JPH09129930A - Manufacture of blue light emitting element using compound semiconductor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make such an etching gas that becomes the object of fluorocarbon gas control unnecessary by etching a second clad layer and an active layer composed of gallium nitride semiconductors with an etching gas containing boron trichloride and chlorine. SOLUTION: After a sapphire substrate 100 is set on a quartz plate 17, a vacuum chamber 11 is evacuated to a vacuum. Then boron trichloride BC3 and chlorine C2 are respectively introduced to the chamber 11 at rates of 50sccm and 5sccm through a first reaction gas introducing pipe 13 and a second reaction gas introducing pipe 13 and high-frequency electric power of 13.56MHz in frequency is supplied between first and second electrodes. As a result, the plasma of the reaction gases is generated in the chamber 11 and the laminated body of the gallium nitride semiconductors can be dry-etched. Therefore, a dry etching method which can etch a wide range of semiconductors, especially, GaN compound semiconductors without using such an etching gas that becomes the object of the fluorocarbon gas control can be realized.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to gallium nitride-based II
I-V group (GaN-based III-V compound semiconduct
or) It relates to a method for manufacturing a blue light emitting device using a compound semiconductor, and more particularly to a dry etching technique for a gallium nitride-based III-V group compound semiconductor.

[0002]

2. Description of the Related Art In recent years, GaN, In _x Ga _{1 -x} N, Ga
Gallium nitride-based compound semiconductors such as _x Al _1-x N have attracted attention as materials for blue light emitting diodes (LEDs) and blue laser diodes (LDs). By using this compound semiconductor, it has become possible to obtain an LED or LD that emits blue light, which has been difficult to obtain sufficiently high emission intensity.

As a blue light emitting device using a gallium nitride-based compound semiconductor, for example, there is one described in JP-A-5-63266. FIG. 16 shows the structure of such a conventional LED. That is, the blue light emitting element 2 includes the n-type GaN semiconductor layer 202 and the p-type Ga that are stacked on the sapphire substrate 100 with the buffer layer 201 interposed therebetween.
It consists of N semiconductor layer 203. Light can be emitted by injecting carriers into the depletion layer between the n-type GaN semiconductor layer 202 and the p-type GaN semiconductor layer 203. In order to manufacture such a blue light emitting device, first, a sapphire substrate 100 is prepared, and MO-CVD is performed thereon.
Each semiconductor layer 201 made of gallium nitride by using a method such as
202 and 203 are laminated. After that, the laminated substrate is taken out of the CVD reaction chamber, and the gallium nitride semiconductor laminated body is subjected to necessary etching. Finally, the laminated substrate is cut into appropriate sizes to separate individual chips.

The gallium nitride-based semiconductor is chemically very stable, does not dissolve in an acid such as hydrochloric acid, sulfuric acid, hydrofluoric acid or a mixed solution thereof, and wet etching is impossible at present. Therefore, dry etching must be used. As such dry etching, Japanese Patent Application Laid-Open No. HEI-1
-278025 or JP-A-1-278026. In these publications, carbon tetrachloride (CCl ₄ ) or carbon difluoride dichloride (CCl _{2) is used.}
Dry etching with F ₂ ) gas has been proposed.

[0005]

However, carbon difluoride dichloride (CCl ₂ F ₂ ) is subject to CFC gas regulation, and it is difficult to handle exhaust gas.
Special consideration needs to be taken. On the other hand, carbon tetrachloride (CC
The method using l ₄ ) does not have such a problem, but it is said that the etching rate is much slower and the productivity is not improved as compared with the method using carbon difluoride dichloride (CCl ₂ F ₂ ). There are other problems. Furthermore, since it is a liquid at room temperature, it is difficult to maintain a constant pressure and flow rate, which makes it difficult to handle.

Therefore, an object of the present invention is to provide a dry etching method for a gallium nitride-based compound semiconductor which is easy to operate and has a wide application range.

Another object of the present invention is to provide a manufacturing method capable of obtaining a high-quality gallium nitride-based blue light emitting device with a high manufacturing yield by using the dry etching method for a gallium nitride-based compound semiconductor. That is.

[0008]

In order to achieve the above object, the dry etching according to the present invention uses an etching gas containing boron trichloride (BCl ₃ ) and chlorine (Cl ₂ ).

The method for manufacturing a blue light emitting device according to the present invention further includes a first gallium nitride based semiconductor layer having a first conductivity type, a substantially intrinsic gallium nitride based semiconductor active layer, and A step of forming a laminated body made of a second gallium nitride based semiconductor layer having a second conductivity type opposite to the first conductivity type, and a predetermined process of forming the laminated body by an etching gas made of boron trichloride and chlorine. At least to the step of dry etching. By "substantially authentic" is meant that no impurities have been intentionally added.

According to the present invention having the above-described structure, dry etching applicable to a wide range of semiconductors can be realized without using an etching gas that is subject to CFC gas regulation.

Further, with the above-mentioned structure, a high quality blue light emitting diode or the like can be easily manufactured with a high yield.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings.

