WO2004079830A1

WO2004079830A1 - Iii-v nitride compound semiconductor light-emitting device and method for manufacturing same

Info

Publication number: WO2004079830A1
Application number: PCT/JP2004/002589
Authority: WO
Inventors: Keiji Ito; Yoshiaki Hasegawa; Toshiya Yokogawa
Original assignee: Matsushita Electric Industrial Co., Ltd.
Priority date: 2003-03-06
Filing date: 2004-03-02
Publication date: 2004-09-16
Also published as: JP2006179508A

Abstract

A semiconductor light-emitting device comprising a III-V nitride compound semiconductor substrate, a semiconductor multilayer structure formed on the major surface of the substrate, a first electrode formed on the back surface of the substrate, and a second electrode formed on the semiconductor multilayer structure is disclosed. This semiconductor light-emitting device emits a light due to a current flowing between the first electrode and the second electrode. The radius of curvature which defines the amount of bending of the semiconductor light-emitting device is adjusted to be not less than 80 cm.

Description

Specification

Nitride III-V compound semiconductor light emitting device and method of manufacturing the same

The present invention relates to a nitride-based III-V compound semiconductor light emitting device formed using a nitride-based III-V compound semiconductor substrate such as a GaN-based semiconductor substrate. The technology relates to controlling the stress generated in the structure. Background art

In order to increase the storage capacity of optical discs, it is necessary to shorten the wavelength of laser light required for reading / writing data. At present, DVD player recorders for DVDs widely use red semiconductor lasers having a wavelength of 660 nm. This red semiconductor laser is, for example, a GaAs compound semiconductor made of InGaAlP-based compound semiconductor. Manufactured by epitaxial growth on a substrate.

In recent years, next-generation optical disks have been actively developed to expand the storage capacity of DVDs. Light sources for such next-generation optical discs are required to stably emit blue-violet laser light (wavelength 4 OO nm band) whose wavelength is even shorter than that of red light. 400 nm wavelength GaN-based semiconductor lasers are most expected as light sources for recording and reproduction of next-generation optical disks such as B1u-ray disks (trademark). However, there are some problems that must be solved for practical use.

Since the first report of laser oscillation in 996, attempts have been made to improve the device life of GaN-based semiconductor lasers by reducing drive current and voltage and reducing defects in semiconductor crystals. . However, the crystal quality of the GaN-based compound semiconductor constituting the GaN-based semiconductor laser is not sufficient and does not satisfy the element characteristics or the level required for practical use.

Conventionally, a sapphire substrate or a low dislocation-on-sapphire substrate has been used in the manufacture of a GaN-based semiconductor light-emitting device.However, such a substrate is thermally expanded with a nitride III-V compound semiconductor. It has the disadvantage that the coefficient difference is large and that it is not easy to form the end face of the GaN-based semiconductor laser.

For this reason, the use of GaN substrates instead of sapphire substrates has recently been studied (for example, Technical Report of IEICE).

LQE2001-29, 73 (2001)). However, for a light emitting device using a GaN substrate, no device that satisfies the practically required life time level has been obtained.

The present inventor believes that one of the factors that promotes the deterioration of the GaN-based semiconductor laser and the light emitting die is the force acting on the active layer. According to the studies made by the present inventors, when a large tensile force acts on the active layer, the element is significantly deteriorated, and the life time is extremely reduced. Such force depends on the type of substrate that forms the device and the nitride III-V group that forms the device. It depends strongly on the thermal history during crystal growth of compound semiconductors and during mounting with bonding materials.

So far, no effective method has been proposed for preventing the deterioration of a light emitting device using a GaN substrate due to the force of the active layer.

The present invention has been made in order to solve the above problems, and an object of the present invention is to provide a semiconductor light emitting device which prevents device deterioration due to force and has an improved life time, and a method for manufacturing the same. . Disclosure of the invention

The nitride-based II I-V compound semiconductor light-emitting device of the present invention comprises a nitride-based

A III-V compound semiconductor substrate, a semiconductor laminated structure provided on a main surface of the substrate, a first electrode formed on a back surface of the substrate, and a second electrode formed on the semiconductor laminated structure. Wherein the semiconductor light-emitting element emits light by a current flowing between the first electrode and the second electrode, and has a radius of curvature that defines the amount of warpage of the semiconductor light-emitting element. Adjusted to 〇 cm or more.

