JPS60211840A - Forming method for pattern - Google Patents

Abstract

PURPOSE:To prevent a glass substrate from damaging in the etching step of an amorphous silicon device by mixing etching as an mixture gas plasma of oxygen in the course of etching a titanium film by a plasma of carbon tetrachloride, thereby increasing the etching velocity of not only a molybdenum film but also the amorphous silicon film. CONSTITUTION:With a photoresist 38 as a mask a titanium film 37 is etched with etching gas of only carbon tetrachloride in plasma in a sample for a thin film transistor. Then, the film to be etched becomes gray of a molybdenum film 36 from white of the film 37. In this state oxygen gas is mixed in the plasma, and it is etched with the same discharging power. Then, the entire sample is colored with red amorphous silicon film 35. Further, an n<+> type amorphous silicon film 35 and a non-doped amorphous silicon film 34 are etched, become colorless silicon nitride film 33, and finished for the etching.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method for forming a pattern in the manufacturing process of a semiconductor device using amorphous silicon, particularly a method for forming a pattern on a titanium film and an amorphous silicon film at the same time. It is related to.

(Prior art and its problems) Development of semiconductor devices using amorphous silicon is progressing, and devices with larger areas are appearing. Devices using silicon crystal are mainly about 6 inches in diameter, whereas amorphous silicon devices are required to have a diameter of 15 inches or more. Furthermore, these amorphous silicon devices now require a manufacturing process that requires high-definition etching.

However, very few detailed data regarding etching of amorphous silicon have been published. This is because amorphous silicon contains a film containing many defects, hydrogen,
This seems to be because the film contains a large amount of fluorine, etc., and the interactions between the contained elements and defects and the etchant are unknown. C.F.
An example of dry etching amorphous silicon using 4 gases is published in the Journal of the Institute of Electronics and Communication Engineers, October 1981 issue.
Vol.

J64-C, No. 10, page 698, and for others, wet etching using an HF+HNO etching solution can be considered. Also, Anti! for amorphous silicon devices. Although AJ films are mainly used as metal films, we discovered various disadvantages when using AJ films and attempted to change the metal film to a titanium film. However, there is almost no detailed data regarding etching of titanium films.

Conventional etching processes for amorphous silicon devices have had various drawbacks. First, many amorphous silicon devices use glass substrates, and when an etchant containing fluorine is used, the smoothness of the glass is impaired, which poses a serious problem for devices that utilize light. Second, because the difference in etching rate between the amorphous silicon film and other films is small, there is a drawback that etching cannot be stopped accurately. Thirdly, there is non-uniformity in etching, resulting in a poor yield of large-area devices.

(Object of the Invention) The object of the present invention is to develop a pattern for an amorphous silicon device that solves the drawbacks of damage to the glass substrate in the conventional etching process of amorphous silicon devices, the drawbacks of a small difference in etching speed, and the drawbacks of poor etching uniformity. The object of the present invention is to provide a forming method.

(Structure of the Invention) According to the present invention, a mask is formed on a structure in which a molybdenum film and a titanium film are laminated on an amorphous silicon film, and the titanium film is etched using chlorine gas plasma to completely remove the titanium film. A pattern forming method is obtained in which the molybdenum film and the amorphous silicon film are etched by mixing oxygen into the gas plasma to advance the etching at the time when the molybdenum film and the amorphous silicon film can be removed.

Furthermore, according to the present invention, a mask is formed on a structure in which an amorphous silicon film and a titanium film are stacked on a titanium film patterned on an insulating substrate, and a titanium film and a titanium film are formed using chlorine-based gas plasma. A pattern characterized in that an amorphous silicon film is etched, and at the same time a part of the underlying titanium film is exposed, oxygen is mixed into the gas plasma to etch the remaining portion of the amorphous silicon film, and the underlying titanium film is used as an etching stopper. A forming method is obtained.

(Detailed explanation of the structure E!A) Next, novel experimental facts that form the basis of the present invention will be explained in detail using the drawings.

