JPH11340194A - Method for dry-etching and semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a work surface with less damage by, when etching is performed with the plasma of the mixed gas containing hydrocarbon gas as an etchant, mixing the mixed gas with the gas of molecule comprising independent or a plurality of phosphorus atoms. SOLUTION: On an n-type InP substrate 2, an n-type InP buffer layer 4, an undope multiple quantum well active layer 5, a p-type InP clad layer 6, and a p-type InGaAs contact layer 7 are sequentially formed by organic metal vapor-phase growth method. Then the wafer is carried in above a cathode electrode of an etching device of parallel-flat type electrode structure. Then, the mixed gas of ethane, hydrogen, argon, and phosphin (mixing ratio 4:10:1:1) is guided into an etching processing device, and at gas pressure 80 mT, such high-frequency electric power 300 W as with an electrode provided with a sample as a cathode is supplied for grow discharge. Thus, reactive ion etching is performed to form a step of about 3 micron on the substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention belongs to the technical field of a dry etching method suitable for manufacturing a semiconductor device, particularly a compound semiconductor device, a semiconductor optical device manufactured by the method, and an optical application system using the same.

[0002]

2. Description of the Related Art An etching technology for a compound semiconductor is as follows.
It is used for various compound semiconductor devices such as a semiconductor laser, an optical modulator, a heterojunction bipolar transistor, and a high electron mobility transistor. The wet etching has long been used for the etching of compound semiconductors. However, in recent years, there has been an increasing demand for improving the processing dimension uniformity within the wafer surface, and research on dry etching technology has been advanced. Conventional dry etching techniques for compound semiconductors are described systematically and in detail in Integrated Circuit Process Technology Series Semiconductor Dry Etching Techniques, edited by Wei Tokuyama and Sangyo Tosho Co., Ltd. As described in detail in this document, two systems of a hydrocarbon-based gas and a chlorine-based gas have been studied as a dry etching method for a compound semiconductor. Of these, hydrocarbon-based gases are easier to use than toxic and corrosive chlorine-based gases, and the vapor pressure of the reaction product is high and good etching can be performed under room temperature conditions. Used. As a known example of the dry etching of a hydrocarbon gas, for example, an optical waveguide is formed by reactive ion etching of a hydrocarbon gas.
Reliability test results of Fe-doped InP embedded semiconductor lasers are published in Journal of Lightwave Technology 15
Volume 3, Issue 3, pages 534-537, reported in 1997

[0003]

The above-mentioned conventional dry etching technology of hydrocarbon gas has the following problems.
The problems described below are examples of materials to be etched.
Although discussion will be made with an example taking InP as an example, it is specified in advance that the same discussion holds for GaAs and InGaAsP.

[0004] The mechanism by which InP is etched in the plasma of a hydrocarbon-based gas is mainly that methane radicals adsorbed on the surface react with In atoms by the energy of ion bombardment to react with In (CH ₃ ) ₂ and In (CH ₃ ). _{3) 3} and generating and desorbing hydrogen radicals and P atoms adsorbed on the surface due to desorption to react to PH _3. However, desorption rate of the reaction product methylation In direction of PH ₃ is a gas at room temperature
Since it is faster, the etched surface becomes In-rich, which causes various damages. In other words, not only the In-rich layer itself, but also
The In-rich layer oxidizes to form In oxide, and
Interstitial In defects and vacancy P defects penetrate into the deeper part of the rich layer due to the diffusion from the In rich layer or knock-on phenomena due to ion bombardment. And form a composite defect. In high-speed electronic devices and semiconductor lasers,
Since the etching is mainly performed on the electrically active layer and the optically active layer, respectively, the above-mentioned damage caused at the time of etching has a serious adverse effect on the reliability of the device characteristics and device life. Dry etching is applied to mesa processing of a semiconductor laser, and this mesa is embedded in an insulating semiconductor, so-called
Taking a BH (Buried-Heterostructure) laser as an example, the oxygen atoms remaining at the interface between the mesa and the buried layer are n-type impurities, which cause a leak current, and the In-rich layer may serve as a leak path. Needless to say. In addition, the complex defects formed inside the mesa are multiplied and complexed by the action of light and current during energization to form a non-radiative recombination center, which causes an increase in the threshold current and the non-luminous current. As a specific example, as disclosed in the above document, when an optical waveguide of a semiconductor laser is formed by reactive ion etching of a hydrocarbon-based gas, an element at the time of an energization test is affected by a damaged layer on the side of an active layer. It has been shown that the degradation progresses faster and is suppressed by removing the damaged layer by wet etching. As described above, conventionally, the damaged layer has been removed by adding wet etching after dry etching. However, when wet etching is added, the uniformity of pattern dimensions in the wafer surface is significantly impaired, and the advantage of dry etching is lost.

