JP2002110632A - Manufacturing methods of structual substrate and of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a structural substrate with proper planarity of the surface which comprises a ridge part, formed partially on the surface to project from the surface of the substrate, and to provide a manufacturing method of a semiconductor device using the structural substrate. SOLUTION: A GaAs-group substrate 10, after forming a ridge part 10a, is subjected to at least two of the following treatments in the order of treatment with an organic solvent, plasma treatment and surface reduction treatment. In the treatment with an organic solvent, for example, the substrate 10 is immersed in acetone, followed by rinsing with water and them drying. Ultrasonic cleaning may be added to the acetone treatment and the water rinsing. As the plasma treatment, the substrate is subjected to surface oxidation with an oxygen plasma and then to reduction treatment of immersing the substrate in 1 hydrogen 2 ammonium difluoride, as the surface reduction treatment. As a result, roughness of the substrate 10 can be alleviated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a structural substrate partially provided on a surface of a substrate with a ridge portion projecting from the surface, and a method of manufacturing a semiconductor device using the same.

[0002]

2. Description of the Related Art Group III-V compound semiconductors, that is,
Gallium arsenide (GaAs), aluminum arsenide (AlA)
s), semiconductor lasers using indium arsenide (InAs), indium phosphide (InP), gallium phosphide (GaP), gallium antimonide (GaSb), etc., have an oscillation wavelength at room temperature ranging from red to infrared. Therefore, application to a light source of a high-density optical disk, an optical communication device, or a device such as a laser pointer is expected.

In application to these devices, it is desired to further reduce the threshold current.
SDH (Separate Double H)
(Etherostructure) structure has been proposed. For example, when a semiconductor layer is grown on a stepped structure substrate such as a ridge substrate, the layers are shifted just like a fault, and the current blocking layers are formed on both sides of the active layer on the step. You. In this way, a refractive index waveguide structure having an internal current confinement mechanism, that is, an SDH structure is obtained (Japanese Patent Laid-Open No. 61-183987, Electron).
ics Letters Vol. 32 No. 7 (1
996) pp. 664, IEEE J.C. Quantum
Electron. Vol. 28 (1992) p4). The SDH structure has an advantage that it can be formed by a single crystal growth, and since selective growth is used, a high-quality crystal can be grown even on a step or a slope portion of a structural substrate.

[0004]

A ridge substrate provided with a ridge portion such as a forward taper type on one surface is used as such a structure substrate. The forward tapered ridge portion refers to a ridge portion in which the inner angle between the bottom surface and the side surface is an acute angle and the cross-sectional shape is trapezoidal. Heretofore, a flat base surface and a protruding ridge portion have been formed on a substrate by etching the surface using, for example, a sulfuric acid-based etchant. However, in a sulfuric acid-based etchant, it is difficult to control the etching because the etching rate is high and the etchant must be prepared with a high precision mixing ratio. The ridge portion is formed by photolithography technology, CVD (Chemical).
Vapor Deposition (chemical vapor deposition)
Method, RIE (ReactiveIon Etchin)
g; reactive ion etching) and wet etching. As a result, the surface of the completed structural substrate was roughened, that is, surface contamination due to deposits, oxide films and the like, surface irregularities, and the like occurred.

[0005] In the semiconductor layer grown on such a structural substrate, abnormal growth occurs due to nuclei attached to the side surfaces of the ridge portion, and the flatness and homogeneity of the top surface and the bottom surface of the ridge portion. Or decreased. This itself is a factor that destabilizes the laser characteristics such as the threshold current and the oscillation wavelength, but this time, it was found that this would hinder the mask alignment in the subsequent processes,
Since the yield of the product is affected, the surface roughness of the structural substrate has become an issue to be further solved.

The present invention has been made in view of the above problems, and an object of the present invention is to manufacture a structural substrate having a ridge portion protruding partially from the surface of the substrate with good surface flatness. And a method for manufacturing a semiconductor device using the same.