A parallel plate electrode type plasma etching apparatus was used. A pattern was formed using a photoresist mask, and etching was attempted on the amorphous silicon film and titanium film. As an etching gas, carbon tetrachloride was introduced into the plasma etching apparatus up to a pressure of g OmT orr, and plasma discharge was generated to perform etching. The etching rate (nm/min) obtained as a result is shown in FIG. 1 with respect to the applied RF discharge power (5). 11 shows the results obtained for the titanium film, and 12 shows the results obtained for the amorphous silicon film.

Next, etching was attempted by changing the ratio of oxygen mixed into carbon tetrachloride as the etching gas.

The pressure of the mixed gas introduced into the plasma etching apparatus was constant at 95 rnTorr, and the discharge power was also constant at 600 W. The resulting etching rate (nm/min
) is shown in Figure 2 as a mixture ratio of pressure of oxygen gas to carbon tetrachloride. 21 shows the titanium film with 22
are the results obtained for an amorphous silicon film. Although we have described an example using carbon tetrachloride as the etching gas, other well-known raw materials for generating chlorine in discharge plasma include boron trichloride, silicon tetrachloride, hydrogen chloride, and chlorine gas. It is the material.

From the above experimental results, it has been found that the following points are particularly significant for industrial use.

■Amorphous silicon film and titanium film should be etched to the same extent in carbon tetrachloride plasma.

■When plasma etching is performed using a mixture of carbon tetrachloride and oxygen gas, there is a significant difference in the etching speed of amorphous silicon and titanium films.

In addition, the etching surface is smooth, the etching speed of the glass substrate is extremely slow, no clouding occurs, the rate of pattern change is small, and a sufficient etching speed can be obtained with either the anode or cathode power supply method. It has become clear that the difference between a titanium film and an amorphous silicon film can be distinguished even in plasma by the difference in the color of the film. Based on the above results, the present invention has discovered a method of patterning an amorphous silicon device that solves the problems of the prior art.

Embodiments of the present invention will be described below with reference to the drawings.

Example 1. This example is an embodiment of Ml's invention. Figure 3(a)
, To explain using (b), a patterned molybdenum film 32 of 100 OA is adhered on a glass substrate 31, a silicon nitride film 33 with a thickness of 2000×, and a non-doped amorphous silicon film with a thickness of 300× are deposited on top of it. 34, Lintalk thickness 500X n+ amorphous silicon 35, 200A thickness molybdenum 11Si!
36. The thin film transistor sample on which the titanium film 37 with a thickness of 100 OA was formed was etched using a photoresist mask 38. A parallel plate electrode type plasma etching system was used, and an anode power supply system was adopted. Further, the RF free power was set to 500 (W). First, the titanium film 37 is etched in plasma using only carbon tetrachloride as an etching gas at 85 mTDrr. The titanium film was completely etched away in about 2 and a half minutes, and the etched film reached the molybdenum film 36. The etched film changed from the white of the titanium film 37 to the gray of the molybdenum film 36 over the entire surface of the sample. It was recognized by the change in color. This state is shown in FIG.
) was used for etching. In about 30 seconds, the color of the metal film on the amorphous silicon film disappeared over the entire surface of the sample, changing to a reddish color of the amorphous silicon film. Etching is further progressed, and the n+ amorphous silicon film 35 and the non-doped amorphous silicon film 34 are etched away. After approximately 3 minutes had elapsed, the etching was terminated when the reddish color of the amorphous silicon film being etched disappeared and was replaced by the colorless color of the silicon nitride film. The state is shown in Fig. 3+b>. Since the etching speed of a molybdenum film is slow with carbon tetrachloride plasma alone, by changing the etching gas during etching of this film and creating a mixed gas plasma of carbon tetrachloride and oxygen, not only a molybdenum film but also an amorphous silicon film can be etched. Since the etching speed is also high, the etching time can be shortened. In addition, non-uniformity in etching is corrected in areas where the etching rate is slow, such as a molybdenum film, and the etching rate is then increased, so that subsequent etching can be performed more uniformly. Furthermore, by finishing the etching on the silicon nitride film, which has an extremely slow etching rate, it was possible to eliminate non-uniformity in the amount of etching.

