JPS6116524A - Dry etching device - Google Patents

Abstract

PURPOSE:To prevent an irregularity from happening on an etching surface while improving the sectional shape of etching pattern by a method wherein, within the inner surface of a device coming into contact with discharge plasma, at least those surface exposed to violent ion shock is coated with silicon nitride. CONSTITUTION:Within a parallel flat type reacting sputter etching device, a target coating member 2 comprising silicon nitride and a ceramics opposite 6 sheet comprising silicon nitride are arranged on a target electrode 1 in a vacuum chamber 7. Then e.g. etching specimens 3 with silicon parts are arranged closely on the target coating member 2. Next silicon tetrachloride gas is jetted from an etching gas introducing and jetting tube 4 to adjust the interval of plasma discharge produced by means of impressing high frequency voltage from the power supply 5 thereof. Then after etching Si with specific thickness, the high frequency power supply is stopped to pick up the specimens 3. Through these procedures, an etching surface may avoid any polluted layers such as carbon while preventing an irregularity from happening to be provided with highly smooth and fine pattern.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a parallel plate type dry etching apparatus.

(Prior Art) Reactive sputter etching or reactive ion etching is an established technology in the field of semiconductor manufacturing, with a number of orientations that replace aqueous etching. It is known that the etching characteristics can be improved by a combination of an electrode coating member and an etching introduction gas.

Conventionally, for reactive sputter etching of silicon materials, quartz (8i02) or surface alumina coating (A40s) of aluminum metal is used as the target electrode coating member, and CCl5Fy CC4 is used as the etching introduction gas.
s CF4 + Ox, SiF+, SF
a + C1t tcc4 + Cl2, etc. have been used. Here, active ions in the plasma generated by applying a high-frequency electric field are accelerated in the ion sheath zone near the surface of the canned electrode and are incident perpendicularly to the sample to be etched.The sputtering effect due to physical ion bombardment and the chemical reaction generated in the discharge plasma Etching progresses through a chemical reaction in which reactive neutral molecules react on the surface of the material to be etched to produce volatile products.

(Problems with the prior art) The reactive sputter etching technique described above also applies to polycrystalline silicon substrates with a thickness of 0.5 microns or less and silicon substrates with a depth of about 0.5 to 1 micron, which have been used in conventional semiconductor devices. With this etching, we were able to perform anisotropic etching with fewer undercuts without causing any problems, and we were able to respond to these miniaturizations. In recent years, research and development of semiconductor elements with new miniaturized structures has been actively conducted, and the dependence of the electrical characteristics of the elements on etching processing technology has increased. In particular, as a fine device isolation method, there is a so-called trench isolation method that uses deep trenches that make full use of reactive sputter etender technology. In addition, there is another device isolation method in which deep trenches are formed in a silicon substrate, the trench sidewalls are covered with an insulating film, and then silicon crystalline silicon is buried in the trenches by selective epitaxial growth. In any of these cases, the etching shape of the fine pattern when trenching deep trenches in the silicon substrate is vertical, the etched surface remains mirror-like without becoming rough, and the silicon surface is not contaminated by impurities. However, as mentioned above, it is necessary to use quartz (Sift) as a covering member for the electrode of the etching device in the etching process of silicon substrates for separating microscopic elements.
CCI, F,
When CCl4+ C1t gas is used, silicon substrate (
When the etching depth of 8i) was about 0.5 to 1 micron, the vertical shape was maintained, but when the etching depth became deeper than 1.5 microns, the middle part of the pattern side wall became constricted and rounded, and the desired rectangular shape was obtained. In addition, the etched surface becomes rough due to redeposition of reaction products, and is contaminated with impurity atoms such as multiple elements, which reduces the manufacturing yield of integrated circuits. Therefore, when using a quartz target covering member,
It was necessary to remove the contaminant layer such as C and F after etching from the silicon surface by wet etching, and to perform a surface recovery treatment using a thermal oxidation method or the like.

(Object of the Invention) The present invention prevents etching surface roughness caused by using a conventional quartz target electrode coating member, etching surface contamination by impurity atoms, constriction of etching pattern sidewalls, etc. This was developed for the purpose of being usable with good reproducibility in fine element separation that requires trenching. (Structure of the Invention) The dry etching apparatus of the present invention places the object to be etched closely on the electrode. In net retrieving equipment,
The 0-discharge method is characterized in that at least the surface of the inner surface of the device that is in contact with the discharge plasma and is subject to strong ion bombardment is coated with nitride, and the shape of the electrodes does not matter.

(Principle of the Invention) The constituent materials of the surface coating member must have spatter resistance and be a substance that does not become a source of contamination.
The effect is remarkable when using silicon tetrachloride (stcZ) as the etching gas, which is the most suitable stimulant, especially when the target material for etching is silicon (8i).

The surface roughness, which has been a problem in the past, is due to the fact that 8i01 is produced by the reaction between moisture and oxygen generated from the surface of the device during etching and the etching gas SiC14, which becomes an etching mask. by. The purpose of the present invention is to prevent roughness of the etching surface and improve the cross-sectional shape of the etching pattern by cutting off the supply of oxygen from the surface of the device.Also, the purpose of the present invention is to prevent the etching surface from becoming rough and improve the cross-sectional shape of the etching pattern. Since it does not contain silicon, there is no need to perform recovery treatment on the silicon surface after removing the contaminant layer after trench etching, which simplifies the process.

(Example) ``A typical embodiment of the present invention will be explained using the drawings.

FIG. 1 schematically shows a parallel plate type reactive sputter etching apparatus. The apparatus includes a target coating member 2 made of a silicon nitride ceramic material and a silicon nitride material ceramic on a target electrode lO in a vacuum chamber 7. The ceramic facing plate 6 is arranged first. First, an etching sample 3 having a silicon portion is closely placed on the silicon nitride ceramic target coating member. Next, remove silicon tetrachloride gas (8i
C4) Adjust the plasma discharge interval generated by applying a high-frequency electric field 5 to the k-blowout Q and a predetermined thickness of 8i? :
After etching, the high-frequency electric field is stopped and the sample is taken out. In the embodiment of the present invention, an etching device having two disc-shaped electrodes has been described, but the present invention uses a polyhedral electrode, which is in almost the same situation as this example. Reactive ion beam etching equipment with an independent ion source 1
It is effective even when used under a relatively high pressure of 110 Torr or more, and there are no particular limitations on the discharge method or electrode shape.

Further, in this embodiment, plates made of silicon nitride were used for the target and the opposing plate, but it is sufficient that at least the surface is covered with silicon nitride.

Further, in this embodiment, the gas blowing pipe 4 was made of stainless steel and was used as it was, but if its surface was also coated with silicon nitride, contamination etc. could be further reduced.

Furthermore, in this example, a silicon nitride disk was used as target 2, but if you want to improve heat dissipation, it is recommended to use a cutout target with a cutout area for placing sample 3 (invention (Effect of C) By performing sputter etching using an etching gas of silicon tetrachloride on a counter plate made of the same material as the silicon nitride ceramic target electrode coating member that does not contain atoms that can be a source of impurity contamination, contamination such as C can be removed. A layer-free etched surface was obtained. In addition, it is possible to prevent roughness of the etched surface caused by re-adhesion of 8i01, etc., and to obtain a smooth etched surface with fine vertical patterns, which solves the problems associated with conventional deep trenching of silicon. It has the advantage of

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Claims (1)

[Claims] A dry etching device in which an object to be etched is placed closely on an electrode, characterized in that, of the inner surface of the device facing the discharge plasma, at least the surface that receives strong ion bombardment is coated with silicon nitride. Device.