JPS6376380A - Semiconductor device - Google Patents

Abstract

PURPOSE:To achieve speeding up of mobility of electrons by forming hetero junction interfaces of a channel region so that they may have a plurality of parallel and stripe forms each other and producing electron gases in the same manner as one dimensional quantization that are separated one another among stripes. CONSTITUTION:This device permits an n-type AlxGa1-xAs layer 2 and a non- doping i-type GaAs layer 3 to make an epitaxial growth on a semi-insulated GaAs substrate 1. A flat plane where a stripe-like pattern of the i-type GaAs layer 3 is visible between SiO2 films 5 is formed to make the GaAs layer 3 visible, in which a source and drain contact region is formed by an etching treatment. Si is ion-implanted into this region to form an n-type source and drain contact region 4 after carrying out an activated heat-treatment, thereby arranging a source and drain electrodes 6 composed of, for instance, AuGe/Au as well as a gate electrode 7 composed of, for instance, Al. As a result, electron gases 3e are formed in the vicinity of respective hetero junction interfaces that are patternized in the form of stripes by electrons moved from the n-type AlGaAs layer 2 to the i-type GaAs layer 3. Thus, this approach helps increase mobility of the electrons and improve speeding up of mobility.

Description

[Detailed Description of the Invention] [Summary] The present invention relates to a field effect transistor that uses an electron gas as a channel by spatially separated doping and interface quantization, and in which the heterojunction interface in the channel region is formed into a plurality of mutually parallel stripes. By molding and producing an electron gas that corresponds to one-dimensional quantization separated between stripes, the mobility of electrons is increased and the speed of semiconductor devices is increased.

[Industrial application field]

The present invention relates to a semiconductor device, and more particularly to a semiconductor device in which a channel is a high-mobility electron gas based on one-dimensional doping and interface quantization.

The conventionally known high electron mobility field effect transistor (
HEMT) uses a two-dimensional quantized electron gas as a channel, but there is a desire to realize a semiconductor device with even higher electron mobility in which the two-dimensional quantized state approaches the one-dimensional quantized state.

[Conventional technology]

A schematic side sectional view of an example of a conventional HEMT is shown in FIG.

In this conventional example, a semi-insulating gallium arsenide (GaAs) substrate 2
1, there is a non-doped i-type GaAs layer 22 on top of the undoped i-type GaAs layer 22, and a layer 22 having a smaller electron affinity than that, for example, a concentration of 2×10111CI+1.
An n-type aluminum gallium arsenide (AIXGal-XMS) layer 23 doped with donor impurities to the extent of an arch, and an n-type GaA layer 23 doped with donor impurities to the same extent or more.
A two-dimensional electron gas 22e is formed near the heterojunction interface by electrons transferred from the n-type AlGaAs1J23 to the i-type GaAs layer 22.

Source and drain electrodes 26 are provided on the n-type GaAs layer 24 of this semiconductor substrate using, for example, gold germanium/gold (AuGe/Au), and the n-type AlGaAs electron supply layer 23
A gate electrode 27 is provided thereon using, for example, titanium/platinum/gold (Ti/Pt/Au) or aluminum (AI). Note that 26A is an alloyed region formed between the source/drain electrode 26 and the semiconductor substrate.

Transistor operation is performed by controlling the areal density of the two-dimensional electron gas 22e in the Schottky depletion layer formed by the gate electrode 27, but this two-dimensional electron gas 22e has almost no reduction in mobility due to impurity scattering and, for example, when lattice scattering is reduced. The highest mobility is obtained at low temperatures below 77°C. In this case, the electron mobility is usually 1 to 10×10'cm"/V
, s, for example, about 6 x 10'cm"/V, s, which is much lower than the electron mobility in a GaAs single crystal doped with impurities, which is less than I x 10'cm"/V, s. A high value has been obtained.

[Problem that the invention seeks to solve]

As mentioned above, HEMT uses two-dimensional electron gas as a channel.
has the highest carrier mobility among conventional field effect transistors, and together with shortening the gate length, it has become a typical example of increasing the speed of semiconductor devices.

However, there are limits to miniaturization of patterns and shortening of gate length, and there is a need to concretely realize field-effect transistors that further increase carrier mobility through one-dimensional quantization of electrons or a similar state. There is.

[Means for solving problems]

The problem is that the non-doped first semiconductor layer and the first
The channel region has a heterojunction with a second semiconductor layer that has a smaller electron affinity than the second semiconductor layer and contains donor impurities, and the heterojunction interface of the channel region is formed into a plurality of mutually parallel stripes, and there are gaps between the stripes. By the semiconductor device according to the present invention, an electron gas that is separated and quantized at least in a direction perpendicular to the interface is generated near the interface, and the electron gas is controlled by a gate electrode disposed intersecting the stripe. resolved.

[For production]

According to the present invention, the channel region of the spatially separated doped heterojunction interface is formed into a plurality of mutually parallel narrow stripes, and the direction perpendicular to the interface is similar to the conventional two-dimensional electron gas. The electron gas is quantized and separated between stripes in the stripe width direction, and although it is not quantized, it generates an electron gas with a low scattering effect similar to one-dimensional quantization, and its electron mobility is compared to that of a conventional two-dimensional electron gas. make it higher.

