JPH0366165A - Diffusion of impurities to semiconductor substrate - Google Patents

Abstract

PURPOSE:To thermally diffuse impurities at a lower heat treatment temperature and in a short time by a method wherein a substance with a small thermal diffusion constant of the impurities is implanted deep into the bottom of an impurity region by a high-energy ion implantation method to form an impurity-diffusion stopper region. CONSTITUTION:A polysilicon electrode 3 is deposited on a gate insulating film 2 which is formed on a surface part of a semiconductor substrate 1. Then, phosphorus is implanted into the semiconductor substrate by an ion implantation method in a self- aligned manner with the polysilicon electrode (this becomes an n<-> region 5 later on). Then, ion seeds with a small thermal diffusion constant of the phosphorus are implanted into a deep part of the semiconductor substrate by a high-energy ion implantation method to form an impurity-diffusion stopper region 4. In addition, an annealing operation is executed in an atmosphere of nitrogen in order to anneal and diffuse a phosphorous implanted region to form the n<-> region 5. However, since the previously formed impurity-diffusion stopper region exists, an impurity thermal diffusion operation which is more anisotropic in a horizontal direction than in a depth direction can be executed; impurities can be thermally diffused at a lower heat treatment temperature and in a short time.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to impurities used in semiconductor devices, such as high-voltage MO3I transistors and memory cells, which are processed according to fine rules in a region where the short channel effect is significant. Concerning diffusion methods.

[Summary of the invention]

In order to perform impurity thermal diffusion with anisotropy in the horizontal direction rather than in the depth direction with lower temperature heat treatment, a substance with a small thermal diffusion constant of the impurity is added to the bottom of the impurity region formed by the ion implantation method. An impurity-diffused stosobar region was formed by deeply implanting the impurity using high-energy ion implantation.

[Conventional technology]

Figure 2 shows a double-diffused drain fabricated using a conventional method, with double-diffused regions serving as source and drain regions.
D D D
FIG. 2 is a cross-sectional structural diagram of a RAIN) type MOS) transistor. In this transistor, a gate insulating film 2 is formed on a surface portion of a semiconductor substrate 1. A polysilicon electrode 3 is deposited thereon by chemical vapor deposition (CVD). Furthermore, phosphorus is implanted into the semiconductor substrate width into this polysilicon electrode using an ion implantation method in a self-aligned manner. Next, the temperature was set at 1000°C for annealing and diffusion of this phosphorus implantation region.
Annealing is performed in a nitrogen atmosphere to form n- region 5. Then, arsenic was implanted to form n+6.

[Problem to be solved by the invention]

As described above, in the DDD type MO3) transistor, in order to improve the drain breakdown voltage, it is necessary to lengthen the diffusion length Xj of the n- region to create a gentle impurity profile to relax the electric field in the drain region. In this n-region thermal diffusion, normally 20 to 30
However, high-temperature heat treatment at 1000° C. causes large thermal diffusion in the source and drain regions, causing short channel effects such as punch-through, making it extremely difficult to fabricate fine transistors.

[Means to solve the problem]

In order to solve the above-mentioned problems, in the present invention, in order to perform impurity thermal diffusion with anisotropy in the horizontal direction rather than in the depth direction at a lower heat treatment temperature, an impurity region formed by an ion implantation method is An impurity diffusion stopper region was formed by deeply implanting a material with a small impurity thermal diffusion constant into the bottom using high-energy ion implantation.

[Effect]

As mentioned above, by deeply implanting a material with a small thermal diffusion constant of the impurity into the bottom of the impurity region formed by the ion implantation method, using the high energy ion implantation method,
By forming an impurity diffusion layer region, it is possible to perform anisotropic impurity thermal diffusion in which thermal diffusion is faster in the horizontal direction than in the depth direction, making it possible to perform impurity thermal diffusion in a shorter time at a lower heat treatment temperature. . Therefore, it has become possible to suppress the short channel effect caused by microfabrication.

〔Example〕

Embodiments of the present invention will be described in detail below based on the drawings. FIG. 1 is a cross-sectional structural diagram of a DDD type MO3) disk manufactured using the impurity diffusion method of the present invention. In this transistor, a gate insulating film 2 is formed on a surface portion of a semiconductor substrate 1. On top of that, polysilicon electrode 3
is deposited by CVD method. Next, phosphorus is implanted into the semiconductor substrate into this polysilicon electrode by an ion implantation method in a self-aligned manner (later, it becomes an n-%l region 5). Here, ion species with a small thermal diffusion constant of phosphorus, such as oxygen or nitrogen, are implanted into the deep part of the semiconductor substrate using a high-energy ion implantation method.
form. Furthermore, annealing was performed in a nitrogen atmosphere for annealing and diffusion of the phosphorus implant region.
form.

However, due to the previously formed impurity diffusion stopper region,
Since impurity thermal diffusion can be performed with more anisotropy in the horizontal direction than in the depth direction, impurity thermal diffusion can now be performed at lower heat treatment temperatures and in a shorter time.

Therefore, it becomes possible to suppress the short channel effect caused by microfabrication. Then, arsenic is implanted into the n″ region 6.
was formed.

〔Effect of the invention〕

As explained above, the method for diffusing impurities into a semiconductor substrate of the present invention is to deeply implant a substance with a small thermal diffusion constant of the impurity into the bottom of the impurity region formed by the ion implantation method using a high energy ion implantation method. By forming an impurity-diffusion stratobar region, it is possible to perform anisotropic impurity diffusion in which thermal diffusion is faster in the horizontal direction than in the depth direction, making it possible to perform impurity thermal diffusion in a shorter time at a lower heat treatment temperature. . Therefore, it has become possible to suppress the short channel effect caused by microfabrication.

[Brief explanation of drawings]

Figure 1 is a cross-sectional structural diagram of a DDD type MO3) transistor manufactured using the method of diffusing impurities into a semiconductor substrate according to the present invention, and Figure 2 is a cross-sectional diagram of a DDD type transistor manufactured using the conventional method of diffusing impurities into a semiconductor substrate. FIG. 2 is a cross-sectional structural diagram of a type MOS transistor. Semiconductor substrate gate insulating film polysilicon electrode impurity diffusion layer region n- region 6 ・On n° region

Claims (1)

[Claims] In a semiconductor element in which a diffusion region is formed by implanting an impurity near the surface of a semiconductor substrate using an ion implantation method and thermally diffusing the impurity, the impurity is thermally diffused into the bottom of the impurity region into which the impurity is implanted by the ion implantation method. An impurity diffusion stopper region is formed by deeply implanting a material with a small constant using high-energy ion implantation, and when subsequent impurity thermal diffusion is performed, an anisotropic impurity that causes greater thermal diffusion in the horizontal direction than in the depth direction. An impurity diffusion method that enables low-temperature processing due to the effect of thermal diffusion.