JPH01136377A - Semiconductor device - Google Patents

Abstract

PURPOSE:To obtain a semiconductor device operating at ultra-high speed by composing a control electrode buried in a semiconductor of an oxide superconductor in order to control currents flowing between two electrodes oppositely faced, holding the semiconductor and forming an insulating layer onto the surface oppositely faced to the current path of at least currents in the oxide superconductor. CONSTITUTION:Trenches 21a are shaped to a silicon substrate 21, and annealed and treated. Insulating layers 29 are formed into the trenches 21a. An oxide superconductor 27 is shaped so as to bury the trenches 21a. The superconductor 27 is removed until sections except the trenches 21a are exposed. An insulating layer 29c is shaped onto the whole surface. Sections except sections corresponding to the superconductors 27 are gotten rid of. A semiconductor layer 21b having an impurity profile is grown onto the silicon substrate 21, and the superconductors 27 are buried with the semiconductor layer 21b and the silicon substrate 21. An N-type impurity is doped, and electrodes are shaped. Accordingly, a distance between a control electrode and an electrode on the side where electrons reach in a first or second electrode can be shortened.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a semiconductor device with a vertical structure such as a permable base transistor, and particularly relates to a semiconductor device 1 having a feature of a current control electrode. It is something to do.

(Prior Art) In order to realize ultra-high-speed computers, high-frequency devices, high-speed thyristors, etc., semiconductor devices that perform ultra-high-speed switching operations are required. For this reason, the development of such semiconductor devices has been energetically pursued for some time.

For example, one way to speed up the operation of a semiconductor device such as a field effect transistor is to reduce its size. That is, the purpose is to minimize the source train open circuit M to improve the operating speed. In addition, by miniaturizing, highly integrated semiconductor devices,
Moreover, it is also possible to obtain a semiconductor device Ill with low power consumption.

It can be said that the semiconductor device that is most likely to obtain the above-mentioned advantages is one having a vertical structure, and a vertical semiconductor device in which a control electrode is embedded in a semiconductor is known as one of the ultimate semiconductor devices. As such a vertical semiconductor device, for example, there is a document (IEEE)
ED-27 (1980) P.

Permeable base transistors (P, B, T”) disclosed in
(I.E.E.E.) ED-25 (+978)
P, 761), a static induction transistor (
S, 1. T, ) etc.

FIG. 4 is a cross-sectional view schematically showing the structure of a conventional permeable base transistor.

In FIG. 4, 11 indicates a semiconductor, and 13 and 15 indicate a first electrode and a second electrode formed on the semiconductor 11, respectively, so as to face each other with the semiconductor 11 in between. The two electrodes 15 become a source electrode 13 and a train electrode 15 that are in ohmic contact with the semiconductor 11, respectively.

Further, 17a and +7b are the source electrodes 13 of the semiconductor 11.
and a control electrode that controls the current flowing between the train electrodes 15.

The operating principle of such a semiconductor device is disclosed in various documents including the above-mentioned document, so its explanation will be omitted, but conventional materials for forming the control electrodes 17a and +7b metals such as tungsten were used.

By the way, since the metals mentioned above have a large resistance, the resistance component R6 of the control electrode becomes large, and as a result, in the case of a semiconductor device that performs switching by raising and lowering the potential of the control electrode, the control electrode cannot be charged or discharged. It will take a long time to do so.

The time required for charging and discharging is one factor that determines the switching speed of the semiconductor device. However, in the semiconductor device described in the above-mentioned literature, since the size of the semiconductor device itself is very large, the size of the control electrode can also be made large, and therefore the resistance Ra of the control electrode is It can be made small, and therefore the charging and discharging time can be made negligible.

Another factor that determines the switching speed of a semiconductor device is the time n during which electrons travel between the control electrode and the train electrode. Calculate the distance between the center point of the control electrode and the train electrode. (see FIG. 4), and when the average velocity of electrons is Qv, this traveling time τ can be expressed as τ=L co/V. Therefore, in order to obtain a semiconductor device Its capable of ultra-high-speed operation, it is necessary to reduce the distance between the control electrode and the train electrode.

