JPH0193132A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To improve the surface flatness of a polycrystalline silicon film by heat-treating and recrystallizing the polycrystalline silicon film after making said silicon film amorphous by a method wherein a silicon oxide film on the polycrystalline silicon film of a semiconductor device is implanted with silicon ion. CONSTITUTION:A polycrystalline silicon film 5 in specific thickness is formed on a semiconductor substrate 4 by CVD process and then the silicon film 5 is implanted with silicon ion 6 in the depth of around 1/3-2/3 of the film thickness to make the film 5 amorphous. Next, the silicon film 5 is implanted with impurity ion such as arsenic etc., to provide the film 5 with conductivity. This amorphous silicon film 5 is heat-treated in non-oxidative atmosphere to be recrystallized. Later, a silicon oxide film 9 is formed on the recrystallized layer 8 by heat-treatment in oxidative atmosphere. Finally, the surface of polycrystalline silicon film 5 is flattened.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a semiconductor device, and particularly to a method for manufacturing a semiconductor device in which a silicon oxide film is formed on a polycrystalline silicon film.

[Prior Art] In the conventional manufacturing process of semiconductor devices, the following method has been used when forming a silicon oxide film on a polycrystalline silicon film. That is, as shown in FIG.
A polycrystalline silicon film 2 is formed by a pour deposition method or the like. Next, heat treatment is performed in an oxidizing atmosphere using a thermal oxidation method to form a silicon oxide film 3 on the surface of the polycrystalline silicon film 20.

In addition, when making the polycrystalline silicon film conductive, after forming the polycrystalline silicon film 2, there is a step of implanting impurity ions such as arsenic into the polycrystalline silicon film 2 by ion implantation, and A heat treatment step for activating ions is added before the step of forming silicon oxide film 3.

[Problems to be Solved by the Invention] However, since the surface of the polycrystalline silicon film 2 formed in this manner has an uneven surface corresponding to the size of the crystal grains, this polycrystalline silicon film The uniformity of the film quality of the silicon oxide film formed on the surface of the silicon oxide film 2 deteriorates due to variations in the size of crystal grains, and the crystallinity deteriorates at the grain interface between the polycrystalline silicon film 2 and the silicon oxide film 3. . Furthermore, if a conductive film is formed on the silicon oxide film 3 in a later process, the withstand voltage may be lowered between the conductive film and the silicon oxide film 3.
There were problems such as easy leakage current.

Therefore, an object of the present invention is to provide a method for manufacturing a semiconductor device that can obtain a semiconductor device with uniform quality of the silicon oxide film formed on the surface of the polycrystalline silicon film, high breakdown voltage, and low leakage current. shall be.

[Means for solving the problem of selection points] The method for manufacturing a semiconductor device according to the present invention includes a step of forming a polycrystalline silicon film with a predetermined thickness on a semiconductor substrate;
A step of implanting predetermined silicon ions into the polycrystalline silicon film by an ion implantation method to form an amorphous layer in the polycrystalline silicon film, and heating the polycrystalline silicon film to re-form the amorphous layer. The method includes a step of crystallizing the polycrystalline silicon film, and a step of heating the recrystallized polycrystalline silicon film in an oxidizing atmosphere to form a silicon oxide film on the surface of the polycrystalline silicon film.

[Function] In the method of manufacturing a semiconductor device according to the present invention, silicon ions are implanted into a polycrystalline silicon film to make the polycrystalline silicon film amorphous, and then heat treatment is performed to recrystallize the polycrystalline silicon film. let In this recrystallization process,
Since the crystal grains of polycrystalline silicon grow larger than the crystal grains before becoming amorphous, large crystal planes are arranged on the surface of the polycrystalline silicon film, thereby improving the flatness of the surface of the polycrystalline silicon film. Therefore, the silicon oxide film formed on the polycrystalline silicon film has improved uniformity in film thickness and film quality, reflecting the surface shape of the polycrystalline silicon film.

[Example] Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1A, FIG. 1B, and FIG. 1C are manufacturing process diagrams showing a method for manufacturing a semiconductor device according to the present invention according to its manufacturing steps.

First, referring to FIG. 1A, polycrystalline silicon film 5 is formed to a predetermined thickness on semiconductor substrate 4 by CVD or the like. Next, silicon ions 6 are implanted to a depth of about one-third to two-thirds of the thickness of the polycrystalline silicon film 5 using an ion implantation method to make the polycrystalline silicon film 5 amorphous.

Next, referring to FIG. 1B, impurity ions 7 such as arsenic are implanted into polycrystalline silicon film 5 by an ion implantation method in order to make polycrystalline silicon film 5 conductive.

Further, referring to FIG. 1C, the amorphous polycrystalline silicon film 5 is heat-treated in a non-oxidizing atmosphere to be recrystallized. Thereafter, a silicon oxide film 9 is formed on the recrystallized layer 8 of the polycrystalline silicon film 5 by thermal oxidation treatment in an oxidizing atmosphere.

FIG. 2 shows a micrograph of the crystal structure of the cross section of the semiconductor device formed by the above steps. This photograph was taken using a transmission electron microscope at a magnification of 2x10'. According to this figure, in the polycrystalline silicon film 5, the recrystallized layer 8
The crystal grains have grown larger than the crystal grains in the non-recrystallized layer, and the interface between polycrystalline silicon film 5 and silicon oxide film 9 is formed flat.

Note that in the above embodiment, a method for manufacturing a semiconductor device including an ion implantation step of impurity ions in order to make the polycrystalline silicon film 5 conductive has been described. If unnecessary, the step of implanting impurity ions can be omitted. In this case as well, the same effect as described above can be obtained by recrystallizing the polycrystalline silicon film 5.

[Effects of the Invention] As described above, according to the present invention, the flatness of the surface of a polycrystalline silicon film is improved, and the thickness and quality of the silicon oxide film formed on the polycrystalline silicon film can be uniform. Therefore, a semiconductor device having high breakdown voltage, low leakage current, and high reliability can be obtained between the conductive film and the conductive film formed on the silicon oxide film in a subsequent step.

[Brief explanation of the drawing]

FIG. 1A, FIG. 1B, and FIG. 1C are manufacturing process diagrams showing the method for manufacturing a semiconductor device according to the present invention according to manufacturing steps. FIG. 2 is a micrograph showing the crystal structure of a semiconductor device manufactured according to the present invention. FIG. 3 is a schematic cross-sectional view of a semiconductor device manufactured by a conventional method. In the figure, 4 is a semiconductor substrate, 5 is a polycrystalline silicon film,
8 is a recrystallized layer of a polycrystalline silicon film, and 9 is a silicon oxide film. In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Scope of Claims] A step of forming a polycrystalline silicon film with a predetermined thickness on a semiconductor substrate, and implanting predetermined silicon ions into the polycrystalline silicon film by an ion implantation method. forming an amorphous layer; heat-treating the polycrystalline silicon film to recrystallize the amorphous layer; and heat-treating the recrystallized polycrystalline silicon film in an oxidizing atmosphere. A method for manufacturing a semiconductor device, comprising: forming a silicon oxide film on the surface of the polycrystalline silicon film.