JP2918125B2 - Semiconductor device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an ultra-high frequency semiconductor device such as a Gunn diode used in a millimeter wave band, and more particularly to a semiconductor device package capable of obtaining excellent high frequency characteristics.

BACKGROUND ART In a semiconductor device, a package is indispensable for protecting a semiconductor chip and improving reliability, and a two-terminal semiconductor device used in a microwave band or higher, particularly a gun diode having a large heat generation density, A pill type package having excellent heat dissipation is used as the package.

FIG. 1 is a sectional view schematically showing the structure of a conventional gun diode package. In FIG.
Is Ti on the surface formed on the package body 1 and then A
It is adhered on a diamond heat sink 2 covered with a metal of u. A cylindrical insulator 3 was formed so as to surround the Gunn diode, and the upper portion thereof was plated with gold.
A lid 6 made of Cu is formed as an upper electrode. The Cu lid 6 and the gun diode 4 are electrically connected by the gold ribbon 5. The diamond heat sink 2 serves as a lower electrode, and also serves as a radiator for the gun diode 4 together with the package body 1.

2A to 2C show a method of manufacturing the conventional gun diode package shown in FIG. First, as shown in FIG. 2A, a metal-coated diamond heat sink 2 as a pedestal is attached to the center of a Cu package body 1, and a radiator is formed by the two.

A cylindrical insulator 3 made of alumina or the like is bonded to an upper portion of the package body 1. This insulator 3 is usually called a ceramic ring. The ceramic ring 3 is a diamond heat sink 2 as shown in FIG. 2A.
Is fixed to the package body 1 so as to surround the package body 1. Gun diode 4
Is formed in a mesa type with a plated heat sink (Plated Heat Sink), and is die-bonded to the diamond heat sink 2 by thermocompression bonding or soldering at the portion of the plated heat sink as shown in FIG. 2B. The gun diode 4 has upper and lower electrodes formed thereon, and the pedestal portion 2 formed of a diamond heat sink also serves as a lower electrode. Next, as shown in FIG. 2C, the upper electrode of the Gunn diode 4 is connected via a gold ribbon 5 to a metal coating formed on the upper end surface 8 of the ceramic ring 3. Finally, as shown in FIG.
Is sealed using a Au-Sn (20%) eutectic alloy or the like with a lid 6 made of gold-plated Cu and used as upper electricity to complete the package of the gun diode 4.

However, for example, E-band (60 to 90 GHz), V-band
(40-75 GHz), W-band (75-110 GHz) or more, as the millimeter-wave band device operating in the ultra-high frequency band is developed, the inductance L of the gold ribbon 5 in the package, the lid 6 and the package body, The formed capacitance C greatly affects the characteristics.

As a method of reducing the inductance L of the gold ribbon in the package, an improved package as shown in FIG. 3A disclosed in Japanese Patent Application Laid-Open No. Hei 5-16728 is known.
In FIG. 3A, the distance (height difference) Δ between the upper part of the gun diode 4 and the upper end part of the insulator 3 is set to be three times or more and ten times or less the thickness of the gold ribbon 5 so that the length of the gold ribbon 5 is increased. And the inductance L is reduced. Figure 3B is thickness
When a gold ribbon 5 having a width of 15 μm and a width of 100 μm is used, the height difference Δ shown in FIG.
The band characteristics of each sample at μm (characteristic line b) and 100 μm (characteristic line c) are shown. The mount and the resonator have the same conditions. For a sample with a height difference Δ of 300 μm, the oscillation frequency is 85-9
In contrast to 0 GHz, the sample with a height difference of 100 μm had an oscillation frequency of 95-100 GHz, and the output was Δ = 300 μm.
It turns out that it becomes 1.3 times or more compared with the sample of m.

However, reducing only the inductance L is not enough to obtain excellent high-frequency characteristics such as high output in a high frequency band of 700 GHz or more. That is, the larger the value of the parasitic capacitance C of the package, the longer it takes to charge and discharge the parasitic capacitance C. The parasitic capacitance C of the millimeter-wave band device operating in the V-band, W-band or higher ultra-high frequency band. It slows down the operation.
In particular, in the conventional package structure, since the insulator is sandwiched by the ceramic ring 3 formed of alumina having a relatively large dielectric constant, the value of the capacitance C is considerably large, and the performance inherent in the element is sufficiently improved. I found out that I could not withdraw. For this reason, it has been attempted to improve the high-frequency performance by using a package using a quartz ring having a dielectric constant smaller than that of alumina instead of the alumina ceramic ring generally used as the insulator 3. However, quartz has a low compressive strength and a low tensile strength as compared with alumina, and therefore has a problem that cracks are easily formed when brazing to a Cu package body.

