JP3496639B2 - High frequency semiconductor device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-frequency semiconductor chip used in microwave and millimeter-wave frequency bands, a high-frequency semiconductor device in which the high-frequency semiconductor chip is sealed in a package, and the high-frequency semiconductor device. The present invention relates to a high frequency communication device having a semiconductor chip or a mother board on which the high frequency semiconductor device is mounted. A semiconductor device for high frequency (for example, HEMT)
GaAs MESFET, GaAs HBT, SiGe including MODFET
HBT, etc.) has a problem that it is vulnerable to electrostatic breakdown because it requires fine processing to operate at a high frequency. Conventionally, as means for protecting semiconductor devices from electrostatic breakdown,
A method of inserting a protective diode as shown in FIG. 5 between a terminal to be protected and the ground and releasing the electrostatic current to the ground has been often used. For example, Japanese Patent Publication No. 6-69101, Japanese Patent Publication No. 7-40571, Japanese Patent Publication No. 6-24243, Japanese Patent Publication No. 7-19
It is as described in the 782 publication. But,
In high frequency regions such as microwaves and millimeter waves, there is a problem that signal loss and distortion occur due to parasitic capacitance, parasitic resistance, and nonlinearity of the protection diode, and high frequency characteristics deteriorate. On the other hand, a high-frequency semiconductor chip that does not use a protection diode that places importance on high-frequency characteristics has a problem that a special assembly line is required to prevent electrostatic breakdown, and package assembly and bare chip mounting are difficult. SUMMARY OF THE INVENTION An object of the present invention is to propose means for improving the resistance to electrostatic breakdown of a semiconductor chip without using a diode, and to prevent high frequency semiconductors from deteriorating the high frequency characteristics of the semiconductor device. It is to realize a chip and realize a high-frequency semiconductor device and a high-frequency communication device with good high-frequency performance that do not require a special assembly line. As a result of examining the electrostatic waveform of the electrostatic breakdown model, it has been confirmed that the instantaneous energy of the low frequency component up to about kilohertz is large and the component above gigahertz is small. Therefore, as a means to protect high-frequency semiconductor devices from electrostatic breakdown, it is beneficial to reduce the instantaneous heat generation by cutting low frequencies or lengthening the low-frequency component passage time constant. It is useful to insert an MIM capacitor having no nonlinearity in series with a terminal to be protected of a semiconductor device for use or to insert a spiral inductor with respect to ground in parallel with a terminal to be protected of a semiconductor device for high frequency. is there. Note that the MIM capacitor refers to a capacitor having a configuration in which a capacitive insulating film is sandwiched between two plate electrodes. The present invention proposes that a plurality of MIM capacitors be connected in series for the following reason. 1. Depending on the composition and thickness of the interlayer insulating film of the MIM capacitor, the MIM capacitor itself may be electrostatically destroyed.
The voltage per capacitor is divided to prevent destruction of the MIM capacitor itself. 2. Since the series insertion loss of the MIM capacitor is sufficiently smaller than the parallel insertion loss of the spiral inductor and the parallel insertion loss of the diode, the characteristic deterioration can be minimized. 3. By connecting a plurality of MIM capacitors in series, a small capacitance value can be realized in a large pattern.
A highly accurate capacitor can be realized. By inserting a plurality of non-linear non-linear MIM capacitors in series into the terminals to be protected of the high-frequency semiconductor device, the electrostatic breakdown resistance of the chip can be improved without causing characteristic deterioration. Package assembly and bare chip mounting are possible without constructing an assembly line, and a high-frequency communication device with good characteristics can be realized. DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a high frequency semiconductor device according to an embodiment of the present invention will be described with reference to the drawings. (Embodiment 1) First, a high-frequency semiconductor device according to Embodiment 1 of the present invention will be described with reference to FIGS. FIG. 1A is a circuit diagram of a high-frequency semiconductor device according to Embodiment 1 of the present invention, where 1 is a GaAs MODFET.
