JPH04343223A - Semiconductor surface etching method - Google Patents

Abstract

PURPOSE:To obtain a semiconductor surface etching method with which a film is removed with a high film thickness-controllability in a clean atmosphere. CONSTITUTION:In a substrate-surface etching method wherein semiconductor substrates 4 and 10 are heated up to the prescribed temperature under high vacuum, ultraviolet rays or vacuum ultraviolet rays are made to irradiate on the surface of the substrates, amorphous materials 11 and 14 are selectively etched taking advantage of high etching speed comparing with crystal material, and a pattern is characteristically formed. Besides, the above-mentioned etching is charactistically conducted while the semiconductor substrate surface is being exposed to hydrogen gas in this semiconductor surface etching method.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor surface etching method as a method for removing a film with high film thickness controllability in a clean atmosphere.

0002

2. Description of the Related Art In order to accurately etch the surface of a semiconductor material, it is necessary to rely on a dry etching method carried out in a vacuum chamber. In methods such as sputtering and reactive ion etching, in which ion species generated by ECR plasma or RF discharge are accelerated and incident on the substrate surface for etching, the energy of the incident particles is high, making it difficult to precisely control the etching depth. It is difficult and causes a lot of damage to the surface. Naturally, no difference in etching rate is observed for materials with different crystallinity. On the other hand, in the so-called photoexcited etching method using ultraviolet or vacuum ultraviolet light irradiation, the kinetic energy of reactive species is low, so the proportion of the physical sputtering process is very small, and damage is small. Until now, SF6 has been mainly used as the reaction gas, but in this case there is no reaction selectivity between amorphous and crystalline materials. Machining surfaces at the atomic layer level requires a soft process that leaves no contaminants in a highly clean environment. However, such a method has not been known until now.

0003

SUMMARY OF THE INVENTION An object of the present invention is to provide a semiconductor surface etching method for removing a film with high film thickness controllability in a clean atmosphere.

More specifically, the object of the present invention is to provide an etching method in which a semiconductor substrate is heated to a predetermined temperature in a high vacuum, and the surface of the substrate is irradiated with ultraviolet or vacuum ultraviolet light to etch the surface of the substrate. By providing a semiconductor surface etching method characterized by selectively etching an amorphous material to form a pattern by taking advantage of the fact that an amorphous material has a faster etching speed than a crystalline material. be.

Another object of the present invention is to provide a semiconductor surface etching method characterized in that the semiconductor surface etching method is carried out while exposing the surface of the semiconductor substrate to hydrogen gas.

[0006]

[Means for Solving the Problems] Short wavelength ultraviolet light or vacuum ultraviolet light is used as an excitation source. In general, photoreactions have the advantage of high material selectivity, but as shown in the section on action, the present invention effectively utilizes differences in the rate of photostimulated desorption due to differences in crystallinity. . In particular, the use of synchrotron radiation allows for high spatial resolution and allows for processing without the use of reactive gases. In addition, synchrotron radiation is highly effective to use because of its high brightness and straight-line propagation. Further, when hydrogen gas is used as the etching gas, the etching rate is further increased. For example, when a Si or Ge substrate is irradiated with ultraviolet or vacuum ultraviolet light in a hydrogen gas atmosphere of about 0.1 Torr, hydrogen molecules in the gas phase are photoionized and dissociated into hydrogen atoms with an energy of several eV. Since atomic hydrogen is highly reactive, it covers part of the outermost surface of Si and Ge. On the other hand, due to the high gas phase pressure, the surface of the substrate is partially covered with molecular hydrogen, which is dissociated by light irradiation. Eventually, an adsorption layer of SiHx or GeHX is formed on the outermost surface, and the bond with the underlying bulk atoms is weakened. The speed at which the adsorption layer in the irradiated area is photodesorbed by light irradiation largely depends on the crystallinity of the material, and is overwhelmingly faster in an amorphous film than in a crystalline film. By utilizing this fact, it is possible to selectively remove only the amorphous film. Furthermore, since this reaction process proceeds on the outermost surface, it essentially has the property of removing the film on the order of atomic layers.

