JPS58164267A - Manufacture of thin film silicon transistor - Google Patents

Abstract

PURPOSE:To improve the yield and the reliability of a silicon transistor by slightly etching the surface of a transparent substrate, and then forming thin film Si transistor through an insulating film of a sole layer or multilayer of different purity and composition from those of the substrate. CONSTITUTION:The surface of a soda glass substrate 7 is slightly etched with HF diluted solution, the gate film 9 of a CVD SiO2 and a P-added polysilicon electrode are formed, and with the gate electrode as a mask P is implanted in high density. The CVD SiO2 film is covered, a window is opened, and metal wirings 10 of Al-Si alloy are attached. After the surface is slightly etched and cleaned in this manner, an insulating film of CVD SiO2, PSG, or Si3N4 of different composition from the transparent substrate in high purity is superposed in a sole layer or multilayer, and a thin film Si transistor is formed through the insulating film, thereby eliminating the invasion of contamination into the substrate, preventing the leakage of the surface of the substrate, stabilizing the initial characteristics and improving the yield.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thin film silicon transistor of polycrystalline silicon or amorphous silicon formed on a transparent substrate such as a quartz plate, soda glass, or neusilicate glass. In the midst of the so-called "neighborhood information society," there has been a remarkable development in combination printer-related equipment, and along with this, display devices have also changed from the conventional OR'! Flat displays are being actively developed as an alternative to '. In particular, flat displays that use liquid crystals are low power, low voltage, and light-receiving types, making them easy to read, making them useful not only in watch calculators but also in home appliances.

It has also been widely used in automobile panels.

Furthermore, a system in which liquid crystal is driven by an active matrix of thin film transistors is currently being considered as an inexpensive flat display that is attracting attention as an alternative to ORT.

This is a display panel for dual-image display, in which switching thin film transistor circuits are formed in a matrix on a transparent substrate, and liquid crystal is sealed between this substrate and another transparent glass plate.

The structure of a conventionally reported general thin film silicon transistor is as shown in FIG. 1. First, a thin film silicon 2 such as 1I1F crystal silicon or amorphous silicon is deposited on a transparent substrate 1 by IMIILIII and photo etching, leaving only a certain part of the transistor WI. Remove the thin film of silicon.

Next, an oxide film 1 is formed on the surface of the thin film silicon by a thermal oxidation method or a 071) method, and a thin film silicon for a gate electrode is deposited on the oxide film, and a gauge electrode is formed by photoetching. The gauge electrode is formed by directly depositing a thin silicon film containing impurities, or by depositing a thin silicon film and then thermally diffusing the impurities to lower the wiring resistance.

Next, ion implantation is performed on the i-layer of the gate electrode to form source and drain portions, and then an insulating film 4 is deposited on the main surface of the substrate.

Next, a contact F hole is formed by photo-etching, and then the metal wiring 5 is cut out.

As described above, in the conventional general manufacturing method of thin film silicon transistors, since the transparent substrate uses an insulating substrate such as a quartz plate or glass, the thin film silicon for forming the transistor is formed directly on the main surface of the substrate.

However, on the surface of these transparent substrates, abrasives such as aluminum powder or cerium oxide used for surface polishing adhere to surface irregularities such as polishing scratches, and apart from quartz plates, other glass substrates have sodium ions. Because it contains various mobile ions such as iron ions, metal ions such as iron ions, and sulfur ions, it is impossible to completely remove the contaminants even if the surface of the transparent substrate is cleaned in a general manner. It's impossible. For this reason, during the numerous heat treatment processes applied when forming thin film transistors on transparent substrates, these impurities penetrate into the thin film silicon and adversely affect the TNT characteristics, causing a decrease in the initial yield such as a decrease in ON current or an abnormal increase in 071F current. Of course, there is also a problem in terms of long-term reliability.

Moreover, in transparent substrates with poor purity, surface leakage of the substrate due to impurities is also seen as a problem.

Therefore, the present invention eliminates such conventional drawbacks and makes it possible to manufacture highly reliable thin film transistors.The present invention will be explained below using examples.

