JPH11288888A - Crystal growth method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a crystal growth method in which a spontaneous oxide film is not formed on the surface of a semiconductor layer and on the surface of a semiconductor substrate by a method, wherein a dielectric film is formed on the semiconductor substrate, a selective growth operation is performed by making use of the dielectric film as a mask, the dielectric film is removed in a growth chamber and a second semiconductor layer is formed from its upper part so as to be embedded and grown. SOLUTION: A dielectric film 2 is formed on a semiconductor substrate 1 at a film formation speed of 1 nm or lower per minute. An opening part 5 is formed in the dielectric film 2 by the use of a photolithographic technique. A first semiconductor layer 3 is grown on the semiconductor substrate 1 by the use of a organometallic thermal-decomposition crystal growth apparatus. Then, the dielectric film 2 which becomes a mask for selective growth is removed, while hydrogen chloride gas is made to flow in the organometallic thermal-decomposition crystal growth apparatus. Lastly, the first semiconductor layer 3 is embedded into the semiconductor substrate 1 on which the first semiconductor layer 3 is formed, a second semiconductor layer 4 is formed without the use of a mask, and the second semiconductor layer 4 is grown so as to form a semiconductor layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and more particularly, to a crystal growth method using a metalorganic thermal decomposition vapor deposition method.

[0002]

[Prior art]

In the conventional crystal growth method, when a semiconductor layer is selectively grown at a desired position on a semiconductor substrate, a dielectric such as silicon oxide is formed on the semiconductor substrate, and a photolithography technique is applied thereto. An opening is provided by using the dielectric having the opening as a mask, and selectively grown only in the opening by using an organic metal thermal decomposition method or the like. It is taken out from the crystal growth apparatus, and the dielectric layer is removed by chemical etching.
In a general process, the semiconductor substrate processed in this manner is introduced again into a crystal growth apparatus, and the semiconductor layer formed by the selective growth is further buried by a second crystal growth to form a semiconductor layer structure. there were.

[0004]

However, in the case of such a crystal growth method, in order to remove the dielectric layer, the semiconductor substrate which has been selectively grown must be once taken out of the crystal growth apparatus into the atmosphere. At this time, a natural oxide film is formed on the surface of the semiconductor layer formed by the selective growth or on the surface of the semiconductor substrate from which the dielectric film has been removed. for that reason,
There has been a problem that defects or the like due to surface levels are formed at the interface.

As a method for growing a crystal or a method for manufacturing a semiconductor device, Japanese Patent Application Laid-Open No. 7-235722 discloses a method for manufacturing a semiconductor laser having a narrow stripe width in an active region with good reproducibility.

Japanese Patent Application Laid-Open No. 8-78386 discloses that
There is disclosed an etching method capable of etching a semiconductor layer with good controllability without using an etchant.

Further, the above publications disclose that a first-layer insulating film mask is removed to form a second-layer insulating mask.

However, JP-A-7-235722 and JP-A-8-78386 disclose that a first-layer insulating film mask is removed to form a second-layer insulating mask. However, it does not disclose removing the first-layer insulating film mask in the growth chamber. Also, of course, there is no disclosure of a specific technique for making it possible.

SUMMARY OF THE INVENTION The present invention has been made in view of the problems of the crystal growth method in the prior art described above, and a first object of the present invention is to selectively perform the selective growth using a dielectric film as a mask. The purpose is to prevent a natural oxide film from being formed on the surface of the formed semiconductor layer or the surface of the semiconductor substrate from which the dielectric film has been removed.

Another object of the present invention is to realize a crystal growth method in which no defects or the like due to surface states are formed at the interface.

[0011]

According to an aspect of the present invention, there is provided a method for growing a crystal of a semiconductor layer, comprising the steps of: providing a semiconductor substrate and / or a semiconductor uppermost layer formed on the semiconductor substrate; Forming a dielectric film formed at a film formation rate of 1 nanometer or less per minute on the upper surface of
Using the formed dielectric film as a mask to selectively grow crystals in a growth chamber using an organometallic thermal decomposition method or the like; and forming the formed dielectric film in the growth chamber after the crystal is selectively grown. And a step of removing as a basic step, and repeating the basic step a predetermined number of times.