(Problems to be Solved by the Invention) However, the purpose is to obtain a semiconductor device capable of ultra-high-speed operation. If the value of is made small, the desired electron transit time τ of 4 m can be obtained, but on the other hand,
The size of the control electrode itself must necessarily be made small. Therefore, in conventional semiconductor devices in which the control electrode is made of metal such as tungsten, the resistance RG of the control electrode cannot be ignored, and the operating speed limit of the semiconductor device is ultimately determined by this resistance RG. The problem arises that the

In addition, in the permeable paste transistor shown in the third cause, since the control electrode is in direct contact with the semiconductor, many surface layers may be formed and defects may be induced at the interface between the control electrode and the semiconductor. There were manufacturing problems. Moreover, such surface order and defects are a cause of leakage current generation, and such leakage current delays the charging time of the control electrode, resulting in an obstacle to high-speed operation of the semiconductor device.

This invention was made in view of these points,
Therefore, an object of the present invention is to solve the above-mentioned problems and provide a semiconductor device M that operates at ultra high speed.

(Means for Solving the Problems) In order to achieve this object, according to the present invention, the current flowing between the first and second electrodes that face each other with the semiconductor sandwiched therebetween is controlled. In order to achieve this, in a semiconductor device comprising a control electrode embedded in the semiconductor, the control electrode is made of an oxide superconductor, and the oxide superconductor has at least the above-mentioned current. It is characterized by having an absolute wire layer on the surface facing the road.

(Function) According to such a configuration, by operating the semiconductor device according to the present invention at a temperature below the critical temperature of the oxide superconductor constituting the control electrode, the resistance R0 of the control electrode can be reduced.
becomes a negligible value.

Therefore, even if the control electrode is made very small, the switching speed will not be reduced due to the resistance of the control electrode. Therefore, the distance between the control electrode and the electrode on the side where electrons reach out of the first or second electrode, that is, the above-mentioned Lo. It becomes possible to make the distance corresponding to the distance very small.

In general, it is known that the critical current value of oxide superconductors is large, which makes it possible to increase the potential of the control electrode to a practical value in a very short time.

Further, according to the present invention, an insulating layer is provided on at least the surface of the control electrode facing the current path to prevent direct contact between the control electrode and the semiconductor. Therefore, since the surface order can be greatly reduced, both leakage current and stray capacitance can be reduced.

Furthermore, if the insulating layer in contact with the oxide superconductor is made of, for example, a thermal oxide film, the optimum composition, particularly the optimum composition of oxygen, in the oxide superconductor can be ensured.

(Embodiments) Hereinafter, embodiments of the semiconductor device of the present invention will be described with reference to the drawings. It should be noted that each figure used in the explanation is only a schematic illustration to the extent that the present invention can be understood, and therefore,
It is clear that the dimensions, shapes, and arrangement of each component are not limited to the illustrated example, and that various modifications or changes can be made.

FIG. 1 is a sectional view schematically showing the structure of a semiconductor device according to an embodiment.

In FIG. 1, 21 indicates a semiconductor, and this semiconductor is
For example, 6a-based compound semiconductors such as Si or GaAs,
Alternatively, it can be made of an In-based compound semiconductor such as InP.

Reference numerals 23 and 25 indicate first and second electrodes facing each other with the semiconductor 21 in between, which are the first electrodes 2 in this embodiment.
3 is a source electrode in ohmic contact with the semiconductor 21, and the second electrode 25 is a drain electrode in ohmic contact with the semiconductor 21.

27a and 27b indicate control electrodes buried in the semiconductor 21 in order to control the current flowing through the train electrode 25 and the source electrode 23, and these control electrodes 27
a and 27b are made of oxide superconductor. As this oxide superconductor, for example, YBa2CuaO7-s
(6<0.3), but the present invention is not limited thereto, and of course other oxide superconductors may be used.

In this structure, the current flowing in the current path between the train electrode 25 and the source electrode 23 can be controlled by changing the voltage applied between the control electrodes 27a and 27b, as in the conventional case.

Further, 29a is a control electrode 2 made of an oxide superconductor.
7a indicates an insulating layer provided to reduce the area where the semiconductor 21 contacts with the M contact, and 29b shows the control electrode 27b formed of an oxide superconductor and the semiconductor 21 with the M contact. Insulating layer 29a of this example shows an insulating layer provided to reduce the area.

