Coherent light generators – Particular active media – Semiconductor
Reexamination Certificate
2000-07-27
2001-07-24
Arroyo, Teresa M. (Department: 2881)
Coherent light generators
Particular active media
Semiconductor
C372S045013
Reexamination Certificate
active
06266354
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a compound semiconductor and a method for producing the same. More particularly, the present invention relates to a dry-etching method for a III-V group or II-VI group compound semiconductor, and to a semiconductor laser device fabricated thereby.
2. Description of the Related Art
As a conventional dry-etching technique for a compound semiconductor, a method described in Japanese Laid-Open Patent Publication No. 7-66175 is known in the art. In this method, dry-etching is performed on an In-containing compound semiconductor by using ECR-RIBE (Electron Cyclotron Resonance-Reactive Ion Beam Etching) apparatus with auxiliary coil reducing a divergence of magnetic field. In the ECR-RIBE apparatus, a primary coil and an auxiliary coil are provided so that the divergence of magnetic field in the vicinity of the sample to be etched is inhibited. In this method, chlorine, helium and nitrogen are used as the etching gas. With the flow ratio of the chlorine
itrogen gases being equal to one or less and the internal pressure being equal to 0.5 mTorr, a cross-section which is vertical with respect to the etching mask and a smooth etching surface are obtained.
According to the above-mentioned publication, when the gas is supplied with the chlorine gas
itrogen gas ratio being equal to one or less, the production of chlorine radicals is inhibited and the etching due to chlorine ions becomes more predominant over the etching due to chlorine radicals. This makes it. possible that ions having energy as low as several tens of eV can be used and a balance of evaporation of a chloride of In and a chloride of P can still be achieved. As a result, etching which is capable of obtaining a cross-section which is vertical with respect to the etching mask, and of obtaining a smooth etching surface can be realized.
Conventionally, the dry-etching of compound semiconductor had problems associated with roughness of the etching surface due to a large difference in vapor pressures between the reactant of a III group element and the etching gas and the reactant of a V group element and the etching gas or with difficulty in controlling cross-sectional shapes.
Dry-etching technology disclosed in the above-mentioned publication also intended to solve these problems. In this technology, nitrogen gas is added so that chlorine gas is decomposed and the amount of chlorine radicals created with chlorine ions is kept below ⅓ of the total amount of chlorine radicals and chlorine ions, thereby solving the above-mentioned problems. Also realized in the above-mentioned technology is that a pressure inside the reaction chamber is made equal to 0.5 mTorr or less in order to minimize the production of chlorine radicals. This results in desorption velocities in equilibrium of the chloride of In and the chloride of P. A feature of the above-mentioned technology is that the etching is carried out under conditions which minimize the concentration of chlorine radicals. The above-mentioned publication does not show quantitative data concerning the amount of chlorine ions produced and the etching characteristics.
Moreover, if a sample to be etched contains Al, then Al
2
O
3
is formed with moisture remaining in the reaction chamber, thereby preventing the etching or greatly reducing the etching rate.
SUMMARY OF THE INVENTION
According to one aspect of the present invention, in an etching method for performing dry-etching on a III-V group compound semiconductor or a II-VI group compound semiconductor in a dry-etching apparatus including a plasma source for creating a plasma of density of about 10
10
cm
−3
or greater, using a mixed gas containing a gas including a halogen element and a gas including nitrogen, (a flow rate of the gas containing the halogen gas)/(a flow rate of the nitrogen gas)≧about 1, and an internal pressure during etching reaction is about 1 mTorr or greater.
In one embodiment of the present invention, ions created in the plasma source are accelerated, and a sample is etched by kinetic energy of the accelerated ions while a sample surface is being heated.
In one embodiment of the present invention, ions created in the plasma source are accelerated. Only a portion of the sample containing a II-VI group compound in the vicinity of the surface is heated by kinetic energy of the accelerated ions, and a support for the sample is cooled.
In one embodiment of the present invention, etching is performed while a sample holder is heated.
In one embodiment of the present invention, an etching method further includes the steps of: performing a first dry-etching wherein ions created in the plasma source are accelerated by a first accelerating voltage; and performing a second dry-etching, after the first dry-etching, wherein ions created in the plasma source are accelerated by a second accelerating voltage. The second accelerating voltage is larger than the first accelerating voltage.
In one embodiment of the present invention, an etching method further include a step of performing wet-etching.
In one embodiment of the present invention, the dry-etching apparatus includes a radical beam source and an ion beam source, and a density of radicals created in the radical beam source and a density of ions created in the ion beam source are independently controlled.
In one embodiment of the present invention, the compound semiconductor is formed of Al
x
Ga
y
In
1−x−y
P (0<x≦1, 0≦y≦1).
In one embodiment of the present invention, the compound semiconductor is formed above an off-substrate.
According to another aspect of the present invention, an etching method for performing dry-etching on a III-V group compound semiconductor or a II-VI group compound semiconductor in a dry-etching apparatus including a plasma source for creating a plasma of density of about 10
10
cm
−3
or greater, using a mixed gas containing a gas including halogen element and a gas including nitrogen, includes the steps of: performing a first dry-etching with a halogen ion density being made larger than a halogen radical density; and performing a second dry-etching with a halogen ion density being made smaller than a halogen radical density.
According to yet another aspect of the present invention, an etching apparatus includes a radical beam source, an ion beam source, a reaction chamber having the radical beam source and the ion beam source connected thereto, a sample support provided inside the reaction chamber and a load lock chamber.
According to still another aspect of the present invention, a method for producing a semiconductor laser device includes the steps of: epitaxially growing at least one compound semiconductor layer on a semiconductor substrate; forming a patterned mask on the at least one compound semiconductor layer; performing etching on the at least one compound semiconductor layer, using the patterned mask, by any one of the etching methods described above so as to form a ridge stripe; and burying the ridge stripe with compound semiconductor.
In one embodiment of then present invention, the substrate is a misoriented substrate; the at least one compound semiconductor layer includes an active layer, an n-AlGaInP cladding layer and p-AlGaInP cladding layer, the n-AlGaInP cladding layer and the p-AlGaInP cladding layer interposing the active layer; and the ridge stripe contains the p-AlGaInP layer.
In one embodiment of the present invention, the p-AlGaInP cladding layer has a p-AlGaInP first cladding layer and a p-AlGaInP second cladding layer, and an etching stopper layer is formed between the first cladding layer and the second cladding layer.
In one embodiment of the present invention, a layer for monitoring an etched amount of the p-AlGaInP second cladding layer is formed within the p-AlGaInP second cladding layer.
According to still another aspect of the present invention, a semiconductor laser device includes: a substrate; and a ridge stripe formed on the substrate and including an active layer, an n-cladding
Adachi Hideto
Chino Toyoji
Kidoguchi Isao
Kumabuchi Yasuhito
Arroyo Teresa M.
Matsushita Electric - Industrial Co., Ltd.
Monbleau Davienne
Renner , Otto, Boisselle & Sklar, LLP
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