JPH02225681A - Method for vapor-phase etching - Google Patents

Abstract

PURPOSE:To efficiently carry out anisotropic etching in a vapor phase without damaging the surface of a substrate to be etched by impressing a high-frequency or DC electric field on a reactive gas activated by utilizing cyclotron resonance in the direction vertical to the substrate. CONSTITUTION:The reaction space 1 in a stainless steel vessel 1' in which the substrate 10 heated to a specified temp. by a halogen lamp 7 is arranged and the resonance space 2 in a quartz tube 29 connected to the reaction space 1 are evacuated to a specified pressure by an evacuating system 11 including a vacuum pump 9. An inert gas such as Ar or a nonproductive gas is introduced into the resonance space 2, and cyclotron resonance is produced by the microwave from a microwave oscillator 3 and the magnetic fields of air-core coils 5 and 5'. The formed electron and the excited gas 21 are discharged into the reaction space 1. An etching gaseous reactant 22 such as fluorocarbon capable of generating at least halogen element is introduced into the reaction space 1 and excited. Furthermore, a high-frequency or DC electric field vertical to the substrate 10 is impressed by the reticular electrodes 20 and 20' arranged at the upper and lower parts of the reaction space 1. As a result, anisotropic etching is applied selectively on the surface to be etched or over the whole surface of the substrate 10.

Description

Detailed Description of the Invention Field of Application of the Invention 1 The present invention uses electron cyclotron resonance to activate or decompose a reactive gas for etching, and further applies a high frequency or direct current electric field in a direction perpendicular to the surface of the substrate to be etched. This invention relates to a vapor phase etching method in which a substrate or a material to be etched on a substrate is anisotropically etched by simultaneously adding .

rPrior Art j A plasma etching method (glow discharge etching method) in which a reactive gas is activated by a high frequency or a direct current electric field is known as an etching technique (vapor phase chemical removal method) using a gas phase etching reaction.

However, in the anisotropic etching method using such glow discharge, the anisotropy of the film is not sufficient compared to the progress of VLSI, and there has been a need to further improve the accuracy of the anisotropic etching. .

On the other hand, an etching method using electron cyclotron resonance is known. However, although such a method allows etching of the entire film, it is insufficient for selective anisotropic etching. This is because the reactive gas moves parallel to the substrate surface due to resonance, making it almost impossible to form a recess.In addition, when creating resonance, for example, argon is used as the resonant atom, and the frequency is set to 2.45 GH,z. This requires a strong magnetic field of 875 Gauss. For this reason, the air-core coil for magnetic field action tends to be large, and the excited gas cannot be spread over a large area.As a result, it has a width or diameter of submicron (less than 1μ, for example 0.2μ)
Hole-like etching with a depth of 2 to 4 microns was not possible at all.

Means for Solving Problems j In order to solve these problems, the present invention uses cyclotron resonance to activate the reactive gas.

Therefore, activation, decomposition, or reaction of the reactive gas for etching can be carried out extremely efficiently using electrons or activated gas. This activated gas is introduced into the atmosphere where the glow discharge is occurring, and the active state is maintained even after the resonance energy has ceased to resonate, and this electric field is made perpendicular to the substrate, giving it directionality. Alternatively, the material to be etched on the substrate is anisotropically etched, and the upper part of the substrate is capable of having sufficiently deep recesses even at the submicron level.

Then, by this plasma glow discharge technique, the activated gas is spread over a wide space, and therefore, a large amount of the substrate or the material to be etched on the substrate can be etched with high precision anisotropically over a wide area. It becomes possible to perform the process uniformly without any variation.

In the present invention, a DC power source was used as the glow discharge power source. However, even with high-frequency glow discharge, the excited state of the excited reactive gas can be maintained, and anisotropic etching can be performed by the self-bias created at the same time.

Furthermore, cyclotron resonance uses an inert gas or a non-product gas (a gas that itself produces only a gas when decomposed or reacted). Argon is a typical inert gas. However, helinium, neon, and krypton may also be used.

As the non-product reactive gas for etching, CPI is used.

CFtHt=CFHy, CFsH, CC1a, nitrogen fluoride (Nh, NzFi), hydrogen fluoride ()IP), fluorine (p
n), hydrogen chloride (HCI), chlorine (Clg), or a mixture of these with a carrier gas or oxygen is typical.

These non-product etching gases are activated by cyclotron resonance, mixed with the product gas in a reaction space outside this resonance region, and the excitation energy is transferred to the product gas, which causes the etching gas to undergo extremely large electromagnetic Because of the energy it receives, it can be activated or decomposed by approximately 100x, and is accelerated by the electric field for anisotropic etching and impinges on the substrate at a predetermined angle, generally perpendicular to the substrate, to cause an etching reaction. Furthermore, room temperature ~ 30
By heating the substrate at a temperature of 0° C., it is possible to anisotropically etch the substrate or the material to be etched on the substrate.

The present invention will be illustrated below with reference to Examples.

Implementation N1 FIG. 1 shows an outline of the cyclotron resonance type plasma etching apparatus of the present invention.

In the drawing, a stainless steel container (l゛) has a lid (1") and constitutes a reaction space (1). This container (1'
), the board (10) is installed on the board holder (10°) on the top, and the halogen lamp heater (7) is installed on the back side of the lid (1°). ) is opened upwards to heat the substrate by irradiating infrared rays through a quartz window (19).Furthermore, there is one mesh electrode (20') on the back side of this substrate and one at the bottom of the container (1"). A 13.56 M1 (z or direct current) electric field is applied thereto from a high frequency or direct current power source (6). It is located.

