JP2008235582A - Semiconductor device and led print head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve light emission efficiency of an LED12 by enlarging a light emission region 13 formed in a PN junction region. <P>SOLUTION: An N-side contact layer 5 is provided to contact the surface of an N-type semiconductor layer 8 which is opposite to a semiconductor substrate 20. A P-side contact layer 11 is provided to contact the surface of a P-type semiconductor layer 10 which is opposite to the semiconductor substrate 20. A P-side electrode 3 extends radially from around the center of the P-side contact layer 11, and connects to a contact part, comprising a plurality of arm-like projections contacting to the P-side contact layer 11, by the radial central part, while connected to a P-side electrode wiring through an insulating layer 3. An N-side electrode 6 has such shape as encloses the contact part of the P-side electrode 3 as across almost equal distances. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a semiconductor device such as an LED that emits light, for example, and an LED print head using the LED.

In semiconductor devices such as LEDs that generate light, technological development for increasing the light emission output is underway. For example, Patent Document 1 discloses a technique for preventing an electrode formed on the light extraction surface from blocking the output of light generated therein and reducing the light extraction efficiency. In this prior art, a ring-shaped first conductive side electrode formed on the light extraction surface of the surface emitting LED and a small circular second conductive side electrode at the center of the ring are formed on the opposite side. When the LED is seen through from the direction of the axis, both are sufficiently separated and do not overlap. As a result, the light generated in the light emitting region is output from the light extraction surface without being blocked by the first conductive side electrode.
JP 2005-123526 A

  In the above conventional technique, it is difficult to enlarge the light emitting region formed in the PN junction region, and there remains a problem to be solved that the light emission efficiency is lowered.

  The present invention is a semiconductor device in which a first conductivity type semiconductor layer and a second conductivity type semiconductor layer are sequentially stacked on a substrate, and is provided in contact with a surface of the first conductivity type semiconductor layer opposite to the substrate. The first conductive side contact layer, the second conductive side contact layer provided in contact with the surface of the second conductive type semiconductor layer opposite to the substrate, and the first conductive side contact layer are connected. A first conductive side electrode; and a second conductive side electrode connected to the second conductive side contact layer. The second conductive side electrode extends radially from a substantially central portion of the second conductive side contact layer. A contact portion having a plurality of arm-shaped protrusions in contact with the second conductive contact layer; and the contact portion and a radial central portion thereof, and is connected to the second conductive side contact layer via an insulating layer. And a first conductive side battery. It is mainly characterized in that it has a shape surrounding the contact portion of the second conductive side electrode in a substantially equidistant.

  According to the present invention, a contact portion that extends radially from the substantially central portion of the second conductive side contact layer and has a plurality of arm-shaped protrusions that are in contact with the second conductive contact layer, the contact portion and its radial approximate shape. And a lead portion disposed on the second conductive side contact layer via an insulating layer. The first conductive side electrode has a contact portion of the second conductive side electrode substantially equal By having a shape that surrounds the distance, the light-shielding region can be suppressed to the minimum, so that the effect of increasing the light emission efficiency is obtained. Further, by forming the distance between the first conductive side electrode and the second conductive side electrode approximately equal, the current density flowing between the first conductive side electrode and the second conductive side electrode is biased in the light emitting region. Can be reduced. As a result, the effect that the light quantity distribution is made uniform is obtained.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a plan view of an LED array chip according to the present invention.
As shown in the figure, an LED array chip 100 according to the present invention is formed by arranging a large number of LEDs 12 on a semiconductor substrate 20 as an example. A P-side electrode wiring 4 and an N-side electrode wiring 7 are led out from the LEDs 12 formed in an array. A P-side electrode pad 15 is formed on the tip of the P-side electrode wiring 4, and an N-side electrode pad 16 is formed on the tip of the N-side electrode wiring 7 on the semiconductor substrate 20. Here, both the P-side electrode pad 15 and the N-side electrode pad are pads for wire bonding, and are used when an LED array chip is connected to a driver IC chip or the like later to form an LED light emitting unit. .

