JPH02202065A - Manufacturing method of static induction transistor - Google Patents

Abstract

PURPOSE:To prevent the dispersion of a transistor characteristics and to improve it in switching speed by a method wherein the doping required for the formation of a gate and a source electrode section is executed through a laser doping method, and the epitaxial growth made for the formation of a source is performed in an environment of low temperature. CONSTITUTION:The doping required for the formation of a gate 204 and a source electrode section 205 is executed through a laser doping method, and the epitaxial growth made for the formation of a source 205 is performed in an environment of low temperature. Therefore, a reaction is prevented from taking place outside a required range, and the shape of impurity of a channel section which forms a gate can be uniformly formed just conforming to the shape of a mask 203, and the channel section can be made short, so that the channel section can be stably made small in resistance as in the same as designed. The impurity is formed very sharp in form, so that a depletion layer can be reduced in capacity. By this setup, a transistor of this design can be protected against dispersion in characteristics and improved in switching speed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing a static induction transistor,
In particular, the present invention relates to a method for manufacturing a stable static induction transistor with a low gate channel resistance value and little variation in characteristics.

[Prior Art] Conventionally, static induction transistors have been manufactured through a process as shown in FIG.

For example, to manufacture an N-type static induction transistor, first a layer is formed by epitaxial growth or the like with an N-type semiconductor layer 302 having a high impurity concentration for forming a drain electrode as shown in FIG. 3 (a). As shown in (b), on the N-type semiconductor 301 with a low impurity concentration, masking is performed by creating a void using photolithography technology in a pattern shape that matches the shape of the gate to be formed (303), and the gate is formed from the void. A group 3 element such as boron is doped by thermal diffusion or ion implantation to form (
304), after removing the masking material, N was removed in 5iC1 gas at about 1100°C as shown in (c).
A low impurity concentration layer of the mold is epitaxially grown (305
), a group 5 element such as phosphorus is diffused thereon to form a highly impurity layer source (306), and finally, as shown in (e), after etching the gate part, pure aluminum or the like is metallized. Each electrode is formed using the same method.

In FIG. 3(e), 307 is a source electrode, 308 is a gate electrode, and 309 is a train electrode.

[Problems to be Solved by the Invention] However, in the above-mentioned conventional manufacturing method, the shape of the impurity in the channel portion constituting the gate follows the shape of the mask because heat treatment at a high temperature of approximately 1100°C is not required for doping the impurity. 304 in Figure 3(b)
As shown by the curve 300 in FIG. 4, the required shape is not completed and the boundary with the N-type low impurity layer, which is a carrier path, collapses and widens, resulting in an increase in channel resistance and variations in characteristics. There was a problem.

The present invention has focused on the above-mentioned conventional problems, and an object of the present invention is to provide a method for manufacturing a static induction transistor in which the shape of the impurity in the channel portion constituting the gate can be formed in accordance with the shape of a mask. It is said that

[Means for Solving the Problems] In order to achieve the above object, in the method for manufacturing a static induction transistor according to the present invention, a material that is inert to the material of the substrate is formed on a substrate that is to be a drain made of a semiconductor. An electrostatic type method in which a mask is made of a suitable material and has voids in the desired pattern, and impurities are injected into the voids of the mask to form a gate, and after the mask is removed, a source is formed by epitaxial growth. In a method for manufacturing a transistor, doping for forming a gate is performed by laser doping at room temperature, and epitaxial growth for forming a source is performed in a low-temperature environment to manufacture a static induction transistor.

[Function] According to the above manufacturing method, the doping for forming the gate and source electrode portions is performed by laser doping, and the epitaxial growth for forming the source is performed in a low temperature environment, so that the reaction progresses beyond the required range. The shape of the impurity in the channel part constituting the gate can be formed in the same way as the mask shape, and the channel can therefore be shortened, making it possible to stably form the resistance value as small as the design. It is possible to manufacture static induction type transistors with various characteristics without any variation in the characteristics. Furthermore, since the shape of the impurity is finished steeply, the depletion layer capacitance decreases, making it impossible to improve the switching speed.

[Embodiment 2] Hereinafter, embodiments of the static induction transistor according to the present invention will be described in detail with reference to the drawings. An embodiment of the manufacturing process of a static induction transistor according to the present invention will be explained with reference to FIG.

For example, in order to manufacture an N-type static induction transistor, first, a layer is formed with an N-type semiconductor layer 202 having a high impurity concentration for forming a drain electrode as shown in FIG. As shown in (b) on the N-type semiconductor 201 with a low impurity concentration, voids are created using photolithography technology in a pattern shape that matches the shape of the gate to be formed, and masking is performed with aluminum or polycrystalline silicon. (203), by irradiating a laser beam in an atmosphere of a dopant gas containing a group 3 element such as boron so as to form a gate according to the gap, and doping by localized heat from the laser (
204), after dissolving and removing the masking material with an etching agent, monosilane gas is heated at about 600 to 700°
An N-type low impurity concentration layer is epitaxially grown in a C atmosphere (205), and then laser doping is performed again in an osphine gas atmosphere containing a group 5 element such as phosphorus to form a source of a high impurity layer. Finally, as shown in (e), after etching the gate portion, pure aluminum or the like is metallized to form each electrode.