2 and 3 are 10 pF MIM capacitors connected in series and inserted for protection against electrostatic breakdown, 4 is a gate bias resistor of 2 kΩ,
5 is a signal input terminal corresponding to an external connection terminal (pad), 6 is a gate terminal of 1 and is a terminal to be protected,
A signal output terminal 7 is a drain terminal 1 (another external connection terminal). All of these components of the high-frequency semiconductor device according to the first embodiment are formed on a substrate (not shown). FIG. 1B is a circuit diagram of a high-frequency semiconductor device (chip) for comparison, which is obtained by removing the capacitors 2 and 3 from FIG. 1A. The electrostatic breakdown resistance of FIG. 1B was 18 V when measured between the terminal 6 and the ground using an electrostatic breakdown model (machine model), but it was 5 in the case of FIG. 1A.
The resistance to electrostatic breakdown between the ground and the ground is 40 V, and it can be seen that the electrostatic breakdown resistance is improved by the present invention. This is because, due to the capacitance components of the MIM capacitors 2 and 3, a large time constant is generated in the low frequency component of static electricity and the time applied to the terminal 6 is lengthened. As a result, the instantaneous heat generation amount is reduced. It has improved resistance to electrostatic breakdown. FIG. 2A is a plan view of the capacitors 2 and 3 connected in series in FIG. 1A, and FIG.
FIG. 3 is a cross-sectional view taken along the line AA ′ of FIG. Reference numeral 11 denotes a lower layer metal of the MIM capacitor, which is a Pt film having a thickness of 200 nm and also serves as a connection between 2 and 3.
Reference numerals 2 and 13 are interlayer insulating films of the MIM capacitors 2 and 3, respectively, and SrTiO ₃ films having a thickness of 300 nm.
Reference numerals 14 and 15 are upper metal layers of the MIM capacitors 2 and 3, respectively, and are Au / Ti films having a thickness of 700 nm. When 12 or 13 is used alone, it has a resistance to electrostatic breakdown of 30 V.
It turns out that it has improved to V. The difference in high frequency characteristics between FIG. 1 (a) and FIG. 1 (b) is that NF at 5 GHz is 0.8d in FIG. 1 (a).
In contrast to B, in FIG. 1B, it is 0.9 dB, and it can be confirmed that almost no deterioration has occurred. In this embodiment, GaAs MODFET is used as an element to be protected. However, in a broad sense including GaAs HEMT.
The same effect can be obtained regardless of whether it is a MESFET or a Si MOSFET. Also, the interlayer insulating film of the MIM capacitor is made of S
Although described as rTiO ₃ , the same effect can be obtained with a ferroelectric material such as BaSrTiO ₃ , general silicon oxide, and silicon nitride. In the present embodiment, M having the same capacitance value is used.
Although an example in which two IM capacitors are connected in series has been described, the same effect can be obtained even if they have different capacitance values, or if three or more MIM capacitors are connected in series. (Embodiment 2) Next, a high-frequency semiconductor device according to Embodiment 2 of the present invention will be described with reference to FIG. FIG. 3 is a circuit diagram of the high-frequency semiconductor device according to the second embodiment. Reference numeral 1 denotes an element to be protected by a GaAs MODFET. Reference numerals 2 and 3 denote series-connected elements inserted for protection against electrostatic breakdown. 10 pF capacitor, 5 is a signal input terminal and corresponds to an external connection pad, 6 is a gate terminal of 1 and a terminal to be protected, 7 is a signal output terminal, 1 is a drain terminal and an external connection terminal , 8 are 2 kΩ gate bias resistors. FIG. 1 (a)
Those having the same numbers indicate the same elements and terminals. In the first embodiment, the gate bias voltage of one MODFET is fixed to the ground potential.
It was impossible to change the gate bias voltage from outside the chip. In the present embodiment, the MIM capacitor 2,
3, the gate bias resistor 8 is inserted in parallel, so that the gate bias voltage can be set from the input terminal 5. (Embodiment 3) Next, a high-frequency semiconductor device according to Embodiment 3 of the present invention will be described with reference to FIG. FIG. 4 is a circuit diagram of the high-frequency semiconductor device according to the third embodiment of the present invention, 21 is an element to be protected by GaAs HBT, and 22 and 23 are connected in series inserted for protection against electrostatic breakdown. 10 pF capacitors, 24 is a base bias circuit for supplying a base current to 21 bases, 25 is a signal input terminal corresponding to an external connection pad, 26 is a base terminal of 21 and is a terminal to be protected, A signal output terminal 27 is a collector terminal 21 and an external connection terminal. Also in this embodiment, as described in the first embodiment, the effect of improving the resistance to electrostatic breakdown can be obtained. In this embodiment, GaAs HBT is used, but the same effect can be obtained with SiGe HBT or Si bipolar transistor. By using the high-frequency chip according to the first to third embodiments, for example, a chip that can only be assembled on a class 0 (25 V or lower) line in a machine model can be assembled on a class 1 (25 to 100 V) line. Therefore, it becomes possible to easily assemble, and it is possible to realize a high-frequency semiconductor device and a high-frequency communication device with good high-frequency performance. In the high-frequency semiconductor device, a high-frequency semiconductor chip is sealed in a plastic package or a ceramic package and mounted on a printed circuit board or a ceramic substrate that is a mother substrate, or is mounted on a mother substrate in a bare chip state, And a so-called modular high-frequency semiconductor device in which a high-frequency semiconductor chip and a chip component are mounted on a printed circuit board or a ceramic substrate. According to the present invention, the resistance to electrostatic breakdown can be improved without deteriorating the high frequency performance. In addition, by improving the resistance to electrostatic breakdown, it is possible to easily assemble the package and the motherboard of the communication device, thereby realizing a semiconductor device and a high-frequency communication device with good high-frequency performance.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1A is a circuit diagram of a high-frequency semiconductor device according to a first embodiment of the present invention, and FIG. 1B is a circuit diagram of a high-frequency semiconductor device for comparison. FIG. 3 is a cross-sectional view of the capacitor of the high-frequency semiconductor device according to the first embodiment. FIG. 3 is a circuit diagram of the high-frequency semiconductor device according to the second embodiment of the present invention. FIG. 5 is a circuit diagram of a conventional high-frequency semiconductor device using a protection diode. DESCRIPTION OF SYMBOLS 1 MODFET 2, 3 MIM capacitor 4 Gate bias resistor 5 Signal input terminal 6 Gate terminal 7 Signal output Terminal 8 Gate bias resistor 11 Lower metal 12, 13 Interlayer insulating film 14, 15 Upper metal 21 HBT 22, 23 Capacitor 24 Base bias circuit 25 Signal input terminal 26 the base terminal 27 signal output terminal

──────────────────────────────────────────────────── ----- Continuation of the front page (56) References JP 4-48809 (JP, A) JP 2000-294566 (JP, A) JP 2000-260783 (JP, A) JP 63-224358 ( JP, A) JP 2000-68714 (JP, A) JP 8-274256 (JP, A) JP 2-159753 (JP, A) International Publication 98/012751 (WO, A1) (58) Survey Field (Int.Cl. ⁷ , DB name) H01L 27/04 H01L 27/06 H01L 21/822 H03F 3/54-3/60

Claims (1)

(57) and [Claims 1. A semiconductor substrate, an external connection terminal formed on the semiconductor substrate, or formed on the semiconductor substrate
A semiconductor element connected to said external connection terminals One, the half
A protective element formed on a conductive substrate and connected between the semiconductor element and the external connection terminal;
The element consists only of a series connection of multiple MIM capacitors.
The MIM capacitor has a metal, an insulating film and a metal in front.
A high-frequency semiconductor device characterized by being sequentially laminated on a semiconductor substrate .