JP2964553B2 - Method for manufacturing semiconductor light emitting device - Google Patents

Description

The present invention relates to a method for manufacturing a group II-VI compound semiconductor light emitting device.

[Prior Art] In a II-VI compound semiconductor light emitting device comprising zinc selenide (ZnSe), zinc sulfide (ZnS) and the like and a mixed crystal thereof, the reflection surface of a conventional optical resonator is {110} crystal. It is formed utilizing the cleavage of the surface.

[Problems to be Solved by the Invention] However, there are the following problems in processing the resonator reflection surface of the II-VI compound semiconductor light emitting device according to the above-described conventional technology.

The cleavage plane described above is an excellent reflection plane having smoothness and parallelism in the atomic order. However, a light-emitting device manufactured by cleavage shows its characteristics only by cleavage and chipping, and it is impossible to evaluate the characteristics on a wafer-by-wafer basis. It is necessary, and loss is large when characteristics are poor. In addition, the cleavage process is difficult to miniaturize, and the element size also depends on the resonator length, which has been a major obstacle when considering integration such as OEIC.

Furthermore, II-VI group compound semiconductors have higher ionic bonding properties than III-V group compound semiconductors, and therefore have lower mechanical strength. Therefore, in a step having a high mechanical factor such as a cleaving step, cracks are easily generated on the cleaved surface and the like, and the yield is greatly reduced. As described above, cleavage of the II-VI group compound semiconductor is more difficult than that of the III-V group compound semiconductor, and the production of the optical resonance surface requires a manufacturing method having few mechanical elements instead of the cleavage.

Therefore, the present invention solves the above-mentioned problems, and the object is to achieve fine processing, reproducibility, and practicability.
It is an object of the present invention to provide a method for manufacturing a semiconductor light emitting device having an optical resonator structure using a group VI compound semiconductor.

[Means for Solving the Problems] A method for manufacturing a semiconductor light emitting device of the present invention is a method for manufacturing a semiconductor light emitting device having an optical resonator structure using a II-VI compound semiconductor, in which an etching mask is formed. Process and reactive gas separation / separation type microwave excitation / ECR
Activating in a plasma chamber, extracting an ion beam at an extraction voltage of 0 V or more and 1 kV or less, performing dry etching by irradiating the material to be processed made of II-VI compound semiconductor with a uniform direction and Thus, the optical resonator reflection surface is formed.

The material of the etching mask is preferably an insulator or a metal, for example, a photoresist, silicon oxide, silicon nitride, molybdenum, or nickel oxide is used.

As the reactive gas, a gas containing at least a halogen element is preferably used.

The pressure of the reactive gas is preferably 5 × 10
The range is from ^-3 Pa to 1 Pa.

The incident power of the microwave is preferably 1 W
The range is at least 1 kW or less.

As the substrate temperature at the time of etching the material to be processed,
Preferably, the temperature is 0 ° C or more and 80 ° C or less.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings.

First, FIG. 3 shows a schematic sectional view of the configuration of a reactive ion beam etching apparatus according to an embodiment of the present invention. Since a gas containing a highly reactive halogen element is used as an etching gas, the sample preparation chamber 11 and the etching chamber 12 have a structure separated by a gate valve 24.
12 is always kept in a high vacuum. Reference numeral 13 denotes an electron cyclotron resonance (ECR) plasma chamber, which is surrounded by a cylindrical donut-shaped coil 14 for generating a magnetic field, and includes a microwave waveguide 15
There is a microwave-introduced quartz window at the connection point with. Electrons ionized and generated by microwaves repeatedly collide with gas while performing cyclotron motion with an axially symmetric magnetic field. This rotation period coincides with the microwave frequency, for example, 2.45 GHz when the magnetic field intensity is, for example, 875 Gauss, and the electronic system resonatesly absorbs the microwave energy. Therefore, the discharge continues even at a low gas pressure, a high plasma density is obtained, and the reactive gas can be used for a long life. Further, since the electrons and ions are focused on the central portion due to the high electrolytic distribution at the central portion, the sputtering effect of the ions on the side wall of the plasma chamber is small, and a highly clean plasma can be obtained. ECR plasma chamber 1
The ions generated in 3 are accelerated by a mesh-shaped extraction electrode section 16 and irradiated on a sample 17. Sample holder 18
Can be rotated 360 ° about the vertical direction by the manipulator 19, and the direction of the ion beam incident on the sample can be changed.