DISCLOSURE OF THE INVENTION Accordingly, an object of the present invention is to provide a semiconductor device having good high-frequency characteristics even in a millimeter wave band of 90 GHz or more. In particular, it is an object of the present invention to provide a semiconductor device in which high-frequency characteristics are improved by sufficiently reducing a parasitic capacitance C of a package, and high reliability and sufficient heat dissipation are realized.

In order to solve the above problem, the present invention provides a heat radiator 1, a semiconductor element 9 having one main surface (lower surface) fixed to the heat radiator 1, and a hollow portion surrounding the semiconductor element 9 as shown in FIG. 4A. One end surface (lower end surface) 7 of the hollow portion is in contact with the radiator 1 and the other end surface (upper end) 8 is separated from the radiator by a predetermined distance from the other main surface (upper surface) of the semiconductor element 9. A cylindrical insulator 3, a metal foil 5 for connecting the other end surface (upper end surface) 8 of the insulator 3 to the upper surface of the semiconductor element 9, and an insulator which is alloyed with the metal foil 5. And a lid 6 attached to the other end surface (upper end surface) of the insulator 3 to seal the hollow portion, and the thickness of the insulator 3 is not less than 0.08 mm and not more than 0.14 mm. For example, alumina or the like may be used as the insulator. Here, the thickness of the insulator refers to the thickness in the radial direction defined by (ab) / 2 when the outer diameter of the insulator is a and the inner diameter is b. If the thickness of the insulator in the radial direction is less than 0.08 mm,
It is not preferable to make the thickness less than 0.08 mm because cracks occur at the time of brazing and welding of the insulator and the yield decreases. In particular, in order to further improve the reliability of the device, the thickness of the insulator 3 is preferably 0.1 mm or more in consideration of the strength of the material of the insulator. Here, the semiconductor element 9 includes a pedestal portion 2 such as a diamond heat sink and a millimeter-wave device chip 4 such as a compound semiconductor on the pedestal portion 2. As the millimeter wave element chip 4, a Gunn diode is particularly preferable.

Since the insulator 3 has a structure surrounding the semiconductor element 9, the inner diameter b of the insulator 3 is not less than 0.35 mm and not more than 0.5 mm in consideration of the size (0.3 mmφ) of the pedestal 2. It is preferred that

The semiconductor element 9 has electrodes (upper electrodes and lower electrodes) on both main surfaces. The radiator 1 is made of metal or the like,
One electrode (lower electrode) of the semiconductor element 9 is connected.
The metal foil 5 is made of Au and has a thickness of 5 to 20 μm. Lid 6
Is made of a metal, alloyed with a eutectic alloy of Au such as Au-Sn, and attached to the other end face (upper end face) 8 of the insulator.
It is needless to say that the distance (difference in height) Δ from the upper surface of the millimeter wave element chip 4 to the upper end surface of the insulator 3 is preferably not less than 3 times and not more than 10 times the thickness of the metal foil 5.

By setting the thickness of the cylindrical insulator 3 to be 0.08 mm or more and 0.14 mm or less as shown in FIG. 4A, the area of the upper end face and the lower end face of the insulator 3 is reduced, and as a result, the lid 6 and the radiator 1 The area of the capacitance C formed by the above can be reduced. Further, by reducing the value of the capacitance C, excellent high-frequency characteristics can be obtained. Further, since one main surface (lower surface) of the semiconductor element 9 is fixed to the heat radiator 1, sufficient heat radiation can be obtained. Also,
Since the lid 6 is attached to the upper end surface 8 of the insulator 3 by alloying, high reliability can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view showing the structure of a conventional Gunn diode package.

2A to 2C are views showing a method for manufacturing the conventional gun diode package shown in FIG.

FIG. 3A is a cross-sectional view showing the structure of a conventional improved package, and FIG. 3B is a diagram showing its characteristics together with a comparative example.

4A and 4B are longitudinal sectional views showing the structure of a gun diode package according to an embodiment of the present invention.

FIG. 5 is a diagram showing an oscillation frequency-output characteristic of the example of the present invention together with a comparative example.

BEST MODE FOR CARRYING OUT THE INVENTION The embodiment of the present invention shown in FIGS. 4A and 4B relates to a case where an InP gun diode is used as a millimeter wave element chip 4.
That is, in a millimeter-wave semiconductor device typified by a Gunn diode, a novel structure and conditions are provided that enable the value of the parasitic capacitance C formed between the package lid and the heat radiator of the package body to be reduced. Is what you do.