A first object of the present invention is to provide a method for dry-etching a hydrocarbon-based gas (and a method for manufacturing a semiconductor device using the same) by which a processed surface with low damage can be obtained. A second object of the present invention is to provide a semiconductor device manufactured by using the dry etching method of the present invention. A third object of the present invention is to provide a semiconductor laser manufactured by using the dry etching method of the present invention. A fourth object of the present invention is to provide an optical module equipped with the semiconductor laser of the present invention. A fifth object of the present invention is to provide an optical application system such as an optical transmission system or an optical information processing system equipped with the semiconductor laser of the present invention.

[0006]

SUMMARY OF THE INVENTION A first object of the present invention is to provide:
In a dry etching method for forming a step on a workpiece on which a mask pattern has been formed in advance by using a plasma of a mixed gas containing a hydrocarbon gas as an etchant, the mixed gas may be a gas of a molecule having at least one phosphorus atom as a constituent element. Is achieved by mixing. It is also achieved that the molecule having at least one phosphorus atom as a constituent is phosphine. Further, it is achieved by mixing a gas of a molecule containing at least one arsenic atom with the above mixed gas. It is also achieved that the molecule containing at least one arsenic atom is arsine. In addition, this is achieved when the mixed gas contains hydrogen gas. In addition, this is achieved when the hydrocarbon gas is methane gas. Further, this is achieved by that the hydrocarbon gas is ethane gas. In addition, this is achieved when the workpiece includes a III-V compound semiconductor. In addition, the workpiece is II
This is achieved by including a group IV mixed crystal semiconductor. Also,
This is achieved when the workpiece includes a semiconductor containing phosphorus as a component. Further, a second object of the present invention is achieved by providing a semiconductor device manufactured by using the dry etching method of the present invention. Further, a third object of the present invention is achieved by providing a semiconductor laser manufactured by using the dry etching method of the present invention. Further, a fourth object of the present invention is achieved by providing an optical module equipped with the semiconductor laser of the present invention. Further, a fifth object of the present invention is achieved by providing an optical application system such as an optical transmission system or an optical information processing system equipped with the semiconductor laser of the present invention.

Hereinafter, the operation of the present invention will be described.

In the present invention, desorption of group V atoms from the surface to be processed is suppressed by mixing a gas of a molecule containing a group V element of a group III-V compound semiconductor to be etched as a constituent element. Hereinafter, a case where InP is etched while phosphine is mixed with a reaction gas will be described as an example. When phosphine is added to the etching gas, the partial pressure of phosphine increases, and the amount of phosphine adsorbed from the gas to the etching surface increases, so that the rate of desorption of phosphine desorbed from the InP surface as an etching product is apparent. Become slow. For this reason, the imbalance in the speed of desorption of In and P is alleviated, so that the generation of an In-rich layer is suppressed and damage is reduced. Next, the flow rate of phosphine necessary for operating the present invention will be described. In order to sufficiently increase the partial pressure of phosphine, it is necessary to introduce more phosphine than the amount of phosphine generated as a reaction product during etching. Therefore, the minimum required phosphine flow rate varies depending on the conditions such as the etching rate, and the required flow rate cannot be definitely determined. Therefore, just an example. Consider a case where an InP substrate having a diameter of 2 inches is etched at an etching rate of 0.05 μm / min. By reactive ion etching of a mixed gas of methane and hydrogen. If the amount of phosphine generated as an etching product in this case is converted into the flow rate introduced into the chamber, it corresponds to about 0.07 sccm. Therefore, in this case, if at least 0.07 sccm or more of phosphine is added, the effects of the present invention can be obtained.

In the above description, a case has been described where the material to be etched contains phosphorus (P) as a constituent element and phosphine is mixed with a reaction gas for etching. However, the material to be etched contains arsenic (As) as a constituent element. When it is contained, it is needless to say that the same effect is obtained by mixing arsine. When the material to be etched contains both phosphorus and arsenic as constituents, it goes without saying that a great effect can be obtained by mixing phosphine and arsine simultaneously.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of the present invention described above will be described with reference to the following Examples 1 to 6 and their related drawings (FIGS. 1 to 6).

