JPH11233850A - Method for manufacturing semiconductor device - Google Patents

Abstract

[PROBLEMS] To provide a method of manufacturing a semiconductor device which is easy to manufacture and assemble. SOLUTION: A semiconductor substrate is bonded to a support plate to expose an anode layer. A mask film is formed on the anode layer, and a portion excluding a region where a semiconductor device is to be formed is removed by etching to form a concave portion. After the mask film is removed, the concave portion is filled with low-melting glass so as to surround the region where the semiconductor device is to be formed. Forming an anode electrode and a cathode electrode connected to the anode layer and the cathode layer in the semiconductor device formation planned region, cutting a low melting point glass portion between the semiconductor devices,
Complete the semiconductor device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for manufacturing a semiconductor device used as an oscillator in a millimeter wave band.

[0002]

2. Description of the Related Art In recent years, applications of radio waves in the millimeter wave band have been actively performed. For example, an attempt has been made to measure the distance between vehicles with a millimeter-wave Doppler radar to avoid collisions and rear-end collisions, or to detect a collision from the side in advance and activate an airbag to ensure safety. I have. In addition, communication using millimeter waves does not require facilities such as conducting wires and optical fibers, and thus has already been partially used. Further, since the millimeter wave is strong against rainfall and snowfall and has high directivity, it is effective as a communication medium having a wide range of use.

[0003] Gunn diodes, in-pad diodes, H
EMT and the like. Of these, Gunn diodes are the most widely used.

A Gunn diode is a bulk oscillation device using an electronic transition effect, and therefore has little influence of surface states. Therefore, it has the least 1 / f noise among compound semiconductors and a constant frequency output like a Doppler radar. It has a particularly significant advantage when it is needed.

A gun diode for millimeter waves is usually made of a compound semiconductor such as gallium arsenide or indium phosphide, and has a low electric field mobility of several thousand cm 2 / V · s.
ec and large. However, when a higher electric field is applied, the accelerated electrons transition to a band having a large effective mass, and the mobility is reduced. Such a mechanism causes a negative differential mobility in the bulk, resulting in a negative differential conductance of the current-voltage characteristic, and a thermodynamic instability. Therefore, a domain is generated, and the domain travels from the cathode side to the anode side. As a result of repeating this, current oscillation is obtained.

The oscillation frequency is determined by the distance traveled by this domain. In the case of a millimeter-wave gun diode, this traveling space must be extremely short, such as 1 to 2 microns. In addition, the n-type impurity concentration in the traveling space of the domain is as high as 10 ¹⁶ atoms / cm 3. Since electrons move in a traveling space having a short distance and a small resistance as described above, the operating current increases unless the traveling space is reduced. In a millimeter-wave gun diode, the size of the element, including the traveling space, must be 10
It must be formed as extremely small as about a micron diameter.

Further, even if the size of the element is small, the operating current becomes as large as several hundred milliamps, so that it is necessary to provide a structure having good heat radiation efficiency.

A conventional millimeter-wave gun diode has been assembled as follows in order to improve heat radiation efficiency. First, a gun diode element 13 large enough to be assembled.
To form At this time, the current-voltage characteristic of the gun diode element 13 is set to be larger than a predetermined set value.
Thereafter, it is assembled into a pill type package as shown in FIG. In the pill type package, a glass or ceramic cylinder serving as an envelope 15 is hard brazed so as to surround the radiation base electrode 14.

The Gunn diode element 13 is electrostatically attracted to a sapphire column or the like and adheres to the radiator base electrode 14. At this time, the sapphire pillar blocks the visual field, and the radiation base electrode 14
It is difficult to visually recognize the image directly, and the working efficiency is very poor.

Further, wiring is performed on the gun diode element 13 with a gold ribbon 17 through a quartz pedestal 16 provided with a metal layer of CrAu or the like on the surface, and gold is again applied to the metal layer provided at the tip of the envelope 15. It is necessary to perform wiring by the ribbon 17, and there is a problem that work efficiency is very poor.

After assembling in this manner, the entire package is immersed in an etching solution to dissolve only the portion constituting the Gunn diode element 13, such as GaAs, to reduce the area of the active region. The fact that the area has been reduced to the predetermined area can be known from the decrease in the current value. Therefore, it is necessary to repeat the process of measuring the current-voltage characteristics after performing the etching until the current decreases to a predetermined value.