In a preferred embodiment, the radius of curvature is greater than or equal to 83 cm and, if necessary, is greater than or equal to 89 cm.

In a preferred embodiment, the thickness of the substrate is more than 100 171 and not more than 5 μm.

In a preferred embodiment, the thickness of the substrate is more than 15 jum.

In a preferred embodiment, the substrate is a GaN-based compound semiconductor group. · ©.

The semiconductor light-emitting element module includes any one of the nitride-based III-V compound semiconductor light-emitting elements and a support member to which the nitride-based in-V compound semiconductor light-emitting element is fixed. The semiconductor light emitting elements are joined by a molten metal.

A method of manufacturing a nitride III-V compound semiconductor device module includes: forming a nitride III-V compound semiconductor substrate; a semiconductor laminated structure provided on a main surface of the substrate; and a back surface of the substrate. Preparing a semiconductor light emitting device having a first electrode formed on the semiconductor laminated structure and a second electrode formed on the semiconductor laminated structure (Α); and using a bonding material to form the nitride III-V compound semiconductor device. A method of manufacturing a nitride-based III-V compound semiconductor device module including the step of mounting on a package (Β), wherein the thickness of the substrate of the semiconductor light emitting element and the mounting temperature in the step (Β) are adjusted. By doing so, the absolute value of the J force generated in the semiconductor multilayer structure is controlled to 0.22 GPa or less.

In a preferred embodiment, the step (B) includes a step of mounting the semiconductor light-emitting device on a submount, and adjusting a thickness of the substrate according to a coefficient of thermal expansion of the submount and the mounting temperature. You.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a cross-sectional view showing a configuration of a nitride-based II I-V compound semiconductor light emitting device according to the present invention.

FIG. 2 is a cross-sectional view showing a state in which the elements of FIG. 1 are mounted on a submount in a junction-up arrangement. FIG. 3 is a cross-sectional view showing a state in which the device of FIG. 1 is mounted on a submount in a junction-down arrangement.

FIG. 4 is a graph showing the relationship between the narcotic force applied to the active layer of the light emitting device and the substrate thickness in the embodiment of the present invention.

FIG. 5 is a drawing showing the relationship between the amount of warpage of the element and the radius of curvature of the warp.

BEST MODE FOR CARRYING OUT THE INVENTION

The GaN substrate has higher thermal conductivity and better heat dissipation than the sapphire substrate, but it should be used as thin as possible in order to minimize the rise in device temperature during laser operation. It is considered favorable.

However, according to the study by the present inventors, it has been found that when a GaN substrate is used, the element life greatly varies depending on the thickness of the substrate. It has been considered that the thinner the substrate used for a light emitting element such as a semiconductor laser, the better the heat dissipation, and the thinner the GaN substrate, the longer the life of the element. The inventors have found that when the substrate thickness is small, the life of the element is rather deteriorated, and have arrived at the present invention.

When a GaN substrate is used, when mounting a light emitting element in a chip state on a heat sink of a package via a submount or the like, a small distortion that does not pose a problem with a GaAs semiconductor laser is generated. Even if it is produced, the element lifetime tends to be degraded. This is probably because the hardness of the GaN-based semiconductor is higher than the hardness of the GaAs-based semiconductor, and even if the same magnitude of strain occurs, a larger internal i force is generated. Conceivable. Then, it is estimated that when such a force is applied to the active layer, the deterioration of crystallinity proceeds and the device life is shortened.

According to the experiments described later, by setting the thickness of the GaN substrate larger than the substrate thickness (approximately 50 to 65 m) which has been considered to be preferable in the past, the life of the element can be reduced. Deterioration can be suppressed.

(First Embodiment)

Hereinafter, a first embodiment of a semiconductor light emitting device according to the present invention will be described with reference to the drawings.

First, refer to FIG.囡 1 is a nitride-based material according to the present embodiment I I I

FIG. 2 is a sectional view of a group V compound semiconductor laser.

