JPS6358817A - Composite semiconductor crystal structure - Google Patents

Abstract

PURPOSE:To obtain the structure with which a composite semiconductor device is integrated easily by a method wherein the element regions, which are left by performing selective etching on a semiconductor substrate, are completely element- isolated with each other using a junction insulating film and the insulating film formed on the etched part. CONSTITUTION:The surface on the side of the first semiconductor substrate 16 of a composite substrate 19 is etched until a junction oxide film is exposed leaving an element region 16a. Besides, another etching operation is performed as far as to the inside part of the second semiconductor substrate 17, and after a thermally oxided film has been formed on the etched surface, the thermally oxided film is selectively etched, and the thermally oxided film 21, whereon the desired second semiconductor substrate surface and the like are exposed, is formed. Subsequently, when N<-> type silicon has been vapor-grown on the etched surface, an epitaxial layer 22 is formed on the surface of the silicon single crystal and, at the same time, a polycrystalline silicon layer 23 is formed on the thermally oxided film 21. Accordingly, as each element can be isolated completely by the junction insulating film and the insulating material of the insulating film formed on the etched part, the degree of restrictions placed on the inverse vias of the constitution of circuits is small.

Description

DETAILED DESCRIPTION OF THE INVENTION 1. Object of the Invention] (Industrial Application Field) The present invention relates to a composite semiconductor crystal structure, and in particular, the present invention relates to a composite semiconductor crystal structure, in which a plurality of functional elements that require element isolation can be integrated into one! It is used for the substrate of multi-layered composite semiconductor devices.

(Prior Art) In a composite semiconductor device in which a plurality of active elements or passive elements are integrated on one substrate, it is necessary to electrically isolate the elements from each other. The main device isolation methods used for this purpose include those using reverse biased PN junctions and those using insulators. Figure 3 shows 1 of the junction isolation method using PN junction.
Give an example.

A plurality of N-type semiconductor element regions 4 are connected to a P-type semiconductor substrate 1.
By applying a reverse bias to the PN junction between the element isolation region 3 and the N-type element region 4, it is electrically isolated from other N-type regions 2 via the depletion layer. Although this method is inexpensive, there are restrictions on the circuit configuration for providing a reverse bias potential, and the leakage current of the PN junction is a drawback in terms of characteristics. FIG. 4 shows a conventional example of the device isolation method using an insulator. A plurality of N-type semiconductor device regions 5 form island regions separated and held by a silicon oxide film 6 and a polycrystalline silicon layer 7. This method has advantages such as not requiring the reverse bias circuit required for the PN junction separation, and having fewer restrictions due to parasitic elements.

However, in this method, what corresponds to the substrate is composed of the polycrystalline silicon layer 7, which requires a step of depositing very thick polycrystalline silicon, which is economically disadvantageous. Furthermore, since one surface of the polycrystalline silicon layer 7 is insulated by the silicon oxide film 6, there is a disadvantage that the polycrystalline silicon layer 7 serving as a substrate cannot be used as a current circuit.

(Problems to be Solved by the Invention) An object of the present invention is to solve the above-mentioned problems and provide a composite semiconductor crystal body with a novel structure that allows easy integration of composite semiconductor devices.

[Structure of the Invention] (Means and Effects for Solving the Problems) The present invention provides a composite structure in which one main surface of a first semiconductor substrate and one main surface of a second semiconductor substrate are mirror-joined via an insulating film. a substrate, a first semiconductor substrate and a bonding insulating film of the composite substrate are selectively etched, and at least a portion of the etched portions reach the second semiconductor substrate; and an insulating film formed on some of the etched portions. an epitaxial layer provided on a second semiconductor substrate in the etched portion; and a polycrystalline silicon layer provided on an insulating film formed in the etched portion at the same time as the epitaxial layer. It is a semiconductor crystal.

In the composite semiconductor crystal of the present invention, each element region left after selectively etching the first semiconductor substrate is completely interconnected by the bonding insulating film left by etching and the insulating film formed in the etched portion. The elements are isolated from each other, and the elements are also isolated from the element regions in the epitaxial layer provided on the second semiconductor substrate.

In the second semiconductor substrate and the epitaxial layer connected thereto, it is possible to form power elements with different breakdown voltage characteristics by adjusting the arbitrary layer thickness and impurity concentration independently of the element region formed from the first semiconductor substrate. Yes, the polycrystalline silicon layer deposited on the insulating film at the same time as the epitaxial layer is X! It can be used for filling the membranous groove.

