JPS6231126A - Dry etching method - Google Patents

Abstract

PURPOSE:To make a form in preventing the roughness on the surface by a method wherein at least tow kinds of reactive gases containing harogen elements are introduced into a vacuum container, and the reactive gases are excited to produce active species so as to etch a substrate to be processed with those species. CONSTITUTION:A SiO2 mask 22 is formed on a plane-directional (100) P-type Si substrate 21 as a substrate to be processed 12, with the mask on which a groove 23 is formed with RIE. After the contamination due to organic substance has been removed from the surface-processed substrate 12 with O2 plasma beforehand, the substrate is placed on a sample stand 13. After air within a container 11 has been discharged with an air-discharge opening 18, a mixture gas of NF3 and Cl2 is introduced into an electric discharge pipe 15 from a gas introduction opening 14 to produce active species with microwave-discharge by means of a microwave power source 16. The active species are introduced into the container 11, with the result that it is made possible to etch the inside of the groove 23, that is, washing process is made possible. Thus, the inside of the groove 23 is smooth, allowing favorable washing.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to a dry etching method, and more particularly to a dry etching method for performing damage-free dry etching, surface treatment, etc.

[Technical background of the invention and its problems]

The integration of semiconductor integrated circuits continues to progress, and today even 16 Mbit RAM is becoming a realistic goal. As one method to realize this, structures such as FCC and CCC have been proposed, and
There is a need for a technique to precisely control the shape and etch a pattern having a groove with a width of less than . Currently, the only practical etching method for LSI structures is reactive ion etching (
However, since this etching method involves ion bombardment, the atomic arrangement on the surface of the material to be etched is displaced. This kind of damage is in the hundreds
[The damage ranges from 1 person to several thousand people, and a step to remove this damaged layer after etching is essential. this is,
When considering submicron processing, this is expected to be a major obstacle, and an etching technology that does not rely on the impact of high-energy particles and has good controllability is required.

On the other hand, no matter what etching method is employed, reaction products and the like are expected to remain on the outermost surface 1 after etching, and post-treatment to remove them is necessary. A cleaning method that removes contamination on the outermost surface layer along with the material to be etched can be considered a type of etching, and water-based wet cleaning is currently widely used. However, as etching shapes become narrower and deeper in the future, the problem of surface tension will increase, and it is questionable to what extent, for example, it is possible to completely wash out the grooves with water. Wet cleaning also becomes an obstacle when automating processes. As a type of dry cleaning, CF4 +02 CD
E (chemical dry etching) is sometimes used, but if it is not combined with wet cleaning, problems such as surface roughness may occur.

Furthermore, in order to apply the CDE method to a large area of material to be etched, the active species must have a long life, and the range of selection of reaction gases is also limited.

(Object of the Invention) The present invention has been made in consideration of the above circumstances, and its purpose is to be able to control the etched shape without causing roughness on the etched surface, and to improve the quality of future semiconductor integrated circuits. The object of the present invention is to provide a dry etching method suitable for etching, surface treatment, etc. in manufacturing.

[Summary of the invention]

The gist of the present invention is to control the etching shape by using two methods.
The purpose is to use a reactive gas containing more than one type of halogen element.

That is, the present invention provides a dry etching method for etching a substrate to be processed housed in a vacuum container, in which at least two kinds of reactive gases containing a halogen element are introduced into the container to prevent damage caused by charged particles to the substrate to be processed. At least one of these reactive gases is excited to generate active species without giving any This is the method I used.

In addition, from the viewpoint of increasing the etching rate, it is advantageous that one of the active species is an F atom. The present inventors have discovered that in a mixed system of Ca-based gas and F-based gas, the etched shape changes depending on the gas composition ratio, and at the same time, the roughness of the etched surface changes. Figure 7 is CF4
This graph shows the changes in etching shape and etching speed depending on the amount of CQ2 added when Ca2 is added to a mixed gas of 02 and 02 to generate active species, which are extracted to etch single crystal silicon. It is. CQ2
The etching rate decreases as the amount added increases. Also,
The etched shape is isotropic where (/22 is small) and the etched surface is noticeably rough.
As the number increases, although there is an undercut, (111
) surface appears depending on the surface orientation, and the etched surface becomes smooth. This can be explained by assuming that etching by C2-based active species and F-based active species occurs simultaneously.

In order to cause etching, it is generally necessary to excite a reactive gas by some means to generate active species.

This excitation may be performed in the vicinity of the material to be etched, or it may be performed at a remote location to transport the active species onto the material to be etched. In the former case, it is necessary that the excitation means do not damage the material to be etched, and light or the like is used. In the latter case, although the excitation means is free, the problem is whether the generated active species will reach the material to be etched within its lifetime. The present inventors have found that when a mixed gas of two or more reactive gases is used, if at least one active species has a long life, other active species are also apparently transported upwards by 1q. This is because long-lived active species on the surface of the etched material dissociate other active species that have been deactivated by recombination, etc.
This is thought to be because a phenomenon similar to atomic Ce titration occurs.

Furthermore, in order to increase the anisotropy, it is effective to simultaneously supply an organic compound gas that will serve as a precursor of the deposit Ill and to irradiate the substrate with light or charged particles such as ions and electrons perpendicularly.