In order to achieve one-dimensional quantization, the width direction of the stripe must be aligned with the Doe-Brog wavelength of electrons (approximately 30 nm in GaAs).
Although it is difficult to achieve this by pattern formation using lithography etching methods, etc., it is necessary to reduce the scattering effect by about 10 times or less than the two-dimensional electron gas and increase the mobility. It is possible.

Note that even if variations occur in this dimension, the characteristics will not vary significantly as in the case of shortening the gate length.

Furthermore, since a plurality of stripes are connected in parallel, it is possible not only to simply increase the current but also to average out variations.

〔Example〕

The present invention will be specifically explained below using examples.

FIG. 1 is a schematic diagram of an embodiment of the present invention.
A Y' cross-sectional view is shown, and FIG. 2 (11 to (3)) is a Y-Y'' cross-sectional view during the manufacturing process of this embodiment.

In the figure, 1 is a semi-insulating GaAs substrate, 2 is an n-type A1x Gat-, As (x=0.3
) layer, 3 is a non-doped i-type GaAs layer, 4 is, for example, S
n-type source/drain contact region implanted with T, 5
6 is a protective insulating film made of, for example, Sing, and 6 is made of, for example, Au.
Source and drain electrodes made of Ge/Au; 6A is an alloyed region formed between the source and drain electrode 6 and the semiconductor substrate; 7 is a gate electrode made of, for example, A1;
Electrons transferred from the n-type AtGaAs layer 2 to the i-type GaAs layer 3 form an electron gas 3e in the vicinity of each heterojunction interface patterned into stripes.

This example is manufactured, for example, as follows.

Refer to FIG. 2 (1) 2. The n-type A
The lxGa, -, As layer 2 and the non-doped i-type GaAs layer 3 are epitaxially grown to a thickness of, for example, 1100 nm.

For example, a 5iOz film is provided on the i-type GaAs layer 3, and a mask width wI=Q, 4gm is formed on the portion above the channel region.
, an opening width wz=Q, and a striped pattern of 4 Inn is formed to form a mask 11.

Refer to FIG. 2(2): Using this mask 11, the i-type GaAs layer 3 is etched by, for example, a reactive ion etching method using carbon dichloride difluoride (CChFt). In this etching method, the GaAs layer 3 is made of AlGa
The As layer 2 is selectively etched, and the i-type GaAs layer 3 is made to have a stripe width W=0.1 to 0.2 pm, which is narrower than the mask width W+, due to the side etching effect.

Refer to FIG. 2 (3): The mask 11 is removed, the Sing film 5 is deposited, and a film 12 such as a resist is further applied to make the upper surface flat. By dry etching with (02) added, a flat surface is formed between the 5iOz films 5 on which the striped pattern of the i-type GaAs layer 3 is exposed.

Refer to FIGS. 1(al) and (b): Through this etching process, the GaAs layer 3 which will become the resource/drain contact region 4 is also exposed.
with an energy of about 100 keV and a dose of 1×1013
After implanting ions of CIl-2 and performing activation heat treatment,
Type source/drain contact regions 4 are formed, source and drain electrodes 6 made of, for example, AuGe/Au are provided, and alloying heat treatment is performed.

See FIGS. 1(a) and 1(C): A gate electrode 7 made of, for example, A1 is provided.

In this embodiment, for example, at a temperature of 77 K, the electron mobility is about I x 106cn+"/V,s, and the electron mobility of a conventional two-dimensional quantized HEMT is 1 to 10 x 10'
cm"/V,s, e.g. 6 X 10'cm"/V;s
A clear increase has been demonstrated compared to the extent of

In the above embodiment, the n-type AlGaAs layer is on the substrate side, but for example, the non-doped i-type GaAs layer is on the substrate side.
A similar effect can be obtained by growing an AlGaAs layer thereon and patterning the electron supply layer into stripes. Furthermore, it is clear that the present invention is not limited to GaAs/AlGaAs semiconductor devices, but can be applied to semiconductor devices using, for example, InGaAs/InAlAs.

〔Effect of the invention〕

As explained above, according to the present invention, the electron mobility is further increased than that of conventional HEMTs by spatially separated doping and interface quantization that approximates one-dimensionality, and the speeding up of semiconductor devices is further promoted. It has a great effect on electronic computing systems, etc.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of an embodiment of the present invention, Fig. 2 is a cross-sectional view taken along the Y-Y” line during the manufacturing process, and Fig. 3 is a schematic side sectional view of a conventional example. 2 is an n-type AlzGaI-xAs layer, 3 is a non-doped i-type GaAs layer, 3e is an electron gas, 4 is an n-type source/drain contact region, 5 is a protective insulating film, 6 is a source and drain electrode, 6A is an alloyed region, 7 is a gate electrode, 11 is a mask, and 12 is a film such as a resist.

Claims (1)

[Claims] A heterojunction is provided between a non-doped first semiconductor layer and a second semiconductor layer that has a smaller electron affinity than the first semiconductor layer and contains donor impurities, and the heterojunction interface in the channel region is Formed into a plurality of mutually parallel stripes, an electron gas separated between the stripes and quantized at least in a direction perpendicular to the interface is generated near the interface and distributed across the stripes. A semiconductor device characterized in that the electron gas is controlled by a gate electrode provided.