JPH0464225A - Manufacturing method of semiconductor device - Google Patents

Abstract

PURPOSE:To obtain high pattern accuracy by adsorbing the chlorine of of several atomic layers onto a surface, selectively irradiating the surface with electron beams, selectively desorbing adsorbed chlorine atoms on the surface, forming a volatile silicon chloride through the irradiation of ultraviolet rays in a vacuum and desorbing the silicon chloride into a vacuum. CONSTITUTION:Chlorine gas is introduced into a vacuum device 4, and an adsorbed chlorine atomic layer 6 is formed on the surface of a silicon substrate 1. Regions 11 not etched on the surface of the substrate 1 are irradiated with electron beams 8. Consequently, adsorbed chlorine is desorbed into a vacuum from the regions 11 not etched, and the surface of the silicon substrate 1 is exposed. The whole surface of the substrate 1 is irradiated with ultraviolet rays 9 in a vacuum. As a result, a volatile silicon compound 7 is formed by the reaction of the atomic layer 6 and the substrate 1, and desorbed into the vacuum. Accordingly, the substrate 1 in the peripheries of the regions 11 is etched. The process is repeated, thus allowing etching in specified thickness with high accuracy.

Description

[Detailed description of the invention] 〔overview] Concerning a dry etching method for the surface of a semiconductor substrate.

The purpose of this invention is to enable dry etching of the surface of a semiconductor substrate without using a resist containing organic substances and without causing damage due to ion bombardment.

A reactive substance is adsorbed on a cleaned surface of a semiconductor substrate, and a predetermined region of the surface is irradiated with an electron beam having a quantum energy within a range that does not cause a reaction between the reactive substance and the surface. The semiconductor from which the reactive substance has been removed is exposed to ultraviolet light having a quantum energy in a range capable of removing the reactive substance from the predetermined region and causing a reaction between the adsorbed reactive substance and the surface. The method includes steps of etching the semiconductor substrate around the predetermined region by irradiating the entire surface of the substrate.

(Industrial Application Field) The present invention relates to a method for dry etching the surface of a semiconductor substrate.

[Conventional technology]

Dry etching has become essential in order to form fine patterns with high precision necessary for increasing the speed and integration of semiconductor devices. Further, a resist layer made of a photosensitive organic material is used as a mask in the dry etching.

[Problems to be Solved by the Invention] As a result, contamination by resist remaining on the surface of the semiconductor substrate, decomposition products of the resist, and impurities such as sodium contained in the resist cannot be avoided.

Furthermore, in dry etching, there is a problem in that the surface of the semiconductor substrate is damaged by accelerated ions.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method capable of etching a semiconductor substrate with high precision without causing contamination or ion damage caused by using a resist as described above.

[Means to solve the problem]

The above purpose is to adsorb a substance that is reactive with the surface onto a cleaned surface of a semiconductor substrate, and to use a quantum energy within a range that does not cause a reaction between the adsorbed reactive substance and the surface. selectively irradiating a predetermined region of the surface with a first beam of electromagnetic waves having a first electromagnetic wave beam to remove the reactive substance from the predetermined region; and causing a reaction between the adsorbed reactive substance and the surface. Etching the semiconductor substrate around the predetermined region by irradiating the entire surface of the semiconductor substrate from which the reactive substance has been selectively removed as described above with a second electromagnetic wave having a quantum energy in a range that can be generated. This is achieved by a method for manufacturing a semiconductor device according to the present invention, which is characterized by including the steps of:

[Function] For example, the surface of a silicon substrate from which an oxide film has been removed by heating in a vacuum is exposed to a chlorine gas atmosphere, and several atomic layers of chlorine are adsorbed onto the surface. A predetermined region of the silicon substrate that is not etched is selectively irradiated with an electron beam of 100 to several 100 eV to selectively remove adsorbed chlorine atoms from the surface of this region. Thereafter, by irradiating the substrate surface with vacuum ultraviolet light, the remaining adsorbed chlorine atoms react with the silicon substrate to generate volatile silicon chloride, which is released into vacuum. In this way, the silicon substrate around the predetermined region is etched.