FIG. 1 is a structural perspective view of a semiconductor laser showing one embodiment of the present invention. On an n-type GaAs substrate 1, an n-type ZnSe layer 2, Zn
This is a structure in which an S _X Te _1-X (X = 0.35) layer 3 and a p-type ZnSe layer 4 are laminated, and reference numerals 5 and 6 are n-type and p-type ohmic electrodes, respectively. ZnSe and ZnS _X Te _1-X (X = 0.35) have substantially the same lattice constant, and the energy gap of ZnSe is about 0.2 eV larger, so that the ZnSe layer functions as a cladding layer. Optical resonance surface 7
Is formed by the reactive ion beam etching method according to the present invention. 2 (a) to 2 (d) show the steps for manufacturing the device of FIG. First, Si-doped Ga
In or Ga doped ZnSe layer 2, ZnS _X Te on As substrate 1
_{A 1-X} (X = 0.35) layer 3 and an N-doped ZnSe layer 4 are laminated by a molecular beam epitaxial growth method or the like, and then an n-type electrode 5 and a p-type electrode 6 are formed. Next, a photoresist (positive type) 8 is coated on the entire surface of the substrate,
Bake for ~ 120 minutes. Then, Ti9 is formed by an electron beam evaporation method of about 1000 A or the like. (FIG. 2 (a)) Next, as shown in FIG. 2 (b), a pattern of the photoresist 10 is formed by a normal photolithography process. Next, Ti9 is etched using the photoresist 10 as a mask.

The etching method uses a buffered hydrofluoric acid solution for wet etching, and the reactive ion etching (RIE) method using CF ₄ gas for dry etching. Slight dry etching is more desirable. Then, using the Ti9 as a mask, the etching of the photoresist 8 is performed by the RIE method using oxygen plasma. (FIG. 2 (c)) At this time, what should be noted is the pressure of the oxygen gas. When an ordinary parallel plate type dry etching apparatus is used for producing an etching mask having a vertical cross-sectional shape without a taper, the pressure of oxygen gas is preferably about 5 Pa. If the pressure is too high, the etching proceeds isotropically, which is not suitable in this case. Photoresist 8
The Ti9 used as an etching mask is removed with a buffered hydrofluoric acid solution or the like.

Next, reactive ion beam etching is performed. Pure chlorine gas (99.999%) as etching gas, gas pressure 1 ×
Etching was performed under the conditions of 10 ^-1 Pa, a microwave incident power of 200 W, an extraction voltage of 400 V, and an ion beam incident direction perpendicular to the substrate. At this time, the etching rate of ZnSe and ZnSTe was about 850 A / min, and that of the photoresist was about 250 A / min.
The photoresist mask 10 has a vertical section, and ZnSe and ZnST
Since e is constant-velocity etching, a smooth vertical end face can be obtained even at the heterojunction interface as shown in FIG. 2 (d). This vertical end face is smooth at the atomic plane level,
In addition, it is hardly damaged by etching, and can be used as a resonance surface of a semiconductor laser. Also, the mask is made by a somewhat complicated process here,
The reason is that when a photoresist is used as a mask, a vertical cross section cannot be obtained because a mask manufactured by a normal photolithography process has a taper.

Thereafter, the remaining photoresist is removed by ashing or the like, and the device is separated by cleavage or the like, whereby the device shown in FIG. 1 is completed. Since this cleavage is a mere separation step, it is not required to be as rigorous as in the conventional production of a resonance surface.

The etching conditions which are vertical, smooth and have little damage as described above are as follows. First, as for the gas pressure, if the mean free path between the ion beam and the neutral particles is substantially the same, the directivity of the etching will be lost, and a practical etching rate will be obtained.
The pressure is preferably from 10 ⁻³ Pa to 1 Pa. With respect to the microwave incident output, if the output is too high, the plasma temperature rises and the electrode is thermally deformed, and the substrate temperature also increases due to radiant heat, making temperature control difficult. The extraction voltage is preferably 0 V or more and 1000 V or less, since if it is too high, the substrate will be greatly damaged. Especially II-VI
Since the constituent elements of the group III compound semiconductors have high ionicity, they easily react chemically with halogen elements such as Cl, and because of the high rate of separation from the material surface due to the vapor pressure of the reaction product and the progress of etching, the energy of ions Is small. For this reason, etching proceeds even at a low extraction voltage,
Etching with less damage is achieved as compared to III-V compound semiconductors such as GaAs. Most of the halides of the constituent elements of the II-VI compound semiconductor form a reaction product combined with two halogen elements. For example, ZnSe
The chlorides of Zn and Se form ZnCl ₂ and SeCl ₂ . Since these reaction products are not very active chemically, the effect of protecting the etching of the side wall is greater than that of a III-V compound semiconductor such as GaAs, the anisotropic etching is strong, and a vertical cross section is easily obtained.

