JP4160747B2 - Gunn diode and Gunn diode oscillator - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a Gunn diode that reduces damage during mounting and reduces variations in oscillation frequency, oscillation output, and the like, and a Gunn diode oscillator including the Gunn diode.
[0002]
[Prior art]
FIG. 2 shows a conventional Gunn diode 20 for microwave or millimeter wave oscillation. In FIG. 2, 21 is a semiconductor substrate, 22 is a first semiconductor layer, 23 is an active layer, 24 is a second semiconductor layer, 25 is an insulator, 26 is a cathode electrode, 27 is an anode electrode, and 28 is a conductive protrusion. Cathode bumps 29 and 29 are anode bumps with conductive protrusions.
[0003]
The insulator 25 is formed in a cylindrical shape by boron implantation from the upper surface to the boundary between the active layer 23 and the first semiconductor layer 22. The cathode electrode 26 is separated from the anode electrode 27, and the inner side surrounded by the insulator 25 is formed. A functional part of a Gunn diode is formed by the first semiconductor layer 22, the active layer 23 and the second semiconductor layer 24. In FIG. 2, six cylindrical portions are formed by the insulator 25, and Gunn diode function portions are formed below the six cathode electrodes 26. The cathode bumps 28 are formed on all the upper surfaces of the six cathode electrodes 26, respectively. The anode bumps 29 are formed on one side so as to sandwich a group of cathode bumps 28 from both sides of the upper surface of the anode electrode portion. A total of six are formed by three.
[0004]
3 is a view showing a cross section of a Gunn diode oscillator configured by mounting the Gunn diode 20 of FIG. 2 on the microstrip line 30, FIG. 4 is a perspective view of the whole, and FIG. It is a perspective view showing a section. In the microstrip line 30, a signal electrode 32 and two surface ground electrodes 33 are formed on the upper surface of a semi-insulating flat substrate 31 so as to sandwich the signal electrode 32 from both sides, and a back surface ground electrode 34 is formed on the back surface. Then, each front surface ground electrode 33 and back surface ground electrode 34 are made conductive by a via hole 35. The signal electrode 32 is formed with a bias electrode 32A for voltage application, an open stub 32B constituting a resonator, and an output part 32C for extracting oscillation output. The Gunn diode 20 is mounted such that the central cathode bump 28 is bonded to the signal electrode 32 and the anode bumps 29 on both sides are bonded to the surface ground electrodes 33 on both sides. Reference numeral 36 denotes a heat radiation base, which is omitted in FIGS.
[0005]
Conventionally, when the Gunn diode 20 is mounted on the microstrip line 30, the cathode bump 28 of the Gunn diode 20 is used as the signal electrode 32 and the anode bump 29 is used as the surface ground electrode 33 using a thermocompression bonding tool. It was glued.
[0006]
[Problems to be solved by the invention]
However, in this system, the bumps 28 and 29 of the Gunn diode 20 and the electrodes 32 and 33 of the microstrip line 30 are Au-Au thermocompression bonding, and heating (junction temperature) of about 380 ° C. is required. When heat at such a temperature is applied to the diode 20, there is a problem that the resistance increases due to the sintering effect of the ohmic electrode and the oscillation characteristics deteriorate.
[0007]
Therefore, by using a bonding tool that combines heat and ultrasonic waves, the heating temperature is lowered to prevent the deterioration of the characteristics. However, there is a risk that defects such as transition may be induced in the crystal of the Gunn diode chip by the ultrasonic waves. There is. When such a defect occurs, there is a problem that variations occur in the oscillation frequency, oscillation output, etc. of the Gunn diode 20.
[0008]
An object of the present invention is to provide a Gunn diode and a Gunn diode oscillator in which variations in oscillation frequency, oscillation output, etc. do not occur even when using a thermal and ultrasonic bonding system bonding tool. is there.