Embodiment 1 FIG. 92 shows a thin film silicon transistor formed on a transparent substrate with an insulating film 6 interposed therebetween according to the present invention.

First, after thoroughly cleaning the transparent substrate (using soda glass) 7, the surface was removed with a diluted solution of 70% acid.

Then, 50001% of oxidized J[6 was formed by the own method.

Then, a polycrystalline silicon film 8 is formed on this OVD oxide film 6.
0001 formed and photoetched to obtain a polycrystalline crystal of 9:1.
Leave only the F transistor forming part and remove the other parts of the conductive film.

Next, a gate oxide film is formed on the polycrystalline silicon film using the OVD method. 120001 is deposited, followed by depositing phosphorus-doped polycrystalline silicon for a gate electrode, and forming a gate electrode by photoetching.

Next, using the gauge electrode as a mask, phosphorus is ion-implanted at a high concentration.

After depositing 50,000 layers of oxide film by O'VD on the main surface of the transparent substrate including the transistor section where the source/drain is formed, a contact hole for the source/drain section is formed by photoetching.

Next, an aluminum silicon alloy was sputtered on the main surface of the substrate as a metal wiring material, and then metal wiring 1 was formed by photo-etching.
form 0.

As explained above, when forming a thin film silicon transistor on a transparent substrate, the present invention first slightly etches and removes the surface layer of the transparent substrate, and then forms a thin film via a VD oxide film of high purity and a composition different from that of the transparent substrate. Since silicon transistors are manufactured, it is necessary to prevent contaminants from entering the substrate, and also to prevent surface leakage due to impurities on the substrate surface, especially in the initial T1! A great effect has been obtained in stabilizing the characteristics.

In addition to the above-mentioned soda glass substrate, even if thin film silicon transistors (polycrystalline silicon and amorphous silicon transistors) are formed on porcelain glass or other transparent glass substrates in the same manner as in Example 1, the same results will be obtained. The stability of the characteristics has been firmly established.

Example 2 After thoroughly cleaning the transparent substrate 7', the surface layer was removed by etching 10001 with a diluted 7' acid solution, and then approximately 8 mol of phosphosilicate glass was deposited on the main surface of the substrate by CVD using phospine gas. A polycrystalline silicon film 8' is further formed in a thickness of 50,001. The following steps are the same as in Example 1.

By using phosphorus silicate glass as the insulating film, the getter action of phosphorus has a greater effect as a passivation agent than in Example 1, and a great effect is obtained not only in stabilizing the initial 〒νT characteristic but also in long-term stability. Ta.

Implementation H5 First, the transparent substrate 7'' was thoroughly cleaned, and then the surface of the substrate was etched with &'lRO001 using a diluted acid solution, and then argon paste 1-monosilane gas and 11 gas were added in a plasma ticker forming furnace. Then, a polycrystalline silicon film 8jIt was deposited at a temperature of about 550°C.
A thin film transistor was formed using the same steps as in Example 1, including T-type stamping.

This ticker film is formed using monosilane gas in plasma, and it is possible to form a dense film unique to ticker films at low temperatures, making it an extremely effective means for preventing the infiltration of contaminants. Therefore, an effect similar to or better than that of Example 1.2 is obtained.

Implementation (': ' In addition to s 2e 5, the insulating film is formed on a transparent substrate by spin-coding using a wavy coating agent known as a silica diffusion coating agent, and then heating it at a temperature of around 400°C to form an insulating film. Method of forming or liquid l
We have also tried methods of forming an insulating film using reimide resin, and each method has been found to be effective in stabilizing the characteristics.

Example 4 An example in which an active matrix is constructed using thin film silicon transistors according to the present invention will be described.

As shown in FIG.
After etching both 0xl1, the oxide film 12 is etched using the 0'VD method.
After depositing a polycrystalline silicon film 15, photoetching is performed to remove the transistor portion and remove the other polycrystalline silicon film.

Next, a gate oxide film 14 is formed on the polycrystalline silicon film by the CVD method, followed by a phosphorus-doped polycrystalline silicon film 15 for the gate electrode, and then a gate wiring portion is formed by photoetching. A source/drain portion is formed by ion implantation of phosphorus at a high concentration.

