JPH04109678A - Thin film semiconductor device - Google Patents

Abstract

PURPOSE:To prevent disconnection of metal electrodes generated during microminiaturization of elements and improve reliability of metal electrodes by covering a region corresponding to the lower part of a contact hole on a glass substrate and the lower part of an active layer with an insulating film having resistance to hydrogen fluoride. CONSTITUTION:A thin film semiconductor device forming thin film semiconductor elements on a glass substrate 1, where a contact hole 7, used to lead the source-drain electrodes from an isolated active layer 2, is formed in such a shape as reaching not only the active layer 2 but also external side thereof and a region at least corresponding to the lower part of the contact hole 7 on the glass substrate 1 and the lower part of the active layer 2 are covered with an insulating film 10 having resistance to hydrogen fluoride. Thereby, disconnection of contact area is not generated and reliability of the stepped portion can be improved in the micro-miniaturized thin film semiconductor device.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to an insulating substrate for a thin film semiconductor device useful for manufacturing thin film semiconductor elements and image sensors, and particularly to an insulating substrate for forming a partial coating with a thin film of silicon nitride on the substrate. The present invention relates to a thin film semiconductor device in which a thin film semiconductor element is formed on an insulating substrate.

[Prior art]

Normally, to form a thin film transistor, polycrystalline silicon is formed on the entire surface of an insulating substrate and manufactured using photolithography technology or the like. In this case, impurities from the substrate (Na, Ca, Fe, AQ, W, etc.)
The diffusion of the
There were reliability issues.

A technique for forming an element after coating a glass substrate with a thin film of Sin, SiN, PSG, etc. is disclosed in Japanese Patent Application Laid-Open No. 59-8.
There is a publication No. 9436. This is a method in which the entire surface (front surface, front surface + back surface) is coated as a blocking layer for mobile ions contained in the glass substrate.

However, W from the insulating substrate to the thin film semiconductor element.

In order to prevent contamination due to diffusion of impurities such as heavy metals such as Fe, alkali metals such as Na, etc., when using an insulating film such as a silicon oxide film, a phosphorous glass film, or a silicon nitride film as a coating film for the substrate, In case of full-surface coating, defects may occur due to film formation, cracks may occur due to subsequent heat treatment, internal stress of the film during film formation, or 111! There is a drawback that peeling and cracking of the M# film is likely to occur due to thermal stress caused by the difference in coefficient of thermal expansion between the edge film and the insulating substrate. For this reason, it has been found that even if the entire surface of the substrate is coated with an insulating film, the desired effect cannot be obtained.

By the way, in a thin film semiconductor device in which a thin film semiconductor element is formed on a glass substrate, source, source, and
FIG. 2 shows a basic example of a thin film semiconductor device in which a contact hole for drawing out a drain electrode is shaped to reach not only the active layer but also the outside of the active layer. Both contact holes 7 are in the active layer region.

It is formed to have a smaller size than the active layer region. As a result, the dimensions of the contact hole 7 and the dimensions of the active layer region (L process), including the process margin, are limited, which has the drawback of limiting miniaturization of the device.

In a thin film semiconductor device in which the active layer region is separated by a thin film, it is conceivable to utilize this feature to miniaturize the element in the following manner.

That is, by not limiting the size of the contact hole only above the active layer region, restrictions on the size of the active layer can be reduced and the device can be miniaturized.

A diagram of the thin film semiconductor device at this time is shown in FIG.

However, the structure shown in FIG. 3 has the following problem. In other words, if a wet processing process is performed using an etchant containing HF to open a contact hole, a depression 6 will be created at the edge of the active layer as shown in FIG. 4, and a break IIIA9 will be created in the metal electrode in the next step. . Dry process, CDE (Chemical Dry Etching)
) also produces a depression 6 of a similar shape 6 On the other hand, RIE
(Reactive Ion Etching) has low material selectivity and is unsuitable for thin film semiconductor processes.

〔the purpose〕

An object of the present invention is to prevent disconnection of metal electrodes that occurs when the above-mentioned miniaturization is performed in a thin film semiconductor device, and to improve reliability of the metal electrodes.

〔composition〕

In order to achieve the above object, the present inventor has conducted intensive research and found that by applying partial coating to the vicinity of the isolated active layer of a thin film semiconductor device, and in the case of partial coating, dust The present invention was completed by confirming that it is possible to prevent disconnection of metal electrodes without causing problems such as defects and cracks caused by the above.

