JPS63232333A - Treatment of extra-fine surface - Google Patents

Abstract

PURPOSE:To facilitate forming an extra-fine pattern by a method wherein a conductive probe needle is made to approach the neighborhood of the electrode of a substrate to be treated and a tunnel current is applied between the substrate and the needle. CONSTITUTION:A conductive probe needle 5 is made to approach the neighborhood of the electrode on the surface of an Si substrate 2 to be treated in a reactive gas atmosphere and a tunnel current is applied between the substrate 2 and the needle 5. The most intense tunnel current is applied between the most protruding atoms in the tip of the probe needle 5 and the closest atoms in the surface of the substrate 2. Therefore, electrons are preferentially implanted into the parts of the substrate 2 surface to which the tunnel current is applied. With this constitution, extra-fine etching pattern and deposition pattern can be drawn.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a surface treatment method for dry etching and deposition of semiconductor substrates, and more particularly.

This invention relates to a method suitable for ultrafine surface treatment in the angstrom or nanometer range.

[Conventional technology]

In recent years, research and development of optical excitation processes as dry etching and deposition methods for semiconductor substrates has been active. Through such research, it has become clear that electrons play an important role in etching reactions and deposition reactions. For example, when dry etching a silicon substrate by dissociating chlorine gas with ultraviolet light to generate radicals, the etching reaction progresses with n-type silicon, but with additive-free or p-type silicon, an interband transition is induced on the substrate surface. This @ phenomenon, which does not etch unless there is light irradiation, is due to the fact that in n-type silicon, there are many electrons, whereas in °C5 additive-free or P-type silicon, hole-electron pairs are formed only after light irradiation. It is considered. Then, on the semiconductor substrate surface, electrons move to the adsorbed chlorine atoms to form CQ-,
It is thought that the etching reaction will eventually volatilize as 5iCAx. Examples of such research are described on page 46 of the Abstracts of the 22nd Summer Seminar of the Spectroscopic Society of Japan.

[Problem that the invention seeks to solve]

However, as semiconductors become more highly integrated and the need to etch and deposit patterns as fine as the wavelength of light increases, the processing limitations of surface treatment using optical excitation have become the biggest problem.

Therefore, it is an object of the present invention to provide a method for surface treatment of ultra-fine patterns that can perform etching and deposition at submicron level or less, which is difficult to achieve with the above-mentioned surface treatment using optical excitation.

Another object of the present invention is to provide a surface treatment method that enables the formation of the ultra-fine pattern described above by injecting electrons into a substrate to be processed without evacuating one reaction chamber to an ultra-high vacuum.

[Means for solving problems]

The above object is achieved by bringing a conductive probe very close to the surface of a substrate to be processed in a reactive gas atmosphere and causing a tunnel current to flow between the substrate to be processed and the probe.

[Effect]

A tunnel current flows strongly between the most protruding atom at the tip of the probe and the nearest atom on the substrate surface.

Electrons are preferentially injected onto the substrate surface through which the tunnel current flows. As a result, one reactive gas is locally activated, making it possible to draw ultra-fine etching patterns and deposition patterns.

〔Example〕

Hereinafter, one embodiment of the present invention will be explained with reference to FIG. 1. In FIG. 1, 1 is a reaction chamber, 2 is a substrate to be processed, 3 is an etching gas introduction pipe containing a halogen element, 4 is an exhaust pipe, and 5 is a The conductive probe 6 is a tunnel current amplifier and display device. Etching gas? If you do it, pressure 1! By the action of the actuator (not shown), the distance between the substrate 2 to be processed and the conductive probe 5 is
Bring it close to about 11. A bias voltage of 1 mV to several V is applied between the probe 5 and the substrate 2 to be processed, so that a tunnel current flows between the two. Etching gas is introduced from the primary etching gas introduction tube 3, resulting in a 1-channel etching process. The etching gas is activated in the micro-space region where the current flows and etches the substrate to be processed. In the above description, the process procedure is described in which the etching gas is introduced while a tunnel current is flowing, but the process is not limited to this procedure.

For example, as a second step, an etching gas may be introduced into the reaction chamber 1, and then, after the reaction chamber 1 is evacuated, the conductive probe 5 may be brought close to the substrate 2 to be processed to cause a tunnel current to flow therethrough. In this case, the etching gas adsorbed on the substrate 2 to be processed is activated and the etching reaction progresses.

