JP2697677B2 - Current switch and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a current switch and a method of manufacturing the same, and more particularly, to a current switch which is an electronic device operating at a high frequency and a method of manufacturing the same.

[0002]

2. Description of the Related Art In the era of mobile radio such as mobile phones, small and light micro-monolithic ICs (MMIs) have been developed.
The development of C) is very important. However, the RF current switch used as a key component of the conventional MMIC is composed of a large number of transistors and is complicated. Also, for example, 19
1994 IEICE Spring Conference C-119, C-12
As can be seen from 0, P2-624, 20625, etc., the ratio of signal to leakage current in a single pole double throw (SPDT) switch, which is a switch of one input and two output terminals at the current development level, is about -20 dB. is there.

As a current switch based on a completely different operating principle, a directional coupler utilizing the quantum mechanical properties of electrons has been proposed, and its operation has been actually demonstrated ("Seiken Kenkyu").
Vol. 6, No. 3, p. 7, Appl. Phys.
Left. 56, 78 (1990), or App
l. Phys. Left. 56,2527 (199
0)).

[0004]

However, the conventional SP
In the DT switch, the ratio between the signal and the leak current is large, and a smaller value is desired. In addition, the speed of MMICs has been increasing year by year, and RF
A current switch is required. Further, the directional coupler utilizing the quantum mechanical properties of the above-described electrons operates only at a very low temperature, and is difficult to operate at room temperature.
The resulting current levels are very small, on the order of nanoamps.

[0005] The present invention has been made in view of the above points,
An object of the present invention is to provide a current switch capable of obtaining a sufficient amount of current and operating at room temperature, and a method of manufacturing the same.

[0006]

In order to achieve the above object, a current switch according to the present invention has first and second damaged regions formed on a semiconductor thin film substrate and dividing the semiconductor thin film substrate into three regions. An injector electrode formed in a first region sandwiched between the first and second damaged regions among the three regions, and an injector electrode formed in the remaining two regions excluding the first region among the three regions. Controlling the first drain electrode to be a reference potential, applying a bias voltage to each of the second drain electrode and the injector electrode, and applying the bias voltage to the second drain electrode. The output of the input signal input to the injector electrode to the first drain electrode is controlled according to the signal.

Here, the semiconductor thin film substrate has a semiconductor heterojunction structure or an epitaxial layer, and the first and second semiconductor thin film substrates have the same structure.
Is characterized in that the damaged region is formed for the two-dimensional electron gas on the semiconductor thin film substrate.

Further, the method of manufacturing a current switch according to the present invention includes a first step of forming a semiconductor thin film substrate having a predetermined pattern, a first and a second drain electrode and an injector electrode at predetermined positions on the semiconductor thin film substrate. Forming a first and a second damaged region with a focused ion beam on the semiconductor thin film substrate having undergone the second process.
To divide the semiconductor thin film substrate into three regions.
A first region of the region sandwiched between the first and second damaged regions
In the area, the injector electrode is located.
The remaining two regions except the first region have the first and second regions respectively.
The object is achieved by a method including a third step of separately locating the second drain electrodes .

[0009]

FIG. 1 is a diagram showing the principle of a current switch according to the present invention. First and second damaged regions 2 and 3 are formed on the semiconductor thin film substrate 1, whereby the semiconductor thin film substrate 1 is divided into three regions 4, 5 and 6. The first region 4 sandwiched between the first and second damaged regions 2 and 3 among the three divided regions 4, 5 and 6 is an injector, on which an injector electrode 7 is formed. Also, 3
The remaining two regions 5 and 6 of the four regions 4, 5 and 6 except for the first region 4 are first and second drains, respectively, and have first and second drain electrodes 8 and 9 respectively.
Are formed respectively.

The first drain electrode 8 is set to the ground potential as a reference potential, and bias voltages V _I and V _D2 are applied to the injector electrode 7 and the second drain electrode 9 from bias power supplies 10 and 11, respectively. . The bias voltage V _I for normal operation is positive. When a positive bias voltage V _D2 is applied to the drain electrode 9 in this state, all the current of the injector 4 flows into the first drain 5 as shown by an arrow 12, and when the bias voltage V _D2 is set to be negative,
All the current of the injector 4 flows into the second drain 6, as indicated by the arrow 13. Therefore, by changing the polarity of the bias voltage V _D2 to the second drain 6, it functions as a current switch that can turn on and off the current to the first drain 5.

