JPH03165516A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To completely destroy the natural oxide film generating between a silicon substrate and a polycrystalline silicon film even on a contact part having a narrow groove width, and to make it possible to suppress the contact resistance on an interface by a method wherein the polycrystalline silicon film, with which the contact part is constituted, is formed in two stages. CONSTITUTION:The resistance of a polycrystalline silicon film 4a is lowered by ion-implanting impurities from above the polycrystalline silicon film 4a which is formed on contact groove parts 10a and 10b and an oxide film 3 in such an extent wherein the thickness of the contact groove part 10a is not increased, and at the same time, the natural oxide film located between impurity diffusion layers 2a and 2b and the film 4a is destroyed. A polycrystalline silicon film 4b is formed again on the film 4a, the resistance-lowered natural oxide film of the film 4b is destroyed in the same manner as above, and finally, polycrystalline silicon films 4c and 4d are formed. Consequently, as the resistance component between a semiconductor substrate 1 and the wiring layer does not become larger because the natural oxide film is completely destroyed, the deterioration of characteristics of the semiconductor element can be prevented even when a narrow-width contact section is formed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing a semiconductor device, and in particular, to a method for manufacturing a semiconductor device, and in particular to a method for manufacturing a semiconductor device, and in particular, a wiring layer for inputting and outputting electrical signals to and from a semiconductor element, and a conductive layer formed on a semiconductor substrate. The present invention relates to a method of manufacturing a semiconductor device having a contact portion for making contact with a region.

[Prior Art] FIGS. 2A to 2C are cross-sectional structural views for explaining a manufacturing process for forming a contact portion of a conventional semiconductor device. First, referring to FIG. 2C, the semiconductor device is
A silicon substrate 1, impurity diffusion layers 2a and 2b formed on the silicon substrate 1, an oxide film 3 formed on the silicon substrate 1, and impurity diffusion layers 2a and 2b of the oxide film 3.
Polycrystalline silicon M14C formed in the opening corresponding to
.

14d, aluminum electrodes 6 formed on polycrystalline silicon films 14c and 14d, and a PSG film 5 that insulates the aluminum electrodes 6 from each other and protects the entire device.

Next, the manufacturing method will be described with reference to FIGS. 2A to 2C. First, impurity diffusion layers 2a and 2b are formed on silicon substrate 1, as shown in FIG. 2A. Thereafter, an oxide film 3 is formed over the entire surface of the element. Resist mask (
(not shown) to form contact grooves 10a and 10b. Next, as shown in FIG. 2B, a polycrystalline silicon film 14 is formed on the oxide film 3 and the contact trenches 10a and 10b. The contact portions 14a and 14b of this polycrystalline silicon film 14 form an impurity diffusion layer 2a.

Electrical contact can be made with 2b. Here, the thickness of the polycrystalline silicon film 14a formed in the contact portion having a narrow contact trench width is greater than the thickness of the polycrystalline silicon film 14b formed in the contact portion having a relatively wide contact trench width. On the other hand, the formed polycrystalline silicon film 14
A natural oxide film is formed by thermal oxidation or the like between the impurity diffusion layers 2a and 2b. Impurity ions are implanted to lower the resistance component of this natural oxide film and to lower the resistance component of the polycrystalline silicon film. Next, as shown in FIG. 2C, the polycrystalline silicon film 14 is patterned to finally form polycrystalline silicon films 14c and 14d. A PSG film 5 is formed on the entire surface and annealed and baked. After that, contacts are formed at predetermined positions, and aluminum electrodes 6 are formed. Conventionally, contact portions of semiconductor devices have been formed in this manner.

FIG. 3 is a schematic diagram for explaining the resistance component of the contact portion 14c having a narrow contact groove width shown in FIG. 2C. Referring to FIG. 3, the resistance at contact portion 14c is:
It is composed of a resistance component R1 of impurity diffusion layer 2a, a contact resistance component R2 at the interface between silicon substrate 1 and polycrystalline silicon 14c, and a resistance component R1 of polycrystalline silicon.