<First Embodiment> First, a first embodiment of the present invention will be described in detail with reference to FIG. Example 1 In this example, results of evaluation of damage to an n-type InP substrate etched using the etching method of the present invention by photoluminescence measurement are shown. For comparison, data of a conventional sample etched under the condition without addition of phosphine and a reference sample not subjected to dry etching are also shown.

First, the etching conditions will be described. The apparatus used in this embodiment is a reactive ion etching apparatus having parallel plate electrodes. Etching under the conditions of the present invention uses methane 8 sccm, hydrogen 32 sccm, phosphine 10 sccm as a reaction gas, a gas pressure of 40 mT, and an applied high-frequency power of 20.
This was performed in the state of 0 W, and the 2-inch n-type InP substrate was etched by 1 μm. Etching under conventional conditions was performed using 10 sccm of methane and 40 sccm of hydrogen as a reaction gas at a gas pressure of 40 mT and an applied high-frequency power of 200 W to etch a 2-inch n-type InP substrate at 1 μm. Photoluminescence measurement was repeated on these three samples while etching the surface with sulfuric acid. FIG. 1 shows the measurement results of the distribution of the photoluminescence intensity in the depth direction. The photoluminescence intensity of the reference sample not subjected to dry etching is almost constant except for a few nm on the surface, whereas the sample subjected to dry etching of the prior art without adding phosphine is 40 nm from the surface.
In the region, the photoluminescence intensity is significantly reduced. This is because damage is severe in a region 40 nm from the surface, and non-radiative recombination occurs. On the other hand, in the sample subjected to the dry etching to which the phosphine of the present invention was added, the effect of the present invention in which the desorption rate of In on the surface and the desorption rate of P are balanced and an In-rich layer is not generated is reflected. In addition, the occurrence of damage to the etched surface was suppressed, and the region where the photoluminescence intensity was reduced was 10 nm or less from the surface, and a processed surface which was extremely low as compared with the dry etching damage of the prior art was obtained.

In this embodiment, the case where a reactive ion etching apparatus is used has been described. However, the same effect can be obtained by using another etching apparatus such as a microwave etching apparatus or a chemical dry etching apparatus. Has been confirmed. In this embodiment, the example in which phosphine is added to the etching of the InP substrate is described.However, the same effect can be obtained when arsine is added to the etching of GaAs or when arsine and phosphine are added simultaneously to the etching of InGaAsP. Observed. Further, in the present embodiment, an example was shown in which methane and hydrogen gas were used as the reaction gas other than phosphine, but similar effects were obtained when a mixed gas of ethane gas and hydrogen was used. Needless to say, the effect of the present invention does not change even if a gas such as oxygen or argon is added to these reaction gases. Also, it has been confirmed that the same effect can be obtained even if hydrogen is not contained in the mixed gas.

<Embodiment 2> Next, a second embodiment will be described in detail with reference to FIG.

An n-type InP buffer layer (thickness 0.3 μm) 4, an undoped multiple quantum well active layer 5 and a p-type InP cladding layer (thickness 2.0 μm) are formed on an n-type InP substrate 2 by metal organic chemical vapor deposition. 6, a p-type InGaAs contact layer (0.2 micron thick) 7 was formed in order. The multiple quantum well active layer 5 is an InGaAs well layer
5 layers (thickness: 60 nm) and InGaAsP barrier layer (thickness: 100 nm, composition wavelength
1.15 microns) sandwiched between 6 layers. Next, an SiO ₂ film having a thickness of 300 nm was formed by a thermal CVD method, and an SiO ₂ stripe 1 having a width of 1.5 μm was formed using a normal lithography technique (FIG. 2A). Next, this wafer is loaded onto the cathode electrode of an etching apparatus having a parallel plate electrode structure, and a mixed gas of ethane, hydrogen, argon, and phosphine is mixed at 50 sccm (mixing ratio: 4: 1).
0: 1: 1) was introduced into the etching apparatus, and at a gas pressure of 80 mT, a high-frequency power of 30 using the electrode on which the sample was placed as a cathode.
By supplying 0 W and performing glow discharge, reactive ion etching was performed to form a 3 micron step on the substrate. At this time, since the reaction gas contains phosphine,
Almost no damage occurs on the etched surface (Fig. 2
(b)). Thereafter, the polymer deposited on the SiO ₂ pattern 1 during the etching was removed by oxygen plasma ashing, and then carried into a metal organic chemical vapor deposition furnace. Next, growth temperature 60
Fe-doped semi-insulating by introducing phosphine gas, trimethylindium, ferrocene, and methyl chloride at 0 ° C
InP current confinement layer (growth thickness 3 microns) 8 was grown (Fig. 2
(c)). Since a compound semiconductor such as InP does not grow on the SiO ₂ stripe, the semiconductor exposed surface is selectively buried by the InP layer. However, amorphous or polycrystalline semiconductor may be deposited on the SiO ₂ stripe,
By adding a small amount of methyl chloride as in this embodiment, such precipitation can be suppressed, and the embedded surface can be made flat. After buried growth, SiO ₂
Stripe 1 is removed with diluted hydrofluoric acid to form p-side electrode 9,
After the back surface of the substrate was thinned by polishing, an n-side electrode 10 was formed on the back surface (FIG. 2 (d)). Finally, by dividing and opening the wall,
A semiconductor laser with an emission wavelength of 1.55 microns was fabricated.

