JPH056879A - Dry etching method - Google Patents

Abstract

PURPOSE:To provide a dry etching method wherein the verticality of an etched shape is good and the controllability of an etched width is excellent because the etched bottom face is smooth and a side-etched amount is small. CONSTITUTION:An InP substrate 1 is irradiated with an argon ion beam 3 and chlorine molecules 6 as well as, at the same time, a hydrogen ion beam 4 and hydrogen radical atoms 5; an electron exhaustion layer 7 is formed entirely around the surface of a semiconductor. The chlorine molecules 6 which have adhered to the etched bottom are dissociated by the ion assistance effect of the argon ion beam 3; they are reacted with indium atoms as a substrate constitutent element; they form a chlorine; they are disconnected. The chlorine molecules 6 on the side face cannot be dissociated because the electron exhaustion layer is formed also on the side face and it is not irradiated with the argon beam 3; an etching operation does not progress. Consequently, a side etching operation is not caused by a reactive gas, and an etching operation whose verticality is good and whose controlling of an etched width is high can be performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor dry etching method using an excitation beam and a reactive gas.

[0002]

2. Description of the Related Art A dry etching method for a compound semiconductor using a reactive gas and an ion beam as an excitation beam has been conventionally known, and an example thereof has been reported by Yoshikawa et al. Proceedings of the Physical Society of Japan 31
p-K-6). In this dry etching method,
The sample substrate is irradiated with argon ions vertically, and chlorine gas is supplied from the nozzle as a reactive gas at the same time, and the InP substrate is etched by the ion beam excitation.

[0003]

However, in the above-described conventional dry etching method, although a smooth etching bottom surface can be obtained at a substrate temperature of about 200 ° C. or higher, the side etching amount by gas etching is large and the vertical etching shape However, there is a problem that the etching width is difficult to control and the etching width is difficult to control. Further, when the substrate temperature is lowered to about 100 ° C., side etching is suppressed and verticality is obtained, but there is a problem that the etching bottom surface becomes rough.

An object of the present invention is to provide a dry etching method in which the etching bottom surface is smooth and the side etching amount is small, so that the verticality of the etching shape is good and the control of the etching width is excellent.

[0005]

SUMMARY OF THE INVENTION The present invention provides a method for dry etching a semiconductor using an excited beam and a reactive gas, wherein a semiconductor surface modifying species containing at least either hydrogen ion or hydrogen radical atom is used. This is a dry etching method characterized by comprising a step of forming an electron depletion layer in the vicinity of the semiconductor surface by irradiation and suppressing gas etching on the side surface.

[0006]

When the semiconductor substrate is irradiated with ions or radical atoms such as hydrogen, these atoms are injected near the surface of the semiconductor substrate and trap electrons in the semiconductor. Therefore, an electron depletion layer is formed near the surface of the semiconductor substrate. On the other hand, in gas etching using a reactive gas such as chlorine gas, the reactive gas molecules attached to the semiconductor substrate receive electrons from the substrate, dissociate into negative ions and radical atoms, and react with the substrate constituent atoms to perform etching. Progresses.

According to the dry etching method of the present invention,
Since an electron depletion layer is uniformly formed in the vicinity of the semiconductor surface during etching, the reactive gas molecules attached to the semiconductor substrate cannot be dissociated only by thermal energy. At this time, the reactive gas molecules are dissociated by ion excitation at the bottom portion irradiated with the ion beam and etching proceeds, but the reactive gas molecules cannot be dissociated at the side where the ion beam is not hit so that etching does not proceed. .. Therefore, an etching shape with good verticality can be obtained, and the etching width can be uniformly controlled.

[0008]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a schematic diagram for explaining an embodiment of the present invention.

