JPS6339676B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for dry etching various films used in the manufacture of semiconductor devices and the like. The present invention aims to obtain finer structure and reliability of etching through dry etching, and also to facilitate maintenance of the apparatus.

In a method of manufacturing a semiconductor device, wet etching using a mixed solution such as hydrofluoric acid has been used to etch the surface of a semiconductor substrate or various films formed on the surface of a semiconductor substrate. Recently, however, dry etching using a plasma-like gas using a reactive gas and high-frequency discharge has been carried out to etch these films.

This dry etching has various advantages over conventional wet etching. It does not require the use of large amounts of acids and the accompanying need for pure water for cleaning. As a result, in the manufacturing process of semiconductor devices, handling becomes easier and the risk to workers is greatly reduced. Furthermore, dry etching has made a big leap forward in terms of miniaturization compared to conventional wet etching. The reason for this is that in conventional wet etching, the etching mask wraps around the etching mask at the edge of the opening. This is called etching isotropy, and the penetration of the etching solution under the etching mask is approximately equal to the thickness of the film to be etched or the etching depth. In comparison, dry etching, especially a method that ionizes a reactive gas and is called reactive ion etching or reactive sputter etching, prevents etching from penetrating under the etching mask, and etches only the openings of the etching mask. This has nothing to do with the etching depth.
This etching is said to have very high precision and good anisotropy.

However, even this dry etching method, which has excellent anisotropy, has various drawbacks, and measures have been taken to improve these drawbacks.

The drawback is that a large amount of etching cannot be performed at one time. The reason for this is that, as described above, a high frequency electric field is applied to the reactive gas to turn the gas into a plasma state, which requires a large exhaust system. This places great restrictions on the size of the device. However, in order to carry out this purpose, the device must have a large vacuum evacuation capacity.

In addition, in dry etching, since a plasma-like gas is used for etching, depending on the method and conditions in which the gas contacts the semiconductor substrate to be etched,
The uniformity of the etching amount is greatly affected. Considering the uniformity, the simple solution is to expand the area of the electrodes in the etching chamber, improve the uniformity of the plasma gas in the etching chamber, and hold the semiconductor substrate in the plasma gas. This would require the use of large equipment with the same drawbacks mentioned above.

In addition to the device structure described above, a structure in which semiconductor substrates are buried one by one has been proposed in order to avoid increasing the size of the device and to improve uniformity. This single-wafer processing equipment places semiconductor substrates in cassettes,
The material leaves the etching chamber from one input side and is delivered to the other output side. This kind of equipment is suitable for automation, and if the film to be etched on the semiconductor substrate is processed in a relatively short time,
Very effective. In particular, it is preferable that the film to be etched be a polycrystalline silicon film or a silicon nitride film that can be etched in a short time.

However, for relatively thick films such as silicon oxide films and aluminum films, which require time to etch, it is disadvantageous in terms of time when a large number of films are to be processed. Furthermore, when etching thin metal films such as aluminum films, the etching chamber is contaminated by reaction products with reactive gases, and the etching ability or vacuum ability of the apparatus decreases after only a few sheets have been etched. Therefore, when performing such etching, the equipment must be cleaned for a certain period of time or for a certain number of sheets. The work is
First, the reaction products inside were removed, and then the etching chamber was cleaned to create a high vacuum.

As described above, both the apparatus for etching a large number of substrates at once and the apparatus for etching one substrate at a time each have their own problems, and there are many points that need to be improved in the manufacturing process of semiconductor devices.

The structure of the present invention includes a plurality of etching chambers having a parallel plate electrode structure, for example, in a preparatory chamber that can be depressurized, and further has a cassette installation chamber that is integrated with the preparatory chamber and can be depressurized.

A semiconductor substrate is placed in one cassette, and an empty cassette in which no semiconductor substrate is placed in the other cassette is prepared, and each is set in a cassette installation chamber that can be depressurized.
At this time, the cassette installation chamber is under normal pressure, and the other preliminary chambers and etching chambers are maintained under reduced pressure.

