JP3038961B2 - Method for manufacturing semiconductor device - Google Patents

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 forming a connection portion with a p-type diffusion layer region by selective vapor deposition of tungsten.

[0002]

2. Description of the Related Art A method of burying a tungsten layer by selective vapor deposition in a connection hole opened in a diffusion layer region is disclosed in, for example, Japanese Patent Application Laid-Open No. 63-280442. FIG.
This disclosure will be described with reference to longitudinal sectional views in the order of steps shown in FIG.

[0003] First, an LO is placed on the surface of an n-type silicon substrate 301.
A field oxide film 302 is formed by the COS method, and B ⁺
A p ⁺ -type diffusion layer region 303 is formed by ion implantation of ions. Subsequently, an interlayer insulating film 305 is deposited on the entire surface,
^A connection hole 306 reaching the ⁺ type diffusion layer region 303 is opened [FIG. 3 (a)].

Next, the p ⁺ exposed at the bottom of the connection hole 306 is formed.
B ⁺ ions are again implanted into the mold diffusion layer region 303 (FIG. 3B).

Next, a tungsten layer 308 is buried in the connection hole 306 by a selective vapor deposition method (FIG. 3C).
As a result, an electrical connection is made between the metal wiring (not shown) formed on interlayer insulating film 305 and p ⁺ type diffusion layer region 303.

[0006]

In the conventional method of burying a contact hole with a tungsten layer, the connection to the p ⁺ -type diffusion layer region has a higher contact resistance and varies as compared with the connection to the n ⁺ -type diffusion layer region. Have a point.

[0007] The peculiar instability of the resistance value due to the embedding of the tungsten layer in the contact hole with respect to the p ⁺ type diffusion layer region is caused by the fact that WF _{6 serving as a} source gas in the selective vapor deposition method is used.
It is clear from the results of detailed experiments by the inventor that the present invention is based on the difference in the number of nucleation points in the reaction between the p ⁺ type diffusion layer and the n ⁺ type diffusion layer. Was.

FIG. 4 is a graph showing the difference in the reaction between WF ₆ and the p ⁺ -type diffusion layer and the n ⁺ -type diffusion layer examined by the present inventors. When the substrate temperature is 230 ° C. and the partial pressure of WF ₆ is 0.5 mTorr, the p ⁺ type diffusion layer
And (2/3) ・ WF ₆ + Si → (2/3) ・ W + SiF ₄で between the n ⁺ -type diffusion layer and WF ₆ , which is generated when ₄ is a graph showing the relationship between the amount of SiF ₄ produced and the reaction time.

From these results, it can be seen that p is smaller than that of the n ⁺ type diffusion layer.
^It can be seen that the ⁺ type diffusion layer has a longer time until the reaction of the formula (1) stops. This means that the p ⁺ -type diffusion layer has a smaller number of nucleation of tungsten in the initial stage of film formation than the n ⁺ -type diffusion layer, and the crystal growth based on the contact of crystal grains by nucleation, This indicates that it takes a long time to form a dense film by this.

In general, in the selective vapor deposition of tungsten, a film is formed by H ₂ reduction, SiH ₄ reduction, or the like. Therefore, the reaction between WF ₆ and Si as shown in the equation (1) is very small in the early stage of film formation. Progress only for a short time. Since the nucleation points are small in the p ⁺ type diffusion layer, the effective contact area at the W / Si interface is smaller than that in the n ⁺ type diffusion layer. This causes an increase in contact resistance. Further, when the nucleation point is small and the effective contact area is small, unreacted tungsten fluoride (W
Because it contains the F _X), by passing through the atmosphere and subsequent wet process, the W is oxidized in W / Si interface, the resistance that becomes unstable, revealed from the experiments conducted by the present inventors Was.

[0011]

According to a method of manufacturing a semiconductor device of the present invention, a step of diffusing an impurity containing a Group 3b element into a predetermined region of a semiconductor substrate to form a p-type diffusion layer region; Forming a contact hole reaching the p-type diffusion layer region in the interlayer insulation film by forming an interlayer insulating film in the interlayer insulating film; diffusing an impurity containing a 3b group element into the p-type diffusion layer region exposed at the bottom of the contact hole; A step of diffusing impurities containing Group 5b and 5b elements; and a step of embedding a tungsten layer in the connection holes by selective vapor deposition.

[0012]

Next, the present invention will be described with reference to the drawings. FIG. 1 is a longitudinal sectional view in the order of steps for explaining a first embodiment of the present invention.

First, as shown in FIG. 1A, after a field oxide film 102 is formed on the surface of an n-type silicon substrate 101, a silicon oxide film (about 30 nm thick) is formed on the surface of the n-type silicon substrate 101 by thermal oxidation. (Not shown). BF ₂ ⁺ ions are implanted at an acceleration voltage of 70 keV and a dose of 5 × 10 ¹⁵ cm ⁻² , and heat treatment is performed in a nitrogen atmosphere at 900 ° C. to form a p ⁺ -type diffusion layer region 103. Subsequently, after removing the silicon oxide film described above,
A silicon oxide film 104 having a thickness of about 100 nm and a BPSG film 105 having a thickness of about 1 μm are sequentially deposited on the entire surface by a vapor phase growth method.

Next, as shown in FIG. 1B, after a connection hole 106 is formed by a usual photolithography technique, a silicon oxide film 107 having a thickness of about 30 nm is deposited on the entire surface by a vapor growth method. Subsequently, ion implantation of BF ₂ ⁺ was performed at an acceleration voltage of 70 keV and a dose amount of 5 × 10 ¹⁵ cm ⁻² , and subsequently, an acceleration voltage of 30 keV, 5
Phosphorus ion (P ⁺ ) ion implantation is performed at a dose of × 10 ¹⁴ cm ⁻² . Then, in a nitrogen atmosphere at 900 ° C., 10
A heat treatment is performed for one minute to activate boron and phosphorus. It should be noted that the ion implantation of BF ₂ ⁺ is performed again for n
This is to prevent an increase in the layer resistance of the p ⁺ -type diffusion layer region 103 at the connection hole 106 due to diffusion of the type impurity.

Next, as shown in FIG. 1C, after the silicon oxide film 107 is removed, a tungsten layer 108 is buried in the connection hole 106 by a selective vapor deposition method using SiH ₄ reduction of WF 6. Subsequently, an aluminum film is deposited on the entire surface by a sputtering method, and is patterned by a normal photolithography technique.
09 is formed.

In this embodiment, the tungsten layer 10
The p ⁺ -type diffusion layer region 103 in which 8 grows contains phosphorus (P), and the number of W nucleation points due to the reaction between WF ₆ and Si is larger than that in the normal p ⁺ -type diffusion layer region. To increase. As a result, the effective contact area at the W / Si interface is increased, and the contact resistance is reduced and, at the same time, a stable value with little variation is obtained.

FIG. 2 is a longitudinal sectional view in the order of steps for explaining a second embodiment of the present invention. This embodiment is different from the first embodiment in the method of diffusing impurities into the connection holes.

First, as in the first embodiment, a field oxide film 202 and a BF ₂ ⁺
P of by heat treatment in ion implantation and in a nitrogen atmosphere ⁺
Type diffusion layer region 203 is formed, a silicon oxide film 204 having a thickness of about 100 nm,
An about m BPSG film 205 is sequentially deposited. Subsequently, after forming the connection hole 206, a film thickness of 30 n
An about m silicon oxide film 207 is deposited on the entire surface. Next, as shown in FIG. 2A, an acceleration voltage of 30 keV,
Arsenic ions (As ⁺ ) are implanted at a dose of 1 × 10 ¹⁴ cm ⁻² .

Next, as shown in FIG. 2B, after removing the silicon oxide film 207, the silicon oxide film 207 is heated to 900 ° C. in a hydrogen (H ₂ ) atmosphere of 10 Torr to remove the natural oxide film at the bottom of the connection hole 206. Then, B ₂ H ₆ gas is introduced to thermally diffuse boron at the bottom of the connection hole 206. Arsenic by ion implantation is activated by these thermal processes.

Next, as shown in FIG. 2C, WF ₆ is reduced by SiH ₄ at 250 ° C.
8 is embedded in the connection hole 206. Subsequently, an aluminum film is deposited on the entire surface to a thickness of about 500 nm by a sputtering method, and is patterned by a normal photolithography technique to form an aluminum wiring 209.

In this embodiment, since the group 5b element that diffuses into the connection hole 206 is arsenic, it can be diffused only near the surface. Further, since B ₂ H ₆ is used as a diffusion source of a 3b group element, diffusion and activation and the embedding of the tungsten layer 208 can be performed in the same device, and the boron concentration on the surface can be increased. It has the characteristic. In addition, since the natural oxide film can be removed, more stable contact resistance can be obtained.

[0022]

The present invention described above, according to the present invention is the selective vapor deposition of tungsten on the p ⁺ -type diffusion layer region performs impurity diffusion comprising 5b group element p ⁺ -type diffusion layer region surface, Stable W / S by increasing the number of nucleation of tungsten by Si reduction reaction of WF ₆ gas
An i-interface is formed, so that the contact resistance can be reduced and stabilized.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view in the order of steps for explaining a first embodiment of the present invention.

FIG. 2 is a longitudinal sectional view in the order of steps for explaining a second embodiment of the present invention.

FIG. 3 is a longitudinal sectional view in the order of steps for explaining a conventional method of manufacturing a semiconductor device.

FIG. 4 is a diagram for explaining a problem of a conventional method of manufacturing a semiconductor device, and is a graph showing a change over time of a generation amount of a SiF ₄ gas in a Si reduction reaction of a WF ₆ gas.

[Explanation of symbols]

101, 201, 301 n-type silicon substrate 102, 202, 302 field oxide film 103, 203, 303 p ⁺ -type diffusion layer region 104, 107, 204, 207 silicon oxide film 105, 205 BPSG film 106, 206, 306 connection hole 108,208,308 Tungsten layer 109,209 Aluminum wiring 305 Interlayer insulating film

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-4-67630 (JP, A) Monthly Semiconductor World, Vol. 10, No. 17 (November 20, 1991) p. 214-221 IEICE Technical Report (Technical Report of IEICE) Vo. 91, No. 332 (November 21, 1991) p. 19-24 (SDM91-133) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/28 H01L 21/768

Claims (3)

(57) [Claims] A step of diffusing an impurity containing a group 3b element into a predetermined region of a semiconductor substrate to form a p-type diffusion layer region; and forming an interlayer insulating film on the semiconductor substrate to form a p-type diffusion layer. Forming a connection hole reaching the layer region in the interlayer insulating film; diffusing an impurity containing a group 3b element and an impurity containing a group 5b element into the p-type diffusion layer region exposed at the bottom of the connection hole; A method of manufacturing a semiconductor device, comprising: a step of performing diffusion; and a step of burying a tungsten layer in the connection hole by a selective vapor deposition method. 2. The method according to claim 1, wherein the impurity containing a Group 3b element is boron difluoride ion or diborane. 3. The method according to claim 1, wherein the impurity containing a group 5b element is phosphorus or arsenic.