The fabricated laser device has a threshold current of 10 mA and an oscillation efficiency of 0.45 W / A at room temperature and under continuous conditions, reflecting the effect of the present invention in which the reactive current component such as non-radiative recombination due to damage is small. Thus, characteristics with low threshold and high efficiency were obtained. In addition, as a result of conducting a constant optical output current test at 50 ° C. and 5 mW, an estimated lifetime of 200,000 hours was obtained, reflecting the crystal structure with few defects of the present invention. In this embodiment, the case where the present invention is applied to a semiconductor laser in the 1.55 μm band is described, but the present invention is also applicable to a semiconductor laser in the 1.3 μm band and other wavelength bands. Further, in this embodiment, the case where the reactive ion etching having the parallel plate type electrode is used has been described. However, the same effect can be obtained by using an ECR type or ICP type microwave etching apparatus. Further, in the present embodiment, the case where SiO ₂ is used as the mask material has been described, but other materials such as Si ₃ N ₄ may be used. In the present embodiment, the case where the present invention is applied to a semiconductor laser has been described. However, the present invention is applicable to other compound semiconductor devices such as an optical modulator, a high electron mobility transistor, a field effect transistor, a photodiode, and an optical waveguide device. Could also be applied. Further, in this embodiment, an example using a mixed gas of ethane / hydrogen / argon / phosphine has been described, but methane may be used as the hydrocarbon gas. Further, another gas such as carbon dioxide or oxygen may be added to the mixed gas. In this example, the case where only phosphine was added to the reaction gas was described.However, since the active layer is composed of InGaAsP, it was confirmed that a further greater damage reduction effect was confirmed by adding phosphine and arsine simultaneously. Append.

<Embodiment 3> Next, a third embodiment will be described in detail with reference to FIG. FIG. 3 shows a wavelength of 1.3 μm using the present invention.
This is an example of fabricating a band distributed feedback semiconductor laser. FIG.
As shown in (a), an n-type (100) InP buffer layer 1.0 μm15, n-type InGaAs
P lower guide layer (composition wavelength 1.10 μm) 0.05 μm, 5-period multiple quantum well layer (6.0% thick 1% compression strained InGaAsP (composition wavelength 1.37 μm) well layer, 10 nm thick InGaAsP (composition wavelength 1.10 μm)
μm) barrier layer), InGaAsP (composition wavelength 1.10 μm), active layer 16 composed of upper light guide layer 0.05 μm, first p-type InP cladding layer 0.1 μm17, undoped InGaAsP (composition wavelength 1.15 μm)
m) A diffraction grating supply layer of 0.05 μm 18 is sequentially formed. The emission wavelength of the multiple quantum well active layer 16 is about 1.31 μm. next,
A diffraction grating resist pattern 4 whose phase was inverted at the center of the device with a period of 241 nm was formed by electron beam lithography, and the ECR
After loading into plasma etching equipment, methane gas 10scc
m, hydrogen gas 30sccm, phosphine gas 2sccm, gas pressure 2m
Etch under the conditions of T, microwave power of 1000 W and RF bias of 50 V. As a result, as shown in FIG.
A diffraction grating 20 whose phase is inverted at the center of the device at 1 nm is formed on the entire surface of the substrate. The depth of the diffraction grating is about 100 nm, and the diffraction grating penetrates the diffraction supply layer 18 and the first p-type InP cladding layer 17.
To reach. Subsequently, a second p-type InP cladding layer 1.7 μm 21 and a high-concentration p-type InGaAs
A cap layer 0.2 μm 22 is sequentially formed (FIG. 3C). Next, a buried laser structure with a width of about 1.5 μm or a width of about 2.2 μm
After working to form a ridge waveguide type laser structure of μm, an upper electrode 23 and a lower electrode 24 are formed. As shown in FIG. 3 (d), after being cut into devices having a device length of 400 μm by a cleavage process,
A low-reflection film 25 having a reflectance of about 1% is formed on both end surfaces of the element by a known method.