Subsequently, the pressure in the cassette installation chamber is reduced, and when the pressure reaches the same level as that in the preliminary chamber, the intermediate shutter is opened and the semiconductor substrate is moved from the cassette installation chamber to the preliminary chamber.
The movement is particularly carried out by belt conveyance or chuck conveyance. After the cassettes are installed in the preliminary chamber, the shutter located between the cassette installation chamber and the cassette installation chamber is closed, and then only the preliminary chamber and one of the plurality of etching chambers, for example, the one close to the cassette loading side, are kept at the same pressure, and the pressure inside the etching chamber is kept the same. Guide the semiconductor substrate. Subsequently, the etching chamber is evacuated to a higher level than the preliminary chamber, a reactive gas is introduced, and a high frequency electric field is applied between the parallel plate electrodes to turn the reactive gas into a plasma and perform etching.

The other etching chambers can of course perform etching using the same reactive gas as one etching chamber, but they can also be used for post-processing of the semiconductor substrate after one etching is completed. In that case, the reactive gas introduced into each etching chamber is changed and the gas is introduced in accordance with the purpose.

Furthermore, in this dry etching apparatus, it is also possible to switch the functions of the semiconductor substrate carry-out side and the carry-in side. The function of the etching chamber at this time can be considered depending on the etching material used for the semiconductor substrate, and the use of the apparatus can be differentiated between cases where the inner wall of the etching chamber is easily contaminated and etching where the inner wall of the etching chamber is easily contaminated. In other words, one of the multiple etching chambers is used for the one that is more likely to be contaminated with etching products, and the others are used for those that are relatively less contaminated or generate gas plasma for cleaning. Reverse the usage of the multiple pieces,
Maintenance of an etching chamber using reactive gas can be greatly reduced.

The invention will be explained in detail by means of embodiments shown in the following figures.

FIG. 1 is an external view of a dry etching apparatus according to an embodiment of the present invention. At the rear of the etching apparatus main body 1, there is a vacuum pump unit 2 for reducing the pressure in the preliminary chamber, the etching chamber installed therein, and the cassette installation chamber. Further, next to the main body of the etching apparatus, there is installed a control section 3 that controls the operation of the main body and includes a high frequency power supply unit.

FIG. 2 is an enlarged perspective view of the main body of the dry etching apparatus shown in FIG. 1. FIG. 3 is a transparent perspective view of a preliminary chamber, an etching chamber, and a cassette installation chamber of the main body portion.

Inside the preliminary chamber 21, there are two etching chambers 2.
2 is installed. The two etching chambers 22 have a cylindrical shape, and two gas pipes 25 for introducing gas into the etching chamber 24 are installed in the upper part 23 of each etching chamber. The gas pipe 25 is connected to the outer preliminary chamber 21 by a flexible pipe 26 and is fixed to the wall of the preliminary chamber 21 so that it can be connected to an external pipe (not shown). The etching chamber 22 has a vertical mechanism (not shown), which moves the semiconductor substrate 27 upward to set it therein. The etching chamber 24 is composed of two chambers, a gas introduction chamber 24-1 and a reaction chamber 24-2. Between the chambers is an upper electrode 28 with a number of holes for gas blowout. Lower electrode 29
is located below the semiconductor substrate 27 and has a structure that also serves as a sample stage.

Although only one of the etching chambers was illustrated in FIG. 2, the other etching chamber also has a similar structure.

Next, the cassette installation room 3 is integrated into the preliminary room 21.
0 is set. The cassette installation room 30 has two
Two cassettes 31 and 32 are installed. Further, a mechanism 33 for transporting the semiconductor substrate 27 is housed inside the cassette installation chamber, and is used to transport the semiconductor substrate 27 to a predetermined position. A passage hole 34 through which a semiconductor substrate passes is provided between the cassette installation chamber 30 and the preliminary chamber 21. This passage hole 34 is provided with a shutter (not shown), which is opened when the pressure difference between the cassette installation chamber 30 and the preliminary chamber 21 disappears.