Regarding the substrate temperature above 80 ° C, ZnCl _X , SeCl _X , Te
The side wall protective film such as Cl _X evaporates, and the ions scattered on the surface cause uneven etching of the side surface, resulting in rough morphology, which is not appropriate. On the other hand, when the temperature is 0 ° C. or lower, the substrate temperature becomes too low than the ambient temperature, and contamination such as adhesion of chlorine gas becomes large.

In the present embodiment, Zn is used as the II-VI group compound semiconductor.
Although Se and ZnSTe have been described, other II-VI compound semiconductors such as ZnSSe and CdTe are also effective. Also, the description has been made using a photoresist as an etching mask. However, when a material having a selectivity with respect to a material to be etched, for example, ZnSe is used as a material to be etched, SiO _x ,
Insulator such as SiN _X, Mo, is also valid for metals such as Ni. Although pure chlorine gas is used as an etching gas, a gas containing a halogen element, for example, BCl ₃ , CCl ₂
F ₂ , etc. In addition, the structure of the light-emitting element can be applied to any end-emission type.

[Effects of the Invention] As described above, according to the present invention, the following effects can be obtained.

(1) Since the resonance surface is manufactured by a dry process, reproducibility and yield are remarkably improved as compared with the conventional cleavage process.

(2) Since the length of the optical resonator is determined by the accuracy of the photolithography process, the accuracy is improved as compared with the conventional mechanical accuracy,
Miniaturization is also possible.

(3) Monolithic integration of light emitting elements and electronic devices is possible.

(4) The screening can be performed on a wafer basis, and the manufacturing cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a structural perspective view of a semiconductor laser showing one embodiment of the present invention. FIGS. 2 (a) to 2 (d) are views showing steps for manufacturing the semiconductor laser of FIG. FIG. 3 is a schematic diagram illustrating the configuration of an etching apparatus used in an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1 ... n-type GaAs substrate 2 ... n-type ZnSe layer 3 ... ZnS _X Te1 _-X (X = 0.35) layer 4 ... p-type ZnSe layer 5 ... n-type electrode 6 ... p-type electrode 7 ... ... Optical resonance surface 8 ... Photoresist 9 ... Ti layer 10 ... Photoresist 11 ... Sample preparation room 12 ... Etching room 13 ... ECR plasma generation room 14 ... Electromagnet 15 ... Microwave waveguide 16 ... … Extraction electrode 17… Sample 18… Sample holder 19… Manipulator 20… Gas inlet 21… Transport rod 22… Exhaust system 23… Exhaust system 24… Gate valve

Claims (7)

(57) [Claims] 1. A method of manufacturing a semiconductor light emitting device having an optical resonator structure using a II-VI group compound semiconductor, comprising the steps of: forming an etching mask;・ Activate in the ECR plasma chamber, extract the ion beam at an extraction voltage of 0 V or more and 1 kV or less,
A step of performing dry etching by irradiating the material to be processed comprising the II-VI compound semiconductor with a uniform direction with the ion beam to form the optical resonator reflection surface by a step of performing dry etching. Production method. 2. The method according to claim 1, wherein the material of the etching mask is an insulator or a metal. 3. The method according to claim 1, wherein the material of the etching mask is photoresist, silicon oxide, silicon nitride, molybdenum, or nickel. 4. The method according to claim 1, wherein the reactive gas contains at least a halogen element. 5. The pressure of the reactive gas is from 5 × 10 ⁻³ Pa.
2. The method according to claim 1, wherein the pressure is in the range of 1 Pa. 6. The method for manufacturing a semiconductor light emitting device according to claim 1, wherein the incident power of the microwave is in a range of 1 W or more and 1 kW or less. 7. The method of manufacturing a semiconductor light emitting device according to claim 1, wherein the substrate temperature at the time of etching the material to be processed is set to 0 ° C. or more and 80 ° C. or less.