The fabricated distributed feedback semiconductor laser device in the 1.3 μm band does not cause damage during the formation of the diffraction grating, and reflects a small reactive current component due to non-radiative recombination generated when there is damage. Under a continuous condition at room temperature, the threshold current was 10 mA, the oscillation efficiency was 0.45 W / A, and a low threshold and high efficiency characteristics were obtained. In addition, as a result of conducting a constant light output current test at 50 ° C. and 5 mW, an estimated lifetime of 200,000 hours was obtained, reflecting a high-grade crystal structure without a damaged layer. When a forward bias is applied below the oscillation threshold,
The spectrum shape is shown in FIG. A typical spectrum in which the oscillation dominant mode appears at the center of the stop band reflecting the phase shift type diffraction grating was obtained. In addition, reflecting the excellent process dimension controllability of the present invention, the reproducibility and single mode selectivity of the phase shift type diffraction grating are extremely high, and the stable single mode with a submode suppression ratio of 40 dB or more even at a high temperature of 85 ° C. One-mode operation has been achieved with a high production yield of 95% or more.
This structure can be applied not only to the 1.3 μm band but also to a distributed feedback semiconductor laser in the 1.55 μm band and other wavelength bands.

<Embodiment 4> Next, a fourth embodiment will be described in detail with reference to FIG. FIG. 4 shows the optical lens after mounting the distributed feedback semiconductor laser 26 of the third embodiment on the heat sink 27.
28 is a structural diagram of an optical transmission module in which a photodiode 29 for monitoring the light output of the rear end face and an optical fiber 30 are integrated. At room temperature and under continuous conditions, the threshold current was 10 mA and the oscillation efficiency was 0.20 W / A. In addition, an estimated lifetime of 200,000 hours was obtained reflecting the crystal structure of the present invention with less irradiation damage. In addition, even at a high temperature of 85 ° C, a threshold current of 25 mA and an oscillation efficiency of 0.13 W / A were obtained, showing good oscillation characteristics. In addition, reflecting the excellent processing dimension controllability of the present invention, a stable single mode operation with a sub mode suppression ratio of 40 dB or more was realized at a high production yield of 95% or more even at a high temperature of 85 ° C. With this laser, the standardized optical coupling coefficient can be set as high as 2.5 or more.
The degradation of oscillation characteristics due to the return light from the fiber end, which is the biggest problem in module mounting, did not occur at all.

<Embodiment 5> Next, a fifth embodiment will be described in detail with reference to FIG. FIG. 5 illustrates a transmission module according to the fourth embodiment.
This is a trunk optical communication system using No. 31. The transmission device 32 has a transmission module 31 and a drive system 33 for driving the module 31. The optical signal from the module 31 passes through the fiber 34 and is detected by the light receiving unit 36 in the receiving device 35.
According to the optical communication system of this embodiment, repeaterless optical transmission over 100 km can be easily realized. This is based on the fact that the chirping is significantly reduced, so that the signal degradation due to the dispersion of the fiber 34 is also significantly reduced.

<Embodiment 6> Next, a sixth embodiment will be described in detail with reference to FIG. FIG. 6 shows a GaAs HBT (He
This is an example of producing a terojunction bipolar transistor. This HBT device has an emitter cap layer 66, an emitter layer 6
5, a base layer 64, a collector layer 63, a sub-collector layer 62, and a substrate 61. This is used in a self-aligned manner by using the tungsten silicide electrode 67 as an emitter electrode as a mask,
According to the etching method of the present invention, n-In _0.5 Ga _0.5 As / n-GaA
s Emitter cap layer 66 to n-Al _0.3 Ga _0.7 As emitter layer 6
Etch up to 5 (Fig. 6 (a)). An ICP (Inductively-coupled plasma) etching apparatus is used for the etching. Etching conditions are methane gas 10sccm, hydrogen gas 40sccm, arsine gas 2sccm, gas pressure 4mT, incident power
1000W, RF bias 30V. Then, after forming an SiO ₂ film 68 on the side wall of the emitter electrode, using these as a mask, the p-type A
The portions from the lGaAs base layer 64 to the GaAs collector layer 63 are etched by the same method as above (FIG. 6B). After this,
The side wall SiO ₂ film 68 is removed with dilute hydrofluoric acid, the buried SiO ₂ 69 and the insulating side wall SiO ₂ 70 are formed (FIG. 6C), the base electrode 71 and the collector electrode 72 are formed, and the target HBT element is formed. (Fig. 6 (d)).