A method for etching a gallium nitride based semiconductor according to the present invention will be described with reference to FIG. FIG. 1 is a schematic view of a parallel plate type plasma etching apparatus capable of performing dry etching according to the present invention. The plasma etching apparatus 10 includes a vacuum chamber 11, a first reaction gas introduction pipe 12, a second reaction gas introduction pipe 13, an exhaust pipe 14, a first electrode 15, a second electrode 16 and a second electrode 16. It consists of a quartz plate 17 placed on top. The quartz plate 17 serves as an electrode cover for insulating the etching sample from the second electrode 16 and preventing metal contamination from the second electrode 16.
In FIG. 1, a sample for etching, that is, a sapphire substrate 100 having a layered body of gallium nitride based semiconductor formed on its surface is placed on a quartz plate 17, and then the vacuum chamber 1
The inside of 1 is evacuated to about 1 × 10 ^-2 Pa. And the first
50 of boron trichloride BCl ₃ from the reaction gas introducing pipe 12 of
Sccm from the second reaction gas introducing pipe 13 to chlorine Cl ₂
Is introduced at 5 sccm, and the first electrode 15 and the second electrode
13.56 MHz radio frequency (RF) power is supplied between the electrodes 16 of the. Then, plasma of the reaction gas is generated in the vacuum chamber 11, and dry etching of the stacked body of gallium nitride based semiconductors can be performed. During the dry etching, the reaction pressure is 1 Pa and the substrate temperature is kept at 5 ° C. The reaction pressure may be adjusted by a conductance adjustment valve such as a butterfly valve connected between the exhaust pipe 14 and the vacuum pump. Keeping the substrate temperature at 5 ° C
As will be described later, this is to maintain the resistance of the resist of the mask material used for selective etching, to prevent the resist from deteriorating due to high temperature, and to prevent a drive that makes peeling difficult.

First, the flow rate ratio between BCl ₃ supplied from the first reaction gas introduction pipe 12 and Cl ₂ supplied from the second reaction gas introduction pipe 13 is variously changed to determine the etching rate. Explain if it changes. In the case of a gallium nitride-based n-type semiconductor, BCl ₃ alone can be expected to have some etching effect. However, these two etching gases are indispensable for etching other gallium nitride-based semiconductors, especially gallium nitride-based p-type semiconductors. FIG. 2 shows the results of examination on how the etching rate of the gallium nitride-based p-type semiconductor changes when the flow rate ratio of BCl ₃ and Cl ₂ is changed at an etching pressure of 1 Pa and an RF output of 120 W. . As is clear from FIG. 2, Cl ₂ / (Cl ₂ + BCl ₃ ) is 0.02
It is understood that a high etching rate is obtained and the effect of dry etching appears only when the ratio is 0.8 to 0.8. More specifically, it can be seen that the expected dry etching effect appears when Cl ₂ is contained in the reaction gas at 1% or more. This seems to be because the reactivity of Cl ₂ and the effect of sputtering of BCl ₃ must be synergistically manifested in etching the gallium nitride-based p-type semiconductor.

[0015] Figure 3 is RF output 120 W, the etching pressure 5 Pa, a diagram showing a flow rate dependency of BCl ₃ of gallium p-type semiconductor in the etching rate nitride in a case where the flow rate of Cl ₂ and 5sccm constant, the BCl ₃ 10sc
It can be seen that a substantially constant etching rate can be obtained at cm or more. FIG. 4 shows RF output 120 W, etching pressure 5
In Pa, a view showing a Cl ₂ flow rate dependency of the etching rate of the gallium nitride-based p-type semiconductor in the case of the flow rate of BCl ₃ and 5 sccm constant after reaching the maximum value in the vicinity Cl ₂ 5 sccm, the etching rate is removed It can be seen that is decreasing. FIG. 5 shows the dependence of the etching rate of the gallium nitride-based p-type semiconductor on the pressure inside the vacuum chamber 11, that is, the etching pressure dependence on the RF output 120.
As a result of measurement at W, BCl ₃ flow rate of 5 sccm, and Cl ₂ flow rate of 5 sccm, it can be seen that the etching rate becomes almost maximum at an etching pressure of 1 Pa, and the etching rate gradually decreases when the pressure is further increased. FIG.
Is etching pressure 5 Pa, BCl ₃ flow rate 5 sccm, C
l and ₂ flow first electrode 15 of the GaN-based p-type semiconductor of the etch rate of 5sccm second electrode 16
It is a figure which shows the RF power dependency applied during, ie, RF output dependency. It can be seen that the etching rate increases almost in proportion to the RF output. Of the conditions shown in FIGS. 2 to 6, when the etching rate is high, p-type G is used.
aN, n-type GaN, p-type In _x Ga _1-x N, n-type In _x
Ga _1-x N, p-type _{In x Al y Ga 1-xy} N, n -type In
_x Al _y Ga _1-xy N and SiO ₂ etching rate is almost the same etching rate.

