JPS5839014A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To remove the lattice defect of the titled device by a method wherein the distortion generated due to the difference in the coefficient of thermal expansion between the silicon substrate and the oxide film at the circumferential part of the silicon oxide film is reduced. CONSTITUTION:After ions are implanted, the silicon oxide film 2 located on the whole surface of the silicon substrate 1 is removed, a new silicon oxide film 5 is grown in vapor-phase on the whole surface of the silicon substrate 1, and then the above is annealed by performing heat treatment at 1,000 deg.C in a nitrogenous or oxygenous atmosphere for thirty minutes. In this case, as the annealing is performed in the state wherein no aperture is provided on the silicon oxide film, the thermal distortion which will be generated in the vicinity of the aperture can be prevented, thereby enabling to sharply reduce a leakage current.

Description

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

Recently, ion implantation technology has come to be widely applied in the manufacturing process of semiconductor devices.

In medium to high concentration ion implantation with an implantation amount of 3XIQ cm-2 or more, the junction leakage current is often one to two orders of magnitude larger than that in the thermal diffusion method.

That is, in the conventional manufacturing method, as shown in FIG.
A silicon oxide film 2 is formed on the surface of the silicon substrate 10 by thermal oxidation or vapor phase growth, and then an opening 3 is formed by photoetching, and then boron, which is a PWi impurity, is deposited at an accelerating voltage of 50 kV, for example. Injection amount 1×1015c
m′ ion implantation.

At this time, lattice defects are distributed on the surface side of the implanted region, as schematically shown by black dots. Thereafter, it is lightly oxidized for 10 minutes in an oxygen atmosphere at 1000° C. (to prevent boron atoms from jumping out from the surface), and then annealed for 50 minutes in a nitrogen atmosphere.

When stretched, as shown in Figure 2, lattice defect #1 almost disappears, but strain stress due to the difference in thermal expansion coefficient with silicon substrate 1 is concentrated in the peripheral area 4 of the opening of silicon oxide 1!2. Therefore, it is considered that lattice defects generated by ion implantation grow into a dislocation network around the silicon-oxide film interface, causing a P-N junction leakage current. Here, the silicon oxide film 2 is used as an ion implantation mask.
Even with the use of a silicon nitride film, it has not been possible to solve the problem of leakage current, and with such an implantation amount, a photoresist with no heat resistance cannot be used as an ion implantation mask.

The present invention provides a manufacturing method that can eliminate crystal defects that cause junction leakage current as described above.

The present invention eliminates lattice defects by reducing the strain caused by the difference in thermal expansion coefficient between the silicon substrate 1 and the silicon oxide film 2, which the peripheral portion 4 of the silicon oxide film 20 receives due to heat treatment. An example will be described below.

Example 1: After the ion implantation is completed as shown in the tX1 diagram, the silicon oxide film 2 is completely removed, and a new silicon oxide film 5 is grown in a vapor phase on the entire surface of the silicon substrate 1 as shown in FIG. , e.g. 3 in a nitrogen or oxygen atmosphere at 1000°C.
Annealing is performed by heat treatment for 0 minutes. In this case, since the silicon oxide film is annealed without any openings, the thermal strain that occurs near the openings described above is eliminated.
Leakage Example 2 After the ion implantation is completed as shown in FIG. 1, the process is carried out in the same manner as in Example 1 in the state shown in FIG. 4 until t when the oxide film 2 is removed.
7) Similar effects can be obtained by performing annealing under different conditions. However, in this case, since the silicon substrate surface is exposed, the implanted boron jumps out and re-diffuses into the unimplanted silicon surface layer 6.
The surface layer 6 may be thermally oxidized in a subsequent process, the surface concentration of the implanted region 3 and the surrounding surface layer 6 may not be significantly different, or the annealing atmosphere may be an oxidizing atmosphere such as oxygen. Either condition is required. In addition.

As an annealing method in the above case, a method of irradiating with a high-power laser, flood light, electron beam, etc. may be used. In these cases, the irradiation time is short, so the boron does not jump out, and the above-mentioned The following conditions are no longer necessary.

By implementing any of these embodiments), it has become possible to reduce junction leakage current in the ion implantation region.

[Brief explanation of drawings]

Figures 1 and 2 are cross-sectional views showing the conventional manufacturing method;
FIG. 4 is a sectional view showing an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1...Silicon substrate, 2...Silicon oxide film, 3...Opening, 4...Periphery of opening, 5...・New silicon film, 6.
...The surroundings are injected and the 4th

Claims (1)

[Claims] A step of ion-implanting impurities into the substrate through an opening provided in a part of a thin film on the entire surface of the semiconductor substrate, a step of completely removing the thin film, and annealing to damage the crystals on the surface of the substrate. 1. A method of manufacturing a semiconductor device, comprising a step of recovering .