JPH0783017B2 - Compound semiconductor microfabrication method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of finely processing a compound semiconductor using an electron beam, and more particularly to a method of finely processing a compound semiconductor such as GaAs with a precision of nanometer scale.

[0002]

2. Description of the Related Art Microfabrication technology for compound semiconductors is important for semiconductor processes. In particular, microfabrication using electron beams has attracted attention as a recent topic. For such dry etching using an electron beam, a method of patterning the InGaAs growth layer on a GaAs compound semiconductor with an electron beam as a mask and then transferring it to the underlying compound semiconductor material is the 53rd Annual Meeting of the Japan Society of Applied Physics. It is proposed in the technical paper "EB excited etching of GaAs using InGaAs thin film mask" by Kawamoto et al.

FIG. 3 is a process diagram of this conventional example. Figure 3
As shown in (a), a GaAs semiconductor layer 2 is grown on a GaAs substrate 1, and an InGaAs layer 33 is further grown thereon. Next, as shown in FIG. 6B, the InGaAs layer 33 is etched by simultaneously irradiating the electron beam 4 and the chlorine gas 5. After that, the electron beam is turned off and the underlying GaAs is etched only with the chlorine gas 5, as shown in FIG. At this time, the mask of the InGaAs layer 33 is chlorine gas 5
Resistant to. Therefore, from the above process, GaA
s patterning has been realized.

In such fine processing using an electron beam, electrons are irradiated 10,000 times as light as compared with ions, so that there is no damage due to ion irradiation unlike the conventional dry etching using ions. It can be processed.

[0005]

In the prior art using the InGaAs layer as a mask, the InGaAs layer is GaA.
Since it is a strain system that does not lattice match with the s substrate, it is necessary to precisely control the mixed crystal composition and the grown film thickness. If the degree of strain is too large, the InGaAs layer may crack and fail to function as a mask.

Further, it is known that the composition in the growth film of the InGaAs layer is not uniform, and the In composition increases near the surface, and so-called In segregation occurs. Therefore, it may be difficult to maintain the reproducibility and controllability of the mask because an InGaAs layer that does not have reproducibility as a mask effect may grow, and thus the reproducibility and controllability of fine processing of compound semiconductors should be maintained. Was not easy. An object of the present invention is to provide a method for forming a semiconductor mask which is free from segregation of In and is excellent in reproducibility and controllability, and finely processing a compound semiconductor using this mask.

[0007]

In order to achieve the above object, in the fine processing method according to the present invention, GaAs or Ga is used.
A step of stacking a superlattice structure of InAs and GaAs on a compound semiconductor surface of an As / AlGaAs heterostructure or a quantum well structure, and irradiating the superlattice structure with an electron beam in a reactive gas containing a halogen atom Fixing to form a pattern by partially etching the lattice structure, and the GaAs or GaAs / AlG using the superlattice structure formed by this pattern forming process as a mask.
and a step of etching a compound semiconductor having a hetero structure or quantum well structure of aAs.

The etching of a compound semiconductor of GaAs or a heterostructure of GaAs / AlGaAs or a quantum well structure may be carried out by gas etching using a reactive gas containing a halogen atom, or GaAs or Ga.
The compound semiconductor having a heterostructure or quantum well structure of As / AlGaAs may be etched by electron beam assisted etching performed by irradiating an electron beam in a reactive gas containing a halogen atom.

[0009]

In the present invention, by using the superlattice structure of InAs and GaAs as a mask, the surface segregation, which is a problem with the InGaAs mask, can be avoided and an electron beam patterning process excellent in controllability and reproducibility can be realized.

[0010]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a process diagram showing a first embodiment of the present invention. As shown in FIG. 1A, a GaAs layer 2 is crystal-grown on a GaAs substrate 1, and InAs /
The mask layer 3 is formed by growing a GaAs monoatomic layer superlattice for 5 periods.
And A molecular beam crystal growth method (MBE) was used for crystal growth.

Next, as shown in FIG. 3B, the substrate temperature is heated to 160 ° C., and the surface is partially irradiated with an electron beam 4 with an accelerating voltage of 3 kV in chlorine gas 5 of 5 × 10 ^-5 Torr. Then, electron beam assisted etching was performed for 5 minutes. As a result, only the portion of the superlattice structure mask layer 3 irradiated with the electron beam 4 was etched and a pattern could be formed.
On the other hand, the superlattice structure mask layer 3 which was not irradiated with the electron beam 4 was not etched by the chlorine gas 5.