FIG. 2 is a plan view of an LED according to the present invention.
This figure is a diagram for explaining in detail the LEDs 12 constituting the LED array chip 100 (FIG. 1).

3 is a cross-sectional view taken along the line XX in FIG.
4 is a cross-sectional view taken along the line YY in FIG.
Both drawings are enlarged sectional views for explaining the structure of the LED 12.
Hereinafter, the LED 12 will be described in detail with reference mainly to FIG. 2 and FIG. 3 and FIG. 4 in the description.

  As shown in the figure, an LED chip 12 according to the present invention includes a known metal organic chemical vapor deposition method (MOCVD method), metal organic chemical vapor phase epitaxy method (MBE method) on a semiconductor substrate (semiconductor substrate 20 as an example). The epitaxial wafer in which the N-type semiconductor layer 8 (FIGS. 3 and 4), the P-type semiconductor layer 10 (FIGS. 3 and 4), the N-side contact layer 5, and the P-side contact layer 11 are sequentially generated by the above. Are etched by wet etching, dry etching, or the like to form the N-side electrode 6, the N-side electrode wiring 7, the insulating layer 9, the P-side electrode 3, and the P-side electrode wiring 4.

  The N-side contact layer 5 is a portion that is interposed between the N-side electrode 6 and the N-type semiconductor layer 8 and injects drive current from the N-side electrode 6 to the N-type semiconductor layer 8 in a predetermined direction. The N-side electrode 6 has a shape that surrounds the contact portion of the P-side electrode 3 at approximately the same distance, and is formed of a metal containing Au, Ge, Ni, or the like that can be in ohmic contact with the N-side contact layer 5. Electrode. The N-side electrode wiring 7 is a metal wiring containing Au, Ge, Ni and the like that connects the N-side electrode 6 to the N-side electrode pad 16 (FIG. 1).

  The N-type semiconductor layer 8 (FIGS. 3 and 4) is a semiconductor layer epitaxially grown on the semiconductor substrate 20 (for example, a compound semiconductor such as AlGaAs). The insulating layer 9 is an insulating film formed by, for example, a silicon oxide thin film interposed between the P-side contact layer 11 and the N-side contact layer 5 and the P-side electrode wiring 4.

  The P-type semiconductor layer 10 is a semiconductor layer in which a predetermined impurity is diffused in a predetermined compound semiconductor layer. The P-side contact layer 11 is a portion that is interposed between the P-side electrode 3 and the P-type semiconductor layer 10 and injects a drive current from the P-side electrode 3 to the P-type semiconductor layer 10 in a predetermined direction.

The P-side electrode 3 extends radially from the substantially central portion of the P-side contact layer 11 and is connected to a contact portion having a plurality of arm-shaped projections at the contact portion and the substantially central radial portion thereof. An electrode formed on the semiconductor thin film, having a lead portion disposed on the P-side contact layer 11 via For example, it is made of SiN, SiO ₂ , Al ₂ O ₃ or the like. The P-side electrode wiring 4 is a wiring that connects the P-side electrode 3 and the P-side electrode pad 15 (FIG. 1) and is formed of, for example, a metal containing Ti, Pt, Au, or the like.

  The light emitting region 13 is a PN junction region between the N-type semiconductor layer 8 and the P-type semiconductor layer 10 and is a region that emits light by injecting a drive current. The N-type semiconductor layer 8 and the P-type semiconductor layer 10 are not limited to a single type of compound semiconductor layer such as AlGaAs, but may be formed of a plurality of semiconductor layers such as GaAs and AlGaAs. Further, they may constitute a heterostructure or a double heterostructure.