29b is such that it covers the entire surface of the control electrode, but the arrangement of these insulating layers is not limited to this.The insulating layer covers at least the area between the train and source electrodes of the control electrode. It is sufficient that they are provided on the surfaces facing the current path, that is, the control electrodes 27a and 27b facing each other, and it is of course possible to have a structure as shown in FIG. 2, for example.

Further, the shape of the control electrode in this embodiment is rectangular in cross section because such a shape facilitates manufacturing and takes into consideration electric field efficiency and the like.

However, it is clear that the shape of the control electrode can be changed depending on the design of the semiconductor device.

Here, regarding the semiconductor device of the example, the transit time of electrons between the control electrode and the train electrode, and the charging/discharging time of the control electrode will be considered.

First, regarding the transit time τ, let us assume that the distance Lao (see Figure 1) between the center point of the control electrode and the train electrode is 2000 people, and the average velocity V of the electrons is 2x lo7cm.
/second, then from τ= L ao/V, τ=IQ−
It will be 12 seconds. Therefore, Lo. By having about 2,000 people, it is possible to realize an ultra-high-speed semiconductor device that operates at a speed of about 1 picosecond.

Also, considering the charging/discharging time of the control electrode, it is as follows.

The shape of the control electrode is such that the cross-sectional area is, for example, 400λ x 800 people = 3.2 x 10-” cm2, and the length is, for example, 4 um.
shall belong to. In such a case, if the control electrode is made of conventional tungsten, its resistivity will be approximately 4 x 10
-'Ω・cl', so in the above shape, the resistance is minute.

becomes 500Ω. Also, the capacitance C of the control electrode in this shape
6 is approximately 3 femtofarads (fF), so the C6.Ra product is 1.5 x 10-" seconds, so the time τ determined by the co"Ra product. is longer than the electron transit time τ, and the switching speed of conventional semiconductor devices using tungsten is this charging/discharging time τ. The speed will be controlled by However, according to the semiconductor device of the present invention in which the control electrode is composed of an oxide superconductor, the resistance valve Ra of the control electrode becomes negligibly small, and as a result, the charging/discharging time τ
. , is a value sufficiently smaller than the transit time T of electrons. Roughly speaking, electric current can be applied to the control electrode. is the critical current and degree of the oxide superconductor. If the cross-sectional area of the control electrode is S, then ■. = J a × S, so J a =
If IO'A/cm2 and S=3.2×10-th cm2, then Ia=320 LIA. Also, if the potential of the control electrode is 'Fr V c, then Vo is VG =Q/C=
Since 2n is determined by Ia - t/C, the potential V of the control electrode becomes 100 mV or more by flowing a current of 320 LIA for 1 pico second through the control electrode with a capacitance of 3 fF.

As described above, according to the semiconductor device of the present invention, since its operating speed is not affected by the charging/discharging time of the control electrode, it is also possible to operate at the oscillation frequency of terahertz (THz).

Furthermore, the fact that the control electrode is made of oxide superconductor is because
Regardless of the structure of the semiconductor device, it will contribute to shortening the charging/discharging time of the control electrode, but in terms of contributing to the operating speed of the semiconductor device, the electron travel time is greater than the charging/discharging time of the control electrode. An element structure in which L is also shortened, that is, L
It can be said that a remarkable effect is exhibited when aO becomes thinner than about 3000λ.

Next, in order to deepen the understanding of the present invention, an example of a method for manufacturing the semiconductor device of the embodiment shown in FIGS. 1 and 2 will be described.

3A to 3G are process diagrams schematically showing an example of a method for manufacturing the semiconductor device shown in FIG. 1 using cross-sectional views.

A silicon (Si) substrate, for example, as a semiconductor is prepared. A control electrode 27a is provided on this silicon substrate 21.

A trench 21a for burying 27b is formed by, for example, ion milling or ECR (Electron Cycling).
It is formed using a plasma etching method or the like. Note that the groove 21a in this embodiment
is 1000 people wide, 4um long, and 600λ deep. In this embodiment, a large number of such grooves 21a are formed at predetermined intervals in the silicon substrate 21 (FIG. 3(A)).

Next, in order to remove etching damage from the silicon substrate 21 in which the grooves 2ta are formed, the substrate 21 is subjected to, for example, annealing treatment.

