JPH03116737A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To obtain an electric connection with other electrode stably without vanishing the electrode of a material and to prevent deterioration of TFT characteristics by reducing an oxide film of metal formed in the case of removing resist by an oxygen plasma, with a hydrogen plasma. CONSTITUTION:A Cr gate electrode 22 is formed on a substrate 21, a silicon nitride 23 is deposited on a whole surface by a plasma CVD method, and an amorphous silicon semiconductor 24 is so deposited as to be partly superposed with the electrode 22. Then, it is coated with photoresist 25, an opening is formed on the Cr electrode by exposing, developing steps, and the silicon nitride in the opening 29 is removed by etching. Thereafter, a substrate is introduced into a plasma processor 27, oxygen gas is introduced, the resist is removed by ashing by means of a plasma discharging, hydrogen gas is then introduced instead of oxygen gas, continuously plasma-discharged, and exposed with hydrogen radical. Eventually, source.drain and connecting Al electrodes 26a, b, c are formed to complete a TFT.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for manufacturing semiconductor devices such as thin film transistors (hereinafter referred to as TPT), and particularly to a method for manufacturing semiconductor devices such as thin film transistors (hereinafter referred to as TPT). The present invention relates to a method for removing oxides on electrodes to obtain ohmic contact.

BACKGROUND OF THE INVENTION FIG. 4 shows a cross-sectional view of a conventional TPT process. Figure 4 (a
), a gate electrode 2 made of Cr or the like is formed on a substrate 1.
After selectively depositing the gate electrode 2, a gate insulating film 3 made of silicon nitride or the like is deposited on the entire surface, and an amorphous silicon semiconductor film 4 is further deposited so as to partially overlap the gate electrode 2.

Next, as shown in FIG. 4 et al., a photoresist 5 is coated, exposed and developed to form openings 7 in areas where electrical connection with the electrodes 2 is required. Thereafter, as shown in FIG. 4C, the gate insulating film in the opening 7 is removed by etching, and the photoresist is removed by ashes using oxygen plasma in a vacuum chamber. Finally, as shown in FIG. 4(d), source/drain electrodes 6a, s, 6b made of A1, etc. and an electrode 6C for electrical connection with the gate electrode 2 are selectively deposited to form TPT. Complete.

Problems to be Solved by the Invention In the above-described manufacturing method, Cr oxide is formed on the surface of the Cr gate electrode 2 when the resist is removed using oxygen plasma. Since this Cr oxide film cannot be easily removed with a general acidic aqueous solution such as dilute hydrofluoric acid, it becomes a resistance between the Cr gate electrode 2 and the AI electrode 6c, and the curve (
As shown in b), a normal electrical connection such as the current not increasing linearly with the applied voltage between the Cr-Al electrodes cannot be obtained, and this causes deterioration of the TPT characteristics. A defect occurred (see Figure 3).
Conventionally, Cr oxide was removed using a special etching solution containing cerium ammonium nitrate as a main component.

However, the uniformity of etching is poor and Cr itself is etched, which not only complicates process control, but also causes parts where Cr is not removed, and Cr itself to be etched.
A defect occurred in which the electrode disappeared.

The present invention was conceived to solve this problem, and provides a method for easily removing the oxide film to obtain normal electrical connection.
It is an object of the present invention to provide a manufacturing method that does not cause deterioration of PT characteristics.

Means for Solving the Problems In order to solve the above problems, the present invention removes the resist using oxygen plasma and then removes the oxide film by exposing the resist to a hydrogen radical atmosphere generated by plasma discharge or light.

Function: According to the present invention, the oxide film formed on the surface is reduced by the above-mentioned technical means, and an effect similar to that obtained by removing the oxide film can be obtained, so that a good electrical connection can be obtained. Furthermore, once the oxide film is removed, further reduction reactions stop, so the metal material does not disappear.

Example Examples of the present invention will be described below.

FIG. 1 shows a process sectional view of this embodiment. As shown in FIG. 1(a), a Cr gate electrode 22 is formed on a substrate 21,
Silicon nitride 23 is deposited over the entire surface by plasma CVD, and amorphous silicon semiconductor 24 is deposited so as to partially overlap gate electrode 22 . Next, a photoresist 25 is applied, and an opening is formed on the Cr electrode by exposure and development steps as shown in FIG. 1, etc., and the silicon nitride in the opening 29 is etched away. Thereafter, as shown in FIG. 1(C), the substrate is placed in a plasma processing apparatus 27, oxygen gas is introduced and the resist is incinerated and removed by plasma discharge, and then hydrogen gas is introduced instead of oxygen gas. Vacuum degree I
Plasma discharge was performed continuously under the conditions of Torr, discharge power of 300 mW/cd, and discharge time of 5 minutes, and the specimen was exposed to hydrogen radicals. Finally, as shown in FIG. 1(d), the source/drain and connecting AI electrodes 26a, b, c are formed to complete the TPT according to the manufacturing method of this embodiment.

The Cr gate electrode 22 and AI electrode 26 formed in this way
When measuring the current-voltage characteristics between C and C, as shown in the straight line (a) in Figure 2, the current increases linearly as the voltage increases, indicating that a good electrical connection is obtained. . Furthermore, when we evaluated the characteristics of the completed TPT, we found that the TPT produced by the conventional manufacturing method was
Compared to the previous model, the dark voltage was lower, the saturation current was increased, and the characteristics were improved.

Effects of the Invention As described above, the present invention uses hydrogen plasma to reduce the metal oxide film formed during resist removal using oxygen plasma, thereby stably removing the material electrode from the other side without losing it. Electrical connection with the electrode is obtained and T
This has the effect of providing a manufacturing method that does not cause deterioration of PT characteristics.

[Brief explanation of drawings]

Fig. 1 is a process sectional view of an embodiment of the present invention, Fig. 2 is a current-voltage characteristic diagram of the electrical connection part in the conventional and embodiment of the present invention, Fig. 3 is a TPT characteristic diagram, and Fig. 4 is a conventional FIG. 1.21...Glass substrate, 2,22...
・Cr electrode, 3.33... Gate insulating film, 4,
44...Semiconductor film, 5.25...Photoresist, 6,26...AI electrode, 27...
...Vacuum chamber, 28...Hydrogen plasma.

Claims (2)

[Claims] (1) A step of selectively forming a first conductive layer made of a metal or a semiconductor on one main surface of the substrate, a step of covering the entire surface with an insulating layer, and a step of coating the first conductive layer on the first conductive layer. a step of removing a resist for forming an opening in a part of the insulating layer using oxygen plasma in a vacuum chamber;
a step of exposing the surface of the conductor layer to a hydrogen radical atmosphere in a vacuum chamber; and a step of selectively forming a second conductor layer so as to be electrically connected to the first conductor layer. A method for manufacturing a semiconductor device comprising: (2) Claim (1) characterized in that the hydrogen radical atmosphere is formed by plasma discharge using hydrogen gas.
) A method for manufacturing a semiconductor device according to the method.