JPH01232737A - Manufacture of semiconductor element - Google Patents

Abstract

PURPOSE:To restrain the diffusion amount of an impurity diffused layer in the lateral direction and to augment the integration by a method wherein an N type epitaxial layer is selectively oxidized using a nitride film on an impurity diffused layer as a mask to advance the diffusion of the impurity diffused layer as well as an oxide film is formed on a substrate. CONSTITUTION:The surface of an N type epitaxial layer 11 in the region wherefrom a nitride film 14 is etched away is etched in around 1mum and simultaneously a boron diffused layer 13 diffused in the etching region is further etched away. Next, after removing a photoresist 15 using an organic solution, the layer 11 is selectively oxidized using the nitride film 14 as a mask. Thus, the boron diffused layer 13 is further diffused reaching a P type substrate 10 to isolate the N type epitaxial layer simultaneously forming an oxide film 16 in around 2mum in the selective oxide region on the N type epitaxial layer 11. The diffusion coefficient in the boron oxide film 16 being larger than that in silicon, the boron on the interface oxide film 16 is absorbed into the oxide film 16 during the deposition of the oxide film 16 so that the boron concentration in the boron diffused layer 13 near the oxide film 16 in the selective oxide region may be reduced to decrease the diffusion amount in the lateral direction.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for manufacturing a semiconductor device.

[Conventional technology]

Conventionally, this type of manufacturing method was used in the 1986 IEICE General National Conference Lecture Proceedings Volume 9 Volume 2:・So-)2.N1
1504 Study of high alcohol pressure BiCMO8, pp. 2-262.”
The method disclosed in 2003 is described below with reference to a process diagram shown in FIG.

First, as shown in FIG. 2 (aJ), on the surface of a predetermined portion of the N-type epitaxial layer 2 formed on the P-type substrate 1, a surface oxide film 3 with a diffusion window 3a opened therein was used as a diffusion mask, and 10
BC4s at 00℃? Boron as a P-type impurity is diffused in a mixed gas atmosphere of 'h and 02 to form a zolon diffusion layer 4.

Thereafter, as shown in FIG. 2(b), after removing the boron glass formed on the surface of the P-type substrate 1 with a hydrofluoric acid solution, an annealing treatment is performed to form a boron diffusion layer (impurity layer) 4.
reaches the P-type substrate 1, and the N-type substrate 2 taxial layer 2
t - electrically isolated.

In this case, as the thickness of the N-type epitaxial layer 2 increases, the annealing treatment conditions require a high temperature and a long time.

For example, when the thickness A of the N-type epitaxial layer 2 is about 13 μm, heat treatment at 1200° C. for about 5 hours is required.

[Problems to be Solved by the Invention] However, in the above-mentioned conventional method, during heat treatment,
The boron diffusion layer 4Vi is also diffused in the lateral direction, and its width B is approximately 0.8 times the width A in the vertical direction, that is, the thickness of the N-type epitaxial layer 2.

Therefore, the lateral width υ width B of the impurity layer 4 dividing the N-type epitaxial layer 2 of about 13 μm is about 10 μm. Therefore, the width of the separation layer, the so-called impurity layer 4, is a large value equal to the width of the diffusion window 3a of the diffusion region opened in the surface oxide film 3 used as a diffusion mask plus 20 μm. The problem was that it was difficult.

In view of the above-mentioned problems, the present invention provides a method for manufacturing a semiconductor device that suppresses lateral diffusion of an impurity layer, reduces the area of an isolation region, and allows miniaturization of the device.

[Means to solve the problem]

In order to achieve the above-mentioned object, the present invention comprises a step of forming an impurity diffusion layer on a predetermined portion of a substrate, a step of forming a nitride film on all or a portion of the impurity diffusion layer, and a step of forming an impurity diffusion layer on a predetermined portion of a substrate. Using the film as a mask, the surface of the substrate is etched to a thickness equal to or greater than the thickness of the impurity diffusion layer. Using the nitride film as a mask, selective oxidation is performed to progress the diffusion of the impurity diffusion layer, and the surface of the substrate is etched. The method includes a step of forming an oxide film, and then a step of removing the nitride film.

[For production]

In the present invention, selective oxidation is performed as a full mask of the nitride arsenic film on the impurity diffusion layer to promote diffusion of the impurity diffusion layer, and an oxide arsenic film is formed on the substrate, so that the substrate is separated and The impurities at the oxide film interface are sucked into the oxide film by VC, the impurity concentration of the impurity diffusion layer near the oxide film becomes low, and the amount of lateral diffusion of the impurity diffusion layer decreases.