FIG. 4A is an enlarged sectional view of a portion A in FIG. 4B. The figure
In FIGS. 4A and 4B, the same or equivalent members as those in FIGS. 1, 3A and the like described above are denoted by the same reference numerals, and redundant description will be omitted.

In FIG. 4A, one end face 7 (lower end face) of a ceramic ring 3 made of alumina, which is an insulator formed in a cylindrical shape.
Are fixed to the heat radiator 1 of the package body. The Gunn diode 4 as a millimeter wave element chip is 40 to 60 μmφ, has electrodes on both upper and lower surfaces, and is manufactured in a mesa type with a 0.3 mmφ plated heat sink. The lower surface of the gun diode 4 is die-bonded on a diamond heat sink whose surface as the pedestal portion 2 is coated with a metal made of Ti and then Au by thermocompression bonding or soldering at a portion of a plated heat sink. Since the gun diode 4 is directly fixed on the diamond heat sink 2, the heat generated by the gun diode 4 can be sufficiently released. On the other hand, the distance between the upper surface of the Gunn diode 4 and the upper end surface 8 of the ceramic ring 3 is 50 μm to 150 μm.
By setting the thickness to μm, the length of the metal foil 5 connecting the upper end portion 8 of the ceramic ring 3 and the upper electrode of the Gunn diode 4 is adjusted, and the value of the inductance L of the metal foil 5 becomes too large. The characteristics are not affected.
The connection between the upper electrode of the Gunn diode 4 and the metal coating on the upper end face 8 of the ceramic ring 3 is made in a W-band (75 to 110 GHz).
In z), a gold ribbon 5 generally made of metal foil having a thickness of 10 to 15 μm and a width of about 100 μm is used. That is, the distance (difference in height) between the upper surface of the gun diode 4 and the upper end surface 8 of the ceramic ring 3 is selected to be about 10 times or less the thickness of the gold ribbon 5. On the upper end surface 8 of the ceramic ring 3, a lid 6 made of gold-plated Cu is sandwiched between the Au-
It is fixed with a Sn-based eutectic alloy. By alloying,
The lid 6 is securely brought into close contact with the upper end surface 8 of the ceramic ring 3. However, if this distance (difference in height) is too short, the thickness of the gold ribbon 5 is 10 to 15 μm and its deflection is 10 to 20 μm.
Since the gap between the cover 6 and the cover 6 is reduced by m, the eutectic solder (Au-Sn) used for sealing the cover 6 flows into the gold ribbon 5 side, and the quality of the gold ribbon 5 becomes hard, and the gold ribbon 5 is pulled or shifted to the gun diode chip. Since the reliability of the apparatus may be impaired due to the application of such stress, it is preferable that the distance (the height difference) be at least three times the thickness of the gold ribbon.

Next, characteristics of the millimeter wave package of the present invention shown in FIGS. 4A and 4B are shown in FIG. The output characteristic shown in FIG. 5 is a case where a Gunn diode designed to oscillate at 94 GHz is used, and for comparison, a case under a condition different from the best embodiment of the present invention is also shown. That is, by changing the area of the end face of the ceramic ring 3 for two cases of the embodiment of the present invention and two cases of the comparative example in total,
It is a result of an oscillation experiment when the value of the parasitic capacitance C formed between the lid 6 and the heat radiator 1 of the package body is changed. More specifically, it is an experimental result when a package is formed by changing the area of the end face of the ceramic ring 3 by changing the combination (a, b) of the outer diameter a and the inner diameter b of the ceramic ring 3. Here, as a comparative example of the high frequency characteristics, the combination (a, b) of the outer diameter a and the inner diameter b is (0.78 mm, 0.4 mm)
And 0.77 mm, 0.46 mm), (0.73 mm, 0.46 mm) in the first embodiment of the present invention, and (0.75 mm, 0.50 mm) in the second embodiment. That is, the thickness ((ab) / 2) of the ceramic ring 3 of the comparative example was 0.19 mm and
The thickness of the ceramic ring 3 of the first and second embodiments of the present invention is 0.135 mm and 0.125 mm, respectively.
By changing to, the high frequency characteristics are shown.

In the first and second embodiments of the present invention, the inner diameter a of the ceramic ring 3 is preferably not less than 0.35 mm and not more than 0.5 mm so that the semiconductor element 9 can be put in the ceramic ring 3. is necessary. If the thickness exceeds 0.5 mm, the value of the inductance L of the metal foil 5 connecting the upper end surface 8 of the ceramic ring 3 and the upper electrode of the Gunn diode 4 increases, and the oscillation frequency decreases.
It cannot exceed 0.5mm.

