JPS61150339A - Method for dry etching - Google Patents

Abstract

PURPOSE:To enable the anisotropic etching of a few damages without decreasing an etching rate by irradiating the predetermined region in an etching chamber with the light including the wavelength absorbed by the gas introduced into the etching chamber. CONSTITUTION:On the side walls of a vacuum chamber 11 forming an etching chamber, windows made of transparent plates 21 and 22 are formed. In this constitution, the light 24 from a light source 23 irradiates a discharge region between electrodes 12 and 13 through the plate 21 and is led out through the plate 22. For a sample 16, N<+> polysilicon is used and Cl2 is introduced thereby effecting the etching using an excimer laser as a light source. The etching rate is much faster than that when light irradiation is not utilized and a damage is hardly seen. Since this method is able to make a difference in potential smaller and the etching rate faster besides to reduce damages, it is suitable for the minute processing.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a dry etching method, and particularly to a dry etching method using light irradiation.

[Technical background of the invention and its problems]

Conventionally, in semiconductor device manufacturing, reactive ion etching has been mainly used to achieve anisotropy during etching. In the reactive ion etching method, ions generated in the discharge region generate a potential difference (V) between the discharge phase and the surface of the object to be etched.
dc). Anisotropy is achieved by making these accelerated ions incident perpendicularly on the substrate.

However, this type of method has the following problems. That is, the incidence of accelerated ions may damage the object to be etched, and therefore the accelerating voltage cannot be increased too much.

The potential difference Vdc generated by the discharge largely depends on the discharge conditions, and the amount of active species generated by the discharge also depends on the discharge. Therefore, in dry etching using only discharge, it is difficult to independently control both the generation of VdC and the generation of active species, and the discharge conditions for etching are narrow. For example, by lowering the power for discharging, V
Although it is possible to reduce dc and perform etching without damaging the object to be etched, this also reduces the etching speed, which poses a problem in a process where mass productivity is important.

[Purpose of the invention]

An object of the present invention is to provide a dry etching method that can perform anisotropic etching with less damage without reducing the etching rate.

[Summary of the invention]

The gist of the present invention is to promote the activation of gases contributing to etching by irradiation with light.

That is, the present invention provides a dry etching method in which at least an active gas is introduced into an etching chamber in which a sample to be etched is placed, and a discharge is generated in the etching chamber to etch the sample. In this method, light including a wavelength range that is absorbed by the gas is irradiated.

Note that the above-mentioned active gas is a gas that chemically etches the object to be etched by performing electric discharge.

〔Effect of the invention〕

According to the present invention, activation of the gas can be promoted by light irradiation, and many active species contributing to etching can be formed. Therefore, a sufficiently high etching rate can be maintained even if Vdc is made small. That is, anisotropic etching with less damage can be achieved without reducing the etching speed. Therefore, super L
It is suitable for microfabrication in the SI manufacturing process and is effective for improving productivity.

[Embodiments of the invention]

First, before explaining embodiments, the basic principle of the present invention will be explained.

The present invention is a dry etching method that utilizes a chemical reaction caused by a discharge, in which the VdC generated by the discharge is controlled by discharge conditions, and active particles generated by the discharge are activated by irradiating light onto the discharge area. This method generates particles or excites the surface of the object to be etched by irradiating light.

Generally, VdC is proportional to (depends on) the power applied to the N pole for discharging, and as the discharge power is increased, VdC also increases accordingly. In discharge with such high power, many active species are generated and VdC is also high, so that high-speed and anisotropic etching can be achieved. However, Vd
Since c is large, it may damage the crystallinity of the object to be etched, which poses a problem in manufacturing devices. The Vdc required to achieve anisotropy may be about several tens of volts. However, if the discharge power is lowered and the discharge is performed such that Vdc is on the order of several tens of volts, the generation of active species will also decrease and the etching rate will decrease.

In the present invention, etching is performed by increasing the etching rate by supplementing the active species, which decrease by lowering Vdc, by excitation of particles or substrate by light irradiation. Light irradiation into the discharge region excites particles in the neutral ground state,
In addition, the discharge further excites the excited particles, creating radicals.