[0007]

[Means for Solving the Problems]

A method of manufacturing a structural substrate according to the present invention comprises a first step of manufacturing a structural substrate by partially forming a ridge portion projecting from the surface of the substrate, and performing a surface treatment on the structural substrate. Second to improve the surface flatness
Wherein the second step is a step of treating the structural substrate with an organic solvent, a step of irradiating the surface of the structural substrate with plasma, and a step of reducing the surface of the structural substrate with a reducing agent. Are performed in this order.

According to the method of manufacturing a semiconductor device of the present invention, a first step of manufacturing a structural substrate by partially forming a ridge portion protruding from the surface of the substrate, and applying a surface treatment to the structural substrate. And a second step of improving the flatness of the surface by the second step.
Is a step of treating the structural substrate with an organic solvent,
At least two of the step of irradiating the surface of the structural substrate with plasma and the step of treating the surface of the structural substrate with a reducing agent are performed in this order.

In the method for manufacturing a structural substrate or the method for manufacturing a semiconductor device according to the present invention, the surface roughness of the structural substrate is improved and the flatness is improved.

[0011]

Embodiments of the present invention will be described below in detail with reference to the drawings.

[First Embodiment] A method of manufacturing a structural substrate according to a first embodiment of the present invention includes a step of forming a ridge portion and a step of performing a surface treatment thereafter. Hereinafter, a method of manufacturing a structural substrate will be described according to this order.

FIG. 1 shows a step of forming a ridge portion. First, as shown in FIG.
A substrate 10 made of a group III compound semiconductor, for example, GaAs doped with Zn as a p-type impurity and having a thickness of 350 μm with the (100) plane as the main surface (the thickness in the direction perpendicular to the main surface) is prepared. .

As the substrate 10, the following materials can be used. For example, aluminum arsenide (A
lAs), indium arsenide (InAs), indium phosphide (InP), gallium phosphide (GaP), and gallium antimonide (GaSb), or a mixture of at least one of these and GaAs. Akira,
And GaAs, AlAs, InAs, InP, Ga
A mixed crystal containing at least one of P and GaSb is used. All of these can be used with or without the addition of impurities.

Next, a mask pattern 11 is formed on the main surface of the substrate 10 so as to correspond to the formation region of the ridge 10a (see FIG. 1C). The formation of the mask pattern 11 is performed, for example, as follows. CVD (Chem
A silicon oxide (SiO ₂ ) film having a thickness of 150 nm and a silicon nitride (SiN _x ) film having a thickness of 10 nm are stacked on the (100) surface of the substrate 10 by an evaporation method such as an electrical vapor deposition (chemical vapor deposition) method. The formed multilayer inorganic material film is formed. On this inorganic material film, for example, a substrate 1 is formed by resist formation and photolithography.
A stripe-shaped mask extending in the <110> direction of 0 is formed, and the stacked film is selectively removed by RIE or etching with a soluble solution such as hydrogen fluoride (HF). After that, the resist film (not shown) is removed.

The width of the mask pattern 11 (width in the direction perpendicular to the extension direction) is determined in consideration of the fact that the width of the ridge portion 10a becomes smaller than the width of the mask pattern 11 due to side etching in an etching step described later. hand,
A predetermined value determined according to the width of the ridge portion 10a (for example, 10 μm when the width of the upper surface of the ridge portion 10a is 4 μm)
m). The interval between stripes is, for example, 100
μm.

The mask pattern 11 only needs to be able to withstand the subsequent etching, and may be formed of, for example, a single-layer film of silicon oxide or silicon nitride.

