JPH0786298A - Semiconductor device - Google Patents

Abstract

PURPOSE:To improve the heat dissipating effect of a bipolar device formed on an SOI substrate and operate the bipolar device at a high speed by the reduction of the capacitance present between the bipolar device and the SOI substrate. CONSTITUTION:A first oxide film 2 is formed on a P-type silicon substrate 1, and an N-type silicon film 3 is formed on the first oxide film 2, and a second oxide film 4 is formed on the N-type silicon film 3, and further, an N-type epitaxial layer 5 is made to grow on the second oxide film 4, and moreover, a bipolar transistor is formed on the N-type epitaxial layer 5. Further, on the outside of the element separating region of this bipolar transistor, a groove stuck into the epitaxial layer 5 and the second oxide film 4 whose bottom part is provided in the N-type silicon film 3 is formed. Moreover, a non-doped polycrystal silicon film 7b is so buried in the groove that it is extended from the bottom part of the groove to the surface thereof and it is connected with a heat dissipating electrode 13. Thereby, since heat conducts to the heat dissipating electrode 13 via the N-type silicon film 3 and the polycrystal silicon film 7b, the heat dissipating effect of the bipolar transistor is improved.

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 silicon-on-insulator (SOI) structure.

[0002]

2. Description of the Related Art A conventional bipolar transistor formed on an SOI substrate will be described. FIG. 8 is an N-type epitaxial layer grown on the oxide film 20 formed on the silicon substrate 1 through the high-concentration N ⁺ -type buried layer 6 at a predetermined position or on the entire surface of the SOI layer formed by, for example, bonding. An oxide film is formed on the layer 5 as an element isolation region on the sidewall of the trench reaching the oxide film 20 (not shown),
It has a structure in which a non-doped polycrystalline silicon film 7a is buried. Further, 12a to 12c are electrodes, and 16 is a mask oxide film. The oxide film 20 and the non-doped polycrystalline silicon film 7a form an element isolation structure. This kind of element isolation structure, which is a conventional technology, is called "High-Speed So
ft-Error-Immune ECL Circuits with Fully Isolated T
ransistors "(IEEE Trans. on Electron Devices, vol.
39, No. 3, MARCH 1992). in this case,
An oxide film 20 having a thickness of 0.5 μm is formed on the entire surface of the silicon substrate 1 serving as a supporting substrate, and the silicon substrate 1 to be a semiconductor substrate is bonded to the silicon substrate 1, pulse application is performed, and heat treatment is performed to bond the silicon substrate 1 to each other. Next, by polishing, the semiconductor substrate portion is left with a thickness of about 2.0 μm. Then, the trench in the element isolation region is formed by performing silicon etching up to the oxide film and burying a polycrystalline silicon film. The main part of the transistor is the conventional manufacturing method E
It is produced using SPER.

[0003]

In this conventional bipolar transistor on the SOI substrate, the oxide film 20 on the substrate 1 is formed in order to reduce the capacitance _Ccs between the substrates for speeding up.
It was necessary to make the film thickness of 0.5 μm or more, for example. (FIG. 9) However, in such a structure, when the thickness of the oxide film 20 is increased, the heat generated by the current flowing through the collector of the transistor, that is, the N ⁺ type buried layer, causes the heat generated in the trench portion to be generated. At the same time as it is transmitted to the side wall, it escapes toward the bottom, but since it passes through the oxide film 20 having a thermal resistance 100 times higher than that of silicon, it is difficult to be transmitted to the silicon substrate 1, the heat dissipation state deteriorates, and the temperature rise of the semiconductor element is prevented. It had the drawback of increasing it.

[0004]

The present invention provides a first insulating layer formed on a first semiconductor layer, a second semiconductor layer formed on the first insulating layer, and a second semiconductor layer on the second semiconductor layer. A second insulating layer formed on the second insulating layer, and a third insulating layer formed on the second insulating layer.
In a structure having a semiconductor layer, a semiconductor element having an insulating region extending from this surface to the second insulating layer is formed in a part of the third semiconductor layer, and the third semiconductor layer is provided outside the semiconductor element. A structure having a groove formed by penetrating the second insulating layer and reaching the second semiconductor layer, the polycrystalline silicon film buried in contact with the bottom of the groove, and the polycrystalline silicon film. A semiconductor device formed on a semiconductor layer above an oxide film, and specifically, a first semiconductor layer and a semiconductor electrode formed on the first semiconductor layer. A first oxide film, a second semiconductor layer formed on the first oxide film, a second oxide film formed on the second semiconductor layer, and a second oxide film formed on the second semiconductor layer.
N grown through the N ⁺ type buried layer formed on the oxide film
As the third semiconductor layer, the type epitaxial layer is used as a third semiconductor layer, and in the third semiconductor layer, a semiconductor element portion surrounded by an insulating region and the surface of the N-type epitaxial layer provided outside the semiconductor element portion, It has a groove penetrating the second oxide film, a non-doped polycrystalline silicon film buried from the bottom of this groove, and a metal electrode connected to this polycrystalline silicon film on the surface of this groove. is there.