As described above, according to the plasma etching using BCl ₃ and Cl ₂ , a wide range of semiconductors, especially GaN-based compound semiconductors can be obtained without using an etching gas that is subject to the restriction of CFC gas. The dry etching applicable to is realized. In addition, the etching rate is sufficiently high and the production efficiency is high. From the above, in the present invention, the BCl ₃ flow rate is 50 sccm, the Cl ₂ flow rate is 5 sccm, the etching pressure is 1 Pa, and the RF output is 120.
W was selected as the optimum gallium nitride based semiconductor etching condition. Plasma etching under these conditions causes less undercutting, can form U-grooves having substantially vertical sidewalls, and causes less damage to the semiconductor substrate during etching.

A method of manufacturing the gallium nitride-based compound semiconductor blue light emitting diode according to the present invention using the above dry etching will be described with reference to FIGS. 7, 8 and 9 to 13. FIG. 7 is a cross-sectional view of the gallium nitride-based compound semiconductor blue light emitting diode 1 according to the manufacturing method of the present invention immediately before the assembly process. As shown in FIG. 7, the sapphire substrate 10
0 on top of the gallium nitride-based n-type semiconductor buffer layer 10
1. A gallium nitride-based n-type semiconductor contact layer 102 is formed, on which a gallium nitride-based n-type semiconductor clad layer 103, a gallium nitride-based semiconductor active layer 104, a gallium nitride-based p-type semiconductor clad layer 105, and a gallium nitride-based layer are formed. An n-side electrode 108 connected to the p-type semiconductor contact layer 106 and the gallium nitride-based n-type semiconductor contact layer 102 and a p-side electrode 107 connected to the gallium nitride-based p-type semiconductor cladding layer 105 are formed. The n-side electrode 107 is p
From the surface of the n-type semiconductor contact layer 106 to the p-type semiconductor clad layer 105, the active layer 104, and the n-type semiconductor clad layer 1.
The n-type semiconductor contact layer 102 is exposed at the bottom of the groove provided through the n.
It is formed so as to make ohmic contact with 02. More specifically as gallium nitride semiconductor used for the respective layers 101 to 106, are used _{In x Al y Ga 1-xy} N compound semiconductor. This is its composition (mole fraction)
This is because blue light emission in a wide range can be realized by adjusting x and y. Here, the composition x, y is 0 ≦
It satisfies x ≤ 1, 0 ≤ y ≤ 1, and x + y ≤ 1.

Gallium nitride-based n-type semiconductor buffer layer 10
1 is to alleviate the lattice mismatch between the gallium nitride based semiconductor contact layer 102 and the sapphire substrate 100. An In _x Al each composition value of _y Ga _1-xy N, for example, 0 ≦ x ≦ 1,0 ≦ y ≦ 1 , preferably, 0 ≦ x
≤ 0.5, 0 ≤ y ≤ 0.5. The gallium nitride-based n-type semiconductor contact layer 102 is for obtaining good ohmic contact with the n-side electrode 108. I
Each composition values of _{n x Al y Ga 1-xy} N , in the case of a gallium nitride-based n-type semiconductor contact layer 102, for example, 0 ≦ x
≤ 1, 0 ≤ y ≤ 1, preferably 0 ≤ x ≤ 0.3, 0
≤ y ≤ 0.3 is selected. Again, impurities such as silicon (Si) and selenium (Se) are added to make it n-type, but the impurity concentration is 6 x 10 ¹⁸ cm ^-3.
It is. Gallium nitride-based n-type semiconductor cladding layer 103
Constitutes the n-side of the pin junction forming the light emitting region.
In _x Al _y Ga used for the n-type semiconductor clad layer 103
Each composition value of _1-xy N is appropriately adjusted according to the wavelength to be emitted, and for example, 0 ≤ x ≤ 1, 0 ≤ y ≤ 1, preferably 0 ≤ x ≤ 0.3, 0.1 ≤ y ≤ 1 Be done. Also, again, impurities such as Si and Se are added to make it n-type, but the impurity concentration is 3 x
It is 10 ¹⁸ cm ^-3 . Gallium nitride based semiconductor active layer 104
Is a layer forming a central region of the light emitting region and not intentionally doped with impurities, that is, a substantially intrinsic semiconductor layer. In _x Al _y G used for the active layer 104
Each composition value of a _1-xy N is appropriately adjusted depending on the wavelength to be emitted, and for example, 0 ≤ x ≤ 1, 0 ≤ y ≤ 1
Preferably, 0 ≤ x ≤ 0.6 and 0 ≤ y ≤ 0.5 are selected. The gallium nitride-based p-type semiconductor cladding layer 105 is
It constitutes the p side of the pin junction forming the light emitting region. In _x Al _y Ga used for the p-type semiconductor clad layer 105
Each composition value of _1-xy N is appropriately adjusted according to the wavelength to be emitted in relation to the gallium nitride-based n-type semiconductor cladding layer 103 and the gallium nitride-based semiconductor active layer 104, but for example, 0 ≤ x ≤ 1 , 0 ≤ y ≤ 1, and preferably 0 ≤ x ≤ 0.3 and 0.1 ≤ y ≤ 1.0.
Further, impurities such as magnesium (Mg), beryllium (Be), and zinc (Zn) are added in order to make it p-type. The impurity concentration is 3 x 10 ¹⁸ cm ^-3 . The gallium nitride-based p-type semiconductor contact layer 106 is for providing a contact surface to the p-side electrode 107. p
_X Al _y Ga used for the type semiconductor contact layer 106
Each composition value of _1-xy N is, for example, 0 ≤ x ≤ 1, 0 ≤ y
≤ 1 Preferably 0 ≤ x ≤ 0.3, 0 ≤ y ≤ 0.3
To be chosen. Also, in order to make it p-type, Mg, B
Impurities such as e and Zn are added. The impurity density is 8 x 10 ¹⁸ cm ^-3 .