As shown in FIG. 1, this laser has a substrate 11 made of n-type gallium nitride and a laminated structure formed on the substrate 11. The stacked structure has an n-type buffer layer 12, an n-type cladding layer 13, an n-type guide layer 14, an active layer (multiple electron well layer) 15, and a p-type guide layer in order from the side closer to the substrate 11. 16, a p-type cladding layer 1, a p-type contact layer 18, and a current confinement insulating layer 19.

The p-type contact layer 18 has a ridge extending along the cavity length direction, and a region other than the upper surface of the ridge is covered with the current confinement insulating layer 19. A 0-type electrode 2 絶縁 b is provided on the current confinement insulating layer 19, and a P-type electrode 20a is arranged between the p-type electrode 2〇b and the p-type contact layer 18. This p-type electrode 20a is a portion of the upper surface of the type contact layer 18 that is not covered with the current confinement insulating layer 19 (Upper surface of the ridge). Note that an n-type electrode 21 is provided on the back surface of the substrate 11.

The composition and thickness of each layer constituting the above laminated structure can be set, for example, as shown in Table 1 below.

【table 1】

In the laser shown in FIG. 1, a current flows in the vertical direction between the p-type electrodes 20 a and 2 〇 b and the n-type electrode 21, so that light emission occurs near the active layer 15. FIG. 2 shows the laser of FIG. 1 mounted on a submount 22 by a junction-up arrangement. The submount 22 is made of aluminum nitride having excellent conductivity and heat dissipation, and is arranged on a heat sink in a package (not shown). In this specification, an object to which a chip of a semiconductor light emitting element is fixed may be referred to as a “support member” regardless of whether it is a submount or a heat sink. In this specification, a package in which a semiconductor light emitting element is fixed on such a support member is referred to as a “semiconductor light emitting element module”.

In the case of junction-up mounting, the n-type electrode 21 is sub-mounted

22 and a GaN substrate 11 is interposed between the laser PN junction and the submount 22. The heat generated in the active layer 15 mainly flows to the submount 22 via the GaN substrate 11 and is diffused to the heat sink.

FIG. 3 shows the laser of FIG. 1 mounted on a submount 22 with a junction-down arrangement. In the case of junction-down mounting, the p-type electrode 21 is bonded to the main surface of the submount 22 and the substrate 11 is not located between the PN junction of the laser and the submount 22. .

The implementations shown in Figures 2 and 3 are either case, typically 1

This is performed at a temperature of 90 ° C to 260 ° C. This is because the bonding and fixing between the submount 22 and the electrode of the laser are usually performed by soldering. As a result of the mounting process being performed at such a high temperature, Strain and internal force are generated between the semiconductor light emitting element and the submount when the temperature returns to room temperature after the combination, due to the difference in thermal expansion coefficient between the two.

Table 2 below shows the results of calculating the narcotic force generated in the active layer of the semiconductor laser of the present embodiment mounted as shown in FIG. 2 or FIG.

[Table 2]

The minus sign of ^ force in Table 2 means "pulling force" and the plus sign means "compression force".

As can be seen from Table 2, when mounted by the junction-down method, the stress acting on the active layer is a tensile stress regardless of the thickness of the substrate. Moreover, whereas _c "absolute value" of the force is reduced as the substrate thickness increases, when mounted in a junction-up method, the sign of the force acting on the active layer, the substrate thickness is 5 0~ 2 0 0 Ai At m, it is negative, and the absolute value of the force decreases as the substrate thickness increases. Then, at a certain substrate thickness between 20 Oim and 500 m, the absolute value of the narcotic force acting on the active layer becomes substantially 、, and then the sign of the force changes to brass. . Figure 4 is a graph of the contents of Table 2 above. The vertical axis of the graph in Fig. 4 is force, and the horizontal axis is substrate thickness. The data obtained by the junction-up implementation is the point of “酾”, and the data obtained by the junction-down implementation is the point of “▲”.

As can be seen from Table 2 and Fig. 4, in the case of mounting using a submount made of aluminum nitride, when the mounting temperature is set in the range of 190 to 260 ° C, the thickness of the gallium nitride substrate 11 If it is more than 100 m and less than 500 m, the range of the force acting on the active layer can be adjusted to a range of more than 0.12 GPa and less than +0.03 GPa. It is preferable to keep these 15 forces within the above range, because an increase in the power applied to the active layer causes a serious impairment in the reliability of the device.

