.

Effects of the Invention As described above, according to the present invention, the insulating film constituting the thin film semiconductor device is composed of a silicon nitride film containing a large amount of hydrogen, which serves as a hydrogen diffusion source, and a hydrogen-containing silicon nitride film laminated thereon. By constructing an insulator film with a low content, hydrogen can be effectively and easily diffused into the 1110 semiconductor layer, and the 7aWA
As a protection for the semiconductor layer, it can be made without cracks, has strong water resistance, and has strong mechanical strength, which can contribute to improving the characteristics and stability of thin film semiconductor devices. Moreover, its manufacture is also easy.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of an N-channel MO8FET according to the first embodiment of the present invention, and FIG.
FIG. 3 is a cross-sectional view of the N-channel thin film MOSFET of the second embodiment of the present invention, and FIG. 1 is a cross-sectional view of a channel thin film MO8FET. DESCRIPTION OF SYMBOLS 1... Quartz substrate, 7, 22... First silicon nitride film, 8... Second silicon nitride film (insulator film), 23
...Insulator film, 24...Substrate agent Yoshihiro Morimoto Figure 1/-Ichisoku Yoshimoto 7-11 Tom1's Nitrogen 7-layer 3-g7's Nitrogen Fig. 2 Heat treatment humidity ('(1) Fig. 3

Claims (1)

[Claims] 1. An insulating film constituting a semiconductor device includes a first silicon nitride film containing more than 5% hydrogen and a hydrogen content of 5% or less laminated on the first silicon nitride film. A thin film semiconductor device characterized in that it is formed of an insulating film. 2. The thin film semiconductor device according to claim 1, wherein the insulating film containing 5% or less hydrogen is a second silicon nitride film. 3. The thin film semiconductor device according to claim 1 or 2, wherein an oxide film is formed under the first silicon nitride film. 4. When forming an insulating film constituting a semiconductor device, a first silicon nitride film is formed by high-frequency excitation CVD using a mixed gas of a gaseous silicon compound and a gas containing at least nitrogen atoms; 1. A method of manufacturing a thin film semiconductor device, comprising laminating an insulating film containing 5% or less hydrogen on a silicon nitride film, and then heat-treating at a temperature of 350° C. or more and 550° C. or less. 5. When forming an insulating film constituting a semiconductor device, a first silicon nitride film is formed by high-frequency excitation CVD using a mixed gas of a gaseous silicon compound and a gas containing at least nitrogen atoms; A method for manufacturing a thin film semiconductor device, characterized in that an insulating film is laminated on a silicon nitride film at a substrate temperature of 350° C. or higher and 550° C. or lower. 6. When forming the insulating film constituting the semiconductor device, the first silicon nitride is formed by high-frequency excited CVD using a mixed gas of a gaseous silicon compound and a gas containing at least nitrogen atoms, with the substrate temperature ranging from room temperature to 350°C. form a film,
Manufacturing a thin film semiconductor device according to claim 5, characterized in that a second silicon nitride film is laminated on the first silicon nitride film at a substrate temperature of 350° C. or higher and 500° C. or lower. Method. 7. When forming an insulating film constituting a semiconductor device, a first silicon nitride film is formed by high-frequency excited CVD using a mixed gas of a gaseous silicon compound and at least NH_3, and this first silicon nitride film is A second silicon nitride film formed by high frequency excitation using a gaseous silicon compound and a mixed gas containing nitrogen atoms or molecules other than NH_3 is laminated thereon. The method for manufacturing a thin film semiconductor device according to item 5. 8. The method of manufacturing a thin film semiconductor device according to claim 4 or 5, wherein the insulating film constituting the semiconductor device is formed after first forming an oxide film. 9. The thin film semiconductor device according to claim 1, wherein the thin film semiconductor layer is α-Si, polycrystalline Si, recrystallized Si, or single crystallized Si. 10. The method for manufacturing a thin film semiconductor device according to claim 4 or 5, wherein the thin film semiconductor layer is α-Si, polycrystalline Si, recrystallized Si, or single crystallized Si.