JPH04221864A - Optical semiconductor device - Google Patents

Abstract

PURPOSE:To perform predetermined characteristics by exposing a P-N junction end in which different conductivity type layers are formed in order and which is produced on the sidewall of a semiconductor substrate by a liquid growing method, and covering it with an insulator layer. CONSTITUTION:A P-type layer 16 and an N-type layer 17 are grown and formed in order on a P<+> type semiconductor substrate 15 by a liquid growth method to form a P-N junction, and the end is exposed at the side to form a so-called mesa type semiconductor substrate 15. Insulator layers 19 each having about 0.1-1.0mum of a thickness are provided at the ends of the exposed junction 18 by a CVD method or boiling it in hydrogen peroxide. Thus, positive Cu<+> ionized by an electric field generated upon moving is so made as to be attracted to a negative electrode but not to adhere to the layers 19 covering the vicinity of the ends of the junction exposed at the sidewalls of the substrate 4.

Description

[Detailed description of the invention]

[Purpose of the invention]

0001

[Industrial Application Field] The present invention is applicable to optical semiconductor devices such as optical signal transmitters that combine light sources such as optical sensors, optical coupling elements (photocouplers), and pilot lamps using light emitting elements, as well as semiconductor light receiving elements. It is suitable for

0002

2. Description of the Related Art In the assembly process of semiconductor devices, lead frames, that is, supporting parts, are often used, and materials such as iron, iron-nickel alloys, and cladding materials of these elements are used. Recently, copper-based materials have also been put into practical use.

Moreover, in order to improve the bonding condition with the thin metal wire in the bonding process that is essential to the assembly process and the bonding condition with the transparent resin that functions as a protective layer, it is common to apply a silver or gold plating layer. Some copper-based metals are also treated in the same way.

By the way, FIG. 1 is a cross-sectional view of an optical semiconductor device such as an optical sensor, an optical coupling element (photocoupler), a light source such as a pilot lamp using a light emitting element, and an optical signal generator combined with a semiconductor light receiving element. This is explained by:

[0005] The support part made of the above-mentioned material is manufactured by an etching process or a pressing process using a mold. In the former, the entire surface is coated with a silver or gold plating layer after the etching process, and in the latter If so, use one that is partially coated with a silver or gold plating layer.

[0006] The thickness of the silver plating layer is 1 μm to 3 μm.
The thickness of gold is about 0.5 μm, and the thickness of the copper plating layer, that is, the copper-based member provided as a base, is about 0.1 μm.

In FIG. 1, a support portion 1 and an outer lead 2 are shown.
A plating layer 3 is displayed around each of them, and a semiconductor light emitting element 4 is overlaid and fixed to this using a conductive adhesive 5.

The semiconductor light emitting device 4 is formed by sequentially growing a P layer 6 and an N layer 7 on a P+ semiconductor layer 5 by a liquid phase growth method as shown in the cross-sectional view of FIG. 2 to form a semiconductor substrate. The PN junction end portion is exposed on the side surface of the semiconductor substrate to form a so-called mesa type.

Further, electrodes 8 and 9 made of conductive metal are provided on the N layer 7 and the P+ layer 5 that constitute the front and back surfaces of the semiconductor substrate.
will be established.

A thin metal wire 10 made of, for example, Au is bonded between the electrode 8 and the lead 2 by a bonding method, and then a light-transmitting sealing resin (not shown) is coated in a conventional manner to obtain a semiconductor light-emitting device. It will be done.

In an optical coupling device, which is a type of optical semiconductor device, the space between a light emitting element and a light receiving element mounted on a support member is filled and coated with an encap material made of an insulating material such as silicone containing a filler, and then these are coated with a resin. A method is adopted in which the material is protected by layers and used as an envelope.

0012

[Problem to be Solved by the Invention] When operating an optical semiconductor device mounted on a support part having a copper-based member as an underlying plating layer or a support part made of a copper-based material, there are factors that ionize copper in the vicinity. When there is, it is ionized as Cu+ due to the potential difference, and is attracted to the negative potential side by the electric field,
A metallic electrically conductive layer is formed in parallel with the PN junction.

[0013] Possible factors for ionizing copper include, for example, a filler added to silicone disposed within the optical coupler envelope.

For this reason, a phenomenon occurs in which the potential necessary for the operation of the optical semiconductor device flows through the metallic electrically conductive layer, making it impossible to obtain the desired characteristics.As a countermeasure, for example, nickel or A method was adopted in which a film such as gold was coated by means such as plating.

[0015] However, in the semiconductor industry, which is subject to severe price competition, the above-mentioned method of increasing costs inevitably becomes a problem.

The present invention was made under these circumstances, and even if an optical semiconductor element is mounted on a support member provided with a copper-based layer and a metallic electrically conductive layer is formed in parallel with the PN junction, An object of the present invention is to provide an optical semiconductor device that can exhibit predetermined characteristics.

[Configuration of the invention]

[0018]

[Means for Solving the Problems] A support portion including a copper-based member, a semiconductor substrate overlaid on and fixed to the support portion and disposed close to the copper-based member, and a PN formed on the semiconductor substrate.
The optical semiconductor device according to the present invention is characterized by a junction, a PN junction end exposed on the side surface of the semiconductor substrate, an insulating layer covering the PN junction end, and a transparent protective layer covering the laminate.

[0019]

[Function] In the optical semiconductor device according to the present invention, the PN junction end formed by sequentially stacking layers of different conductivity types on a semiconductor substrate using a liquid phase growth method is exposed on the side wall of the semiconductor substrate and covered with an insulating layer. .

For this reason, even if the semiconductor substrate is placed close to the copper-based member formed on the mounting support, ionized metal generated from the copper-based member can be prevented from adhering to the vicinity of the PN junction end. .