That is, the present invention is a thin film semiconductor device in which a thin film semiconductor element is formed on a glass substrate.

In a thin film semiconductor device in which a contact hole for drawing out source and drain electrodes from a separated active layer has a shape that reaches not only above the active layer but also to the outside of the active layer, at least a contact hole on a glass substrate is used. The present invention relates to a thin film semiconductor device characterized in that a portion corresponding to the lower part of the active layer and a lower part of the active layer are covered with a hydrogen fluoride-resistant insulating film.

The hydrogen fluoride-resistant insulating film has heat resistance (preferably 10
It is stable at 00° C.) and does not add impurities that become dopants to the semiconductor material, and a specific example is a silicon nitride film. This film thickness is usually 0.0
It is 5 to 1 μm, particularly preferably 0.2 to 0.4 μm.

The configuration of the present invention will be specifically explained with reference to the drawings.

In the present invention, as shown in FIG. 1, a thin film semiconductor device is formed by partially covering a glass substrate with an HF-resistant insulating film 10 such as a silicon nitride film.

That is, it is a thin film semiconductor device in which a silicon nitride film 10, an active layer 2 made of polysilicon, a gate oxide film 3 formed by thermally oxidizing active M2, and a gate electrode 4 made of polysilicon are formed on a quartz substrate 1. The contact hole 7 for drawing out the source and drain electrodes is formed in such a shape that it reaches not only above the active layer but also to the outside of the active layer and does not extend outside the silicon nitride film region.

〔Example〕

Although the present invention will be described in detail, the present invention is not limited thereto.

As shown in FIG. 1, the thin film semiconductor device of the present invention is manufactured by first depositing a silicon nitride film (silicon nitride film) on a quartz substrate.
- 1000 layers are deposited using the CVD method, and the covering layer 10 is formed using the photolithography etching technique.

Next, polysilicon is deposited to a thickness of 1200 nm using the LP-CVD method, and the active layer 2 of the transistor is formed using the photophosphorographic etching technique. Thermal oxidation was performed at 1020°C in a dry oxygen atmosphere to give an 80%
A thermal oxide film 3 of 0 is grown. Subsequently, 3,000 layers of polysilicon are deposited using the LP-CVD method, and the gate electrode 4 is formed using photophosphorographic etching technology. Next, using the ion implantation method, phosphorus (or boron) is implanted with an energy of 90Kev (30Kev for boron).
), and the doping amount is 4 x 10" atomic/ad. At this time, the gate electrode 4 and the source train region are implanted with impurities at the same time, and the source and drain regions are self-aligned with the gate electrode. Activation , N
2 atmosphere for 30 minutes at 900°C. Next, the eyebrow insulating film 5
3000 people deposited 5in2 using the LP-CVD method,
Contact hole 7 is formed using photolithography etching technology. At this time, the contact hole 7 is connected to the active layer 2.
Exposure is performed using a photomask with contact holes shaped to reach not only the top but also the outside of the active layer 2. Finally, for the metal electrode 8, AQ is deposited by sputtering and patterned by photolithography to complete the thin film M○S transistor device of the present invention.

〔effect〕

Since the present invention is configured as described above, it is possible to achieve the effect that there is no disconnection at the contact portion in a miniaturized thin film semiconductor device and the reliability at the step portion is improved, which is extremely important in industry. Useful.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing the structure of the thin film semiconductor device of the present invention;
Figure 2 is a cross-sectional view showing the structure of a basic example semiconductor device;
The figure is an explanatory diagram showing a portion where defects are likely to occur in a conventional device, and FIG. 4 is an enlarged explanatory diagram of the defective portion in FIG. 3. 1...Quartz substrate 2...Active layer 3...Gate oxide film 4...Gate electrode 5...Interlayer insulating film
6... Depression 7... Contact hole 8... Metal electrode 9... Disconnection part 10...
S i N, coating layer Fig. 1 Fig. 2

Claims (1)

[Claims] 1. A thin film semiconductor device in which a thin film semiconductor element is formed on a glass substrate, and the contact hole for drawing out the source and drain electrodes from the separated active layer reaches not only above the active layer but also outside the active layer. 1. A thin film semiconductor device having a hole, characterized in that at least a portion of a glass substrate corresponding to a lower portion of a contact hole and a lower portion of an active layer are covered with a hydrogen fluoride-resistant insulating film.