Further, in at least one of the semiconductor layers formed by repetition of the basic steps, a crystal of the semiconductor layer is grown without using the mask. The above crystal growth method is also provided.

Further, alumina can be used as a material of the dielectric film in the crystal growth method. Further, silicon oxide can be used as a material of the dielectric film in the crystal growth method.

Further, as a method of forming the dielectric film in the crystal growth method, an electron beam evaporation method can be used. In the method of removing the dielectric film in the crystal growth method, a hydrogen chloride gas or a hydrogen fluoride gas may be used.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a crystal growth method according to the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a semiconductor manufacturing process to which a crystal growth method according to the present invention is applied.

First, an outline of a crystal growth method according to the present invention and a structure of a semiconductor formed by the method will be described. Semiconductor substrate 1
A dielectric film 2 formed at a deposition rate of 1 nanometer per minute or less is formed thereon, and selective growth is performed using the dielectric film 2 as a mask by using an organic metal thermal decomposition method. After the selective growth, the dielectric film 2 used as the mask is removed in a growth chamber, and a second semiconductor layer 4 formed by selective growth is formed thereon and buried.

Next, the details of the above steps will be described based on the above structure. As shown in the step of FIG. 1A, a dielectric film 2 is formed on a semiconductor substrate 1 at a deposition rate of 1 nm or less per minute, and a photolithography technique is used for the dielectric film 2. An opening 5 is provided. This semiconductor substrate 1 is introduced into an organic metal thermal decomposition crystal growth apparatus.

Next, the first semiconductor layer 3 is grown on the semiconductor substrate 1 by the organometallic thermal decomposition method using the above-mentioned organometallic thermal decomposition crystal growth apparatus. At this time, as shown in the step of FIG. 1B, the semiconductor layer does not grow on the dielectric film 2 and the first layer is formed only on the opening 5 where the semiconductor surface is exposed.
Semiconductor layer 3 is selectively grown.

Next, as shown in the step of FIG. 1C, the dielectric film 2 serving as the selective growth mask shown in the step of FIG. It is removed by flowing hydrogen chloride gas. Normally, the dielectric film cannot be removed by hydrogen chloride gas, but the dielectric film 2 formed by the above-described method can be removed by hydrogen chloride gas. For this reason, usually, it is necessary to take out once from the organometallic pyrolysis crystal apparatus, remove it with hydrogen fluoride or the like, and introduce it again into the organometallic pyrolysis crystal apparatus, but according to the crystal growth method according to the present invention, The step of once removing the sample to the outside can be omitted.

Finally, in the step shown in FIG. 1D, the first semiconductor layer 3 is buried on the semiconductor substrate 1 on which the first semiconductor layer 3 is formed, and the second semiconductor layer 4 is formed. Is formed without using a mask, and the second semiconductor layer 4 is grown to form a semiconductor layer.

The series of steps shown in FIGS. 1 (a) to 1 (d) are used as basic steps, and the basic steps are repeated a predetermined number of times to continuously bury each layer of the semiconductor having a multilayer structure. Can be done.

According to the crystal growth method of the present invention, since the formation rate of the dielectric film is set as described above, it is not necessary to take the sample out of the apparatus for removing the dielectric film. A natural oxide film is not formed on the surface of the substrate 1 or the first semiconductor layer 3, and the generation of defects due to surface levels caused by the formation of an oxide film at the interface with the second semiconductor layer 4 is suppressed. be able to.

FIG. 2 is a diagram showing a semiconductor manufacturing process to which the crystal growth method according to the present invention is applied. In the crystal growth method according to the present invention, a mask made of a dielectric film is used in the process of forming the second semiconductor layer as in the process of forming the first semiconductor layer.