In the case of the junction-up arrangement, if the substrate thickness is 65 n or more and 500 m or less, the power of the active layer can be suppressed within the range of 0.12 GPa or more and +0.03 GPa or less. Although not shown in Table 2, it is inferred based on Fig. 4 that, in the case of the junction-up arrangement, the substrate thickness is within the range of 200 m or more and 500 um or less] ^ Minimize the absolute value of the force Value exists. From the viewpoint of reducing the tensile force acting on the active layer, it is advantageous to increase the thickness of the substrate. However, with a substrate having a thickness exceeding 500 m, it becomes difficult to form the end face of the light emitting element by cleavage. Therefore, the thickness of the gallium nitride substrate is suppressed to a low level of collicity acting on the active layer. It is preferable that the thickness is set so that cleavage is easy.

In the case of junction-up mounting, the board thickness is preferably more than 100 m and not more than 500 m to keep the absolute value of the force generated in the active layer in a smaller range. It is even more preferred to exceed

As is clear from Table 2 and Fig. 4, when the board thickness is the same, the absolute value of the force acting on the active layer tends to be larger in the junction-down mounting than in the junction-up mounting. is there. Therefore, the effect of setting the board thickness large is more remarkable in the case of junk-down mounting.

Also in the case of junction-down mounting, the preferable size of the substrate thickness is more than 100 m, and more preferably more than 150 m.

In addition, it is preferable that the substrate shape is processed so that the substrate thickness is large (/ U easily, and the end surface of the element is easily formed. For example, a stripe is formed on the back surface side of the substrate where the element end surface is formed). If a lip groove is formed, the end face can be easily formed by cleavage.

In addition, it is difficult to actually measure the cooling force acting on each layer constituting the semiconductor effect element. It is relatively easy to measure the amount of warpage of an element that is warped. Therefore, the amount of warpage of the element can be measured by using, for example, an interferometer.

FIG. 5 shows the relationship between the amount of warpage of the element measured in the present embodiment and the radius of curvature of the warp. If the cavity length is set, the amount of warpage of the chip is d, and the radius of curvature of the warp is R, the following equation is established.

d = R-(1-c os Θ)

The above equation is equal to approximately ^{R- R · (1 -Θ 2/} 2).

d = RR · (1— Θ ² 2)

= R · Θ ^2/2

Here, using the relation of L = 2R〇,

d = L ² / 8R is obtained.

Using this relational expression, the amount of warp d of the tip and the radius of curvature R are related.

Table 3 below shows the amount of device warpage obtained when the device of FIG. 1 is mounted in a junction-down arrangement on a submount made of aluminum nitride.

[Table 3]

The upper part of Table 3 shows the warpage 璗 of the element obtained from the narcotic power calculation in Table 2, which agrees well with the measured values in the lower part. As shown in Table 3, when the thickness of the gallium nitride substrate is 100 Aim, the warpage of the device is 0.〇79 im, and when the thickness of the gallium nitride substrate is 200 m, the warpage of the device is 〇. 076 im. Table 4 below shows the radius of curvature obtained by setting L to 75 m ₍ Table 4).

As can be seen from Table 4, when the substrate thickness is in the range of 100 to 200 m, the radius of curvature of the element is in the range of about 89 to 93 cm. When the submount is made of aluminum nitride, the preferable lower limit of the radius of curvature in the junction-down arrangement is 89 cm. As can be seen from the above description, by adjusting the thickness of the gallium nitride substrate, the active layer of the element can be formed. It is possible to control the working lights.

(Second embodiment)

Hereinafter, a second embodiment of the present invention will be described.

The present embodiment is different from the first embodiment only in that the above-described submount 22 made of aluminum nitride is used, and instead of using the submount made of silicon carbide. .

The device shown in Fig. 1 is mounted on a submount made of silicon carbide by the junction down method or the junction up method. And calculated the narcotic force acting on the active layer of the device. Some of the results are shown in Table 5 below.

