JPH0719836B2 - Method for manufacturing dielectric-isolated semiconductor device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for manufacturing a dielectric isolation type semiconductor device in which elements are isolated using a dielectric.

[Technical background of the invention and its problems]

Compared to pn junction isolation, the so-called dielectric isolation method in which conventional ICs and LSIs are used to isolate elements from each other with an insulator can (1) greatly reduce leakage current, and (2) increase breakdown voltage. It has advantages such as that (3) it is not necessary to pay attention to the direction of voltage application.

The ideal dielectric isolation is achieved by completely wrapping each element with an insulator except for the electrode connections. Such an element can be formed using, for example, an SOS substrate in which silicon is epitaxially grown on sapphire. However, sapphire is expensive, and the crystal matching with silicon is not perfect, so that a high-quality single crystal film cannot be obtained, and the film thickness cannot be increased sufficiently. There is a limit.

Many dielectric isolation methods that do not use an insulating substrate such as sapphire have been proposed so far. One example thereof will be described with reference to FIGS. 2 (a) to (e). First, as shown in FIG. 2A, a desired diffusion layer 43 (43 ₁ , 43 ₂ ) is formed on a silicon single crystal layer 42 (42 ₁ , 42 ₂ ) formed on a silicon single crystal substrate 41 by an epitaxial method. A device having
Furthermore, each element is separated by mesa etching and the entire surface is
Cover with an insulating film 44 such as O ₂ . Thereafter, as shown in FIG. 2 (b), a polycrystalline silicon support layer 45 is deposited on these elements, and then a silicon substrate 41 is formed as shown in FIG. 2 (c).
Are ground by polishing or etching until each element is completely separated, and the surface thereof is covered with an insulating film 46. Second after this
As shown in FIG. 3D, the polycrystalline silicon support layer 47 is deposited again on the insulating film 46 side. Then, as shown in FIG. 2 (e), the support layer 45 is removed by etching to obtain a dielectrically separated element.

The biggest problem with such a conventional method is that the formation of a support layer is essential. Not only extra steps such as deposition and removal of the support layer are required, but also in the case of commonly used polycrystalline silicon, since the deposition rate is slow, a sufficient thickness to withstand the steps such as polishing is obtained. It takes a very long time. For the purpose of omitting the step of depositing the support layer, it has been proposed to complete the element isolation in the step of FIG. 2C and take out the wiring from the back surface of the element. However, in this method, the wiring structure becomes complicated and various constraints are newly added. A method of attaching a silicon substrate or the like as a support through an adhesive layer such as oxide or glass has also been proposed, but in this method, a temperature exceeding 1300 ° C. and several tens kg / cm ^{2 are used.}
The above high pressure was required. Under such a condition, the substrate may be deformed due to creep or the like, and the impurity distribution of the diffusion layer formed in the element region may be changed.

[Object of the Invention]

The present invention has been made in view of the above points, and an object of the present invention is to provide a method of manufacturing a semiconductor device capable of highly reliable dielectric isolation with simple steps.

[Outline of Invention]

According to the present invention, when the surfaces of two semiconductor single crystal substrates are mirror-polished to be sufficiently smooth, a strong substrate bonded body can be obtained by directly adhering the polished surfaces to each other in a sufficiently clean atmosphere. Based on our findings, we apply this technique to dielectric isolation. According to the present invention, an oxide film is formed on the mirror surface of at least one of the first and second semiconductor substrates that have been mirror-polished, and the mirror surfaces are made to face each other through the oxide film to be in close contact with each other. A bonding step of bonding the second semiconductor substrate; a heat treatment step of heating the substrate bonded body obtained in the above step to 200 ° C. or higher; a step of making the first semiconductor substrate have a desired thickness; 1. A method for manufacturing a dielectric isolation type semiconductor device, comprising: a step of epitaxially growing a semiconductor layer on a surface of a first semiconductor substrate; and a step of burying an insulator that penetrates the semiconductor layer and the first semiconductor substrate and reaches the oxide film. In the step 1, after forming the desired thickness of the first semiconductor substrate, an isolation groove for isolating the first semiconductor substrate into island-shaped semiconductor regions is formed, and an insulator is embedded in the isolation groove. The semiconductor Is epitaxially grown to form an isolation groove in the semiconductor layer, and an insulator is embedded in the isolation groove to connect with the insulator in the isolation groove formed in the first semiconductor substrate to form the semiconductor layer and the first semiconductor. A method of manufacturing a dielectric isolation type semiconductor device, which comprises forming an insulator penetrating a substrate.

〔The invention's effect〕

According to the present invention, since a step of depositing or removing a support layer such as polycrystalline silicon is not used and there is no problem due to occurrence of warpage, a semiconductor device in which element isolation is performed is obtained very easily. be able to. The thickness of the semiconductor crystal layer can be increased by sequentially forming the grooves. Furthermore, since the surface is flat, wiring can be facilitated.

