JPH06252256A - Manufacture of dielectric isolation type semiconductor - Google Patents

Abstract

PURPOSE:To prevent the decrease of impurity concentration of an impurity high concentration region formed in a part of the bottom of an island type element region after sintering, in a dielectric isolation type semiconductor device wherein single crystal silicon substrates are mutually stuck. CONSTITUTION:In the island type element region of a lateral type bipolar element 18 which has a P-type impurity high concentration region 3 in the bottom part, an oxide film 19 on the bottom surface is made thin. Hence, at the time of sintering, P-type impurities contained in glass 7 can diffuse into the P-type high concentration impurity region 3. Thereby a high concentration impurity region can be selectively formed, in a dielectric isolation type semiconductor device wherein single crystal silicon substrates are mutually stuck in a sintering process.

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 dielectric isolation type semiconductor device manufactured by laminating single crystal silicon substrates using soot-shaped glass.

[0002]

2. Description of the Related Art A dielectric material manufactured by laminating a single crystal silicon substrate through a soot-shaped glass to form a p-type island element region separated by a dielectric material on a single crystal silicon substrate. FIG. 3 shows a conventional example of a separation type semiconductor device in which a high concentration p-type impurity region is formed on the bottom surface of a part of the p-type island element region, and a manufacturing method thereof will be described with reference to FIG. The cross-sectional view of FIG. 4 shows a method of manufacturing a semiconductor substrate of an optically coupled semiconductor relay in the order of steps. A photovoltaic diode and a lateral bipolar element that is a control element thereof are simultaneously formed on the same substrate. It shows the process.

First, FIG. 3 showing a state in which element formation is completed.
The configuration of each part will be described based on. In the figure, the island element region indicated by 17 constitutes a photovoltaic diode, and the island element region indicated by 18 constitutes a lateral bipolar element. Reference numeral 2 is an oxide film, 3 is a high concentration p-type impurity region of the lateral type bipolar element 18, 5 is an isolation oxide film for electrically isolating each island element region and preventing diffusion of impurities, and 6 is each P-type island element region for forming an element, 7 is p
A soot-shaped glass containing a boron-type impurity boron B is formed on the single crystal silicon substrate 8 by a sintering process.
Is to be fixed.

Further, the photovoltaic diode 17 has p ⁺
It consists in the area of type anode region 9, p-type anode region 10, n ⁺ type cathode region 11, a lateral bipolar element 18, n ⁺ -type emitter region 12, p-type base region 13, n ⁺ The collector region 14 of the p-type, the region of the p ⁺ -type base region 15, and the p ⁺ -type base region (p-type impurity high-concentration region 3). 16 is an electrode.

The photovoltaic diode 17 must generate a large number of carriers in order to efficiently extract the photocurrent, but the light receiving area of the substrate surface is limited,
The P-type island element region must be thickened to ensure a sufficient carrier generation region. The thickness of each p-type island element region will be formed uniformly according to the thickness of the p-type island element region of the photovoltaic diode 17.

On the other hand, the lateral bipolar element 18 is
In order to increase the current amplification factor h _FE and to reduce the base resistance, the p-type island high concentration region 3 is formed in the p-type island element region formed to be sufficiently thick in accordance with the photovoltaic diode 17. There is a need.

Next, the manufacturing process will be described with reference to FIGS. 4 (a) to 4 (g). First, as shown in FIG. 4A, the p-type single crystal silicon (100) substrate 1 is thermally oxidized,
The oxide film 2 in the portion forming the p-type impurity high concentration region 3 is selectively removed by photolithography. And
Using the remaining oxide film 2 as a mask, p-type impurity boron B is diffused or ion-implanted to form a p-type impurity high concentration region 3. At this time, oxidation is performed so that an oxide film thickness enough to serve as a mask can be obtained for the subsequent silicon anisotropic etching.

Next, as shown in FIG. 4B, the oxide film 2 in the portion forming the groove for separating the p-type island element region is selectively removed by photolithography, and the remaining oxide film 2 is removed.
Using the mask as a mask, the p-type single crystal silicon (100) substrate 1 is anisotropically etched to form a groove 4.

Next, after removing the remaining oxide film 2 as shown in FIG. 4 (c), the isolation oxide film 5 is removed as shown in FIG. 4 (d).
To form. The thickness of the isolation oxide film 5 not only allows the p-type island-shaped element regions 6 to be electrically isolated from each other, but also reduces the photocurrent of the photovoltaic diode 17 due to impurity diffusion from the glass 7 in the subsequent step. A sufficient film thickness is required so as not to occur.

Next, as shown in FIG. 4 (e), BCl ₃ , S
A boron-doped soot-like glass 7 is deposited on the isolation oxide film 5 using a gas such as iCl ₄ , O ₂ or the like, and a single crystal silicon substrate 8 is bonded thereto, followed by heat treatment and sintering.