Next, as shown in FIG.
The first wet etching using a first etchant having no selectivity to the constituent elements of the substrate 10 is performed to the vicinity of the desired ridge shape with respect to 0. This first wet etching is an isotropic etching, and is performed so as not to have dependence on the plane orientation of a crystal including at least a {111} B crystal plane (hereinafter, referred to as a {111} B plane). This ends before the side surface of the ridge portion is etched until the {111} B surface becomes stable. As the first etchant, for example, sulfuric acid (H ₂ SO ₄ ), hydrogen peroxide solution (H ₂ O ₂ ), and water (H ₂ O) are mixed with sulfuric acid: hydrogen peroxide solution: water = 30: 10: 500. A mixed solution mixed at a volume ratio of is used.

Here, the mask pattern 11 of the substrate 10
Etching progresses from the portion not covered by <11
Side etching also proceeds in a direction perpendicular to the 0> direction. However, since the mask pattern 11 is formed of an inorganic material film to enhance the adhesion to the substrate 10, the progress of side etching is prevented at these interfaces. Accordingly, a drum-shaped ridge portion 10b is formed as a whole.

Next, as shown in FIG.
Among the constituent elements of 0, an element that can be a cation (for example,
In the case of GaAs, a second wett for causing a {111} B plane, which is an amorphous growth plane, to appear on the side surface of the ridge portion 10a with respect to the substrate 10 using a second etchant for selectively etching Ga). Perform etching. The second wet etching is a selective etching that is selectively performed on the substrate 10 with respect to a plane orientation including at least the {111} B plane. Here, the non-crystal growth surface refers to a surface where the crystal growth rate is extremely low and the crystal does not substantially grow.

As the second etchant, for example, an aqueous solution of citric acid in which citric acid and water are mixed at a volume ratio of 1: 1 and an aqueous solution of hydrogen peroxide, an aqueous solution of citric acid: aqueous hydrogen peroxide = 450: A mixed solution mixed at a volume ratio of 150 is used. In addition to the citric acid-based etchant, any of the constituent elements of the substrate 10 that forms a complex with an element that can be a cation can be used. Examples of such an etchant include carboxylic acids such as tartaric acid, acetic acid, oxalic acid, formic acid, succinic acid, and malic acid.

In the second wet etching, when the {111} B surface appears on the side surface of the ridge portion 10a, the etching is automatically stopped, and the side etch does not proceed any more immediately below the mask pattern 11. Further, the etching process is stopped when a predetermined etching depth is reached. At this time, the exposed surface of the substrate 10 becomes a base surface, and the height of the ridge portion 10a is defined by the position of the base surface. Thereby, for example, the side surface is constituted by the {111} B surface, and the upper surface has a width of 4 μm and a height of 3.5 to 4.0 μm.
The ridge portion 10a of the forward taper type extending in the <110> direction is formed. Incidentally, the first etchant and the second etchant have an effect of setting the side surface of the ridge portion 10a to a specific crystal plane only when they are used in the order described above, and the effect cannot be obtained by using only one of them. It is. Therefore, in this embodiment, two different types of wet etching are performed in combination to form the ridge 10a.
Are formed with high precision.

Next, as shown in FIG.
Dry etching using a solution such as a soluble chemical, or wet etching using a solution such as a soluble chemical.
Remove one. Thereby, a forward tapered ridge portion 10a having a stripe shape and a trapezoidal cross section is formed on the substrate 10.

At this time, the substrate 10 has particulate surface contamination due to the remaining mask pattern 11 and the like, and undulating undulations on the base surface and the upper surface of the ridge portion 10a. Conventionally, the substrate 10 is used in the manufacture of a semiconductor device in this state or after being subjected to organic cleaning, and the device characteristics are deteriorated as described above.

Therefore, in the present embodiment, the substrate 10
Is subjected to surface treatment. FIG. 2 is a sequence (flow chart) showing the procedure of the surface treatment. Next, the surface treatment of the substrate 10 will be described with reference to FIG.

First, an organic cleaning is performed (step 11).
This involves immersing the substrate 10 in, for example, acetone. Other solvents include methanol, ethanol,
Any one of isopropyl alcohol (IPA)
Species or a mixture of two or more can be used. The immersion conditions at this time may be determined appropriately.