In addition, as a third step, an etching gas is introduced into the reaction chamber 1, and then the supply and exhaust of the gas are stopped, and the probe 5 is brought close to the substrate 2 to be processed in a static state to generate a tunnel current. In order to cause a tunnel current to flow between the probe 5 and the substrate 2 to be processed, it is necessary to maintain a gap of about 1+gm between the probe 5 and the substrate 2 to be processed. Therefore, it is necessary to have a means to remove vibrations from the experimental system, but at the same time, even when the etching gas is flowed into the reaction chamber to proceed with the process, it is necessary to flow a tunnel current in a static state. From this point of view, among the above three procedures, procedure 2 or procedure 3 is more suitable.

FIG. 2 shows a second embodiment of the present invention, which is characterized by the addition of optical excitation means for activating the etching gas. In the figure, 7 is a light source, 8 is a light beam, and 9 and 10 are light transmission windows provided in the reaction chamber 1. This method is effective as a means for increasing the etching rate in a system where the substrate 2 to be processed is P-type or additive-free silicon, and the etching gas is chlorine. In this system, for example, a light source such as a XeCQ excimer laser that emits light in the absorption band region of chlorine gas is used as the light source 7.

As shown in FIG. 2, the light beam 8 must be passed horizontally very close to the substrate surface and must not directly illuminate the substrate surface. Therefore, a laser is suitable as the light source 7. This is because when light hits the surface of the substrate, hole-electron pairs are formed in that area and the etching reaction progresses. Therefore, in order to perform etching of ultra-fine parts, conditions in which the light beam 8 is reflected by the probe 5 and the reflected light hits the substrate surface are also undesirable.

In this system, chlorine gas is activated near the substrate 2 to be processed by a photoexcitation reaction. On the other hand, a tunnel current flows between the substrate 2 to be processed and the probe 5, and electrons move to chlorine radicals that are adsorbed or approached in the minute region where the tunnel current flows. the result,
The etching reaction progresses in minute areas on the order of angstroms or nanometers. In the embodiment shown in FIG. 2, a large amount of chlorine radicals are formed by the light irradiation from the light source 7, so that the etching rate is significantly improved compared to the embodiment shown in FIG.

FIG. 3 shows a third embodiment of the present invention, which is characterized in that a discharge means is used to activate the etching gas.

In FIG. 3, numeral 11 is a discharge section, which can utilize microwave discharge, high frequency discharge, etc.

Etching gas, for example chlorine gas, is activated in discharge section 11 and then passed through ion collector 12 provided in etching gas introduction tube 3 and introduced into reaction chamber 1 . On the other hand, since a tunnel current flows between the substrate 2 to be processed and the probe 5, the etching reaction of minute parts on the angstrom order or nanometer order progresses as in the embodiment shown in FIG. In the embodiment shown in FIG.
Since a large amount of chlorine radicals are formed and introduced into the reaction chamber 1, this method is effective as a measure for improving the etching rate, similar to the embodiment shown in FIG.

Incidentally, pine cord (M, A) is an example close to the present invention.

There is a paper by McCord et al. (Journal of
Vacuum Science and Technology, 84
Volume, No. 1, Page 86, 1986; J, Vac,
Sci.

Technol, B4 (1), 86. (19
86) -) In the embodiments shown in FIGS. 1 to 3, the probe 5 was installed in the reaction chamber 1, but in this system, the probe 5 itself is etched together with the substrate 2 to be processed.

In order to suppress this, it is suitable to separate the etching gas introduction chamber from the processing chamber (probe installation chamber) in which the tunnel current flows. In this case, the etching gas may be adsorbed onto the substrate 2 to be processed in the etching gas introduction chamber, and then the substrate 2 to be processed may be transferred to the processing chamber, and then a tunnel current may be applied. However, in this case, the substrate to be processed 2
An ultra-thin layer of 1-2R layers on the surface will be etched.

Furthermore, when a pulsed light source is used as the light source 7, such as the X e CQ excimer laser shown in the embodiment of FIG. 2, the etching gas is activated in accordance with the repetition frequency and furthermore the pulse width. therefore.

In order to efficiently etch the substrate 2 to be processed, a tunnel current may be caused to flow between the substrate 2 and the probe 5 in synchronization with the irradiation of the light beam 8. As means for synchronizing the tunnel current, there are a method of controlling the applied voltage and a method of varying the distance between the substrate 2 to be processed and the probe 5.

Although the above explanation is all related to the ultra-fine dry etching method, it can also be applied to a method for depositing a film in an ultra-fine area without almost changing the apparatus configuration and steps shown in the description of the above embodiments. can. In that case,
As the gas introduced into the reaction chamber, a gas for forming a film (for example, a silane gas, an organic metal compound gas, a metal carbonyl gas, an organic monomer gas for forming a polymer film, etc.) may be used.

