KR20050091584A - Method for growing compound semiconductor thin film layer using metal organic chemical vapor deposition and laser diode manufactured by the same - Google Patents

Abstract

The present invention relates to a compound semiconductor thin film growth method using an organometallic chemical vapor deposition method and a compound semiconductor laser diode produced by the method. In the method for growing a compound semiconductor thin film according to the present invention, an epi substrate is first introduced into a deposition chamber. Then, the pressure inside the deposition chamber is stabilized while mainly injecting the Group 5 source gas into the deposition chamber. Subsequently, while injecting the Group 5 source gas mainly into the deposition chamber, the temperature of the deposition chamber is increased to the thin film growth temperature of the compound semiconductor. Then, the temperature inside the deposition chamber is stabilized while injecting a group 5 source gas and a carrier gas into the deposition chamber. Finally, the Group 3 organometallic source gas, which reacts with the Group 5 source gas, the carrier gas, and the Group 5 source gas to form a compound semiconductor thin film on the epitaxial substrate, is injected into the deposition chamber.

According to the present invention, a defect-free compound semiconductor thin film having good interfacial properties and no defects can be grown on an epitaxial substrate having a diffraction grating.

Description

TECHNICAL FOR GROWING COMPOUND SEMICONDUCTOR THIN FILM LAYER USING METAL ORGANIC CHEMICAL VAPOR DEPOSITION AND LASER DIODE MANUFACTURED BY THE SAME}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the manufacture of compound semiconductor laser diodes for optical communication, and more particularly, a method of stably growing a compound semiconductor thin film on an epitaxial substrate having a diffraction grating using a MOCVD method and a compound semiconductor manufactured by the method. For laser diodes.

In general, strict optical wavelength control is required in long distance, high capacity, and high speed optical communication. Recently, laser diodes made of compound semiconductors have been widely used as optical modulation devices. Representative examples of such laser diodes include a distributed-feedback laser diode (DFB laser diode) and a distributed Bragg reflector (DBR laser diode).

The laser diode (hereinafter referred to as DFB and DBR laser diodes together) has a structure in which an optical waveguide and a wavelength selection diffraction grating are combined to suppress light dispersion and modulate an electrical signal into short wavelength light. It is characterized by. Therefore, in the initial manufacturing process of the laser diode, the epitaxial substrate is artificially etched to form a diffraction grating, and then the compound semiconductor thin film is grown to a predetermined thickness by a MOCVD method, and a photolithography process is applied to the laser diode. Will form.

More specifically, in the conventional process of growing a compound semiconductor thin film using an MOCVD method on an epitaxial grating substrate, the epitaxial grating on which the diffraction grating is formed is introduced into the deposition chamber by an etching process, and then the carrier gas is stored at room temperature. Is injected sufficiently into the deposition chamber to maintain an appropriate pressure for thin film growth. Then, while injecting the Group 5 source gas, the internal temperature of the deposition chamber is increased to the growth temperature of the thin film. In this process, the interior of the deposition chamber is filled with a large amount of carrier gas and a small amount of Group 5 source gas.

When the internal temperature of the deposition chamber rises to a temperature suitable for thin film growth, a temperature stabilization step is performed for a predetermined time, and then a Group 3 organometallic source gas is injected into the chamber. Then, the group 3-5 compound semiconductor is grown to a predetermined thickness on the epitaxial substrate.

However, when the applicant applies the thin film growth method as described above, not only the interface property between the diffraction grating and the thin film is deteriorated, but also the material film is grown in the form of grain without growing the material film in atomic layer units in the thin film. It was confirmed that there is a limit in which grain defects occur.

This limitation is due to the unstable crystal lattice that is released to the outside of the material atoms (e.g., In atoms in the case of InP substrates) of the epi substrate during the heating of the epi substrate to the thin film growth temperature of the compound semiconductor. Material exchange is expected to occur because the material atoms bond to each other to grow into grain (eg, In grain for InP substrates).

