JPH01157553A - Manufacture of thin-film circuit - Google Patents

Abstract

PURPOSE:To simplify a process by forming a contact hole in the following way: a lift-off material of metal is arranged and formed in a prescribed position; a gate insulating film is formed; after that, the lift-off material is etched and removed. CONSTITUTION:A gate material is evaporated on a glass substrate 1; it is etched or patterned by an evaporation lift-off method; a gate electrode 2 is formed. Then, a pattern of a lift-off material 3 is formed in a place where a contact hole is to be made; after that, a gate insulating film 4 is formed on the whole surface by a sputtering operation or the like. Then, the lift-off material is immersed in an etching solution; the lift-off material is etched; the gate insulating film is destroyed by applying a mechanical vibration and is removed; the contact hole is made. Then, a semiconductor layer 6 is formed; a source and drain electrode 7 is formed. By this setup, it is possible to manufacture this circuit in a simple process and at a low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for manufacturing a thin film circuit, and more particularly to a method suitable for manufacturing a linear image sensor having a drive circuit made up of thin film transistors.

Conventional technology Aiming to downsize facsimile machines, development is progressing on a close-contact image sensor that does not reduce the size of the document using an optical system and has the same size as the original, instead of the conventional reduction-type image sensor using CCD or MOS. In some cases, it has also been put into practical use.

The structure of contact image sensors can be roughly divided into thin film type (Cd
There are two types: S/Cd Se solid solution, a-3i, etc.) and Si single crystal type (CCC multi-chip type, bipolar transistor multi-chip type).

The thin film type has the advantage of being easy to increase in size, reducing the overall cost, and also being able to be used as a lensless type image sensor. - The blade wheel crystal Si type uses Sr single crystal process technology, which allows for fine processing and high speed, and has achieved high performance, but there are cost issues and it has not yet been put into practical use. This has not yet been achieved.

By the way, an optical sensor using a solid solution of a ■-■ compound has the advantage of a simple circuit configuration due to its large photocurrent, and it is also possible to combine it with a TPT made of a ■-■ compound semiconductor, so recently, the use of substrates has become more popular. Attempts have also been made to form a drive circuit composed of a sensor and a TFT semiconductor on the same substrate for the purpose of effective utilization, reduction of circuit and wiring costs, and the like.

An image sensor with an integrated TPT drive circuit has basically been manufactured through the steps shown below.

1. Formation of semiconductor film 2. Formation of counter electrode (sensor process) 3. Formation of protective film 4. Formation of gate electrode 5. Formation of gate insulating film 6. Formation of contact hole 7. Formation of semiconductor layer 8. Formation of source and drain electrodes 9, formation of wiring 10, and formation of protective film (above circuit processes) The point to be improved in the present invention is the formation of contact holes.

A conventional method of forming a contact hole in a gate insulating film will be described with reference to FIGS. 2 and 3.

The first method is an etching method as shown in FIG.

a) Gate electrode 2 and gate insulating film 3 on glass substrate 1
Form by overlapping.

b) A mask material 4 such as photoresist is patterned thereon in areas other than the areas where contact holes are to be formed.

C) Wet etching with hydrofluoric acid or general acid etching solution, or CFa, CCI, ArX0
A contact hole 5 is formed by etching by dry etching using two gases or the like, and then removing the resist.

d) forming a semiconductor layer 6;

e) Form source and drain electrodes 7 and connect them through contact holes.

The second method is a lift-off method using photoresist, as shown in FIG.

a) Gate electrode 2 and lift-off material (
Photoresist) 4 pattern is formed.

b) Form a gate insulating film 3.

C) Remove the photoresist and lift off unnecessary portions of the gate insulating film to form contact holes 5.

d) forming a semiconductor layer 6;

e) Source and drain electrodes 7 are formed and connected through contact holes.

In FIGS. 2 and 3, 8 indicates the remaining photoresist.

Problems to be Solved by the Invention According to the conventional method for forming contact holes, first of all, in the case of wet etching, it is difficult to find an etchant and etching conditions suitable for the type of film, and currently, hydrofluoric acid is mainly used. system, the etching solution must be handled with care, and the cost of waste solution processing equipment is high. Furthermore, since the etching rate is low, problems such as peeling off of the photoresist occur during etching.

In addition, in the case of dry etching, it is difficult to find gas and etching conditions that match the type of film, and there is also the problem of having to pattern the mask material again during the process, resulting in extremely poor efficiency (and resulting in high costs). The problem is that it is an expensive method.

On the other hand, when lift-off is used, the substrate temperature cannot be raised sufficiently during formation of the gate insulating film, and an insulating film of good quality cannot be obtained.

In the case of sputtering, the temperature of the substrate rises due to the energy of flying particles during film formation, or in the case of vapor deposition, due to heat radiation from the evaporation source, causing the resist to harden and remain as a residue during lift-off. However, there was a problem in that the contact with the overlapping electrodes was insufficient.

In view of these problems, the present invention provides a contact hole forming method that is a simpler process and lower cost than conventional contact hole forming methods, and does not impair the film quality of the gate insulating film. It is.

Means for Solving the Problems The thin film circuit of the present invention is manufactured by forming at least a first electrode on an insulating substrate in a thin film circuit manufacturing process in which a drive circuit composed of thin film elements is formed. process,
The steps include a step of forming an insulating film and a step of forming a contact hole, the contact hole is formed by placing a metal lift-off material at a predetermined position, and after forming the gate insulating film,
Formed by etching and removing lift-off material.