In FIG. 3(e), 207 is a source electrode, and 208 is a gate 209, which is a drain electrode.

The shape of the P-type layer of the gate electrode part according to the present invention is as shown by curve 200 in FIG.
The boundary with the mold layer is clearly formed without becoming unclear.

Next, the method of laser doping will be explained with reference to FIG.

FIG. 2 is a schematic diagram of a laser doping apparatus for an electrostatic induction transistor according to the present invention, in which internal gas is exhausted by an exhaust device 7 from a masked substrate for forming a gate. It is fixed in a vacuum chamber 4. A window 6 made of quartz is provided on the masked front side of a substrate 5 fixed in a vacuum chamber 4, so that a laser beam 8 from a laser device 1 can be directed to the substrate 5 through the laser beam. The vacuum chamber 4 has two ports, and exhaust gas 9 is discharged from one port by an exhaust device 7, and low-pressure reaction gas is injected from the other port. Also,
The vacuum chamber 4 is not heated and is maintained at room temperature.

Next, the internal workings of the vacuum chamber 4 will be explained.

The vacuum chamber 4 is evacuated by an exhaust device 7, and a dopant gas containing group 3 elements, for example boron, is diluted with hydrogen gas and injected at low pressure. The gas is in contact with the surface.

When the laser device 1 irradiates the laser beam 8 perpendicularly to the surface of the substrate 5, which is masked with voids in contact with the surface of the dopant gas, the voids in the masking on the surface of the substrate 5 are instantaneously exposed to the laser beam. The P-type crystal is formed in the designed shape because the boron is melted locally by the energy of , and the boron melts into the crystal structure of the molten base silicon and does not diffuse laterally.

For example, by irradiating 1.6 J/cm' shots of Nitrogen with an excimer laser in an atmosphere with a gas pressure of 50 torr, a gate portion with a concentration of 3 x 10''/cm' and a depth of 0.4 μm is formed.

To form a crystal with a high impurity concentration for the source, scan a laser in a gas containing a group 5 element, such as osphine gas containing phosphorus, instead of a gas containing a group 3 element as described above. This allows processing to be performed using the same vacuum chamber 4.

In addition, the gas pressure and laser device may be selected according to the desired diffusion depth and concentration. [Effects of the Invention] As explained above, according to the method of manufacturing a static induction transistor based on the present invention, , doping for forming the gate and source electrode portions is performed by laser doping,
Since the epitaxial growth for forming the source is performed in a low-temperature environment, the reaction does not proceed beyond the required range, and the shape of the impurity in the channel part that makes up the gate follows the masking shape, and the depth is also shallow. -The channel distance can be shortened, so the resistance value can be formed stably to a small value as designed, and the characteristics will not vary. Can be done. Furthermore, since the shape of the impurity is finished steeply, the depletion layer capacitance is reduced and the switching speed can be improved.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the manufacturing process of a static induction type transistor based on the present invention. FIG. 2 is a schematic diagram of a laser doping apparatus based on the present invention. FIG. 3 is an explanatory diagram of a conventional static induction transistor manufacturing process. FIG. 4 is a curve diagram for explaining the difference in impurity concentration and penetration depth around the gate between the manufacturing method according to the present invention and the conventional manufacturing method. 1...Laser device 2...Reactive gas 4...Vacuum chamber 5...Base 6...Quartz window 7...・Exhaust device 8...Laser 9...Exhaust gas 200.300...Impurity concentration/penetration depth characteristic curve 201.301...Base 202 forming the drain side
．． 302...Drain electrode part 203.303...Masking 204.304...Gate 205.305...Source 206.306...Source electrode part 207.307...Electricity 1iii (source) 208.
308...Electrode (gate) 209.309...Electrode (drain) Applicant: Komatsu Ltd. Figure 2 (b) (C) Figure 1 Figure 3

Claims (1)

[Claims] A mask made of a material inert to the material of the substrate and having voids in the desired pattern is provided on a substrate which is to be a drain made of a semiconductor, and impurities are doped through the voids of the mask. In a method for manufacturing a static induction transistor in which a gate is formed and a source is formed by epitaxial growth after removing a mask, doping for forming the gate is performed by laser doping, and epitaxial growth for forming the source is performed in a low temperature environment. 1. A method of manufacturing a static induction transistor, characterized by comprising: