JPH0629236A - Method for manufacturing semiconductor device - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] To provide a method for forming a metal thin film for forming a wiring, which has good surface morphology and good coverage, particularly a contact hole of a CVD-W thin film. [Structure] On the interlayer insulating film 2 formed on the Si substrate 1,
The barrier metal 3 is formed on the entire inner wall and bottom of the contact hole opened at a predetermined position of the interlayer insulating film 2, and the surface reaction rate-determining first surface is formed on the entire surface of the barrier metal 3.
The reduction reaction and the second reduction reaction, which is the rate-determining supply reaction, are alternately repeated in this order and performed multiple times. The first reduction reaction has good coverage but poor surface morphology.
The W film A ₁ to A ₄ was formed as a _second reducing, the flow ratio of H ₂ / WF ₆ so that the surface reaction rate is set to 10 or less. The second reduction reaction has poor coverage but forms W films B _{1 to} B ₄ as SiH ₄ reduction having good surface morphology.

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 in which a metal thin film is formed in a contact hole of a semiconductor device by a chemical vapor deposition (hereinafter abbreviated as CVD) method.

[0002]

2. Description of the Related Art FIGS. 5A to 5C are cross-sectional views of a contact portion of a semiconductor device having a W film formed by a conventional blanket W-CVD method. In FIGS. 5A to 5C, W films 4, 5 and 6 are formed on the entire surface of the barrier metal 3. An interlayer insulating film 2 is formed on the Si substrate 1, and a contact hole 2a is opened at a predetermined position of the interlayer insulating film 2.

A method of forming these conventional W films 4, 5 and 6 will be described below with reference to FIGS. First, the case of FIG. 5A will be described below. As shown in FIG. 5A, the barrier metal 3 also serving as an adhesion layer, such as TiN, is formed on the entire inner wall and bottom of the contact hole 2a formed in the interlayer insulating film 2 on the Si substrate 1.
/ Ti, TiW, W, WSi _2, etc. are formed. Then, a W film 4 is formed thereon by a blanket W-CVD method using a reduction reaction of WF ₆ and H ₂ so as to fill the contact hole 2a.

Typical film forming conditions at this time are shown in Table 1 (a).
The sequence of the introduced gas, pressure, and film forming temperature at that time is shown in FIG.

[0005]

[Table 1]

In this reaction system, by adjusting the flow rate ratio of H ₂ / WF ₆ to 6 and the pressure to 80 torr,
Coverage ((ta ₁ / ta ₂ ) × 10)
0%) is very good. But in this condition,
As shown in FIG. 5A, the surface morphology of the W film 4 becomes extremely poor.

Next, in the case shown in FIG.
After forming Tal 3, WF₆ And H ₂ Using the reduction reaction of
Contact the W film 5 by blanket W-CVD method
The film is formed so as to fill the hole 2a. At this time
Typical film forming conditions are shown in (b) of Table 1, and the introduction at that time
The sequence of gas, pressure, and film formation temperature is shown in Fig. 7.
You In this reaction system, H₂ / WF₆ About the flow rate of
Supply by adjusting 50 and pressure to 80 torr
The reaction is rate-determined, and as shown in FIG.
I'm trying to improve the logic. But in this condition W
Membrane 5 coverage ((tb₁/ Tb₂) × 100%) is bad
Become.

Finally, in the case shown in FIG. 5C, after forming the barrier metal 3, the W film 6 is formed in the contact hole 2a by the blanket W-CVD method using the reduction reaction of WF ₆ and SiH _4. The film is formed so as to be embedded. Typical film forming conditions at this time are shown in (c) of Table 1, and the sequence of introduced gas, pressure, and film forming temperature at that time is shown in FIG. In this reaction system, the flow rate ratio of SiH ₄ / WF ₆ is adjusted to about 50 and the pressure is adjusted to 80 to control the rate of the supply reaction so that the surface morphology is improved as shown in FIG. 5 (c). ing. However, in this condition W
The coverage of the membrane 6 ((tc ₁ / tc ₂ ) × 100%) becomes worse.