The p-side electrode 107 is an electrode transparent to the light emission of the gallium nitride based semiconductor active layer 104. Specifically, ITO (Indium Tin Oxide)
Is formed from a compound of a metal and oxygen such as Al,
A metal such as Ni, Pt, or Pd may be formed sufficiently thin.
The n-side electrode 108 is the other electrode, but it need not be particularly transparent. For example, Ti, Al, Ni, Pt,
It may be formed of a metal such as Pd.

With the above settings, In _x Al _y Ga _1-xy
The composition values of N are the gallium nitride-based n-type semiconductor cladding layer 103 and the gallium nitride-based p-type semiconductor cladding layer 105.
Has a band gap of gallium nitride based semiconductor active layer 10
It is determined to be larger than the band gap of 4. By doing so, the amount of carriers injected into the gallium nitride based semiconductor active layer 104 can be increased and the emission intensity can be further improved.

Next, a method of manufacturing the blue light emitting diode shown in FIG. 7 will be described with reference to FIGS. 8 and 9 to 13.

A) MO-C on the sapphire substrate 100
With VD or the like as shown in FIG. 9 n-In _x Al _y Ga
_1-xy N buffer layer 101, n-In _x Al _y Ga
_1-xy N contact layer 102, n-In _x Al _y Ga
_1-xy N cladding layer 103, non-doped In _x Al _y G
a _1-xy N active layer _{104, p-In x Al y} Ga 1-xy
The N cladding layer _{105, p-In x Al y} Ga 1-xy N contact layer 106 sequentially stacked. For example, the n-clad layer 103 has a thickness of 0.1 μm, the active layer 104 has a thickness of 0.2 μm, and the p-clad layer 105 has a thickness of 0.5 μm.
The thickness of the m, p contact layer 106 is 0.1 μm.
FIG. 8 shows the MO-CV for continuous growth of each of these layers.
An example of the outline of D device is shown. This equipment is radio frequency (RF)
Induction heating type low pressure CVD furnace, vacuum chamber 20,
It comprises a substrate holder 21 provided therein, a reaction gas introduction pipe 22, an exhaust pipe 23, and a high-frequency coil for heating the substrate placed on the substrate holder 21. However, the high-frequency coil is not shown for simplification. In the continuous epitaxial growth using FIG. 8, first, the sapphire substrate 100 is placed on the substrate holder 21, and the inside of the vacuum chamber 20 is evacuated to 10 ⁻² to 10 ⁻⁵ Pa. Then, the temperature of the sapphire substrate 100 is raised by high frequency induction heating and maintained at a predetermined temperature, and a reaction gas containing an organic metal is introduced.
As the reaction gas, for example, Ga (CH ₃ ) ₃ , In (CH ₃ ) ₃ , Al (CH ₃ ) at a substrate temperature of 850 ° C. to 1050 ° C.
₃ ) ₃ and NH ₃ etc. may be used, and these source gases are introduced together with a carrier gas composed of hydrogen, nitrogen and the like.
The growth pressure is about 1 Pa. In this way, the gallium nitride-based semiconductor is continuously grown from the buffer layer 101 to the contact layer 106. At that time, the respective component ratios of the reaction gas are switched to adjust the component ratio of each layer.
In order to add impurities, monosilane (Si
H ₄ ) and biscyclopentadienyl magnesium (C
P ₂ M _g ) etc. are introduced.

(B) Next, the buffer layers 101 to
Removed sapphire substrate 100 contact layer 106 were continuously deposited from CVD furnace, p-In _x Al _y Ga
An oxide film (SiO ₂ film) 111 as an etching mask is formed on the _{1-x- y} N contact layer 106 by using a sputtering method or a CVD method. The CVD method for forming the SiO ₂ film is a plasma CVD method or an optical CVD method.
Method or thermal CVD method may be used. Then, as shown in FIG. 10, the oxide film 1 is formed by a predetermined photolithography technique.
A photoresist 112 is patterned on 11. The photoresist may be a positive resist such as AZ. The oxide film has a thickness of, for example, 300 nm, and the photoresist has a thickness of, for example, 3 μm.