  The array chip 100 (FIG. 1) integrates a large number of the LEDs 12 described above, and the known metal organic chemical vapor deposition method (MOCVD method), metal organic chemical vapor phase epitaxy method (MOVPE method), and molecular beam epitaxy method. (MBE method) or the like, for example, a sacrificial layer is interposed on a GaAs substrate, a sapphire substrate, an InP substrate, a glass substrate, a quartz substrate, a Si substrate, or the like to produce an LED thin film.

  Since the LED thin film (LED array chip 100) can be made very thin, for example, 5 μm or less, it is characterized by being very flexible. In addition, unlike liquid crystal and organic EL, the LED thin film uses a material manufactured by the semiconductor epitaxial growth method, which has a proven track record as an extremely high quality and highly reliable material. It is characterized by being a material that can ensure the properties.

  As described above, the LED thin film is epitaxially grown so as to provide a sacrificial layer that can be selectively etched, and is lifted off as an LED thin film by selectively etching the sacrificial layer.

  Further, in the case of a compound semiconductor that is difficult to selectively etch the sacrificial layer, such as a GaN-based LED element, the LED light emitting element is obtained by grinding the back surface of the substrate as one of the means for thinning the substrate. Only the required epitaxial growth layer is thinned to about 5 μm or less, and the LED thin film is used as a light emitting element.

FIG. 5 is a schematic perspective view of the LED light emitting unit.
This figure shows a state in which the LED light emitting unit of the LED print head is configured using the LED array chip 100 (FIG. 1) according to the present invention.

  As shown in the figure, the LED array chip 100 cut out from the epitaxial wafer by dicing or the like is arranged side by side on a COB (Chip On Board) substrate 120 together with the driver IC chip 110, and both are arranged between the LED / IC. The connection wire 130 is connected using an electrode pad (not shown).

  The LED thin film (LED array chip 100) is characterized in that it is firmly bonded on the COB substrate 120 by intermolecular force due to hydrogen bonding. Therefore, the bonding surface of the LED thin film (LED array chip 100) and the surface of the Si substrate to be bonded are controlled so that the surface roughness, that is, the typical height difference between the peak and valley of the unevenness is about 5 nm or less. It is desirable.

  In order to make the bonding force stronger, it is desirable that those bonding surfaces be cleaned and activated by an energy wave, for example, a plasma device. Also, applying an activator is one of the methods for activating the joint surface.

Next, the characteristic functions of the LED 12 according to the present invention will be described with reference to FIGS.
As shown in FIG. 2, the LED 12 according to the present invention has, as an example, a thin X-shaped P-side electrode 3 (contact portion of the second conductive side electrode) and a curved shape substantially corresponding to the P-side electrode 3. Since the N-side electrode 6 is used, the light blocking area is reduced.

  Further, as shown in FIG. 2, since the distance between the P-side electrode 3 and the N-side electrode 6 is substantially equal, the narrow X-shaped P-side electrode 3 has a curved N-side. The bias of the current density in the light emitting region 13 of the current flowing toward the corresponding position of the electrode 6 is reduced. As a result, the light quantity distribution becomes uniform.

  In the above description, the shape of the contact portion between the P-side contact layer 11 and the P-side electrode 3 has been described as an X shape composed of four arm-shaped protrusions. The number of protrusions may be a plurality of protrusions extending radially from the portion, and the number of protrusions is not limited to four. The number of protrusions can be determined as appropriate from the shape of the P-type contact layer 11 or the ratio of the area covered by the protrusions.

Description of (Effect) As described above, according to the present invention, it is possible to form a large light emitting region in the PN junction region, and to obtain an effect that the light emission efficiency can be increased. In addition, since the distance between the P-side electrode and the N-side electrode can be formed to be substantially equal, the thin X-shaped P-side electrode 3 is directed to the corresponding position of the curved N-side electrode 6. Thus, there is an effect that the current density in the light emitting region 13 of the flowing current is reduced and the light amount distribution is made uniform.

  In this embodiment, the LED array chip as the semiconductor device configured in the first embodiment is used, and the LED head used in an electrophotographic printer or the like has a large luminous efficiency and a uniform light amount distribution. .