(Example 2) This example is an example of the second invention. Figure 4(a)
To explain using (b), a titanium film 42 with a Ni-turn pattern of 150X is adhered on a glass substrate 41, and a 300X thick phosphorus-doped n+ amorphous silicon layer 43. FJ Sa5000A nondo~
Poor amorphous silicon film 44, thickness 200A Amorphous silicon film 45, thickness 2000A
A 'pin diode sample on which a titanium film 46 of X was laminated was etched using a photoresist 47 mask. The state is shown in FIG. 4(a). A cathode power supply system was adopted using a parallel plate electrode type plasma etching system. Further, the RF power was set to 600 (W). First, the etching gas was carbon tetrachloride alone at 100 mTorr (mTorr).
), plasma is generated and titanium film 46F p+
+l, n+ layer amorphous silicon film 45.44
．． 43 are etched in sequence. Approximately 15 minutes after etching was first started, the color of a part of the etched surface of the amorphous silicone layer changed from reddish to the white color of the underlying titanium film. At the same time as this change, oxygen was introduced into the carbon tetrachloride plasma to a pressure ratio of 4096, and the pressure ratio was 100 (rnTorr), 600
Etching was continued in the same manner with (W). As a result, after about 30 seconds, the color of the etched portion on the entire surface of the sample became the white color of the titanium film, so the etching was terminated. This break is shown in FIG. 4(b). When the etching reaches even a part of the underlying titanium film, the plasma is changed to oxygen-containing plasma, so that the underlying titanium film is hardly etched and acts as a stopper, and only the parts where the amorphous silicon film remains unevenly are etched at high speed. As a result, there was no disconnection of the underlying titanium film, and the amorphous silicon film could be etched with good uniformity.

(Effect of the invention) .

In the present invention, the glass substrate did not become rough at all, and the defective rate by visual inspection could be significantly reduced.

Etching of an amorphous silicon device using a titanium film can be performed using the same gas used for etching a dry-processed amorphous silicon film, simplifying the process. Furthermore, the method according to the present invention has a smaller pattern change rate than the conventional method, and can extremely reduce variations in device characteristics between elements. By changing the etching gas ratio during etching, the non-uniformity of the etching thickness was eliminated, and the selectivity to the underlying titanium film was increased, thereby preventing disconnection of the lower titanium film.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the etching rate with respect to the discharge power, Fig. 2 is a diagram showing the etching rate with respect to the mixing ratio of carbon tetrachloride and oxygen, and Fig. 3 (at, (b)) explains the first invention of the present application. Figure 3 (
a) is a diagram showing the structure during etching when the etching gas is changed, M3 diagram (b) is a diagram showing the structure at the end of etching, and FIGS. Figure 4 (
a) shows the structure before etching, and FIG. 4 shows the structure after etching with different etching gases. Etching characteristics for amorphous silicon film, 31.41 is a glass substrate, 3
2.36 is a molybdenum film, 33 is a silicon nitride film, 34
, 35.43, 44.45 are amorphous silicon films,
37, 42, and 46 are titanium films, and 38° and 47 are photoresist) Ill, respectively. Figure 1 Figure 2 73 Figure 4 SR

Claims (1)

[Claims] 1. A mask is formed on a structure in which a molybdenum film and a titanium film are stacked on an amorphous silicon film, and the titanium film is completely removed by etching the titanium film using chlorine-based gas plasma. A pattern forming method comprising the step of etching the molybdenum film and the amorphous silicon film by mixing oxygen into the gas plasma when the etching is completed. 2. On the titanium film patterned on the insulating substrate,
Furthermore, a mask is formed on the structure in which the amorphous silicon film and the titanium film are laminated, and the titanium film and the amorphous silicon film are etched using chlorine-based gas plasma. 1. A method for forming a pattern δ, which is characterized in that the remaining portion of the amorphous silicon film is etched by mixing oxygen into the etching film, and the underlying titanium film is used as an etching stopper.