Therefore, before the growth of the compound semiconductor thin film, an additional chemical etching process is applied to remove the crystal lattice damage layer on the epitaxial substrate, and when the temperature of the deposition chamber is increased to the thin film growth temperature, the temperature increase rate is variously changed to epi. A method of stabilizing crystal lattice damage on the substrate has been proposed.

However, the former method has a problem that the yield is reduced and the manufacturing cost is increased because a separate process must be added, and the latter method is not suitable for mass production due to the poor process reproducibility.

Therefore, the present invention was devised to solve the above-described problems of the prior art, and in the initial process for manufacturing a laser diode having a diffraction grating, the compound semiconductor thin film is stable on the epi substrate on which the diffraction grating is formed by using a MOCVD method. And a compound semiconductor laser diode produced by this method.

The compound semiconductor thin film growth method using the organometallic chemical vapor deposition method according to the present invention for achieving the above technical problem, (a) introducing an epi substrate into the deposition chamber; (b) stabilizing the pressure inside the deposition chamber while mainly injecting a Group 5 source gas into the deposition chamber; (c) raising the temperature of the deposition chamber to the thin film growth temperature of the compound semiconductor while injecting the Group 5 source gas mainly into the deposition chamber: (d) injecting the Group 5 source gas and the carrier gas into the deposition chamber Stabilizing the internal temperature; And (e) injecting a Group III organometallic source gas into the deposition chamber to react with the Group 5 source gas, the carrier gas, and the Group 5 source gas to form a compound semiconductor thin film on the epitaxial substrate. It characterized in that it comprises a step.

In the present invention, the Group 5 source gas may be a PH ₃ gas, AsH ₃ gas or a mixture thereof. The Group 3 organometallic source gas may be triethylgallium gas, trimethylgallium gas, triethylindium gas, trimethylindium gas, or a mixture thereof.

In the step (b) it is preferable to stabilize the pressure in the deposition chamber to 30 ~ 80 torr.

In the step (c), it is preferable to increase the temperature of the deposition chamber to 560 ~ 640 ℃.

In the step (d), it is preferable to stabilize the temperature by maintaining the temperature of the deposition chamber for 2 to 6 minutes while gradually increasing the flow rate of the carrier gas to 10 to 30 l / min.

In (b) or (c), the carrier gas may be further injected into the deposition chamber. In this case, the flow rate of the carrier gas is preferably smaller than the flow rate of the Group 5 source gas.

According to the present invention, the epi substrate may be an artificially etched epi substrate, including a diffraction grating thereon.

The present invention provides a compound semiconductor laser diode manufactured by the compound semiconductor thin film growth method described above in order to achieve the above technical problem.

The laser diode may be a distributed feedback laser diode or a distributed Bragg reflective laser diode.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, terms or words used in the present specification and claims should not be construed as being limited to the common or dictionary meanings, and the inventors should properly explain the concept of terms in order to best explain their own invention. Based on the principle that can be defined, it should be interpreted as meaning and concept corresponding to the technical idea of the present invention. Therefore, the embodiments described in the specification and the drawings shown in the drawings are only the most preferred embodiments of the present invention and do not represent all of the technical idea of the present invention, various equivalents that may be substituted for them at the time of the present application It should be understood that there may be water and variations.

1 is a diagram illustrating each process step for a method of growing a compound semiconductor thin film using the MOCVD method according to the present invention in a time (X axis) and a temperature (Y axis) graph, and FIG. 2 is a gas supply method of each process step. The table shows.

1 and 2, the present invention first introduces an epitaxial substrate having a diffraction grating formed thereon into an deposition chamber by an etching process. The epi substrate may be an InP substrate or a GaAs substrate, but is not limited thereto.

Then at room temperature while stabilizing the pressure in the chamber while injecting mainly the Group 5 source gas into the deposition chamber (①). At this time, the pressure of the deposition chamber is preferably stabilized to 30 ~ 80 torr. Here, the Group 5 source gas may be a PH ₃ gas, an AsH ₃ gas, or a mixed gas thereof, but is not limited thereto.