In this embodiment, an ion beam assisted etching (IBAE) is used in which an inert gas ion is used as an excitation beam and a reactive gas is supplied in a molecular state for etching.
The method was used. An InP substrate 1 was used as a semiconductor substrate, and a Sio ₂ film processed into a stripe shape by a photolithography method was used as an etching mask 2. EC
R (Electron Cyclotron Reso
Argon (Ar) as an inert gas and hydrogen (H ₂ ) as a semiconductor surface modifying species are introduced into the plasma chamber to generate plasma, which is accelerated by the extraction electrode to accelerate the argon ion beam 3 and the hydrogen ion beam 4. Is irradiated onto the substrate. At this time, the hydrogen radical atoms 5 reach the substrate by diffusion. Chlorine gas was used as the reactive gas, and the substrate was irradiated with chlorine molecules 6 from a nozzle near the substrate. As an example of the etching conditions, an acceleration voltage of about 500V, a chlorine gas pressure of about 8 × 10 ^{- 4} Torr, a substrate temperature of about 200 ° C. when etching rate - DOO smooth etching bottom is obtained in about 1 [mu] m / min. At this time, since the hydrogen ion beam 4 and the hydrogen radical atom 5 are irradiated on the bottom surface and the side surface of the etching, the electron depletion layer 7 is formed in the whole vicinity of the semiconductor surface. The chlorine molecule 6 attached to the etching bottom surface is dissociated by the ion assist effect of a large mass of argon ion beam and reacts with the indium (In) atom which is a constituent element of the substrate to form an indium chloride to be desorbed. On the other hand, the chlorine molecule 6 is also irradiated on the etching side surface, but the electron depletion layer is also formed on the side surface, and since the argon ion beam 3 is not directly irradiated, the chlorine molecule 6 cannot be dissociated and the etching does not proceed. Therefore, side etching due to the reactive gas does not occur, verticality is excellent, and etching with high controllability in which the etching width is determined only by the mask width becomes possible.

The hydrogen atoms used for forming the electron depletion layer are easily desorbed from the semiconductor by heating the substrate to about 400 ° C. or higher after etching, so that the electron depletion layer 7 can be eliminated. .. Therefore, even if the electron depletion layer 7 formed during the etching process impairs subsequent process steps or deteriorates the device characteristics, it can be easily avoided by the heat treatment step.

In the above embodiment, the ion beam assisted etching (IBAE) method was used as the etching method, but the present invention is not limited to this, and the present invention is also applicable to other dry etching methods such as electron beam excited etching and photoexcited etching. Is applicable.

In the above embodiment, the semiconductor substrate to be etched is InP, but the present invention is not limited to this, and the present invention can be applied to other semiconductor substrates such as GaAs.

In the above embodiment, argon was used as the inert gas ion species and chlorine was used as the reactive gas species, but the present invention is not limited to this. For example, other elements such as xenon (Xe) may be used as the inert gas ion species. The present invention can be applied even when the active gas is a halogen element such as bromine (Br) or iodine (I) as the reactive gas species.

Although hydrogen is used as the semiconductor surface modifying species in the above embodiments, the present invention is not limited to this, and other atoms such as deuterium capable of forming an electron depletion layer near the semiconductor surface may be used. The present invention can also be applied.

[0015]

As described above, according to the present invention, since the side etching amount is small, the verticality of the etching shape is good, and the dry etching with the excellent controllability of the etching width can be performed.

[Brief description of drawings]

FIG. 1 is a schematic diagram for explaining an embodiment of the present invention.

[Explanation of symbols]

 1 InP substrate 2 Etching mask 3 Argon ion beam 4 Hydrogen ion beam 5 Hydrogen radical atom 6 Chlorine molecule 7 Electron depletion layer

Claims (1)

Claim: What is claimed is: 1. A method for dry etching a semiconductor using an excited beam and a reactive gas, which comprises irradiating a semiconductor surface modifying species containing at least either hydrogen ion or hydrogen radical atom. Thus, the dry etching method is characterized in that the method has a step of forming an electron depletion layer in the vicinity of the semiconductor surface and suppressing gas etching on the side surface.