Next, an insulating layer 29 having a thickness of, for example, about 50 to 100 λ is formed in the groove 21a by a suitable method such as thermal oxidation (FIG. 3 (8)).

Next, on the substrate 21 including the groove 21a, an oxide superconductor indicated by 27 as a material constituting the control electrode is formed so as to fill at least the groove 21a (FIG. 3(C)).
This oxide superconductor can be formed by a suitable method such as the CVD method proposed in Japanese Patent Application No. 62-181655 filed by the same applicant.

Next, the oxide superconductor 21 is removed until the portion of the silicon substrate 21 other than the groove 21a is exposed (FIG. 3(D)).
).

Next, on the silicon substrate 21 including the oxide superconductor 27, an insulating layer 29c is formed to a predetermined thickness, for example, about the thickness of the insulating layer 29, by a suitable method such as CVD (see FIG. 3). E)), insulating layer 29c in this embodiment
is made of the same material as the insulating layer 29, 5in2.

Next, only the part of the insulating layer 29c corresponding to the oxide superconductor 27 is left and the other part is removed (FIG. 3(F)'). As a result, the oxide superconductor 27 is removed from the insulating layer 27.
9 and 29c (hereinafter referred to as an insulating layer 29).

Next, on the silicon substrate 21 having the oxide superconductor 27 covered with the insulating layer 29, a semiconductor layer 21b having an impurity profile necessary for the structure of the semiconductor device is grown using an epitaxial growth method. . As a result, the oxide superconductor 27 is connected to the semiconductor layer 21b and the silicon substrate 2.
1 results in an embedded structure.

Next, from below the silicon substrate 21 and the semiconductor layer 21
For example, an n-type impurity is doped into n++ from above the substrate b, and then a metal such as an A9 film is deposited on the surface and the substrate is heat-treated to form a train electrode and a source electrode.

In this way, the structure shown in Fig. 1 is obtained (Fig. 3).
Figure (G)).

Furthermore, in manufacturing the semiconductor device shown in FIG. 2, processing is first performed according to the manufacturing process explained using FIGS. This can be done by growing a semiconductor layer shown as 21b.

(Effects of the Invention) As is clear from the above description, according to the semiconductor device of the present invention, the control electrode embedded in the semiconductor is composed of an oxide superconductor.

Therefore, by operating the semiconductor device W at a temperature below the critical temperature of this oxide superconductor, the resistance R, of the control electrode becomes a negligible value, so even if the control electrode is made very small. , the switching speed is no longer reduced due to the resistance of the control electrode. Therefore, the distance between the control electrode and the one of the first or second electrodes that the electrons reach, that is, as described above. . The distance corresponding to can be made very small.

Further, according to the present invention, by providing an insulating layer on at least the surface facing the current path of the control electrode, it is possible to greatly reduce the surface roughness, thereby reducing the leakage current and stray capacitance of the semiconductor device. This can prevent a decrease in operating speed.

Therefore, it is possible to obtain an ultra-high-speed semiconductor device that employs an element structure that increases the transit time of electrons in the semiconductor device.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view schematically showing the structure of a semiconductor device of an example, FIG. 2 is a cross-sectional view schematically showing the structure of a semiconductor device of another example, and FIGS. G) is a manufacturing process diagram for explaining the method of manufacturing the semiconductor device of the embodiment, and FIG. 4 is a diagram for explaining the conventional technique. 21...Semiconductor, 21b...Semiconductor layer 2
3... First electrode (source electrode) 25... Second electrode (train electrode) 27... Oxide superconductor 27a, 27b - Control electrode 29, 29a, 29b, 29c... Insulating layer. Patent applicant Oki Electric Industry Co., Ltd. 21: Semiconductor 27a, 27b
: Control electrode 23: M-electrode (first electrode) 2
9a, 29b: Insulating layer 25: Second electrode (train electrode) Fig. 1 Fig. 28 Fig. 4 for explaining the prior art

Claims (1)

[Claims] (1) A semiconductor device comprising first and second electrodes facing each other with a semiconductor interposed therebetween, and a control electrode buried in the semiconductor for controlling the current flowing between the first and second electrodes, wherein the control The electrode is made of an oxide superconductor, and
A semiconductor device characterized in that an insulating layer is provided on at least a surface of the oxide superconductor that faces the current path of the current.