JP4336071B2 - Semiconductor device with excellent heat dissipation - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor device having excellent heat dissipation, and more specifically, because of its excellent heat dissipation, it is possible to drive a large current, and a field effect transistor (FET), bipolar transistor (BJT), heterojunction bipolar transistor (HBT). ), A thyristor, an insulated gate bipolar transistor (IGBT), a gate turn-off transistor (GTO), a Schottky diode, a p (i) n junction diode, and the like.
[0002]
[Prior art]
GaN-based semiconductor materials such as GaN, InGaN, and AlInGaN have a large band gap energy, high heat resistance, excellent high-temperature operation, and high-frequency operation compared to, for example, GaAs-based materials. Research and development of GaN-based FETs is underway using materials.
[0003]
For example, a GaN-based FET structure is formed as follows. First, a buffer layer made of GaN is formed on a crystal growth substrate made of sapphire by applying a metal organic chemical vapor deposition method (MOCVD method) or a gas source molecular beam epitaxial growth method (GSMBE method).
Next, an undoped GaN layer having a thickness of about 2 μm is formed on the buffer layer, and an n-GaN layer having a thickness of about 20 nm that functions as an active layer is formed thereon by using, for example, Si as an n-type dopant. To make a slab layer structure.
[0004]
Next, after forming a SiO ₂ film on the surface of the slab layer structure by, for example, plasma CVD, patterning is performed by applying photoresist and chemical etching, and the surface of the undoped GaN layer is used for a source electrode and a drain electrode. Are formed, and an opening for a gate electrode is formed on the surface of the n-GaN layer.
[0005]
Finally, for example, Ti or Al is vapor-deposited at the opening portions for the source electrode and the drain electrode to form the source electrode and the drain electrode, and at the opening portion for the gate electrode, for example, Pt, Au, A gate electrode is formed by evaporating Pd or the like to form an FET structure.
Therefore, the above-described FET is formed with three operating electrodes including a source electrode, a drain electrode, and a gate electrode protruding on the surface, and the entire back surface side is thicker than each semiconductor layer. It is composed of a sapphire substrate.
[0006]
[Problems to be solved by the invention]
The FET described above generates heat during current driving. In particular, when a large current is driven, the amount of generated heat increases, and the FET temperature rises considerably. However, in the above-described FET, most of the thickness is occupied by a sapphire substrate having a low thermal conductivity, so that the heat dissipation is extremely poor.
[0007]
Therefore, heat is accumulated in the GaN-based semiconductor and raises its temperature. In the worst case, the FET structure may be lost due to thermal destruction of the GaN-based semiconductor.
Therefore, in the case of the above-described FET, in order to realize a large current drive, it is unavoidable to form a structure with excellent heat dissipation.
[0008]
An object of the present invention is to solve the above-described problems and to provide a semiconductor device having a structure excellent in heat dissipation, that is, a structure capable of driving with a large current.
[0009]
[Means for Solving the Problems]
To achieve the above object, in the present invention, said surface having a plurality of working electrode on the surface of the semiconductor devices formed on the crystal growth substrate is formed to receive at least the working electrode to the surface and said surface of the radiating board which recess is formed, the semiconductor device is provided, wherein formed isosamples bonded via an insulating film.
[0010]
In this case, it is preferable that the insulating film is made of a material having good thermal conductivity such as Al or diamond, and the heat dissipation substrate is made of Cu or Al.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows an example A of the semiconductor device of the present invention when the semiconductor device is an FET.
The semiconductor device A is radiating substrate A ₂ to be described later as with the semiconductor device A ₁ to be described later is bonded via the insulating film 9, and the crystal growth substrate 1 used at the time of fabrication of the semiconductor device A ₁ is off structure It has become.
[0012]
An operating electrode composed of a source electrode S, a gate electrode G, and a drain electrode D is formed to protrude on the junction side surface of the semiconductor device A ₁ , and at the same time, the remaining surface is covered with, for example, a SiO ₂ film 6. .
On the other hand, the bonding side surface of the heat dissipation substrate A ₂ has an uneven shape in a negative-positive relationship with the bonding side surface of the semiconductor device A ₁ . Specifically, at least a surface portion corresponding to the position of the working electrode is formed with a concave portion 8a which is similar to the shape of the working electrode in surface view and is slightly larger.
