JPH08102488A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE: To manufacture a semiconductor device of dielectric isolation structure, with a very simple process, and obtain excellent element characteristics. CONSTITUTION: In the manufacturing method of a semiconductor device of dielectric isolation structure, a mirror-finished Si substrate 11 on which surface an N<+> type layer 12 is formed and a mirror-finished Si substrate 13 on which surface an oxide film 14 is formed are bonded to each other by mutually sticking the polised surfaces whose roughness is 50nm or less, in a clean atmosphere in which foreign matters are not contained practically. Then the bonded compound body is heated at a temperature of 200 deg.C or higher, thereby improving the bonding strength. A plurality of desired elements are formed on the Si substrate 11 side of the bonded substrates which have been obtained. The elements are dielectrically isolated in the horizontal direction, by element isolation trenches 16 and passivation glass 17 buried in the trenches 16.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device having a dielectric isolation.

[0002]

2. Description of the Related Art For various light senses and displays,
There are many uses for one-dimensional and two-dimensional matrices of semiconductor devices. In such a matrix of elements, it is essential that the elements are completely electrically separated from each other. In particular, dielectric isolation is essential for a high breakdown voltage element, an optical sensor, and the like.

Conventionally, as a method of forming a device matrix in which dielectrics are separated, for example, a semiconductor thin film formed on an insulating substrate by an epitaxial method or various vapor deposition methods is used. However, according to these methods, (1) a semiconductor thin film cannot be formed sufficiently thick, so that a device with a high breakdown voltage and a large current cannot be produced.

(2) Since a high-quality semiconductor film cannot be obtained, there is a limit to element characteristics. (3) It is difficult to control the impurity concentration and distribution, and the element structure is limited. There was a problem such as.

On the other hand, in an integrated circuit, a semiconductor film is formed on a single crystal substrate by an epitaxial method, elements are formed thereon, and then the substrate is wrapped and removed, and then an insulating film such as an oxide film is formed on the back surface. There is known a method for element isolation. However, this method has the drawback of requiring very complicated steps.

Further, a technique of forming a device by subjecting a polycrystalline semiconductor film deposited on an insulating substrate to heat treatment with a laser, an electron beam, or the like to form a single crystal has recently been receiving attention. However, this method still has many problems to be solved in terms of control of crystal perfection, film thickness and shape.

[0007]

As described above, conventionally, there are various methods for forming a device matrix separated from a dielectric material. However, excellent device characteristics cannot be obtained by simple steps. Met.

The present invention has been made in view of the above points, and provides a method of manufacturing a semiconductor device having a dielectric isolation structure, which is capable of obtaining excellent device characteristics in a very simple process. With the goal.

[0009]

In the present invention, in order to obtain a dielectric isolation substrate, a technique is used in which a mirror-polished semiconductor substrate and an insulating substrate are integrated by directly bonding their polished surfaces to each other. That is, when substrates mirror-polished to a surface roughness of 50 nm or less are brought into close contact with each other in a clean atmosphere substantially free from foreign matter, and heat-treated at a temperature of 200 ° C. or more, a strong bonded substrate is obtained. The insulating substrate may be either a semiconductor substrate having an insulating film formed on its surface, or a substrate entirely made of a dielectric material.

A desired element is formed on the substrate thus separated in the vertical direction, and a groove is formed on the semiconductor substrate side for separating the element in the horizontal direction, and the groove is filled with an amorphous material. I do. In order to form a device group with high withstand voltage and large current,
It is absolutely necessary to increase the thickness of each element. For example, a thickness of 100 μm or more is required to realize a breakdown voltage of 1000 V or more. When such an element is separated by a groove in the lateral direction, it is difficult to wire across the groove, and it is necessary to fill the groove with a dielectric.

In the present invention, in order to directly adhere a substrate,
The smoothness of the substrate is important, and it is desirable to finish the substrate with a mirror surface having a surface roughness of 50 nm or less. With such a mirror surface, the two substrates will be joined together by close contact. In this case, since the joining is performed by itself, there is no need to apply an external pressure for heating. Therefore, a good substrate in which distortion due to pressure and the like hardly remains can be obtained. If the surface of the substrate to be bonded is contaminated, the surface is degreased with a solvent such as trichlene, rubbed with a neutral detergent, H ₂ O ₂
/ H ₂ SO ₄ mixed solution is used for cleaning. After that, it is washed with water and dehydrated using a spinner or the like.

