JPS60257541A - Production of semiconductor device - Google Patents

Abstract

PURPOSE:To prevent an SiO2 film from being etched during epitaxial growth as well as to reduce defects in the periphery having vertical walls and surrounded by the isolating oxide film and by providing a thin insulating film containing no oxygen on the surface of the inner wall of the aperture and the upper face of the SiO2 film, and then forming an active region by causing Si to grow epitaxially. CONSTITUTION:An SiO2 film 2 is formed on an Si substrate 1 and provided with an aperture 3 by anisotropic etching such that the aperture has vertical walls. The upper face of the SiO2 film 2 and the internal wall faces of the aperture are covered with an insulating film containing no oxygen, e.g. with an Si3N4 film 5, such that a second aperture 6 is provided within the aperture 3 while a part of the Si substrate 1 is exposed on the bottom of the aperture. An Si layer 4 is then selectively caused to grow epitaxially within the second aperture 6. Subsequently, protruded portions of the epitaxially grown Si layer 4 and the Si3N4 film 5 on the upper face of the SiO2 are removed by polishing so as to flatten the surface and to obtain an active region 4a. In this manner, the aperture walls are not etched any way during the epitaxial growth, and therefore the verticality of the walls can be maintained.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for obtaining an active region structure surrounded by an isolation oxide film with vertical walls in order to reduce the isolation width between elements. It is something.

[Prior art]

As the integration of semiconductor devices progresses, there is a demand for increasingly narrower isolation widths between elements. Figures 1A to 1C are cross-sectional views showing the main stages of a conventional method developed in response to such demands.First, as shown in Figure 1A, a silicon (8i) substrate (1) is Silicon oxide (S 10
2) Form a membrane (2) and form an opening (3) in a part of it. Subsequently, as shown in FIG. 1B, an epitaxially grown Si layer (4) is selectively formed in the opening (3), and then, as shown in FIG. 1C, an epitaxially grown Si layer (4) is formed by polishing. ) is removed to flatten the upper surface to obtain an active region (4a).

In order to narrow the isolation width between elements, it is desirable that the walls of the isolation oxide film be vertical, and even with the conventional method described above, an anisotropic dry etching method or anisotropic dry etching method is used to form the opening (3) at the stage shown in FIG. 1A. 8 using ion beam etching method as shown in the figure.
1 A wall surface perpendicular to the surface of the substrate (1) has been obtained, but at the stage shown in FIG.
The io2 film (2) undergoes etching. That is, for example, monosilane (S1a 4
) , ) Lichlorosilane (siHc13).

Dichlorosilane (SiH2C70) + monochlorosilane (S 1H3CZ), silicon tetrachloride (S I C7
A large amount of hydrogen (H2) gas is flowed to decompose Si-containing gases or liquids such as 0). Therefore, S10□ and 8
1 reacts with silicon monoxide to form silicon monoxide (SiO). 8i0 is vaporized and discharged. In the case of FIG. 1B, at the initial stage of epitaxial growth, Si is deposited while S10□ is slightly etched. This SiO2 Si
Since the etching by O oxide and the epitaxial growth of 81 proceed simultaneously, the amount of etching of SiO2 increases from the bottom to the top of the SiO3 film (2), and the vertical wall surface of the SiO2 film (2) increases. gradually becomes rounded, which becomes an obstacle to reducing the isolation width between elements. In addition, the above SiO gas cannot be completely removed, but is taken into the nearby Si, so oxygen precipitation nuclei are formed and grown by high-temperature heat treatment, and the defect density increases due to the difference in lattice constant from Sl. do. Therefore, the aperture (
Since a defect layer with a width of about 1 μm is generated around 3),
When a pn junction is formed, there is also the problem that junction leakage tends to occur.

[Summary of the invention]

This invention has been made in view of the above points, and after forming an opening in which an active region is to be epitaxially grown in an 8 x O2 film constituting a separation layer, 1. By forming a thin insulating film that does not contain oxygen on the top surface and then epitaxially growing Si to form an active region, etching of the SiO2 film during epitaxial growth is prevented, and an isolation oxide film on the straight wall surface is formed. The present invention provides a method for obtaining an active region structure with fewer defects even in the surrounded peripheral portion.