In addition, the non-product gas is extracted from the doping system (13) (18)
It is then supplied to the resonant space (2) made of a quartz tube (29). This resonant space has an air-core coil (5) outside it.

(5°) and apply a magnetic field. At the same time, the microwave oscillator (3) passes through the analyzer (4), e.g.
GH2 microwaves are supplied to the resonance space (2).

In this space, when the non-product gas is argon, a magnetic field (for example, 875 Gauss) determined by its mass and frequency is applied by an air-core coil in order to cause resonance.

For this reason, the argon gas is excited and resonates at the same time as it is binned by the magnetic field, and after being sufficiently excited, the reaction space (1
) is released as electrons and excited argon gas (21
), and at the outlet of this space, an etching gas is discharged (22) through a system (16) of a doping system (13') by a plurality of ring-shaped nozzles (17), as a result,
The etching gas (22) is excited and activated by the non-product gas (21). In addition, a pair of electrodes (20)
, (20') is simultaneously applied to these reactive gases.

As a result, the activated gas flies along this electric field,
The substrate can be selectively etched.

In addition, in order to sufficiently spread the reactive gas in the reaction chamber and to activate the cyclotron, the pressure in the reaction space (1) and resonance space (2) is set to 1 to 10-'torr, for example 0.03 to 0.0QL.
It was set to torr. This pressure was achieved by adjusting the displacement of the vacuum pump (9) using a turbo pump together with the control valve (14) of the exhaust system (11).

Experimental Example 1 In this experimental example, Example 1 was used, and a silicon semiconductor was etched with nitrogen fluoride.

That is, the pressure in the reaction space was 0.003 torr, and argon was supplied as a non-product gas from (18) at a rate of 50 cc/min.

In addition, NF2 was supplied from (16) at 20 cc/min. As the electric field, a high frequency electric field of 13.56 LHz with a self-bias was applied. The microwave had a frequency of 2.45 GH2 and was regulated with a power of 30-500-, for example 200-. The resonance intensity of the magnetic field (5) and (5°) was set to 875 Gauss.

The substrate (lO) was a silicon semiconductor whose upper surface was selectively coated with photoresist. A non-single crystal semiconductor, such as an amorphous silicon semiconductor, on the surface to be formed is removed, and unnecessary gas is removed from the exhaust system (11
) was released. As a result, it was possible to obtain an etching speed of 15 people/second. This speed is three times faster than the 5 per second obtained with plasma etching alone. Furthermore, by cutting a resist pattern with a width of 0.3μ on this silicon substrate, it was possible to obtain anisotropic etching with a width of 0.3μ and a depth of 4μ.

Furthermore, it is effective to remove the reactive gas after anisotropic etching, introduce oxygen instead, and remove the resist remaining on the surface by ashing after this etching.

``Effects'' As is clear from the above description, the present invention can perform anisotropic etching of a large area substrate or a material to be etched on a substrate with extremely little damage to the surface to be etched. Ta. In addition, since cyclotron resonance is used, a high etching rate can be obtained.

The etching method of the present invention is applied to semiconductor devices such as photoelectric conversion devices, light emitting devices (former S), PET (field effect semiconductor devices), S
It can be fully applied to L elements (super lattice elements), HEHT elements, and VLSIs. Furthermore, the present invention is also effective for other live conductor lasers or optical integrated circuits.

In the etching method using cyclotron resonance of the present invention, it is effective to simultaneously apply optical energy and perform optical etching. In particular, it is effective to use an excimer laser (wavelength: 100 to 400+V), argon laser, nitrogen laser, etc. as a light source instead of a low-pressure mercury lamp, and select a resonant wavelength.

In the present invention, the substrates to be etched are mainly silicon semiconductors, glass substrates, and stainless steel substrates. However, in addition ■-■ compounds such as GaAs
, GaAlAs, InP, GaN, etc. Aluminum, silicide metals may also be used.

Furthermore, the etching method of the present invention is applicable not only to single crystal semiconductors (
Non-single-crystal semiconductors, such as amorphous semiconductors, are not only 5iGe1-x (0<Xd)
0<X<2), SlMCl-31 (0<X<1), 5i
It is also valid for Jn-x (0<X<4).

Further, in FIG. 1, the substrate may be in a lower or vertical structure, and the cyclotron and electric field may be emitted downward or laterally from the upper direction.

[Brief explanation of the drawing]

FIG. 1 shows a cyclotron resonance type plasma etching apparatus of the present invention.

Claims (1)

[Claims] 1. By applying electrons or activated reactive gas for etching using cyclotron resonance to a high frequency electric field or a direct current electric field in a direction perpendicular to the substrate using an electrode provided in a reaction chamber. A vapor phase etching method characterized by selectively etching the surface to be etched or anisotropically etching the entire surface of the substrate. 2. In claim 1, the gas activated using cyclotron resonance is selected from inert gases or non-product gases, and the reactive gas for etching includes at least a gas that generates a halogen element. A vapor phase etching method characterized by being selected. 3. In claim 1, the etching gas is carbon fluoride (CHnF_4_-_■0≦n<4), carbon chloride (CHnCl_4_-_■0≦n<4), silicon fluoride (SiF_4, Si_2F_6, etc.) or nitrogen fluoride (N
A vapor phase etching method characterized in that F_3, N_2F_4) is used.