[0013]
An insulating film 9 is interposed at least at a position where the working electrode is located on each bonding side surface of the semiconductor device A ₁ and the heat dissipation substrate A ₂ , so that the working electrodes are insulated from each other. ing.
Therefore, in the case of the semiconductor device A, the semiconductor device A ₁ is removed sapphire substrate 1 poor heat dissipation, and since the surface of the working electrode positioned heat dissipation substrate A ₂ are bonded, as a whole heat dissipation The property is excellent. That is, it is possible to perform a large current drive that generates a large amount of heat.
[0014]
This semiconductor device A can be manufactured as follows.
First, fabrication of a semiconductor device will be described.
As shown in FIG. 2, a buffer layer 2 made of, for example, GaN, an active layer 4 made of, for example, undoped AlGaN, and an Si-doped n−, for example, are formed on a sapphire substrate 1 that is a substrate for crystal growth. fabricating a slab layer structure a ₁ -1 are sequentially formed a contact layer 5 made of GaN.
[0015]
Then, the surface of the slab layer structure A ₁ -1, for example, a thermal chemical deposition method to form a SiO ₂ film, the SiO ₂ film in a photolithography and dry etching, the active layer for forming the gate electrode 4 After the surface 4a is exposed, the SiO ₂ film is completely removed, and an intermediate A _1-2 is produced as shown in FIG.
Next, the SiO ₂ film 6 is formed again on the entire surface of the intermediate A _1-2 . Then, the process proceeds to formation of the working electrode.
[0016]
First, wet etching using photolithography and hydrofluoric acid is performed on the SiO ₂ film 6 on the contact layer 5 to form openings for the source electrode and the drain electrode to expose the surface of the contact layer 5. Thereafter, Al, Ti, and Au are sequentially deposited thereon by sputtering, for example, to form a source electrode S and a drain electrode D having a predetermined shape that are in ohmic contact with the contact layer 5. Further, for example, an electrode may be formed by depositing an ohmic electrode material such as Ta—Si by a vacuum evaporation method.
[0017]
Next, after the surface is lifted off, an opening is formed in the SiO ₂ film 6 where the gate electrode is to be formed in the same manner as described above, and then the gate electrode G is formed there. As a constituent material of the gate electrode G, for example, Ni, Pt, Pd, Ti, Au, W, Ta, a combination of these materials, a silicide-based alloy containing Si, or the like can be used.
[0018]
In this way, as shown in FIG. 4, the GaN-based FET A _1-3 that is the base material of the semiconductor device A ₁ shown in FIG. 1 is obtained. On the surface a ₁ of the FET A _1-3, operation electrodes made of a source electrode S, a drain electrode D, a gate electrode G, and the like having a predetermined plan view shape are formed to protrude, and the entire surface is uneven. And the back side remains the sapphire substrate 1.
[0019]
Next, the production of the heat dissipation board A ₂ will be described.
First, a flat plate made of a material having high thermal conductivity and excellent heat dissipation is prepared. Specifically, a metal flat plate such as Cu, Al, Fe, or stainless steel, or a plate such as AlN, zirconia, diamond-like carbon, or diamond is preferable.
Etching is performed after applying a photoresist on the surface of the flat plate 7 and performing patterning. As shown in FIG. 5, the relationship between the uneven shape of the surface a ₁ of the intermediate material A _1-3 and the negative / positive relationship. An intermediate material A ₂ -1 having an uneven surface is prepared.
[0020]
Incidentally, irregularities are formed in this case, in relation to be bonded to the irregular surface a ₁ of the semiconductor device A ₁ shown in FIG. 4 after forming here in the insulating film in the next step, the insulating film Is formed so that the uneven surface a ₁ of the semiconductor device A ₁ can be received there. For example, the recess 8a for receiving the gate electrode is formed slightly larger than the shape of the gate electrode in plan view, and the depth is also slightly deeper.
[0021]
Then, the intermediate material A ₂ -1 material of the insulating film on the surface for example by sputtering of allowed deposition after forming the insulating film 9 having a desired thickness, carried out for example liftoff, dry etching, the portions which do not require By removing the insulating film portion, the intermediate material A ₂ -2 having the uneven surface a ₂ shown in FIG. 6 is manufactured.
