JP2949731B2 - Method for manufacturing semiconductor device - Google Patents

Description

The present invention relates to a divergent magnetic field type electron cyclotron resonance (EC).
R) The present invention relates to a method for manufacturing a semiconductor device in which a substrate is processed using a plasma apparatus, and more particularly to a method for manufacturing a semiconductor device which enables anisotropic etching with little damage to a substrate to be processed.

[Summary of the Invention]

The present invention relates to a diverging magnetic field type electron cyclotron resonance (EC).
R) In a method of manufacturing a semiconductor device in which a substrate is processed using a plasma apparatus, an inert gas is introduced into a plasma generation chamber and a gas containing bromine is introduced into a reaction chamber to form a high melting point metal on a substrate to be processed. By performing the etching of the polycide film, anisotropic etching that causes less damage to the substrate to be processed is performed.

[Conventional technology]

2. Description of the Related Art Conventionally, semiconductor integrated circuits have been miniaturized together with high integration, and higher functions, higher speeds, and higher reliability have been required. In order to realize a high-speed semiconductor device, it is essential to reduce the resistance of various wirings such as gate wirings, and it is useful to use a refractory metal silicide as a material suitable for this.

There is known a polycide film in which an impurity-doped polycrystalline silicon layer and a high melting point metal silicide are laminated for the purpose of guaranteeing compatibility with a conventional process, particularly a gate process. In this technique, polycrystalline silicon is disposed at an interface with a gate insulating film, which most easily affects device characteristics and reliability, and a high-melting metal silicide layer thereon is used to reduce resistance.

By the way, in the manufacture of a semiconductor device having a high degree of integration, anisotropic etching is useful for realizing a fine pattern.

When performing anisotropic etching on the above-mentioned polycide film,
It is difficult to control the etching. That is, in the etching of the polycide film, the lower polycrystalline silicon layer is etched faster than the upper refractory metal silicide layer due to the difference in vapor pressure of the generated halogen compound, or the polycrystalline silicon grains are etched. This is because undercuts, constrictions, and the like are likely to occur in the pattern due to the reason that halogens accumulate in the field to lower the anisotropy.

Since the formation of the gate wiring requires a high dimensional accuracy particularly in the self-alignment technique because it directly affects the channel length, it is necessary to perform etching so that the above-mentioned pattern abnormality does not occur. Therefore, in order to keep the difference in etching rate between the upper and lower layers of the polycide film small and to achieve anisotropic etching, Freon 113 (C ₂ Cl
Freon-based gases such as ₃ F ₃ ), Freon 114 (C ² Cl ₂ F ₄ ), and Freon 115 (C ₂ ClF ₅ ) are used. This gas is widely used because chlorine and fluorine in the molecule each contribute to etching effectively, and furthermore, highly anisotropic etching can be performed while protecting the side wall by depositing a carbon-based polymer.

However, the carbon-based polymer not only deposits on the etched cross section as a sidewall protective film, but also deposits on the inner wall of the etching apparatus, causing contamination. In addition, when an etching gas containing carbon atoms is used, there is a problem that the selectivity to a base such as silicon oxide is reduced.

Therefore, as an etching technique using an etching gas that does not contain carbon atoms, a microwave down stream asher is described in Proceedings of the Dry Process Symposium (1988), pp. 58-63, lecture number II-5. A technique for etching polycrystalline silicon with HBr gas using a connected RIE (reactive ion etching) apparatus is disclosed.

[Problems to be solved by the invention]

The etching in the RIE apparatus described in the above-mentioned document is performed by an etching species having a relatively high energy. For example, when an attempt is made to form a gate wiring made of polycrystalline silicon, the selectivity to silicon oxide as a gate oxide film is increased. And damage is likely to occur. In particular, the gate electrode width is reduced to 0.35 to 0.5 μm by submicron processing technology. With this miniaturization, the thickness of the gate oxide film has been reduced to 80 to 120 mm, and the junction depth has been reduced to 0.1 to 0.15 μm. Is removed, and there is a possibility that the bonding may be deteriorated or broken.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method of manufacturing a semiconductor device which enables a high-melting-point metal polycide film on a substrate to be etched while maintaining high anisotropy.

[Means for solving the problem]

In order to achieve the above object, a method for manufacturing a semiconductor device according to the present invention includes a plasma generation chamber for generating plasma by electron cyclotron resonance, and a reaction chamber in which a substrate to be processed for irradiating the generated plasma is disposed. Using a plasma processing apparatus, an inert gas is introduced into the plasma generation chamber, and a gas containing bromine is introduced into the reaction chamber from a tip having a large number of gas outlets of an annular pipe. The etching of the refractory metal polycide is performed.

[Action]

The divergent magnetic field type ECR plasma device used in the method of the present invention is to extract a plasma flow from a plasma generation chamber to a reaction chamber by a magnetic field gradient under a high vacuum,
ECR plasma equipment can perform etching with low scattering and excellent directionality.
3.1 eV) can be generated efficiently in an energy range that can be selectively cut. For example, polycrystalline silicon and silicon oxide (Si-O bond energy is 8.4 e
Etching can be performed by setting the selectivity of V) large.

