JPS59119727A - Dry etching method - Google Patents

Abstract

PURPOSE:To avoid the adhesion of dust onto the surface by etching a body to be etched while surrounding the body to be etched by a cover with a plurality of minute holes when the body to be etched disposed into a chamber is etched through sputtering etching, ion etching, reactive ion etching or the like. CONSTITUTION:The bodies to be etched 3 are fitted on an electrode 2 in the chamber, and the bodies to be etched are surrounded by the covers 7. A semiconductor substrate in which a polycrystalline Si film to which P is doped is deposited on a Si wafer through an oxide film, etc. are used as the body to be etched 3, and a desired resist pattern is formed on the surface of the substrate. The cover 7 is constituted by a susceptor 9 in Al2O3, SiO2 or the like on which a net body 8, an upper surface thereof is opened and which is made of stainless, etc., is stretched and a porous filter 10, which is fixed to the upper surface of the susceptor and which has a plurality of minute holes and consists of carbon, etc. Accordingly, predetermined etching is executed to the body to be etched 3, and a Si film is etched without generating side etching.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for drying and etching an object to be etched such as Ueno.

[Technical background of the invention and its problems]

Conventionally, etching using a dry etching apparatus, such as a reactive ion etching apparatus shown in FIG. 1, has been carried out by the following method. That is, first, the object to be etched 3 is placed on the electrode 2 in the channel 1. These objects to be etched 3 are made by depositing a phosphorous doped polycrystalline silicon film on a silicon wafer 1 via an insulating film, and a resist pattern is further formed on the surface of the polycrystalline silicon film. Next, the chamber
1 A vacuum pump 5 connected to the bottom via a butterfly valve 4
is operated to remove the air from the channels 1, and CC24 gas and 02 gas are introduced from the gas inlet 6, so that the respective partial pressures are, for example, CC24°0, I Tot+r # 02;
Adjust to 0.04 Tobr. Then 13
．． By applying a high frequency voltage of 100OV P-P at 56 MHz, a DC bias of -800V was applied to the electrode 2.
is applied, CC44 in the channel 1 decomposes into ions and reacts directionally with the polycrystalline silicon film exposed from the resist/turns of the object to be etched 3. The crystalline silicon film is etched. This dry etching method allows for thorough side etching, and is therefore suitable for microfabrication and is frequently used in the fabrication of recent VLSIs.

However, in the conventional dry etching method described above, the following problems arise as LSIs become smaller. That is, if dust adheres to the polycrystalline silicon film of the object to be etched before or during etching, the lower part of the polycrystalline silicon under the dust is not etched and remains, resulting in a defect. Components of the dust include fragments of resist on or around the object to be etched 3, polycrystalline silicon, a reaction material between the resist and the reactive gas (CCt4 ions), silicon debris from the wafer, and many others. In addition, the adhesion of dust to the object to be etched 3 is caused by the air pressure during vacuuming, and the adhesion of dust to the object to be etched 3.
1 Adhering to the inner wall surface is caused by falling of the polycrystalline silicon film of the object to be etched 3 during etching, or by mechanical contact when the object to be etched 3 is placed on the electrode 2. There are various forms such as things. This kind of garbage is more than a few micrometers in size every winter.

For this reason, the dust adhering to the inner wall surface of the chamber 1, the top of the electrode 2, etc. of the reactive ion etching apparatus may be cleaned and removed.

However, cleaning requires disassembling the device, and even after cleaning, it is necessary to dry the device and reset the etching conditions, and one cleaning takes about half a day to a day. In addition, reactants adhere to the inner walls of the chambers 1 each time they are etched, so it is necessary to clean them every time to minimize the amount of dust. It also decreases drastically.

The cleaning frequency is usually determined by taking into account the throughput of the device and the amount of dust, but the reduction in yield due to dust cannot be avoided, and this is a major problem in reducing the yield of LSI.

