JP2001011631A - Formation of metallic film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for forming a metallic film having low resistivity in a low temp. process by an MOCVD method. SOLUTION: As to this method for forming a metallic film, a wafer provided in a reaction vessel is heated to a prescribed temp., gaseous Ta-contg. organometallic precursory bodies, gaseous ammonia and carrier gas are introduced into the reaction vessel, and the organometallic precursory bodies and ammonia are brought into reaction with each other under prescribed pressure at prescribed temp. to form a film composed of TaNx [(x) is 0.3 to 1.5]. In this case, as the Ta-contg. organometallic precursory bodies, plural precursory bodies composed of a precursory body including a double bond of Ta=N selected from the formulae: RN=Ta(N(R')2)3 and Ta[(N(R")2)]n [R, R' and R" are respectively 1 to 6C alkyl groups, they may be the same or different, and (n) is 4 to 5] and a precursory body which does not include the double bond are used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a metal film, and more particularly, to a method for forming a barrier layer for preventing a reaction between a wiring material and an underlayer and an insulating layer when the wiring material is embedded in a wiring step of a semiconductor device. The present invention relates to a method for forming a metal film to be used.

[0002]

2. Description of the Related Art As one method of forming a TaNx barrier layer, a metal organic chemical vapor deposition (MO) method having a good wiring hole filling property is used.
CVD method). In the formation of the barrier layer by the MOCVD method, the quality of the barrier layer film, in particular, the reduction of its resistivity,
It is important to improve the barrier properties and reduce impurities in the film, and for that purpose, various techniques have been developed.

[0003]

In the conventional MOCVD technique, a high film forming temperature of about 600 ° C. was required to form a TaNx film having a low resistivity (about 1000 μΩ · cm). From a post-process for manufacturing, it is desired to form a TaNx film having a low resistivity by a low-temperature process.

The present invention solves the above-mentioned problems of the conventional barrier layer.
It is an object to provide a method for forming a metal film having a low resistivity by a low-temperature process.

[0005]

Means for Solving the Problems The present inventors have studied the stoichiometric ratio of a TaNx film which is important for reducing the resistivity of a barrier layer.
It has been found that by optimizing (x), and by using a plurality of specific Ta-containing organometallic precursors therefor, it is possible to form a metal film capable of realizing a reduction in resistivity in a low-temperature process. The invention has been completed.

In the method of forming a metal film as a barrier layer according to the present invention, a wafer provided in a reaction vessel, which is a vacuum reaction vessel, is heated to a predetermined temperature, and a gaseous Ta-containing organometallic precursor, ammonia gas and A carrier gas is introduced into the reaction vessel, and the organometallic precursor is reacted with ammonia at a predetermined pressure and temperature, and TaNx (where x is 0.3 to 1.5). A metal film formed on the wafer, comprising: a precursor containing a double bond of Ta and N (Ta = N) as the Ta-containing organometallic precursor; And a plurality of precursors containing no precursor. The composition ratio (x) between Ta and N of the obtained TaNx film can be controlled by changing the ratio (mixing ratio) of these plural precursors to be used.

As the organometallic precursor, the following formula: RN = Ta [N (R ′) ₂ ] ₃ and Ta [N (R ″) ₂ ] _n (where R, R ′ and R '' Indicates C _{1 to} C _6, respectively.
Alkyl groups, which may be the same or different, and n is 4 or 5. )), And a plurality of precursors comprising a precursor containing Ta = N and a precursor not containing Ta = N are used. In the above formula, R, R ′, and R ″ are each selected from a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, or an isomer thereof. , R,
R ′ and R ″ may be the same or different from each other, and include precursors wherein n is 4 or 5. For example, C ₂ H ₅ N = Ta [N (C ₂ H ₅ ) ₂ ] ₃ (light yellow liquid, boiling point: 120 ° C./0.1 Torr), (CH ₃ ) ₃ C
N = Ta [N (C ₂ H ₅ ) ₂ ] ₃ , Ta [N (C ₂ H ₅ ) ₂ ] ₄ (light yellow liquid, boiling point 120 ° C./0.1 Torr), Ta [N (CH
₃ ) ₂ ] ₅ (solid, boiling point 80 ° C./0.1 Torr), Ta [N
It is preferable to use a precursor such as (C ₂ H ₅ ) ₂ ] ₅ . The method of introducing the plurality of organometallic precursors into the reaction vessel is not particularly limited, and, if desired, as a mixture in which the plurality of precursors are premixed, or each of the plurality of precursors individually, or A part of the plurality of precursors may be introduced as a premixed mixture, and the remaining precursors may be individually introduced into the reaction vessel. When the plurality of precursors are individually introduced into the reaction vessel, x of TaNx can be varied by appropriately changing the flow rate ratio.

