JPS63304631A - Photo-excitated dry etching and equipment therefor - Google Patents

Abstract

PURPOSE:To enable the highly precise anisotropic etching only with photo- excitation etching reaction, by making etching gas adsorbed by a substrate and the substrate react with each other by light irradiation. CONSTITUTION:A substrate 1 on which a prescribed mask pattern is formed is set in a reaction vessel, the inside of which is exhausted. Then etching gas 3 is introduced into the reaction vessel, and absorbed by an aperture part of the mask 2 on the substrate 1. The etching gas 3 in vapor phase is exhausted and eliminated, the substrate 1 is vertically irradiated with light, to make the absorbed etching gas 3 and the substrate 1 react with each other, and volatile reaction product is exhausted and eliminated. By repeating the reaction process between the etching gas 3 and the substrate 1, the etching is processed up to a specified depth. In this process, the substrate 1 is vertically irradiated with light. As the result, the bottom part only is etched, and the sidewall is not subjected to etching. Thereby, the anisotropic etching is enabled.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to dry etching used in the production of semiconductor integrated circuits, thin film functional devices, etc., and particularly relates to a photoexcited dry etching method and apparatus with excellent anisotropy accuracy. Regarding.

[Conventional technology]

Although photo-excited dry etching basically relies on radical reactions, the etching shape is isotropic, but anisotropic etching is desired for forming fine patterns.

Conventionally, due to the anisotropy of photoexcited etching, a method of etching while forming a sidewall protective film (Japanese Patent Laid-Open No. 61-755
29, JP-A-60-260131, JP-A-60=1
65724, JP-A No. 60-165725) and a method using both plasma excitation and optical excitation (JP-A-61-1503).
No. 39.

JP-A No. 60-253230) and the like are known.

[Problem that the invention seeks to solve]

In the prior art method of etching while forming a sidewall protective film, it is difficult to balance the competition between the film forming reaction and the etching reaction. Particularly when there are island-like or hole-like patterns of various sizes in the substrate, the competitive reactions become locally unbalanced, making it difficult to perform accurate anisotropic etching. Also, in the method of using plasma excitation and optical excitation in combination, there is a problem in that the pattern sizes are unbalanced, similar to the above.

SUMMARY OF THE INVENTION An object of the present invention is to provide a highly accurate anisotropic etching method and apparatus using only a photoexcited etching reaction, which does not involve controlling competitive reactions or causing differences due to pattern size.

[Means for solving problems]

The above object is achieved by irradiating the substrate with light and causing the etching gas adsorbed on the substrate to react. Specifically, (1) A substrate on which a predetermined mask pattern is formed is placed in a reaction container, and the inside of the reaction container is evacuated.

(2) Etching gas is introduced into the reaction vessel, and the etching gas is adsorbed into the opening of the mask on the substrate.

(3) Evacuation and removal of etching gas in the gas phase.

(4) The substrate is irradiated with light perpendicularly to cause the adsorbed etching gas to react with the substrate, and volatile reaction products are removed by exhaust.

(5) Repeat steps (2) to (4) above to etch to a predetermined depth.

This is achieved by

[Effect]

Conventionally, photo-excited dry etching involves exciting an etching gas in a gas phase to cause it to react with a substrate. Therefore, the etching gas excited by the light irradiation diffuses in the gas phase and collides with the substrate, so that the etching becomes isotropic.

On the other hand, in the present invention, there is no etching gas in the gas phase during light irradiation, and the only molecules contributing to etching are the etching gas molecules adsorbed on the substrate.