This divergent magnetic field type ECR plasma device is characterized by the fact that the plasma flow spreads along the magnetic field as it progresses in the divergent magnetic field, so that the processing state tends to be uneven with the peripheral part at the center of the substrate to be processed. The problem is solved by introducing an inert gas into the production chamber and introducing a gas containing bromine into the reaction chamber.

According to the method of the present invention, first, electrons resonately absorb microwave energy in a plasma generation chamber where the ECR condition is achieved, and the electrons collide with inert gas molecules to generate plasma. When the inert gas molecule is, for example, argon,
In the plasma, there are metastable argon radicals which are other neutral species of argon ions and electrons. The metastable argon radical has a relatively long life and does not deactivate even if it is drawn from the plasma generation chamber into the reaction chamber by a magnetic field gradient. Therefore, the argon radicals collide with a gas containing bromine in the vicinity of the substrate to be treated, and are dissociated to generate bromine radicals. The bromine radical is
It adheres to the surface of the substrate to be processed, especially the surface of the polycide film, where it receives the kinetic energy of argon ions and uses it for the reaction energy of etching.

As is apparent from the above process, the etching according to the method of the present invention essentially proceeds only on the surface irradiated with the inert gas ions, so that anisotropic etching can be achieved without particularly forming a sidewall protective film. In addition, it is not necessary to anticipate an increase in the width of the gate electrode due to the sidewall protection film at the time of designing, so that the dimensional accuracy is also improved.

〔Example〕

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

As shown in FIG. 1, the divergent magnetic field type ECR plasma device used in the method of the present invention has a rectangular waveguide 1 for guiding microwaves generated by a microwave source (not shown).
A plasma generation chamber 3 connected to the rectangular waveguide 1 via a microwave introduction window 2 made of a quartz glass plate or the like to generate plasma using electron cyclotron resonance;
It has a plasma extraction window 4 for extracting plasma generated in the plasma generation chamber 3, a susceptor 6 for holding a substrate 5 to be processed such as a wafer, a reaction chamber 7 in which predetermined processing is performed, and a rectangular waveguide 1. A magnetic coil 8 disposed so as to go around the plasma generation chamber 3 from one end, a primary gas introduction system 9 for introducing gas into the plasma generation chamber 3, and a gas into the reaction chamber 7 The exhaust gas system (not shown) connected from the reaction chamber 7 in the direction of arrow A in FIG.

The outer wall of the plasma generation chamber 3 has a double structure, and a rise in temperature due to plasma generation is suppressed by introducing cold water through the cooling water pipe 11. A high-frequency power supply for applying a high-frequency bias to the substrate 5 to be processed and the susceptor 6 for the purpose of precisely controlling ion energy.
Twelve are also provided.

In the method of the present invention, an inert gas is supplied from the primary gas introduction system 9;
A gas containing bromine is introduced from the secondary gas introduction system 10.

Here, argon (Ar), krypton (Kr), xenon (Xe), or the like is used as the inert gas.

As a gas containing bromine, hydrogen bromide gas (HB
r), bromine gas (Br ₂ ), or a mixture of these with an appropriate diluent gas is used. Since the gas containing bromine needs to be distributed as uniformly as possible in the vicinity of the substrate to be treated, the secondary gas introduction system 10 is an annular pipe having a large number of gas outlets at its tip. Used.

Using such an ECR plasma apparatus, a refractory metal polycide film in which a polycrystalline silicon layer and tungsten silicide were stacked was actually etched. Here, the degree of vacuum in the apparatus is set to 5 × 10 ⁻³ Torr, and a microwave having a frequency of 2.45 GHz and power of 800 W is introduced from the rectangular waveguide 1 into the plasma generation chamber 3 through the microwave introduction window 2. A magnetic field with a magnetic flux density of 875 Gauss is formed by the magnetic coil 8 and the ECR
The conditions were achieved. In this state, Ar gas was introduced from the primary gas introduction system 9 at a flow rate of 40 SCCM, and HBr gas was introduced from the secondary gas introduction system 10 at a flow rate of 20 SCCM, and etching was performed by applying a high frequency bias of 300 W. An extremely anisotropic pattern without constriction or undercut was obtained.

〔The invention's effect〕

As is clear from the above description, in the method of the present invention, in the divergent magnetic field type ECR plasma device, the refractory metal polycide film on the substrate to be processed is etched so that the damage is small and the high anisotropy is realized. Is done. Further, since etching species involved in actual etching are generated in the vicinity of the substrate to be processed, and the gas containing bromine is uniformly distributed in the vicinity of the substrate to be processed, the uniformity of the process is also high.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an ECR plasma apparatus used in the method of the present invention. 3 ... plasma generation chamber, 5 ... substrate to be treated, 7 ... reaction chamber, 9 ... primary gas introduction system, 10 ... secondary gas introduction system.

Claims (1)

(57) [Claims] A plasma processing apparatus having a plasma generation chamber for generating plasma by electron cyclotron resonance and a reaction chamber in which a substrate to be irradiated with the generated plasma is disposed, wherein the plasma generation chamber has With the introduction of active gas,
Etching a refractory metal polycide film on a substrate to be processed while introducing a gas containing bromine into the reaction chamber from a tip having a large number of gas outlets of an annular pipe. .