This intermediate material A ₂ -2 is an example in which no insulating film is formed in the recess 8b that receives the drain electrode, and the drain electrode is in direct contact with the heat dissipation substrate. As long as insulation between the working electrodes can be obtained, it is not necessary to form an insulating film in each of the recess 8a that receives the gate electrode and the recess 8c that receives the source electrode.
[0022]
As a material of the insulating film 9, it is an essential requirement that it be electrically insulating, but it is preferable that the material has a high thermal conductivity. It is possible to increase the heat dissipation effect for the heat generated by the semiconductor device A _1. Examples of such materials include metal oxides such as AlN, diamond and TaO _x , metal nitrides such as TiN, and the like.
[0023]
Then, as shown in FIG. 7, is disposed opposite the surface a ₂ of the intermediate material A ₁ -3 surface a ₁ and the intermediate material A ₂ -2 shown in FIG. Then, for example, both surfaces a ₁ and a ₂ are joined using solder, and the intermediate material A ₁ -3 and the intermediate material A ₂ -2 are combined to form an intermediate material A ₀ as shown in FIG.
Finally, it carried out, for example, laser irradiation with respect to the sapphire substrate 1 of the intermediate material A _0. As a result, the sapphire substrate 1 is peeled off and the semiconductor device A of the present invention shown in FIG. 1 is obtained.
[0024]
In the above description, a metal substrate is used as the heat dissipation substrate. Instead of a metal substrate, an insulating substrate that is electrically insulating and has high thermal conductivity, such as AlN or diamond, is used. You can also.
If such an insulating substrate is used, the surface can be processed and the surface can be directly bonded to the surface a _{1 of} the intermediate material A _1-3 shown in FIG. That is, it is not necessary to form the insulating film 9 on the surface as in the case of the intermediate material A ₂ -2 shown in FIG.
[0025]
Further, as a method for removing the sapphire substrate 1 of the intermediate material A ₀ , a mechanical polishing method, a polishing method combined with chemical etching (CMP), or the like can be applied in addition to the laser irradiation described above.
[0026]
【The invention's effect】
As is apparent from the above description, the semiconductor device of the present invention has a structure in which a heat dissipation substrate is bonded to the working electrode side, which is the surface on which a plurality of working electrodes of a semiconductor device are formed. Excellent heat dissipation against heat generated during driving. In other words, it has a structure capable of driving a large current.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an example A of a semiconductor device of the present invention.
FIG. 2 is a cross-sectional view showing an intermediate material A ₁ -1 when the device A is manufactured.
FIG. 3 is a cross-sectional view showing an intermediate material A ₁ -2 when the apparatus A is manufactured.
4 is a cross-sectional view showing an intermediate material A ₁ -3 at the time of manufacturing the device A. FIG.
FIG. 5 is a cross-sectional view showing an intermediate material A ₂ -1 when the apparatus A is manufactured.
6 is a cross-sectional view showing an intermediate material A ₂ -2 at the time of manufacturing the apparatus A. FIG.
7 is a sectional view showing a state where the surface a ₂ of the intermediate material A ₁ -3 surface a ₁ and the intermediate material A ₂ -2 placed opposite.
8 is a sectional view showing an intermediate material A _0.
[Explanation of symbols]
1 Crystal growth substrate (sapphire substrate)
2 Buffer layer 3 Non-doped GaN layer 4 Active layer 4a Active layer surface 5 Contact layer 6 SiO ₂ film 7 Metal flat plates 8a and 8b Recess 9 Insulating film

Claims (6)

The surface on which a plurality of working electrodes are formed on the surface of a semiconductor device formed on the substrate for crystal growth, and a recess having at least a similar shape to the surface view of the working electrodes on the surface and receiving the working electrodes A semiconductor device, wherein the surface of the heat dissipation substrate on which is formed is joined via an insulating film. 2. The semiconductor device according to claim 1, wherein the insulating film is made of a material having good thermal conductivity. 3. The semiconductor device according to claim 2, wherein the material is AlN or diamond. 2. The semiconductor device according to claim 1, wherein the heat dissipation substrate is made of Cu or Al. 2. The semiconductor device according to claim 1, wherein the semiconductor device is made of a GaN-based semiconductor material. The semiconductor device according to claim 1, wherein a said crystal growth substrate of the semiconductor device is removed.

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