The above-mentioned problems are not limited to the method using an active ion etching device, but also occur when etching is performed using a dry etching device such as a base etching device or an ion etching device.

[Purpose of the invention]

The present invention aims to provide a dry etching method that can eliminate LSI defects caused by dust adhering to the surface of an object to be etched, such as a silicon wafer, and can contribute to improved yield and throughput.

[Summary of the invention]

The present invention prevents dust from adhering to the surface of the object to be etched during dry etching by surrounding the object to be etched placed in a chamber with a cover having fine holes through which gas can pass. The main purpose of this method is to avoid etching defects of the object to be etched.

[Embodiments of the invention]

Next, an example in which the present invention is applied to a dry etching method using a reactive ion etching apparatus will be described with reference to FIGS. 2 and 3.

First, as shown in FIG. 2, the object to be etched 3 is placed on the electrode 2 in the chamber, and then the cover 1 is placed on the electrode 2 so as to surround the object to be etched 3. installed. The object to be etched 3 is, for example, a phosphorous-doped polycrystalline silicon film deposited on a silicon wafer via an oxide film, and a desired resist or turn is further formed on the surface of the polycrystalline silicon film. . Moreover, the above-mentioned cover J is the third
As shown in the figure, there is a cylindrical support base 9 made of an insulating material such as At2o, 5to2, etc., with a stainless steel net 8 stretched over the top opening, and a plurality of fine holes fixed to the top surface of the support base 9. The porous filter 10 has a porous filter 10. Note that the porous filter is made of quartz glass At203.
Examples include sintered powders, carbon molded products, and the like. However, if the covering is used like a triode grid to actively change the electric field, a porous filter with multiple fine holes perforated in metal foil such as AA, Cu, or Au can be used. Can be used. The diameter of the micropores is desirably set to 11 m or less.

Next, a vacuum pump connected to the bottom of the chamber via a butterfly valve is operated to remove the air from the chamber, and CCT4 gas and 02 gas are introduced from the gas inlet, and the partial pressure of each is set to, for example, CCl2:0. ITorr+02:0.
04 Torr.

Next, 13.56 MHz 100OV p-p
By applying a high frequency voltage, a DC bias of -800V is applied to the electrode 2, and the CCl2 in the chamber is decomposed into ions, and the porous filter with the cover L... It reacts with the polycrystalline silicon film exposed from the resist pattern of the object to be etched 3 . . . in the same type 7 .

According to the above method, even if dust falls onto the surface of the object to be etched 3 during vacuuming or etching, the object to be etched 3 is surrounded by the cover 7. Therefore, it is possible to prevent dust from adhering to the surface of the cutting/etching body 3. Also, covered! ... has a structure in which a porous filter o is fixed on the net 8 of the support stand 9, as shown in Fig. 3, so that the ionized c inside the chamber is
The ct gas can freely flow through the filter o and the mesh body 8 into the same kind l..., and as a result, the etched body 3...
...(7) L/ sis) /? The polycrystalline silicon film exposed from the turns can be etched without any problem. Furthermore, the cover l... is replaceable, and if you use a cleaned cover each time you etch, you don't have to worry about dirt getting into the cover from the top surface. Moreover, since the cover 7 is extremely small compared to the chamber of the active ion etching apparatus, cleaning is also extremely easy.

Therefore, when etching the polycrystalline silicon film exposed from the resist 7) turn of the object to be etched,
By surrounding the object 3 to be etched with the cover 7, it is possible to prevent etching defects caused by dust adhering to the surface of the object 3 to be etched, and also to facilitate cleaning and maintenance of the apparatus. Become. As a result, LSIs can be manufactured with high yield, and the nullput of the reactive ion etching apparatus can also be improved.