〔Example〕

Hereinafter, one embodiment of the method of the present invention will be described with reference to a process diagram shown in FIG.

First, as shown in FIG. 1 (aJ), on the N-type epitaxial layer 11 with a concentration of I x 1015 cm-3 and a thickness of 6 to 8 μm on the P-type substrate 10, a surface oxidation film was formed with a diffusion window 12a opened at a predetermined portion. Using the film 12 as a mask, heat treatment is performed in an atmosphere containing zolon to diffuse high concentration boron JWJ13
form. At that time, the concentration of the boron diffusion layer 13 is approximately I
It is approximately X 10'' to 8 X 1021α-3.

Next, as shown in FIG. 1(b), after removing the surface oxidized arsenic film 12 with a hydrofluoric acid bath, a layer of 1000 to 2000':A thickness is deposited on the N-type epitaxial layer 11 using the CVD method. nitrogen f
A fillet film 14 is formed. Thereafter, using photolithography, a predetermined portion of the nitride film 14 on the boron diffusion layer 13 is coated with, for example, EAM.
A photoresist 15 having a width of 5,000 to 10,000 Å thick is formed.

Thereafter, as shown in FIG. 1C, the substrate 10 is inserted into a fluorine-based gas activated by high frequency discharge or the like, and the nitride film 14 is etched away.

Subsequently, as shown in FIG. 1(d), the surface of the N-type epitaxial layer 11 in the region where the nitride film 14't has been etched is removed by etching by approximately 1 μm, and at the same time, the boron diffusion layer 13 that had been diffused in the etched region is removed. Also removes. In this case, similarly to the etching removal of the nitride film 14, the vaporization of silicon by activated fluorine gas may be used, or the nitride film 1 remaining after etching may be removed.
4 may be used as a mask and the melting phenomenon of silicon may be utilized in an alkaline solution.

Next, as shown in FIG. 1(e), after removing the photoresist 15 with an organic solution, using the nitride film 14 as a mask, selective acid atomization is performed for about 5 hours in a steam atmosphere at 1200 DEG C., for example. In this way, the diffusion of the zolon diffusion layer 13 progresses and reaches the P-type substrate 10, and the N-type epitaxial layer 11'f! : Separation and N-type epitaxial layer 1
An oxide film 16 having a thickness of approximately 2 μm is formed in the selective oxidation region on the oxide film 1 . The diffusion coefficient of boron in the arsenic oxide film 16 is larger than that in silicon, so when the arsenic oxide film 16 grows, boron at the interface of the oxide film 16 is absorbed into the oxide film 16, and the selective oxidation area Goron diffusion layer 13 near the oxide film 16 of
As the poron concentration becomes smaller, the amount of lateral diffusion decreases. Therefore, the width C of the poron diffusion layer 13 in the lateral direction is
is small, for example, in the case of this embodiment, about 5μ.

Thereafter, as shown in FIG. 1 (fJK), the nitride film 14 used as a mask for selective oxidation is removed using, for example, a phosphoric acid solution at about 170° C. to complete the semiconductor device.

〔Effect of the invention〕

As explained above, according to the present invention, selective oxidation is performed using the nitride film on the impurity diffusion layer as a mask to advance diffusion of the impurity diffusion layer, and an oxide film is formed on the substrate.
Impurities at the oxide film interface are sucked into the oxide film, and the amount of diffusion in the lateral direction of the impurity diffusion layer is suppressed, reducing the area of the impurity diffusion layer (separation region) and making the device smaller. Accordingly, the degree of integration can be improved. Further, since selective oxidation is performed on the surface of the substrate that has been removed by etching, the above-mentioned problem can be solved by the unique effect that the surface of the substrate can be flattened.

[Brief explanation of the drawing]

FIG. 1 is a process diagram of an embodiment of the method of the present invention, and FIG. 2 is a process diagram of a conventional method. lO...P type substrate, 11...N type epitaxial layer, 12...surface oxide film, 12a...diffusion window, 13...
... Poron diffusion layer, 14... Nitride film, 15... Photorenost, 16... Oxide film. Patent applicant: Oki Electric Industry Co., Ltd. Figure 1 Figure 1

Claims (1)

[Claims] A step of forming an impurity diffusion layer at a predetermined portion on a substrate; a step of forming a nitride film on all or part of the impurity diffusion layer; and a step of forming an impurity diffusion layer on the substrate using the nitride film as a mask. etching the surface to a thickness greater than the thickness of the impurity diffusion layer; selectively oxidizing the nitride film using the nitride film as a mask to advance diffusion of the impurity diffusion layer and forming an oxide film on the substrate; A method for manufacturing a semiconductor device, comprising: a step of removing the nitride film.