(C) Photoresist 112 shown in FIG.
As shown in FIG. 11, Cl ₂ and BCl are used as a plasma etching mask using a two-layer mask composed of the oxide film 111 and the oxide film 111.
_The p-contact layer 106, the p-clad layer 105, the non-doped active layer 104, and the n-clad layer 103 are etched by parallel plate plasma etching using ₃ to form a U-groove 113 having a depth of 1.2 μm. Layer 1
02 exposed. A part of the n contact layer 102 may be further etched. This plasma etching is B
The flow rate of Cl ₃ is 50 sccm, the flow rate of Cl ₂ is 5 sccm,
The etching pressure may be 1 Pa and the RE output may be 120 W for 10 minutes.

(D) The photoresist 112 used as the mask material for plasma etching is removed with NaOH, the oxide film 111 is removed with HF, and then the substrate is washed. An ITO film for the p-side electrode 107 is formed by the CVD method or the sputtering method on the p-contact layer 106 that has been subjected to predetermined slight etching. The p-side electrode 107 is patterned by the so-called lift-off method. Prior to the deposition of the ITO film 107, the semiconductor layer other than the portion in contact with the ITO film 107 is formed by the photoresist 11.
4 and then the ITO film 107 as shown in FIG.
Is deposited. After that, if the photoresist 114 is removed, the pattern of the p-side electrode 107 is formed only on the p-contact layer 106.

(E) Next, as shown in FIG. 13, an n-side electrode 108 is formed at the bottom of the U groove. The lift-off method is also used for forming the n-side electrode 108. That is, the portion other than the portion where the n-side electrode 108 is formed is covered with the photoresist 115 and Ti,
By depositing a metal material 108 such as 1 or Ni by a sputtering method or a vacuum evaporation method and then removing the photoresist, the n-side electrode 108 can be formed only on the bottom of the U groove (see FIG. 7).

(F) After the basic structure of the blue light emitting device is completed in this way, a dicing process is performed. That is, a diamond cutter is used to cut on a scribe line that has been previously mesa-etched and cut into a suitable size to obtain a large number of chips. Then, these chips are mounted on a predetermined stem (wire frame), and after wire bonding and molding, the blue LED of the present invention is completed.

Although omitted in the above description, the mesa etching of the scribe line for dicing is performed before the etching of the U groove 113 described in (b) and (c) above. That is, the SiO ₂ film is deposited immediately after the continuous epitaxy of the above (a), and dry etching using BCl ₃ and Cl ₂ is performed using a two-layer mask of the SiO ₂ film and the photoresist. This is because when a substrate on which a gallium nitride based semiconductor laminate is formed is cut into a large number of chips, the characteristics of the semiconductor are adversely affected by the cuts.
A groove is previously formed in the laminated body of gallium nitride based semiconductors. This is what is done in general mesa type semiconductors, but in the Ga—N system, good mesa etching could not be conventionally achieved. In the present invention, the gallium nitride-based n-type semiconductor clad layer 103, the gallium nitride-based semiconductor active layer 104, and the gallium nitride-based p-type semiconductor clad layer 10 are arranged along the position of the scribe line for cutting.
5. The gallium nitride-based p-type semiconductor contact layer 106 can be easily and accurately partially removed by plasma etching. After this, photoresist and SiO ₂
After removing the film and cleaning the substrate surface, the CVD of the SiO ₂ film 111 described in (b) above may be performed. After all, when the mesa etching is performed by dry etching, SiO ₂
The film is formed twice.

That is, according to the plasma etching using BCl ₃ + Cl ₂ gas of the present invention, the contact resistance of the n-contact layer 102, which is the etching surface, is larger than the contact resistance of the normally grown contact layer of 10 ⁻³ Ωcm ² . It is possible to realize 10 ⁻⁴ to 10 ⁻⁵ Ωcm ^{2 which} is one to two digits lower. This is due to the plasma etching of the present invention.
It is considered that the contact layer is less damaged, and nitrogen vacancies are formed during etching, and the nitrogen vacancies are n-type, which increases the carrier density on the etching surface. Therefore, according to the present invention, a light emitting device can be realized. Furthermore, in order to reduce etching damage, the gas flow rate may be changed toward the end of etching. For example, BCl ₃ from 50 SCCM to 5 SCC
This is achieved by gradually decreasing to M and simultaneously increasing Cl ₂ from 5 SCCM to 10 SCCM.

In the above description, the blue LED has been described, but a blue LD can also realize a product with high efficiency and high manufacturing yield.

Next, with reference to FIGS. 14A and 14B, another example of a method for manufacturing a blue light emitting device using the compound semiconductor according to the present invention will be described. FIG. 14A is a plan view of the blue light emitting element, and FIG. 14B is AA of FIG. 14A.
It is sectional drawing.

