JPH0618187B2 - Semiconductor substrate processing method - Google Patents

Description

The present invention relates to a method for processing a semiconductor substrate, and more particularly to a method for processing a semiconductor substrate using a focused ion beam.

[Conventional technology]

A processing method using a focused ion beam with a liquid metal ion source is promising for future fine processing requiring a higher degree of fineness because the irradiation diameter can be made finer.

FIG. 4 is a sectional view of a processing apparatus including a semiconductor substrate for explaining a conventional method of processing a semiconductor substrate of this type.

This semiconductor substrate processing method begins with GaAs for processing.
A chlorine-containing reactive gas 50 such as Cl ₂ or SiCl ₄ is introduced into the etching chamber 40 in which the substrate 1a is arranged from the outside through a pipe, and then 10b from the liquid metal ion source.
The ion beam extracted from the laser beam is focused by a focusing lens system and irradiated onto the surface of the GaAs substrate 1a in the atmosphere of the reactive gas 50, and the GaAs substrate 1a is directly etched to form the etching groove 4a. It is an etching method.

[Problems to be solved by the invention]

The conventional semiconductor substrate processing method described above is a maskless etching method in which the surface of the GaAs substrate 1a is directly irradiated with the focused ion beam 11b for etching, so that the beam intensity of the focused ion beam 11b at the AA ′ cross section is obtained. Since the distribution is a Gaussian distribution type as shown in FIG. 5 (a), the upper side wall 42 of the entrance of the etching groove 4a is formed.
However, there is a drawback that a small amount of ion beam is irradiated and the corners of the upper side wall 42 are rounded and the verticality of the side wall of the etching groove 4a is impaired.

The sidewall vertical etching of the semiconductor substrate is highly necessary like the end face processing of a laser element, but it is realized by the conventional processing method using the focused ion beam as described above, particularly when a deep etching groove is formed. There was a problem that it was difficult.

An object of the present invention is to provide a method for processing a semiconductor substrate, which can easily form a deep etching groove without impairing the verticality of the side wall.

[Means for solving problems]

A method of processing a semiconductor substrate of the present invention comprises a step of forming an upper layer film of a predetermined material on a semiconductor substrate to be processed, and a step of forming a first gas and radicals for promoting a reaction on the upper layer film. A step of irradiating a focused ion beam from a first ion source while supplying one of them to perform etching to selectively form an opening in the upper layer film; and a step of forming a semiconductor substrate on the semiconductor substrate exposed in the opening. The focused ion beam from the second ion source is supplied while supplying one of the second gas and radicals, which has a high reactivity with the substrate and a low reactivity with the upper layer film. Irradiation and etching to form an etching groove having a predetermined depth.

[Action]

In the present invention, after the opening is formed in the upper layer film formed on the semiconductor substrate, the semiconductor substrate exposed in the opening has a high reactivity with the semiconductor substrate and does not react with the upper layer film. Since the focused ion beam is radiated while supplying gas or radical having sufficiently low reactivity, even the focused ion beam with Gaussian intensity distribution has sufficiently low reactivity with the upper layer film. Therefore, this upper layer film is not etched and serves as a mask layer, and since the reactivity with the semiconductor substrate is large, the etching is promoted, and even a deep etching groove can be easily formed without damaging the verticality of the side wall. be able to.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

1 (a) to 1 (c) are cross-sectional views of a semiconductor substrate and a processing apparatus shown in the order of processing steps for explaining an embodiment of the present invention.

As shown in FIG. 1 (a), Si is formed on the surface of the GaAs substrate 1.
An upper layer film ₂ of O ₂ or SiN ₂ is formed.

Next, as shown in FIG. 1B, the ion beam extracted from the liquid metal ion source 10 of Si is focused by a focusing lens system to irradiate the upper layer film 2 as a first focused ion beam 11.

In this case, it is possible to process by physical sputtering only by ion irradiation, but the etching rate is low. Therefore, the first reactive gas SiF ₄ is fed from the radical generation tube 20.
The focused ion beam 11 is radiated while supplying the gas 21 to perform etching efficiently, and the opening 3 is formed in the upper layer film 2.

Next, as shown in FIG. 1 (c), the ion beam extracted from the Ga liquid metal ion source 10a is focused by a focusing lens system to form a second focused ion beam 11a, which is exposed in the opening 3 of GaAs. Irradiate the substrate 1. At the same time, the reactive gas Cl ₂ is introduced into the radical generating tube 20a, and Cl radicals 2 are generated in the radical generating tube 20a by discharge or the like.
2 is generated, and the generated Cl radical 22 is supplied and adsorbed on the surface of the GaAs substrate 1 exposed in the opening 3.

This causes Cl radicals and G on the surface of the GaAs substrate 1.
Focused ion beam 11 irradiated with chemical reaction with aAs
Caused by a, etching is performed efficiently.

The change in the etching shape of the GaAs substrate 1 at this time is
Shown in the figure.

By irradiating the focused ion beam 11a of Ga while supplying the Cl radical 22 to the opening 3 of the upper layer film 2, the bottom portions 41a to 41c of the etching groove 4 become deeper one after another and the etching proceeds.

On the other hand, at this time, since the SiO ₂ or SiN ₂ the upper film 2 hardly reacts with Cl, the edge shape change unetched openings 3 by a small number of the ion beam irradiated to the edge of the opening 3 cause I don't.