As shown in FIG. 5, the thickness of the ceramic ring 3 ((a−
b) / 2), that is, in the first and second embodiments of the present invention in which the areas of the upper end face and the lower end face of the ceramic ring 3 are small, the high frequency characteristics are improved as compared with the comparative example in which the area of the end face is large. You can see that it is doing.

In the measurement of the high frequency characteristics shown in FIG. 5, it is a matter of course that the four types of samples have the same conditions for the mount and the resonator. The thickness of the comparative ceramic ring 3 is 0.15 mm
(A = 0.77mm, b = 0.46mm), the oscillation frequency is 81
Thickness of 0.135mm (a = 0.73mm, b
= 0.46 mm), the sample of the first example of the present invention has an oscillation frequency of 89 to 99 GHz. Further, it can be seen that the oscillation frequency is 94 to 100 GHz in the second embodiment of the present invention in which the thickness is 0.125 mm (a = 0.75 mm, b = 0.50 mm). However, if the thickness ((ab) / 2) of the ceramic ring 3 is less than 0.08 mm, the mechanical strength is weakened due to slack when the ceramic ring 3 is brazed (welded), etc. May be compromised. In order to ensure the reliability of the device, it is necessary that the thickness is 0.08 mm or more, preferably 0.1 mm or more.

The above results are examples, E-band (60-90 GHz), F
Similarly, in the case of -band (90 to 140 GHz), the high frequency characteristics of the same structure as those of the first and second embodiments of the present invention were recognized as compared with the comparative example. The same applies to other millimeter-wave elements such as GaAs gun diodes as well as InP gun diodes.

Therefore, from the above results, the radial thickness of the insulator is 0.
By setting the thickness to 08 mm or more and 0.14 mm or less, excellent high-frequency characteristics can be obtained.

INDUSTRIAL APPLICABILITY As described above, in the semiconductor device according to the present invention, by setting the thickness (ab) / 2 of the cylindrical insulator to 0.08 mm or more and 0.14 mm or less, the end face of the insulator (top The area of the end surface and the lower end surface is reduced, the value of the parasitic capacitance C formed between the lid and the heat radiator of the package body is reduced, and the distance between the upper surface of the semiconductor element and the upper end surface of the insulator is reduced. , The parasitic inductance L is small, and excellent high-frequency characteristics can be obtained even in the millimeter wave band of 90 GHz or more. further,
In the semiconductor device according to the present invention, one main surface (lower surface) of the semiconductor element is fixed to the radiator, so that sufficient heat radiation can be obtained. Further, in the semiconductor device according to the present invention, since the lid is attached to the upper end surface of the insulator by alloying, high reliability can be obtained.

Continuation of front page (56) References JP-A-55-75247 (JP, A) JP-A-50-44954 (JP, A) JP-A-49-137345 (JP, A) (58) Fields studied (Int .Cl. ⁶ , DB name) H01L 23 / 02,23 / 36,47 / 02

Claims (8)

(57) [Claims] 1. A heat radiator, a semiconductor element fixed to an upper part of the heat radiator, a hollow cylindrical insulator surrounding the semiconductor element and having a lower end surface in contact with the heat radiator, A metal foil for connecting the end face and the semiconductor element, and a lid which is in contact with a part of the metal foil and is formed on an upper portion of the insulator and seals a hollow portion of the insulator; A semiconductor device having a thickness measured in a radial direction of a body of 0.08 mm or more and 0.14 mm or less. 2. The semiconductor device according to claim 1, wherein said semiconductor element comprises at least a pedestal portion and a millimeter-wave device chip formed on an upper portion of said pedestal portion and having a lower surface in close contact with said pedestal portion. Semiconductor device. 3. The semiconductor device according to claim 2, wherein said millimeter wave element chip is made of a compound semiconductor. 4. The semiconductor device according to claim 2, wherein said millimeter wave element chip is a Gunn diode. 5. The semiconductor device according to claim 2, wherein said pedestal is a diamond heat sink. 6. The semiconductor device according to claim 1, wherein said lid is alloyed with a part of said metal foil and fixed to an upper end surface of said insulator. 7. The metal foil is a gold ribbon, and the lid is made of Au.
7. The semiconductor device according to claim 6, wherein the semiconductor device is alloyed with a Sn-based eutectic alloy and is fixed to an upper end surface of the insulator. 8. The method according to claim 1, wherein a distance between an upper surface of said semiconductor element and an upper end surface of said insulator is not less than 3 times and not more than 10 times a thickness of said metal foil. Semiconductor device.