First, in the step shown in the completed view in FIG. 2A, a first semiconductor layer 22 is grown on the entire upper surface of the semiconductor substrate 21 by an organic metal thermal decomposition method or the like. The steps so far are the same as the steps of the crystal growth method shown in FIGS.

Next, the dielectric film 23 is formed at a film formation rate of 1 nanometer or less per minute. Next, the dielectric film 23 and the first semiconductor layer 22 are formed by using a photolithography technique.
The excess dielectric film attached to the semiconductor substrate 21 is removed by chemical etching. The dielectric film 23 remaining after the etching is used as a mask when forming the second semiconductor layer.

Next, in the step shown in FIG.
The semiconductor substrate 21 is introduced into an organic metal thermal decomposition growth apparatus, and a second semiconductor layer 24 is formed on the semiconductor substrate 21 on which the structure including the first semiconductor layer 22 and the dielectric film 23 is formed.
Grow. At this time, the semiconductor layer does not grow on the dielectric film 23 due to the mask action, and therefore, the second semiconductor layer 24 grows selectively only on the semiconductor substrate 21.

Next, in the step shown in FIG. 2C, the dielectric film 23 is removed without taking the semiconductor substrate 21 out of the organometallic thermal decomposition growth apparatus, as in the above-described crystal growth method of the present invention. , And hydrogen chloride gas or the like.

Finally, after removing the dielectric film 23 as shown in the step of FIG. 2D, a third semiconductor layer 25 is grown, and the first semiconductor layer 22 and the second semiconductor layer 24 are grown. Is embedded, and finally a semiconductor structure as shown in the step of FIG. 2D is completed.

A series of steps shown in FIGS. 2 (a) to 2 (d) are set as basic steps, and the basic steps are repeated a predetermined number of times to continuously bury and grow each layer of the semiconductor having a multilayer structure. Can be done.

In the above description of the crystal growth method of the present invention, two typical cases of buried growth have been described. By setting
Irrespective of the embedded shape of the crystal, the mask of the dielectric film after the selective growth of the crystal is removed in an apparatus such as an organometallic thermal decomposition growth apparatus without removing the entire sample to the outside of the apparatus. It is possible to perform buried growth in which the subsequent crystal growth is performed continuously.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 3 is a diagram illustrating an example of a semiconductor manufacturing process to which the crystal growth method according to the first embodiment of the present invention is applied.

In the manufacturing process according to this embodiment, the GaAs ridge structure is selectively grown, and the ridge structure formed by the first selective growth is buried and grown in GaAs without taking the wafer out of the apparatus. Is shown.

First, in a step shown in FIG. 3A, a dielectric film 32 made of alumina formed on a GaAs (001) semiconductor substrate 31 made of Si-doped GaAs at a film formation rate of 1 nm or less per minute. After forming an opening in the dielectric film 32 by using a photolithography technique, the GaAs semiconductor substrate 31 is introduced into an organic metal thermal decomposition crystal growth apparatus.

Next, a first GaAs semiconductor growth layer 33 made of Mg-doped GaAs (impurity concentration 1 × 10 4) is formed on the semiconductor substrate 31 by using an organic metal thermal decomposition crystal growth apparatus.
¹⁷ cm ⁻³ ) at a growth temperature of 700 ° C. and a V / III ratio of 100
Under the above growth conditions, 1.5 μm selective growth is performed, and thereafter, the dielectric film 32 is selectively removed by flowing hydrogen chloride gas in an organic metal thermal decomposition crystal growth apparatus. Normally, the dielectric film cannot be removed by hydrogen chloride gas, but the dielectric film 32 formed by the method of the present invention can be removed by hydrogen chloride gas. For this reason, it is usually necessary to take out the sample once out of the organometallic thermal decomposition crystallizer, remove it with hydrogen fluoride or the like, and introduce it again into the organometallic thermal decomposition crystallizer. The step of taking out can be omitted.