When a predetermined current value is reached, the envelope 1
5. A lid-shaped metal disk (not shown) is brazed on 5,
Assembly of the pill type package is completed.

[0013]

As described above, the conventional millimeter-wave semiconductor device has many problems in terms of manufacturing and assembling, many factors that lower the yield, and has a problem that the cost is increased. Was. An object of the present invention is to solve the above problems and to provide a method of manufacturing a semiconductor device which is easy to manufacture and assemble.

[0014]

According to the present invention, in order to achieve the above object, one main surface and another main surface of a semiconductor substrate are provided.
In a method of manufacturing a semiconductor device in which first and second electrodes are respectively formed, a step of preparing a semiconductor substrate having a support means and exposing one main surface; and a step of preparing a semiconductor substrate excluding at least a region where a semiconductor device is to be formed. A step of forming a concave portion reaching another main surface by etching away a part from one main surface side, and filling the concave portion with an insulator so that the insulator surrounds at least a region where the semiconductor device is to be formed Forming a first electrode connected to the one main surface of the semiconductor substrate in a region where a semiconductor device is to be formed; removing the supporting means; exposing another main surface of the semiconductor substrate. Forming another support means to:
Forming the second electrode connected to the other exposed main surface.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to a method of manufacturing a Gunn diode.
A semiconductor substrate made of gallium arsenide, indium phosphide, or the like is prepared. This semiconductor substrate includes an anode layer 1 composed of a buffer layer formed on a high-concentration n-type substrate, a domain running layer 2 composed of a low-concentration n-type region, and a cathode layer 3 composed of a high-concentration n-type region. On the surface of the cathode layer 3,
A first insulating film 4 made of a nitride film or the like is formed by a known CVD method or the like. Next, a support plate 5 for handling is adhered on the insulating film 4. This support plate 5 may use the same semiconductor substrate as the semiconductor substrate.

Thereafter, the semiconductor substrate is polished from the side of the anode layer 1 and then subjected to chemical mechanical polishing or chemical polishing to reduce the thickness of the semiconductor substrate to a predetermined thickness (about 50 microns). A semiconductor substrate is used (FIG. 1). A film 6 serving as an etching mask, such as a photoresist or a nitride film, is formed on the surface of the anode layer 1 of the mirror-finished semiconductor substrate so as to cover a region where a gun diode is to be formed. Thereafter, the semiconductor substrate is etched to leave the region where the Gunn diode is to be formed, exposing the first insulating film 4 and forming the concave portion 7 (FIG. 2). FIG. 2 is a cross-sectional view showing a case where a gun diode forming region is formed in a donut shape in order to enhance the heat radiation effect of the gun diode element. The gun diode formation region formed here has a size that does not require an area adjustment by etching later as in the related art.

Next, the film 6 is removed, and a second insulating film made of a silicon film, an amorphous silicon film, or a nitride film is formed on the surface of the semiconductor substrate on the side of the anode layer 1 where the concave portions 7 are formed, by CVD or sputtering. 8 is formed in a single layer or a multilayer. Thereafter, the low melting point glass powder is filled into the concave portion 7 by a well-known method such as a centrifugal method or a dokuda blade method, and is melted or sintered to be solidified (FIG. 3). The solidified low melting point glass 9 can be brought into close contact with the semiconductor substrate through the insulating film 8. Thus, the semiconductor substrate in the region where the gun diode is to be formed has a structure surrounded by the solidified low-melting glass 9. Since the melting point or the sintering temperature of the low melting point glass can be set lower than the epitaxial growth temperature, the characteristics of the Gunn diode are not impaired in the solidification step of the low melting point glass. Further, the heat treatment for melting and solidifying the low melting glass is performed with the surface coated with the low melting glass facing upward. You.