As shown in FIG. 14B, a gallium nitride-based n-type semiconductor buffer layer 7 is formed on the sapphire substrate 700.
01, a gallium nitride-based true semiconductor layer 702 is formed,
On top of that, a gallium nitride based n-type semiconductor contact layer 70 is formed.
3, gallium nitride-based semiconductor active layer 704, gallium nitride-based p-type semiconductor cladding layer 705, gallium nitride-based p-type semiconductor contact layer 706, and gallium nitride-based n-type semiconductor contact layer 703, and n-side electrode 708 and gallium nitride-based A p-side electrode 707 and a pad 710 connected to the p-type semiconductor contact layer 706 are formed. In addition, the pad 710 and the gallium nitride-based p-type semiconductor contact layer 7
Direct contact with 06 is avoided by the silicon oxide layer 709. Further, a protective film for the silicon oxide layer 711 is provided on the p-side electrode 707.

As an example, the thickness of the sapphire substrate 700 is 70 μm, and the gallium nitride-based n-type semiconductor buffer layer 70 is used.
1, the thickness of the gallium nitride-based true semiconductor layer 702 is 4 μm, the thickness of the gallium nitride-based n-type semiconductor contact layer 703 is 4 μm, and the thickness of the gallium nitride-based semiconductor active layer 704 is 0.2 μm. The thickness of the p-type semiconductor clad layer 705 is 0.4 μm, and the thickness of the gallium nitride-based p-type semiconductor contact layer 706 is 0.1 μm. The n-side electrode 708 is a double layer of gold and titanium. Titanium is directly connected to the gallium nitride-based n-type semiconductor contact layer 703, and gold forms the contact surface. Like the n-side electrode 708, the pad 710 is a double layer of gold and titanium. The p-side electrode 707 is a triple layer of nickel / gold / nickel or a double layer of gold / nickel.

The impurity concentration of the gallium nitride-based n-type semiconductor contact layer 703 is 2 × 10 ¹⁸ cm ^{−3 to} 2 × 10 ¹⁹ c.
m ^-3, impurity concentration of the gallium nitride-based p-type semiconductor cladding layer 705 is 1x10 ¹⁸ cm ^-3 to 5x10 ¹⁸ cm ^-3, the impurity concentration of the gallium nitride-based p-type semiconductor contact layer 706 is 2x
It is between 10 ¹⁸ cm ^{-3 and 1} × 10 ¹⁹ cm ^-3 .

As a gallium nitride-based semiconductor used for the gallium nitride-based semiconductor active layer 704, In _x Al _y Ga is used.
_1-xy N compound semiconductor is used. Its composition (mole f
By adjusting raction) x and y, blue light emission in a wide range can be realized. The composition x, y is 0 ≤ x ≤ 1,
It satisfies 0 ≤ y ≤ 1 and x + y ≤ 1. Other gallium nitride based semiconductors are based on GaN.

The etching up to the gallium nitride-based n-type semiconductor contact layer 703 is performed by the method already described in the first example. Incidentally, in the case of dry etching, the etching shape can be arbitrarily controlled, so that FIG.
It is possible to easily form the shape shown in FIG.

Next, with reference to FIGS. 15A and 15B, another example of the method for manufacturing a blue light emitting device using the compound semiconductor according to the present invention will be described. Here, a semiconductor laser is used. 15A is a plan view of the blue light emitting element, and FIG. 15B is a cross-sectional view taken along the line AA of FIG. 15A.

As shown in FIG. 15B, a gallium nitride-based n-type semiconductor buffer layer 8 is formed on the sapphire substrate 800.
01, a gallium nitride-based true semiconductor layer 802 is formed,
On top of that, a gallium nitride-based n-type semiconductor contact layer 80
3, gallium nitride based semiconductor clad layer 804, gallium nitride based true semiconductor active layer 805, first clad layer 806 of gallium nitride based p-type semiconductor, gallium nitride based p-type semiconductor layer 807, second of gallium nitride based p-type semiconductor Clad layer 808, gallium nitride-based p-type semiconductor cap layer 80
9, a gallium nitride-based p-type semiconductor contact layer 810, an n-side electrode 811 connected to the gallium nitride-based n-type semiconductor contact layer 803, and a p-side electrode 812 connected to the gallium nitride-based p-type semiconductor contact layer 810 are formed. There is.

Each of the layers 801 to 810 is made of In _x Al _y.
It is made of a gallium nitride-based semiconductor having a composition of Ga _1-xy N, and the composition values thereof are, for example, 0 ≤ x ≤ 1, 0 ≤ y.
≤ 1 Preferably, 0 ≤ x ≤ 0.3, 0 ≤ y ≤ 0.3
To be chosen. Before stacking the gallium nitride-based p-type semiconductor contact layer 810, the gallium nitride-based p-type semiconductor second cladding layer 808 and the gallium nitride-based p-type semiconductor cap layer 809 are etched to an appropriate width, and the etched portion _{in x Al y Ga 1-xy} N high resistance gallium nitride based semiconductor layer 813 of the composition of is formed, thereon by gallium nitride-based p-type semiconductor contact layer 810 is laminated on.