FIG. 6 is a cross-sectional view of the LED head.
As shown in the figure, the LED head 200 includes a base member 201, an LED unit 202, an LED light emitting unit 203, a lens array 204, a lens holder 205, and a clamper 206.

  The base member 201 is a member for fixing the LED unit 202, and an opening 201 a for fixing the LED unit 202 and the lens holder 205 to the base member 201 is provided on a side surface thereof using a clamper 206. It has been. It is injection molded using organic polymer materials.

  The LED unit 202 is a unit in which the LED light emitting unit 203 is integrated on a predetermined substrate. The LED light emitting unit 203 is a unit in which the LED array chip 100, the driver IC chip 110 and the like described with reference to FIG. 5 are mounted on the COB substrate 120 and connected by the LED / IC connection wire 130. .

  The lens array 204 is an optical lens group in which a large number of columnar optical lenses are arranged along the LED array chip 100 arranged on the LED light emitting unit 203. The lens holder 205 is a part that holds the lens array 204 at a predetermined position of the base member 201. The clamper 206 is a spring material that integrally holds each component through an opening 201 a provided in the base member 201.

  An optical signal generated by the LED light emitting unit 203 constituting the LED head 200 described above passes through the rod lens array 204 and is irradiated to a photosensitive drum (not shown), for example. Since the LED array chip described in the first embodiment is used for the LED head 200, the photosensitive drum or the like is irradiated with an optical signal having high light emission efficiency and a uniform light amount distribution. .

Description of (Effects) As described above, the LED head 200 according to the present embodiment uses the LED array chip described in the first embodiment, so that the light signal has a high light emission efficiency and a uniform light amount distribution. The effect of outputting is obtained.

  In the above embodiment, the case where the LED as a semiconductor device according to the present invention is used in a printing apparatus such as an electrophotographic printer has been described as an example. However, the present invention is not limited to this example. In other words, it can be suitably used for traffic information display devices and the like that have been used in large quantities in recent years in transportation.

It is a top view of the LED array chip by this invention. 1 is a plan view of an LED according to the present invention. FIG. 3 is a sectional view taken along the line XX in FIG. 2. FIG. 3 is a YY cross-sectional arrow view of FIG. 2. It is a schematic perspective view of a LED light emission part unit. It is a cross-sectional view of an LED head.

Explanation of symbols

3 P-side electrode 4 P-side electrode wiring 5 N-side contact layer 6 N-side electrode 9 Insulating layer 10 P-type semiconductor layer 11 P-side contact layer 12 LED
13 Light Emitting Area 20 Semiconductor Substrate

Claims (4)

A semiconductor device in which a first conductive semiconductor layer and a second conductive semiconductor layer are sequentially stacked on a substrate,
A first conductive side contact layer provided in contact with a surface of the first conductive type semiconductor layer opposite to the substrate;
A second conductive side contact layer provided in contact with a surface of the second conductive type semiconductor layer opposite to the substrate;
A first conductive side electrode connected to the first conductive side contact layer;
A second conductive side electrode connected to the second conductive side contact layer,
The second conductive side electrode extends radially from a substantially central portion of the second conductive side contact layer, has a plurality of arm-shaped protrusions in contact with the second conductive contact layer, the contact portion, and the contact portion And a lead portion disposed on the second conductive side contact layer via an insulating layer, connected at a substantially central portion in the radial direction,
The semiconductor device according to claim 1, wherein the first conductive side electrode has a shape surrounding a contact portion of the second conductive side electrode at an approximately equal distance.   The semiconductor device according to claim 1, wherein the contact portion has four protrusions and is substantially X-shaped.   3. The semiconductor device according to claim 1, wherein the first conductive semiconductor layer and the second conductive semiconductor layer form a light emitting diode element. 4.   An LED print head comprising: the semiconductor device according to claim 3; a drive device that drives the semiconductor device; and a lens that collects light emitted from the semiconductor device.

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