KR101031279B1 - Semiconductor light-emitting device - Google Patents

Abstract

An object of the present invention is to provide a light emitting device of high output and high efficiency by improving the use efficiency of the light emitted from the semiconductor light emitting device.

A semiconductor light emitting device of the present invention is a semiconductor light emitting device comprising a package substrate, a submount provided on the package substrate, a semiconductor light emitting element provided on the submount, and a reflector surrounding the submount and the semiconductor light emitting element, The position and size of the submount, the light emitting element and the reflector satisfy the following relationship (A) in the cross section perpendicular to the package substrate passing through the center of the semiconductor light emitting element.

r-1s ≤ (hs-d) × (1s-1c) / hc --- (A)

Where r, 1s and 1c are the distances from the dropping portion of the reflector, the outer circumference of the submount and the outer circumference of the semiconductor light emitting element to the center of the semiconductor light emitting element, respectively, and hs and d are the heights of the submount and the dropping portion of the reflector, respectively. Is the height of the upper surface of the semiconductor light emitting element from the upper surface of the submount.

Description

Semiconductor Light Emitting Device {SEMICONDUCTOR LIGHT-EMITTING DEVICE}

The present invention relates to a semiconductor light emitting device. More specifically, the present invention relates to a semiconductor light emitting device having a reflector surrounding a semiconductor light emitting element.

The trend toward higher power and higher efficiency of LEDs is expanding their applications. In addition to conventional applications such as colored indicators and large outdoor displays, LEDs are rapidly expanding in their use as backlight sources, headlights and lighting sources in mobile phones that emit white light. Attempts to meet this need call for further improved power and efficiency.

The LED chip is a type of LED epitaxial lamination structure formed on a general conductive substrate used for As type LED and a type of LED epitaxial lamination structure formed on insulation substrate used in many of N type LED. Are classified as: In the electronic type LED chip, the electrode is formed on the front surface of the semiconductor and the back surface of the substrate, that is, the upper electrode is formed on the upper surface of the LED chip and the lower electrode is formed on the lower surface of the LED chip, while the latter type of LED chip is In, two electrodes are formed on the surface of the semiconductor. An example of mounting a chip having upper and lower electrodes formed on the upper and lower surfaces of an LED chip is described in Japanese Patent Application Laid-Open No. 61-77347, and an example of mounting a chip having two electrodes formed on a semiconductor surface is given by way of example. For example, it is disclosed in Unexamined-Japanese-Patent No. 5-243613. In addition, there are further face-up chips in which the substrate surface functions as a mounting surface, and flip-chip chips in which the semiconductor surface functions as a mounting surface. In addition, there exists a technique that flip-chip type chips can be wired together with Au bumps to a member called a sub-mount having a larger size than the chip (see, for example, Japanese Patent No. 3257455). ).

Conventional submounts have been used as electrical circuits or as protection circuits against electrostatic breakdown, but have not been used to improve the use efficiency of light emitted from semiconductor light emitting devices. As for the size, the submount has the same size as the size of the LED chip or generally increases in size by the area of the wire bonding pad.

In addition, a conventional semiconductor light emitting device having a reflector is known (for example, see FIG. 1 of Japanese Patent Laid-Open No. 2003-8074). In practice, in the drilling of the reflector, the opening in the bottom surface is stretched to a thickness of about 100 mu m, as shown in Fig. 6, and a part of the light emitted from the semiconductor light emitting element is the drooping portion 5 of the reflector and the package substrate. Reach on the non-reflective surface of face 7; In other words, the light utilization efficiency is bad because the light is not used efficiently.

In addition, a semiconductor light emitting device using a conventional parabolic reflector is known (for example, see Fig. 1 of Japanese Patent Laid-Open No. 58-164276). If the focus is a semiconductor light emitting element, the reflector must have a large opening. Thus, a part of the light emitted from the semiconductor light emitting element likewise reaches on the dripping portion 5 of the reflector and the non-reflective surface of the package substrate surface 7; In other words, the light utilization efficiency is bad because the light is not used efficiently.

That is, in the semiconductor light emitting device having the reflector attached on the mounting surface of the package substrate in a subsequent step, the opening of the bottom surface of the reflector is inevitably stretched to a thickness of about 100 mu m. On the other hand, the light emitting device chip usually has a thickness of 50㎛ ~ 500㎛. Therefore, in the conventional LED package, in which the reflector is attached to the subsequent step, the dropping portion faces the chip in the horizontal direction, so that the light beam is not limited to the optical design. In addition, stray rays are repeatedly reflected and attenuated between the chip and the package substrate, resulting in loss of light and efficiency.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems derived from a semiconductor light emitting device having a reflector and to improve the use efficiency of the light emitted from the semiconductor light emitting device to provide a light emitting device of high output and high efficiency.

