JPH02231734A - Gaas integrated circuit - Google Patents

Abstract

PURPOSE:To enable a GaAs integrated circuit to be formed without complicating the process by respectively connecting plural P-N junction diodes in series between each input/output signal line and power source, and connecting at least one of P-N junction diodes so that it may be reverse to other diodes. CONSTITUTION:Two P-N junction diodes 1 and 2, which are connected reversely with each other, are put between an input/output signal line and a grounding power source line. For these protective diodes, the P-N junction diode 1 works as a protective diode to positive surge, and the P-N junction diode 2 functions as a protective diode to the negative surge. By using P-N junction as a protective diode this way, larger electrostatic breakdown strength can be obtained with small area as compared with the case where Schottky junction is used. Accordingly, a drawing-out electrode will do, so long as it is taken out to an N-type GaAs region, and there is no special need to add a process anew for formation of a protective diode. Hereby, a GaAs integrated circuit of high yield rate can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to GaAs integrated circuits with input/output protection circuits.

Conventional technology GaAs MESFET C methanol φ semiconductor (sheet-key junction gate type) field effect transistor]
Integrated circuits using GaAs are being developed in various fields because they are capable of high-speed signal processing that cannot be achieved with integrated circuits made of silicon due to the high mobility of GaAs.

In putting GaAs integrated circuits into practical use, the problem of electrostatic withstand voltage of signal terminals is a major issue. GaAs integrated circuits use MESFETs as basic structural units;
is known to have low electrostatic withstand voltage and be susceptible to surges. In order to improve the electrostatic withstand voltage, it is necessary to incorporate a protection diode.

FIG. 7 is a diagram showing a general protection diode circuit. In conventional GaAs integrated circuits, as a protection diode,
Shitkey junction diode DIOO. D200 was used. However, in order to obtain a surge withstand voltage equivalent to that of the St integrated circuit, there was a problem in that a Schittky junction diode with a very large area had to be used. On the other hand, it is also possible to form this surge protection diode with a PN junction diode. PN junction diodes have a higher electrostatic withstand voltage than Sirotchi junction diodes and can provide sufficient capacitance in a small area, but p-type GaA
If an ohmic electrode is to be provided in the s-region, a metal material different from that used for the n-type electrode must be used, and new steps such as metal material vapor deposition, photolithography, etching, or lift-off are required. In the manufacture of integrated circuits, complication of the process is a problem because it directly leads to deterioration in yield and directly affects manufacturing costs. As another electrostatic protection circuit, it is known that inserting a series resistor in the input/output signal line is a good idea.In circuits that handle high-speed signals such as GaAs IC1 GaAs integrated circuits, the frequency characteristics deteriorate significantly, so it cannot be applied. difficult.

Problems to be Solved by the Invention As mentioned above, in conventional GaAs integrated circuits, if a Shibattky junction diode is used as a protection diode, a diode with a very large area must be used, and a PN junction diode must be used. If used, the process would become unavoidably complicated. The present invention aims to provide a GaAs integrated circuit with a built-in surge protection circuit that solves the problems of the GaAs integrated circuit.

Means for Solving the Problems In order to solve the above problems, the present invention connects a plurality of PN junction diodes in series between each input/output signal line and a power supply line, and At least one of the diodes is connected in the opposite direction to the other diodes, and a series resistor is inserted in the input/output terminal for the low frequency signal.

Function The present invention uses a PN as a protection diode with the above configuration.
Since a junction diode is used, a protection circuit can be formed with a diode of small area. Also, since a PN diode connected in series in the opposite direction is used, the extraction electrode is an n-type G
It is sufficient to take out only the aAs region, and there is no particular need to add a new process for forming the protection diode. Furthermore, by inserting a series resistor only in the input/output terminals of low frequency signals, an electrostatic withstand voltage equivalent to that of a silicon integrated circuit can be obtained without impairing the high frequency characteristics of the integrated circuit. An electrostatic protection circuit according to an embodiment is shown. Two PN junction diodes 1.2 connected in opposite directions are inserted between the input signal line and the ground power line.

FIG. 2 is an example showing an actual pattern diagram and cross-sectional view of the protection circuit and FET shown in FIG. 1. IO is semi-insulating GaA
s substrate, 11, 12, 18, 17 is a NyJIGaAs region, for example, I
S1 ions are implanted at a dose of X10"cm-". l3 is a P-type Ga'As region, for example 1
1 x 10”cm- with acceleration energy of 30keV
"Ion implantation of Zn ions. 14, 15., 18.
Reference numeral 19 denotes an ohmic electrode for the N-type GaAs region, which is patterned by depositing, for example, AuGe/Ni/Au and lifting off. The protection circuit shown in FIG. 1 can be constructed by connecting the ohmic electrodes 14 and 15 to the input signal line and the ground power line, respectively. In the protection diodes thus formed, the PN junction diode 1 functions as a protection diode against positive surges, and the PN junction diode 2 functions as a protection diode against negative surges. In any case, since a PN junction is used as a protection diode, a large electrostatic withstand voltage can be obtained with a small area compared to the case where a symmetry junction is used. For example, under the above ion implantation conditions, the PN junction diode 1,
If the length of 2 is 90um, it will be 400v.
It is possible to obtain an electrostatic withstand voltage of (100 pF
, for tests using the 0Ω capacitor discharge method).