Example of Invention

Embodiments of the present invention will be described below with reference to the drawings. 1 (a) to (k) show an embodiment of a photodiode array using the present invention. Single crystal substrate 11 and N-type second silicon single crystal substrate 12 having a surface index of 100 and a resistivity of 0.03 Ω-cm or less
To prepare. In this example, a first insulating film 13 such as an oxide film is formed on the surface of the second silicon substrate 12. The opposite surfaces of these substrates are mirror-polished. These substrates 11 and 12 are brought into close contact with each other as shown in FIG. 1 (b) and heat-treated at a temperature of 200 ° C. or more to join them. Although it is possible to obtain a considerable bonding strength just by bringing them into close contact at room temperature, the heat treatment at 200 ° C or higher significantly improves the bonding strength. However, the upper limit of heat treatment temperature is to prevent creep etc.
It is necessary to set the temperature to 1300 ° C.

In the present embodiment, the substrate bonded body thus formed is
An epitaxial film is formed on 12. Therefore, as shown in FIG. 1 (c), the substrate 12 is scraped off by polishing, etching or the like until the required thickness is obtained. Next, as shown in FIG. 1D, a part of the surface of the substrate 12 is covered with a resist film, an oxide film or the like to form a groove having a width of 1 to 2 μm by the anisotropic etching until the first insulating film 13 is reached. Then, thereafter, as shown in FIG. 1E, an oxide film is formed under the condition that the groove is filled with the second insulating film 14. Further, as shown in FIG. 1 (f), a generally known PEP process is performed to remove the oxide film having a width of 5 μm, which is slightly larger than the groove width.

Next, as shown in FIG. 1 (g), an N-type epitaxial growth film 15 of a third semiconductor crystal having a lower impurity concentration than that of the substrate 12 is formed thereon to a desired thickness.

Next, as shown in FIG. 1 (h), an epitaxial growth film 15 is formed.
A groove having a width of 1 to 2 μm is formed right above the second insulating film 14 on the surface of the substrate by anisotropic etching again until the insulating film 14 is reached. After that, the groove is formed as shown in FIG. 1 (i). An oxide film is formed so as to be filled with the third insulating film 16. In a part of the substrate 15 thus formed, N-type impurities such as phosphorus are selectively diffused until reaching the substrate 12, and then P-type impurities such as boron are selectively diffused to form the P layer 18. To get About 10 μm of aluminum is used to connect the photodiodes (Fig. 1 (j)) configured in this way in series.
To form a wiring 19, and a desired semiconductor device as shown in FIG. 1 (k) is completed.

As described above, according to this embodiment, a highly reliable semiconductor device having a dielectric isolation structure can be easily manufactured.

The greatest feature of the present invention is that semiconductor crystals having a desired impurity concentration and thickness can be stacked in multiple layers on a semiconductor single crystal substrate directly bonded through an insulating film. Further, by changing the wiring shape, it is possible to easily connect the separated elements in series or in parallel.

Although the present invention describes the photodiode in the above embodiment, a transistor, a thyristor, a MOS FET or the like can be formed. Further, in forming the groove for burying the insulator, if a groove in one direction is not formed, an adjacent semiconductor device can be electrically connected arbitrarily.

In this embodiment, the semiconductor single crystal substrate directly bonded through the insulating film has been described. However, oxygen is ion-implanted into the semiconductor single crystal to form the insulating film in a region shallower than the surface, The same effect can be obtained by stacking semiconductor crystals by epitaxial growth.

[Brief description of drawings]

FIG. 1 is a diagram showing a device manufacturing process of an embodiment of the present invention, and FIG. 2 is a diagram showing a device manufacturing process by a conventional dielectric isolation method. 11 …… First silicon single crystal substrate 12 …… Second 〃13 …… First insulating film 14 …… Second 〃15 …… Epitaxial growth film 16 …… Third insulating film 17 …… N type Diffusion layer 18 …… P-type diffusion layer 19 …… Wiring electrode

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yu Shinbo 1 Komukai Toshiba-cho, Saiwai-ku, Kawasaki-shi, Kanagawa Toshiba Research Institute Ltd. (56) Reference JP-A-56-155547 (JP, A) Japanese Patent Publication Sho 49-26455 (JP, B1)

Claims (1)

[Claims] 1. An oxide film is formed on the mirror surface of at least one of the first and second semiconductor substrates that have been mirror-polished, and the mirror surfaces are made to face each other through the oxide film and are brought into close contact with each other. And a joining step of joining the second semiconductor substrate; a heat treatment step of heating the substrate joined body obtained in the above step to 200 ° C. or higher; a step of making the first semiconductor substrate have a desired thickness; Epitaxially growing a semiconductor layer on the surface of the first semiconductor substrate; the semiconductor layer and the first semiconductor layer;
And a step of burying an insulator that penetrates the semiconductor substrate and reaches the oxide film. After the step of adjusting the thickness of the first semiconductor substrate to a desired thickness, A groove for separating the first semiconductor substrate into island-shaped semiconductor regions is formed, an insulator is embedded in the separation groove, and then the semiconductor layer is epitaxially grown to form a separation groove in the semiconductor layer. A dielectric isolation, characterized in that an insulator is embedded and is connected to an insulator in a separation groove formed in a first semiconductor substrate to form an insulator penetrating the semiconductor layer and the first semiconductor substrate. Method of manufacturing a semiconductor device.