At this time, when ultrasonic waves are applied to the solvent,
The detachment of the deposit proceeds, and the substrate can be more effectively cleaned (step 12). As a standard for ultrasonic cleaning, for example, the frequency may be a single frequency or a superimposed frequency in the range of about 28 to 100 kHz, the output may be 100 W, and the cleaning time may be about 5 to 10 minutes.

Next, the substrate 10 is pulled out of the organic solvent and washed with water (step 13). Washing, for example,
This is performed as running water washing with ultrapure water for about 5 minutes. As a result, the organic cleaning is stopped, and the organic solvent components and surface products are removed. If ultrasonic cleaning is also combined at this time, it is possible to prevent the adhered substances and the like once removed from adhering to the substrate 10 again, and to perform the substrate cleaning more effectively (step 14). The conditions of the ultrasonic cleaning are, for example, an output of 100 W and a frequency of 28.
Single frequency or superimposed frequency in the range of about 100 kHz,
The cleaning time is 5 minutes.

Next, the substrate 10 is dried (step 1).
5). Drying is performed by, for example, spin drying, infrared drying, hot air drying, natural drying, or the like. Among these, in the spin dry method, for example, the rotation speed is set to 900 rpm for 60 to 90 seconds. Here, the steps of organic washing, water washing and drying are collectively referred to as “organic solvent treatment”.

Next, plasma processing is performed on the substrate 10 (step 16). This can be performed in the same manner as, for example, the plasma etching. For example, when the surface of the substrate 10 is ashed using
50 ° C., oxygen gas flow rate 400 sccm, back pressure 80 Pa,
The output can be 350 W and the processing time can be 5 minutes. As a result, organic substances and the like attached to the surface of the substrate 10 are removed, and the substrate 10 is uniformly oxidized. In addition, as a plasma gas used for the treatment, any one of hydrogen, nitrogen, and a rare gas element can be given. In addition to the oxidation (ashing), the treatment is performed as plasma etching to remove deposits such as organic substances. It may be removed. Note that the surface state of the substrate 10 is made uniform by the plasma treatment regardless of whether it is oxidized.

Further, the substrate 10 is subjected to a surface reduction treatment (step 17). This is performed by immersing the substrate 10 in a reducing agent. For example, it is carried out by using a mixture of 18% ammonium difluoride and 72% water as a reducing agent and immersing for 5 to 20 minutes. As the reducing agent, other solvents such as hydrogen fluoride (HF), a solvent containing hydrogen (H) and fluorine (F), or an organic alkali solvent can be used. The oxide film generated by the treatment or the like is uniformly removed, and other residues are removed.

As described above, by performing the organic solvent treatment, the plasma treatment, and the surface reduction treatment in this order,
The surface roughness of the substrate 10 shown in (D) is improved. The manufactured substrate 10 is used as a substrate in a semiconductor device such as a semiconductor laser.

It is not always necessary to perform all of these processing steps, and it is sufficient that at least two of these processing steps are performed. The present inventors have previously tried only the surface reduction treatment on the surface of such a structural substrate, but this did not sufficiently remove the deposits and did not improve the undulation of the surface (FIG. 10). reference). Therefore, it is difficult to improve the surface roughness of the structural substrate by removing the deposits and the oxide film covering the surface by only one chemical cleaning, and a synergistic effect of at least two of the above processes is required. It is.

In this case, the order of processing must be maintained. For example, when plasma treatment is performed before organic solvent treatment, it is expected that deposits such as organic substances react with plasma to form a polymer. Such a polymer is generally not easily removed by washing with an organic solvent.
The surface state of the substrate 10 is made uniform by the plasma processing regardless of whether it is oxidized, and it is more effective to perform the surface reduction processing thereafter. If the surface is oxidized, a reduction treatment should be performed at the end to remove the oxide film.