[0005]

Embodiments of the present invention will be described with reference to the drawings. [Embodiment 1] FIG. 1A is a sectional view of a semiconductor device according to Embodiment 1 of the present invention, and FIG. 1B is a plan view. A first oxide film 2 is formed on a P-type silicon substrate 1, an N-type semiconductor layer 3 is formed on the first oxide film 2, and a thin second oxide film 4 is formed on the first oxide film 2. Epitaxial layer 5 is grown via N ⁺ type buried layer 6, and has side wall nitride film 8 on the side wall oxide film as an insulating region and element isolation trench 15 in which non-doped polycrystalline silicon film 7a is buried. . Further, the semiconductor element has an N ⁺ type buried layer 6 as a collector of a bipolar transistor, an N ⁺ type region 9, a P ⁺ type base region 10 and an N ⁺ type emitter region 11 inside. A heat dissipation trench 14 having a non-doped polycrystalline silicon film 7b embedded therein is formed outside the insulating region of the device. The surface of the heat dissipation trench 14 is connected to the metal electrode 13. The first oxide film 2 is
It is formed with a thickness of about 1.0 μm to reduce the capacitance between the substrate and the N-type semiconductor layer 3 so that heat can be easily conducted.
A thickness of about 1.0 μm or more is required. Further, the thickness of the second oxide film 4 is formed to be 0.2 μm or less in order to facilitate heat conduction to the N-type semiconductor layer 3. Further, as shown in FIG. 1B, the heat dissipation trench 14 and the heat dissipation electrode 1
Other than forming the L-shape around the element, the element 3 may be formed so as to surround the periphery of the element portion, depending on the degree of freedom of layout.

Next, a schematic cross-sectional view showing the sequence of main steps for explaining a method of manufacturing a semiconductor device is shown in FIGS.
(C), FIG.3 (d)-(f), and FIG.1 (a).
The description will be made with reference to FIG. The bipolar transistor of the first embodiment is formed as follows. First, the entire surface of the P-type silicon substrate 1 is oxidized to form a first oxide film 2 having a thickness of about 1.0 μm. Next, after bonding the N-type silicon substrate by laminating, it is polished to about 2.
The thickness is reduced to 0 μm to form the N-type silicon layer 3.
[FIG. 2 (a)] Next, an acceleration voltage of 200 keV and a dose amount of about 0.5 × 10.
After implanting oxygen ions of ¹⁸ cm ^-2, a second oxide film 4 is formed inside the N-type silicon layer 3 by heat treatment at 1280 ° C. or higher.
To a thickness of about 0.1 μm. [FIG. 2 (b)] Furthermore, N ⁺ as an embedded collector of the transistor
The mold burying layer 6 is formed at a predetermined position by photolithography, for example, by ion implantation of arsenic. After that, the N-type epitaxial layer 5 is grown. (The upper portion of the N-type silicon layer 3 is included in this layer.) [FIG. 2 (c)] Next, the element isolation trench 15 and the heat dissipation trench 14 are silicon-etched by patterning. At this time, the etching ratio between silicon and the oxide film is large, and the second oxide film 4 at the bottom of the trench can be left without being etched. [FIG. 3D] Further, after the nitride film is grown, ion etching is performed until the second oxide film 4 at the bottom of the trench is exposed, and the sidewall nitride film 8 is left. Then, the second oxide film 4 at the bottom of the trench is removed by wet etching. [Fig. 3 (e)]