(Example) FIG. 1(e) shows a cross-sectional view of an example of the composite semiconductor crystal of the present invention, and FIG. 1(a) to e) show the main parts of the manufacturing process of this example crystal. This shows that.

First, the bonded surface (bottom surface of the figure) of the first semiconductor substrate 16 of N-type silicon and the bonded surface (top surface of the figure) of the second semiconductor substrate 17 of N1-type silicon shown in FIG. Thermal oxide films 18a and 18b are formed to a thickness of about 1 μm. Next, the thermal oxide film surface 18 formed on the first and second semiconductor substrates
A and 18b are polished to a mirror surface, and the mirror surfaces of the first semiconductor substrate 16 and the second semiconductor base plate 17 are brought into close contact with each other in a sufficiently clean atmosphere and heat treated to form a bonding oxide film as shown in FIG. 1(b). A composite substrate 19 is obtained which is strongly mirror bonded via the substrate 18. Next, after polishing the surface of this composite substrate 19 on the first semiconductor substrate 16 side to make the thickness of the first semiconductor substrate 16, for example, about 100 μm, this surface is selectively subjected to a known photolithography process. , as shown in FIG. 1C, the first semiconductor substrate 16 is covered with a junction oxide film 18, leaving the element region 16a.
Etch until exposed. Next, as shown in FIG. 1(d), the exposed junction oxide film 18 is removed, and the inside of the second semiconductor substrate 17 is etched. A thermal oxide film is applied to the etched surface, and then selectively etched. Then, a thermal oxide film 21 is formed in which a desired second semiconductor substrate surface and the like are exposed. Thereafter, when N- type silicon is grown in vapor phase on the etched surface, an epitaxial layer 22 is formed on the silicon single crystal surface, and at the same time, a polycrystalline silicon layer 23 is formed on the thermal oxide film 21.

After this, the first semiconductor substrate 16, the epitaxial layer 22,
When the polycrystalline silicon layer 23 is polished, the composite semiconductor crystal shown in FIG. 1(e) is obtained.

The embodiment shown in FIG.
The thickness of the epitaxial layer 22 is thicker than that shown in FIG. The thickness is the same as that from the first semiconductor substrate 16.

[Effects of the Invention] In the composite semiconductor crystal structure of the present invention, each element can be completely separated by the insulator of the junction insulating film and the insulating film formed in the etched portion, so that restrictions on circuit configuration related to reverse bias can be avoided. I rarely receive it.

In addition, since the layer thicknesses and impurity concentrations of the device region consisting of the first semiconductor substrate portion, the second semiconductor substrate, and the epitaxial layer can be adjusted arbitrarily, functional elements with different breakdown voltage characteristics can be formed by creating appropriate differences in these. It is structurally possible to form one composite semiconductor crystal. Furthermore, when a power element is formed as a functional element, it is convenient because the back surface of the composite semiconductor crystal on the second semiconductor substrate side can be effectively used as a current path.

[Brief explanation of drawings]

FIGS. 1<a) to 1(0) are cross-sectional views showing the manufacturing process of a composite semiconductor crystal according to an embodiment of the present invention (FIG. 1(e) is a cross-sectional view showing the manufacturing process of a composite semiconductor crystal according to an embodiment of the present invention). 2 is a sectional view showing another embodiment of the composite semiconductor crystal of the present invention, FIG. 3 is a sectional view of a conventional junction isolation device using a PN junction, and FIG. 4 is a sectional view showing the structure of a semiconductor crystal. 1 is a cross-sectional view of a conventional insulating layer separation method element using an insulator. 16... First semiconductor substrate, 17... Second semiconductor substrate, 18... Bonding insulating film, 19... Composite substrate,
21... Insulating film formed on the etched portion, 22° 22a
...Epitaxial layer, 23...Polycrystalline silicon layer. Figure 1 <C> Section 1 (d) Figure 1 (e) Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] 1 one main surface of the first semiconductor substrate and one main surface of the second semiconductor substrate
A composite substrate formed by mirror bonding two principal surfaces via an insulating film, and at least a portion of the composite substrate formed by selectively etching the first semiconductor substrate and the bonding insulating film to reach the second semiconductor substrate. an etched portion, an insulating film formed on some of the etched portions, an epitaxial layer provided on the second semiconductor substrate of the etched portion, and an insulating film formed on the etched portion at the same time as this epitaxial layer. A composite semiconductor crystal body comprising a polycrystalline silicon layer.