JPS6269694A - Semiconductor laser - Google Patents

Abstract

PURPOSE:To protect a laser diode from dielectric breakdown even if static charge is applied by a method wherein a protecting diode is formed by introducing the second conductivity type impurity into the first conductivity type semiconductor substrate and the protecting diode is connected to a laser diode in parallel. CONSTITUTION:A photodiode 24 is composed of an impurity region 22 and a semiconductor substrate 21 and a protecting diode 25 is composed of an impurity region 23 and the semiconductor substrate 21. Even if static charge on an operator is applied to one of the electrodes of a laser diode 31 through an external lead, when the direction of the charge application is the forward direction of the protecting diode 25, the static charge reaches the other electrode of the laser diode 31 through the protecting diode 25 and hence a high voltage is not applied between the two electrodes of the laser diode 31. On the other hand, when the static charge is applied to the direction opposite to the direction of the above case, a Zener diode, which has a breakdown voltage a little higher than the forward voltage of the laser diode 31, can be employed as the protecting diode 25. With this constitution, the laser diode 31 can be protected from dielectric breakdown.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a semiconductor laser device, and specifically relates to a laser diode and a protection diode connected in parallel with the laser diode to protect the laser diode from undesired high voltage. The present invention relates to a semiconductor laser device that combines the above.

<Prior Art> Fig. 2 is a perspective view showing a conventional semiconductor laser device. First, to explain the configuration, 1 is a steel base, and a copper heat sink 2 is fixed to this base 1. has been done.

A submount 3 made of silicon is attached to the heat sink 2, and a laser diode 4 is soldered to the submount 3. Since the submount 3 is made of silicon, its expansion coefficient is similar to that of the laser diode 4 which is made of a gallium arsenide compound semiconductor, and the heat generated by the laser diode 4 when emitting light causes the laser diode to expand. This is to suppress thermal strain occurring in the laser diode 4 even if the laser diode 4 expands. This laser diode 4 has a silicon submount 3 as one electrode, and the other electrode of the laser diode 4 is connected to an external lead 5 via a bonding wire. The aforementioned base 1
The monitor photodiode 6 is connected to the submarine 1 and 3
One electrode of the photodiode is connected to an external lead 7 via a bonding wire. The other electrode of the laser diode 4 and the other electrode of the photodiode 6 are connected to an external lead 8, and these external leads 5, 7.8 are connected to wiring on a printed board (not shown). The base 1 is fitted with a cap 9 such that the laser diode 4 and the photodiode 6 are sealed in the internal space.
A transparent glass portion 1o is provided on the top surface. Therefore, the coherent light emitted from the laser diode 4 passes through the glass part IO and is emitted to the outside.
Coherent light passing through the glass portion 1o is also emitted in a symmetrical direction, and a photodiode 6 located on the optical path
generates a photovoltaic force.

In the prior art example 1, after a laser diode device is manufactured through a series of semiconductor manufacturing processes, it is assembled together with other circuit elements into a predetermined device, such as a pickup of a laser disk device. During this time, the laser diode device often comes into contact with the worker, and when the worker moves, the clothes rub against each other, and static electricity is generated due to the friction of the clothes.If the clothes are charged, the laser diode device 4 When touched, a high voltage was applied to the laser diode 4 and the laser diode 4 was sometimes destroyed. Therefore, in order to protect the laser diode 4 from being destroyed by high voltage, it is necessary to install an anti-static floor in the assembly workshop and to wear an anti-static weir or wear an anti-static belt when working. there were.

<Problems to be solved by the invention> However, making the floor of the workplace an antistatic floor
There was a problem in that the construction cost of the workshop increased, and this was reflected in the products, causing the price of laser disc equipment etc. to rise by 1. Furthermore, there are also problems in that performing assembly work while wearing an antistatic weir has poor work efficiency, and that attachment and detachment of the antistatic weir is complicated. In view of the problems of the conventional example, a protection diode including a semiconductor substrate of a first conductivity type and an impurity region of a second conductivity type formed in the semiconductor substrate, and a semiconductor substrate of the first conductivity type are provided. One electrode is the laser diode and has an undesired high voltage on the laser diode,
For example, when static electricity is applied, the protection diode allows the charge to pass through, thereby preventing high voltage from being applied to the laser diode.