[Embodiments of the invention]

FIGS. 2A to 2D are cross-sectional views showing the main stages of a method according to an embodiment of the present invention, and the same reference numerals as in the conventional example indicate equivalent parts. First, as shown in FIG. 2A, S
1 csio on the i board (1). To form the film (2), an insulating film that does not contain oxygen, such as silicon nitride (813N4), is used.
Covering the top surface of the SiO3 film (2) and the inner wall surface of the opening (3) with the membrane (5), leaving a second opening (6) inside thereof,
A part of the Efi substrate (1) is exposed on the bottom surface.

This second aperture (6) is then opened as shown in Figure 2C.
An epitaxially grown Si layer (4) is selectively formed on the portion of
The 513N4 film (5) on the upper surface of the 02 film (2) is removed to flatten the upper surface to obtain an active region (4a).

In the method of this embodiment, before forming the epitaxially grown S1 layer (4) at the stage of FIG.
) is coated on the surface of the SiO□ film (2) around the Si3N4 film (5
) is formed, which does not contain oxygen,
Moreover, it prevents the 5102 film (2) from coming into contact with the gas or liquid for epitaxial growth, making it easier to use than conventional SiO3.
+81 does not react with H2 to form a Si layer, and the verticality of the wall surface of the second opening (6) can be maintained. In addition, the epitaxial growth S1 layer (4
) has no oxygen auto-diffusion at the edges, resulting in high quality with few defects. Therefore, in the active region thus obtained, even when a pn junction is formed, leakage current does not occur, and an excellent junction can be formed.

In this way, the emitter-collector piping phenomenon, which is particularly problematic in bipolar devices, is not only prevented, but also an excellent isolation zone with low leakage is obtained even in MO3 devices.

Furthermore, when configuring memory elements, the "groove isolation method" has traditionally been used, especially for the purpose of increasing memory capacity, but this method involves etching a portion of Si vertically and narrowly to form an oxide film or other layer. A capacitor is constructed by embedding an insulating film, but in principle it is difficult to perform high-speed etching of Sl, and it is also difficult to finish the etched shape sufficiently vertically to the bottom. .

Therefore, if the present invention is applied to this case, a high-quality insulating film with vertical walls, which could not be obtained conventionally, can be obtained, making it possible to construct an excellent capacitor and create a large-capacity memory with a small chip size. realizable.

〔Effect of the invention〕

As explained above, in the method of the present invention, the inner wall surface of the opening formed in the SiO2 film and the upper surface of the 5102 film are covered with an oxygen-free insulating film, and then Si is epitaxially grown inside the opening. During epitaxial growth, verticality can be maintained without etching on the wall surfaces of the openings, and an improvement in the degree of integration can be expected for both bipolar and MO3 structures.

1' It is also possible to form the entire insulating film with an insulating film that does not contain oxygen, but this poses problems in terms of opening etching speed and opening finish shape. This also solves this problem.

[Brief explanation of drawings]

1A to 1C are sectional views showing the main steps of a conventional method, and FIGS. 2A to 2D are sectional views showing the main steps of a method according to an embodiment of the present invention. In the figure, (1) is a silicon (semiconductor) substrate, (2)
(3) is a silicon oxide film, (3) is an opening, (4L (4a) is an epitaxially grown silicon layer, and (5) and (5a) are silicon nitride films. Note that the same reference numerals in the figures indicate the same or corresponding parts. Agent Masuo Oiwa Figure 1 Figure 2

Claims (3)

[Claims] (1) A silicon oxide film is formed on the entire surface of a semiconductor substrate, an opening is formed in a desired portion of the silicon oxide film, the semiconductor substrate is exposed on the bottom surface of the opening, and the silicon oxide film is formed on the inner wall surface of the opening and After covering the silicon film with an oxygen-free insulating film, silicon is epitaxially grown on the insulating film to a thickness equal to or greater than the depth of the opening, and the upper surface is further polished to planarize it. A method for manufacturing a semiconductor device, characterized in that the silicon oxide film and the insulating film on the inner wall surface of the opening are formed as an isolation insulating film of a silicon layer epitaxially grown in the opening. (2) The method of manufacturing a semiconductor device according to claim 1, wherein an anisotropic etching method is used to form the openings in the silicon oxide film. (3) A method of manufacturing a semiconductor device according to claim 1 or 2, characterized in that a silicon nitride film is used as the oxygen-free insulating film.