The configuration of the present invention is shown below. That is, the present invention provides an etching method in which the semiconductor substrate (4, 10) is heated to a predetermined temperature in a high vacuum, and the surface of the substrate is irradiated with ultraviolet or vacuum ultraviolet light to etch the surface of the substrate. Crystalline material (11, 14) is crystalline material (10)
This method is a semiconductor surface etching method characterized by selectively etching the amorphous material (11, 14) to form a pattern by utilizing the fact that the etching speed is faster than that of the method. Alternatively, the semiconductor substrate surface (4
, 10) is performed while being exposed to hydrogen gas. Alternatively, in the present invention, a Si substrate (10) is prepared, and the Si substrate (10) is prepared.
Silane gas is introduced onto the i-substrate (10) at a temperature below 500°C to increase the thickness of the amorphous Si layer (11) to the desired quantum wire (
13) A first step of depositing to match the thickness of
Alternatively, using a VUV light mask (12), the introduction pressure is 0.
Synchrotron radiation was irradiated at 700°C in a hydrogen gas atmosphere of 1 Torr to form amorphous Si at the mask opening.
The second step involves removing the layer and controlling the etching to stop at the Si substrate interface, and then introducing a metal hydride gas for the metal layer (13) and irradiating the mask opening with light to remove the metal layer (13). A third step of selectively growing a quantum wire structure, a fourth step of depositing an amorphous Si layer (14) as an upper layer to cover the quantum wire structure (13), and further heating to 900° C. to form an amorphous Si layer (14). Si layer (11,
It has a structure as a semiconductor surface etching method including a fifth step of polycrystalizing the portion 14) to impart etching resistance.

[0008]

[Function] Below, we will describe the optically stimulated desorption of amorphous Si by vacuum ultraviolet light and the effect of promoting its etching by introducing hydrogen gas. FIG. 3 shows the substrate temperature dependence of the etching rate of amorphous Si by irradiation with synchrotron radiation. White circles are in ultra-high vacuum, black circles are 0.1
Each was obtained by irradiating synchrotron radiation from the direction perpendicular to the surface under a hydrogen gas atmosphere of Torr. The wavelength of the emitted light is 1 to 1000 Å, and the peak wavelength is 100 Å. Even under ultra-high vacuum, the amorphous Si in the irradiated area is etched by synchrotron radiation. However, with the introduction of hydrogen gas, the etching rate doubled. The reason why a peak is observed in the substrate temperature dependence of the etching rate is that when the temperature becomes too high, amorphous Si gradually crystallizes and the reactivity decreases. This state can be monitored by reflection high-speed electron diffraction. As can be seen from the figure, for example, at 720°C under a hydrogen atmosphere of 0.1 Torr,
Although the reaction rate is low at 1 atomic layer/2 minutes at a ring current of 300 mA, this means that processing with high film thickness accuracy is possible in a clean environment.

[0009]

EXAMPLES Examples of the surface etching method of the present invention will be described below. FIG. 1 shows an example of the configuration of an etching apparatus as an embodiment of the surface etching method of the present invention. 1 is a reaction vessel with ultra-high vacuum specifications, and 2 is a vacuum exhaust port. 3 is a substrate holder on which a Si or Ge substrate 4 can be fixed and heated from behind by a heater 5. Ultraviolet or vacuum ultraviolet light is introduced from the light introduction port 6, and hydrogen gas is introduced from the reaction gas introduction port 7, respectively.

A method for creating a quantum wire structure with a thickness of several tens of angstroms using this apparatus will be explained with reference to FIG.

A Si substrate 10 is prepared, and an amorphous Si layer 11 is deposited on the Si substrate 10 using silane gas at 500° C. or lower. The film thickness is made to match the desired thickness of the quantum wire (step 1).