Therefore, the current switch having the basic configuration of FIG. 1 described above is represented by reference numeral 20 in FIG. 2, and the terminal I is connected to each of the injector I, the first drain electrode D1, and the second drain electrode D2. It is assumed that bias voltages V _I , V _D1 and V _D2 are applied from 22 and 23. Further, the injector I is input RF signal from the terminal 24 via a filter in series circuit of the coil L _I and a capacitor C _I, the first drain electrode D1 is the series circuit of the capacitor C _D1 and a coil L _D1 It is connected to terminal 25 via a filter. Further, a control signal V _D2 is applied from the terminal 23 to the second drain electrode D2.

As a result, the high-frequency signal (RF signal) input to the injector I is output from the first drain electrode D1 to the terminal 25 via the C _D1 and L _D1 in series by the control signal V _D2 . The RF signal can be turned on or off. In addition, since a sufficiently high electric field is applied to both ends of the damaged region, the speed of electrons passing through this region has reached a saturated state, and a response at a sufficiently high frequency can be expected from this.

Here, the fine line-shaped damaged region on the semiconductor thin film is defined as
The current flowing beyond depends on the voltage applied to the damage area
And change greatly. Figure 3 shows the flow over this damaged area
1 shows an example of a current-voltage characteristic. The damaged area here is
As shown in the inset of FIG. 3, the structure of the sample was GaAs.
/ AlGaAs semiconductor two-dimensional electron gas (2DEG)
Focused ion using Ga as ion species
Beam dose (FIB) is 10^Four / Cm or less
A damaged area is formed on the substrate above.

Then, when a bias voltage is applied at room temperature between two regions divided by the damaged region, and a current flowing between the divided regions is measured, as shown in FIG.
Within a voltage range of about 10 V, the current changes by seven digits, and a large current can be obtained. Therefore, 2 divided by these damaged areas
By properly biasing the voltage between the two regions, a new device or circuit can be created with only one process step. Among these new devices and new circuits, current switches are the simplest and most useful.

[0015]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 4 is a schematic perspective view of a first embodiment of the current switch according to the present invention. As the substrate, a compound semiconductor heterostructure is used, and in the embodiment shown in FIG.
The s substrate 41 is used. On this semi-insulating GaAs substrate 41, an undoped GaAs buffer layer 42 of about 1 μm is grown.

Thereafter, undoped Al _0.3 Ga _0.7
An As layer is grown to a thickness of about 800 °, and sheet doping of impurity Si is performed during the growth. Thereby, the sheet dope layer 43 and the undoped Al _0.3 Ga _0.7
The As layer 44 is formed in a planar T shape. Thereby, the concentration and the mobility of the two-dimensional electron gas obtained at the hetero interface are
They are 7.65 × 10 ¹⁵ / cm ² and 0.63 m ² / Vs, respectively.

The undoped Al _0.3 Ga _0.7 As layer 44 is a focused ion beam (FIB) using Ga as an ion species.
As a result, damaged regions 45 and 46 are formed at a line dose of 4 × 10 ⁶ / cm, and are divided into three regions 47, 48 and 49. The first area 47 sandwiched between the first and second damaged areas 45 and 46 among the three divided areas 47, 48 and 49 is an injector, and an injector electrode 50 is formed.

The remaining two regions 48 and 4 of the three regions 47, 48 and 49 except the first region 47
Reference numeral 9 denotes first and second drains, respectively, on which first and second drain electrodes 51 and 52 are formed, respectively. The circuit diagram of this embodiment is the same as FIG.