FIG. 3 also shows a plan view and a sectional view of the FET formed together with the protection circuit. 18 and 19 are source and drain electrodes, 16 and 17 are N-type regions under the source and drain electrodes, 20 is a gate metal, and 21 is a lightly doped n-type region that becomes a channel of the FET. Since the extraction electrode of the protection diode part is taken out only from the N-type GaAs region, the only additional step required to form the protection circuit is the ion implantation step for forming the P-type GaAs region 13, which is a significant step in the manufacture of integrated circuits. This is an advantage.

FIG. 3 shows another embodiment of the invention. Two diode groups 5 according to the present invention inserted into the input signal line and the ground power line
0 is also formed between the power supply line and the input signal line,
Greater surge resistance can be ensured. FIG. 4 shows yet another embodiment of the invention. Two groups of diodes 50 inserted into the input signal line and the ground power line are also formed between the power line and the input signal line, and a series resistor 30 is further inserted to ensure even greater surge resistance. Can be done. However, care must be taken as this series resistance has a negative effect on high frequency characteristics.

FIG. 5 is a circuit block diagram of a variable frequency divider which is an example of a GaAs integrated circuit constructed by SCFL (source coupled FETI logic). This circuit is IG
Hz band input (IN) can be set in two modes: l28/129/l depending on the level of control signals (NC, S!)
Switch to the four division ratios of li4/G5 and set the output (O
It is a GaAs integrated circuit such as UT). The electrostatic withstand voltage without a built-in electrostatic protection circuit is 30 to 150V, which is a big problem in practical use. An example in which the protection circuit of the present invention is applied to this variable frequency divider will be described.

Input terminal (ILIN) to which IGHz high frequency signal is applied
) has the protection circuit shown in Figure 3, and other low speed (10MH
A protection circuit (series resistance of 1 kΩ) shown in FIG. 4 was used for the terminals (IC, SIF, OUT) that operate at temperatures around

When the protection circuit of the present invention is applied, 25
Electrostatic withstand voltage of 0V or more can be obtained. Input terminal (I
If the protection circuit shown in Figure 4 is applied to N, IN), the electrostatic withstand voltage can be increased to about 400V, but this will have a negative effect on the high frequency characteristics, and if a series resistor of 1 kΩ is used, for example, the maximum operation of the frequency divider will be reduced. Frequency is from IGHz to 700MHz
z, so the one shown in FIG. 3 is desirable here.

Effects of the Invention As described above, by using the present invention, since a PN junction diode is used as a protection diode, a protection circuit can be formed using diodes with a small area, and PN diodes connected in series in opposite directions can be formed. Since the extraction electrode only needs to be taken out for the n-type GaAs region, and there is no need to add a new process to form the protection diode, it is possible to realize high-yield GaAs integrated circuits, and also to realize low-frequency By inserting a series resistor only at the signal input/output terminal, high electrostatic stylus pressure can be obtained without impairing the high frequency characteristics of the integrated circuit, and its practical value is extremely large.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIG. 2 is a plan view and a sectional view of a protection circuit according to an embodiment of the present invention, and FIG.
FIG. 4 is a circuit diagram showing another embodiment of the present invention. Fifth
The figure is a circuit block diagram of a GaAs variable frequency divider that is an embodiment of the present invention, Figure 6 is a diagram showing the electrostatic withstand voltage of the variable frequency divider of Figure 5 with and without a protection circuit, and Figure 7 is a diagram of the conventional variable frequency divider. It is a circuit diagram showing a protection circuit of. 1, 2●●●PN junction diode, 50●●● diode group. Agent's name Patent attorney Shigetaka Awano Baka Tech name Figure Figure αυ <b> Figure Figure Figure Figure

Claims (4)

[Claims] (1) A plurality of PN junction diodes are connected in series between each input/output signal line and a power supply line, and at least one of the plurality of PN junction diodes is connected in a direction opposite to that of the other diodes. A GaAs integrated circuit characterized by: (2) A plurality of PN junction diodes are connected in series between each input/output signal line and a power supply line, and at least one of the plurality of PN junction diodes is connected in a direction opposite to that of the other diodes. A GaAs integrated circuit characterized in that a resistor is inserted in series between the input/output signal line and the internal circuit. (3) In a GaAs integrated circuit having a plurality of input/output signal lines, a plurality of PN junction diodes are connected in series between the input/output signal line of the high frequency signal and the power supply line, and each of the plurality of PN junction diodes At least one diode is connected in the opposite direction to the other diodes, and a plurality of P
N-junction diodes are connected in series, at least one of the plurality of PN-junction diodes is connected in the opposite direction to the other diodes, and the N-junction diodes are connected in series between the input/output signal line of the low frequency signal and the internal circuit. A GaAs integrated circuit characterized in that a resistor is inserted in the GaAs integrated circuit. (4) The high frequency signal is the input signal of the frequency divider, the low frequency signal is the division ratio setting signal and the division output signal, and the input signal is divided into the division ratio according to the division ratio setting signal. G according to claim 3, which has a function of frequency-dividing and outputting
aAs integrated circuit.