However, in the present invention, since the conductive probe is exposed to an etching gas atmosphere, it is easily corroded, and accordingly, there arises a problem that the probe must be replaced frequently. However, this problem can be significantly alleviated by forming the conductive probe from a corrosion-resistant material. Such corrosion-resistant materials include gold, platinum, tantalum, titanium, niobium, zirconium, nickel, tungsten, molybdenum, alloys containing any of the above metals from gold to molybdenum, and iron-based materials. Materials such as complex boride-based hard sintered alloys or so-called synthetic metals containing conductive polymer materials are suitable.

The entire conductive probe used in the present invention may be made of such a corrosion-resistant material, but it may also be in a form in which only the surface layer that comes into contact with the etching gas is coated with a corrosion-resistant material. In the latter case, the interior material coated with a corrosion-resistant material can be formed from a conductive material or a non-conductive material such as glass, which is susceptible to corrosion when in contact with the etching gas.

〔Effect of the invention〕

According to the present invention, an ultra-small region (
Dry etching and deposition in the angstrom range to nanometer range can be performed. Also,
This has the advantage that there is no need to introduce ultra-high vacuum exhaust equipment, which is essential for realizing ordinary electron beam utilization equipment.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of an apparatus showing a first embodiment of the present invention;
FIG. 2 is a schematic configuration diagram of an apparatus showing a second embodiment of the present invention;
FIG. 3 is a schematic configuration diagram of an apparatus showing a third embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Reaction chamber, 2... Substrate to be processed, 3... Etching gas introduction pipe, 4... Exhaust pipe, 5... Probe, 6...
...Amplifier and display device, 7...Light source, 8...Light beam, 9.10...Light transmission window, 11...Discharge part, 1
2...Ion collector. Length 1m

Claims (1)

[Claims] 1. A step of introducing a reaction gas into a reaction chamber containing a substrate to be processed, a step of bringing a conductive probe close to the substrate to be processed, and activating the reaction gas. An ultra-fine surface treatment method comprising the step of flowing a tunnel current between the substrate to be treated and the conductive probe. 2. The ultrafine surface treatment method according to claim 1, wherein a gas containing a halogen element is used as the reaction gas. 3. The ultrafine surface treatment method according to claim 1 or 2, characterized in that a semiconductor substrate is used as the substrate to be treated. 4. The ultrafine surface treatment method according to claim 2, wherein a chlorine atom-containing gas is used as the reaction gas. 5. The ultrafine surface treatment method according to claim 3, wherein P-type or additive-free silicon is used as the substrate to be treated. 6. The ultrafine surface treatment method according to claim 1, further comprising a light irradiation step as the reaction gas activation step. 7. The ultra-fine surface treatment method according to claim 6, characterized in that a laser is used as the light irradiation means. 8. The ultra-fine surface treatment method according to claim 6 or 7, characterized in that the light beam emitted from the light irradiation means is passed parallel to the surface of the substrate to be processed. 9. The light beam emitted from the light irradiation means is pulsed, and the tunneling current is caused to flow in synchronization with the pulse, according to any one of claims 6 to 8. ultra-fine surface treatment method. 10. The ultrafine surface treatment method according to claim 1, characterized in that a discharge step is further used as the step of activating the reaction gas. 11. A discharge unit for activating the reaction gas is provided outside the reaction chamber, and the reaction gas activated by the discharge is introduced into the reaction chamber. Ultra-fine surface treatment method. 12. The ultrafine surface treatment method according to claim 10 or 11, characterized in that charged particle supplementation means is provided between the discharge section and the reaction chamber. 13. Claims 1 to 1, characterized in that a step of flowing the tunneling current is provided after the step of introducing the reaction gas into the reaction chamber and the step of exhausting the reaction gas. Ultrafine surface method according to item 5. 14. A patent claim characterized in that a chamber in which the reaction gas is adsorbed onto the substrate to be processed is separated from a processing chamber in which a reaction between the substrate to be processed and the reaction gas is induced by flowing the tunnel current. The ultrafine surface treatment method according to any one of items 1 to 5. 15. After introducing the reaction gas into the reaction chamber, the introduction and exhaust of the reaction gas are stopped, and the tunnel current is allowed to flow in a static state. The ultra-fine surface treatment method according to any one of the above. 16. The conductive probe may be made of gold, platinum, tantalum, titanium, niobium, zirconium, nickel, tungsten, molybdenum, an alloy containing any of the above metals from gold to molybdenum, or an iron-based material. A probe made of a corrosion-resistant material selected from the group consisting of a complex boride-based hard sintered alloy or a so-called synthetic metal containing a conductive polymer material is used. The method for ultrafine surface treatment according to any one of items 1 to 15. 17. The ultra-fine surface treatment method according to claim 16, wherein a probe whose surface is coated with the corrosion-resistant material is used as the conductive probe.