As described above, according to the present embodiment, at least two of the organic solvent treatment, the plasma treatment, and the surface reduction treatment are performed on the substrate 10 on which the ridge portion 10a is formed.
Since the three steps are performed in this order, so-called surface contamination due to deposits such as organic substances can be removed, and at the same time, unevenness of the surface can be eliminated. Therefore, the surface roughness of the substrate 10 is reduced and planarized by a simple method with good reproducibility.

[Second Embodiment] The present embodiment relates to a method of manufacturing a semiconductor device using the method of manufacturing a structural substrate according to the first embodiment. Here, SD
A description will be given using a semiconductor laser having an H structure as an example. The SDH structure refers to a refractive index guided structure in which a current confinement mechanism is provided inside by a discontinuous semiconductor layer formed using a structural substrate such as a substrate having a ridge portion. In the following description, the same parts as those in the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted.

3 to 5 show a method of manufacturing a semiconductor laser according to the present embodiment for each process. First, the substrate 10 is manufactured in the same manner as in the first embodiment.

Here, when forming the ridge portion 10a, it is preferable to adjust the height so as to be, for example, 2.0 μm or more. This is because the height of the ridge portion 10a needs to be 2.0 μm or more in order to manufacture a semiconductor laser having the SDH structure. Further, it is preferable to adjust the width of the upper surface of the ridge 10a to be, for example, 10 μm or less. If the width of the ridge portion 10a is 10 μm or less, the width of the active layer laminated thereon can be about 3.0 μm, and a lower threshold of the laser can be achieved.

Next, as shown in FIG.
P-type zinc was added as a buffer layer 31, p-type impurities having a thickness of 0.6μm to zinc as type impurity is a p-type GaAs that has been added _Al s _{Ga 1-s} As (where 0 <
s <1) 500 nm thick first conductivity type cladding layer 32 of mixed crystal, p-type A doped with zinc as a p-type impurity
l _t Ga _1-t As (where, t <s) optical guide layer 33 with a thickness of 35nm made of mixed crystal, and _Al u _{Ga 1-u} A
7 nm thick active layer 3 of s (where u <t) mixed crystal
4 are sequentially grown on the substrate 10. Subsequently, for example, n-type Al _t G to which silicon is added as an n-type impurity
Light guide layer 3 having a thickness of 35 nm and made of a _1-t As mixed crystal
5, and n-type A doped with silicon as an n-type impurity
l _s Ga _1-s consisting As mixed crystal second conductivity type cladding layer 36 are sequentially grown the lower portion 36a (see FIG. 8). The lower layer portion 36a is grown until its two side surfaces intersect. The thickness of the lower layer portion 36a is, for example, 500 nm. Each of these layers is, for example, a continuous MOCV
D, that is, the source gas supplied for each layer is switched for growth.

As a result, the lower layer 3
Each layer up to 6a is formed on the upper surface of the ridge portion 10a and on both sides thereof by being divided by the ridge portion 10a. Ridge part 1
In addition to the {111} B plane, which is a non-crystal growth plane, the side surface of Oa has a reduced surface roughness because it is formed by the method of the first embodiment. Abnormal growth of the semiconductor layer is further suppressed.

Each of the layers from the buffer layer 31 to the lower layer portion 36a formed on the upper surface of the ridge portion 10a has the same {111} B plane as the side surface of the ridge portion 10a at the end thereof, and as if the ridge portion 10a had the same surface. Grows as if the sides are extended. Also on this upper surface, since it is formed by the method of the first embodiment, unevenness of the surface is reduced, and the semiconductor layers are stacked flat.

Next, as shown in FIG. 4, for example, p-type Al _s Ga _{1 -s} As to which zinc is added as a p-type impurity
A current blocking layer 37 made of a mixed crystal is grown by adjusting the thickness so as to cover the side surface of the active layer 34 provided on the upper surface of the ridge portion 10a. Here, since the ridge portion 10a has a uniform height and a substantially flat side surface, the shape of each layer grown on the upper surface follows the shape. Therefore, the current blocking layer 37 is formed to cover the side surface of the active layer 34 with high positional accuracy. As a result, both ends of the active layer 34 are closed, and current confinement and lateral light confinement are performed. Thus, an SDH structure is formed.

