JPH0794491A - Dry etching method and dry etching treatment apparatus - Google Patents

Abstract

PURPOSE:To etch Si or GaAs selectively in relation to SiO, SiO2, SiC or Al by forming high-density hydrogen radicals by a microwave discharge to hydrogen and by applying the hydrogen radicals onto the surface of the Si or the GaAs. CONSTITUTION:A reaction vessel 2 made of stainless steel is joined to a hydrogen radical producing chamber 1 made of quartz glass. Moreover, a sample stage 3 is provided in the reaction vessel 2 and a sample 4 to be treated is set on this stage. Besides, a heater 5 is provided inside the sample stage 3 and thereby the temperature of the sample 4 to be treated is controlled. In a treatment apparatus thus constructed, hedrogen radicals 6 produced in the hydrogen radical producing chamber 1 are applied onto the sample 4 to be treated, so as to etch Si or GaAs selectively in relation to SiN, SiO2, SiC or Al. Thereby the in-plane uniformity of etching and the precision of etching can be increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dry etching processing apparatus used in an etching processing step for manufacturing a semiconductor device.

[0002]

2. Description of the Related Art A technique for forming a semiconductor device used in a large area display device such as a liquid crystal display is a semiconductor thin film,
This is a composite technology of a technique for forming an insulating thin film and a metal thin film, a technique for patterning a resist, and a technique for etching a semiconductor layer and the like using these as a mask. Improving the uniformity of a processing technology that combines these film forming and etching processes over a wide area is important for improving the yield and reliability of products.

For example, in a process of forming a reverse staggered structure thin film transistor which is a mainstream of a current practical thin film transistor, for example, a technique of selectively etching and removing only a Si layer with respect to an underlying SiN or SiO ₂ is required.

A reactive plasma etching apparatus has been mainly used for such an etching process. In this device, a sample to be treated is placed in a reaction vessel equipped with a pair of parallel plate type electrode structures, and a high frequency power of 13.6 MHz is applied to discharge a fluorocarbon gas, an SF ₆ gas, and a halogen gas to generate them. It is a method of etching a sample to be processed using the gas plasma. There is also an ECR plasma etching apparatus. In this method, an ECR plasma discharge using microwave is used to produce a fluorocarbon gas, SF gas.
₆ gas or halogen-based gas is decomposed and etching is performed. This point is similar to the reactive plasma etching.

As a method of etching GaAs in a gas phase, in addition to reactive plasma etching using a halogen-based gas, a method of using HCl or a method of introducing AsCl ₃ into a high temperature hydrogen atmosphere to generate HCl. The method is common. These take advantage of the corrosive nature of HCl. As another example, a method of etching GaAs with hydrogen gas at a high temperature of 800 to 900 ° C. has been proposed (J.
Appl. Phys. 60 (1981) 1501). As another example, as described in JP-A-5-102109, there is a report that the temperature at which etching occurs is lowered to 550 ° C. by adding a slight amount of AsH ₃ to H ₂ .

[0006]

PROBLEMS TO BE SOLVED BY THE INVENTION Polycrystalline Si and SiO ₂
As an example of dry etching treatment for
As described in Japanese Patent No. 58176, a reactive ion etching method using ECR plasma discharge of a gas containing chlorine as a main component has been proposed. In this case, polycrystalline Si and Si
The etching rate ratio of O ₂ is 20.

For hydrogenated amorphous Si, as described in the proceedings of the 39th Joint Lecture on Applied Physics (Spring Convention 1992) Proceedings 501, page No. 28a-NC-5, SF ₆ or A reactive plasma etching method using a gas in which SF ₆ is mixed with oxygen and chlorofluorocarbon has been attempted. In this case, the etching rate ratio of hydrogenated amorphous silicon and SiN is about 7.

As described above, in the conventional dry etching method using the CFC-based gas, the SF ₆ gas and the halogen-based gas, Si or GaAs is etched with complete selectivity with respect to SiO ₂ , SiN, SiC or Al. Was difficult.