The present invention provides the following apparatus.

(1) a semiconductor light emitting device comprising a package substrate, a submount provided on the package substrate, a semiconductor light emitting element provided on the submount, and a reflector surrounding the submount and the semiconductor light emitting element, wherein the submount; The position and size of the light emitting element and the reflector satisfy the following relationship (A) in the cross section perpendicular to the package substrate passing through the center of the semiconductor light emitting element.

r-1s ≤ (hs-d) × (1s-1c) / hc --- (A)

Where r, 1 and 1c are the distances from the dropping portion of the reflector, the outer circumference of the submount and the outer circumference of the semiconductor light emitting element to the center of the semiconductor light emitting element, respectively, and hs and d are the height of the submount and the dropping portion of the reflector, respectively. Is the height of the upper surface of the semiconductor light emitting element from the upper surface of the submount.

(2) The semiconductor light emitting device according to (1), wherein the side surface of the reflector is a parabolic surface, and its focus is the center of the semiconductor light emitting device.

(3) The semiconductor light emitting device according to (1) and (2), wherein the semiconductor light emitting element is a face up type.

(4) The semiconductor light emitting device according to (1) and (2), wherein the semiconductor light emitting element has upper and lower electrodes on the upper and lower surfaces thereof.

The present invention provides a high output light emitting device in which light extraction efficiency of a semiconductor light emitting device equipped with a reflector is improved. In the design of the reflector, the diameter of the reflector and the height of the reflector can be freely designed by changing the height of the submount of the semiconductor light emitting element while maintaining the luminous efficiency. This makes it possible to increase efficiency and output in colored indicators and large outdoor displays, as well as backlight sources, headlights and illumination sources of mobile phones emitting white light.

In addition, according to the size and shape of the sub-mount and the package, it is possible to minimize the light loss. The present invention can increase the output and efficiency of the light emitting device regardless of the size. It is possible to provide a high power and high efficiency white LED and colored LED by using a semiconductor light emitting element as an excitation source and adding a material for changing the wavelength, without being limited to the short wavelength infrared monochromatic light emitting element.

1 is a schematic cross-sectional view showing a semiconductor light emitting device manufactured in Example 1. FIG.

2 is a schematic plan view of the semiconductor light emitting device manufactured in Example 1. FIG.

3 is a schematic plan view showing a semiconductor light emitting device of the present invention using a rectangular semiconductor light emitting element.

4 is a schematic plan view of a semiconductor light emitting device of the present invention using a polygonal semiconductor light emitting element.

Fig. 5 is a schematic plan view showing a semiconductor light emitting device of the present invention using an elliptical reflector.

6 is a schematic cross-sectional view showing a conventional semiconductor light emitting device having a reflector.

7 is a schematic cross-sectional view showing the positional relationship of the semiconductor light emitting device of the present invention.

8 is a schematic cross-sectional view showing a semiconductor light emitting device of the present invention using a parabolic reflector.

9 is a schematic cross-sectional view showing the semiconductor light emitting device manufactured in Example 2. FIG.

10 is a schematic cross-sectional view showing the semiconductor light emitting device manufactured in Example 3. FIG.

1 is a schematic view showing a cross section of a semiconductor light emitting device of the present invention manufactured in Example 1 to be described later, wherein light emitted from the semiconductor light emitting element 1 reaches a non-reflective surface other than the reflecting surface of the reflector 3. The ideal positional relationship of the chip 1, the submount 2, and the reflector 3 which prevents it is shown.

In order to prevent light from the semiconductor light emitting element from reaching both the package substrate surface 7 and the water level 5 of the reflector, it is important that a and b represented by the following general formula satisfy a ≦ b relationship.

a = r-1s

b = (hs-d) × (1s-1c) / hc

Here, as shown in Fig. 7, r is the distance from the center of the semiconductor light emitting element to the dripping portion of the reflector, 1s is the distance from the center of the semiconductor light emitting element to the outer periphery of the submount, and 1c is the center of the semiconductor light emitting element. Is the distance from the outer circumference of the semiconductor light emitting element, hs is the height of the submount, d is the height of the dropping portion, and hc is the height of the upper surface of the semiconductor light emitting element from the upper surface of the submount.

