JPH02260416A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To obtain a manufacturing method, of a semiconductor device, which can be automated and which can comply with an integration operation by a method wherein a semiconductor crystal layer is formed selectively by a vapor growth method in which raw-material gases are supplied alternately. CONSTITUTION:A silicon oxide film (SiO2 film) 12 is formed on the whole sur face of an n-type GaAs (100) wafer 11 by using a vapor deposition method; then, the silicon oxide film 12 is removed selectively by using a reactive ion etching method; a groove whose depth reaches the substrate 11 and whose wall faces are all perpendicular to the wafer and are flat is formed. Then, a semiconductor crystal layer 13 having a laser structure is laminated in the groove part by using a vapor growth method in which raw-material gases are supplied alternately; lastly, the water is immersed in a solution of ammonium fluoride; the silicon oxide film 12 which has been formed at the beginning is removed; an electrode is formed. Since a cleavage process is not used in this manner, a manufacturing process can be automated and a semiconductor laser can be integrated in an arbitrary direction on the wafer.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to a method for manufacturing a semiconductor device.

(Conventional Technique Wi) For example, when manufacturing a semiconductor laser device, after forming a semiconductor crystal layer with a desired structure on a wafer, the wafer is divided by cleavage, and laser resonator end faces are formed at that time. Common. However, the cleavage process is automated and is a K-peel process. Another problem is that a plurality of semiconductor lasers cannot be freely integrated on the same chip using a cleavage process. Therefore, there is a need for an end face forming method that can replace the cleavage process.

In the process of forming the laser resonator end face, it is necessary to form a flat surface perpendicular to the wafer with a height of at least several μm. It is very difficult to form such a shape using normal etching methods.

Therefore, attempts are being made to form such surfaces using beams of electrons, ions, light, etc. Among these, research on end face formation using ions is particularly progressing. A plasma is formed with a gas containing a gas that has the property of removing the substrate, and the reactive ions generated there are accelerated by an electric field generated between the plasma and the substrate or by an electric field applied from the outside. The idea is to collide with the object to form a perpendicular surface. Since the ions accelerated in this manner collide with the substrate, the crystals of the substrate at the end face were significantly damaged by radiation. Therefore, there is a problem in that characteristics such as the threshold value and lifetime of the semiconductor laser are deteriorated.

Efforts have been made to lower the ion energy using electron cyclotron resonance, but it has not been possible to eliminate irradiation damage while maintaining a good end face shape. Etching methods using electron beams or light are also being researched, but the research has just begun and will not be put to practical use any time soon.

In order to eliminate the radiation damage described above, the following method can be devised instead of directly processing the semiconductor crystal layer that will become the laser using a beam process. That is, first, a pre-formed thin film or the substrate itself is processed using a one-beam process or the like to form a mold having a shape of a laser end face with flat and parallel opposing wall surfaces. A conceivable method is to embed a semiconductor crystal layer that will become a laser therein, and then remove unnecessary portions of the initially formed mold to form an end face. In this case, it is necessary to embed the semiconductor crystal layer in a predetermined portion with a uniform thickness and without gaps.

However, with conventional crystal growth methods, the growth rate increases significantly at the edges of the grown region, and there are areas where no growth occurs, making it impossible to perform uniform buried growth, and it is difficult to achieve the desired laser structure. could not be formed.

(Problems to be Solved by the Invention) As described above, it has not been possible to manufacture a semiconductor laser with sufficient characteristics without using a cleavage process. This cleavage process is difficult to automate, and there is also the problem that it cannot cope with the integration of optical lasers that will be required in the future.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing a semiconductor device that eliminates the above problems, can be automated, and is compatible with integration.

[Structure of the invention]

(Means for Solving the Problems) The present invention provides a method for manufacturing a semiconductor device in which a semiconductor crystal layer is selectively formed by a vapor phase growth method in which source gases are alternately supplied.

(Function) In the vapor phase growth method in which raw material gases are alternately supplied, it is possible to epitaxially grow only one atomic layer with one alternate supply of raw material gases.

Using this method, the film thickness can be controlled in units of atomic layers regardless of the shape of the pattern. At this time, the film thickness becomes uniform within the wafer surface with atomic layer precision.

Therefore, according to the present invention, a mold having a laser end face shape in which the opposing wall surfaces of the set are flat and parallel is formed, and a laser is formed using a growth method that controls the film thickness in units of atomic layers. By embedding the semiconductor crystal layer, a semiconductor laser having a good end face can be manufactured without using a cleavage process.

