JPH0744291B2 - Optically coupled semiconductor relay device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor relay device, and more particularly, to an AC / DC converter including a light emitting section that emits an optical signal and a light receiving section that performs a switching operation based on the optical signal. The present invention relates to an optical coupling type semiconductor relay device for both direct current and DC.

(Prior Art) An electromagnetic relay device has been mainly used as a device for controlling an output side circuit electrically insulated from the input side circuit based on a signal given to the input side circuit. . However, since the electromagnetic relay device has a mechanically movable part, the device itself is large, and it is difficult to downsize a device using the device. In addition, the electromagnetic relay device has a drawback that mechanically movable parts are easily fatigued and have a short life.

In recent years, instead of such an electromagnetic relay device, SSR (Solid State Rela
The semiconductor relay device called y) is becoming popular. However, bipolar transistors, thyristors, or
A semiconductor relay device using a MOS field effect transistor (MOSFET) cannot be used for both AC and DC.

This point will be briefly explained using MOSFET as an example.
The MOSFET is normally used with the source region and the substrate region including a part of the channel forming region at the same potential,
Both the source electrode and the backside electrode of the substrate are grounded.

In such a configuration, since the source region and the channel forming region are substantially short-circuited, when an AC voltage is applied between the source region and the drain region, the PN junction between the drain region and the channel forming region is normally formed. In the half cycle of the AC waveform biased in the direction, the current flows regardless of the gate voltage. That is, the MOSFET cannot be used as a switching element for both AC and DC.

In order to solve these problems, a semiconductor relay device capable of supplying AC / DC by using two MOS field effect transistors (MOS FETs) has been developed. This is an optical coupling type semiconductor relay device composed of a light emitting section composed of a light emitting diode and a light receiving section composed of a photodiode and a MOS FET. FIG. 7 shows the equivalent circuit. Photodiode arrays 41 and 42 in the light receiving section receive the optical signal emitted from the light emitting diode 38 in the light emitting section, perform photoelectric conversion, and drive the MOS FETs 39 and 40 by the obtained electromotive force. The source electrodes of the MOS FETs 39 and 40 are connected to each other, and the electromotive forces of the photodiode arrays 41 and 42 are applied between the gate electrode and the source electrode of the MOS FETs 39 and 40, respectively.

At this time, in either one of the MOSFETs, the PN junction between the source region and the channel forming region is reverse-biased, and the AC signal can be switched by the gate voltage. In this way, the current flowing between the drains of the MOS FETs 39 and 40 is controlled.

In the above optical coupling type semiconductor relay device, one light emitting diode, two photodiode arrays, and two MOS FEs are used.
A total of 5 elements of T are required. As a method of further downsizing the semiconductor relay device by reducing the number of elements used and reducing the manufacturing cost, a method of stacking a photodiode array on a vertical MOS FET via an insulating film has been proposed. If this method is adopted, since the MOS FET and the photodiode are integrated, an optical coupling type semiconductor relay device can be realized with a total of three elements.

(Problems to be Solved by the Invention) However, in the above method, it is necessary to provide wiring between two vertical MOS FETs in which photodiode arrays are stacked. Therefore, the manufacturing cost is still high and there is a limit to miniaturization.

The present invention solves the above-mentioned conventional problems, and an object of the present invention is to further reduce the size and reduce the manufacturing cost of an AC / DC device by configuring the light receiving portion with one element. An object is to provide a shared optical coupling type semiconductor relay device.

(Means for Solving the Problem) An optically coupled semiconductor relay device according to the present invention is provided with a light emitting portion having a light emitting element and a light receiving portion optically coupled to the light emitting portion. The light receiving unit is a first set of switches each formed on a single semiconductor substrate, the plurality of vertical MOSFETs sharing the substrate as a drain and short-circuiting a source region and a channel forming region. A transistor, a second set of switch transistors composed of a plurality of vertical MOSFETs sharing the substrate as a drain and having a source region and a channel formation region short-circuited, and formed above the first set of switch transistors with an insulating film interposed therebetween. The first photoelectric conversion element connected between the gate electrode and the source electrode of the switch transistor of the first set and the switch transistor of the second set are disconnected from above. A second photoelectric conversion element formed via an edge film and connected between the gate electrode and the source electrode of the second set of switch transistors, and the drain of the first set of switch transistors and the second set of photoelectric conversion elements. The drain of the switch transistor is commonly connected to the substrate, and thereby the above object is achieved.

