JPS59121876A - Glass substrate for thin film device - Google Patents

Abstract

PURPOSE:To prevent a thin film device from deforming at the time of forming the device by covering both side surfaces of a low melting point plate glass with insulators having ditortion point higher than those thereof. CONSTITUTION:Since mechanical stress abruptly decreases in the vicinity of the distortion point of glass 11, the glass is readily deformed by thermal stress or mechanical stress. At this time, both side surfaces are strengthened by covering the surfaces with an insulating substance 12 such as SiO2 having strong mechanical strength even in the distortion point of the glass 11 in a thickness of 0.5- 1.0mum. Thus, a thin semiconductor film, an insulating film, and annealing can be formed even at the temperature in the vicinity of the distortion point of the glass 11, and accurately masking can be performed.

Description

[Detailed description of the invention] [Technical field to which the invention pertains] The present invention relates to a glass substrate for thin film devices.

[Prior art and its problems]

In recent years, amorphous silicon and polysilicon.

Thin FIAf high speed steels for thin film transistors, bond centers, solar cells, electroluminescence devices, etc. that use CdS, CdSe, ZnS, etc. as semiconductor thin films are being researched and developed.

These devices often use low melting point plate glass such as borosilicate glass due to its advantages of low cost, thick surface, light transmittance, and the like. The fabrication of these devices requires relatively high-temperature processes such as semiconductor film formation, insulating film formation, and annealing. Usually, multiple mask patterns are used to fabricate these devices, and mask alignment is performed using the previous mask pattern. This is done by matching the pattern formed by the process. However, since the above thermal processes are often performed at temperatures close to the strain point of the glass, these processes deform the glass and shift the position of the pattern formed on the glass, making it difficult to adjust the pattern with the next mask pattern. The problem was that it became impossible.

This becomes more noticeable as the pattern becomes more precise and the diameter of the glass substrate becomes larger.

[Purpose of the invention]

It is an object of the present invention to solve the above-mentioned conventional problems and to provide a glass substrate that is less deformed during production of thin film devices.

[Summary of the invention]

In the present invention, both sides of a low melting point plate glass substrate are generally heated to 11 t by an insulating material having a high strain point at a temperature sufficiently lower than the strain point of the glass (at least 150 degrees Celsius or more lower than the strain point of the glass). . Since the mechanical stress of glass suddenly weakens near the strain point, it becomes easily deformed by thermal stress and mechanical stress, but by covering both sides with a material that has strong mechanical strength even near the strain point of glass This strengthens the substrate and prevents deformation during production of thin film devices.

The coating temperature of the insulator can be made higher if both sides are coated at the same time and stress is not applied (for example, during removal). However, in general, temperatures below the above range are preferred.

〔Effect of the invention〕

According to the present invention, semiconductor thin films, insulating films, and annealing can be performed even at temperatures near the strain point of glass, and accurate mask alignment can be performed. In addition, since the above process generally yields better results at higher temperatures, it is possible to improve device characteristics. Furthermore, as the area of the substrate becomes larger, the degree of difficulty in mask alignment due to deformation of the glass increases, so the present invention makes it possible to employ a large-area glass substrate.

[Embodiments of the invention]

Examples of the present invention are shown in FIGS. 1(a) to (C). This is an example in which an amorphous silicon thin film transistor is formed on a glass substrate.

First, Corning Co.'s No. 7059 plate glass with a diameter of 4 inches and a thickness of 0.8 tone,
Strain point: 593°C).
0212 was deposited at 1 μm on each side. The conditions are -M gas 3
mmTorr, 300 W, and 50 minutes.

Next, M is used as the gate electrodes 13a and 13b.

by DC sputtering at room temperature, Ar gas, 7 Torr
r, 300V, 0.2A, about 100OA for 10 minutes
It was deposited and patterned using photolithographic techniques.

Next, as a gate insulating film, 5i0214
f S i H, using +02 gas, 450°C, normal pressure,
Approximately 300OA was deposited in 5 minutes. Thereafter, the amorphous silicon was decomposed by glow discharge to form SiH.

Gas, I Torr, 5W, 40 minutes, substrate temperature 2
Deposited at 80°C and patterned (15a,
15b).

On top of this, Δh is added to 50OA Subatutale by the method described above,
300 OA of AA was deposited at 150° C., and both were patterned as source/drain electrodes 16.

As shown in FIGS. 2(a) to (c) corresponding to the above steps,
A normal glass substrate without the 5i02# mantle layer 12 on both sides warps into a convex shape during the gate insulating film deposition process. This is thought to be caused by the difference in expansion coefficients due to the weak mechanical strength of the glass during the process of returning it to room temperature after film formation. On the other hand, in the present invention, since the glass substrate is reinforced, warping is prevented.

FIG. 3(b) shows the gate Mo13a at a location 1.II at the edge of the wafer 6 cm apart from each other.
+13b pattern and amorphous silicon 15a.