[0009]
[Means for Solving the Problems]
The invention according to claim 1 is characterized in that one or a plurality of first electrodes are formed in a substantially central portion of one side, a recess or an insulator formed so as to partition a Gunn diode functional part around the first electrode, The first electrode on the one surface and the second electrode formed on the surface excluding the recess or the insulator, the first bump formed by the conductive protrusion formed on the first electrode, and the second electrode In a Gunn diode having a plurality of second bumps formed by conductive protrusions formed so as to sandwich the first bump between electrodes, the total area of the first bump is set to the total area of the second bump. Thus, the Gunn diode is characterized by being set to 0.7% to 20%.
[0010]
The invention according to claim 2 is a semi-insulating flat plate substrate, a signal electrode formed on the surface of the flat plate substrate, and two surface grounds formed so as to straddle a position where an open stub remains at one end of the signal electrode An electrode, a back surface ground electrode formed on the back surface of the flat substrate, a microstrip line having a via hole for conducting the surface ground electrode and the back surface ground electrode, and the signal electrode of the microstrip line A Gunn diode oscillator comprising the Gunn diode according to claim 1, wherein one Gunn bump is adhered, and the second bump is adhered to each surface ground electrode of the microstrip line.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
1A and 1B are views showing a Gunn diode 10 according to one embodiment of the present invention, in which FIG. 1A is a plan view and FIG. 1B is a cross-sectional view. In FIG. 1, 11 is a semiconductor substrate made of N-type gallium arsenide with an impurity concentration of 1-2 × 10 ¹⁸ atm / cm ³ , and 12 is an N-type with an impurity concentration of 2 × 10 ¹⁸ atm / cm ³ and a thickness of 1.5 μm. A first semiconductor layer made of gallium arsenide, 13 has an impurity concentration of 8 × 10 ¹⁵ atm / cm ³ and an active layer made of 1.6 μm N-type gallium arsenide, and 14 has an impurity concentration of 1 × 10 ¹⁸ atm / cm ³ . This is a second semiconductor layer made of N-type gallium arsenide having a thickness of 0.3 μm. 15 is an insulator, 16 is a cathode electrode made of a metal film such as AuGe, Ni, or Au in ohmic contact with the second semiconductor layer 14, 17 is a similar anode electrode, 18 is a cathode bump formed by conductive protrusions, and 19 is the same. This is an anode bump.
[0012]
The insulator 15 is formed in a cylindrical shape by boron implantation from the upper surface to the boundary between the active layer 13 and the first semiconductor layer 12. The cathode electrode 16 is separated from the anode electrode 17, and the inner side surrounded by the insulator 15 is formed. A functional part of a Gunn diode is formed by the first semiconductor layer 12, the active layer 13 and the second semiconductor layer 14. In FIG. 1, six cylindrical portions are formed by the insulator 15, and Gunn diode function portions are formed below the six cathode electrodes 16. Further, the cathode bumps 18 are formed on all the upper surfaces of the six cathode electrodes 26, respectively, while the anode bumps 19 are provided on both corners on one side so as to sandwich a group of cathode bumps 18 from both sides on the upper surface of the anode electrode 17 part. A total of four are formed. The anode bump 19 preferably has a quadrangular shape as shown in the drawing in consideration of alignment using a CCD camera, but is not limited thereto. The area is preferably at least about 100 μm × 50 μm.
[0013]
The area of the active layer 13 corresponding to each cathode electrode 16 partitioned by the insulator 15 is set to a value (lateral area) at which a predetermined operating current of the Gunn diode is obtained. The area of the active layer 13 corresponding to the anode electrode 17 is about 10 to 100 times the area corresponding to the cathode electrode 16, and this portion does not function as a Gunn diode.
[0014]
The Gunn diode 10 can function as a Gunn diode oscillator by being mounted on the microstrip line 30 in the same manner as the conventional Gunn diode 20 shown in FIGS. At this time, a tool using both heat and ultrasonic waves is used as the bonding tool.