In the above embodiment, the object to be etched was placed on the electrode, and the cover was placed on the electrode so as to surround the object to be etched, but the object to be etched 3 was placed on the chuck 11 as shown in FIG. However, dry etching may be performed by placing a cover 7i on the chuck 1 so as to surround the object 3 to be etched so that the object 3 to be etched is completely surrounded by the chuck 11 and the cover J. In this way, the object to be etched 3
If the polycrystalline silicon film of the object to be etched is completely surrounded by the chuck 11 and the cover 7, and the chuck and cover are cleaned each time the etching is performed, the dust on the electrode 2 will not adhere to the surface of the object to be etched 3. This can be completely prevented.

Although the structure shown in FIG. 3 was used as the cover in the above embodiment, the structure is not limited thereto. For example, as shown in FIG. A cover 7f consisting of a ring-shaped presser member 13 fixed to the ring-shaped holding member 13 on which a net body 12 for holding the filter 10f is stretched may also be used. Further, as shown in FIG. 6, a porous cover made of an insulating material such as quartz glass or At203 and having a hollow shape with only the bottom open may be used. Furthermore, as shown in FIG. 7, the porous filter IQ and the ring-shaped holding member 13' are made of a conductive material, and a tongue piece 14 is made to protrude from a part thereof, and a wiring 15 is connected to this tongue piece 14. A holding member 13' is attached to the wiring 15 to form a cover.
The potential of the porous filter 10' may be fixed.

In the above embodiment, a method was described in which a polycrystalline silicon film was etched using an object to be etched in which a polycrystalline silicon film was deposited on a silicon wafer through an oxide film. 5 on top
A silicon wafer or a SiO□ film may be etched using an object to be etched with an i02 film deposited thereon.

The present invention is not limited to dry etching using a reactive ion etching apparatus as in the above embodiment, but also applies to dry etching using a sputter etching apparatus, an ion etching apparatus, and even a so-called isotropic plasma etching apparatus. I can demonstrate it.

〔Effect of the invention〕

As detailed above, according to the present invention, etching defects can be avoided by preventing dust from adhering to the surface of the object to be etched during vacuuming and etching during dry etching. It has remarkable effects such as being able to be manufactured.

[Brief explanation of drawings]

Figure 1: Schematic diagram of beam active ion etching device;
FIG. 2 is a schematic diagram of the vicinity of the electrodes of a reactive ion etching device used in an embodiment of the present invention, FIG. 3 is an exploded perspective view of a cover used in the device of FIG. 2, and FIG. 5 to 7 are perspective views showing other forms of the cover used in the dry etching method of the present invention. 1...Chamber, 2...Electrode, 3...Etched object, 5...Vacuum number? 6... gas inlet;
Z...cover, 9...support stand, 10.10'...porous filter, 13, 13'...pressing member, 15...
·wiring. Applicant's agent: Sehiko Suzue Figure 1 Figure 4 Figure 5 123- Figure 6

Claims (9)

[Claims] (1) A dry etching method for etching an object to be etched placed in a chamber, characterized in that the object to be etched is surrounded by a cover having micropores through which gas can pass. (2) A dry etching method according to claim 1, characterized in that the object to be etched is etched by a step etching method. (3) The dry etching method according to claim 1, wherein the object to be etched is etched by an ion etching method. (4) The dry etching method according to claim 1, characterized in that the object to be etched is etched by a reactive ion etching method. (5) Claim 1, characterized in that the plurality of micropores opened in the cover have a diameter of 1 μm or less.
Dry etching method described in section. (6) The dry etching method according to claim 1, wherein the cover is composed of a porous filter having micropores through which gas can pass, and a support portion that supports the filter. (7) The dry etching method according to claim 1, wherein a part of the cover is made of a conductor. (8) The dry etching method according to claim 7, characterized in that a wiring is connected to the conductor portion of the cover, and the potential of the conductor portion is controlled from the outside. (9) The dry etching method according to claim 1, wherein the object to be etched is a wafer. α1 The dry etching method according to claim 1, wherein the object to be etched is a wafer with a film formed thereon.