The coverage (ta ₁
/ Ta ₂ , tb ₁ / tb ₂ , tc ₁ / tc ₂ ) and the difference in surface morphology (surface roughness) are described in JEJ Schm.
idtz, RCEllwanger, and AJM / van Dijk, Tungsten a
nd other Refractory Metalsfor VLSI applications
(III), 1988, pp55-61, Thomas E. Clark et.al., solid
state technology (Japanese version) December 1989, pp33 ~
41, and Albert Hasper, et.al., Tungsten and other
Advanced Metals for ULSI applications 1990,1990, pp
See 317-325.

Further, as a method for improving the surface roughness of a W film by H ₂ reduction, a document Albert Hasper, et.al., Tungsten an.
d other Advanced Metals for ULSI applications 199
0,1990, pp317-325, a method of eliminating surface irregularities by introducing a nucleation step of SiH ₄ into H ₂ reduction is described. The gas sequence at this time is shown in FIG. According to this, after H ₂ reduction, the supply of WF ₆ is stopped, SiH ₄ is caused to flow to dissociate on the W surface, a Si layer of about 2 nm is formed on the surface, then SiH ₄ is stopped, and then WF ₆ is supplied again. Then, the Si layer is subjected to Si reduction and used as the nucleus of the H ₂ reduction reaction, so that the grain growth is once stopped, and the grain is grown again based on the reformed nucleus to reduce the grain size. As a result, the unevenness of the W film surface is reduced.

[0011]

By the way, as the degree of integration and miniaturization of semiconductor devices progresses, it becomes necessary to form a fine pattern of wiring, particularly a fine pattern by photolithography. At this time, if irregular reflection occurs, wiring disconnection, patterning failure, misalignment, etc. occur. Therefore, in order to obtain a good fine pattern, the surface morphology of the wiring forming metal thin film must be improved.

Further, since the diameter of the contact hole is becoming finer and the aspect ratio is being made higher, it is necessary to improve the coverage of the contact electrode having the high aspect ratio.

Therefore, the surface morphology is good and the cover is
A metal thin film for wiring formation with good rage is required.
Above all, the blanket W-CVD wiring formation technology
This is the most promising technology. However, as shown in the above conventional example
The surface reaction rate-determining H, which is a film with good coverage,₂ Return
The original W film 4 has a very bad surface morphology and
Supply reaction-controlled H with good surface morphology₂ By reduction
W film 5 and SiH _Four Covered with W film 6 by reduction
There was the problem that Ji was bad.

In addition, SiH ₄ is added to the H ₂ reduction shown in the conventional example.
In the method of including the step of re-nucleation by the method, the formation of the Si layer saturates at about 2 nm. Therefore, the W film formed by the Si reduction of the Si layer has a sufficient amount to sufficiently reduce the unevenness of the surface. The film thickness cannot be obtained.

The present invention solves the above problems, and an object of the present invention is to provide a method for forming a metal thin film for forming a wiring, which has good surface morphology and good coverage, particularly a contact hole of a CVD-W thin film.

[0016]

In order to solve the above problems, the present invention is directed to an interlayer insulating film formed on a semiconductor substrate, an inner wall of a contact hole opened at a predetermined position of the interlayer insulating film, and Barrier metal is formed on the entire bottom surface,
A W film is formed on the entire surface of the barrier metal by the chemical vapor deposition method. When the W film is formed by the chemical vapor deposition method, the surface reaction rate-determining first reduction reaction and the supply reaction rate-determining second reduction reaction are performed. The reaction and the reaction are alternately performed plural times in this order.

The first reduction reaction is a reduction reaction of WF ₆ and H _2, and the gas flow rate ratio of H ₂ to WF ₆ is 10 or less in order to limit the rate of surface reaction. The film is manufactured on a flat surface to a thickness of 200 nm or less, and the second reduction reaction is a reduction reaction of WF ₆ and SiH ₄ .
The W film formed at one time is manufactured with a thickness of 5 nm or more and 50 nm or less on a flat surface.

Alternatively, the first reduction reaction is performed by using WF ₆ and H.
WF ₆ for reducing reaction with ₂ and controlling the surface reaction
And the gas flow rate ratio of H ₂ to 10 is less than or equal to 10 and the W film formed at one time has a thickness of 200 nm or less on a flat surface, and the second reduction reaction is a reduction reaction between WF ₆ and H _2. ,
WF gas flow ratio of H ₂ to the feed reaction rate as 10 or more for _6, is intended to produce in the formed W film 5nm or 50nm or less thick on flatness once.