Gallium nitride-based true semiconductor active layer 805
Are formed as quantum wells, and are 100 in the case of a single layer.
Å-500 Å thickness, 10 Å-in case of multiple layers
Layers with different band gaps of 100 Å are formed by alternately laminating 10 layers.

[0041] As the gallium nitride-based semiconductor used in each layer 801-810 uses a compound semiconductor composition of _{In x Al y Ga 1-xy} N. Here, each composition value is, for example, 0 ≤ x ≤ 1, 0 ≤ y ≤ 1, preferably 0 ≤ x
≤ 0.3, 0.1 ≤ y ≤ 1, but generally the band gap of the gallium nitride-based true semiconductor active layer 805 must be smaller than the band gaps of the cladding layers sandwiching it.

Further, the etching up to the gallium nitride-based n-type semiconductor contact layer 803 is performed by the method using the etching gas containing boron trichloride (BCl ₃ ) and chlorine (Cl ₂ ) already described in the first example. Furthermore, the resonator end face of this laser, that is, the upper and lower ends in FIG.
The same method is applied to the plane parallel to the paper surface in (b).

[0043]

As described above in detail, the BC of the present invention
According to the plasma etching using l ₃ + Cl ₂ gas, the contact resistance of the n contact layer 102, which is the etching surface, is one to two orders of magnitude lower than the contact resistance 10 ⁻³ Ωcm ^{2 of} the normally grown contact layer. ^-4 ~
10 ⁻⁵ Ωcm ² has been realized. This is because the n-contact layer is less damaged by the plasma etching of the present invention, and nitrogen vacancies are formed during etching, and the nitrogen vacancies are n-type, which increases the carrier density on the etching surface. it is conceivable that.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an apparatus for performing dry etching according to the present invention.

FIG. 2 is a diagram showing the dependency of etching rate in dry etching of the present invention.

FIG. 3 is a diagram showing the dependency of etching rate in dry etching of the present invention.

FIG. 4 is a diagram showing an etching rate dependency in dry etching of the present invention.

FIG. 5 is a diagram showing dependence of etching rate in dry etching of the present invention.

FIG. 6 is a diagram showing dependence of etching rate in dry etching of the present invention.

FIG. 7 is a cross-sectional view showing a layer structure of a semiconductor chip of a gallium nitride-based compound semiconductor blue light emitting diode according to the present invention.

FIG. 8 is a CD forming a layer structure of a semiconductor chip of a gallium nitride-based compound semiconductor blue light emitting diode according to the present invention.
It is a schematic diagram showing a V device.

FIG. 9 is a process sectional view illustrating a method for manufacturing a semiconductor chip of a gallium nitride-based compound semiconductor blue light emitting diode according to the present invention.

FIG. 10 is a process sectional view illustrating a method for manufacturing a semiconductor chip of a gallium nitride-based compound semiconductor blue light emitting diode according to the present invention.

FIG. 11 is a process sectional view illustrating a method for manufacturing a semiconductor chip of a gallium nitride-based compound semiconductor blue light emitting diode according to the present invention.

FIG. 12 is a process sectional view illustrating a method for manufacturing a semiconductor chip of a gallium nitride-based compound semiconductor blue light emitting diode according to the present invention.

FIG. 13 is a process sectional view illustrating a method for manufacturing a semiconductor chip of a gallium nitride-based compound semiconductor blue light emitting diode according to the present invention.

FIG. 14A is a plan view of a blue light emitting device produced by a method according to the present invention, and FIG. 14B is a sectional view taken along line AA of FIG.

15A is a plan view of a blue light emitting element, and FIG. 15B is a sectional view taken along line AA of FIG.

FIG. 16 is a cross-sectional view of a layer structure of a semiconductor chip of a conventional gallium nitride-based compound semiconductor blue light emitting diode.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 Plasma etching apparatus 11 Vacuum chamber 13 Reactive gas introduction pipe 14 Exhaust pipe 15 First electrode 16 Second electrode 17 Quartz plate 100,700 Sapphire substrate 101,801 Gallium nitride-based n-type semiconductor buffer layer 102,803 Gallium nitride-based n-type semiconductor contact layer 103 gallium nitride-based n-type semiconductor clad layer 104, 805 gallium nitride-based semiconductor active layer 105, 808, 806 gallium nitride-based p-type semiconductor clad layer 106, 810 gallium nitride-based p-type semiconductor contact layer 107 p side Electrode 108 n-side electrode 111 Oxide film 809 Gallium nitride-based p-type semiconductor cap layer 813 High-resistance gallium nitride-based semiconductor layer

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical display location H01S 3/18 H01L 21/302 F

Claims (18)