The fabricated device achieved good reliability with an estimated lifetime of 150,000 hours, reflecting the effect of the present invention in which the formation of recombination centers in the base layer due to etching damage was greatly suppressed. In this embodiment, the GaAs HBT element has been described.
nP HBT element, HEMT (High Electron Mobility Transisto)
r) devices and their MMICs (Monolithic Microwave Integr
ated Circuit) and other compound semiconductor electronic devices, the same effect was obtained.

[0023]

According to the present invention, dry etching of a compound semiconductor with low damage can be realized. The use of the present invention is effective in reducing the cost by increasing the reliability of the compound semiconductor device and improving the production yield.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a first embodiment of the present invention.

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

FIG. 3 is a diagram illustrating a third embodiment of the present invention.

FIG. 4 is a diagram for explaining a fourth embodiment of the present invention.

FIG. 5 is a diagram for explaining a fifth embodiment of the present invention.

FIG. 6 is a diagram for explaining a sixth embodiment of the present invention.

[Explanation of symbols]

1 ... SiO ₂ mask, 2 ... InP substrate, 4 ... n-type InP buffer layer, 5
... undoped multiple quantum well active layer, 6 ... p-type InP cladding layer, 7 ... p-type InGaAs contact layer, 8 ... Fe-doped semi-insulating property
InP current confinement layer, 9 ... p-side electrode, 10 ... n-side electrode, 15 ... n-type In
P buffer layer, 16: multiple quantum well active layer, 17: first p-type I
nP cladding layer, 18 ... undoped InGaAsP diffraction grating supply layer, 20 ... diffraction grating, 21 ... second p-type InP cladding layer, 22 ...
p-type InGaAs cap layer, 23 ... upper electrode, 24 ... lower electrode,
25: Low reflection film, 26: Distributed feedback semiconductor laser, 27: Heat sink, 28: Optical lens, 29: Photodiode, 30
... optical fiber, 31 ... transmission module, 32 ... transmission device, 33
... Drive system, 34 ... Optical fiber, 35 ... Receiving device, 36 ... Light receiving section, 61 ... GaAs substrate, 62 ... Sub-collector layer, 63 ... GaAs collector layer, 64 ... p-type AlGaAs base layer, 65 ... n-Al _0.3 Ga _0.7 As
Emitter layer, 66 ... n-In _0.5 Ga _0.5 As / n-GaAs emitter cap layer, 67 ... tungsten silicide electrode, 68 ... sidewall Si
O ₂ film, 69: embedded SiO ₂ , 70: insulating side wall SiO ₂ , 71: base electrode, 72: collector electrode.

Claims (14)

[Claims] 1. A dry etching method for forming a step on a workpiece on which a mask pattern has been formed in advance by using a plasma of a mixed gas containing a hydrocarbon gas as an etchant, wherein the mixed gas contains at least one phosphorus atom. Dry etching method, wherein a gas of the following molecule is mixed. 2. The dry etching method according to claim 1, wherein the molecule having at least one phosphorus atom as a constituent is phosphine. 3. A dry etching method for forming a step on a workpiece on which a mask pattern has been formed in advance using plasma of a mixed gas containing a hydrocarbon gas as an etchant, wherein said mixed gas contains at least one arsenic atom. Dry etching method, wherein a gas of the following molecule is mixed. 4. The dry etching method according to claim 3, wherein the molecule comprising at least one arsenic atom is arsine. 5. The dry etching method according to claim 1, wherein said mixed gas contains hydrogen gas. 6. The dry etching method according to claim 1, wherein said hydrocarbon gas is methane gas. 7. The dry etching method according to claim 1, wherein said hydrocarbon gas is ethane gas. 8. The dry etching method according to claim 1, wherein said workpiece includes a group III-V compound semiconductor. 9. A dry etching method according to claim 1, wherein said workpiece includes a group III-V mixed crystal semiconductor. 10. The dry etching method according to claim 1, wherein the workpiece includes a semiconductor containing phosphorus or arsenic as a component. 11. A semiconductor device manufactured by using the dry etching method according to claim 1. 12. A semiconductor laser manufactured by using the dry etching method according to claim 1. 13. An optical module comprising the semiconductor laser according to claim 12. 14. An optical application system comprising the semiconductor laser according to claim 12.