[0019]

In the above structure, WF is used as the first reduction reaction.
_Two W films are formed at one time by the reduction reaction of WF ₆ and H ₂ whose surface reaction rate is controlled so that the gas flow rate ratio of H _{2 to 6} is 10 or less.
By forming a film with a thickness of 00 nm or less, a W film with good coverage can be formed, and since the film thickness is thin, the unevenness on the surface can be made relatively small, though not enough.
After that, as a second reduction reaction, a W film having a poor coverage but a good surface morphology is formed by a feed reaction rate-limiting reduction reaction of WF ₆ and SiH ₄ at a thickness of 5 nm or more and 50 nm or less at a time. The unevenness on the surface of the W film formed by the first reduction reaction can be reduced and the surface morphology can be kept good. Therefore, by alternately repeating the first reduction reaction and the second reduction reaction a plurality of times, W having good coverage and good surface morphology can be obtained.
A film can be formed.

Further, as the first reduction reaction, the surface reaction rate-determining WF in which the gas flow rate ratio of H _{2 to} WF ₆ is 10 or less.
By forming a W film with a reduction reaction of ₆ and H ₂ with a thickness of 200 nm or less at a time, a W film with good coverage can be formed, and since the film thickness is thin, unevenness on the surface is not sufficient. No, but can be made relatively small. After that, as a _second reduction reaction, a W film produced by the reduction reaction of WF ₆ and H _{2 which} has a poor coverage but a good surface morphology and has a supply reaction rate, and a gas flow rate ratio of H _{2 to} WF ₆ of 10 nm or more and 5 nm or more. By forming the film with a thickness of 50 nm or less, the unevenness of the W film surface formed by the first reduction reaction can be reduced and the surface morphology can be kept good. Therefore, by alternately repeating the first reduction reaction and the second reduction reaction a plurality of times in this order, a W film having good coverage and surface morphology can be formed, and Si is not mixed in the film. A W film having a low specific resistance can be formed.

[0021]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a sectional view of a contact hole portion in a first embodiment of the present invention, FIG. 2 shows a sequence of introduced gas, pressure and film forming temperature at the time of forming a W film in the present invention, and Table 2 shows The film forming conditions are shown. In FIG. 1, those having the same functions as those of the conventional one ((a) to (c) of FIG. 5) are designated by the same reference numerals, and the description thereof is omitted.

[0022]

[Table 2]

As shown in FIG.
First of all, the coverage is good, but the surface morphology is bad.
WF with high surface reaction rate control₆ And H₂ W by reduction reaction with
Membrane A ₁ Film, then the surface coverage
WF with a good supply reaction rate control₆ And SiH_Four Return of
W film B by original reaction₁ Film, and the order and
And a plurality of times under different conditions (three times more in this embodiment),
W film A₂ ~ A_Four And W film B₂ ~ B_Four And are deposited.

Here, W by the surface reaction-controlled H ₂ reduction is applied.
As shown in FIG. 2 and Table 2, the manufacturing conditions of the membranes A _{1 to} A ₄ (hereinafter, abbreviated as A _1-4 ) are: H ₂ / WF ₆ flow rate ratio of 900 / 75 = 6 and 10
It is set below.

Further, the surface irregularities are made thicker.
The surface reaction rate-determining H₂ By reduction
W film A_1-4 The thickness of each is less than 200 nm
Make sure that the unevenness of the
Feed rate-controlled SiH with poor surface roughness and small surface irregularities
_Four W film by reduction B₁ ~ B_Four (Hereinafter, B_1-4 Abbreviated)
Deposit a film with a thickness of 5 nm or more and 50 nm or less
₂ W film by reduction A_{1- Four} The surface morphology of
A sufficient film thickness to be deposited. At this time, SiH _Four To give back
According W film B_1-4 If the film thickness of is too thick, the W film A
_1-4 , B_1-4 The coverage in the entire contact hole 2a
Since it becomes worse, the film thickness should be as thin as possible. Implementation
In the example, W film A_1-4 Thickness of 80 nm, W film B
_1-4 Has a thickness of 15 nm.