Next, as shown in FIG. 5, on the current blocking layer 37 and the lower portion 36a, for example, made of n-type _Al s _{Ga 1-s} As mixed crystal of silicon is added as n-type impurity 500 nm thick second conductivity type cladding layer 36
Is grown. At this time, the upper layer portion 36b
Grows over the entire surface of the substrate 10 when the growth proceeds to a thickness that covers the lower layer portion 36a. Next, on the upper layer portion 36b, for example, a thickness 6000 made of n-type GaAs doped with silicon at a high concentration as an n-type impurity is used.
A nm cap layer 38 is grown.

Thereafter, on the cap layer 38, for example, an alloy of gold (Au) and germanium (Ge), nickel (Ni) and gold are sequentially deposited to form an n-side electrode 39. Further, for example, nickel, platinum (Pt) and gold are sequentially deposited on the back surface of the substrate 10 to form a p-side electrode 40.
To form Thus, a semiconductor laser having the SDH structure is completed.

The semiconductor laser manufactured as described above operates as follows.

In this semiconductor laser, the n-side electrode 39 is
When a predetermined voltage is applied between the side electrode 40 and the side electrode 40, a current is injected into the active layer 34 formed on the upper surface of the ridge portion 14a, and light emission occurs due to electron-hole recombination. here,
By performing the above-described cleaning process, the surface of the substrate 10 becomes a flat surface with very little attached matter. Therefore, partial variation and abnormal growth are suppressed in the formation position of each semiconductor layer grown on the structure substrate, and both side surfaces of the active layer 34 formed on the upper surface of the ridge portion 14a are connected to the current block layer 37. Accurately covered. Therefore, a phenomenon caused by shape instability such as a reactive current to the active layer 34 is prevented, and various characteristics such as a threshold current, an operating voltage, and an oscillation wavelength are further stabilized.

In the present embodiment, the surface of the substrate 10 provided with the forward tapered ridge portion 10a in which the so-called surface contamination due to the deposits such as organic substances has been removed and the unevenness of the surface is flattened.
Since the DH structure is constructed, it is possible to reduce abnormal growth and variation in the formation position on the side surface of the ridge portion 10a of each semiconductor layer. Therefore, this substrate 1
It is easy to manufacture a semiconductor laser using 0, thereby improving the productivity and reducing the variation in the characteristics of the manufactured device, thereby improving the yield. As a result, when this semiconductor laser is applied to a device such as a light source of an optical integrated circuit, an optical communication or an optical recording medium, the degree of freedom of application is increased, and the speed of the device is reduced, the weight is reduced, and the area is reduced. And power consumption can be reduced. Further, application to a consumer or portable device can be easily performed.

[0048]

EXAMPLES Further, specific examples of the present invention will be described.

(Examples 1 to 3) A GaAs substrate on which a ridge was formed in the same manner as in the embodiment was prepared, and the following surface treatment was performed on the GaAs substrate in the following manner.

Organic solvent treatment; output 100 W, frequency 1
The substrate is immersed in an acetone solution to which 00 kHz ultrasonic wave has been applied for 5 minutes, and then washed and dried in the same manner as in the embodiment. Plasma processing: plasma processing is performed for 5 minutes at a substrate temperature of 150 ° C., an oxygen gas flow rate of 400 sccm, a back pressure of 0.6 Torr, and an RF output of 350 W. Surface reduction treatment: The substrate is immersed in Trico Chemical's Semicoclean, which is an organic alkaline solvent, for 20 minutes and then dried.

In Example 1, an organic solvent treatment, a plasma treatment, and a surface reduction treatment were performed in this order. In Example 2, a surface reduction treatment was performed after the organic solvent treatment.
In Example 3, a surface reduction treatment was performed after the plasma treatment.

