JPH0126191B2 - - Google Patents

Abstract

PURPOSE:To easily adjust the sensitivity of a gate, by irradiating laser light or the like down upon the p2n2-junction of an SCR of p1n1p2n2 four-layer structure. CONSTITUTION:Ga is diffused in an n-type Si substrate to produce a p1-layer 3, an n1-layer 1 and a p2-layer 2. Both the sides of the substrate are coated with SiO2 films 5. An opening is made through the p2-layer 2 to produce an n2-layer. Recesses 10 are provided on the substrate and coated with glass 6. Al is evaporated on an emitter 4 and the gate 2 and an Ni-Ag electrode is evaporated on the other main face. When laser light of about 0.5 W is irradiated upon the p2n2 junction of the layers 4, 2 through the main face, the temperature of the Si rises and local irreversible thermal strain is caused between the SiO2 film 5 and the substrate. As a result, the lifetime of minority carriers of the p2n2-junction is shortened and the current amplification factor of an n1p2n2 transistor in a weak current range is reduced. If no heavy current is applied from the outside the gate current increases. The level of the gate current can be adjusted in a tolerably wide range by changing the area of irradiation, intensity of beam or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a semiconductor device, and in particular, a method for manufacturing a semiconductor device, particularly a P ₁ N ₁ P ₂ N ₂ device having no gate-cathode short circuit resistance.
The present invention relates to a manufacturing method for adjusting the gate sensitivity of a four-layer thyristor.

The operating principle of this type of thyristor is explained by the combination of P ₁ N ₁ P ₂ and N ₁ P ₂ N ₂ transistors, as is generally known. That is, the current gain of the P ₁ N ₁ P ₂ transistor is α ₁ ,
If the current gain of N ₁ P ₂ N ₂ transistor is α ₂ , then
The thyristor P ₁ N ₁ P ₂ becomes conductive when a current that satisfies α ₁ +α ₂ 1 flows inside. To obtain this, a gate current is applied from the outside to the base region P ₂ of the N ₁ P ₂ N ₂ transistor until α ₁ and α ₂ , which are dependent on the current, become large values, and α ₁ + α ₂
It should be set to 1.

The minimum gate current I _GT necessary to cause current to flow through the gate _P2 and bring the device into a conductive state may be required to have a value within a certain current range due to the circuit configuration that uses the device. be. In such a case, a gate current I _GT of 200 μA or more can be obtained relatively easily by adding a short-circuit resistor between the emitter and the base in the selective diffusion step during the manufacturing process. However, for a small gate current I _GT of less than 200 μA, it is extremely difficult to provide a shot resistance by diffusion. That is, in general, when a short-circuit resistor is provided between emitter N ₂ and base P ₂ , a region where the silicon oxide film remains is provided to prevent selective emitter diffusion into emitter N ₂ , which becomes an emitter. The shot resistance is made by diffusing the _N2 layer, and the shot resistance can be reduced to 300K by using the photoresist and the precision of the diffusion.
It is difficult to provide a resistance value larger than Ω with good reproducibility. In addition, when surface protection is performed between the emitter _N2 and the base with a silicon oxide film, the gate current is
I _GT is generally very small, and it has been difficult to increase this value with good reproducibility.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing a semiconductor device that can solve these difficulties and easily adjust the gate sensitivity I _GT required after the completion of the diffusion process without using a short pattern structure.

For this reason, the present invention provides an electrode metal during the semiconductor wafer manufacturing process to reduce the α ₂ of a P ₁ N ₁ P ₂ N ₂ four-layer thyristor, for example, by forming an emitter protected with an insulating material such as a silicon oxide film. N ₂ , base P ₂ P ₂ N ₂
It is characterized by controlling the gate trigger current by applying thermal strain between the silicon and silicon oxide films by applying a laser beam that can concentrate the energy density above the junction.

Next, an embodiment of the present invention will be described with reference to FIG.

Gallium was diffused from both sides into an N-type silicon substrate with a specific resistance of 30 to 40 Ω·cm and a thickness of 240 μ to a concentration of 6×10 ¹⁸ atoms/cc to a junction depth of ₅₀ μ.
Three layers are provided: Layer 3-N ₁ Layer 1-P ₂ Layer 2. After this,
The silicon substrate is oxidized in an oxidizing atmosphere to form a silicon oxide film 5 on both sides, and then the silicon oxide film in the part that should become the emitter _N2 layer 4 is removed using a conventional optical method, and phosphorus is removed from this part. ×10 ²¹
Diffuse to a concentration of atoms/cc and a depth of 20μ. Grooves 10 are dug in such a semiconductor wafer and P ₁ N ₁ and
Expose the N ₁ P ₂ junction and attach glass 6 to this part. Aluminum (Al) is vapor-deposited on the emitter 4 and gate 2 portions of the upper main surface of the semiconductor wafer thus produced, while Ni--Ag is vapor-deposited on the main surface. Further, the P ₂ N ₂ junction between the emitter 4 and the gate 2 layer of the semiconductor wafer thus formed is irradiated with a laser beam from the main surface at an intensity of about 0.5 ^W to 1 ^W. The semiconductor device obtained in this way has a gate current I _GT value of 10% compared to the case without irradiation with light.
It increased to about 2 times, that is, 20 to 50 μA.

In other words, a laser beam is applied to the P ₂ N ₂ junction under the oxide film.
By applying the beam, the temperature of the silicon increases, causing local thermal strain between the silicon and the silicon oxide film. This thermal strain shortens the life of minority carriers in the P ₂ N ₂ junction, reducing α ₂ in the low current region of the N ₁ P ₂ N ₂ transistor, so a larger current must be passed from the outside to reduce α ₁ Since +α ₂ does not become 1, the gate current I _GT ends up increasing. In this way, by applying a laser beam after providing an external electrode, irreversible distortion remains, and the gate current
The value of I _GT can be varied over a considerable range by changing the area to which the beam is applied, the strength of _the beam, etc.

[Brief explanation of drawings]

FIG. 1 is a sectional view illustrating a thyristor manufactured according to an embodiment of the manufacturing method of the present invention. In the figure, 1... silicon substrate, 2...
...Gate layer, 3...Cathode layer, 4...Emitter layer, 5...Silicon oxide film, 6...Glass, 7...
...Al gate electrode, 8...Al cathode electrode, 9...
...Ni-Ag cathode electrode, 10...Mesa groove, 11
. . . laser beam, 12 . . . thermally strained layer, respectively.

Claims (1)

[Claims] 1 A first electrode of one conductivity type with a main electrode connected to the main surface.
a second semiconductor layer of an opposite conductivity type, which is formed in contact with the side and bottom surfaces of the first semiconductor layer and has a main surface coplanar with the main surface of the first semiconductor layer; , a control electrode connected to the second semiconductor layer, a third semiconductor layer of one conductivity type formed in contact with the bottom surface of the second semiconductor layer, and a control electrode connected to the bottom surface of the third semiconductor layer. The fourth semiconductor layer of the opposite conductivity type formed in contact with the other main electrode formed on the bottom surface of the fourth semiconductor layer, and the main surfaces of the first and second semiconductor layers. These first
and an insulating film coated near the junction of the second semiconductor layer,
A gate current is generated by applying a thermal strain between the junction between the first and second semiconductor layers and the insulating film by irradiating the junction between the first and second semiconductor layers with a laser beam. A method of manufacturing a semiconductor device characterized by controlling the semiconductor device.