Next, an oxide film 16 is deposited on the main surface of the substrate by the own method, and then a direct hole is formed by photoetching.

Next, a transparent conductive film is sputtered by about 1500 cm, and after photo-etching, a transparent electrode layer 7 is formed.

Next, after sputtering AlAkebono silicon alloy for metal wiring, photoetching is performed to form metal wiring 41118 only on the source line.

As described above, the present invention relates to the production of a thin film silicon transistor formed using a transparent substrate. First, the polishing material such as alumina or cerium oxide fixed to the surface of the transparent substrate and the adhesive used during polishing are used. Etching is performed using a dilute solution of 7-acid to prevent dirt on the substrate surface from penetrating into the inside of the transistor in the subsequent process, and furthermore, it is possible to prevent dirt on the surface of the substrate from penetrating into the inside of the transistor in the subsequent process. Metal ions such as O are prevented from diffusing into the transistor by an insulating film formed in advance on the substrate surface.

Therefore, the T of the thin film silicon transistor according to the present invention is
? ? The characteristics are much more stable than those of the conventional method, and the variation in characteristics within the substrate is also greatly reduced.

Also, in an active matrix substrate using thin film silicon transistors/transistors formed by the above method, thin film silicon transistors can be formed! The νT characteristics are stable and the signal current ON10? The ν ratio was 104 or more, which was good. Moreover, the display characteristics were good in evaluations using liquid crystal display panels using active matrix F substrates, and there was no surface leakage compared to display panels manufactured using conventional methods, and there was no unevenness in brightness or darkness for each pixel, or both sides. It can be said that the present invention greatly contributes to stabilizing the characteristics and improving the long-term reliability of thin film silicon transistors since there are noticeable differences in display unevenness and the occurrence of defects depending on the location.

In the examples, all the insulating films formed on the transparent substrate are used as a single layer. For example, rather than using a single layer of oxide film by OVD method, phosphosilicate glass is first formed and then non-doped oxidized M[I It goes without saying that the passivation carbon effect of impurities is more effective in the formed two-layer insulating metal, and the five-layer method in which phosphorus silicate glass is sandwiched from both sides in the non-doped oxide layer further improves this effect. It has also been confirmed that it will.

Furthermore, when etching the surface of a transparent substrate, it is necessary to adjust the amount to be removed depending on the polishing condition of the substrate.

[Brief explanation of the drawing]

FIG. 1 shows a cross-sectional structure of a thin film silicon transistor formed on a transparent substrate using a conventional manufacturing method. FIG. 2 is a cross-sectional structure of a thin film silicon transistor formed on a transparent substrate according to the present invention. FIG. 3 is a partial cross-sectional structure of an active matrix substrate in which thin film transistors according to the present invention are arranged in a matrix on a transparent substrate. 1... Transparent substrate 2... Thin film silicon 3... Oxide film 4... Insulating film 5... Metal wiring ゛ 6... ... Insulating film (oxide film) 7.7/, 7# ... Transparent substrate 8.8', 8' ... Polycrystalline silicon! ...
... Gate oxide film 10 ... Metal wiring 11 ... Transparent substrate 12 ... Oxide film 13 ... Polycrystalline silicon 14 ...・Gate oxide film 15...Polycrystalline silicon film 16...Oxide film 17...Transparent electrode 1s...Metal wiring and above Applicant Kinsha Suwa Seiko Co., Ltd. Attorney Mogami Patent Attorney Figure 3

Claims (1)

[Scope of Claims] (1) In forming a thin film silicon transistor on a transparent substrate, the surface of the transparent substrate is first slightly etched, and then a thin film silicon transistor is formed on the transparent substrate via an insulating film. Features of thin film silicon;
Method of manufacturing nttunjista. (J) On the transparent substrate &: Claim 8, characterized in that the active insulating material is composed of a single layer or a multilayer insulating film of Ovng chemical film, phosphor silicate F glass, or Tikka film. A method for manufacturing thin film silicon transistors. (8) The method for manufacturing a thin film silicon transistor as described in the above paragraph, characterized in that the insulating film formed on the transparent substrate is formed by considering the purity and composition of the transparent substrate. .