Optionally, a small amount of inert carrier gas may be further injected into the deposition chamber during the pressure stabilization step. In this case, the flow rate of the carrier gas is preferably smaller than the flow rate of the Group 5 source gas. The flow rate of the carrier gas can be adjusted to 0.1 ~ 5L / min or less, and the carrier gas may be employed H ₂ gas, N ₂ gas or a mixture thereof, but is not limited thereto (the same).

After the pressure of the deposition chamber is stabilized, the temperature of the deposition chamber is gradually raised to the compound semiconductor thin film growth temperature while injecting a group 5 source gas into the deposition chamber under the same conditions as the pressure stabilization step (2). At this time, the temperature of the deposition chamber is preferably raised to 560 ~ 640 ℃.

Optionally, a small amount of inert carrier gas may be further injected into the deposition chamber when the temperature raising step ② is performed. In this case, the flow rate of the carrier gas is preferably smaller than the flow rate of the Group 5 source gas. The flow rate of the carrier gas is adjustable to 0.1 ~ 5l / min or less.

When the temperature rise step ② proceeds, a large amount of Group 5 source gas is present in the chamber. Therefore, in the process of heating the epi substrate, Group 5 source gas is chemically and / or physically adsorbed on the surface of the epi substrate, particularly the diffraction grating surface generated by the etching process. This prevents the material of the epi substrate from being released to the outside of the lattice site of the unstable crystal lattice exposed to the surface of the epi substrate, or prevents material atoms in the adjacent crystal lattice from bonding to each other and growing in grain units. This is because the Group 5 elements contained in the Group 5 source gas adsorbed to the lattice sites exposed to the outside of the unstable crystal lattice are bonded to the crystal lattice sites to stabilize the crystal lattice.

In view of this, when the carrier gas is further injected during the temperature raising step (②), the flow rate is adjusted to prevent the stabilization of the crystal lattice damage on the upper surface of the epitaxial substrate by the Group 5 source gas. It is preferable.

After the temperature of the deposition chamber is raised to the thin film growth temperature, the temperature of the deposition chamber is stabilized while injecting group 5 source gas and carrier gas into the deposition chamber at the same time (③). This temperature stabilization step preferably lasts 2-6 min. In addition, the flow rate of the carrier gas is preferably gradually increased gradually to the flow rate required for thin film growth of the compound semiconductor, that is, 10 to 30 L / min.

After the temperature of the deposition chamber is stabilized, the Group III organic material may form a compound semiconductor thin film in atomic layer units on the epi substrate by reacting with the Group 5 source gas while introducing the carrier gas and the Group 5 source gas into the deposition chamber. The metal source gas is injected into the deposition chamber for a predetermined time. The Group 3 organometallic source gas may be triethylindium gas, trimethylindium gas, triethylgallium gas, trimethylgallium gas, or a mixture thereof, but is not limited thereto.

As described above, when the group III organometallic source gas is injected into the deposition chamber for a predetermined time, the compound semiconductor thin film is grown to a predetermined thickness on the epitaxial substrate.

This completes the compound semiconductor thin film growth process using the organometallic chemical vapor deposition method according to the present invention.

In the present invention, the Group 5 source gas is present in a large amount in the deposition chamber during the pressure stabilization step (①), the temperature rising step (②) and the temperature stabilization step (③) of the deposition chamber. Therefore, the crystal lattice damage caused on the epitaxial substrate during the formation of the diffraction grating is stabilized by the Group 5 source gas before the thin film growth step is substantially progressed. As a result, a defect-free compound semiconductor thin film having excellent interfacial characteristics with the diffraction grating and no grain defects is obtained on the epitaxial substrate.

Experimental Example

The Applicant obtained Samples 1 and 2, respectively, by forming a compound semiconductor thin film on an epitaxial substrate having a diffraction grating using the compound semiconductor thin film growth method according to the prior art and the present invention as follows.