Therefore, it becomes possible to automate all processes without degrading the characteristics of the semiconductor laser. Furthermore, it becomes possible to test devices manufactured using wafers as they are. Also,
It also becomes easier to integrate semiconductor lasers.

(Example) A first embodiment of the first invention will be described with reference to the drawings.

FIG. 1 shows that using the present invention, a large number of GaAs are present in a wafer.
This figure shows an outline of the process for manufacturing an lAs semiconductor laser.

First, as shown in Figure 1(a), n-type GaAs (10
0) A silicon oxide film (S i O, film) 12 having a thickness of 5 μm was formed on the entire surface of the wafer 11 using a vapor deposition method.

Next, as shown in FIG. 1(b), the silicon oxide film was selectively removed using a reactive ion etching method, and the lateral 10
A flat trench was formed with a depth of 300 μm per μm and a depth that reached the substrate, with all walls perpendicular to the wafer. The directions of the grooves are not constant, but are arranged in various directions on the wafer.

Next, as shown in FIG. 1C, a semiconductor crystal layer 13 having a laser structure was laminated in the groove portion by a vapor phase growth method in which raw material gas was alternately supplied.

Finally, as shown in FIG. 1(d), the wafer was soaked in an ammonium fluoride solution to remove the initially formed silicon oxide film, and electrodes were formed to complete the semiconductor laser device.

In the following, a vapor phase growth method in which raw material gases are alternately supplied is used.
The process of forming the semiconductor crystal layer in the groove will be described in detail.

Figure 2 shows the metal organic chemical vapor deposition (MOC) used in the above process.
FIG. 2 is a schematic diagram showing a VD) device. Reference numeral 31 in the figure is a quartz growth container to which a cylindrical body 32 is integrally attached. A susceptor 34 is disposed within the container 31 and is moved up and down by a drive shaft 33. Gas introduction pipes 35 and 36 are connected to the side walls of the cylindrical body 32 of the growth container 31, respectively.

Note that the gas introduction pipe 3 on the upper side connected to the cylindrical body 32
Hydrogen and inert gas are supplied from 5 to prevent film growth on the inner surface of a light introduction window, which will be described later, and which is arranged above the cylindrical body 32. An exhaust member 37 is connected to a lower side wall of the growth container 31 . A high frequency heating coil 38 is wound around the growth container 31. A light introduction window 39 is arranged at the top of the cylindrical body 32 .

Further, 40 in the figure is an excimer laser that emits KrF excimer laser light 41, and the laser light 4 is on the optical path.
A reflecting mirror 42 is arranged to irradiate the inside of the container 31 with 1 through the light introduction window 39.

Next, a method of forming a semiconductor crystal layer in the wafer groove using the MOCVD apparatus described above will be described.

First, after holding the wafer 43 with grooves formed on the susceptor 34, the exhaust member 37 is activated to maintain the pressure inside the growth container 31 at 49 Torr, and 151 m of hydrogen is supplied into the container 31 from the gas introduction pipe 35. .

Arsine was supplied at 509 sec cm from the gas introduction pipe 36, and the wafer 43 was heated to 700'C by the high frequency filter 38 to perform annealing for 20 minutes.

Next, the temperature of the wafer 43 is maintained at 500° C., hydrogen is supplied at 1 am from the gas introduction pipe 35, and source gas and hydrogen are supplied from the gas introduction pipe 36 to the growth container 31 in a certain sequence described later.
The wavelength is 248r1m from the excimer laser 40.
A mirror 42 reflects the excimer laser beam 41, and a light introduction window 3
9 was irradiated perpendicularly to the wafer 43 to form a semiconductor crystal layer.

The sequence of introducing the raw material gas from the gas introduction pipe 36 is as follows:
Introducing group raw material gas for 0.5 seconds (step 1), introducing hydrogen for 0.5 seconds.
Introduction of 5 seconds (process 2), introduction of group V source gas for 0.5 seconds (process 3), and introduction of hydrogen for 0.5 seconds (process 4).
It repeats as a cycle. At this time, the flow rate of hydrogen and the exhaust speed of the exhaust member 37 were adjusted so that the total flow rate of the introduced gases was always 2.751 m and the pressure in the growth container 31 was 40 Torr. Further, in process 1, the laser beam 41 was irradiated with an intensity of 20 m J /Cm'' and a rate of 80 pulses/second.

The sequence of introducing raw material gas for forming the semiconductor crystal layer 13 having a laser structure was performed as follows.