[0012] Applying a mask 12 for UV or VUV light, heat at 700° C. in a hydrogen gas atmosphere with an introduction pressure of 0.1 Torr.
When synchrotron radiation is irradiated, the amorphous Si layer only in the openings of the mask 12 is removed. Base S
Once the surface of the i-substrate 10 has been etched, the etching rate rapidly decreases, making it possible to stop the etching at the interface of the Si substrate 10 with good controllability (step 2).
).

Furthermore, while irradiating the metal hydride gas for the metal layer 13 with light into the opening of the mask 12, the metal layer 13 is
3 is selectively grown to form a quantum wire structure (Step 3)
. An amorphous Si layer 14 is deposited on top to cover the quantum wire structure (step 4).

Further, when this is heated to 900° C., the amorphous Si layer (11, 14) becomes polycrystalline Si 15 and has etching resistance (step 5).

In this way, a single quantum wire structure (13) embedded in the polycrystalline Si 15 is created. To obtain a multilayer structure, steps 1-5 above may be repeated.

[0016]

[Effect of the invention] The present invention is characterized by utilizing the phenomenon that a large etching selectivity can be achieved even with the same material due to differences in crystallinity (amorphous is large and crystalline is small), which was not possible with conventional methods. Can be processed. Due to optical excitation, low-contamination and low-damage processing is possible, and it can be applied to the production of quantum effect devices. Hydrides with high vapor pressure are suitable for application. The most suitable light source is, for example, synchrotron synchrotron radiation, which is highly luminous and includes short wavelength components with good straightness. This is because synchrotron radiation is continuous, high-intensity light that includes short-wavelength components, so it can sufficiently energetically excite the electronic states of gas-phase molecules and atoms near the semiconductor surface. The use of short wavelength components is also advantageous for microfabrication of LSIs. Furthermore, if the processing dimensions are not very small and the target can be excited energetically, an excimer laser, for example, can be used as the excitation light source.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a reaction apparatus for carrying out an embodiment of the present invention.

FIG. 2 is a diagram showing a procedure for creating a quantum wire with a thickness on the order of angstroms using the present invention.

[Figure 3] Surface temperature dependence of desorption rate of amorphous Si upon irradiation with synchrotron radiation (white circles; under ultra-high vacuum; black circles; 0.1T
FIG.

[Explanation of symbols]

1 Reaction container 2 Vacuum exhaust port 3 Board holder 4 Board 5 Heater 6 Optical introduction port 7 Gas introduction port 10 Si substrate 11 Amorphous Si layer 12 UV and VUV light mask 13 Metal layer (quantum wire structure) 14 Amorphous Si layer 15 Polycrystalline Si

Claims (3)

[Claims] Claim 1: In an etching method in which a semiconductor substrate is heated to a predetermined temperature in a high vacuum, and the surface of the substrate is etched by irradiating ultraviolet or vacuum ultraviolet light, an amorphous material is converted into a crystalline material. A semiconductor surface etching method that is characterized by selectively etching amorphous materials to form a pattern by taking advantage of the fact that the etching speed is faster than that of amorphous materials. 2. The semiconductor surface etching method according to claim 1, wherein the etching is performed while exposing the surface of the semiconductor substrate to hydrogen gas. 3. A Si substrate is prepared, and 5 layers are placed on the Si substrate.
The first step is to deposit an amorphous Si layer by introducing silane gas at a temperature below 00°C to match the thickness of the desired quantum wire.
The process of irradiating synchrotron radiation at 700°C using a mask in a hydrogen gas atmosphere with an introduction pressure of 0.1 Torr removes the amorphous Si in the mask opening, and controls the etching to stop at the Si substrate interface. The second step is to form a quantum wire structure in which a metal layer hydride gas is introduced and the metal layer is selectively grown while irradiating light into the mask opening, and an amorphous Si layer is formed on the upper layer. Semiconductor surface etching comprising: a fourth step of depositing to cover the quantum wire structure; and a fifth step of heating to 900° C. to polycrystallize a portion of the amorphous Si layer to impart etching resistance. Law.