Comparative Example A GaAs substrate having a ridge formed thereon was prepared in the same manner as in the example, and only the surface reduction treatment was performed.

An electron microscope observation was performed on these Examples 1 to 3 and Comparative Example. 6 to 9 are photomicrographs of each (FIGS. 6 to 8; magnification 100 times, FIG. 9; magnification 200 times). In the comparative example, a large number of granular deposits remain at the boundary between the upper surface of the ridge and the bottom surface and the side surface, and further, undulating undulations can be clearly seen on the upper surface and the bottom surface of the ridge portion. On the other hand, in Examples 1 to 3, such deposits are sharply reduced, and it can be seen that the undulations on the upper surface and the base surface of the ridge portion have disappeared and are flattened. Also, it can be seen that the surface roughness is lower in the order of the numbers among the examples.

Therefore, one of the above processes
In one treatment, the effect of improving the roughness of the substrate surface was hardly observed, and it was found that a structural substrate having a flat surface can be obtained by combining two or more of these three treatments in this order. In addition, it is most effective to perform all the processes of
Was found to be effective in this order.

Although the present invention has been described with reference to the embodiment and examples, the present invention is not limited to the above-described embodiments and examples, and can be variously modified. For example, in the above embodiments and examples, the side surface
Although the method of manufacturing the substrate 10 having the forward tapered ridge portion 10a formed by the 1｝ B plane has been described, other methods may be used as the ridge portion 10a. Further, for example, the present invention can be applied to other structural substrates such as a so-called reverse tapered substrate.

In the second embodiment, the substrate 1
Although a semiconductor laser was mentioned as a semiconductor device using 0,
The present invention can be applied to other semiconductor device manufacturing methods. For example, a recessed structure FET (Fi
eld Effect Transistor (Field Effect Transistor).

[0057]

As described above, according to the method for manufacturing a structural substrate according to any one of claims 1 to 8, a ridge portion projecting from this surface is partially formed on the surface of the substrate. And a second step of performing a surface treatment on the structure substrate to improve the flatness of the surface. And the step of irradiating the surface of the structural substrate with plasma, and the step of treating the surface of the structural substrate with a reducing agent are performed in this order. Roughness is improved, and a structural substrate composed of a flat surface can be obtained. Therefore, it is possible to easily manufacture a semiconductor device using the semiconductor device and improve the productivity.

In particular, according to the method for manufacturing a structural substrate according to the third aspect, the step of treating the structural substrate with an organic solvent includes a step of immersing the structural substrate in the organic solvent and then washing the structural substrate with water. In addition, in at least one of the step of immersing the structure substrate in an organic solvent, or the step of washing the structure substrate with water, ultrasonic vibration was added to the organic solvent or water, so that The surface roughness can be effectively improved.

According to the method of manufacturing a semiconductor device according to any one of claims 9 to 16, since the method of manufacturing a structural substrate of the present invention is used, a ridge portion of each semiconductor layer is provided. It is possible to reduce the abnormal growth and the variation of the formation position on the side surface. Therefore, a desired semiconductor device can be easily manufactured, productivity can be improved, and variation in characteristics of the manufactured device can be reduced to improve yield.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a step of manufacturing a ridge portion of a structural substrate according to a first embodiment of the present invention.

FIG. 2 is a flowchart illustrating a procedure of a surface treatment performed after the step of FIG. 1;

FIG. 3 is a sectional view illustrating a manufacturing process of a semiconductor laser according to a second embodiment of the present invention.

FIG. 4 is a sectional view illustrating a step following FIG. 4;

FIG. 5 is a sectional view illustrating a step following the step of FIG. 5;

FIG. 6 is a micrograph of a structural substrate of Example 1 of the present invention.

FIG. 7 is a micrograph of a structural substrate of Example 2 of the present invention.