The semiconductor substrate and the insulating substrate that have undergone these treatments are brought into close contact with each other in a clean atmosphere of class 1 or lower, and heated to 200 ° C. or higher to obtain a strong bonded substrate. A desired element is formed on the semiconductor substrate side of the obtained bonded substrate by a usual diffusion method or the like. Then, an element isolation groove is formed at a depth reaching the insulating substrate. This element isolation groove is formed by using a diamond-saw method, an etching method, or the like. The element isolation groove is filled with an amorphous material such as glass or an amorphous semiconductor used for passivation of various semiconductor elements. For example, passivation glass powder is coated by an electrodeposition method, a screen printing method, a sedimentation method, or the like, and the temperature is increased until the glass softens and flows, thereby densifying the glass.

Then, the coated amorphous material film is wrapped to leave the amorphous material only in the element isolation trench. As a result, the semiconductor element surface and the amorphous material surface have the same height, and thereafter, a desired element wiring can be easily formed.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. (Embodiment 1) FIGS. 1 and 2 are cross-sectional views showing steps of manufacturing a semiconductor device according to a first embodiment of the present invention.
First, as shown in FIG. 1 (a), two mirror-polished (11) layers having a thickness of 400 μm and an impurity concentration of about 10 ¹⁴ cm ⁻³ were used.
1) An n ^- type Si substrate is prepared. And one of the substrates 1
Phosphorus is diffused on the polished surface of No. 1 to form an n ⁺ -type layer 12 having a surface concentration of about 10 ¹³ cm ⁻³ , and the oxide film 14 is formed on the polished surface of the other substrate 13 by wet oxidation at 1200 ° C. for 6 hours.
Was formed. Both substrates were scrubbed with a neutral detergent to remove dust, immersed in a solution of H ₂ O ₂ : H ₂ SO ₄ = 1: 4, boiled for 30 minutes, and washed with water. Depending on the surface condition,
Pre-processing by HF and pre-processing by rare HF are performed.

Thereafter, both substrates are dehydrated with a spinner,
The polished surfaces are put together in a clean atmosphere of class 1 as shown in FIG.
As shown in FIG.
Heat treatment was performed at 200 ° C. for 2 hours to increase the adhesive strength. The spinner is used to remove excess water from the mirror-polished surface, and avoid drying at 100 ° C. or higher where most of the absorbed water evaporates. N ⁺ -type layer 1 of adhesive substrate thus obtained
2 is formed by lapping the substrate 11 so that the thickness from the bonding surface is about 100 μm, and then boron is diffused to form ap ⁺ type layer 15 having a thickness of about 20 μm as shown in FIG. Was formed.

Next, the entire surface is covered with an oxide
Depth 70 μm, width 1 using m-width diamond saw
Element isolation grooves 16 of 00 μm were formed at a pitch of 3 mm, and the crushed layer was removed. This state is shown in FIG. After that, as shown in FIG. 2 (b), lead-based passivation glass 17 (IP-760, trade name of Inotic Co.) was filled in the groove 16 by an electroconduction method and baked. Thereafter, although not shown, a contact hole was opened and Al wiring was provided to form a diode array.

The obtained diode array showed a withstand voltage of 1200 V for each element, and the insulation between the elements was sufficient. As described above, according to the present embodiment, it is possible to obtain a semiconductor element group that is dielectrically separated by a simple method. In particular, since the vertical separation of the substrate uses a direct bonding method between the semiconductor substrate and the insulating substrate, the thickness of the element can be freely selected, and a high voltage, large current diode or transistor matrix is formed. It is effective in the case where it is performed, and is useful when applied to various optical sensors, power integrated circuits, and the like. Also,
By filling the element isolation groove in the lateral direction with an amorphous material, the element wiring can be easily formed. (Embodiment 2) Next, a second embodiment of the present invention will be described with reference to FIGS.