For this reason, when the substrate is irradiated with light, the adsorbed molecules and the substrate react and are etched. At this time, by directing the light irradiation perpendicular to the substrate, only the bottom surface is etched and the side walls are not etched, resulting in anisotropic etching. Etching is possible.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 2 shows a photoexcited dry etching apparatus used in the present invention. The equipment includes a reaction container system, an excitation light source 9 reaction gas supply system,
Consists of exhaust system. The reaction vessel system consists of a reaction chamber 11 and a load lock chamber 13 via a gate valve 12.
1 has a light entrance window 14 made of synthetic quartz. Excitation light source 20
is a low-pressure mercury lamp (wavelength λ = 185 nm and 254 n
m, illuminance of sample surface 60mW/al, λ=254n
m), mercury-cannon lamp (continuous spectrum with wavelength of 220 nm or more, illumination intensity of 300 mW/aA (λ × 32゜nm)
), excimer laser (A r F λ=193 nm.

Output 200mJ, KrF λ = 249 nm,
Output 250mJ, XeCQ λ = 308nm
, output 150 mJ), and a shutter 21 was used to turn on and off the light irradiation. The reaction gas supply system uses hydrogen chloride and chlorine gas, and the on/off speed of the valve 31 is 10 m.
It is s. The operating timing of the shutter 21 and the valve 31 is controlled by a controller 22. The exhaust system includes a turbo molecular pump 41 (pumping speed 150 (Ml/s)) and a turbo roughing pump 42 (pumping speed 6000 Q/m1n).
The ultimate pressure is IX 10-7 Torr.

FIG. 1 is a schematic cross-sectional view of a sample showing the process of the present invention.

(a) A substrate 1 on which an etching mask 2 of a predetermined pattern is formed is placed in a reaction chamber of the photoexcited etching apparatus, and after the reaction chamber is evacuated, an etching gas 3 is introduced so that the etching gas is adsorbed onto the substrate 1. State 4 is shown.

(b) After exhausting and removing the etching gas in the gas phase, the etching gas 4 adsorbed on the surface of the substrate 1 is irradiated with excitation light 5 to excite the reaction; (c) Volatile reaction products 6 are exhausted and removed; , an etching groove is formed in the substrate 1, and by repeating the above steps, an etching groove of a predetermined depth can be formed.

Anisotropic etching using a photoresist mask of phosphorus-diffused polycrystalline silicon.

Substrate 1 has a thickness of 500 nm with phosphorus diffused, and a sheet resistance of 13
A 1.0 μm line pattern was formed using positive photoresist 2 on a polycrystalline silicon film of Ω/hole. Hydrogen chloride (HCρ) was supplied as an etching gas at 10 Torr and adsorbed onto the substrate, and then evacuated at 10 −3 Torr. Ultraviolet light (λ=
185nm.

254 nm) to excite the reaction and perform etching. Light irradiation was performed for 2 seconds by opening and closing the shutter. After that, HCQ gas was supplied again to 10 Torr, and 10"-8
The chamber was evacuated to Torr and light irradiation was repeated.

Repeat the above steps 20 times per minute, and a reaction time of 40 minutes will result in 300
The silicon film of 0 people could be etched. The cross-sectional shape of the etching is almost perpendicular to the substrate surface, and no side etching is observed.

Example 2 Photoresist mask anisotropic etching of non-doped polycrystalline silicon film.

The substrate 1 is a polycrystalline silicon film with a thickness of 500 nm deposited on a silicon oxide film.
．． A line and space pattern of 0 μm was formed. First, about 450nm is etched using normal reactive plasma etching.
Anisotropically etched to a depth of . In this state, it was installed in a photo-excited etching apparatus, using chlorine as a reactive gas and a mercury-cannon lamp as an excitation light source. The same operation as in Example 1 was repeated 20 times per minute for 30 minutes. As a result, only the polycrystalline silicon film could be selectively etched without etching the underlying silicon film, and its cross-sectional shape became almost perpendicular to the surface of the substrate. Furthermore, it was found that the cross-sectional shape did not change even after over-etching, and a nearly vertical cross-section was maintained.

Example 3 Anisotropic etching of a phosphorus-diffused polycrystalline silicon film using a silicon oxide film mask.