FIG. 8 is a micrograph of a structural substrate of Example 3 of the present invention.

FIG. 9 is a micrograph of a structural substrate of a comparative example of the present invention.

[Explanation of symbols]

 Reference numeral 10: substrate, 10a: ridge portion, 11: mask pattern

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) H01S 5/323 H01L 21/302 NF term (reference) 5F004 AA14 BD01 DA00 DA24 DA25 DA26 DB23 EA10 EB08 FA07 5F043 AA03 AA04 AA05 BB07 FF05 GG10 5F073 AA14 BA01 BA04 CA05 CB02 DA22 DA25 EA23

Claims (16)

[Claims] 1. A first step of manufacturing a structural substrate by partially forming a ridge protruding from the surface on a surface of the substrate, and improving the flatness of the surface by performing a surface treatment on the structural substrate. A method of manufacturing a structural substrate, comprising: a step of treating the structural substrate with an organic solvent; a step of irradiating plasma to a surface of the structural substrate; A method of manufacturing a structural substrate, wherein at least two of the steps of treating the surface of the structural substrate with a reducing agent are performed in this order. 2. The structure substrate according to claim 1, wherein the step of treating the structure substrate with an organic solvent includes a step of immersing the structure substrate in an organic solvent and then washing the structure substrate with water. Manufacturing method. 3. An ultrasonic vibration is applied to the organic solvent or water in at least one of a step of immersing the structural substrate in an organic solvent and a step of rinsing the structural substrate with water. The method for manufacturing a structural substrate according to claim 2. 4. The method according to claim 1, wherein the organic solvent is at least one of acetone, methanol, ethanol and isopropyl alcohol, or a mixture of two or more thereof. 5. The method according to claim 1, wherein the plasma contains any one of hydrogen, nitrogen, oxygen, and a rare gas element. 6. The method according to claim 1, wherein the surface reducing agent is one of an organic alkaline solvent, and a solvent containing hydrogen fluoride (HF) or hydrogen (H) and fluorine (F). 3. The method for manufacturing a structural substrate according to 1. 7. The method according to claim 1, wherein the ridge portion is a forward tapered type having a trapezoidal cross section. 8. The material of the structural substrate may be III-V
2. The method according to claim 1, wherein a group III compound semiconductor is used. 9. A first step of fabricating a structural substrate by partially forming a ridge protruding from the surface on the surface of the substrate, and improving the flatness of the surface by performing a surface treatment on the structural substrate. A method of manufacturing a semiconductor device, comprising: a step of treating the structural substrate with an organic solvent; a step of irradiating a surface of the structural substrate with plasma; A method of manufacturing a semiconductor device, wherein at least two of the steps of treating the surface of a structural substrate with a reducing agent are performed in this order. 10. The semiconductor device according to claim 9, wherein the step of treating the structural substrate with an organic solvent includes a step of immersing the structural substrate in an organic solvent and then washing the structural substrate with water. Manufacturing method. 11. An ultrasonic vibration is applied to the organic solvent or water in at least one of a step of immersing the structural substrate in an organic solvent and a step of washing the structural substrate with water. Claim 10
The manufacturing method of the semiconductor device described in the above. 12. The method according to claim 9, wherein the organic solvent is any one of acetone, methanol, ethanol and isopropyl alcohol or a mixture of two or more thereof. 13. The method according to claim 9, wherein the plasma contains any one of hydrogen, nitrogen, oxygen, and a rare gas element. 14. The method according to claim 9, wherein the surface reducing agent is an organic alkaline solvent, or a solvent containing hydrogen fluoride (HF) or hydrogen (H) and fluorine (F). 13. The method for manufacturing a semiconductor device according to item 5. 15. The method of manufacturing a semiconductor device according to claim 9, wherein said ridge portion is a forward tapered type having a trapezoidal cross section. 16. The material of the structural substrate may be III-
The method for manufacturing a semiconductor device according to claim 9, wherein a group V compound semiconductor is used.