JPH0760815B2 - Dry etching method - Google Patents

Description

The present invention relates to a parallel plate type dry etching method.

(Prior Art) Reactive sputter etching or reactive ion etching is a technique established in the field of semiconductor manufacturing, because it has various advantages that are different from aqueous solution etching. It is known that this etching method obtains an improvement in etching characteristics by combining a target electrode coating member suitable for an etching target substance and an etching introduction gas.

Conventionally, for reactive sputter etching of silicon material, quartz (SiO ₂ ) or aluminum alumina surface alumina coating (Al ₂ O ₃ ) material is used for the target electrode coating member, and CCl ₃ F, CCl ₄ , CF ₄ + O ₂ , SiF ₄ ,
SF ₆ + Cl ₂ , CCl ₄ + Cl _2, 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 cathode electrode and are vertically incident on the sample to be etched.The sputtering effect due to physical ion bombardment and the chemistry generated in the discharge plasma. Etching proceeds by a chemical reaction in which chemically active neutral molecules react on the surface of the material to be etched to generate a volatile product.

(Problems of Prior Art) The above reactive sputter etching technique has also been used for conventional semiconductor devices. The etching of polycrystalline silicon of 0.5 micron or less or a silicon substrate having a depth of about 0.5 to 1 micron did not cause many problems, and anisotropic etching with less undercut was made possible, and it was possible to cope with such miniaturization. 2. Description of the Related Art In recent years, research and development of miniaturized semiconductor devices having a new structure have been actively carried out, and the dependence of electrical characteristics of devices on etching processing technology has been increasing. In particular, a fine element isolation method includes so-called trench isolation using a deep groove that makes maximum use of the reactive sputter etching technique. In addition, after forming a deep groove in the silicon substrate,
There is also an element isolation method in which the side wall of the groove is covered with an insulating film, and then crystalline silicon is buried in the groove by selective epitaxial growth. In any of these cases, the etching shape of the fine pattern at the time of deep trenching of the silicon substrate is vertical, and the etching surface is not roughened and maintains a mirror surface,
It is necessary that the silicon surface is not contaminated by impurities. However, when quartz (SiO ₂ ) is used for the electrode coating member of the etching apparatus and CCl ₃ F, CCl ₄ + Cl ₂ gas is used as the etching introduction gas for the etching process of the silicon substrate for separating these fine elements as described above. ,
The vertical shape was maintained when the etching depth of the silicon substrate (Si) was about 0.5 to 1 micron, but when it was deeper than 1.5 micron, the middle part of the pattern sidewall showed a constricted shape and the desired rectangular shape was obtained. I couldn't do it. Further, the redeposition of the reaction product causes the etching surface to be roughened or contaminated with impurity atoms such as photons, which causes a reduction in the manufacturing yield of the integrated circuit.

Therefore, when a quartz target coating member is used,
It was necessary to remove the dirty layer such as C and F after the sputter etching from the silicon surface by using wet etching, or to perform the surface recovery treatment by using a thermal oxidation method or the like.

(Object of the Invention) The present invention prevents roughness of an etching surface caused by using a conventional quartz target electrode coating member, etching surface contamination due to impurity atoms, constriction of a side wall of an etching pattern, etc., and deep silicon (Si) The purpose of the invention is to enable it to be used with good reproducibility for fine element separation or the like that requires grooving.

(Structure of the Invention) The dry etching method of the present invention is a dry etching method in which an object to be etched is closely arranged on an electrode,
Among the inner surfaces of the apparatus that come into contact with the discharge plasma, at least the surface that is subjected to strong ion bombardment is coated with silicon nitride, and silicon tetrachloride is used as an etching introduction gas. The discharge method and the electrode shape do not matter.

(Principle of the Invention) The constituent material of the surface coating member is required to be a substance that is resistant to spatter and does not become a pollution source. Among them, silicon nitride is
It is the most suitable substance, and its effect is particularly remarkable when silicon tetrachloride (SiCl ₄ ) is used as an etching gas when the etching target substance is silicon (Si).

Conventionally, the surface roughness that has been a problem is due to the fact that SiO ₂ is generated by the reaction between moisture and oxygen generated from the surface of the device during etching and SiCl ₄ which is an etching gas, and it becomes an etching mask. . The present invention aims to prevent the roughness of the etching surface by cutting off the supply of oxygen from the surface of the apparatus and to improve the cross-sectional shape of the etching pattern. In addition, since the covering member and the etching-introduced gas body do not include an impurity contamination source, especially after the trench etching,
It is not necessary to remove the contaminated layer or to recover the silicon surface, and the process can be simplified.

(Example) A typical example of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram showing a parallel plate type reactive sputter etching apparatus.
A target coating member 2 made of a ceramic of silicon nitride material and a ceramic facing plate 6 of a silicon nitride material are disposed on the above. First, an etching sample 3 having a silicon portion is closely placed on the target coating member of the silicon nitride ceramic. Next, silicon tetrachloride gas (SiCl ₄ ) is blown out from the etching gas introduction blow-out pipe 4 made of stainless steel, and a high frequency electric field 5 is applied to adjust a plasma discharge interval generated. Then, after etching Si of a predetermined thickness, the high frequency electric field is stopped and the sample is taken out.

In the embodiment of the present invention, the etching apparatus having two disk-shaped electrodes has been described. However, the present invention is almost the same as the etching apparatus having the polyhedral electrode and the reaction having the ion source independently. Ion beam etching equipment
It is also effective when used under a relatively high pressure of 10 ^-3 Torr or more, and does not particularly limit the discharge method or the electrode shape.

Further, in the present embodiment, a plate in which the target and the facing plate are all made of silicon nitride is used, but at least the surface may be covered with silicon nitride.

Further, in this embodiment, the gas blow-out pipe 4 is made of stainless steel as it is, but if the surface of the gas blow-out pipe 4 is coated with silicon nitride, contamination and the like can be further reduced.

Further, in this embodiment, the target 2 is a silicon nitride disk as it is, but a cutout target in which a portion on which the sample 3 is placed is cut out may be used when heat dissipation is desired to be improved.

(Effect of the Invention) Contamination of C or the like is caused by performing sputter etching using an etching introduction gas of silicon tetrachloride on a counter plate made of the same material as the target electrode coating member of silicon nitride ceramics that does not contain atoms that are sources of impurity contamination. A layerless etched surface was obtained. In addition, it can prevent the roughness of the etching surface due to redeposition of SiO _2, etc., and can solve the problems in the conventional deep trenching of silicon such as obtaining a smooth etching surface with a fine vertical pattern. Have the advantage of

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view of an apparatus used in the dry etching method of the present invention.

Claims (1)

[Claims] 1. An object to be etched is placed in close contact with an electrode, and at least a surface of the inner surface of the apparatus facing the discharge plasma, which is subjected to a strong ion bombardment, is covered with silicon nitride, and tetrachloride is used as an etching introduction gas. A dry etching method characterized by using silicon.