JPH0443662A - Semiconductor device and its manufacture - Google Patents

Abstract

PURPOSE:To reduce an interelement isolation width by a method wherein an oxide-film layer extended in the depth direction is formed under a selective oxide film for interelement isolation use. CONSTITUTION:An oxide film 12 is formed on the surface of a semiconductor substrate 11; a silicon nitride film 13 is deposited on the oxide film 12; an opening part is formed selectively in the part of an interelement isolation region. Then, a selective oxide film 16 is formed; the silicon nitride film 13 is removed; after that, a photomask 1 is formed; an opening part is formed selectively, by an etching operation, in a part near the center of an interelement isolation region of the photomask 1. Boron ions are implanted into the opening part to form a P-type impurity diffusion layer 2. Then, oxygen ions are implanted into the opening part of the photomask 1; an oxide-film layer 3 which comes into contact with the selective oxide film 16 and which is extended in the depth direction of the semiconductor substrate 1 is formed by an annealing operation. Then, the photomask 1 is removed; after that, an N-type impurity diffusion layer 17 to be used as a source-drain region is formed selectively. Thereby, it is possible to form the interelement isolation region whose isolation width is narrow and which does not lower the breakdown strength of elements.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is directed to LOG OS (Local Oxida
Z0 Conventional technology regarding semiconductor devices and their manufacturing methods in which element isolation regions are formed by oxidation process In recent years, isolation between circuit elements has become increasingly important as semiconductor devices become more highly integrated and densely packed. It's coming.

Conventionally, the isolation region between MOS transistors and transistor elements was
When forming by OS, a method is known in which the isolation between elements is increased by selectively injecting holons (t+) into the entire isolation region using silicon nitride and photol/cyst as masks.

Below, a conventional semiconductor device and its manufacturing method will be explained with reference to FIG.

FIG. 2 is a cross-sectional view of the element isolation region at the main process stage of a conventional semiconductor device, in which 11 is a semiconductor substrate made of P-type/recon, and 12 is an oxide formed on the surface of the semiconductor substrate. 13 is a silicon nitride film selectively formed on the surface of the oxide film 12, 14 is a photoresist film selectively formed on the surface of the silicon nitride film 13, and 15 is a P-type impurity. A diffusion layer 16 is a LOCO8 oxide film, and 17 is an N-type impurity diffusion layer selectively formed on the surface of the semiconductor substrate 11.

That is, in the conventional semiconductor device, as shown in FIG. After selectively forming openings in the photoresist film 14 and silicon nitride film 13 by photolithography and etching, boron ions are implanted to form a P-type impurity diffusion layer 15.Next, As shown in FIG.
The type impurity diffusion layer 17 was selectively formed.

Problems to be Solved by the Invention In such a conventional semiconductor device and its manufacturing method,
Since element isolation regions are formed using LOGOS oxide films, LOGOS is used to obtain sufficient element isolation when the isolation width between elements decreases due to higher integration and density of semiconductor devices.
It is difficult to optimize the thickness and horizontal alignment of the sulfur oxide film, and there is also the problem that forming a P-type impurity diffusion layer with a higher concentration than in the past lowers the breakdown voltage of the device.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a semiconductor device and a method for manufacturing the same that enable isolation between elements without increasing the horizontal placement of oxide films due to LOGOS and without lowering the withstand voltage of the elements. do.

Means for Solving the Problems In order to achieve the above object, the present invention provides a selective oxide film formed on a semiconductor substrate, and a selective oxide film formed only near the center of the selective oxide film in contact with the selective oxide film deep in the semiconductor substrate. This structure has an element isolation region formed by providing an oxide film layer extending in the horizontal direction.

Effects of the present invention With the structure described in section 2, the oxide film layer extending in the depth direction of the semiconductor substrate can provide more sufficient isolation between elements without increasing the horizontal placement of the oxide film due to LOGOS. Further, since a high concentration P-type impurity diffusion layer is not required, an isolation region between elements can be formed without lowering the withstand voltage of the element.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to FIG.

FIGS. 1+al to fd) show cross-sectional views of the element isolation region at main process steps in an embodiment of the present invention. In the figure, the same parts as those in FIG. 2 of the conventional example are given the same numbers, and the explanation will be omitted. That is, the feature of the present invention is that the oxide film 12 and the oxide film 16 formed by LOGOS in FIG.
A photomask 1 selectively formed on the surface of the r) type impurity diffusion layer 2 selectively formed using the photomask 1 as a mask, selectively formed using the photomask 1 as a mask in FIG. There is an oxide film layer 3 formed on the surface.

Next, the structure will be explained in detail together with the manufacturing method. First, as shown in FIG.
A nitride film 13 is stacked and openings are selectively formed in the inter-element isolation regions. Next, as shown in FIG. 1(l)), a selective oxide film (LOGOS oxide film) 16 is formed. - After removing the light film 13, a photomask 1 is formed and an opening is selectively formed 4 in a portion near the center of the element IUI:I) Ni region of the photomask 1 by etching. A P-type impurity diffusion layer 2 is formed by implanting boron ions into this opening. Next, as shown in FIG. 1C, oxygen ions are implanted into the openings of the photomask 1 and annealed to form an oxide film layer that comes into contact with the selective oxide film 16 and extends in the depth direction of the semiconductor substrate 1. form 3. Next, in Figure 1 fdl, iI
After removing the photomask], as in the conventional example, N type impurity diffusion layers 17 which will become source/drain regions are selectively formed. As a result, the width of the opening of the photomask 1 near the center of the element isolation region formed by the selective oxide film on the semiconductor surface is appropriately selected to suppress the lateral spread of the oxide film layer 3, and the center of the selective oxide film 6 is Since an oxide film layer 3 extending in the depth direction of the semiconductor substrate 11 is formed only in the vicinity, in contact with the selective oxide film, there is no need to increase the concentration of the P-type impurity diffusion layer 2, and the isolation width is narrow. It was possible to form an isolation region between elements without lowering the withstand voltage of the element.

Effects of the Invention As is clear from the above embodiments, according to the present invention, an oxide film layer extending in the depth direction is provided under a selective oxide film for normal isolation between elements, so that the width of isolation between elements can be reduced. It saves money,
It is possible to provide a semiconductor device whose isolation width is narrow and whose breakdown voltage does not drop, and a method for manufacturing the same.

[Brief explanation of drawings]

Fig. 1 ta+~(dl is a process cross-sectional view of the main process steps of the method for manufacturing a semiconductor device according to an embodiment of the present invention, Fig. 2 fat
, (bl is a process cross-sectional view of the main process steps of a conventional semiconductor device manufacturing method. 3... Oxide film layer, 11... Semiconductor substrate, 16... L OG Oxide film (selective oxide film) by OS. Name of agent: Patent attorney Shigetaka Awano Haka1 person 2nd j1!

Claims (3)

[Claims] (1) A selective oxide film formed on a semiconductor substrate, and an oxide film layer formed only near the center of the selective oxide film and extending in the depth direction of the semiconductor substrate in contact with the selective oxide film. A semiconductor device having an isolation region between elements. (2) The semiconductor device according to claim 1, wherein an impurity diffusion layer is provided below the oxide film layer formed extending in the depth direction of the semiconductor substrate. (3) Forming a selective oxide film as an element isolation region on a semiconductor substrate, and selectively implanting oxygen ions near the center of the selective oxide film so that the selective oxide film contacts the depth of the semiconductor substrate. A method for manufacturing a semiconductor device, comprising: forming an oxide film layer extending in a direction.