A light emitting diode, for example, is used as the light emitting element forming the light emitting unit. A light emitting diode is a diode that emits visible light or near visible light when a voltage is applied. On the other hand, as the photoelectric conversion element that constitutes the light receiving section,
For example, a photodiode is used. A photodiode is a diode that generates photocurrent or photoelectromotive force when irradiated with light of a predetermined wavelength. The above-mentioned light emitting diode and photodiode are selected so as to have a wavelength band in which they are optically coupled.

An equivalent circuit of the optically coupled semiconductor relay device of the present invention is implemented as shown in FIG. 6, for example. The light emitting diode 33, which constitutes the light emitting section, converts the supplied input electric signal into an optical signal. The optical signal emitted from the light emitting diode 33 reaches the photodiode arrays 34 and 35 forming the light receiving section. In FIG. 6, one for one set of photodiode arrays 34, 35
Although one light emitting diode 33 is provided, one light emitting diode may be used by facing each of the photodiode arrays 34 and 35.

The photodiode arrays 34 and 35 convert the received optical signal into an electric signal. The electric signal is given in the form of electromotive force and drives the vertical MOS FETs 36 and 37. Vertical MOS FET 36,37
Have their drain electrodes connected to each other, and the electromotive forces of the photodiode arrays 34 and 35 are applied between the gate and source electrodes of the vertical MOS FETs 36 and 37, respectively. In this way, the current flowing between the sources of the vertical MOS FETs 36, 37 is controlled.

(Operation) In the optically coupled semiconductor relay device of the present invention, two sets of switch transistors to which the drains of the switch transistors of each set are connected, and a photoelectric conversion element for controlling each switch transistor by photocurrent output, Since the light receiving portion is formed by sequentially stacking on the substrate, the two sets of switch transistors and photoelectric conversion elements are integrated.
As a result, the device can be downsized, the number of parts can be reduced, the manufacturing process can be simplified, and the manufacturing cost can be reduced. Moreover, since the two sets of switch transistors are connected in series, even if the polarity of the signal to be switched is reversed, switching is performed by either one, and AC and DC can be shared.

(Examples) Examples of the present invention will be described below.

FIG. 2 is a sectional view showing the structure of an optically coupled semiconductor relay device 1 according to an embodiment of the present invention. A light emitting portion 4 and a light receiving portion 5 are arranged near the respective tip portions of the lead frames 2 and 3 so as to face each other. A light emitting diode is used as a light emitting element forming the light emitting unit 4. A resin 6 capable of transmitting the optical signal emitted from the light emitting unit 4 is disposed between the light emitting unit 4 and the light receiving unit 5. The entire area near the tips of the lead frames 2 and 3 is made of resin 7
It is covered with and prevents malfunction due to light from the outside.

FIG. 3 is a schematic view of the surface of the light receiving unit 5 as viewed from above. A photodiode array was used as the photoelectric conversion element. Vertical MO with a photodiode array stacked through an insulating film
The S FETs 8 and 9 are formed on the same semiconductor substrate 10. These vertical MOS FETs 8 and 9 are connected to each other by sharing the semiconductor substrate 10 as a drain. Vertical MOS
Guard rings 11 and 12 are formed around the FETs 8 and 9 to increase the pressure resistance.

FIG. 1 is a vertical type of FIG. 3 in which photodiode arrays are stacked.
It is a partial perspective view of MOS FET 8 or 9. A method of manufacturing such vertical MOS FETs 8 and 9 will be described. An N-Si epitaxial layer 14 having a thickness of 30 μm was grown on the N ⁺ -Si substrate 13, and boron was partially ion-implanted using a resist mask to form an island-shaped P region 15. Next, island-shaped P
An N ⁺ region 16 was formed in the center of the region 15 by annularly ion-implanting phosphorus using a resist mask. After the gate insulating film 17 was formed by thermally oxidizing the entire surface, an N ⁺ -Si polycrystalline film 18 to be a gate electrode was formed on the entire surface.

Then, etching by normal lithography is performed,
As shown in FIG. 1, the gate insulating film 17 and the N ⁺ -Si polycrystalline film 18 were left only outside the annular N ⁺ region 16. On the entire surface
After the SiO ₂ film 19 is formed, a boron-doped Si non-single-crystal film is formed and irradiated with an argon laser to form P-.
A Si single crystal film was used. Instead of the argon laser, another laser that emits a laser beam having a wavelength absorbed by the Si non-single crystal film may be used. Alternatively, instead of irradiating the laser beam, the Si non-single-crystal film is irradiated with an electron beam or is heated by using a lamp or a heater.
It can also be a Si single crystal film.