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. 3, 4, and 5, and new numbers will be given to parts that are the same as those in the prior art to aid understanding.

As shown in FIG. 3, on the P+ semiconductor substrate 15, a P layer 16 and an N layer 17 are sequentially grown by liquid phase growth to form a PN junction 18, and the ends thereof are exposed on the side. Thus, a so-called mesa-type semiconductor substrate 15 is formed.

An insulating layer 19 having a thickness of about 0.1 μm to 1.0 μm is provided on the exposed end of the PN junction 18 by CVD or boiling in hydrogen peroxide, and then the assembly process begins.

The assembly process is carried out using a lead frame 20, and the material may be iron, iron-nickel, copper, copper alloy, or a cladding material made of these elements.

The lead frame 20 is fully plated or partially plated and coated with a silver layer with a thickness of 1 μm to 3 μm or a gold layer with a thickness of about 0.5 μm to protect the thin metal wire during the bonding process or as a protective layer. A copper plating layer, that is, a copper-based member having a thickness of about 0.1 μm is previously formed as a base for this plating layer.

The classification between full plating and partial plating depends on the manufacturing method of the lead frame 20. When etching is used, partial plating is applied to the entire surface before the pressing process using a mold, and the lead frame 20 is partially plated. frame 20
The descriptions in FIG. 3 regarding the plating layers are collectively referred to as plating layers 21.

A light-emitting device, that is, a semiconductor device, is provided with a PN junction 18 formed by overlapping liquid-phase growth layers of different conductivity types, and is covered with an insulating layer 19, near a plating layer 21 whose base is a copper-based material. The optical semiconductor device 23 is manufactured by adhering to the conductive adhesive 22 or gold eutectic and further covering it with a transparent resin containing a filler (not shown) to form an envelope.

Note that the exposed surfaces of the P+ layer 15 and the N layer 17 are coated with a conductive metal layer to form electrodes 24 and 25.
Further, a thin metal wire, such as a gold wire, is electrically connected between the electrode 24 and an outer lead formed on the lead frame by bonding (see FIG. 1) to prepare for electrical connection with other electronic equipment.

In an optical coupling device, which is a type of optical semiconductor device, the optical semiconductor device to be mounted is a passive device and an active device, and silicone or the like is buried between the two before proceeding to the resin sealing process. The behavior of copper ions during operation of the optical semiconductor device 23 is shown in FIG. 4a, and the general circuit connection is shown in FIG. 4b.

As shown in FIG. 4a, Cu precipitates because
The conductive adhesive layer 22, that is, the conductive epoxy resin
When mounting the optical semiconductor element 23 on the lead frame 20 by curing at a high temperature of 200°C to 200°C, and when forming electrodes by bonding, a high temperature state of 200°C to 350°C
This is the high temperature state of 450° C. when mounted using gold eutectic.

The Cu deposited in this manner is ionized by the filler added to the transparent resin constituting the envelope of the optical semiconductor device 23, and also by the electrolyte made of chemical substances that has entered through the lead frame, such as plating. Treatment solutions are considered.

Moreover, the optical semiconductor device 23 is generally connected to a power source 27 through a resistor 26 as shown in FIG. 4b, and the positive Cu+ ionized by the electric field accompanying its operation is attracted to the negative electrode. However, it is not attached to the insulating layer 19 covering the vicinity of the PN junction end exposed on the side wall of the semiconductor substrate 4. In contrast, in the conventional optical semiconductor device 23, a metal conductive layer made of positive Cu+ is formed in parallel near the exposed PN junction end.

[0033]

Effect of the invention: In an optical semiconductor device in which an optical semiconductor element is mounted on a lead frame using a copper-based member, a rated current of, for example, 70 mA is applied to the light emitting element, and a rated current of 70 mA is applied to the light receiving element using an optical coupling element.
A energization leaving test was conducted in which 50 mW to 300 mW was applied. FIG. 5, which shows the results, is a graph showing the optical output deterioration versus time, with the vertical axis representing relative optical output and the horizontal axis representing time on a log scale. Straight line a represents an optical semiconductor device in which a light emitting element is mounted on a lead frame with a copper-based member according to a conventional technique, straight line b represents an optical semiconductor device in which a light emitting element is mounted on a copper-based lead frame according to a conventional technique, and straight line c
shows an optical semiconductor device according to the present invention.

That is, in the conventional straight lines a and b, the optical output is 5
While the time to reach 0% is about 400 hours, in the optical semiconductor device according to the present invention, no deterioration in optical output was observed for more than 10,000 hours, revealing a remarkable effect.
The superiority of the present invention is demonstrated.

[Brief explanation of the drawing]

FIG. 1 is an internal sectional view of a conventional optical semiconductor device.

FIG. 2 is a cross-sectional view of an optical semiconductor device manufactured by liquid phase growth.

FIG. 3 is a sectional view showing a main part of an optical semiconductor device according to the present invention.

FIG. 4A is a cross-sectional view showing the generation and movement path of Cu ions, and FIG. 4B is a commonly used electrical circuit diagram.

FIG. 5 is a graph illustrating optical output deterioration in a energized storage test versus time.

[Explanation of symbols]

15: Semiconductor substrate 18: PN junction, 19: insulator layer, 20: lead frame, 21: Plated layer containing copper-based members, 22: conductive adhesive, 24, 25: Electrode.

Claims (1)

[Claims] 1. A support portion including a copper-based member, a semiconductor substrate overlaid on and fixed to the support portion and disposed close to the copper-based member, a PN junction formed on the semiconductor substrate, and a side surface of the semiconductor substrate. An optical semiconductor device comprising: a PN junction end portion exposed to the PN junction end portion; and an insulating layer covering the PN junction end portion.