JP2935732B2 - Method for manufacturing semiconductor device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device capable of simultaneously forming fine contact holes having good coverage in p-type and n-type semiconductor regions.

[Conventional technology]

With the miniaturization of semiconductor devices, the step coverage of Al wiring at the edge of the contact hole has been improved,
In order to improve the wiring yield and reliability, it has been widely practiced to open a contact hole in an intermediate insulating film and then reflow by heat treatment to smooth the contact shape.

As an example of a method for forming such a contact hole, a method disclosed in JP-A-62-22437 will be described with reference to FIGS. 2 (A) to 2 (C). First, as shown in FIG. 2A, a thermal oxide film 102 and a BPSG film 103 are formed on a semiconductor substrate 101.
Is formed, and the contact hole 104 is formed by anisotropic etching.
Open. Next, as shown in FIG. 2B, the semiconductor substrate 101 is heat-treated in an oxygen atmosphere at a temperature of less than 900 ° C. to form a thin oxide film 105, and further heat-treated in a nitrogen atmosphere at a temperature of 900 ° C. or more to form a BPSG film. Is performed to make the shape of the contact hole 104 smooth. At this time, especially in the contact hole in the p-type high concentration diffusion layer made of boron, the thin oxide film 105 formed at a relatively low temperature prior to the reflow causes
Outward diffusion of boron from the contact hole surface in a relatively high temperature reflow step and autodoping of phosphorus from the BPSG film 103 into the contact hole 104 are suppressed.

Next, as shown in FIG. 2C, the thin oxide film 105 in the contact hole 104 is removed, a wiring material such as Al is deposited, and then a wiring 106 is formed by patterning. According to this method, in the contact hole in the p-type high-concentration diffusion layer, a decrease in the surface concentration due to the reflow treatment is suppressed, so that the contact resistance does not significantly increase.

[Problems to be solved by the invention]

Generally, the autodoping from the BPSG film is more remarkable for phosphorus than for boron, and the outdiffusion from the diffusion layer is more remarkable for boron than arsenic. This is particularly problematic.

However, in the method disclosed in the above publication, since the p-type and n-type ion-implanted diffusion layers are oxidized under the same conditions from the same state, the n-type high-concentration diffusion layer containing arsenic as an impurity is a p-type impurity layer containing boron as an impurity. Since the oxidation rate is significantly higher than that of the high concentration diffusion layer, an extremely thick oxide film is formed in the opening in the n-type region as compared with the p-type. For this reason, when an oxide film having a thickness necessary for preventing the contact resistance from increasing in the opening in the p-type region is formed, an oxide film having a thickness larger than necessary is formed in the opening in the n-type region. When depositing a wiring material such as Al or Al, it becomes difficult to remove the oxide film in the opening.

In particular, to remove the oxide film at the opening, it is desirable to use a hydrofluoric acid-based solution because of the simplicity of the process. Therefore, there is a problem that a considerable amount of the BPSG film is etched in order to remove the oxide film in the opening of the n-type region which is formed slightly thick, and it becomes impossible to form a fine contact hole.

Further, in general, when a thick oxide film is formed in the high concentration diffusion layer, defects are likely to occur. Therefore, there is a problem that a leak current increases in an n-type region where an unnecessarily thick oxide film is formed. As described above, the method disclosed in the above publication discloses a p-type and an n-type.
It was not suitable for forming contact holes in both diffusion layers of the mold at the same time.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems in the conventional method of manufacturing a semiconductor device, and has a low contact resistance and a low leakage current at the same time for both p-type and n-type regions. An object of the present invention is to provide a method for manufacturing a semiconductor device in which a contact hole is formed.

[Means and actions for solving the problem]

In order to solve the above problem, the present invention provides an opening formed in a reflowable insulating film in an n-type semiconductor region containing arsenic by ion implantation and a p-type semiconductor region containing boron by ion implantation. A method of manufacturing a semiconductor device that makes contact with a metal wiring layer through an arsenic ion implantation, wherein an n-type semiconductor region formed by arsenic ion implantation and a p-type semiconductor region formed by boron ion implantation are formed. Selectively recrystallizing, forming an opening in the insulating film, and then heat-treating in an oxidizing atmosphere of less than 900 ° C. to form an oxide film in the opening, and in an inert atmosphere of 900 ° C. or more. Performing a reflow treatment of the insulating film.

Since the method includes the step of selectively recrystallizing the n-type semiconductor region by arsenic ion implantation, the crystallinity is impaired only in the p-type semiconductor region by boron ion implantation. In the step of forming an oxide film, the thick oxide film is not formed only by the n-type semiconductor region due to the accelerated oxidation effect of the p-type semiconductor region. At the same time, it is possible to form a good contact hole having a coverage shape.