Therefore, the upper layer film 2 serves as a mask layer, and the bottom portions 41a to 4a
Even if the etching of 1c progresses, the cross-sectional shape of the upper part of the sidewall of the etching groove 4 does not change and the verticality is maintained.

In this embodiment, the processing conditions for the upper layer film 2 are S
The focused ion beam of i was combined with the reactive gas of SiF ₄ , and the processing conditions of the GaAs substrate 1 were the focused ion beam of Ga and the Cl radical.

However, the present invention is not limited to this, and the processing conditions of the upper layer film 2 and the GaAs substrate 1 in other embodiments are not limited to this.
Table 1 shows the processing conditions.

In Example A, the upper layer 2 was processed only with Ga ⁺ beam, and the GaAs substrate 1 was processed with Cl ₂ gas or Cl _2.
It is a combination of a radical (symbol Gl ^{* in} Table 1) and a Ga ⁺ beam.

Hereinafter, in Example B, only the Si ⁺ beam on the upper film 2 side, G
The side of the aAs substrate 1 is Cl ₂ gas or Cl radicals and Si.
^In combination with ⁺ beam, in Example C, the upper film 2 side is S
A combination of iF ₄ gas and Ga ⁺ beam, a combination of Cl ₂ gas or Cl radical and Ga ⁺ beam on the GaAs substrate 1 side, a combination of SiF ₄ gas and Si ⁺ beam on the upper film 2 side in Example D, a GaAs substrate The first side is a combination of Cl ₂ gas or Cl radicals and Si ⁺ beam, and in Example E, the upper layer film 2 side is SiF ₄ gas and Si.
A combination of a ⁺ beam and a GaAs substrate 1 side is a combination of a Cl ₂ gas or a Cl radical and a Ga ⁺ beam.

FIG. 3 is a schematic view of a processing apparatus applied to the above embodiment.

First, the vapor deposition apparatus 31 is used to deposit SiO ₂ , S on the GaAs substrate 1.
An upper layer film ₂ such as iN ₂ is formed.

Next, the first device, which is connected to the vapor deposition device 31 through the vacuum path,
The GaAs substrate 1 is transported to the focused ion beam etching device 32, where the upper layer film 2 is etched by the focused ion beam to form the opening 3.

Next, again, the first focused ion beam etching device 32
And the GaAs substrate 1 is transported to the second focused ion beam etching device 33, which is connected to the first focused ion beam etching device 32 and has a different ion species from the first focused ion beam etching device 32, and the GaAs substrate 1 exposed at the opening 3 is focused. Etch with an ion beam.

The examples of these processing devices correspond to the embodiment E of Table 1, and when the ion species used for processing the upper layer film 2 and the GaAs substrate 1 are the same, at least one focused ion beam etching device is used. Good.

In the above embodiment, an example of processing the GaAs substrate 1 is shown, but other semiconductor substrates such as Si,
The same applies to InP, AlGaAs and the like.

〔The invention's effect〕

As described above, according to the present invention, after the opening is formed in the upper layer film formed on the semiconductor substrate, when the semiconductor substrate exposed in the opening is etched by the focused ion beam, the reactivity with the upper layer film is not increased. If the etching is performed while supplying gas or radicals that are sufficiently small and highly reactive with the semiconductor substrate, the upper layer film with the opening functions as a mask layer for preventing wear on the upper side wall, so that the vertical side wall of the etching side wall There is an effect that a deep etching groove can be easily formed without damaging the property.

Further, the present invention does not require patterning (lithography) of the resist mask, and therefore has an effect that the processing steps can be simplified.

[Brief description of drawings]

1 (a) to 1 (c) are sectional views of a semiconductor substrate and a processing apparatus shown in the order of processing steps for explaining an embodiment of the present invention, and FIG. 2 is a semiconductor processed by applying the present invention. FIG. 3 is a sectional view of a substrate, FIG. 3 is a schematic view of a processing apparatus applied to an embodiment of the present invention, and FIG. 4 is a sectional view of a semiconductor substrate and a processing apparatus for explaining a conventional method of processing a semiconductor substrate. 5 Figures (a), (b)
3A and 3B are a sectional view of a semiconductor substrate and a beam intensity characteristic diagram of a focused ion beam, respectively, for explaining a conventional method for processing a semiconductor substrate. 1, 1a ... GaAs substrate, 2 ... Upper layer film, 3 ... Opening part, 4, 4a ... Etching groove, 10, 10a, 10b
... Liquid metal ion source, 11, 11a, 11b ... Focused ion beam, 20, 20a ... Radical generation tube, 21
...... SiF ₄ gas, 22 …… Cl radicals, 31 …… vapor deposition equipment, 32,33 …… focused ion beam etching equipment, 40 …… etching chambers, 41a to 41c …… bottom,
42 ... Upper side wall, 50 ... Reactive gas.

Claims (1)

[Claims] 1. A step of forming an upper layer film of a predetermined material on a semiconductor substrate to be processed, and supplying one of a first gas and a radical for promoting a reaction on the upper layer film. Meanwhile, a step of irradiating a focused ion beam from the first ion source to perform etching to selectively form an opening in the upper layer film, and a step of exposing the semiconductor substrate exposed in the opening to the semiconductor substrate Etching is performed by irradiating a focused ion beam from a second ion source while supplying one of a second gas and a radical having high reactivity and sufficiently low reactivity with respect to the upper layer film. And a step of forming an etching groove having a predetermined depth.