Next, a non-doped polycrystalline silicon film is grown to fill the element isolation trench 15 and the heat dissipation trench 14. It should be noted that the non-doping makes it possible to increase the dielectric constant and reduce the capacitance of the side wall of the trench. Then, the non-doped polycrystalline silicon film on the surface of the N-type epitaxial layer 5 is removed by etching back. [Fig. 3 (f)]
After that, N ⁺ type regions 9P ⁺ type base regions 10 and N ⁺ type emitter regions 11 to be collector extractions are formed by diffusion or ion implantation, respectively, and then a mask oxide film 16 is grown on the entire surface to collect collector, base, After the mask oxide film 16 on the emitter and the heat dissipation trench 14 is patterned and removed, the electrodes 12a to 12c are formed. [FIG. 1A] Next, referring to FIG. 4 which is a schematic cross-sectional view showing the heat dissipation effect, in the first embodiment, a current flows through the bipolar transistor, and the N ⁺ type buried layer as the collector is formed. When the heat is generated at 6, it is transmitted to the N-type semiconductor layer 3 through the thin second oxide film. The N-type semiconductor layer 3 is formed of the non-doped polycrystalline silicon film 7b buried in the heat dissipation trench 14.
Since it is connected to the device, heat is transmitted, and further, it is possible to radiate heat to the outside of the device via the heat dissipation electrode 13 provided on the surface. Further, even if the thickness of the first oxide film is 1.0 μm or more and the capacitance between the substrates is reduced, this heat radiation effect can be maintained.

[Second Embodiment] Next, a second embodiment of the present invention will be described with reference to the drawings. FIG. 7 is a sectional view of a semiconductor device according to a second embodiment of the present invention. A first oxide film 2, an N-type semiconductor layer 3 and a second oxide film 4 are formed on a P-type silicon substrate 1, and an N-type epitaxial layer 5 is grown on the first oxide film 2, an N-type buried layer 6 and an N ⁺ type buried layer 6. , An SOI layer, and an isolation region having an element isolation trench 15 having a sidewall nitride film 8 on a sidewall oxide film as an insulating region, and an N ⁺ type buried layer 6, an N ⁺ type region 9 and It is similar to the first embodiment in that it has the D ⁺ type base region 10 and the N ⁺ type emitter region 11, and the heat dissipation trench 14 is formed outside the insulating region of the element. The difference from the first embodiment is that the element isolation trench 15 and the heat dissipation trench 14 are formed separately,
This is that the tungsten film, which is a conductor film, is buried in the heat dissipation trench 14. Further, since the second oxide film 4 on the bottom of the element isolation trench 15 is not removed by etching,
The embedded polycrystalline silicon film 17 may be doped.

Next, FIGS. 5A to 5C are schematic cross-sectional views in the order of main steps for explaining the method for manufacturing a semiconductor device.
6 (d) to 6 (f) and FIG. 5 together. The bipolar transistor of the second embodiment is formed as follows. First, the entire surface of the P-type silicon substrate 1 is oxidized to form the first oxide film 2, the N-type silicon substrates are bonded together and polished to form the N-type silicon layer 3. [FIG. 5 (a)] Next, an acceleration voltage of 200 keV and a dose amount of about 0.5 × 10
Oxygen ion implantation of ¹⁸ cm ^-2 is performed, and a second oxide film 4 having a thickness of about 0.1 μm is formed inside the N-type silicon layer 3 by heat treatment at 1280 ° C. or higher. [FIG. 5 (b)] Further, an N ⁺ type buried layer 6 is formed at a predetermined position of the transistor by arsenic ion implantation by a photolithography technique, and then an N type epitaxial layer 5 is grown. FIG. 5 (c)]

Next, the element isolation trench 15 is etched by silicon by patterning. At this time, the etching ratio of silicon to the oxide film is large, and the second oxide film 4 at the bottom of the trench can be left without being etched.
[FIG. 6D] Further, trench sidewall oxidation is performed to grow a sidewall nitride film 8 and a polycrystalline silicon film 17. After removing the polycrystalline silicon film and the nitride film on the surface by etch back, the heat dissipation trench 14 is patterned using the nitride film 18 as a mask. Then, silicon etching is performed until the second oxide film 4 is reached. [FIG. 6 (e)] Further, after the nitride film is grown, ion etching is performed until the second oxide film 4 at the bottom of the heat dissipation trench 14 is exposed, and the sidewall nitride film 8 is left. Then, the second oxide film 4 at the bottom of the trench is removed by wet etching.