By forming contact holes by metal lift-off in the process of manufacturing functional thin film circuits, the problems shown in the prior art are solved, and the process is simple and low cost.

Embodiment FIG. 1 shows a portion of the manufacturing process of a thin film element according to the present invention, and the manufacturing process will be described below.

a) Depositing and etching the gate material on the glass substrate 1,
Alternatively, the gate electrode 2 is formed by patterning by vapor deposition lift-off.

b) Lift-off material 3 at the location where the contact hole will be formed
form a pattern. If the gate material and lift-off material are the same metal, a pattern may be formed at the location where the contact hole will be formed using a metal that is insoluble in the etching solution for the gate material, and then b) and a) may be reversed to perform the process.

C) Form a gate insulating film 4 on the entire surface by sputtering or the like.

d) Immerse in a lift-off material etching solution to etch the lift-off material and apply mechanical vibration to destroy and remove the gate insulating film to form a contact hole.

e) forming a semiconductor layer 6; Here, the order of d) and e) may be reversed.

f) forming source and drain electrodes 7;

The reason why the thickness of the lift-off material is set to 5 μm or less is because it takes time to form the lift-off material by vapor deposition and etching for patterning, and the lift-off is performed by using pin poles of the gate insulating film to insulate the gate. This is because the lift-off material under the film is etched, and then the gate insulating film floating in the chamber is crushed and removed by mechanical vibration, which takes time.

On the other hand, the reason why the current is set to 1000 A or higher is that the floating gate insulating film cannot be removed sufficiently if the current is lower than 1000 A.

Table 1 shows the temperature and time of the etching solution during contact hole formation and the contact hole formation status.
The circle mark indicates the formed state.

Table 1 As shown in Table 1, at 30'C, for 30 minutes,
At 60°C, etching is completed in 5 minutes. The reason why the etching time is set to 30 minutes or less is that if the etching time exceeds 30 minutes, side etching will have a negative effect on the element. The temperature of the etching solution was set to 3.0°C or higher at 30°C.
This is because the time required below is 30 minutes or more, and 6
The reason why the temperature was set at 0° C. or lower is that at 60° C. or higher, side etching similarly has an adverse effect on the device.

An example will be explained below based on FIG. 4.

a) Glass substrate (40x40x1.2III11#
7059, Corning Co.), a thin film optical sensor 1 is formed thereon, and a protective layer 2 is further formed thereon.

b) 50 OA of NiCr is deposited, etched and patterned to form the gate electrode 3.

c) Deposit AI at 2000 A and pattern it on the sensor electrode as a lift-off material 4.

d) AI2 as gate insulating film 5 by sputtering
's is deposited at 1500 A.

e) Immerse in an AI etching solution and apply ultrasonic waves to etch the AI of the lift-off material 4, remove the gate insulating film, and form the contact hole 6.

f) CdSe was evaporated at 1000 A and patterned,
A semiconductor layer 7 is formed.

g) Pattern photoresist and evaporate NiCr (10
00A) to form lift-off, source, and drain electrodes 8, and connect any of them to the sensor electrode and the contact hole 6.
Connect via.

h) Forming the protective layer 9 from polyimide.

In this example, NiCr was used as the gate electrode, but A
When I is used as the gate material, a pattern is formed using NiCr or the like at the location where the contact hole is to be formed.

Next, AI is deposited as a lift-off material and patterned on the NiCr. Then, AI is deposited as a gate material and patterned.

If such a method is used, metal remains in the contact hole after gate insulating film formation and AI lift-off, so it is possible to make contact.

The method shown in the embodiments described above does not have the above-mentioned problems that were conventional problems, has a simple process, and is a method that can reduce costs.

Effects of the Invention The method for manufacturing a thin film circuit according to the present invention provides a simple and low cost thin film circuit, and has great industrial value.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing an outline of the process of a thin film circuit manufacturing method according to the present invention, FIG. 2 is a cross-sectional view showing an outline of the process of a conventional thin film circuit manufacturing method (etching), and FIG.
The figure is a cross-sectional view schematically showing the process of a conventional thin film circuit manufacturing method (lift-off), and FIG. 4 is a cross-sectional view schematically showing the process in an embodiment of the present invention. 1...Glass substrate, 2...Gate electrode, 3...
... Lift-off material, 4... Gate insulating film, 6...
- Semiconductor layer, 7... electrode. Name of agent: Patent attorney Shigetaka Awano and 1 other person Dimensions of 1st drawing: c3-0
^1 Zu no d - faction ^ ” Kozuhe ^ He Q
℃＼O＼

Claims (2)

[Claims] (1) In the manufacturing process of a thin film circuit in which a drive circuit composed of thin film elements is formed and manufactured on an insulating substrate, at least a step of forming a first electrode, a step of forming an insulating film, a step of forming a contact hole; and a step of forming a second electrode connected to the first electrode through the contact hole.
The contact hole is formed by placing and forming a metal lift-off material at a predetermined position, forming an insulating film, and then etching and removing the lift-off material. Method. (2) A thin film circuit is an image sensor formed of a thin film,
2. The method of manufacturing a thin film circuit according to claim 1, wherein the thin film circuit is formed integrally with either a display or a thermal head on the same substrate, and is a driving circuit thereof.