When the above relationship is satisfied, light from the semiconductor light emitting element does not reach both the package substrate surface and the water level of the reflector, so that the light emitting device is characterized by high output and high efficiency.

The reflecting surface of the reflector is a parabolic surface, and the height of the submount is preferably adjusted so that the semiconductor light emitting element is in focus. The surface of the reflector is more preferably a spherical, hyperbolic, polynomial curved surface, a curved surface such as a cone side or a cylindrical side, or a combination of planes such as a pyramid side, a footnote side. The reflector is preferably made of metal or resin and has an optically treated reflecting surface. As an optical treatment, the metal is mirror finished by polishing. As a diffusion finish, the metal is coated with granulation, embossing, or white paint. Alternatively, the resin is provided to mirror reflection by vapor deposition onto a reflective metal film. The reflective metal film preferably contains Au, Ag, Ti, Ni, Cu, Cr, Al or Sn.

The submount is preferably formed by using a semiconductor substrate such as silicon, GaP or GaAs, or a transparent substrate such as glass or sapphire, to planarize the placement portion of the chip from a cost point of view. The submount is often made of a low resistance conductive material and shape to supply power through the backside of the submount. In addition, the submount itself is a semiconductor element such as a Zener diode, and thus functions as a circuit for protecting the LED chip.

For example, referring to FIG. 9, when two wires are connected with electrodes on the surface of the LED chip, and the other end of the wire is directly connected to a lead of a package substrate for supplying power, the submount is a structural member of a single material. You may form using. Alternatively, a bond pad may be formed on the surface of the submount to increase the bond strength of the chip. In addition, when an LED chip has an electrode on a mounting surface, a wire pattern may be formed on the surface of a submount. In the case of a sub-mount for flip chip, an electrode pattern corresponding to the electrode array of the chip and an electrode pattern for the external terminal are formed on or inside the sub-mount.

The submount is usually formed in a rectangular shape, but may be formed in the shape of a polygonal plate such as a hexagonal plate, a curved shape such as a circular plate, or a hexagonal shape that also functions as a heat sink.

The surface of the submount is also preferably optically treated. Optical treatments include deposition of metal films, mirror finishes such as buffing, and diffusion finishes such as granulation, embossing, or painting with white paint. Once the surface of the submount is diffused finish, the light diffuses on the submount surface, reducing the intensity dispersion in the package.

 The package substrate may be a type in which a metal reflector is separately attached onto a printing plate. Japanese Laid-Open Patent Publication No. 2003-8074 discloses a printing plate coated on both sides with copper by using an insulating resin such as glass epoxy resin as a core, wherein an electrode pattern is formed by etching copper foil on a surface, and a metal such as aluminum The reflector is bonded with an insulating adhesive film to surround the mounting portion of the LED chip thereon. Instead of a substrate coated with copper on both sides of the glass epoxy resin core, a substrate having copper on one side, a substrate of a metal core on which both sides are coated with copper, a substrate of a metal core on which one surface is coated with copper, and both sides A substrate coated with copper sandwiched therebetween with a ceramic such as alumina or aluminum nitride, or a substrate coated with aluminum on both sides may be used. Such a package substrate typically has a thickness of 0.1 mm to 10 mm.

The semiconductor light emitting element is composed of an As type, P type or N type III-V compound semiconductor, or O type, S type or Se type II-VI compound semiconductor. It is preferable that the emission wavelength is from the deep ultraviolet band of 200 nm to the infrared band exceeding 1 µm. As an example of a semiconductor light emitting element, a semiconductor layer is formed on an insulating substrate such as sapphire, and two electrodes are formed on the surface of the semiconductor layer to electrically connect to a lead on the package substrate side or an electrode on a submount through two wires. Face-up ones electrically connected to the pattern, flip-chip ones in which two electrodes are in direct contact with the electrode pattern on the sub-mount, and a semiconductor layer are formed on the conductive substrate, and one electrode is the surface of the semiconductor layer. The other electrode is formed on the back side of the substrate, the electrode on the surface side of the semiconductor layer is connected to a lead on the package substrate side via a wire, and the back side of the substrate is chipped through a conductive adhesive. Listed are those of the type attached to the submount to fix and conduct. That is, the present invention is effective not only for flip chips, but also for face-up type semiconductor light emitting devices which are not usually mounted on a submount and semiconductor light emitting devices of the type having electrodes on the back side of the substrate.