The size of a large area display device is aimed at 10 inches or more. Even if the area of the object to be processed becomes large, the in-plane uniformity and accuracy of processing must be maintained. But,
In the conventional method, the processing accuracy of the semiconductor device decreases as the area increases due to the low etching selectivity and the decrease in the in-plane uniformity of etching accompanying the increase in the area. Further, it is considered that the in-plane uniformity of the film thickness of the layer to be removed by etching is also reduced as the area is increased. Such a decrease in the in-plane uniformity of the film thickness further deteriorates the processing accuracy.

As described above, with the recent increase in size of large-area display devices, it becomes difficult to maintain the processing accuracy of semiconductor devices over the entire area of the substrate. For example, S
In the process of removing the Si layer on the iO ₂ , if the processing accuracy is poor, some parts of the substrate surface are over-etched to the inside of the SiO ₂ layer, whereas other parts are etched of the Si layer. There is a situation where has not finished yet. Similar problems occur in the ECR dry etching method using chlorofluorocarbon gas.

G by the conventional reactive ion etching method
Even in the dry etching treatment of aAs, the same problem of low selectivity as described above occurs. Further, in the etching method using a corrosive gas such as HCl, the reactor itself may be corroded by the etching gas.

If the CFC gas used as the etching medium is released into the atmosphere as it is, it may cause environmental damage. Therefore, in a dry etching apparatus using chlorofluorocarbon gas, post-treatment of exhaust gas must be strictly performed. However, the treatment of CFCs is not easy because CFCs are chemically stable. Halogen-based gas has the problem of being corrosive and toxic.

The present invention overcomes the low etch selectivity in conventional dry etching of Si and GaAs,
The purpose is to lower the temperature of GaAs etching process and to develop a pollution-free etching medium that replaces fluorocarbon gas and halogen gas.

[0014]

The inventors of the present invention have conducted extensive studies to develop a method of dry etching Si or GaAs from other materials with high selectivity. As a result, it was found that silicon can be etched at 20 ° C. or higher by irradiating the surface of the sample to be etched with high-density hydrogen radicals formed by microwave discharge of hydrogen gas. In particular, it was found that the hydrogenated amorphous silicon has a high etching rate, and that a higher etching rate can be obtained than that of the conventional plasma etching method using CFC gas. It was also found that GaAs can be etched at a low temperature of 300 ° C. Furthermore, SiN, Si
It has been found that Si or GaAs can be selectively etched with respect to O ₂ , SiC or Al.

The present invention has been made based on these findings. That is, according to the present invention, a high-density hydrogen radical is formed by microwave discharge of hydrogen, and the hydrogen radical is treated by irradiating the surface of Si or GaAs with SiN or SiO.
₂ , a method of selectively etching SiC or Al, and a dry etching treatment apparatus for performing the above treatment.

[0016]

Thus, by using the above-mentioned gaseous etching medium, SiN, SiO ₂ , SiC or Al
It is possible to etch Si or GaAs without etching at all.

The material to be etched used in the method of the present invention is crystalline Si, polycrystalline Si, amorphous Si or G.
aAs can be used.

Si used as a sample to be processed in the present invention
Since the presence of a slight natural oxide film on the surface hinders the progress of etching, it is necessary to use a sample to be etched from which the surface natural oxide film has been removed.

The Si etching is carried out while maintaining the processing temperature at 20 ° C. or higher. In the case of etching hydrogenated amorphous Si, since a sufficient etching rate can be obtained at 50 ° C. or lower, a general resist material can be used as a mask.

Resist (OF) by irradiation of hydrogen radicals
PR800 and OMR80 (manufactured by Tokyo Ohka) do not cause film loss or deterioration.

[0021]

According to the method of the present invention, Si or G
aAs can be etched selectively with respect to SiN, SiO ₂ , SiC or Al. For example, SiN, Si
In the etching of Si formed on O ₂ , SiC or Al, the progress of the etching is automatically stopped when the etching of Si is finished and the underlying SiN or the like is exposed on the surface. Therefore, there is no fear of over-etching unlike the conventional etching method. For this reason, it becomes possible to dramatically improve the in-plane uniformity of etching and the etching accuracy required for forming a large-area device. In particular, when the method of the present invention is applied to the dry etching treatment of hydrogenated amorphous Si, it is possible to perform etching at a higher speed than conventional methods while maintaining high in-plane uniformity and high etching accuracy in the depth direction. Furthermore, it is not necessary to use a CFC-based gas that causes environmental damage, and the exhaust gas can be easily treated.