Finally, in the step shown in the completed drawing in FIG. 3B, after the above-mentioned dielectric film is removed, the semiconductor substrate 1 on which the first semiconductor growth layer 33 is formed is doped with Si-doped Ga.
The second semiconductor growth layer 34 of As (impurity concentration 1 ×
10 ¹⁷ cm ⁻³ ) is grown on the entire surface, and the fabrication of the semiconductor buried structure is completed.

According to the crystal growth method shown in this embodiment, it is not necessary to take out the sample to the outside of the apparatus for removing the dielectric film, so that a natural oxide film is formed on the surface of the first semiconductor layer 33. It is possible to suppress the generation of defects due to surface levels at the time of forming an oxide film, which are not formed and are observed at the interface with the second semiconductor layer 34.

FIG. 4 is a view showing an example of a semiconductor manufacturing process to which the crystal growth method according to the second embodiment of the present invention is applied. In the crystal growth method according to the present embodiment, GaInAs
Wavelength 0.98 μm having a strained quantum well structure composed of
The selective growth of a semiconductor laser wafer in a band will be described as an example.

The semiconductor laser wafer of this embodiment is grown by an organic vapor deposition method. First, GaAs doped with Si
A buffer layer 42 of GaAs doped with Si (impurity concentration: 1 × 10 ¹⁸ cm) is formed on an s (001) substrate 41.
^-3 ) was grown 0.5 μm and then Si-doped Al
_A first cladding layer 43 (impurity concentration: 1 × 10 ¹⁷ cm ⁻³ ) made of _0.4 Ga _0.6 As is grown at 700 ° C. and V / III
Under a growth condition of a ratio of 100, the light emitting layer is grown at 2 μm, and then the light emitting layer is grown thereon.

FIG. 5 shows the layer structure of the light emitting layer 44. This light emitting layer 44 is formed on the first cladding layer 43 by Al _0.2 G
a _0.8 As First Light Guide Layer 5 of 40 nm Thickness
1. First barrier layer 5 made of GaAs and having a thickness of 20 nm
2. A first active layer 53 made of Ga _0.76 In _0.24 As and having a thickness of 4.5 nm, and a second active layer 53 made of GaAs and having a thickness of 20 nm.
Barrier layer 54, a second active layer 55 made of Ga _0.76 In _0.24 As and having a thickness of 4.5 nm, a third barrier layer 56 made of GaAs having a thickness of 20 nm, and a 40 nm thick layer made of Al _0.2 Ga _0.8 As. The second light guide layer 57 is formed by sequentially growing under a growth condition of a growth temperature of 680 ° C. and a group V / III ratio of 80.

Further, a second cladding layer 45 made of Mg-doped Al _0.4 Ga _0.6 As is formed on the light emitting layer 44.
(Impurity concentration 1 × 10 ¹⁸ cm ⁻³ ) is grown to 1.5 μm, and a cap layer 46 (impurity concentration 1 × 10 ¹⁹ cm ⁻³ ) made of Mg-doped GaAs is formed on the light emitting layer 4.
Under the same conditions as in No. 4, the first growth is performed by 0.1 μm and the first growth of the laser wafer is completed.

Next, the laser wafer is taken out of the growth apparatus, and a dielectric film is deposited on the entire surface of the cap layer 46 as shown in the step of FIG. Then, a dielectric film 47 made of striped alumina having a width of 5 μm, a ridge-shaped cap layer 46, and a second cladding layer 45 are formed in the [-110] direction.

Next, the GaAs (001) substrate 41 is introduced again into the organic metal thermal decomposition growth apparatus, and a second crystal growth is performed. First, on the second cladding layer 45, a first current blocking layer 48 (impurity concentration 1 × 10 ¹⁸ c) made of Si-doped Al _0.6 Ga _0.4 As and having a thickness of 0.8 μm.
m ^-3 ), and 0.8 μm thick Si-doped GaAs
Current blocking layer 49 (impurity concentration 1 × 1
0 ¹⁸ cm ^-3 ) is grown. At this time, the crystal does not grow on the dielectric film 47 but grows selectively only on the second cladding layer 45.