Generates excited particles such as ions. This makes it possible to perform anisotropic etching at high speed without damaging the object to be etched by reducing Vdc.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic diagram showing a dry etching apparatus used in an embodiment of the present invention. In the figure, reference numeral 11 denotes a vacuum container forming an etching chamber, and parallel plate electrodes 12 and 13 are accommodated within this container 11. Upper electrode 12
is installed, and the lower electrode 13 is connected to a high frequency power source 15 via a matching circuit 14. The sample to be etched 16 is placed on the lower electrode 13.

On the other hand, the clay wall of the container 11 is provided with a gas inlet 17 for introducing reactive gas (active gas) activated by electric discharge, and the bottom wall of the container 11 is provided with a gas inlet 17 for discharging the gas. An exhaust port 18 is provided. In addition, windows are formed on the left and right side walls of the container 11, and these windows are closed to open the transparent plate 2). 22 is attached. A light source 23 such as a laser oscillator is disposed on the right side of the container 11. The light 24 from the light source 23 is then transmitted to the transparent plate 2).
The light is introduced into the container 11 through the rays, irradiates the discharge area between the electrodes 12 and 13, and is led out through the transparent plate 22. Note that 25 in the figure indicates an insulator.

Here, the light 24 from the light source 23 may be incident on the discharge region of the electrodes 12.about.13WR. However, it is not necessary to irradiate the discharge area uniformly, and a part of the discharge area may be irradiated with condensed irradiation or with a beam-shaped irradiation. Also, the second
As shown in the figure, a beam of light 24 may be irradiated near the surface of the sample 16. In other words, it is better to make the light 24 incident so that excited particles can be efficiently generated and supplied to the sample 16. Depending on the discharge form, etc., it is better to make the light 24 incident at an efficient location using various types of discharge devices.

The light source 23 needs to be one that allows particles in the optical path to absorb the light depending on the type of gas used for discharge. There are no restrictions on the wavelength range, from the vacuum ultraviolet region to the infrared region.
Any material may be used as long as it can excite particles in the optical path inside the container 11. When monochromatic light such as a laser is used, particles can be selectively excited. Further, a light source with a wide wavelength range such as an HQ clamp may be used. Furthermore, a plurality of light sources may be used. Furthermore, the reaction may be promoted by adding a small amount of a sensitizer that absorbs light and accelerates the reaction to the discharge region. The table below shows examples of gases and light sources in which the gases exhibit light absorption. When a discharge is performed, excited state molecules of atoms are generated, and the excited particles may absorb light of wavelengths other than those shown in the table.

Next, a dry etching method using the above apparatus will be explained.

N+ poly-Si was used as the sample 16, and C(1
2 was used. First, etching was performed under the same conditions as before without irradiation with light. That is, the high frequency power is 200 [W]
Sample 16 was etched under conditions where Vdc was 50 [V]. As a result, the etching speed was 500
[person/min] was obtained. This etching speed is extremely slow, making it useless in processes where mass production is important. Next, increase the high frequency power to 400
[W] and Vdc was 300 [V] when sample 16 was etched, and the etching rate was 20.
00 [people/1n1 were obtained. This speed is sufficiently high and can be used in processes where mass productivity is important. However, in this case, the sample was seriously damaged. This is because by increasing Vd(j, the energy of the accelerated ions becomes too large.

Next, the sample 16 was etched using light irradiation. That is, etching was performed using an excimer laser as the light source 23, which generates light including a wavelength range absorbed by the C12 gas, under the conditions that the high frequency power was 200 [W] and the Vdc was 50 [V]. As a result, an etching rate of 1500 [people/1n] was obtained. This speed is much faster than when no light irradiation is used, and it is also fast enough to be applied to processes where mass production is important. The reason why the etching rate increased is that the amount of active species increased due to light irradiation. Further, in this case, almost no damage to sample 16 was observed.