The P-Si single crystal film was etched to leave only the region where the photodiode was formed. An N ⁺ region 21 was formed by ion-implanting arsenic into the remaining island-shaped P-Si single crystal region 20 using a resist mask. A P ⁺ region 22 was formed by ion-implanting boron into the island-shaped P-Si single crystal region 20 other than the N ⁺ region 21 using a resist mask. After forming the SiO ₂ film 23 on the entire surface, the vertical type
SiO ₂ films 19 and 23 on the source and gate contact regions (not shown) of the MOS FET, and on the N ⁺ and P ⁺ contact regions of the photodiode.
The SiO ₂ film 23 was opened by etching to expose the Si surface.

Then, after forming an Al film on the entire surface, it was etched into a predetermined pattern to form Al wirings 24 and 25. Although not shown in FIG. 1, Al wirings 24 serving as source electrodes are connected to each other and further connected to an Al wiring 25 formed on the photodiode at one end of the photodiode array. Further, the N ⁺ -Si polycrystalline film 18 serving as the gate electrode is connected to the photodiode at the other end of the photodiode array through the gate contact region. Therefore, the equivalent circuit of the optically coupled semiconductor relay device of this embodiment is represented as shown in FIG. Finally, as a surface protection film, Si
After forming a ₃ N ₄ film (not shown), etching was performed so as to expose only the pad portion that will be a contact point with the external wiring.

FIG. 4 is a sectional view near the guard ring. The guard ring 26 is a P region and was formed at the same time when the P region 15 was formed. Further, the SiO ₂ film 19, 23 on the guard ring when forming the SiO ₂ film 19, 23 described above, and SiO ₂ film 19, 23
The upper Al electrode 27 was formed at the same time when the above Al electrode 24 was formed. As described above, in this embodiment, two switch transistors connected in series and a photoelectric conversion element for controlling each switch transistor by the photocurrent output are sequentially laminated on the substrate to form the light receiving portion, so that two sets of two are formed. Since the switch transistor and the photoelectric conversion element are integrated, the number of parts can be reduced and the manufacturing process can be simplified.

Moreover, since the two sets of switch transistors are connected in series, even if the polarity of the signal to be switched is reversed, switching is performed by either one, and AC and DC can be shared. With only one set of switch transistors, when a positive voltage is applied to the source side with respect to the n-type drain, the positive voltage is also applied to the island-shaped P region. This is because the N ⁺ region 16 and the P region 15 which are sources are short-circuited by the Al electrode 24 as shown in FIG. Therefore, the forward current of the diode flows through the switch transistor regardless of the gate voltage. On the other hand, in the present embodiment, since the drains of the two sets of switch transistors are connected to each other, even if an AC signal is applied to the sources of the two switch transistors, one of the set switch transistors must have its drain On the other hand, the source side has a negative potential. Therefore, in this switch transistor, a negative voltage is also applied to the island-shaped P region on the source side,
It becomes possible to control by the gate voltage.

In this embodiment, the photodiode is formed by ion-implanting arsenic into the P-Si single crystal film, but conversely, the photodiode may be formed by ion-implanting boron into the N-Si single crystal film.

A vertical MOS FE having a stacked photodiode array used in an optical coupling type semiconductor relay device according to another embodiment of the present invention.
A partial perspective view of T is shown in FIG. The steps up to the step of forming the SiO ₂ film 19 on the entire surface are the same as in the above-described embodiment.

Then, after forming a nickel-chromium layer on the entire surface of the SiO ₂ film 19, patterning was performed so as to leave only a region for forming a photodiode, thereby forming an island-shaped lower layer electrode 28. A P-Si amorphous film 29 is formed on the entire surface and patterned so that a part of the island-shaped lower layer electrode 28 is exposed.
An amorphous film 30 was formed on the entire surface and patterned so as to cover the upper surface and side surfaces of the island-shaped P-Si amorphous film 29 and expose a part of the lower electrode 28.

Then, an indium oxide film 31 containing tin is formed on the entire surface as an upper layer transparent electrode to cover the upper surface and the side surface of the island-shaped N-Si amorphous film 30, and the lower electrode 28 and the N of the adjacent photodiode. It was patterned so as to connect with the -Si amorphous film 30.