[Claims] 1. A first cladding layer made of a gallium nitride based semiconductor of a first conductivity type, and a substantially intrinsic (intrinsic) layer.
) An active layer made of a gallium nitride-based semiconductor, and a second clad layer made of a gallium nitride-based semiconductor of a second conductivity type opposite to the first conductivity type. A method of manufacturing a blue light emitting device using a compound semiconductor, which comprises a step of etching the second cladding layer and the active layer with an etching gas containing boron chloride and chlorine. 2. The method for producing a blue light emitting device using a compound semiconductor according to claim 1, wherein the etching gas contains 20% or more of each of boron trichloride and chlorine. 3. The method for manufacturing a blue light emitting device using a compound semiconductor according to claim 1, wherein the etching is performed by plasma discharge using high frequency power. 4. The first cladding layer is n-type In _x
Al _y Ga _1-xy N compound semiconductor, the active layer is an intrinsic In _x Al _y Ga _1-xy N compound semiconductor, and the second cladding layer is a p-type In _x Al _y Ga compound semiconductor.
_The method for producing a blue light emitting device using a compound semiconductor according to claim 1, wherein the method is a _1-xy N compound semiconductor. 5. A buffer layer made of a first conductivity type gallium nitride based semiconductor is laminated on a sapphire substrate before the step of forming the laminated body. The values of the composition x and y are as follows. 0 ≤ x
≤ 0.5, 0.5 ≤ y ≤ 1, 0 ≤ x ≤ 0.3, 0.1 ≤ y ≤ 1 for the first cladding layer, 0 ≤ x ≤ 0.6, 0 ≤ y ≤ 0.5 for the active layer, Two
For clad layers of 0 ≤ x ≤ 0.3, 0.1 ≤ y
The method for manufacturing a blue light emitting device using the compound semiconductor according to claim 1, wherein ≦ 1.0. 6. The method for manufacturing a blue light emitting device using a compound semiconductor according to claim 1, wherein the etching is parallel plate type plasma etching. 7. The method for manufacturing a blue light emitting device using a compound semiconductor according to claim 1, wherein the etching is selective etching using a two-layer mask of an oxide film and a photoresist as an etching mask. 8. The method for manufacturing a blue light emitting device using a compound semiconductor according to claim 1, wherein a U groove having substantially vertical sidewalls is formed by the selective etching. 9. The blue light emitting device using a compound semiconductor according to claim 1, further comprising a step of forming an electrode on the bottom of the U groove formed by the selective etching after the selective etching. Production method. 10. A first cladding layer made of a gallium nitride based semiconductor of a first conductivity type and a substantially intrinsic (intrinsi) layer.
c) an active layer made of a gallium nitride based semiconductor,
Forming a layered body made of a second clad layer made of a gallium nitride based semiconductor of a second conductivity type opposite to that of the first clad layer, and forming a first etching mask on the second clad layer. Forming step, a first dry etching step of etching at least a part of the laminated body using the etching gas containing boron trichloride and chlorine using the first etching mask, and the first etching Forming a new second etching mask on the second cladding layer after removing the mask for etching, and using the second etching mask to form the second cladding layer and the active layer. A method for manufacturing a blue light emitting device using a compound semiconductor, which comprises a second dry etching step of etching. 11. The method for manufacturing a blue light emitting device using a compound semiconductor according to claim 10, wherein the first etching mask is a two-layer mask composed of an oxide film and a photoresist. 12. The method for manufacturing a blue light emitting device using a compound semiconductor according to claim 10, wherein the second etching mask is a two-layer mask composed of an oxide film and a photoresist. 13. The method for manufacturing a blue light emitting device using a compound semiconductor according to claim 10, wherein the first and second dry etching processes are plasma etching using a parallel plate type plasma etching apparatus. . 14. The compound semiconductor according to claim 10, further comprising a step of etching a part of the first cladding layer using the second etching mask, following the second dry etching step. A method for manufacturing a blue light emitting device using. 15. The compound semiconductor according to claim 10, further comprising a step of forming a first electrode layer on a part of the first clad layer after etching the first clad layer. Method for manufacturing blue light emitting element used. 16. The method for manufacturing a blue light emitting device using a compound semiconductor according to claim 10, further comprising the step of forming a second electrode layer on a part of an upper portion of the second cladding layer. . 17. The first cladding layer is n-type In.
_x Al a _y Ga _1-xy N compound semiconductor, the active layer is _{In x Al y Ga 1-xy} N compound semiconductor of the intrinsic, the second cladding layer is p-type an In _x Al _y Ga
_{A 1-xy} N compound semiconductor.
A method of manufacturing a blue light emitting device using the compound semiconductor according to 0. 18. The method further comprises the step of stacking a buffer layer made of a first conductivity type gallium nitride based semiconductor on the sapphire substrate before the step of forming the stacked body, wherein the values of the composition x and y are the buffer. For layers, 0 ≤ x
≤ 0.5, 0.5 ≤ y ≤ 1, 0 ≤ x ≤ 0.3, 0.1 ≤ y ≤ 1 for the first cladding layer, 0 ≤ x ≤ 0.6, 0 ≤ y ≤ 0.5 for the active layer, Two
For clad layers of 0 ≤ x ≤ 0.3, 0.1 ≤ y
11. The method for manufacturing a blue light emitting device using the compound semiconductor according to claim 10, wherein ≦ 1.0.