[Table 5]

As can be seen from Table 5, the relationship between the J force and the substrate thickness in the present embodiment also shows the same tendency as in the first embodiment. In the case of mounting using a submount made of silicon carbide, when setting the mounting temperature in the range of 190 ° C to 260 ° C,

By setting an appropriate value within the range of OO i m or more and 500 m or less, the range of the narcotic force acting on the active layer is reduced by 1 ◦ .22 GPa or more + ◦ 03

It can be suppressed to the range of GPa or less.

An element using a substrate having a thickness exceeding the above range is not preferable because not only the excessive force acting on the active layer becomes excessive, but also it becomes difficult to form an end face of the element.

Table 6 below shows the results of measuring the amount of warpage of the device when the device of FIG. 1 was mounted on a submount made of silicon carbide by the junction down method. [Table 6]

The upper part of Table 6 shows the calculated value of the warpage of the element obtained from the ^ force calculation, and the lower part shows the measured value of the warpage fogging. As shown in Table 6, when the thickness of the gallium nitride substrate is 100 m, the warpage of the device is 0.085 m, and when the thickness of the gallium nitride substrate is 200 m, the warpage of the device Ha〇. 080 im.

As can be seen from the above results, when using a submount made of silicon carbide, it is preferable to set a larger substrate thickness than when using a submount made of aluminum nitride. When the submount is formed from silicon carbide, the radius of curvature in the junction down arrangement is smaller than when the submount is formed from aluminum nitride. Therefore, in this embodiment, The preferred lower limit of the radius of curvature is 83 cm, more preferably 85 cm or more. However, from the viewpoint of heat conduction, the thickness of the substrate is made thin, and in order to make it easier, the radius of curvature should be 80 cm or more.

As described above, it is preferable to determine the optimum substrate thickness in consideration of the material (thermal expansion coefficient, etc.) of the supporting member such as a submount or the like using a gallium nitride substrate. Industrial applicability

According to the present invention, the force generated in the active layer of a light-emitting element having a nitride III-V compound semiconductor as a substrate can be controlled by adjusting the substrate thickness, thereby preventing the element from deteriorating due to the force. It becomes possible.

Claims

The scope of the claims

1. a nitride-based in-V compound semiconductor substrate, a semiconductor laminated structure provided on a main surface of the substrate, a first electrode formed on a back surface of the substrate, and a first electrode formed on the semiconductor laminated structure. A semiconductor light emitting device having two electrodes,

The semiconductor light emitting device may include: a space between the first electrode and the second electrode;

発光 The light is emitted by the current

A nitride-based III-V compound semiconductor light-emitting device, wherein a radius of curvature defining a warpage of the semiconductor light-emitting device is adjusted to 80 cm or more.

2. The nitride III-V compound semiconductor light emitting device according to claim 1, wherein the thickness of the substrate is more than 100 m and not more than 500 jum.

3. The nitride-based III-V compound semiconductor light-emitting device according to claim 2, wherein the thickness of the substrate exceeds 15 m.

4. The substrate is a G a N-based compound semiconductor substrate, the nitride according to claim 1 or et 3 III - V group compound semiconductor light emitting device ₍

5. A nitride III-V compound semiconductor light emitting device according to any one of claims 1 to 4,

A support member to which the nitride III-V compound semiconductor light emitting device is fixed;

With The semiconductor light emitting device module, wherein the support member and the semiconductor light emitting device are joined by a molten metal.

6. a nitride III-V compound semiconductor substrate, a semiconductor laminated structure provided on a main surface of the substrate, a first electrode formed on a back surface of the substrate, and a semiconductor electrode formed on the semiconductor laminated structure. A step (A) of preparing a semiconductor light emitting device having a second electrode;

(B) mounting the nitride-based Ml-V compound semiconductor device in a package using a bonding material;

A method for manufacturing a nitride-based II I-V compound semiconductor device module, comprising:

By controlling the thickness of the substrate of the semiconductor light emitting device and the mounting temperature in the step (B), the absolute value of the force generated in the semiconductor laminated structure is controlled to 0.22 GPa or less. A method for manufacturing an I-V compound semiconductor element module.

7. The step (B) includes a step of mounting the semiconductor light emitting device on a support member,

The method for producing a nitride-based Ml-V compound semiconductor device module according to claim 6, wherein the thickness of the substrate is adjusted in accordance with the thermal expansion coefficient of the support member and the mounting temperature.