15b is shown. 5in in Figure 3(a)
Although no misalignment occurs in the two-coat substrate, there is a large misalignment in the conventional substrate shown in FIG. 3 (0)). Figure 4 (a
1(b) shows the pattern of the thin film transistor formed. In the conventional thin film transistor shown in FIG. 4(b), the gate and channel no longer overlap due to pattern misalignment, making it impossible to operate as a transistor.

Figure 5 shows the 450℃ CVD process on the above two types of glass substrates.
This figure shows the CVD film dependence (temperature dependence) of the radius of warpage of the substrate when approximately 3000^ of 8102 is deposited by the method. The solid line is the conventional method, and the broken line is the sputter coating of 1 μm Si20 at room temperature. For those without a coating film, see Figure 2 [Yes])
If it corresponds to the process of 400,450,500 on the horizontal axis
°C is 2μ and 5μ, respectively.

This corresponds to a pattern deviation of 12μ. On the other hand, 5i02
In the case of a glass substrate with a coating film, the radius of warpage is three times larger or more, that is, the warpage is reduced.

The present invention is not limited to the above embodiments, and devices on glass substrates can be applied to contact sensors, solar cells, electroluminescence devices, etc. In general, an insulating film has a large Young's modulus and is easily deformed, so it is particularly useful when forming an insulating film on a glass substrate. Furthermore, polysilicon is also effective in cases where it is normally deposited at about 500°C. The present invention is also effective against deformation of the substrate that is likely to occur during annealing. Further, the film to be coated on both sides of the glass is not limited to 5 in 2 and may be any film having a high mechanical strength even above the strain point of the glass. For example, At20. ,
,'rho2. Bed, TiO2, Ta205.
Y2O3, Z r02, S I A N4, T
aN, BN, AtN, etc. can be used.

Further, the method for forming these films is not limited to sputtering, but may also be vapor deposition, plasma CVD, etc. which can be formed at a temperature sufficiently lower than the strain point of glass.

In addition, the thickness of the coating (covering film) is usually several hundred to 1μ thick for an insulating film used in thin film devices, and the thickness of a semiconductor thin film is several thousand amps to 1μ, so the thickness of the coating film is at least 0.5 μm. .5μ or more is required. Further, from the viewpoint of formation time, the thickness is preferably 10 μm or less. That is, the strain point of the glass formed on the coating insulating film is 250
C. or more than 150.degree. C. It is preferable to set the thickness to at least twice or more, especially at least three times the total thickness of the insulating film or semiconductor film to which a high temperature process of 150.degree.

Similarly, if the thickness of the coating film is different on both sides of the glass, uneven stress will be generated and the glass will be deformed, so it is desirable that the thickness of the coating film of the present invention be approximately equal.

Although barium borosilicate glass was used in the above embodiments, other low melting point glasses such as aluminum monosilicate glass and soda barium silicate glass may be used.

Further, the coating insulating film is preferably deposited at a temperature lower than the strain point of the glass by 150° C. or more, preferably 250° C. or more. Further, the effect of the present invention is significant when a thermal process is applied at a temperature higher than 250° C., particularly 150° C., below the strain point of glass. Also, the strain point of the coating insulating film is 200°C lower than the strain point of glass.
It is preferable to make it higher than that.

[Brief explanation of drawings]

FIGS. 1(a) to (c) are sectional views for explaining the present invention in detail, FIGS. 2(a) to (cl) are sectional views for explaining the conventional example, and FIG. 3(a)( b) and FIGS. 4(a) and 4(b) are respectively plan views for explaining the present invention in detail, and FIG. 5 is a characteristic diagram for explaining the present invention in detail. ...Low melting point glass substrate, 12...5in2 film,
13...MO gate electrode, ]4...cVDsio,
Film, 15... Amorphous silicon film, 16... Aluminum electrode for source/drain. Agent Patent attorney Kensuke Chika (and 1 other person) Glass Substrates for Devices 3, Relationship with the Amended Person Case Patent Applicant (307) Tokyo Shibaura Electric Co., Ltd. 4, Agent 100 March 29, 1973 (shipment date) Above

Claims (1)

[Scope of Claims] fil A glass substrate for a thin film device, characterized in that both sides of a low-melting point glass plate are covered with an insulator having a strain point higher than that of the plate glass. (2) A glass substrate for a thin film device according to claim 1, wherein the insulator is formed at a temperature that is 9150° C. or lower than the strain point of the plate glass. (3) The strain point of the insulator is 9200°C higher than that of plate glass.
The glass substrate for a thin film device according to claim 1, characterized in that the glass substrate is higher than or equal to 100%. (4) As an insulator, SiO2, AA20,
, 'rho2, Bed. TiO2, Ta20, , Y2O, , ZrO2,
Si3N, , TaN. The glass substrate for a thin film device according to claim 1, characterized in that BN or AlN is used. (5) The thickness of the insulator is 0. The glass substrate for a thin film device according to claim 1, characterized in that it has a thickness of 5 to 10μ.