Thus, according to the method of this embodiment, a sufficiently high etching rate can be obtained even if Vdc is made small. For this reason, two advantages are achieved: faster etching speed and less damage.
It is possible to achieve two effects simultaneously, and its industrial value is extremely high. It also has the advantage that it can be easily realized by simply adding the light source 23 to the conventional device.

FIG. 3 is a schematic diagram showing a dry etching apparatus used in another example method. Note that the same parts as in FIG. 1 are denoted by the same reference numerals 9, and detailed explanation thereof will be omitted. This device differs from the device shown in FIG. 1 in that the sample 16 is placed not on one of the parallel plate electrodes 12.13, but on the other electrode 31. That is, the parallel plate electrodes 12.13 are arranged to face each other in the horizontal direction, and the electrode 31 is arranged below these electrodes 12.13 in parallel to the above-mentioned facing direction.

This electrode 31 has a DC power supply 3 for accelerating ions.
2 are connected. The light 24 is irradiated in the vicinity of the sample 16 from the lateral direction.

Even if such an apparatus is used, etching can be performed using light irradiation in the same manner as in the method of the previous embodiment. That is,
An anisotropic etched shape is achieved by the electric current 8132, and a voltage is applied to create an electric field to an extent that does not damage the sample 16 to be etched, and the gas is activated by light irradiation, thereby reducing the etching rate. It is possible to perform anisotropic dry etching with less damage without causing damage. Here, the light irradiation area may include a discharge area, as shown by a broken line 24' in FIG. 3, and be parallel to the transport direction of the active particles and incident on the sample surface.

In this case, it is effective to improve the etching rate because not only the particles in the space but also the reaction on the sample surface or the activation of the sample surface can be observed.

Note that the present invention is not limited to the methods of each embodiment described above. For example, the gas introduced into the container is not limited to the gases shown in the coating, but any active gas may be used. Moreover, a mixed gas of multiple kinds of active gases may be used. Furthermore, a mixed gas of an active gas and an inert gas may be used. Further, the light source used may be any light source that includes a wavelength range that is absorbed by at least one of the gases introduced into the container. Further, conditions such as VdC and light irradiation intensity may be adjusted as appropriate depending on the specifications. In addition, various modifications can be made without departing from the gist of the present invention.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing a dry etching apparatus used in one embodiment of the method of the present invention, FIG. 2 is a schematic diagram for explaining a modification of the above embodiment, and FIG. 3 is a diagram of another embodiment of the method. 1 is a schematic configuration diagram showing a dry etching apparatus used in the process. DESCRIPTION OF SYMBOLS 11... Vacuum container (etching chamber), 12... Upper electrode, 13... Lower electrode, 14... Matching circuit, 15... High frequency power supply, 16... Sample to be etched, 17...・Gas inlet, 18...gas exhaust port, 2)
22... Transparent plate, 23... Light source, 24... Irradiation light, 25... Insulator, 31... Electrode, 32... DC power supply. Applicant's agent Patent attorney Takehiko Suzue Figure 1

Claims (7)

[Claims] (1) A dry etching method in which a gas is introduced into an etching chamber in which a sample to be etched is placed, and a discharge is generated in the etching chamber to etch the sample. A dry etching method characterized by irradiating light that includes a wavelength range that is absorbed. (2) The region to which the light is irradiated is a discharge region, a region through which active species of gas generated in the discharge region pass, or a sample surface region including a gas phase near the surface of the sample. A dry etching method according to claim 1. (3) The dry etching method according to claim 1, characterized in that parallel plate electrodes are used as the means for generating the discharge, and the sample is placed on one of these electrodes. (4) The dry etching method according to claim 1, characterized in that parallel plate electrodes are used as the means for generating the discharge, and the sample is placed on an electrode different from these electrodes. (5) The dry etching method according to claim 1, wherein the gas is an active gas that absorbs the light. (6) The dry etching method according to claim 1, wherein the gas is composed of a plurality of active gases, and at least one of them absorbs the light. (7) The dry etching method according to claim 1, wherein the gas is a mixed gas of an active gas and an inert gas, and at least the inert gas absorbs the light.