Further, the dielectric film 47 is removed by flowing hydrogen chloride gas without taking the sample out of the organometallic thermal decomposition growth apparatus. At this time, since the second current blocking layer 49 made of GaAs has resistance to hydrogen chloride gas, it is not etched. The dielectric layer 47 is eliminated, and the first GaAs cap layer 4 is formed.
Etching with hydrogen chloride gas is stopped when 6 is exposed. Finally, a 1 μm-thick Mg-doped Ga
As cap layer 410 made of As (impurity concentration 1 ×
10 ¹⁹ cm ⁻³ ) is grown, and the growth of the laser wafer is completed.

In the description of the first and second embodiments of the present invention, the gas used for removing the dielectric film is exemplified by hydrogen chloride gas, and the material exposed on the surface is: Each of the combinations has been described using GaAs as an example, but other combinations may be used as long as the combination is such that the dielectric film is etched but the material exposed on the surface is not etched.

[0045]

As described above, according to the present invention,
When a crystal is selectively grown using the dielectric film as a mask, a natural oxide film is formed on the surface of the semiconductor layer formed by the selective growth or on the surface of the semiconductor substrate from which the dielectric film has been removed. In addition, it is possible to realize a crystal growth method in which defects or the like due to surface states are not formed.

Further, the crystal growth method according to the present invention can be applied to all the burying growth steps of a method using a dielectric film mask when performing selective growth irrespective of the burying shape.

[Brief description of the drawings]

FIG. 1 is a diagram showing a semiconductor manufacturing process to which a first crystal growth method of the present invention is applied.

FIG. 2 is a view showing a semiconductor manufacturing process to which a second crystal growth method of the present invention is applied.

FIG. 3 is a diagram illustrating an example of a semiconductor manufacturing process to which the crystal growth method according to the first embodiment of the present invention is applied.

FIG. 4 is a diagram showing an example of a semiconductor manufacturing process to which a crystal growth method according to a second embodiment of the present invention is applied.

FIG. 5 is a diagram showing a layer structure of a light emitting layer of a semiconductor to which a crystal growth method according to a second embodiment is applied.

[Explanation of symbols]

 1, 21, 41 Semiconductor substrate 2, 23, 32, 47 Dielectric film 3, 22, 33 First semiconductor layer 4, 24, 34 Second semiconductor layer 5 Opening 25 Third semiconductor layer 42 Buffer layer 43 First cladding layer 44 Light emitting layer 45 Second cladding layer 46 First cap layer 48 First block layer 49 Second block layer 51 First light guide layer 52 First barrier layer 53 First activity Layer 54 Second barrier layer 55 Second active layer 56 Third barrier layer 57 Second light guide layer 410 Second cap layer

Claims (6)

[Claims] A step of forming a dielectric film formed at a film formation rate of 1 nanometer per minute or less on a plane upper portion of a semiconductor substrate and / or a semiconductor uppermost layer formed on the semiconductor substrate; A step of selectively growing crystals in a growth chamber using an organic metal thermal decomposition method or the like using the dielectric film as a mask; and removing the formed dielectric film in the growth chamber after the selective growth of the crystals. And a step of repeating the basic step a predetermined number of times as a basic step. 2. The semiconductor device according to claim 1, wherein at least one of the semiconductor layers formed by repeating the basic steps is grown without using the mask. The method for growing a crystal according to claim 1, wherein 3. The crystal growth method according to claim 1, wherein alumina is used as a material of said dielectric film. 4. The crystal growth method according to claim 1, wherein silicon oxide is used as a material of said dielectric film. 5. The crystal growth method according to claim 1, wherein an electron beam evaporation method is used as the method for forming the dielectric film. 6. The crystal growth method according to claim 1, wherein a hydrogen chloride gas or a hydrogen fluoride gas is used in the method of removing the dielectric film.