[Problems to be Solved by the Invention] As described above, the resistance of the contact portion is composed of the resistance component R4 of the impurity diffusion layer, the contact resistance component R2 of the silicon/polycrystalline silicon interface, and the resistance component R1 of the polycrystalline silicon. be done. Here, the contact resistance component R2 at the silicon/polycrystalline silicon interface increases due to a natural oxide film generated when forming the contact portion. For this reason, in the past, the natural oxide film generated at the interface between the silicon substrate 1 and the polycrystalline silicon was removed using ion implantation of impurities to lower the resistance of the polycrystalline silicon film. However, as mentioned above, the polycrystalline silicon film is formed thicker in the contact area with a narrow contact groove width than in the contact area with a wider contact groove width, so even if impurity ions are implanted, the native oxide film will be destroyed. The inconvenience of not being able to do so has arisen. In this case, there is a problem that the contact resistance component R2 at the silicon/polycrystalline silicon interface becomes large and the characteristics of the semiconductor element deteriorate.

In other words, in the conventional method, when forming a contact portion with a narrow contact groove width, the natural oxide film that is generated between the silicon substrate and the polycrystalline silicon film is effectively destroyed, and the silicon substrate
It has been difficult to reduce the resistance component between the polycrystalline silicon film and the polycrystalline silicon film. As a result, the resistance value of the entire contact portion increases, which in turn deteriorates the characteristics of the semiconductor element.

The present invention was made in order to solve the above-mentioned problems, and an object of the present invention is to provide a method for manufacturing a semiconductor device in which the characteristics of a semiconductor element do not deteriorate even if a narrow contact portion is formed. shall be.

[Means for Solving the Problems] A method for manufacturing a semiconductor device according to the present invention includes the steps of forming an opening to serve as a contact portion in an insulating film formed on a semiconductor substrate, and forming a first contact portion on the opening and the insulating film. a first wiring layer formed in the opening without passing through the insulating film from above the first wiring layer to below the first wiring layer and a conductive layer formed on the semiconductor substrate. A step of implanting impurities to the extent that it destroys the natural oxide film formed between the regions, a step of forming a second wiring layer on the first wiring layer, and a step of implanting impurities from above the second wiring layer. implanting to destroy a native oxide film formed between the first conductive layer and the second conductive layer.

[Function] In the method for manufacturing a semiconductor device according to the present invention, the first wiring layer is formed over the opening and the insulating film that will become the contact portion, and the opening is formed from above the first wiring layer without passing through the insulating film. Impurity implantation is performed to the extent that it destroys the natural oxide film formed between the first wiring layer formed on the semiconductor substrate and the conductive region on the semiconductor substrate, and then a second wiring layer is implanted on the first wiring layer. is formed, and the natural oxide film formed between the first wiring layer and the second wiring layer into which impurities are implanted from above the second wiring layer is destroyed, thus forming a narrow contact portion. Even if the first wiring layer is formed in the opening, the natural oxide film formed between the first wiring layer and the conductive region on the semiconductor substrate is definitely destroyed, and the resistance component between the semiconductor substrate and the wiring layer becomes large. It never becomes.

[Embodiment of the Invention] FIGS. 1A to 1D are cross-sectional structural diagrams for explaining a manufacturing process of a contact portion of a semiconductor device showing an embodiment of the present invention. First, the configuration of the semiconductor device will be described with reference to FIG. 1D.

The semiconductor device includes a silicon substrate 1, impurity diffusion layers 2a and 2b formed by diffusing impurities on the silicon substrate 1, and an insulating layer formed on the silicon substrate 1 in a region other than a region where a contact portion is formed. oxide film 3 and a polycrystalline silicon film 4c formed on the contact portion on the silicon substrate 1.
, 4d, aluminum electrodes 6 formed on polycrystalline silicon films 4c and 4d, and a PSG film 5 for insulating the aluminum electrodes 6 from each other and protecting the entire device.

Next, the manufacturing process will be described with reference to FIGS. 1A to 1D. First, as shown in FIG. 1A, an impurity diffusion layer 2a is formed on a silicon substrate 1.

2b is formed. Thereafter, an oxide film 3 is formed on the entire surface of the silicon substrate 1. The oxide film 3 is etched to form contact trenches 10a and 10b.