As shown in FIG. 3A, an impurity concentration of 10
A mirror-polished (100) n ⁻ -type Si substrate 21 having a ^{size of} about ¹⁵ cm ⁻³ and a non-alkali glass substrate 24 (NA-40, trade name of Hoya Glass Co., Ltd.) also having a mirror-polished surface were prepared. n
^- The polished surface of the type Si substrate 21, hydrofluoric acid - width 200μm by chemical etching with nitric acid mixture, depth 100 [mu] m, a groove 22 of pitch 1 mm, further performing phosphorus diffusion 20
An n ⁺ -type layer 23 having a depth of μm was formed. Both substrates are degreased and cleaned on the polished surface as in the previous embodiment,
Spinner dried.

The Si substrate 21 on which the irregularities are formed as described above
As shown in FIG. 3B, the polished surfaces were brought into contact with each other in a clean atmosphere of class 1 and heated to 400 ° C. in air to integrate the glass substrate 24 with the glass substrate 24. After this, FIG.
As shown in FIG.
Exposed.

Then, the same glass 25 as in the previous embodiment is used.
Was filled in the groove 22 by a doctor blade method as shown in FIG. Thereafter, the Si substrate 21 side was further shaved to a thickness of about 60 μm, and a matrix of Si dots surrounded by the glass 25 was obtained. And FIG. 4 (b)
As shown in FIG.
^{The +} type layer 26 was formed and heat-treated at 600 ° C.

Thereafter, although not shown, the entire surface was covered with a CVD oxide film, contact holes were opened, and Al wiring was formed to form a matrix in which 30 × 30 photodiodes were connected in series.

The thus-formed photodiode matrix has excellent element isolation and excellent characteristics. The present invention is not limited to the above-described embodiments, and can be implemented with various modifications without departing from the scope of the invention.

[0023]

As described above, according to the present invention, the semiconductor substrate and the insulating substrate are directly bonded to each other,
By heating at the above temperature to improve the adhesive strength, a plurality of desired elements are formed on the semiconductor substrate side of the thus obtained adhesive substrate, and these elements are separated from each other in a dielectric material in the lateral direction, thereby making the process extremely simple. In addition, it is possible to manufacture a semiconductor device having a dielectric isolation structure capable of obtaining excellent element characteristics.

[Brief description of drawings]

FIG. 1 is a sectional view showing a first half of a manufacturing process of a semiconductor device according to a first embodiment.

FIG. 2 is a sectional view showing the latter half of the manufacturing process of the semiconductor device according to the first embodiment;

FIG. 3 is a cross-sectional view showing the first half of the manufacturing process of the semiconductor device according to the second embodiment.

FIG. 4 is a cross-sectional view showing the latter half of the manufacturing process of the semiconductor device according to the second embodiment.

[Explanation of symbols]

11, 13 ... n ^- -type Si substrate 12 ... n ⁺ -type layers 14 and 18 ... oxide layer 15 ... p ⁺ -type layer 16 ... isolation trench 17 ... passivation glass

Front Page Continuation (72) Inventor Junichi Oura 1 Komukai Toshiba-cho, Kawasaki-shi, Kanagawa Kanagawa Prefecture Corporate Research Institute

Claims (5)

[Claims] A step of bonding a mirror-polished semiconductor substrate and a mirror-polished insulative substrate to each other by bringing the polished surfaces having a surface roughness of 50 nm or less into close contact in a clean atmosphere substantially free of foreign matter; Heating the bonded composite at a temperature of 200 ° C. or higher to improve the bonding strength; forming a plurality of desired elements on the semiconductor substrate side of the obtained adhesive substrate; A method of manufacturing a semiconductor device. 2. The method of manufacturing a semiconductor device according to claim 1, wherein said insulating substrate has an insulating film formed on a surface of a semiconductor substrate. 3. The method of manufacturing a semiconductor device according to claim 1, wherein the dielectric isolation is performed by forming an element isolation groove in a semiconductor substrate and forming an amorphous material on at least a sidewall of the element isolation groove. 4. The method according to claim 3, wherein said amorphous material is filled in said element isolation trench. 5. The method according to claim 1, wherein the step of separating the dielectric is performed after the formation of the element.