JPH0554269B2 - - Google Patents

Description

[Detailed description of the invention]

(Technical field) The present invention relates to GaAs-based shot diodes and
The present invention relates to a shot barrier semiconductor device such as a GaSa-based shot gate field effect transistor and a method for manufacturing the same. (Technical background) W, WSi, and the like are known as heat-resistant shot metals for GaAs-based n-type semiconductors. W shot metal formed by the sputtering method is known to have an n value close to 1 in diode characteristics and a low sheet resistance, but the barrier height is relatively low. Furthermore, the above n
The value increases dramatically and is therefore difficult to apply in devices that require activation annealing after shot metal formation. For example, as reported in Applied Physics Vol. 53, No. 1, p. 34, 1984, WSi shot metal is
Although it has relatively excellent heat resistance, that is, stability against high-temperature annealing, its sheet resistance is high. others
Shock metals such as TiW and TiWSi are also known, but they generally have the disadvantage of lacking heat resistance or having high sheet resistance. (Object of the Invention) An object of the present invention is to provide a GaAs-based shot semiconductor device that has good shot characteristics, excellent heat resistance, and relatively low sheet resistance. (Summary of the Invention) This invention provides an n-type GaAs semiconductor substrate with a thickness of 100 Å.
A shot barrier is obtained by forming the following Al film, forming a high melting point metal on top of it, and then annealing it at a high temperature. (Embodiment) FIG. 1 is a cross-sectional view of the structure of a shot gate type GaAsFET for explaining an embodiment of the present invention, which will be explained below along with the drawings. As shown in Figure 1, a semi-insulating GaAs substrate 1
After selectively forming the n-region 2, an Al film with a thickness of about 20 Å was deposited on it by sputtering, and then a W film with a thickness of about 1000 Å was deposited on it by sputtering. The Al film 3 and the W film 4 are formed on the n region 2 by etching the Al film and the W film so as to perform side etching using a metal having an ion blocking ability as a mask. Thereafter, n ⁺ regions 5 are selectively formed using the mask, and the mask is removed. After that, a SiO ₂ film (not shown) with a thickness of about 1200 Å was used as a protective film on the surface of the substrate 1 in an As pressure atmosphere.
After activation annealing at 900℃ for 15 minutes, this
Remove the _SiO2 film. By this annealing, Al diffuses into the W film 4, and the Al film 3 changes into a layer containing Al in W. Next, ohmic electrodes 6a, 6b are placed on the n ⁺ region.
By sequentially forming the SiO ₂ film 7 and the wiring materials 8a and 8b, a shot gate type as shown in FIG.
Obtain GaAsFET. In addition, in Figure 1, in W
The layer 3 containing Al and the W film 4 serve as a gate electrode, and the ohmic electrodes 6a and 6b serve as source and drain electrodes. Next, its characteristics will be explained using FIG. 2. FIG. 2 is a diagram showing the current-voltage (I-V) characteristics at the shot junction after annealing of the shot semiconductor device according to the present invention; in this example,
The area of the junction of the Schottky semiconductor device is 8×10 ^-5
cm ² , the Al film thickness is 20 Å, and the W film thickness is 1000 Å.
Å, and the n-layer is 60keV at a dose of 1.8×10 ¹² cm ^-2
It was formed by Si ion implantation. This second
As is clear from the figure, even after annealing at 900°C for 15 minutes, the n value is 1.02 and the barrier height φ _B is 0.83.
It was found that very good shot characteristics were obtained, and the sheet resistance was relatively small at about 16 μΩcm. The table shows the shot characteristics of the AlW metal according to the present invention and conventionally used metals before and after annealing, and shows the values of n value and barrier height φ _B.

[Table] Note that *a is the experimental data of the present inventors, *
b is a quotation from the above-mentioned document. As can be seen from this table, when Al is formed to a thickness of 20 Å and W is formed to a thickness of 1000 Å on top of it, the n value is stable near 1 before and after annealing, compared to the case of a shot barrier made of other metals. It can be seen that the barrier height _φB is also high and stable, and better shot characteristics than other metals can be obtained. However, when the Al thickness in the AlW shot electrode is increased to 120 Å, the n value and the barrier height φ _B value are adversely deteriorated compared to when the Al thickness is about 20 Å, resulting in poor shot properties. Become. This is because Al is not completely diffused into the W film and a thin film of Al remains. Further, even if heat treatment is performed at a fairly low temperature of about 350° C., the metal layer may partially condense or peel off from the substrate surface. From the above, the thickness of the Al metal film to be formed is
It is formed almost uniformly on the surface of the GaAs-based substrate, and
A thickness of 100 Å or less is effective to prevent Al from being completely diffused into the W film and leaving a thin Al film. (Effects of the Invention) As explained above, this invention has an n-type GaAs
A shot barrier is obtained by selectively forming an Al film with a thickness of 100 Å or less on a system substrate, and then sequentially forming a high-melting point metal film on top of that, followed by high-temperature annealing. Therefore, it is possible to obtain a shot barrier semiconductor device with good shot characteristics such as n value, barrier height, sheet resistance, etc. even after annealing at, for example, 800° C. or higher.

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining one embodiment of the present invention.
FIG. 2 is a structural cross-sectional view of a GaAs FET, and FIG.
It is a figure showing an example of a characteristic. 1...Semi-insulating GaAs substrate, 2...n region, 3
...Al film (layer containing Al in W), 4...
W film, 5...n ⁺ region, 6a, 6b... source and drain electrodes, 7... SiO ₂ film, 8a, 8b...
...Wiring material.

Claims (1)

[Claims] 1. A method for manufacturing a shot semiconductor device using tungsten as the main material of a shot electrode, comprising: forming an n-type region on a semi-insulating GaAs substrate; forming a tungsten film on the aluminum film; etching the aluminum film and the tungsten film to stack the aluminum film and the tungsten film on the n-type region; a step of forming a shot-type electrode, and annealing at a temperature of 750° C. or higher to diffuse the aluminum film into the tungsten film, forming an upper layer of the shot-type electrode as a tanksten layer and a lower layer as an alloy layer of tungsten and aluminum. 1. A method for manufacturing a short-shot semiconductor device, comprising the steps of: 2. The method of manufacturing a shot-lock semiconductor device according to claim 1, wherein the semiconductor device is a shot-gate field effect transistor.