Preparation of Sample 1

First, the InP epi substrate was introduced into the deposition chamber, and the carrier gas H ₂ gas was injected at a flow rate of 20 l / min until the pressure in the chamber became 60 torr at room temperature (25 ° C.), and the pressure was maintained for 5 minutes (pressure Stabilization step). Then, the temperature of the deposition chamber was maintained for 3 minutes while maintaining the flow rate of the carrier gas and the pressure of the deposition chamber, while introducing PH ₃ gas and AsH ₃ gas into the deposition chamber at flow rates of 270 sccm and 27 sccm, respectively, as a group 5 source gas. Increased to 600 ° C. (temperature rise step). Then, the temperature was stabilized for 3 minutes while maintaining the flow rates of the carrier gas and the Group 5 source gas, and the temperature and pressure of the deposition chamber (temperature stabilization step). In that the pressure and temperature of the deposition chamber after the maintained state, PH ₃ gas, and trimethyl indium gas the AsH ₃ gas as each 270 sccm and the flow rate of Group III metal organic source gas and injected into the deposition chamber in a 17 sccm and tree Ethyl gallium gas was injected into the deposition chamber at flow rates of 200 sccm and 27 sccm, respectively, to grow a compound semiconductor thin film on an InP epitaxial substrate to obtain Sample 1 (thin film growth step).

<Preparation of Sample 2>

First, the InP epi substrate was introduced into the deposition chamber, and PH ₃ gas and AsH ₃ gas were injected at a flow rate of 270 sccm and 27 sccm, respectively, as a Group 5 source gas until the pressure in the chamber became 60 torr at room temperature (25 ° C). This pressure was maintained for 5 minutes (pressure stabilization step). The temperature of the deposition chamber was then increased to 600 ° C. for 3 minutes while maintaining the flow rate of the Group 5 source gas and the pressure of the deposition chamber (temperature raising step). Then, the temperature in the deposition chamber was stabilized (temperature stabilization step) by gradually increasing the carrier gas, H ₂ gas, until the flow rate became 20 L / min while maintaining the temperature of the deposition chamber at 600 ° C. for 3 minutes. In that the pressure and temperature of the deposition chamber after the maintained state, PH ₃ gas, and trimethyl indium gas the AsH ₃ gas as each 270 sccm and the flow rate of Group III metal organic source gas and injected into the deposition chamber in a 17 sccm and tree Ethyl gallium gas was injected into the deposition chamber at a flow rate of 200 sccm and 27 sccm, respectively, to grow a compound semiconductor thin film on an InP epi substrate to obtain Sample 2. (Thin film growth step).

As described above, samples 1 and 2 were obtained, and the cross sections of the InP epitaxial substrate were observed with an electron microscope to obtain photographs shown in FIGS. 3 (sample 1) and 4 (sample 2).

3 and 4, the compound semiconductor thin film grown by the prior art has a deteriorated interface property with the diffraction grating, whereas the compound semiconductor thin film grown by the present invention has excellent interfacial properties and growth of the thin film. It can be seen that it is made uniform.

In addition, the upper surfaces of Samples 1 and 2 were observed with an optical microscope to obtain photographs shown in FIGS. 5 (Sample 1) and 6 (Sample 2).

5 and 6, it can be seen that in the compound semiconductor thin film grown by the prior art, grain defects grown in grain units instead of atomic layer units are distributed throughout the thin film. In contrast, the compound semiconductor thin film grown by the present invention can be confirmed that the entire thin film is uniformly grown in atomic layer units without grain defects.

As described above, although the present invention has been described by way of limited embodiments and drawings, the present invention is not limited thereto and is intended by those skilled in the art to which the present invention pertains. Of course, various modifications and variations are possible within the scope of equivalents of the claims to be described.