The above method has the following first-order advantages.

■ Etching of a silicon substrate is possible without using a resist mask.

(2) Pattern accuracy of resist mask is not required; (1) Higher pattern accuracy than in normal electron beam exposure method can be obtained.

■Since accelerated ions of reactive gas are not used, there is no damage to the silicon substrate.

(2) A phosphorography process related to the production of an exposure mask, the formation of a resist mask, etc. is omitted.

〔Example] Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a process explanatory diagram of an embodiment of the present invention.

That is, 1.Similar to normal surface treatment, silicon substrate 1 is immersed in dihydrofluoric acid (HF), boiled in a mixed solution of nitric acid (HNO3) and hydrogen peroxide (H20□), and treated with aqueous ammonia (NH , OH) and H20□ were repeated, and finally, hydrochloric acid ()IcI) and H20
By boiling in a mixed solution with □, an oxide film 3 with a thickness of about 10 mm is formed on the surface, as shown in FIG.

Next, as shown in the same figure (b), the ultimate vacuum degree is 1X
After placing the silicon substrate 1 in an ultra-high vacuum device 4 at a temperature of 10-” Torr or less, the silicon substrate 1 is heated to approximately 800°C by a heater 5.
Heat under vacuum for 30 minutes. As a result, the oxide film 3 on the surface of the silicon substrate 1 is removed and a clean surface is exposed.

Next, heating by the heater 5 is stopped, and the silicon substrate 1 is heated.
After returning the temperature to room temperature, chlorine gas is introduced into the vacuum device 4, as shown in FIG. 4(C). This introduction
The partial pressure of chlorine in the reactor was controlled to be I Torr, and the test was carried out for 100 seconds. As a result, an adsorbed chlorine atomic layer 6 is generated on the surface of the silicon substrate 1.

The thickness of the adsorbed chlorine atom layer 6 is as shown in FIG.

It is controlled by the partial pressure of chlorine gas and the introduction time. The horizontal axis in Figure 2 is the Langmuir unit (L; IL = I Xl0-bT
The amount of chlorine introduced is expressed in (orr・5ec), and the vertical axis is
It is the amount of chlorine adsorption (number of atomic layers). From the same figure, the above I To
It can be seen that approximately 2 atomic layers of chlorine are adsorbed on the surface of the silicon substrate 1 on average based on the amount of chlorine introduced for 100 seconds at rr, that is, 10''L.

Referring again to FIG. 1, as shown in FIG. 1(d), an unetched region 11 on the surface of the silicon substrate 1 is selectively irradiated with a 5 KeV electron beam 8 for 10 seconds.

As a result, the adsorbed chlorine leaves the non-etched region 11 into the vacuum and the surface of the silicon substrate 1 is exposed.

Next, as shown in FIG. 4E, the gold body on the surface of the silicon substrate 1 is irradiated with vacuum ultraviolet light 9 having a wavelength of 2537. As a result, a volatile silicon compound 7 such as + S I Cl 31 S s C1a is generated by the reaction between the adsorbed chlorine atom layer 6 and the silicon substrate 1, and is released into the vacuum. In this way, the silicon substrate 1 around the area 11 that is not etched is etched. As aforementioned,
Two atomic layers of chlorine are adsorbed by the introduced amount of 10"L. Therefore, assuming that this adsorbed chlorine reacts with the silicon substrate 1 to produce 5iC14, 172 atoms of the silicon substrate 1 are absorbed by one introduction of chlorine gas. The thickness equivalent to the thickness of the layer will be etched.

Therefore, by repeating the steps shown in FIGS. 1(C) to 1(e), it is possible to perform etching to a predetermined thickness with high precision. Further, the lateral dimension of the region 11 that is not etched is determined by the irradiation accuracy of the electron beam 8. Therefore, higher accuracy can be obtained than when using a resist mask patterned by electron beam exposure.