FIG. 3 shows a sectional view of a contact hole portion in the second embodiment of the present invention, and FIG. 4 shows W in the present invention.
The sequence of introduced gas, pressure, and film formation temperature during film formation is shown, and Table 3 shows film formation conditions.

[0027]

[Table 3]

As shown in FIG.
First of all, the coverage is good, but the surface morphology is bad.
WF with high surface reaction rate control₆ And H₂ W by reduction reaction with
Membrane C ₁ Film, then the surface coverage
WF with a good supply reaction rate control₆ And H₂ Reduction anti-
W film D₁ And then this sequence and
Alternately multiple times (3 more times in this example), W film
C₂ ~ C_Four And W film D₂~ D_Four And are deposited.

In this case, as shown in FIG. 4, the W film C₁ 
~ C_Four (Hereafter, C_1-4 Abbreviated), D ₁ ~ D_Four (Hereafter, D
_1-4 (Abbreviated as) W film forming condition is H₂ / WF₆ The flow rate of
W film C just by changing_1-4 Then the surface reaction becomes rate-determining
It is set to 6 below 10 and W film D_1-4 Then supply
It is set to about 60 (10 or more) so that the reaction is rate-controlled.
It

Here, since the surface irregularities increase as the film thickness increases, the W films C _1-4 each have a thickness of 200 nm or less so that the surface irregularities do not become too large, and then the coverage is poor. The W film D _1-4 having small surface irregularities is deposited to a thickness of 5 nm or more and 50 nm or less, and a film thickness sufficient to improve the surface morphology. At this time, when increasing the thickness of the W film D _1-4, W film C _1-4, for D _1-4 coverage in the entire contact hole 2a is deteriorated, the thickness of the W film D _1-4 is It is better to make it as thin as possible. In this embodiment, the thickness of the W film C _1-4 is 80
nm, the thickness of the W film D _1-4 is set at 15 nm.

Further, in this embodiment, unlike the first embodiment, SiH ₄ reduction is not used, so that the W films C _1-4 and D _{1-4 are used.}
There is an advantage that Si is not mixed in and the specific resistance of the W films C _1-4 and D _1-4 can be lowered.

[0032]

As described above, according to the present invention,
On the interlayer insulating film formed on the conductive substrate, and the interlayer
The inner wall of the contact hole opened at a predetermined position in the insulating film
And a barrier metal is formed on the entire bottom surface.
A W film is formed on the entire surface of the wafer by chemical vapor deposition.
When forming the W film by chemical vapor deposition, WF₆ And H
₂ The first reduction reaction with and WF₆ And SiH_Four Second reduction with
The reaction and the first reaction
WF is WF₆ Against H₂ Gas flow ratio of 10 or less
As a result, the surface reaction rate-determining WF has good coverage.
₆ And H₂ W film is formed by the reduction reaction of and is formed once.
The thickness of the W film is 200 nm or less on a flat surface.
The second reduction reaction is a feed reaction rate-determining surface morphology.
Good WF₆ And SiH_Four Film is formed by the reduction reaction of
However, the thickness of the W film formed at one time is 5 nm or more on a flat surface 5
By setting it to 0 nm or less, the coverage is good and the surface
A W film with good morphology can be formed, and this result
As a result, fine patterns can be formed and high asperity can be achieved.
It is possible to fill the contact hole in the contact ratio.

Interlayer insulation formed on the semiconductor substrate
Burrs on the film and on the entire inner wall and bottom of the contact hole
A metal is formed and chemical vapor is formed on the entire surface of this barrier metal.
A W film is formed by the phase growth method, and the chemical vapor deposition of the W film is performed.
When forming by the method, WF ₆ And H₂ The first reduction reaction of
WF₆ And H₂ 2nd reduction reaction of
And the first reduction reaction is WF₆ Against H₂ The gas
A table with good coverage by setting the flow rate ratio to 10 or less
Surface reaction rate-controlled H₂ Form a W film by reduction and form it in one step
The thickness of the W film is 200 nm or less on a flat surface, and
The second reaction is WF₆ Against H₂ Gas flow ratio of 10 or more
As a top, the supply reaction-controlled H with good surface morphology₂ Return
An original W film is formed, and the thickness of the W film formed at one time is flat.
By setting it to 5 nm or more and 50 nm or less on the carrier, the cover
The rage and surface morphology can be improved,
Enables formation of fine patterns and high aspect ratio
The specific contact hole can be filled. Furthermore, this
According to the manufacturing method, the ratio that Si is not mixed in the W film
A W film having low resistance can be formed.