According to the present invention, the compound semiconductor thin film is grown after stabilizing the crystal lattice damage on the epitaxial substrate on which the diffraction grating is formed, thereby obtaining a defect-free compound semiconductor thin film having good interface characteristics and no defects.

The following drawings attached to this specification are illustrative of preferred embodiments of the present invention, and together with the detailed description of the invention to serve to further understand the technical spirit of the present invention, the present invention is a matter described in such drawings It should not be construed as limited to.

1 shows each process step for a method of growing a compound semiconductor thin film using a metal organic chemical vapor deposition (MOCVD) method according to an embodiment of the present invention (time (X-axis) and temperature (Y-axis) ) Is a diagram shown in a graph.

2 is a table showing a gas supply method of each process step.

3 and 4 are photographs obtained by observing the cross section of the epitaxial substrate with an electron microscope after growing the compound semiconductor thin film on the epitaxial substrate, respectively, according to the prior art and the present invention.

5 and 6 are photographs of the upper surface of the epitaxial substrate observed with an optical microscope after the growth of the compound semiconductor thin film on the epitaxial substrate according to the prior art and the present invention, respectively.

Claims (11)

(a) introducing an epitaxial substrate into the deposition chamber; (b) stabilizing the pressure inside the deposition chamber while mainly injecting a Group 5 source gas into the deposition chamber; (c) increasing the temperature of the deposition chamber to the growth temperature of the compound semiconductor thin film while injecting the Group 5 source gas mainly into the deposition chamber; (d) stabilizing the temperature inside the deposition chamber while injecting a Group 5 source gas and a carrier gas into the deposition chamber; And (e) injecting a Group 5 source gas, a carrier gas, and a Group 3 organometallic source gas into the deposition chamber into which the compound semiconductor thin film may be formed on the epitaxial substrate in atomic layer units. Method of growing a compound semiconductor thin film using an organometallic chemical vapor deposition method comprising a. The method of claim 1, The method of growing a compound semiconductor thin film using an organometallic chemical vapor deposition method, characterized in that the Group 5 source gas is PH ₃ gas, AsH ₃ gas or a mixture thereof. The method of claim 1, The Group 3 organometallic source gas is trimethyl indium gas, triethyl indium gas, trimethyl gallium gas, triethyl gallium gas or a mixed gas thereof, a compound semiconductor thin film manufacturing method using an organic metal chemical vapor deposition method. The method of claim 1, Wherein the carrier gas is H ₂ gas, N ₂ gas or a mixture of these, a compound semiconductor thin film manufacturing method using an organic metal chemical vapor deposition method. According to claim 1, wherein step (b), Method of manufacturing a compound semiconductor thin film using an organometallic chemical vapor deposition method characterized in that the step of stabilizing the pressure of the deposition chamber to 30 ~ 80 torr. The method of claim 1, wherein step (c) comprises: Method of manufacturing a compound semiconductor thin film using an organometallic chemical vapor deposition method characterized in that the step of increasing the temperature of the deposition chamber to 560 ~ 640 ℃. The method of claim 1, wherein step (d) Compound semiconductor thin film manufacturing using an organometallic chemical vapor deposition method characterized in that the step of stabilizing the temperature by maintaining the temperature of the deposition chamber for 2 to 6 minutes while gradually increasing the flow rate of the carrier gas to 10 ~ 30 l / min Way. The method of claim 1, wherein in steps (b) and (c), A method of manufacturing a compound semiconductor thin film using an organometallic chemical vapor deposition method, characterized by further injecting a carrier gas into the deposition chamber at a flow rate relatively smaller than that of the Group 5 source gas. The method of claim 1, The epitaxial substrate is a compound semiconductor thin film manufacturing method using an organometallic chemical vapor deposition method, characterized in that the epitaxial substrate is an artificially etched epitaxial substrate comprising a diffraction grating. A compound semiconductor laser diode produced by the method according to any one of claims 1 to 9. The method of claim 10, And the compound semiconductor laser diode is a distributed feedback laser diode or a distributed Bragg reflective laser diode.