Next, an embodiment of the method for manufacturing a current switch according to the present invention will be described with reference to sectional views shown in the order of steps in FIG. In the figure, the same components as those in FIG. 4 are denoted by the same reference numerals. First, as shown in FIG.
After growing a buffer layer 42 of undoped GaAs, a Si sheet doped layer 43 and an undoped AlGaAs layer 44 grown by sheet doping on an As substrate 41, a negative resist is applied thereon, and optical lithography or ion beam lithography is performed. A pattern having a thickness of several μm is formed.

Subsequently, using the resist pattern 55 as a mask, the substrate shown in FIG. 5A is solution-etched as shown in FIG. Thereafter, the resist 55 is peeled off, and AuGe / Ni is deposited on the first and second drain regions located at the front and back of the drawing by a normal lift-off method.
By performing alloying, first and second drain electrodes (51 and 52 in FIG. 4), which are ohmic electrodes, are formed. FIG. 5 is slightly before the FIB damaged area 46 in FIG.
When cut at the portion of FIG.
FIG. 4 is a cross-sectional view, showing a flat T-shape by the above solution etching.
Simultaneously with the formation of the first and second electrodes on the formed substrate
The injector electrode (50 in FIG. 4) is formed in the same manner.
Is done.

Thereafter, as shown in FIG.
Damage introduction by a focused ion beam (FIB) using Ga as an ion species with the beam narrowed to 1 μm is performed in a single stroke across the mesa formed as described above,
The damaged area (45 and 46 in FIG. 4) is formed. This damaged area is about 0.1 μm. Thus, the sample shown in FIG. 4 is completed.

FIG. 6 shows the current-voltage characteristics of the fabricated device at room temperature. That is, FIG. 6 shows the first drain electrode 5
The first bias voltage V _D1 is 0 V, and the drain current I _D1 when the bias voltage V _D2 input to the second drain electrode 52 is changed is shown. The bias voltage V _D2 input to the second drain electrode 52 is a control voltage, and it can be seen that a clear switch characteristic is observed for this control voltage.

Further, as shown in FIG. 6 with V _I, the bias voltage to the injector electrode 50, it is observed that the total current level has changed. Further, the ratio of the signal to the leakage current is -80 dB, and the performance is improved as compared with the conventional current switch described in the section of the related art.

Next, a second embodiment of the present invention will be described. FIG. 7 is a schematic perspective view of a second embodiment of the current switch according to the present invention. As the substrate, a silicon insulating substrate 71 is used. A silicon thin film 72 is formed on the silicon insulating substrate 71. Thereafter, similarly to FIG. 4, a focused ion beam (F
By IB), damaged regions 73 and 74 are formed and divided into three regions 75, 76 and 77. A first region 75 sandwiched between the first and second damaged regions 73 and 74 among the three divided regions 75, 76, and 77 is an injector, and an injector electrode 78 is formed.

The remaining two regions 76 and 7 of the three regions 75, 76 and 77 except for the first region 75
Reference numeral 7 denotes first and second drains, respectively, on which first and second drain electrodes 79 and 80 are formed, respectively. The circuit diagram of this embodiment is the same as FIG.

The present embodiment differs from the first embodiment only in that the substrate used is not a compound semiconductor heterostructure but a silicon epitaxial layer, and the other manufacturing processes and characteristics are almost the same. Therefore, the present embodiment also has the first
As in the embodiment, a high-precision current switch that can obtain a large current at room temperature can be realized.

Next, a third embodiment of the present invention will be described. FIG. 8 is a schematic perspective view of a third embodiment of the electronic switch according to the present invention. In this embodiment, a thin film 82 of an epitaxial layer of compound semiconductor gallium arsenide GaAs is formed on the same GaAs semi-insulating substrate 81 as the first embodiment of FIG. 4, and gallium (Ga) is further formed on the GaAs thin film 82. Damage area 8 is determined by the focused ion beam (FIB) used.
By forming 3 and 84, three regions 85,
86 and 87.

Next, the three regions 85, 86 and 8
7, a first region 85 sandwiched between the first and second damaged regions 83 and 84 is an injector, and an injector electrode 88 is formed. In addition, the remaining two regions 8 excluding the first region 85 among the three regions 85, 86, and 87
Reference numerals 6 and 87 denote first and second drains, respectively, on which first and second drain electrodes 89 and 90 are formed, respectively. The circuit diagram of this embodiment is
Same as 2 .