First, in step I, triethylgallinm (TEG) is introduced at IXIQ'mol/cycle, and in step 3, arsine and disilane are introduced at 1XIQ4mol/cycle and 1xlo'mol/cycle, respectively.The above cycle is repeated 3000 times to determine the film thickness. A 0.84 μm n-type GaAs silicon fluoride layer was formed, and then, in step I, TBG and trimethylaluminum (1M) were introduced at txt & mol/cycle and 2XIQ” mol/cycle, respectively, and in step 1, arsine and silane were introduced. respectively l×lrPmO1/cycle, 1×IQ
The above-mentioned cycle of introducing the film at 1.26 μm in thickness was repeated 4500 times to form an n-type AI with a film thickness of 1.26 μm.
A GaAs cladding layer was formed. Then, in step 1, TEG was introduced at t x [f”m o l /cycle, and in step 3, arsine was introduced at lxlpm
The above-mentioned cycle of introduction at 1/1 cycle was repeated 4000 times to form a GaAs active layer with a thickness of 0.102 μm. Then, in step 1, TEG and TMA, diethylzinc (DBZ) were dissolved 1X 1ff'mol/cycle, 2XIO'mO1/cycle, 1x lff'm
o 1/' cycle, and in step 3, arsine was introduced at IXI Pno 1/cycle. The above cycle was repeated 4500 times to form a p-type AlGaAs film with a film thickness of 1.26 μm.

A layer was formed. Finally, in step 1, TEG and DEZ were each txl (T'mol/cycle, Ix
The above cycle of introducing irrnol/cycle and introducing arsine at l×I Om o 1/cycle in step 3 was repeated 2000 times to obtain a film thickness of 0.56μ.
A cross-section of a part of the wafer on which the 0 2 semiconductor laser structure was formed was observed with a scanning electron microscope, and it was confirmed that the desired structure with a good end facet was formed.

One electrode was attached to this wafer and a laser oscillation test was conducted.

All lasers oscillate with direct current, and their threshold current is 30
It was distributed from mA to 50mA. This is comparable to a semiconductor laser device manufactured using a cleavage process. Also,
Since the characteristics of the laser did not depend on the direction of the laser, it was confirmed that a semiconductor laser device could be fabricated in any direction with respect to the crystal orientation of the substrate.

In the manufacturing method described so far, a silicon oxide film was used to form a mold having the shape of the end face of the laser, but almost the same results were obtained using a silicon nitride film.

Next, a second embodiment of the present invention will be described with reference to FIG. 3, in which a GaAs crystal layer is formed in advance and a mold having the end face shape of the laser is formed thereon.

First, as shown in FIG. 3(a), an n-type A10.3Ga
O, 7 peoples (100) The aforementioned oMOc is placed on the entire surface of the substrate 51.
A GaAs crystal layer 52 having a thickness of 5 m was formed using a VD apparatus. However, TEG and arsine used as raw material gases were continuously supplied at the same time, and laser light was also continuously irradiated during the growth. The supply amount of TEG and arsine is 2×1 each.
01 mol/min, 2×10 mol/min. Next, as shown in FIG. 3(b), the () a A s
The film 52 was selectively removed to form a flat trench measuring io μm in width and 300 μm in length, with a depth that reached the substrate, and whose end face was perpendicular to the wafer. Similar to the above-described embodiment, the direction of the grooves is not constant, but is arranged in various directions on the wafer.

Next, as shown in FIG. 3(C), the groove portion K is annealed using the MOCVD apparatus described above under the same conditions as in the previous embodiment, and then in a sequence substantially similar to that in the previous embodiment. Raw material gases were alternately supplied to stack semiconductor crystal layers 53 having a laser structure. However, when forming the buffer 7 layer, active layer, and contact layer, in process 1,
In addition to the gases shown in the previous examples, TMA was added to 5X I
It was introduced at QmO1/cycle.

After forming the semiconductor crystal layer 53 that will become a laser, as shown in FIG.
As shown in d), Ga formed for the purpose of molding using an ammonia and hydrogen peroxide mixed solution that does not remove A I GaAs but selectively removes Ga A, a.
The As crystal layer 52 was removed, and finally, electrodes (not shown) were formed to complete the semiconductor laser.

In this example, as in the previous example, a laser oscillation test was conducted. All lasers oscillated with direct current, and the threshold current was distributed from 25 mA to 35 mA. Furthermore, regarding the laser characteristics, there was a tendency that the threshold current of the laser whose end facet was close to the (110) plane was low.