<Embodiment> FIG. 1 is a plan view of an embodiment of the present invention, and 21 indicates an n-type semiconductor substrate. This semiconductor substrate 2] has p
type impurities are diffused to form p-type impurity regions 22 and 23. The impurity region 22 forms a photodiode 24 together with the semiconductor substrate 21, and the impurity region 23
forms a protection diode 25 together with the semiconductor substrate 21.

The surface of the semiconductor substrate 21 is covered with a precisely patterned silicon dioxide film 26, which forms an impurity region 22.2.
3 are connected to electrodes 29 and 30 patterned on the silicon dioxide film 26 through contact holes 27 and 28 formed in the silicon dioxide film 26. A laser diode 31 is soldered to the surface of the semiconductor substrate 21 that is not covered with the silicon dioxide film 26. The laser diode 31 and the electrode 3o are connected by a bonding wire 32, and the electrodes 29, 30 are connected to external leads (not shown) by bonding wires 33a, 33b.

Next, the manufacturing process of the semiconductor laser device will be explained as follows. First, the surface of the n-type semiconductor substrate 21 is thermally oxidized to grow a silicon dioxide film 41 (Fig. 3(a)
)), this silicon dioxide film 41 is patterned using lithography technology, p-type impurities are diffused, and impurity regions 2 are formed.
3 (Fig. 3(b)). Next, the silicon dioxide film 41 is patterned again using lithography technology, and p
The impurity of the mold is diffused to form an impurity region 22 (FIG. 3(C)). Silicon dioxide film 4 on the surface of semiconductor substrate 21
1 is removed once, and the surface of the semiconductor substrate 21 is again covered with a silicon dioxide film 41, and then holes 1 to 1 are formed (FIG. 3(d)). After aluminum is deposited, this is patterned. Form electrodes 29,30. Next, the silicon dioxide film 41 is patterned using lithography technology to determine the mounting position of the laser diode 31 (FIG. 3(e)). After vapor-depositing a metal for brazing and patterning this, the laser diode 31 is soldered to the semiconductor substrate 21 (FIG. 3(f)).

The semiconductor laser device according to the above embodiment includes a predetermined device,
For example, when installed in a laser disk device, even if static electricity charged on a worker is applied to one electrode of the laser diode 31 through the external lead, if this is in the forward direction of the protection diode 25, the static electricity passes through the protection diode 25 and the laser diode 31
Since the voltage reaches the other electrode of the laser diode 31, a large voltage is not applied between the two electrodes of the laser diode 31. On the other hand, if static electricity is applied in the opposite direction, a Zener diode with a breakdown voltage slightly higher than the forward voltage of the laser diode 31 may be used as the protection diode 25; Can be protected from destruction.

Further, in the above embodiment, since the photodiode 24 is also formed on the single semiconductor substrate 21 together with the laser diode 3, the intensity of the coherent light generated by the laser diode 31 can be accurately detected, and the detection result Based on this, the voltage applied to the laser diode 31 can be easily controlled.

<Effects> As explained above, according to the present invention, the protection diode is formed by introducing impurities of the second conductivity type into the semiconductor substrate of the first conductivity type, and the protection diode is placed in parallel with the laser diode. Because of this connection, even if static electricity is applied to the semiconductor laser device, the static electricity will flow through the protection diode, and a large voltage will not be applied to the laser diode, resulting in the effect that the laser diode will not be destroyed. can get.

[Brief explanation of drawings]

Fig. 1 is a plan view of an embodiment of the present invention, Fig. 2 is a perspective view of a conventional example, and Figs. 3(a) to (f) show the manufacturing process of the embodiment. Arrow sectional view. It is. 21... Semiconductor substrate, 22... Impurity region 25... Protective diode, 31... Laser diode. Patent Applicant: ROHM Co., Ltd. Representative, Patent Attorney Kiyoshi Kuwai - Figure 2 (el) (b) Figure 3 (C) (d) Figure 3

Claims (1)

[Claims] a protection diode including a semiconductor substrate of a first conductivity type and an impurity region of a second conductivity type formed in the semiconductor substrate; and a laser diode having the semiconductor substrate of the first conductivity type as one electrode. A semiconductor laser device, wherein the protection diode is rendered conductive by an undesired high voltage applied to both electrodes of the laser diode, thereby reducing the undesired high voltage.