[Brief description of drawings]

FIG. 1 is a sectional view of a contact portion of a semiconductor device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a sequence of gas, pressure, and film forming temperature at the time of forming a W film in the first example of the present invention.

FIG. 3 is a sectional view of a contact portion of a semiconductor device according to a second embodiment of the present invention.

FIG. 4 is a diagram showing a sequence of gas, pressure, and film forming temperature at the time of forming a W film in the second example of the present invention.

FIG. 5 is a cross-sectional view of a contact portion of a semiconductor device when a conventional method is used, (a) is a cross-sectional view of the contact portion of the semiconductor device when a W film is formed by surface reaction rate-determining H ₂ reduction, (B) is a cross-sectional view of a contact portion of a semiconductor device when a W film is formed by H ₂ reduction that is rate-controlled by a supply reaction,
(C) is a sectional view of a contact portion of a semiconductor device when a W film is formed by SiH ₄ reduction.

FIG. 6 is a diagram showing a sequence of gas, pressure, and film formation temperature when a W film is formed by surface reaction-controlled H ₂ reduction in a conventional method.

FIG. 7 is a diagram showing a sequence of gas, pressure, and film forming temperature in the case where a W film is formed by H ₂ reduction of a supply reaction rate in a conventional method.

FIG. 8 is a diagram showing a sequence of gas, pressure, and film forming temperature when a W film is formed by SiH ₄ reduction in the conventional method.

FIG. 9 is a gas used when a W film is formed by a method including a conventional H ₂ reduction and a step of re-nucleating SiH ₄ .
It is a figure showing a sequence of pressure and film formation temperature.

[Explanation of symbols]

1 Si substrate (semiconductor substrate) 2 Interlayer insulating film 3 Barrier metal A _{1 to} A ₄ surface W film by reaction-controlled H ₂ reduction B _{1 to} B ₄ supply reaction-controlled W film by SiH ₄ reduction C _{1 to} C ₄ surface W film by reaction-controlled H ₂ reduction D _{1 to} D ₄ supply W film by reaction-controlled H ₂ reduction

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Shuji Hirao 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Yuka Terai, 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd.

Claims (7)

[Claims] 1. A barrier metal is formed on an interlayer insulating film formed on a semiconductor substrate and on an inner wall and a whole bottom surface of a contact hole opened at a predetermined position of the interlayer insulating film,
A method of manufacturing a semiconductor device in which a W film is formed on the entire surface of a barrier metal by a chemical vapor deposition method, wherein when forming a W film by the chemical vapor deposition method, a first reduction reaction, which is a surface reaction rate control, and a supply are supplied. A method for manufacturing a semiconductor device, wherein a second reduction reaction, which is a reaction rate limiting method, is alternately performed a plurality of times in this order. 2. The method for manufacturing a semiconductor device according to claim 1, wherein the first reduction reaction is a reduction reaction between WF ₆ and H _2, and the second reduction reaction is a reduction reaction between WF ₆ and SiH ₄ . 3. The method of manufacturing a semiconductor device according to claim 2, wherein the flow rate ratio of H _{2 to} WF ₆ is 10 or less in the first reduction reaction. 4. The method of manufacturing a semiconductor device according to claim 1, wherein the first reduction reaction is a reduction reaction between WF ₆ and H _2, and the second reduction reaction is a reduction reaction between WF ₆ and H ₂ . 5. The first reduction reaction flow ratio of H ₂ to WF ₆ is 10 or less, the second reduction reaction semiconductor device according to claim 4, wherein the gas flow ratio of H ₂ to WF ₆ is 10 or more Manufacturing method. 6. The W film formed once in the first reduction reaction
The method of manufacturing a semiconductor device according to claim 1, wherein the thickness of the film is 200 nm or less on a flat surface. 7. The W film formed once in the second reduction reaction
The method of manufacturing a semiconductor device according to claim 1, wherein the film thickness is 5 nm or more and 50 nm or less on a flat surface.