Next, the substrate temperature is set to 1 as shown in FIG.
The temperature was lowered to 00 ° C., and gas etching was performed with chlorine gas 5 of 5 × 10 ⁻⁵ Torr. As a result, the openings 6 of the superlattice structure mask layer formed by electron beam assisted etching
The GaAs growth layer 2 was gas-etched only through.

FIG. 2 is a process diagram showing a second embodiment of the present invention.

As shown in FIG. 2A, a GaAs layer 2 is crystal-grown on a GaAs substrate 1 and InAs is further formed on the surface thereof.
As a mask layer 3, a monoatomic layer superlattice of / GaAs was grown for 5 cycles. A molecular beam crystal growth method (MBE) was used for crystal growth.

Next, as shown in FIG. 2B, the substrate temperature is heated to 160 ° C., and the surface is partially irradiated with an electron beam 4 with an accelerating voltage of 3 kV in a chlorine gas 5 of 5 × 10 ^-5 Torr. Then, electron beam assisted etching was performed for 5 minutes. As a result, only the portion of the superlattice structure mask layer 3 irradiated with the electron beam 4 was etched and a pattern could be formed.
On the other hand, the superlattice structure mask layer 3 which was not irradiated with the electron beam 4 was not etched by the chlorine gas 5.

Next, as shown in FIG. 3C, the substrate temperature is set to 5
The temperature was lowered to 0 ° C., and the front surface of the substrate was irradiated with a shower-shaped electron beam 27 with an acceleration voltage of 500 V in chlorine gas 5 of 5 × 10 ⁻⁵ Torr, and electron beam assisted etching was performed for 30 minutes. As a result, G is formed only through the openings 6 of the superlattice structure mask layer 3 formed by electron beam assisted etching.
Gas etching of the aAs growth layer 2 was completed. On the other hand, it was confirmed that etching did not proceed in the portion where the superlattice structure mask layer 3 remained, and the mask effect was sufficient. Although the example of processing the GaAs layer is shown in the above embodiments, it goes without saying that the method of the present invention can process a GaAs / AlGaAs heterostructure or a quantum well structure.

[0017]

As described above in detail with reference to the embodiments, according to the fine processing method of the present invention, InAs and Ga are formed.
By using the superlattice structure with As as a mask, the problems of controllability and reproducibility of the mask, which had been a problem in the past, are avoided, and a heterostructure or a quantum well structure of GaAs or GaAs / AlGaAs with a nanometer scale accuracy is obtained. Fine processing was possible with excellent controllability and reproducibility.

[Brief description of drawings]

FIG. 1 is a process drawing showing a fine processing method according to a first embodiment of the present invention.

FIG. 2 is a process drawing showing the fine processing method according to the second embodiment of the present invention.

FIG. 3 is a process diagram showing a conventional fine processing method.

[Explanation of symbols]

 1 GaAs Substrate 2 GaAs Growth Layer 3 Superlattice Structure Mask Layer 33 InAs Mask Layer 4 Electron Beam 5 Chlorine Gas 6 Opening 27 Shower Electron Beam

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display location H01L 29/778 29/80 29/812 9171-4M H01L 29/80 A 9171-4MH

Claims (3)

[Claims] 1. A step of laminating a superlattice structure of InAs and GaAs on a compound semiconductor surface of GaAs or a heterostructure of GaAs / AlGaAs or a quantum well structure,
A step of forming a pattern by partially etching the superlattice structure by irradiating the superlattice structure with an electron beam in a reactive gas containing a halogen atom; and a patterned superstructure formed by the pattern forming step. And a step of etching the compound semiconductor having the GaAs or GaAs / AlGaAs heterostructure or quantum well structure using the lattice structure as a mask. 2. The microfabrication method according to claim 1, wherein the etching of the compound semiconductor having a hetero structure or a quantum well structure of GaAs or GaAs / AlGaAs is gas etching using a reactive gas containing a halogen atom. 3. The etching of a compound semiconductor of GaAs or a heterostructure of GaAs / AlGaAs or a quantum well structure is electron beam assisted etching performed by irradiating an electron beam in a reactive gas containing a halogen atom. Fine processing method.