FIG. 3 shows the Auger electron spectrum of the surface of the silicon substrate 1 on which chlorine has been adsorbed, and FIG. 4 shows the Auger electron spectrum of the silicon substrate 1 on which chlorine has been adsorbed and then irradiated with an electron beam. That is, FIG. 3 shows the surface immediately after the introduction of 108 L of chlorine, and a silicon peak appears at a position of 100 eV, and a chlorine peak appears at a position of 200 eν. Figure 4 shows that after the introduction of chlorine, the first
As shown in Figure (d), the surface is shown after being irradiated with the electron beam 8 at 5 eV, and the chlorine peak at 200 eV has disappeared, indicating that the adsorbed chlorine is removed by the irradiation with the electron beam 8. I understand that.

In the above example, electron beam irradiation was used to remove adsorbed chlorine atoms in the area not to be etched, and
Ultraviolet light was used to excite the reaction between the adsorbed chlorine atoms and the silicon substrate, but these can be used with other electromagnetic waves that can release the adsorbed chlorine atoms without causing a reaction with the silicon substrate, or with other electromagnetic waves that can excite the adsorbed chlorine atoms and the silicon substrate. There is no problem in replacing each of the other electromagnetic waves that can excite the reaction with ii. moreover.

It goes without saying that the process can also be carried out using a gas that is reactive with semiconductor substrates other than silicon substrates.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to dry-etch the silicon substrate surface without using a resist mask, and there is no organic contamination caused by the resist.
Furthermore, there is no risk of damage caused by ion bombardment, unlike in dry etching using normal accelerated ions. Furthermore, highly accurate etching is possible compared to normal electron beam exposure using a resist mask. By using a silicon substrate having a mesa-like region or an etched groove-like region formed according to the present invention, a semiconductor device such as a quantum wire can be realized. Furthermore, the lithographic process required for etching can be omitted, making it possible to reduce the number of manufacturing steps for semiconductor devices.

[Brief explanation of drawings]

FIG. 1 is a process explanatory diagram of an embodiment of the present invention. Figure 2 is a graph showing the relationship between the amount of chlorine introduced and the amount of chlorine adsorbed. Figure 3 shows the Auger electron spectrum of the silicon substrate surface on which chlorine has been adsorbed. FIG. 4 shows an Auger electron spectrum of the surface of a silicon substrate subjected to electron beam irradiation after chlorine adsorption. In fig. 1 is a silicon substrate, 3 is an oxide film. 4 is a vacuum device, 5 is a heater. 6 is an adsorbed chlorine atomic layer. 7 is a volatile silicon compound. 8 is an electron beam, 9 is a vacuum ultraviolet light. Reference numeral 11 indicates an area in which no engineering/nching is performed. #0'? R child, he is not talented, Kito P Moon Q real) Color I row / 71 years old U scout m Figure 1 (Zono 2) J4L 9 catty, Hekutoi Aunmei's real square color θ・1 Figure 1 (1001) Between the amount of chlorine introduced and the amount of chlorine A,

Claims (2)

[Claims] (1) A step of adsorbing a substance that is reactive with the surface onto a cleaned surface of a semiconductor substrate, and applying quantum energy within a range that does not cause a reaction between the adsorbed reactive substance and the surface. selectively irradiating a predetermined region of the surface with a beam of first electromagnetic waves having a first electromagnetic wave of 100 nm to remove the reactive substance from the predetermined region; and causing a reaction between the adsorbed reactive substance and the surface. etching the semiconductor substrate around the predetermined region by irradiating the entire surface of the semiconductor substrate from which the reactive substance has been selectively removed as described above with a second electromagnetic wave having a quantum energy in a range that can A method for manufacturing a semiconductor device, comprising the steps of: (2) The semiconductor according to claim 1, wherein the mesa of the semiconductor substrate is formed in the predetermined region by repeating adsorption of the reactive substance, irradiation with the first electromagnetic wave beam, and irradiation with the second electromagnetic wave. Method of manufacturing the device.