In the present invention, the area of the dripping portion of the reflector to which the light from the light emitting element reaches is preferably 50% or less if the total peripheral area of the dripping portion of the reflector is 100%. More preferably, the area is 10% or less, most preferably the area is 0%. At 0%, the luminous intensity increases by about 10% on the parabolic axis of the semiconductor light emitting device having the parabolic reflector as compared to the 80%.

(Example)

Although an Example demonstrates this invention concretely below, this invention is not limited to this.

(Example 1)

 1 is a schematic cross-sectional view showing a semiconductor light emitting device manufactured in this embodiment, and FIG. 2 is a schematic plan view thereof.

The semiconductor light emitting element 1 was formed in the following manner. Using an MOCVD apparatus, an epitaxial laminated structure of an LED including a group III nitride compound semiconductor was first formed on a sapphire substrate. The surface of the epitaxial wafer was patterned to form a 1 mm square light emitting device according to the photolithography technique, and partially engraved the chip to the n-type layer by dry etching. A negative electrode of the light emitting device was formed on the etching portion, and a positive electrode containing a high reflectivity metal of the light emitting device was formed on the unetched surface. Thereafter, the back surface of the sapphire substrate was ground and polished to a thickness of about 80 µm, and the wafer was divided into flip chip type 1 square mm chips.

The submount 2 was obtained by forming an oxide layer on the surface of an n ⁺ type Si wafer and forming Al deposition 4 on the oxide layer in a pattern corresponding to the pattern of the positive electrode and the negative electrode. The submount was 2 square mm with a height of 270 µm. The light emitting element was 1 square mm having a height of 80 µm.

The flip chip semiconductor blue light emitting device formed as described above was mounted on a submount of the semiconductor light emitting device using Au bumps. The submount and the light emitting element had directions in the same direction, and their centers overlapped with each other. By using a conductive adhesive, they were fixed to a 50 mm x 150 mm aluminum package substrate 6 forming an electrode pattern, and an Au wire 10 having a diameter of 25 탆 was placed from the electrode 9 on the submount to the electrode on the package substrate. (8) was combined.

The aluminum reflector 3 was bonded to it by an adhesive agent. Here, the center of the light emitting element overlaps with the center of the reflector hole. An aluminum reflector was formed by machining a block of pure aluminum (cylindrical with a diameter of 15 mm and a height of 10 mm). The side (reflection surface) 3 of the reflector was tapered at 45 ° in the shape of a cone. The reflecting surface of the reflector was mirror-finished, and it had a hole of diameter 4mm and the height d of the dripping part 5 (refer FIG. 7) of 100 micrometers formed in the bottom surface. The positional relationship is designed to satisfy the above formula (A).

The light emission output of the semiconductor light emitting device thus obtained was evaluated. The total emission flux was 160 mW when a 350 mA forward current was supplied.

The present invention is in addition to the combination of "square chip, submount, circular reflector", "rectangle chip, submount, circular reflector", "polygonal chip, submount, circular reflector", and "square chip, submount, elliptical reflector. The same effect can be obtained when applied to various combinations of semiconductor light emitting devices. 3 is a schematic plan view showing a combination of "rectangular chip, submount, circular reflector", FIG. 4 is a schematic plan view showing a combination of "polygon chip, submount, circular reflector", and FIG. 5 is a "square chip, Sub-mount, elliptical reflector ". 8 is a schematic cross-sectional view showing the semiconductor light emitting device of the present invention when the side of the reflector is a parabolic surface.

(Comparative Example 1)

 The semiconductor light emitting device was manufactured in the same manner as in Example 1, except that the height of the submount was set to be 100 μm. Therefore, the obtained semiconductor light emitting device did not satisfy the above general formula (A). The obtained semiconductor light emitting device was evaluated in the same manner as in Example 1. The total radiant flux was 140 mW when a 350 mA forward current was supplied, which was inferior to that of the semiconductor light emitting device of Example 1.

(Example 2)

This embodiment deals with a face up chip in which two electrodes are formed on a semiconductor side surface. 9 is a schematic cross-sectional view showing the semiconductor light emitting device manufactured in this embodiment.

A semiconductor light emitting device was manufactured in the same manner as in Example 1, but a face up chip was used as the semiconductor light emitting device. A face up chip was obtained according to the following procedure.