[Effect of onset week]

According to the present invention, the etching shape can be controlled by the composition ratio of the reactive gas supplied.

In addition, by selecting the gases to be mixed, the life of the short-lived active species can be made to have an apparently longer life, so that restrictions on the device configuration can be reduced.

For example, it works uniformly on a large area of the material to be etched.

A flow path with low conductance for supplying species can also be designed without being limited by the lifetime of the active species.

Further, since it is sufficient to excite at least one of the reactive gases, there are advantages such as a wider range of selection of excitation means and reactive gases.

[Embodiments of the invention]

Hereinafter, details of the present invention will be explained with reference to illustrated embodiments.

FIG. 1 is a schematic diagram showing a dry etching apparatus used in the first embodiment of the present invention.

In the figure, reference numeral 11 denotes a vacuum container, and a sample stage 13 on which a substrate 12 to be processed is placed is installed inside the container 11. A gas inlet 14 is provided in the container 11, and one end of a discharge tube 15 is connected to this gas inlet 14. The discharge IF 15 is connected to the waveguide 1 connected to the microwave
It is coupled to 7. A reactive gas containing a halogen element is introduced into the other end of the discharge tube 15. Further, the gas in the container 11 is exhausted from a gas exhaust port 18.

Next, a surface treatment method using the above apparatus will be explained with reference to FIG.

First, as the substrate 12 to be processed, as shown in the second factor (a), a SiO2 mask 22 was formed on a P-type Si substrate 21 with a plane orientation (100), and a groove 23 was formed by RIE. This substrate 12 to be processed is placed on a sample stage 13 after removing contamination caused by organic matter on the surface using 02 plasma. After evacuating the inside of the container 11, a mixed gas of NF3 and C112 is introduced into the discharge tube 15, and these active species are generated by microwave discharge, and the active species are introduced into the container 11.
Introduce. As a result, as shown in FIG. 2(b), the groove 2
The inside of 3 was thinly etched, that is, cleaned.

At this time, the inside of the groove 23 was smooth and good cleaning was performed.

On the other hand, when only NF3 was supplied as the reactive gas, the inside of the groove 23 was extremely rough as shown in FIG. In some cases, reaction heat is generated significantly and it is extremely difficult to control the etching rate, but by adding CJ22, it has become possible to reduce the etching rate to a value that can be sufficiently controlled.

Thus, according to the method of this embodiment, NF is used as the reactive gas.
By using a mixed gas of C.sub.3 and C.beta..sub.2, it is possible to clean the inside of the cap 23 provided on the Si substrate 21 without causing surface roughness or the like. Further, since the gas is activated in a region separate from the container 11, the substrate 12 to be processed is not damaged by charged particles. Further, there is an advantage that the etching rate and etching shape can be controlled by adjusting the amount of CJ22 gas added.

FIG. 3 is a schematic configuration diagram showing a surface treatment apparatus used in the second embodiment method of the present invention. Note that the same parts as in FIG. 1 are given the same reference numerals, and detailed explanation thereof will be omitted.

The difference between this device and the device shown in FIG. 1 is that the NF3
The purpose is to introduce gas and CQ2 gas through independent gas introduction ports. In other words, NF! As in the previous embodiment, the gas passes through the discharge tube 15, is excited by discharge, and is then introduced into the container 11 from the gas inlet 14. On the other hand, Cl
22 gas is directly introduced into the container 11 from the gas inlet 31 without being excited by discharge or the like.

When performing surface treatment using this device, the active species introduced into the container 11 are the active species of NF3 gas excited by the discharge, and the Cl12 gas introduced into the container 11 is excited by this active species. active species of the gas are produced. Therefore, similar to the first embodiment described above, the second embodiment
The substrate 12 to be treated as shown in FIG. 1(a) can be surface-treated as shown in FIG. 1(b).

FIG. 4 is a schematic diagram showing a dry etching apparatus used in the third embodiment of the present invention.

Note that the same parts as in FIG. 1 are given the same reference numerals, and detailed explanation thereof will be omitted.

This apparatus differs from the apparatus shown in FIG. 1 in that it is provided with an optical system for irradiating light onto the substrate to be processed.

That is, a light source 41 made of, for example, an ArF laser is disposed above the container 11, and from now on it! The light from 41 is introduced into the container 11 through the light transmission window 42, and is irradiated perpendicularly onto the upper surface of the substrate 12 to be processed.
.

Next, a 3i etching method using the above-mentioned apparatus will be explained with reference to FIG.

First, as the substrate 12 to be processed, as shown in FIG. 5(a), a P-type Si substrate 51 with a (100) plane orientation and an SiO2 mask 52 formed thereon was used.

This substrate 12 to be processed was placed on the sample stage 13 of the apparatus shown in FIG. 4, and selective etching of the 3i substrate 51 was performed.