Next, as shown in FIG. 4F, the semiconductor substrate is turned upside down, and the p-type single crystal silicon (100) substrate 1 is polished until the isolation oxide film 5 having a predetermined thickness is exposed. A dielectric isolation type substrate having island-shaped element regions 6 is prepared.

Finally, as shown in FIG. 3, each region of the lateral bipolar element 18 is provided in the p-type island element region having the p-type impurity high concentration region 3 and the p-type impurity high-concentration region 3 is not provided. After forming each region of the photovoltaic diode 17 in the island element region, the electrode 16 and the oxide film 2 are formed.

[0013]

However, since the above-mentioned sintering process requires treatment at a high temperature of 1200 ° C. or higher for a long time, impurities in the p-type impurity high-concentration region 3 diffuse and the concentration thereof increases. Will decrease. Therefore, there is a problem that the resistance of the p-type impurity high concentration region 3 increases. In the above-mentioned conventional example, the lateral bipolar element 1
8 will increase the base resistance.

The present invention has been made in view of the above problems. An object of the present invention is to provide a dielectric isolation type semiconductor device in which single crystal silicon substrates are attached to each other, and a part of the island-shaped element is formed after the sintering step. It is an object of the present invention to provide a method of manufacturing a dielectric isolation type semiconductor device capable of preventing the impurity concentration of a high impurity concentration region formed at the bottom of a region from decreasing.

[0015]

In order to solve the above problems, a method of manufacturing a dielectric isolation type semiconductor device according to the present invention is a step of forming a groove on the surface of a first conductivity type (p type) single crystal silicon substrate. A step of forming an isolation insulating film on the one main surface in which the groove is formed, a step of depositing glass containing impurities of the first conductivity type on the one main surface, and a step of depositing glass on the single crystal silicon substrate. Bonding another single crystal silicon substrate through glass and heat-treating, and polishing until the separation insulating film is exposed from the other main surface of the single crystal silicon substrate in which the groove is formed, to form a plurality of island shapes. In the method of manufacturing a dielectric isolation type semiconductor device having a step of forming an element region, the step of forming the isolation insulating film includes the step of forming a part of the island-shaped element region in which a high-concentration impurity region of the first conductivity type is formed at the bottom. At the time of heat treatment, As impurities in Las can diffuse into the high impurity concentration region, and is characterized in that said island-like element region bottom surface of the isolation insulating film only relatively thin to process.

[0016]

When the p-type impurities contained in the deposited glass are sintered, the p-type impurities pass through the thin insulating film for isolation at the bottom surface of the p-type island element region formed at the bottom of the p-type impurity high concentration region during sintering. Diffuse in high concentration area.

[0017]

EXAMPLE A method for manufacturing a dielectric isolation type semiconductor device of the present invention will be described with reference to FIG. 2, and a sectional view after element formation is shown in FIG. The configuration different from the conventional example is only the thin oxide film on the bottom surface of the p-type island element region having the p-type impurity high-concentration region formed at the bottom and the silicon nitride film used to form the thin oxide film. The same reference numerals are given to the same configurations as, and detailed description will be omitted. In the following examples, the case where the p-type impurity high concentration region is formed in the p-type island-shaped element region is shown, but the same applies to the case where the n-type impurity high concentration region is formed in the n-type island-shaped element region. However, in this case,
Glass doped with n-type impurities such as phosphorus P must be used. The type of p-type impurities is not limited to boron B either.

First, as shown in FIG. 2A, the p-type single crystal silicon (100) substrate 1 is thermally oxidized to select the oxide film 2 in the portion where the p-type impurity high concentration region 3 is to be formed by photolithography. To remove it. Then, the p-type impurity boron B is diffused or ion-implanted using the remaining oxide film 2 as a mask to form the p-type impurity high concentration region 3. At this time, oxidation is performed so as to obtain an oxide film thickness that can be electrically separated from the surrounding p-type island element region, and the oxide film 19 is formed.
To form. When forming the photovoltaic diode 17 and the low breakdown voltage element such as the lateral type bipolar element 18 which serves as a control element thereof, it is sufficient that the thickness of the oxide film 19 is about 1 μm. The thickness of the oxide film 19 is 1 μm.
As long as it is approximately, the p-type impurity high-concentration region 3 can be doped with boron from the glass 7 in the substrate-bonding sintering step.

Next, as shown in FIG. 2 (b), after depositing a silicon nitride film 20, as shown in FIG. 2 (c), silicon on the oxide film 19 on the p-type impurity high-concentration region 3 is deposited. The nitride film is selectively left by photolithography.

Next, as shown in FIG. 2D, the oxide film 2 in the portion where the groove is to be formed is selectively removed by photolithography, and the remaining oxide film 2 and silicon nitride film 20 are removed.
P-type single crystal silicon (100) substrate 1 using the as a mask
Is anisotropically etched to form the groove 4. The remaining oxide film 2 is removed as shown in FIG.