Substrate 1 has a thickness of 500 nm with phosphorus diffusion, and a sheet resistance of 13
A polycrystalline silicon film of Ω/mouth, with a thickness of 0.8 to 2 μm on top of it.
A silicon oxide film mask 2 having an island-like pattern is then formed. Hydrogen chloride was used as the etching gas, and excimer laser (ArFλ=193 nm) was used as the excitation light. While evacuating the sample, etching gas was injected in pulses onto the sample surface to adsorb the etching gas onto the sample surface, and the substrate was irradiated with laser light perpendicularly. The emission frequency of the laser is 200 Hz. By scanning the laser beam, the entire surface of the substrate was irradiated with four pulses each. introduction of reaction gas,
Adsorption and light irradiation pulses were alternately repeated. As a result of etching for 30 minutes, the polycrystalline silicon film was selectively etched, and its cross-sectional shape was almost perpendicular to the substrate surface, with no side etching observed. Furthermore, the cross-sectional shape was not affected by over-etching. It turned out that.

FIG. 3 shows the opening/closing status of the reaction gas introduction valve in the above embodiment, the accompanying pressure change near the sample surface in the reaction chamber, and the time sequence of light irradiation.

(a) Operation of installing a sample through the reaction chamber 11, the lock chamber 13 and the gate valve 12 (b) Operation of evacuating the reaction chamber 11 and stabilizing the pressure below 10'' Torr (C) Reaction gas introduction valve (d) Operation to close the reaction gas introduction valve 31 and exhaust and remove the reaction gas in the reaction vessel 11. (e) Operation to exhaust and remove the reaction gas in the reaction vessel 11 (e) Operation to open the reaction gas (HCQ) to the sample surface and adsorb it. Excimer laser λ=19
3 nm, emission frequency 200 Hz, pulse energy 200 mJ, pulse width l 6 n S + beam shape 2
0x8mn) and irradiate and scan the sample surface with light (c), (cl), and (e) each at 0.5
s.

is, is is repeated at a total cycle of 2.5 seconds.

〔Effect of the invention〕

According to the present invention, anisotropic etching using photoexcitation dry etching becomes possible, and a fine pattern can be etched into a desired shape.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of a sample for illustrating the process of the present invention;
FIGS. 2 and 3 show a schematic diagram of a photoexcited dry etching apparatus used in the present invention and its time sequence. 1. Substrate, 2. Mask, 3. Etching gas, 4
... adsorption etching gas, 5 ... excitation light, 6 ... volatile reaction product, 11 ... reaction chamber, 20 ... excitation light source, 31 ... reaction gas introduction valve, 41.42.・・・
Exhaust pump. 6---Katsukuda 11 means Shakyu Hakkan

Claims (1)

[Claims] 1. A method of etching a sample by causing a photochemical reaction with an etching gas, in which: (1) the sample is placed in a reaction vessel; (2) the interior of the reaction vessel is replaced with an etching gas; (3) exhaust and remove the etching gas in the gas phase in the reaction vessel; (4) irradiate the sample surface with light to react with the adsorbed etching gas and generate volatile reaction products. (5) repeating the steps (2) to (3) above to etch a predetermined amount. 2. In order to dry-etch the sample by photochemical reaction, in an apparatus consisting of a reaction vessel, an excitation light source, a reaction gas supply system, and an exhaust system, after placing the sample in the reaction vessel, [1] introducing the reaction gas; [2] ] Exhaust of a reaction gas; [3] A photo-excited dry etching apparatus characterized by having a sequence of repeating light irradiation onto a sample surface a predetermined number of times. 3. Claim 2 provides a sequence in which, after a sample is placed in a reaction vessel, while the interior of the reaction vessel is evacuated, pulsed injection supply of reaction gas and pulsed irradiation of excitation light to the sample surface are alternately repeated. A photoexcited dry etching apparatus comprising: