JPH0590196A - Manufacture of semiconductor device - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a method for manufacturing a semiconductor device having a contact hole with a high aspect ratio, high reliability, and good characteristics. [Structure] A P-type high concentration diffusion layer 13 is formed on a semiconductor silicon substrate 11. Next, the BPSG film 1 which is an interlayer insulating film
2 is formed, and a contact hole 14 is formed in this BPSG film 12. Next, the silicon nitride film 1 is formed on the BPSG film 12.
5 is formed into a film. Then, the silicon nitride film 15 except for the side wall of the contact hole 14 is removed. Next, a polysilicon film 16 is deposited in the contact hole 14, and thereafter,
Doping with ions 17 and heat treatment.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device, and more particularly to a method of manufacturing a semiconductor device having a highly integrated contact hole with a high aspect ratio (depth of contact hole to diameter). ..

[0002]

2. Description of the Related Art Conventionally, there is a contact using buried polysilicon in a semiconductor device having a contact hole having a high aspect ratio, and a manufacturing method thereof will be described with reference to FIG. First, as shown in FIG. 2a, after a diffusion layer 23 having a high impurity concentration is formed on a semiconductor silicon substrate 21, a BPSG film (silicon dioxide containing boron and phosphorus) 22 is used as an interlayer insulating film by a known CVD method. Formed and diffused layer 2
The contact hole 24 is formed on the portion 3 by a well-known fine processing method.
To open.

Next, as shown in FIG.
The polysilicon film 26 is deposited by the D method until the contact hole 24 is sufficiently filled.

Then, as shown in FIG. 2C, the polysilicon film 26 except for the contact holes is removed by using the well-known reactive ion etching method (RIE method).

Thereafter, as shown in FIG. 2d, a diffusion layer 23 is provided to reduce the resistance of the polysilicon burying layer.
Impurities 27 having the same conductivity type as in the above are implanted by a well-known ion implantation method.

Finally, heat treatment is performed to diffuse and activate the impurities in the polysilicon, and then wiring is performed using a known metal film.

[0007]

Conventionally, in a contact hole using buried polysilicon, phosphorus ions diffuse from the BPSG film, which is the sidewall of the contact hole, into the polysilicon film inside the contact hole, so that the P-type diffusion layer is formed. There is a problem that a pn junction is formed in the upper contact, the contact resistance shows non-ohmic property, and the characteristics of the semiconductor device become unstable.

Therefore, an object of the present invention is to provide a method of manufacturing a semiconductor device by a buried polysilicon contact on a P-type diffusion layer having a low resistance and stable characteristics.

[0009]

In order to solve the above-mentioned problems, the present invention provides a semiconductor substrate having a diffusion layer in a method for manufacturing a semiconductor device in which a contact film is filled with polysilicon and then a metal film is formed. A step of forming a contact hole in the interlayer insulating film formed above, a step of forming an impurity diffusion prevention film on the entire surface including the contact hole, and a step of leaving the impurity diffusion prevention film on the side wall of the contact hole. Removing the impurity diffusion prevention film, depositing a polysilicon film in the contact hole to completely fill the contact hole, and implanting the same conductive impurity as the diffusion layer into the polysilicon film. And activating and diffusing the same, the method of manufacturing a semiconductor device.

[0010]

As described above, according to the present invention, by providing the impurity diffusion preventing film, for example, the silicon nitride film on the side wall of the contact hole, the BPSG film outside the side wall is filled with the polysilicon in the subsequent heat treatment step. It is possible to prevent the diffusion of phosphorus ions into the membrane and obtain a good ohmic contact. As a result, the contact resistance can be reduced, and a semiconductor device with stable operation can be obtained.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. FIG. 1 is a cross-sectional view showing the sequence of steps in a method of manufacturing a semiconductor device which is an embodiment of the present invention.

To manufacture a semiconductor device, first, referring to FIG.
As shown in, the P-type high-concentration diffusion layer 13 is formed on the semiconductor silicon substrate 11 by a well-known technique. The surface concentration of this diffusion layer is about 10 ¹⁹ to 10 ²¹ atoms / cm ³ , and the impurity is boron ion.

After that, a BPSG film (silicon dioxide containing boron and phosphorus) 12 which is an interlayer insulating film is formed by a well-known CVD method. The film thickness is 5,000 to 10,000
The concentration of boron and phosphorus contained is about 2 to 10% by weight in the order of angstrom. And
The contact hole 14 is formed by a known fine processing technique.

Next, as shown in FIG. 1b, after forming the contact hole 14, the silicon nitride film 1 is formed by a well-known CVD method.
5 is deposited to a thickness of about 500 to 1,000 angstroms.

Next, as shown in FIG. 1c, well-known directional etching, for example, reactive ion etching (RIE) is performed.
By the method, the silicon nitride film 15 on the portion other than the side wall of the contact hole 14 is removed.

Next, as shown in FIG. 1d, a polysilicon film 16 is deposited using a well-known CVD method until the contact holes 14 are sufficiently filled.

Then, as shown in FIG. 1e, the entire surface is etched by directional etching to remove the polysilicon 16 in the portions other than the contact holes 14. After that, in order to diffuse impurities into the buried polysilicon film 16,
Boron ( ¹¹ B ⁺ ) or boron fluoride ( ⁴⁹ BF ₂ ⁺ ) ions are ion-implanted 17 by a known method.

Finally, the impurities are activated and diffused by a heat treatment at about 800 to 1,000 ° C., a metal film is formed by, for example, a sputtering method, and patterning is performed by a fine processing technique. And a semiconductor device is manufactured.

[0019]

As described above, according to the present invention,
Phosphorus can be prevented from diffusing from the BPSG film which is the interlayer insulating film, and the resistance of the buried polysilicon contact on the P-type diffusion layer can be stabilized and lowered.

By using this technique, it is possible to manufacture a semiconductor device having a highly integrated contact hole with a high aspect ratio, high reliability, and good characteristics.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing a process sequence of a method of manufacturing a semiconductor device according to an embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view showing a process sequence of a method for manufacturing a semiconductor device according to a conventional technique.

[Explanation of symbols]

 11 ... Silicon semiconductor substrate, 12 ... BPSG film, 13 ... Impurity diffusion layer, 14 ... Contact hole, 15 ... Silicon nitride film, 16 ... Polysilicon film, 17 ... Impurity ion implantation, 21 ... Silicon semiconductor substrate, 22 ... BPSG film 23 ... Impurity diffusion layer, 24 ... Contact hole, 26 ... Polysilicon film, 27 ... Impurity ion implantation.

Claims (2)

[Claims] 1. A method of manufacturing a semiconductor device in which a metal film is formed after burying polysilicon in the contact hole, and a step of forming a contact hole in an interlayer insulating film formed on a semiconductor substrate having a diffusion layer, A step of forming an impurity diffusion prevention film on the entire surface including the contact hole; a step of removing the impurity diffusion prevention film leaving the impurity diffusion prevention film on a sidewall portion of the contact hole; The method further comprises: a step of depositing a polysilicon film to completely fill the contact hole; and a step of injecting the same conductivity type impurity as that of the diffusion layer into the polysilicon film to activate and diffuse it. Method of manufacturing semiconductor device. 2. The method for manufacturing a semiconductor device according to claim 1, wherein the impurity diffusion preventing film is made of silicon nitride.