Next, as shown in FIG. 1B, the contact groove IQa,
10b and the oxide film 3, a narrow contact groove 1 is formed on the oxide film 3.
Polycrystalline silicon film 4a is made to such an extent that the thickness of 0a does not become too thick.
form. Impurity ions are implanted from above the polycrystalline silicon film 4a to lower the resistance of the polycrystalline silicon film 4a, and the impurity diffusion layers 2a, 2b and the polycrystalline silicon film 4a are
Destroys the natural oxide film that occurs between the two and lowers the resistance at the interface.

After this, as shown in FIG. 1C, the polycrystalline silicon film 4a
A polycrystalline silicon film 4b is again formed thereon. Impurity ions are implanted from above the polycrystalline silicon film 4b to lower the resistance of the polycrystalline silicon film 4b, and the polycrystalline silicon M
The natural oxide film generated between 4a and 4b is destroyed. Next, as shown in FIG. 1D, polycrystalline silicon films 4a, 4
b is finally patterned to form polycrystalline silicon films 4c, 4.
form d. After this, a PSG film 5 is formed on the entire surface.

The PSG film 5 is annealed and baked.

Thereafter, a contact groove is formed at a predetermined position, and an aluminum electrode 6 is formed.

In this way, in this example, by forming the polycrystalline silicon film that forms the contact portion in two stages,
Even in a contact portion with a narrow contact groove width, the natural oxide film generated between the silicon substrate and the polycrystalline silicon film can be reliably destroyed. As a result, the contact resistance component at the interface between the silicon substrate and the polycrystalline silicon film does not become large. As a result, an increase in the resistance of the entire contact portion, which has been a problem in the past, does not occur. Therefore, the characteristics of the semiconductor element are not deteriorated. In this example, the polycrystalline silicon film is formed in two steps, but the present invention is not limited to this, and may be formed in any number of times as long as it is formed twice or more.

[Effects of the Invention] As described above, according to the present invention, the connection between the first wiring layer formed in the opening and the conductive region on the semiconductor substrate without passing through the insulating film from above the first wiring layer is achieved. By implanting impurities to the extent that it destroys the natural oxide film formed between them, even if a narrow contact portion is formed, the contact between the first wiring layer formed in the opening and the conductive region on the semiconductor substrate is maintained. Since the natural oxide film that forms between the two is reliably destroyed and the resistance component between the semiconductor substrate and the wiring layer does not increase, the characteristics of the semiconductor element will deteriorate even if a narrow contact area is formed. Never.

[Brief explanation of the drawing]

1A to 1D are cross-sectional structural diagrams for explaining the manufacturing process for forming a contact portion of a semiconductor device according to an embodiment of the present invention, and FIGS. 2A to 2C are contacts of a conventional semiconductor device. FIG. 3 is a schematic diagram for explaining the resistance component of the contact portion shown in FIG. 2C. In the figure, 1 is a silicon substrate, 2a is an impurity diffusion layer,
2b is an impurity diffusion layer, 3 is an oxide film, 4a is a polycrystalline silicon film, 4b is a polycrystalline silicon film, 5 is a PSG film, 10a
10b is a contact groove, and 10b is a contact groove. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Scope of Claims] A method for manufacturing a semiconductor device having a contact portion for contacting a wiring layer for inputting and outputting electrical signals to a semiconductor element and a conductive region formed on a semiconductor substrate, the method comprising: a semiconductor device; forming an opening to become the contact portion in an insulating film formed on a substrate; forming a first wiring layer over the opening and the insulating film; and forming a first wiring layer from above the first wiring layer. A natural oxide film is formed between the first wiring layer formed in the opening and the conductive region formed on the semiconductor substrate without passing through the insulating film under the first wiring layer. a step of implanting an impurity to an extent that the wiring layer is destroyed; a step of forming a second wiring layer on the first wiring layer; and a step of implanting an impurity from above the second wiring layer to form a second wiring layer on the first wiring layer. A method for manufacturing a semiconductor device, comprising the step of destroying a natural oxide film formed between the second wiring layer and the second wiring layer.