Here, the gas introduced into the container 11 through the discharge tube 15 is a 1=1 mixed gas of NF3 and Cl2 to which methyl methacrylate (MMA) is added. Meanwhile, the upper surface of the substrate 12 to be processed was irradiated with laser light from the light source 41 . As a result, 81 etchings of the substrate 12 to be processed could be performed. Etched substrate 12
When the cross-sectional shape of the
As shown in Figure (b), a vertical etched shape with almost no undercut was obtained. The reason for this is that polymers from MMA are deposited on the etching sidewalls, and this deposit 54 is
This is because the deposit 54 is decomposed by the energy of the light irradiated surface, and etching progresses in the vertical direction.

Thus, according to the method of this embodiment, the Si substrate 51 can be etched vertically without damaging the 3i substrate 51 due to charged particles.

FIG. 6 is a schematic diagram showing a dry etching apparatus used in the fourth embodiment of the method of the present invention.

Note that the same parts as in FIG. 1 are denoted by the same reference numerals, and detailed explanation thereof will be omitted.

This apparatus differs from the apparatus shown in FIG. 1 in that the excitation of the reactive gas is performed not by electric discharge but by light irradiation. That is, a predetermined reactive gas is introduced into the gas inlet via valves 61 and 62. Lights 1 [163 and 64 are arranged on the left side of the container 11, respectively, and the light from these light sources 63 and 64 enters the container 1 through a light transmission window 65.
1 and is irradiated substantially perpendicularly to the processing surface of the substrate 12 to be processed. Here, as the light source 63, A
rF laser, light! As 64, an HG clamp was used.

When etching is performed using the above device, pulp 61
．． 62 is opened and a mixed gas of NF3 and Cl22 and MMA are introduced into the container 11. These gases are activated by light irradiation, and active species similar to those in the third embodiment described above are formed.

Therefore, a vertical etched shape similar to that of the third embodiment method can be obtained.

Note that the present invention is not limited to the methods of each embodiment described above. For example, instead of the NF3 gas, XeF
2. It is possible to use SFs, CF4, etc. Also,
Instead of CQ2 gas, Br2,12, CF3 Br
, CC(14, etc.(7)Cl2°Sr,I can be used.

Furthermore, instead of these gases, any reactive gas containing at least two types of halogen elements can be used.

Further, the light source for exciting the reactive gas may have a wavelength that causes the desired dissociation reaction, and depending on the case, the light source may be irradiated using a spectroscope or filter. In addition to electric discharge, light irradiation, R-son beam irradiation, or heat can be used as means for exciting the reactive gas in a region separated from the container.

In addition to MMA, the gases introduced for forming the deposited film include various acrylic compounds, tetramethylsilane, methane,
Other organic compounds can be used. Furthermore, instead of light irradiation for the purpose of shape control, charged particle irradiation may be performed.

In addition, the equipment used is as shown in Figures 1, 3, 4, and 6 above.
It is not limited to the figure in any way, and can be changed as appropriate according to the specifications. For example, it is also possible to adopt a configuration in which the substrate to be processed is placed with its processing surface facing down. others,
Various modifications can be made without departing from the spirit of the invention.

[Brief explanation of drawings]

Fig. 1 is a schematic configuration diagram showing a surface treatment apparatus used in the method of the first embodiment of the present invention, and Figs. 2(a) to (C) are for explaining the 3i surface treatment method using the above apparatus. 3 is a schematic block diagram showing the surface treatment apparatus used in the method of the second embodiment, FIG. 4 is a schematic block diagram showing the dry etching apparatus used in the method of the third embodiment, and FIG. Diagram (a)
(b) is a cross-sectional view for explaining the method of etching Sl using the dry etching apparatus described above, FIG. 6 is a schematic configuration diagram showing the dry etching apparatus used in the method of the fourth embodiment, and FIG. FIG. 3 is a characteristic diagram showing changes in etching rate and etching shape with respect to addition amount. 11... Vacuum container, 12... Substrate to be processed, 13...
・Sample stage, 14.31-...Gas inlet, 15...Discharge tube, 16...Microwave power supply, 17...Waveguide,
18...Gas exhaust port, 21.51...3i board, 2
2.52...SiO2 mask, 23.53...groove,
41,63°64...Light source, 42...Light transmission window, 5
4... Sediment. Figure 1 Figure 2 Figure 3 Figure 4

Claims (6)

[Claims] (1) At least two reactive gases containing a halogen element are introduced into a vacuum container containing a substrate to be processed, and at least one of these reactive gases is introduced without damaging the substrate to be processed by charged particles. A dry etching method characterized by etching a substrate to be processed by exciting and generating active species. (2) The dry etching method according to claim 1, wherein at least one of the active species is an F atom. (3) The dry etching method according to claim 1, wherein discharge, electron beam irradiation, light irradiation, or heat is used as means for exciting the reactive gas to generate active species. (4) As the means for exciting the reactive gas to generate active species, these active species are generated in a region separated from the inside of the container. The dry etching method described in Section 3. (5) The dry etching method according to claim 1, characterized in that the gas introduced into the container is irradiated with light as means for exciting the reactive gas to generate active species. (6) A patent characterized in that, as means for exciting the reactive gas to generate active species, the reactive gas introduced into the container is passed through a discharge plasma formed in a region different from the inside of the container. A dry etching method according to claim 1.