JPS6184066A - Manufacture of thin film transistor - Google Patents

Abstract

PURPOSE:To constitute a thin film transistor into a structure having no step difference and to inhibit the leakage current between the gate and source electrodes and that between the gate and drain electrodes by a method wherein a metal layer, which is used as the material for the source and drain electrodes, is coated on the whole surface of the substrate and after parts of the metal layer other than the metal layer at the programming regions for forming the source and drain electrodes are oxidized, the semiconductor thin film, the gate oxide film and the gate electrode are provided on the source and drain electrodes. CONSTITUTION:A Ta film is coated on an insulative substrate 1 consisting of glass or quartz, the source electrode and drain electrode forming parts are respectively covered with a resist film and the exposing parts of the Ta film are anodized using a solution containing oxalic acid and are turned into Ta2O5 insulating layer 12. A source electrode 13 and a drain electrode 14, each consisting of the Ta film made to remain in such a way, are encircled with the layers 12, the surfaces thereof are flattened, the resist films are removed and a channel layer 15, which is extendedly laid on the edge parts of the layers 12, is formed on the electrodes 13 and 14. After that, a gate insulating layer 16 is coated thereon and a gate electrode 17 is provided thereon. According to such a way, the leakage current between the gate and source electrodes and that between the gate and drain electrodes become remarkably less.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for manufacturing a thin film transistor (hereinafter abbreviated as TPT).

(Conventional technology) FIG. 1 shows a cross-sectional view of the main parts of a conventional TPT.

As shown in Fig. 1, this manufacturing method involves coating nichrome (NiCr), tungsten (W), molybdenum (MO), chromium (Cr) on a glass substrate or alumina substrate 1.
), etc., is deposited using an electron beam evaporation method or a sputtering method, and processed into a predetermined i4 turn to form the y-upper electrode 2. On top of that, a silicon oxide (5inX) film or a silicon nitride (5iNX) film, which will become the date insulating layer 3, are deposited with N20 and SiH4, respectively.
, NH, and 5in4 as main component gases by a glow discharge method, and further an amorphous silicon semiconductor layer, which will become the active layer 4, is deposited by a glow discharge method using S r Ha.

Next, the portion other than the portion that will become TPT is processed and removed, and patterned into an island shape to form a dart insulating layer 3 and an active layer 4.

Next, aluminum (A
t) layer by vacuum evaporation method and processing.
T is completed.

(Problems to be Solved by the Invention) However, in the conventional technology, due to the step difference caused by the above-mentioned 2 r-upper electrodes (8 in FIG. 1), the dirt electrode and the source electrode,
Alternatively, since leakage between the r-upper electrode and the drain electrode is likely to occur, it is necessary to increase the thickness of the ketone insulating film 3.

Therefore, it is difficult to work with TPT, which is small and highly reliable.
was difficult to realize.

Furthermore, since the date insulating film becomes thicker, the threshold voltage (Vth) of the transistor inevitably increases.

An object of the present invention is to prevent the leakage current generated at the step portion of the dirt electrode described above and to manufacture a highly reliable TPT with a high yield.

(Means for Solving the Problems) The present invention first deposits metal as a source electrode and drain electrode material on the entire surface of the main part of the substrate, and then uses the metal layer as the source electrode and drain electrode material. A source electrode and a drain electrode are selectively formed by oxidation except for the region, and then a semiconductor thin film and a gate oxide film are deposited, and a gate electrode is formed. be.

(Function) In this way, since both electrodes are selectively formed by oxidizing the parts other than those that will become the source and drain electrodes, a structure with no steps can be achieved9. - Leakage current between the source electrode and the source electrode can be suppressed.

(Implementation) First, tantalum (Ta) is applied to the entire main part of the glass substrate or quartz substrate 1 by electron beam evaporation or sputtering.
) A film with a thickness of 100 to 1000λ is deposited.

After that, a patterning process is performed to cover only the parts that will become the source and drain electrodes using a lennost, etc., and then the electrodes are placed in a solution of distilled water with an acid added, and a direct current of several tens to hundreds of volts is applied using the mental side as the anode. By applying a voltage, anodic oxidation (chemical formation) is performed, and the entire exposed tantalum portion is converted into tantalum pentaoxide (Ta205) to form the insulating layer 12.
shall be.