Next, a tungsten film is grown by blanket CVD, and the heat dissipation trench 1 is etched back.
The tungsten film 19 is embedded only in the inside of the 4 [FIG.
(F)] Thereafter, an N ⁺ type region 9, a P ⁺ type base region 10 and an N ⁺ type emitter region 11 for leading the collector are formed, and a mask oxide film 16 is grown on the entire surface. Then, after removing the mask oxide film 16 on the collector, the base, the emitter and the heat dissipation trench 14 by patterning, each electrode 12 is removed.
a to c, 13 are formed. [FIG. 7] This structure has one more patterning times than the first embodiment shown in FIGS. 1, 2 and 3, but it is necessary to remove the second oxide film 4 at the bottom of the element isolation trench 15. There is no
Further, it is advantageous that a material having a better heat conduction such as the tungsten film 19 can be selected for the heat dissipation trench 14. Further, the element isolation trench 15 is electrically N
Since it is not connected to the type silicon layer 3, it is possible to further reduce the capacitance to the substrate including the element peripheral portion.

[0012]

As described above, according to the present invention,
A first oxide film formed on the first semiconductor layer, a second semiconductor layer formed on the first oxide film, a second oxide film formed on the second semiconductor layer, and the second oxide film. The epitaxial layer formed on the film is provided outside the element isolation region of the semiconductor element having the semiconductor substrate as the semiconductor layer. The formed groove and the side surface of the groove are separated from the epitaxial layer, and a non-doped polycrystalline silicon film is buried from the bottom to the surface of the groove, and the non-doped polycrystalline silicon film is connected to the heat dissipation electrode on the surface. Further, the first oxide film is formed to a thickness of 1.0 μm, and the second oxide film is formed to a thickness of 0.2 μm or less. As a result, the heat dissipation effect of the semiconductor element can be enhanced without increasing the capacitance between the substrate and the substrate. Since the oxide film thickness becomes 1/5, the temperature rise rate can be reduced to about 20%.

[Brief description of drawings]

FIG. 1 is a schematic sectional view for explaining a first embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view in the order of main steps (a) to (c) for explaining the manufacturing method according to the first embodiment of the present invention.

FIG. 3 is a schematic cross-sectional view in the order of main steps (d) to (f) for explaining the manufacturing method according to the first embodiment of the present invention.

FIG. 4 is a schematic cross-sectional view for explaining the action and effect of the first embodiment of the present invention.

FIG. 5 is a schematic cross-sectional view in the order of main steps (a) to (c) for explaining the manufacturing method according to the second embodiment of the present invention.

FIG. 6 is a schematic cross-sectional view in the order of main steps (d) to (f) for explaining the manufacturing method according to the second embodiment of the present invention.

FIG. 7 is a schematic cross-sectional view for explaining the second embodiment of the present invention.

FIG. 8 is a schematic cross-sectional view for explaining a conventional bipolar transistor on an SOI substrate.

FIG. 9 is a schematic cross-sectional view for explaining problems of a conventional bipolar transistor on an SOI substrate.

[Explanation of symbols]

1 P-type silicon substrate 2 First oxide film 3 N-type silicon layer 4 Second oxide film 5 N-type epitaxial layer 6 N ⁺ type buried layer 7a, b Non-doped polycrystalline silicon film 8 Sidewall nitride film 9 N ⁺ type region 10 P ⁺ type base region 11 N ⁺ type emitter region 12a to c electrode 13 heat dissipation electrode 14 heat dissipation trench 15 element isolation trench 16 mask oxide film 17 polycrystalline silicon film 18 nitride film 19 tungsten film 20 oxide film

Claims (5)

[Claims] 1. A first insulating layer formed on a first semiconductor layer, a second semiconductor layer formed on the first insulating layer, and a second insulating layer formed on the second semiconductor layer. And the second
In a structure having a third semiconductor layer formed on an insulating layer, a semiconductor element having an insulating region reaching from the surface to the second insulating layer is formed in a part of the third semiconductor layer, and the semiconductor element A structure having a groove formed by penetrating the second insulating layer from the surface of the external third semiconductor layer to reach the second semiconductor layer at the bottom, and polycrystal embedded in contact with the bottom of the groove. A semiconductor device comprising a silicon film and a metal electrode connected to the polycrystalline silicon film. 2. A conductive film buried in contact with the bottom of the groove and a metal electrode connected to the conductive film instead of the buried polycrystalline silicon film. The semiconductor device described. 3. A semiconductor device is provided so as to surround the periphery of the semiconductor device.
2. The semiconductor device according to claim 1, further comprising a groove that penetrates the second insulating layer from the surface of the third semiconductor layer and has a bottom portion that reaches the second semiconductor layer. 4. The semiconductor device according to claim 1, wherein the first insulating layer is thicker than the second insulating layer. 5. The semiconductor device according to claim 1, wherein the polycrystalline silicon film buried in the groove is not doped with impurities.