The present embodiment is different from the first embodiment only in that the substrate used is not a compound semiconductor heterostructure but an epitaxial layer of GaAs, and other manufacturing processes and characteristics are almost the same. Therefore, the present embodiment also has the first
As in the case of the second embodiment, a highly accurate current switch that can obtain a large current at room temperature can be realized.

[0030]

As described above, according to the present invention,
By properly biasing the voltage between the two regions divided by the damaged region, M
A small and light current switch for MIC can be created. Further, according to the present invention, it is possible to realize a current switch that operates at room temperature and obtain a large current, and it is possible to improve the easiness of fabrication and the operation speed as compared with a conventional current switch.

Further, according to the manufacturing method of the present invention, the degree of freedom in design when applied to a more advanced circuit can be increased due to the ease of manufacturing.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the principle of a current switch according to the present invention.

FIG. 2 is a principle circuit diagram of the current switch of the present invention.

FIG. 3 is a diagram showing an example of a current-voltage characteristic flowing over a fine line-shaped damaged region of a semiconductor thin film.

FIG. 4 is a schematic perspective view of a first embodiment of the current switch of the present invention.

FIG. 5 is a sectional view showing one embodiment of a method for manufacturing a current switch according to the present invention in the order of manufacturing steps.

FIG. 6 is a current-voltage characteristic diagram of the first embodiment of the present invention.

FIG. 7 is a schematic perspective view of a second embodiment of the current switch of the present invention.

FIG. 8 is a schematic perspective view of a third embodiment of the current switch of the present invention.

[Explanation of symbols]

1 Semiconductor substrate 2, 3, 45, 46, 73, 74, 83, 84 FIB
Damaged area 4, 47, 75, 85 Injector 5, 48, 76, 86 First drain 6, 49, 77, 87 Second drain 7, 50, 78, 88 Injector electrode 8, 51, 79, 89 First Drain electrode 9, 52, 80, 90 second drain electrode 41, 81 semi-insulating GaAs substrate 42 buffer layer 43 Si sheet doped layer 44 undoped AlGaAs layer

Claims (5)

(57) [Claims] A first damage region formed on the semiconductor thin film substrate and dividing the semiconductor thin film substrate into three regions; and a first damage region and a second damage region among the three regions. An injector electrode formed in a first region sandwiched between the first region and a first drain region and a second drain electrode formed in two remaining regions of the three regions except the first region; Setting the first drain electrode as a reference potential,
A bias voltage is applied to each of the second drain electrode and the injector electrode, and in response to a control signal applied to the second drain electrode, the first drain electrode of an input signal input to the injector electrode A current switch characterized by controlling an output to a current switch. 2. The semiconductor thin film substrate has a semiconductor heterojunction structure or an epitaxial layer, and the first and second damaged regions are formed with respect to a two-dimensional electron gas of the semiconductor thin film substrate. The current switch according to claim 1. 3. A ground potential is applied as a reference potential to the first drain electrode, and a control signal is input to the second drain electrode, and a high-frequency signal input to the injector electrode is changed according to the control signal. 3. The current switch according to claim 1, wherein switching output is performed from the first drain electrode. 4. A first step of forming a semiconductor thin film substrate having a predetermined pattern, and a second step of forming first and second drain electrodes and injector electrodes at predetermined positions on the semiconductor thin film substrate, respectively.
Steps and, said the second step focused ion beam on the semiconductor thin film on a substrate after the forming the first and second damaged region the
The semiconductor thin film substrate is divided into three regions, and the three regions are divided into three regions.
A first region sandwiched between the first and second damaged regions
, The injector electrode is located, and the three regions
The remaining two areas except the first area are respectively
The third where the first and second drain electrodes are separately located
A method for manufacturing a current switch, comprising the steps of: 5. The first and second steps according to the third step.
In order to form a damaged region, a line dose of 10^Four / Cm or more
5. The method according to claim 4, wherein a focused ion beam is used.
A method for manufacturing the current switch according to the above.