Although the structure and configuration are as described above, the operation will be explained in detail next.

First, only the cassette installation chamber 30 is kept at normal pressure, and the other preliminary chambers and two etching chambers are kept at high vacuum. However, the pressure difference between the preparatory chamber and the etching chamber requires that the etching chamber be maintained at a higher vacuum than the preparatory chamber. A cassette with a semiconductor substrate mounted thereon is placed in one of the cassette installation chambers under normal pressure, and an empty cassette is placed in the other. Next, reduce the pressure in the cassette installation chamber to the same pressure as the preliminary chamber.
Open the shutter provided in the middle passage hole,
Transport the semiconductor substrate to the preliminary room and close the shutter. Next, the pressures in the preliminary chamber and one of the etching chambers are made the same, and the substrate is placed in the center of the etching chamber using a transfer arm or the like.

Next, the etching chamber is closed, the pressure is further reduced to a high vacuum, a reactive gas is introduced at a constant pressure, and a high frequency electric field is applied to turn the gas into a plasma and perform etching.

When the etching is completed, the etching chamber is brought to a high vacuum again, then to the same pressure as the preparatory chamber, and then opened and transferred to the other etching chamber in the same order as described above for the next processing. At this time, the next semiconductor substrate is transported to the etching chamber where reactive gas is introduced.
To enable continuous etching and post-processing such as resist removal after etching.

The semiconductor substrates thus successively subjected to the etching process and placed in one cassette are then filled into the other empty cassette after completing the etching and post-processing as described above.

For example, when etching a polycrystalline silicon film and a silicon oxide film, one etches the polycrystalline silicon film and the other a silicon oxide film, or if there is only a polycrystalline silicon film, one etches the polycrystalline silicon film. A crystalline silicon film can be used as a resist mask on the other hand, or an alumina film can be etched on the other hand, and an aluminum film can be etched in the case of a metal film such as an aluminum film. Also,
Various methods can be used, such as removing the aluminum film and subsequent resist, or heat-treating the resist.

Further, it is also possible to carry out etching in one chamber while cleaning the etching in the other, so that one of the etching chambers is always in operation.

As described above, the present invention can maintain a high vacuum at all times without exposing the etching chamber to outside air by placing a plurality of etching chambers in the preliminary chamber.
Etching can be performed under constant ambient conditions for the material to be etched. Furthermore, by installing a plurality of etching chambers, one can always be used for a different purpose such as cleaning, making it possible to use it for multiple purposes. This increases work efficiency, and by actively cleaning, maintenance can be significantly reduced. Further, by placing the etching chamber in the preliminary chamber, great effects such as miniaturization of the apparatus can be achieved.

[Brief explanation of the drawing]

FIG. 1 is an external view of a dry etching apparatus according to an embodiment of the present invention, and FIG. 2 is a partially cutaway perspective view of a preliminary chamber, an etching chamber, and a cassette installation chamber of the dry etching apparatus. 21...Preliminary room, 22...Etching room, 24
...Etching chamber, 27...Semiconductor substrate, 28
... Upper electrode, 29 ... Lower electrode, 30 ... Cassette installation chamber, 31, 32 ... Cassette, 34 ...
Passing hole.

Claims (1)

[Scope of Claims] 1. A dry etching apparatus comprising a plurality of etching chambers and a cassette installation chamber capable of reducing pressure in a preliminary chamber capable of reducing pressure. 2. The dry etching apparatus according to claim 1, having two etching chambers, wherein one etching chamber performs etching and the other etching chamber is simultaneously cleaned. 3. The dry etching apparatus according to claim 1, wherein at least two cassettes can be installed in the cassette installation chamber, and the loading side and unloading side can be changed arbitrarily.