[0022]

The present invention will be described in more detail with reference to Examples. FIG. 1 shows an example of a reaction vessel equipped with a hydrogen radical production chamber. In the figure, a reaction vessel 2 made of stainless steel is connected to a hydrogen radical producing chamber 1 made of quartz glass. Reaction vessel 2
A sample table 3 is installed inside, and a sample to be processed 4 is placed on the sample table 3.
Put. A heater 5 is installed inside the sample table 3,
This controls the temperature of the sample to be etched. The sample 4 to be processed is irradiated with the hydrogen radicals 6 formed in the hydrogen radical generating chamber for etching.

In this example, 240 SCCM of hydrogen was supplied, the microwave output was 170 W, and the pressure in the reaction vessel was 0.
At 3 Torr, when the sample temperature to be etched is 50 ° C., the etching rate of hydrogenated amorphous Si is 27,000 A / mi.
n was obtained. Crystalline Si (100) at 300 ° C.,
The etching rate of crystalline GaAs is 23 A / m.
in, 83 A / min was obtained. SiN, SiO ₂ ,
SiC and Al were not etched at all in the temperature range of 20 to 300 ° C.

FIG. 3 shows the temperature dependence of the etching rate of hydrogenated amorphous Si. Supply hydrogen gas flow rate 245SCC
M, pressure 0.3 Torr. Etching rate is 20
It increased sharply from 0 ° C and became almost saturated at 100 ° C. It is considered that the reason why the etching rate tends to be saturated with respect to temperature is that the etching reaction is rate-controlled by the amount of the etching medium supplied.

FIG. 4 shows the microwave output dependence of the etching rate of hydrogenated amorphous Si. Supply hydrogen gas flow rate 24
5 SCCM, pressure 0.3 Torr, sample temperature 50 ° C. The etching rate tended to increase monotonically with increasing microwave power.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a dry etching processing apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic sectional view of a dry etching processing apparatus according to another embodiment of the present invention.

FIG. 3 is a graph showing the relationship between the temperature of a sample to be processed and the etching rate.

FIG. 4 is a graph showing the relationship between microwave output and etching rate.

[Explanation of symbols]

 1 Hydrogen Radical Generation Chamber 2 Reaction Vessel 3 Sample Stage 4 Sample to be Processed 5 Heater 6 Hydrogen Radical 7 Magnetron 8 Gas Introducing Tube 9 Exhaust Pipe 10 Quartz Glass 11 Waveguide

 ─────────────────────────────────────────────────── --- Continuation of the front page (72) Inventor Takashi Horimai 6-9, Fuji-cho, Hoya-shi, Tokyo 7-72 (72) Inventor Yasuo Tarui 5-6-4 Minamisawa, Higashi-Kurume-shi, Tokyo

Claims (5)

[Claims] 1. A dry etching method comprising using hydrogen radicals as a gaseous dry etching medium, and exposing a material to be etched to the gaseous etching medium. 2. A dry etching method using a gaseous etching medium according to claim 1, wherein Si is selectively etched with respect to SiN, SiO ₂ , SiC or Al. 3. A dry etching method using a gaseous etching medium according to claim 1, wherein GaAs is selectively etched with respect to SiN, SiO ₂ , SiC or Al. 4. A dry etching processing apparatus comprising a combination of the following parts. (A) A reaction vessel into which hydrogen gas is introduced and which is evacuated to a predetermined pressure. (B) A means for introducing a microwave into the reaction vessel and discharging the hydrogen gas to generate hydrogen radicals as an etching medium according to claim 1. (C) Gas supply means for supplying hydrogen gas into the reaction vessel. (D) Exhaust means for exhausting the inside of the reaction vessel. (E) A sample stand on which the sample to be processed, which exposes the film to be removed, is placed. (F) Means for controlling the temperature of the sample table. 5. The dry etching processing apparatus according to claim 4, wherein the reaction container has a structure in which a hydrogen radical generating chamber and an etching chamber for a sample to be processed are separated.