〔Example〕

Next, examples will be described. Fig. 1 (A)-(C)
FIG. 4 is a manufacturing process diagram for describing an embodiment of a method for manufacturing a semiconductor device according to the present invention. First, as shown in FIG. 1A, a thermal oxide film 2 and an n-type semiconductor region 3 are formed on a semiconductor substrate 1 by ion implantation of arsenic, and this region 3 is recrystallized by a heat treatment. Next, a p-type semiconductor region 4 is formed by ion implantation of boron, and a BPSG film 5 is formed. Further, contact holes 6 are opened in the BPSG film 5 and the thermal oxide film 2 by anisotropic etching. Next, as shown in FIG. 1B, the semiconductor substrate 1 is heat-treated in an oxygen atmosphere at a temperature lower than 900 ° C. to form a thin oxide film 7.

At this time, in the contact hole 6 in the p-type high-concentration semiconductor region 4 due to boron, oxidation is performed in a state in which crystallinity is impaired by ion implantation, and the accelerated oxidation causes the BPSG film 5 to reflow. In a relatively high temperature heat step, the thickness is such that the outward diffusion of boron from the surface of contact hole 6 to p-type semiconductor region 4 and the autodoping of phosphorus from BPSG film 5 into contact hole 6 are sufficiently suppressed. Even when oxide film 7 is formed, an extremely thick oxide film is not formed in contact hole 6 of n-type semiconductor region 3 containing arsenic as an impurity. Then 900 ° C
The heat treatment is performed in the above-described nitrogen atmosphere to reflow the BPSG film 5 to smooth the shape of the contact hole 6.

Next, as shown in FIG. 1 (C), after removing the thin oxide film 7 of the contact hole 6 and depositing a wiring material such as Al,
The wiring 8 is formed by patterning.

In this embodiment, the BPSG film is used as the reflowable insulating film. However, a PSG film may be used as the reflowable insulating film.

Furthermore, in this embodiment, the n-type semiconductor region was recrystallized by arsenic ion implantation prior to boron ion implantation. However, since arsenic atoms are heavier than boron, There is a tendency that an amorphous layer is easily formed in the injection layer. Therefore, it is possible to recover the crystallinity at a lower temperature than the boron ion-implanted layer by the solid phase epitaxial growth. Therefore, the p-type semiconductor region by boron ion implantation and the n-type semiconductor region by arsenic ion implantation
Forming a semiconductor region and performing a heat treatment at a low temperature of, for example, about 600 ° C. to 800 ° C. prior to the opening of the contact hole to the insulating film, also selectively to the n-type semiconductor area by arsenic ion implantation. It is possible to recover the crystallinity, and by this method, an effect similar to that of the above embodiment can be expected.

〔The invention's effect〕

As described above with reference to the embodiment, according to the present invention, the crystallinity is impaired only in the p-type semiconductor region when the oxide film is formed in the opening. A thick oxide film is not formed only in the semiconductor region, thereby forming a fine contact hole having a small contact resistance and a low leakage current and a good coverage shape in both the p-type and n-type semiconductor regions. can do.

[Brief description of the drawings]

1 (A) to 1 (C) are manufacturing process diagrams for explaining one embodiment of a method for manufacturing a semiconductor device according to the present invention, and FIGS. 2 (A) to 2 (C) are conventional semiconductor devices. FIG. 7 is a manufacturing process diagram for describing the manufacturing method of FIG. In the figure, 1 is a semiconductor substrate, 2 is a thermal oxide film, 3 is an n-type semiconductor region by arsenic ion implantation, 4 is a p-type semiconductor region by boron ion implantation, 5 is a BPSG film, 6 is a contact hole, 7 is A thin oxide film 8 indicates a wiring.

Claims (3)

(57) [Claims] A metal wiring layer is formed between an n-type semiconductor region containing arsenic as an impurity by ion implantation and a p-type semiconductor region containing boron as an impurity by ion implantation via an opening formed in a reflowable insulating film. In the method of manufacturing a semiconductor device in contact, an n-type semiconductor region by arsenic ion implantation is selectively recrystallized among an n-type semiconductor region by arsenic ion implantation and a p-type semiconductor region by boron ion implantation. Forming an opening in the insulating film and then performing a heat treatment in an oxidizing atmosphere at less than 900 ° C. to form an oxide film in the opening; and reflowing the insulating film in an inert atmosphere at 900 ° C. or more. Performing a method of manufacturing a semiconductor device. 2. The step of selectively recrystallizing an n-type semiconductor region by arsenic ion implantation is characterized by arsenic ion implantation, heat treatment in an inert atmosphere, and then boron ion implantation. A method for manufacturing a semiconductor device according to claim 1. 3. The step of selectively recrystallizing an n-type semiconductor region by arsenic ion implantation is a step of implanting arsenic and boron ions and performing a heat treatment at 600 ° C. to 800 ° C. Item 2. A method for manufacturing a semiconductor device according to Item 1.