Finally, the SiO ₂ film 19 on the source contact region and gate contact region (not shown) of the vertical MOS FET was opened by etching to expose the Si surface. And Al on the whole surface
After forming the film, the Al wiring 32 was formed by etching in a predetermined pattern. Although not shown in FIG. 5, Al wirings 32 serving as source electrodes are connected to each other and further connected to an indium oxide film 31 containing tin formed on the photodiode at one end of the photodiode array. Further, the N ⁺ -Si polycrystalline film 18 serving as the gate electrode is connected to the photodiode at the other end of the photodiode array through the gate contact region. Therefore, the equivalent circuit of the optically coupled semiconductor relay of this embodiment is also the sixth circuit.
It is represented as shown.

The structure in the vicinity of the guard ring is the same as that of the above-described embodiment except that the SiO ₂ film 23 does not exist.

In this embodiment, the N-Si amorphous film is formed on the P-Si amorphous film, but conversely, the P-Si amorphous film may be formed on the N-Si amorphous film. . Alternatively, P-i-N structure or N-i-P
A structure can also be adopted.

(Effects of the Invention) As described above, according to the optically coupled semiconductor relay device of the present invention, the light receiving unit having two sets of switch transistors connected in series and a photoelectric conversion element for controlling each switch transistor by photocurrent output. Has a structure in which the switch transistor and the photoelectric conversion element are sequentially laminated on the substrate, so that the number of parts is small, the manufacturing process is simple, and the AC-DC semiconductor relay capable of sharing AC and DC is provided. Obtainable. Such a semiconductor relay device is smaller than the conventional semiconductor relay device, and the manufacturing cost is reduced. Therefore, the optically coupled semiconductor relay device of the present invention is widely applied in the field where the conventional electromagnetic relay device was used.

[Brief description of drawings]

FIG. 1 is a vertical MO in which a photodiode array is laminated in an optical coupling type semiconductor relay device which is an embodiment of the present invention.
FIG. 2 is a perspective view showing the main part of the S FET 8 or 9, FIG. 2 is a cross-sectional view of the optically coupled semiconductor relay device, FIG. 3 is a schematic top view of the light receiving portion 5 shown in FIG. 2, and FIG. FIG. 3 is a cross-sectional view showing the vicinity of the guard rings 11 and 12 shown in FIG. 3, and FIG. 5 is a perspective view showing a main part of a MOS FET which constitutes a light receiving portion of an optical coupling type semiconductor relay according to another embodiment of the present invention. FIG. 6 is an equivalent circuit diagram of an optically coupled semiconductor relay device according to an embodiment of the present invention, and FIG. 7 is an equivalent circuit diagram of a conventional optically coupled semiconductor relay device. 1 ... Optically coupled semiconductor relay device for both AC and DC, 4 ...
… Light emitting part, 5 …… Light receiving part, 8, 9 …… Vertical MOS FET with stacked photodiode arrays, 10 …… Semiconductor substrate, 13 …… N ⁺ −Si
Substrate, 15 …… P region, 16,21 …… N ⁺ region, 17 …… Gate insulating film, 18 …… N ⁺ −Si polycrystalline film, 19,23 …… SiO ₂ film, 20 …… P−
Si single crystal region, 22 …… P ⁺ region, 29 …… P-Si amorphous film, 30
…… N-Si amorphous film, 34, 35, 41, 42 …… Photodiode array, 36, 37 …… Vertical MOS FET, 39, 40 …… MOS FET.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tsukasa Doi 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Within Sharp Corporation (72) Minoru Yoshioka 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Incorporated (72) Inventor Masayoshi Kiba 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (56) Reference JP-A-63-51681 (JP, A) JP-A-1-235282 (JP , A)

Claims (1)

[Claims] 1. An optical coupling type semiconductor relay device comprising a light emitting portion having a light emitting element and a light receiving portion optically coupled to the light emitting portion, each light receiving portion being on one semiconductor substrate. And a source region and a channel formed by sharing the substrate as a drain, the first set of switch transistors consisting of a plurality of vertical MOSFETs having a short-circuited source region and channel formation region, and sharing the substrate as a drain. Multiple vertical MOSFs with shorted areas
The second set of switch transistors consisting of ET and the first set
A first photoelectric conversion element that is formed above the pair of switch transistors via an insulating film and is connected between the gate electrode and the source electrode of the first pair of switch transistors, and is insulated above the second pair of switch transistors. A second photoelectric conversion element formed through a film and connected between the gate electrode and the source electrode of the second set of switch transistors, and the drain of the first set of switch transistors and the second set of the second set of switch transistors. An optical coupling type semiconductor relay device in which a drain of a switch transistor is commonly connected to the substrate.