[0015]
FIG. 6A shows the relationship between the area ratio of the total area of the cathode bumps 18 to the total area of the anode bumps 19 and the oscillation frequency of 3σ in the Gunn diode oscillator configured by mounting the Gunn diode 10 on the microstrip line 30. FIG. 6B is a characteristic diagram showing the relationship between the same area ratio and 3σ of the maximum oscillation output. Here, the area of the anode bump refers to the area of the portion where the anode bump contacts the anode electrode, and similarly, the area of the cathode bump refers to the area of the portion where the cathode bump contacts the cathode electrode.
[0016]
By setting the area ratio of the total area of the cathode bumps 18 to the total area of the anode bumps 19 to 20% or less, the oscillation frequency 3σ is reduced as shown in FIG. Further, as shown in FIG. 6B, 3σ of the maximum oscillation output is reduced, and the variation of the maximum oscillation output is reduced. That is, even when a tool using both heat and ultrasonic waves is used as the bonding tool, as described above, the area ratio of the total area of the cathode bumps 18 to the total area of the anode bumps 19 is set to 20% or less so that the oscillation frequency is reduced. And variation in maximum oscillation output can be reduced.
[0017]
The lower limit of the area ratio of the total area of the cathode bump 18 to the total area of the anode bump 19 of the Gunn diode 10 is preferably about 0.7%. When the Gunn diode 10 is used as a Gunn oscillator, an oscillation output cannot be obtained unless the cathode electrode 16 has a total area (133 μm ² ) of at least 13 μm in diameter. In this case, the cathode bump 18 needs to have a diameter of about 13 μm in order to dissipate the cathode electrode 16. Therefore, the area having a diameter of 13 μm (133 μm ² ) is the lower limit. If each of the four anode bumps 19 is 100 μm × 50 μm, the total area is 20,000 μm ² . Therefore, the area ratio of the total area of the cathode bump 18 to the total area of the anode bump 19 is 0.66%, which is approximately 0.7%.
[0018]
FIG. 7 is a histogram of the oscillation frequency when a Gunn diode is mounted on the microstrip line 30 to form a Gunn diode oscillator for the 38 GHz band. FIG. 7A shows the Gunn diode 10 of this embodiment, and FIG. This is the case of the conventional Gunn diode 20. In this embodiment, the Gunn diode 10 has an element size of 290 μm × 490 μm, six cathode bumps 18 having a diameter of 28 μm, and four anode bumps 19 having a size of 100 × 50 μm. The conventional Gunn diode 20 has six anode bumps 29 having a diameter of 50 μm, and the other conditions are the same as those of the Gunn diode 10. Here, although the shape of the anode bump is different, the above characteristics are not affected.
[0019]
In the Gunn diode 10 of this embodiment shown in FIG. 7 (a), good results are obtained with an average oscillation frequency of 38.5 GHz and a standard deviation of 0.16 GHz, whereas the conventional Gunn diode of FIG. 7 (b). 20, the average oscillation frequency is 38.3 GHz and the standard deviation is 0.4 GHz.
[0020]
FIG. 8 is a histogram of the maximum oscillation output when a Gunn diode is mounted on the microstrip line 30 and used as a Gunn diode oscillator for the 38 GHz band, and FIG. 8A shows the Gunn diode 10 of this embodiment (FIG. 7A). (B) is the case of the conventional Gunn diode 20 (same conditions as in FIG. 7B).
[0021]
In the Gunn diode 10 of this embodiment shown in FIG. 8A, the average maximum oscillation output is 122.8 mW and the standard deviation is 7.2 mW, whereas the conventional gun diode of FIG. In the diode 20, the average maximum oscillation output is 106.4 mW and the standard deviation is only 18.4 mW.