The procedure is the same as in Example 1 until the epitaxial stack structure of the LED including the group III nitride compound semiconductor is formed on the sapphire substrate using the MOCVD apparatus until dry etching. The negative electrode of the light emitting element was formed in the etched portion, the positive electrode containing ITO of the light transmissive material of the light emitting element was formed on the unetched surface, and a portion of the electrode pad for wire bonding was formed thereon. Au was formed on the uppermost surface of the electrode pad. Thereafter, the back surface of the sapphire substrate was ground and polished to a thickness of about 80 µm, and the wafer was divided into 1 square mm flip chip chips.

The size of the submount, package, and reflector was the same as that of Example 1, and the positional relationship satisfied the above formula (A). The light emitting output of the semiconductor light emitting device thus obtained was evaluated in the same manner as in Example 1. The total radiant flux was 140 mW when a 350 mA forward current was supplied.

(Comparative Example 2)

A semiconductor light emitting device was manufactured in the same manner as in Example 2, except that the height of the submount was set to 100 μm. Therefore, the obtained semiconductor light emitting device did not satisfy the general formula (A). The obtained semiconductor light emitting device was measured in the same manner as in Example 1. The total emission rate was 120 mW when a 350 mA forward current was supplied, which was inferior to that of the semiconductor light emitting device of Example 2.

(Example 3)

This embodiment deals with a face up chip of the type having electrodes on the back side of the substrate. 10 is a schematic cross-sectional view showing the semiconductor light emitting device manufactured in this embodiment.

Using an MOCVD apparatus, an epitaxial stacked structure of an LED including a group III nitride compound semiconductor was formed on a SiC substrate in the same manner as in Example 1. The surface of the epitaxial wafer was patterned by photolithography to form a light emitting element of 1 square mm. A negative electrode of the light emitting device was formed on the entire back surface of the SiC substrate, and a circular positive electrode was formed while maintaining a pitch of 1 mm on a part of the surface where the group III nitride compound semiconductor was epitaxially grown. Thereafter, the SiC substrate was cut with a dicer so as to form a 1 mm square chip of a type having an electrode on the back side of the substrate. The chip had a thickness of 400 μm. Therefore, the chip had hc = 400 μm and 1c = 500 μm.

The submounts had sizes of hs = 500 μm and 1s = 1300 μm. The shape of the reflector was the same as that of Example 1 except that the sides were parabolic, that is, d = 100 μm and r = 2000 μm. Therefore, the obtained semiconductor light emitting device satisfied the above general formula (A). The semiconductor light emitting device thus obtained evaluated the light emission output in the same manner as in Example 1. The total radiant flux was 120 mW when a 350 mA forward current was supplied.

(Comparative Example 3)

A semiconductor light emitting device was manufactured in the same manner as in Example 3, except that the height of the submount was set to 100 μm. Therefore, the obtained semiconductor light emitting device did not satisfy the general formula (A). The obtained semiconductor light emitting device was evaluated in the same manner as in Example 1. The total radiant flux was 80 mW when a 350 mA forward current was supplied, which was inferior to that of the semiconductor light emitting device of Example 3.

The semiconductor light emitting device of the present invention is characterized in that light extraction efficiency and light output are improved, and are, for example, colored indicators and large outdoor display devices, and backlight sources, headlights and lighting sources of mobile phones emitting white light. It can be used very efficiently to provide very high commercial value.

Claims (4)

A semiconductor light emitting device comprising a package substrate, a submount provided on the package substrate, a semiconductor light emitting element provided on the submount, and a reflector surrounding the submount and the semiconductor light emitting element: The position and size of the submount, the light emitting element and the reflector satisfy the following relationship (A) in the cross section perpendicular to the package substrate passing through the center of the semiconductor light emitting element, The surface of the sub-mount is a semiconductor light emitting device, characterized in that the diffusion finish by granulation, embossing or white coating. r-1s ≤ (hs-d) × (1s-1c) / hc --- (A) [Where r, 1s and 1c are the distances from the dropping portion of the reflector, the outer periphery of the sub-mount and the outer periphery of the semiconductor light emitting element to the center of the semiconductor light emitting element, respectively, and hs and d are the Height, and hc is the height of the upper surface of the semiconductor light emitting element from the upper surface of the submount.] The method of claim 1, A side surface of the reflector is a parabolic surface, and the focus thereof is the center of the semiconductor light emitting device. The method of claim 1, The semiconductor light emitting device is a semiconductor light emitting device, characterized in that the face-up type. The method of claim 1, And said semiconductor light emitting element is of a type having upper and lower electrodes on upper and lower surfaces thereof.

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