After that, the low-melting glass 9 and the second insulating film 8 are polished and removed to expose the surface of the anode layer 1. By this polishing, the height of the solidified low-melting glass 9 and the surface of the anode layer 1 are made substantially the same. Note that the entire low-melting glass fixed in the recesses 7 is not necessarily the anode layer 1.
The height of the central portion of the concave portion 7 may not be equal to the height of the surface. What is necessary is just to become. However, in order to simplify the step of forming the anode electrode and the step of connecting the gold ribbon to the anode electrode, it is preferable that the height of the entire low-melting glass is equal to the height of the surface of the anode layer. With this structure, the side surface of the semiconductor substrate in the region where the gun diode is to be formed is surrounded by the low-melting glass 9. On the exposed anode layer 1 surface,
An electrode metal is deposited to form an anode electrode 10 in ohmic contact with the anode layer 1 (FIG. 4). Here, before depositing the electrode metal, etching may be performed to clean the exposed surface of the anode layer 1.

The support plate 5 adhered to the surface of the first insulating film 4 on the cathode side is removed, and the surface of the anode electrode 10 is removed.
Another handling support plate 11 is bonded with wax or the like. The first insulating film 4 is removed by etching to expose the cathode layer 3. Exposed cathode layer 3 and second
An electrode metal is deposited on the surface of the insulating film 8 to form a cathode electrode 12 in ohmic contact with the cathode layer 3 (FIG. 5). Thereafter, the adhesive of the support plate 11 is dissolved and removed, and the semiconductor substrate is bonded to a dicing tape by a known cutting method, and the low melting point glass 9 between the gun diode elements is cut and diced to form a dice. It is completed (FIG. 6).

The gun diode formed in this manner is assembled to a radiation base electrode. Since the gun diode chip of the present invention has a structure in which the periphery is surrounded by the low-melting glass 9, the low-melting glass plays a role of an envelope of the conventional pill-type package. Therefore, it is possible to assemble the conventional pill-type package without requiring the envelope, and it is possible to solve the problem of the space limitation of the envelope which has been a problem in the past.

In the above description, the process of forming a Gunn diode by forming a first insulating film on the surface of a semiconductor substrate and adhering it to a support plate 5 has been described. The insulating film and the supporting plate are not limited to those described above. For example, if a semiconductor substrate on which another thick semiconductor layer is integrally formed is used, the step of bonding the support plate can be omitted.

The present invention is not limited to Gunn diodes, but can be applied to various types of diodes such as PIN diodes, varactor diodes, and in-pad diodes, and composite devices.

[0023]

As described above, the semiconductor device formed by the manufacturing method of the present invention does not suffer from the spatial restrictions of the existing envelope, so that automatic assembly becomes possible, and the cost is significantly reduced. There is. Further, since it is not necessary to use the heat-dissipating base electrode with the envelope which has been conventionally used, the effect of cost reduction is great also in this regard.

Further, since there is no need to perform etching for adjusting the current value after assembling, there is also an effect that the manufacture can be performed more easily.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of an embodiment of the present invention.

FIG. 2 is an explanatory diagram of an embodiment of the present invention.

FIG. 3 is an explanatory diagram of an embodiment of the present invention.

FIG. 4 is an explanatory diagram of an embodiment of the present invention.

FIG. 5 is an explanatory diagram of an embodiment of the present invention.

FIG. 6 is an explanatory diagram of an embodiment of the present invention.

FIG. 7 is an explanatory view of a conventional semiconductor device of this type.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 anode layer 2 domain running layer 3 cathode layer 4 first insulating film 5 support plate 6 film 7 recess 8 second insulating film 9 low melting point glass 10 anode electrode 11 support plate 12 cathode electrode 13 gun diode element 14 heat radiation base Electrode 15 Envelope 16 Quartz pedestal 17 Gold ribbon

Claims (1)

[Claims] 1. A method of manufacturing a semiconductor device, wherein a first electrode and a second electrode are formed on one main surface and another main surface of a semiconductor substrate, respectively. Preparing at least a portion of the semiconductor substrate except for a region where a semiconductor device is to be formed by etching from one main surface side to form a recess reaching another main surface; and at least forming the semiconductor device. Filling the recess with an insulator so that the insulator surrounds the planned region; forming the first electrode connected to the one main surface of the semiconductor substrate in the semiconductor device formation planned region; Removing the supporting means, forming another supporting means for exposing another main surface of the semiconductor substrate, and forming the second electrode connected to the another main surface being exposed; The method of manufacturing a semiconductor device, which comprises.