[0022]
In the Gunn diode 10 according to the embodiment described above, the types and concentrations of impurities in the Gunn diode function part of the semiconductor substrate 11, the first semiconductor layer 12, the active layer 13, and the second semiconductor layer 14 are adjusted. Thus, the cathode electrode 16 can be replaced with an anode electrode, and the anode electrode 17 can be replaced with a cathode electrode. In the Gunn diode 10 of the above embodiment, the insulator 15 is formed by boron implantation. However, the insulator may not be formed, and a recess may be formed therein to partition the Gunn diode functional part.
[0023]
【The invention's effect】
As described above, according to the present invention, even when a Gunn diode oscillator is configured using a tool using both heat and ultrasonic waves, the area ratio of the total area of the first bumps to the total area of the second bumps as described above. By setting the value to 0.7% to 20%, there is an advantage that variations in the oscillation frequency and the maximum oscillation output can be reduced.
[Brief description of the drawings]
FIG. 1 is a view showing a Gunn diode according to an embodiment of the present invention, in which (a) is a plan view and (b) is a cross-sectional view.
2A and 2B are diagrams showing a conventional Gunn diode, in which FIG. 2A is a plan view and FIG. 2B is a cross-sectional view.
FIG. 3 is a cross-sectional view of a conventional Gunn diode oscillator that is mounted on a microstrip line to form a Gunn diode oscillator.
FIG. 4 is a perspective view of a conventional Gunn diode oscillator which is mounted on a microstrip line and constitutes a Gunn diode oscillator.
FIG. 5 is a partially cutaway perspective view of a conventional Gunn diode oscillator that is mounted on a microstrip line and constitutes a Gunn diode oscillator.
6A is a characteristic diagram of the area ratio of the total area of the cathode bump to the total area of the anode bump and 3σ of the oscillation frequency, and FIG. 6B is a characteristic diagram of the area ratio and 3σ of the maximum oscillation output. is there.
7A is a histogram of the oscillation frequency of the Gunn diode oscillator of this embodiment, and FIG. 7B is a histogram of the oscillation frequency of a conventional Gunn diode oscillator.
8A is a histogram of the maximum oscillation output of the Gunn diode oscillator of this embodiment, and FIG. 8B is a histogram of the maximum oscillation output of the conventional Gunn diode oscillator.
[Explanation of symbols]
10: Gunn diode of this embodiment, 11: Semiconductor substrate, 12: First semiconductor layer, 13: Active layer, 14: Second semiconductor layer, 15: Insulator, 16: Cathode electrode, 17: Anode electrode, 18: cathode bump, 19: anode bump 20: conventional Gunn diode, 21: semiconductor substrate, 22: first semiconductor layer, 23: active layer, 24: second semiconductor layer, 25: insulator, 26: cathode Electrode, 27: Anode electrode, 28: Cathode bump, 29: Anode bump 30: Microstrip line, 31: Signal line, 31A: Bias electrode, 31B: Open stub electrode, 31C: Output unit, 32: Surface ground electrode, 33 : Back grounding electrode, 34: Via hole

Claims (2)

One or a plurality of first electrodes formed substantially at the center of one side, a recess or insulator formed so as to partition a Gunn diode functional part around the first electrode, and the first electrode on the one side And the second electrode formed on the surface excluding the recess or the insulator, the first bump formed by the conductive protrusion formed on the first electrode, and the first bump on the second electrode. In a Gunn diode having a plurality of second bumps by conductive protrusions formed to sandwich,
The Gunn diode, wherein a total area of the first bumps is set to 0.7% to 20% with respect to a total area of the second bumps. A semi-insulating flat substrate, a signal electrode formed on the surface of the flat substrate, two surface ground electrodes formed so as to straddle a position where an open stub remains on one end of the signal electrode, The formed back surface ground electrode, the microstrip line having a via hole for conducting each of the front surface ground electrode and the back surface ground electrode, and the first bump is bonded to the signal electrode of the microstrip line, 2. The Gunn diode oscillator according to claim 1, comprising the Gunn diode according to claim 1, wherein the second bump is bonded to each surface ground electrode of the microstrip line.

Images