In the above embodiments, the mold of the laser end face structure was formed using silicon oxide, silicon nitride, or GaAs crystal layer on the substrate, but the present invention is not limited to these, and other insulating materials may be used. It is also possible to form a mold for the laser end face structure using a semiconductor, a semiconductor, or a metal.

Further, in the above embodiments, after forming the semiconductor crystal layer that becomes the semiconductor laser device, the member used to form the mold of the laser end face structure was removed, but this is not essential to the present invention. .

That is, some or all of the members are left without being removed,
It may also be used for purposes such as protecting the laser end face or transmitting laser emitted light.

Next, an embodiment of the second invention will be described. In the first invention, a flat semiconductor film is formed using a Sin film as a wall surface, but in the second invention, a semiconductor film is selectively formed depending on the underlying material. This will be explained below with reference to FIG. First, as shown in FIG. 4(a), 8i0. n-type Ga A with embedded film 61
An s-substrate 60 is prepared.

The surface of this n-type GaAs substrate 60 is flat.

Next, raw material gases are alternately supplied to the surface of this n-type GaAs substrate 60 in the same manner as in the first invention, and a semiconductor crystal layer 62 having a laser structure as shown in FIG. 4(b) is laminated.

The method for forming the semiconductor crystal layer 62 may be performed in the same manner as the method for forming the semiconductor crystal layer 13 shown in FIG.

In this way, group I and
A semiconductor film can be selectively and evenly formed by vapor phase growth by alternately supplying raw material gases of the group.

In the embodiments described above, K r F excimer laser light was irradiated when forming the semiconductor crystal layer in order to increase the growth rate, but this is not essential to the present invention. It has been experimentally confirmed that the growth rate increases when irradiated with light of other wavelengths such as an argon ion laser, and light of other wavelengths may also be irradiated. Furthermore, since the film thickness of a monoatomic layer can be controlled by alternately supplying raw materials without irradiating light, a semiconductor crystal layer may be formed without irradiating light.

In addition, in the examples, triethylgallium was used as the raw material gas for the Ga element, but it has been confirmed that monoatomic layer thickness control can also be achieved using triethylgallium or triisobutylgallium. You may also use

In addition, in the embodiment, a method for manufacturing a GaAIAs double hetero semiconductor laser has been described, but the present invention is not limited to this. It has been confirmed that in the growth of InkSInAs, it is possible to control the thickness of a monoatomic layer by a vapor phase growth method in which raw materials are alternately supplied. Therefore, the present invention can be directly applied to the manufacture of semiconductor devices made of other mixed crystal materials such as InPs InAs, InGaAIP, InGaAsP, etc.

In addition, various modifications can be made without departing from the gist of the present invention.

〔Effect of the invention〕

As detailed above, according to the present invention, by using a vapor phase growth method in which raw material gases are alternately supplied, the properties are comparable to those produced using a cleavage process without using a cleavage process. We were able to manufacture a semiconductor laser device. Since no cleavage process is used, automation of manufacturing is possible.

Furthermore, since the device can be tested on the wafer, there is no need to perform unnecessary steps on the non-μ device.

Therefore, by using the present invention, the manufacturing cost of semiconductor lasers can be reduced. Furthermore, since semiconductor lasers can be integrated on a wafer in any direction, restrictions on the design of optical integrated circuits are significantly reduced.

[Brief explanation of drawings]

1 and 3 are cross-sectional views showing the manufacturing process of a semiconductor laser embodying the first invention, and FIG. 2 is a schematic view showing an MOCVD apparatus used in the process of forming a semiconductor crystal layer. FIG. 4 is a sectional view showing an embodiment of the second invention. 11-GaAm substrate, 12... silicon oxide film, 3... semiconductor crystal layer laminated with laser structure, l...
Growth container, 4... Susceptor, 5.36... Gas introduction tube, 3... Wafer, 0... Excimer laser 1 1-. AlGaAs substrate, 2... GaAs crystal layer, 3. ...Semiconductor crystal layers with laminated laser structures. Agent Patent Attorney Noriyuki Ken Yudo Mitsuyuki Matsuyama Figure 5--3-Law Figure Kasumi

Claims (2)

[Claims] (1) When forming a semiconductor crystal layer in contact with the wall surface on a semiconductor substrate having a wall surface made of different materials on the surface, the semiconductor crystal layer is formed by vapor phase growth in which source gases are alternately supplied. A method for manufacturing a featured semiconductor device. (2) Manufacture of a semiconductor device characterized in that a semiconductor crystal layer is selectively formed on a semiconductor substrate in which films of different materials are selectively embedded on the surface thereof by vapor phase growth in which raw material gases are alternately supplied. Method.