Thereafter, the source electrode 13 and drain electrode 14 formed in predetermined patterns are formed by removing unnecessary renost and the like.

Next, an amorphous silicon semiconductor layer, which will become the channel layer (active layer) 15, is deposited by the glow discharge method of SII (a), and then silicon oxide (which will become the gate isolation R film I6) is deposited.
A 5inx) film or a silicon nitride (SiNyC) film is deposited by a glow discharge method using N20 and F3iH4, NH3 and SiH4 as main component gases, respectively.

Next, the parts other than those that will become TPT are processed and removed, and the grooves are turned into an island shape.

Finally, the dart electrode 17 is made of nichrome (NiCr), chromium (Cr), tungsten (W), and molybdenum (Mo).
) etc. by vacuum evaporation and processing to complete the TPT.

As a method for oxidizing the source and drain metals, in addition to the anodic oxidation method, the same effect can be achieved by using a plasma oxidation method using 0□ glazma.

Furthermore, although tantalum was used in the first embodiment, titanium (
Ti) or aluminum (At) or tungsten (W) is used as the material for the source and drain electrodes, and the unnecessary parts are anodized or plasma oxidized to form a titanium oxide layer (TlO2) and an aluminum oxide layer, respectively. (At203) Tungsten oxide layer (W
Even if O2) is formed, TPT is completed in the same way.

(Effects of the Invention) As described above, according to the present invention, anodic oxidation or plasma oxidation is performed when forming the source and drain electrodes, and unnecessary portions of the source and drain electrodes are oxidized and made into insulators. It has become possible to form a flat TPT with no steps due to the thickness of the electrode.

Therefore, leakage current between the dirt electrode and the source electrode, and between the gate electrode and the drain electrode can be suppressed to a minimum, and a small TPT can be formed.

Furthermore, this manufacturing method does not require expensive equipment and can be manufactured using normal processes, resulting in low cost.

In addition, high reliability is expected because step caperno is not a problem.

[Brief explanation of drawings]

The figure is a sectional view showing an example of TPT obtained by the present invention. l... Insulator substrate, 2... Insulating layer, 3... Source electrode, 4... Drain electrode, 5... Channel layer,
6... Straight insulating layer, 7... Kate electrode. Source tMoji procedural amendment (salmon) 1. Indication of the case 1982 Patent Application No. 204114 2 Name of the invention Method for manufacturing thin film transnostar 3 Person making the amendment Relationship with the case Patent application Person in charge Place (〒 105) 1-7-12-4 Toranomon, Minato-ku, Tokyo
Agent address (105) 1-7-1 Toranomon, Minato-ku, Tokyo
No. 2 No. 6 Contents of amendment 1: Insert the following sentence between "(Example)" on the second line of page 1 of the specification and "First, glass substrate..." on the third line. . ``A sectional view of the main parts of the uninvented TPT is shown in Figure 2.'' 2 On page 6, line 15 of the same book, before it says ``The figure is in accordance with the present invention,'' it says ``Figure 1 shows the main parts of the conventional TPT.'' Insert the sentence "Cross section, 2nd". On page 31, lines 17 to 19, the statement ``l... insulator substrate, 7... gate electrode.'' is corrected as follows. 1 - Insulator substrate, 12... Insulating layer, No. 3... Source voltage, 11... Thin-in electric drop, 15... Cha/ruin layer, j 6- Case insulation layer, No. 7
...Ke-Door 1L pierced (.) 41 The figure can be corrected as "Figure 2" as per the attached sheet, and "Figure 1" can be added as per the attached sheet.
Figure 1 is a sectional view of the rod of the T. Figure 2 is a curved view of the part of the TPT of the present invention.

Claims (1)

[Claims] A thin film transistor characterized in that the source electrode and the drain electrode are selectively formed by forming a metal layer that will become the source electrode and the drain electrode on the surface of the substrate, and then oxidizing the parts other than the parts that will become the source electrode and the drain electrode. manufacturing method.