Thereafter, as shown in FIG. 2F, an isolation oxide film 5 having a sufficient thickness is formed so that the p-type impurity boron is not diffused from the glass into the p-type island-shaped element region 6. At this time, since the oxide film 19 is covered with the silicon nitride film 20, the film thickness of the oxide film 19 hardly increases.

Next, as shown in FIG. 2 (g), a boron-doped soot-like glass 7 is deposited on the isolation oxide film 5, and a single crystal silicon substrate 8 is bonded thereto, followed by heat treatment and sintering. . At this time, since boron is doped from the glass 7 into the p-type impurity high-concentration region 3 through the oxide film 19, even if the p-type impurity originally doped in the p-type impurity high-concentration region 3 is diffused. , P of the p-type impurity high concentration region 3
The type impurity concentration does not decrease.

FIG. 5 shows a p-type impurity concentration distribution in the thickness direction in the p-type island element region in which the p-type impurity high concentration region 3 is formed. In FIG. 5, the horizontal axis represents the distance from the bottom surface of the island element region, and the vertical axis represents the p-type impurity concentration. Figure 5
5A shows the case of the conventional manufacturing method, and FIG. 5B shows the case of the manufacturing method of the present invention. It can be seen that the p-type impurity concentration on the bottom surface of the p-type island element region is higher in FIG. 5 (b) than in FIG. 5 (a).

As the next step, as shown in FIG.
The semiconductor substrate is turned over and the p-type single crystal silicon (100) substrate 1 is polished until the isolation oxide film 5 having a predetermined thickness is exposed to form a dielectric isolation substrate having the p-type island element region 6. .

Finally, as shown in FIG. 1, in the p-type island-shaped element region having the p-type impurity high-concentration region 3, the lateral bipolar element 18 and the p-type impurity high-concentration region 3 having no p-type impurity high-concentration region 3 are provided. The photovoltaic diode 17 is formed in the island-shaped element region in the same manner as in the above-mentioned conventional example to complete the process.

[0026]

With the above-mentioned structure, the impurities contained in the glass are diffused through the thin oxide film during the sintering process at a high temperature for a long time, so that the single crystal silicon substrate is made of glass. Also in the dielectric isolation type semiconductor device in which the above are bonded together, the high-concentration impurity-doped region can be selectively formed. In the case of the embodiment, it is possible to prevent an increase in the base resistance of the lateral bipolar element, which is the control element, without deteriorating the performance of the photovoltaic diode.

[Brief description of drawings]

FIG. 1 is a sectional view of a dielectric isolation type semiconductor device of an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a dielectric isolation type semiconductor device showing a manufacturing method according to an embodiment of the present invention in the order of steps.

FIG. 3 is a sectional view of a conventional dielectric isolation type semiconductor device.

FIG. 4 is a cross-sectional view of a dielectric isolation type semiconductor device showing a manufacturing method of a conventional example in the order of steps.

FIG. 5 is a graph showing a p-type impurity concentration distribution in the thickness direction of a p-type island-shaped element region having a p-type impurity high-concentration region, where (a) is a conventional manufacturing method and (b) is a This is the case according to the manufacturing method of the invention.

[Explanation of symbols]

1 p-type single crystal silicon (100) substrate 2 oxide film 3 p-type impurity high concentration region 4 groove 5 isolation oxide film 6 p-type island element region 7 glass 8 single-crystal silicon substrate 9 p ⁺ type anode region 10 p-type anode Region 11 n ⁺ type cathode region 12 n ⁺ type emitter region 13 p type base region 14 n ⁺ type collector region 15 p ⁺ type base region 16 electrode 17 photovoltaic diode 18 lateral type bipolar device 19 oxide film 20 silicon nitride film

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display area H01L 29/73 // H01L 27/14 31/10 8422-4M H01L 31/10 A

Claims (1)

[Claims] 1. A step of forming a groove on one main surface of a first conductivity type single crystal silicon substrate, a step of forming an isolation insulating film on the main surface, and an impurity of the first conductivity type on the main surface. A step of depositing a glass containing, a step of heat-treating another single crystal silicon substrate to the single crystal silicon substrate via the glass, and from the other main surface of the single crystal silicon substrate in which the groove is formed. In the method of manufacturing a dielectric isolation type semiconductor device, which comprises a step of polishing until the isolation insulating film is exposed to form a plurality of island-shaped element regions, the step of forming the isolation insulating film is of a first conductivity type. In a part of the island-shaped element region having a high-concentration impurity region formed at the bottom, only the isolation insulating film on the bottom surface of the island-shaped element region is aligned so that the impurities in the glass can diffuse into the high-concentration impurity region during heat treatment. Thin shape A method for manufacturing a dielectric isolation type semiconductor device, comprising the steps of: