JPH04330804A - Semiconductor - Google Patents

Abstract

PURPOSE:To enable a transmission in a waveguide mode in a dielectric substrate, and to improve a transmitting characteristic by providing the dielectric substrate forming a microstrip transmission line in a recessed part provided at the bottom face of the inside of a package. CONSTITUTION:The recessed part is provided at the bottom face of the inside of a package 1 made of metal such as copper, an insulating film 6 such as a silicon oxide film, silicon nitride film, or insulating resin is provided at the horizontal face of the upper step of the recessed part so as to surround the recessed part, and an Ni plating layer and an Au plating layer are provided at the surface of the package 1 except for the insulating film 6 so as to be successively laminated. Then, a dielectric substrate 4 whose upper face is formed of a microstrip transmission path 10 and an open stub pattern 11, is adhered and fixed to the bottom face of the recessed part by using an Au and Sn solder, the upper face of the dielectric substrate 4 is made coincident with the horizontal face of the upper step of the recessed part, and the side face of the dielectric substrate 4 is adjacent to a ground face being the side wall of the recessed part.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device, and more particularly to a semiconductor device having a GaAs field effect transistor (hereinafter referred to as GaAsFET) used in an ultra-high frequency band.

0002

2. Description of the Related Art As shown in FIGS. 3 and 4, a conventional semiconductor device having a GaAsFET has a 50Ω internal matching circuit for a GaAsFET chip 7 mounted in a package 1 using capacitance of a chip capacitor 8 and inductance of a thin metal wire 9. It was constructed by providing a lumped constant matching circuit according to the above, and a distributed constant circuit consisting of a microstrip transmission line 10 and an open stub pattern 11 provided on a dielectric substrate 4. Here, the dielectric substrate 4 was mounted on the flat bottom surface of the package 1.

0003

[Problems to be Solved by the Invention] In the conventional semiconductor device described above, the microstrip transmission lines provided on the dielectric substrates on the input and output sides of the matching circuit prevent the propagating electromagnetic waves from interfering with the dielectric. It propagates across free space. In particular, as the frequency increases, the electromagnetic waves radiated from the dielectric substrate into free space increase, and the electromagnetic waves radiated from the microstrip transmission lines of the dielectric substrate provided on the input and output sides also increase. However, they interfere with each other in the free space inside the package.

[0004] Therefore, there has been a problem that the isolation between the input and output of the GaAsFET deteriorates, the matching state in the ultra-high frequency band collapses, and the characteristics deteriorate.

[0005]

[Means for Solving the Problems] A semiconductor device of the present invention includes:
In a semiconductor device having a semiconductor chip mounted in a package, and a microstrip transmission line mounted in the package and connected to an input side and an output side of the semiconductor chip for impedance matching, the microstrip transmission line is formed. A dielectric substrate is embedded in a recess provided on the bottom surface of the package.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be explained with reference to the drawings.

FIGS. 1 and 2 are a cutaway perspective view and a partially sectional view showing an embodiment of the present invention.

As shown in FIGS. 1 and 2, a recess is provided on the inner bottom surface of a package 1 made of metal such as copper, and a silicon oxide film, a silicon nitride film, or an insulating resin is formed around the recess on the horizontal surface above the recess. An insulating film 6 such as Ni plating layer 2 and Au
Plating layers 3 are sequentially laminated. Next, the dielectric substrate 4 on which the microstrip transmission line 10 and open stub pattern 11 are formed on the top surface is bonded and fixed using AuSn solder 5 to the bottom surface of the recess, and the top surface of the dielectric substrate 4 and the horizontal surface of the upper stage of the recess are bonded. At the same time, the side surfaces of the dielectric substrate 4 are brought close to the ground plane, which is the side wall of the recess.

Here, creeping up of the AuSn solder 5 can be prevented by the insulating film 6.

Next, GaAs is applied to the inner bottom of the package 1.
A semiconductor device is constructed by mounting a FET chip 7 and a chip capacitor 8, and connecting the GaAs FET chip 7, chip capacitor 8, and microstrip transmission line 10 with each other using a thin metal wire 9 to form an impedance matching circuit.

[0011]

As explained above, the present invention provides a dielectric substrate on which a microstrip transmission line is formed in the recess provided on the inner bottom surface of the package, thereby bringing the ground plane close to the side surface of the dielectric substrate. A structure is formed in which radiated electromagnetic waves are blocked by the side walls of the recess, improving positional accuracy when fixing the dielectric substrate, and electromagnetic waves entering free space are blocked by the side walls of the recess. In other words, within the dielectric substrate, transmission is performed in a waveguide mode to improve transmission characteristics.

[0012] Therefore, the electromagnetic waves that jump out into free space from the strip transmission line of the dielectric substrate provided on the input side and the output side are suppressed, and mutual isolation between input and output circuits can be guaranteed, and ultra-high frequency bands of 10 GHz or more can be suppressed. Also, it has the effect that stable 50Ω internal matching with little loss can be obtained.

[Brief explanation of drawings]

FIG. 1 is a cutaway perspective view showing one embodiment of the present invention.

FIG. 2 is a partially enlarged sectional view of FIG. 1;

FIG. 3 is a cutaway perspective view showing an example of a conventional semiconductor device.

FIG. 4 is a partially enlarged sectional view of FIG. 3;

[Explanation of symbols]

1 Package 2 Ni plating layer 3 Au plating layer 4 Dielectric substrate 5 Solder 6 Insulating film 7 GaAsFET chip 8 Chip capacitor 9 Fine metal wire 10 Microstrip transmission line 11
open stub pattern

Claims (1)

[Claims] 1. A semiconductor device having a semiconductor chip mounted in a package, and a microstrip transmission line mounted in the package and connected to an input side and an output side of the semiconductor chip for impedance matching,
A semiconductor device characterized in that the dielectric substrate on which the microstrip transmission line is formed is embedded in a recess provided on the bottom surface of the package.