To control the composition ratio of Ta and N to a desired range, for example, a precursor of the above formula: RN = Ta [N (R ') ₂ ] _{3 and} a precursor of the above formula: Ta [N (R') ') ₂ ] If _{n and n} precursors are introduced into the reaction vessel at a ratio of 1: 1 (volume ratio), x = 0.6 to
A TaNx film of 0.8 can be obtained. The film thus obtained has a resistivity of 2000 to 3000 [mu] [Omega] .cm, and a film which can sufficiently withstand practical use as a barrier layer is obtained.

The reaction between the plurality of organometallic precursors and ammonia is preferably carried out at a temperature of 350 to 450 ° C. and a pressure of 60 to 300 Pa. The method of introducing the organometallic precursor and ammonia gas into the reaction vessel is not particularly limited, and may be performed through a nozzle or through a so-called separate shower plate. Further, the organometallic precursor may be introduced into the reaction vessel by a bubbling method.

Further, as an apparatus used for forming a metal film in the present invention, for example, a known thermal CVD apparatus having a hot plate for heating a wafer can be mentioned.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 schematically shows a side view of a configuration of a thermal CVD apparatus used for forming a metal film serving as a barrier layer. Further, in order to explain the obtained metal film, a cross-sectional view of a substrate in which a TaNx layer is formed in a wiring hole of a semiconductor device is schematically shown in FIG. Example 1 A known single-wafer thermal CVD apparatus having a reaction vessel (vacuum reaction tank) 1 having a hot plate with an electrostatic chuck as shown in FIG. A metal film was formed as a barrier layer.

In the raw material container 2, C ₂ H ₅ N = Ta [N (C ₂ H ₅ ) ₂ ] ₃ and Ta [N (C
₂ H ₅ ) ₂ ] _{4 in} a ratio of 4: 1 (volume ratio). Each of these organometallic precursors is a pale yellow liquid with a boiling point of 120 ° C./0.1.
It is a compound having 1 Torr. The organometallic precursor mixture in the raw material container 2 is led by the pressurized gas a (He) through the liquid mass flow controller 3 to the vaporizer 4 where it is preheated to a temperature of 150 ° C. and then the preheated precursor The mixture is mixed in a vaporizer 4 with one of the carrier gas b (N ₂ ).
After mixing with 000 SCCM, the mixture was introduced into the reaction vessel 1 through a nozzle. The carrier gas b is introduced into the preheater 6 via the mass flow controller 5 and is preheated to 150 ° C. here.
The path between the reactor and the reaction vessel 1 is kept warm by heater H etc.
It can be heated. On the other hand, ammonia gas c
Was introduced into the reaction vessel 1 through the mass flow controller 7 through another nozzle. The substrate 9 placed on the hot plate 8 with an electrostatic chuck is
C., and the pressure in the reaction vessel 1 was maintained at 66.5 Pa for 1 minute to react the precursor mixture with ammonia to form a 50 Å metal film having a TaN _0.8 composition. As shown in FIG. 2, the substrate 9 placed on the hot plate 8 is one in which an insulating layer 10 and a Ti layer 11 are sequentially formed in advance on a Si substrate 9 ′ (or a lower wiring layer). A TaN _0.8 film 1 is formed as a barrier layer on the Ti layer 11 of the substrate 9 by a reaction in the reaction vessel 1.
2 (resistivity: about 3000 μΩ · cm) was formed. The composition of this metal film was identified based on Auger electron spectroscopy (AES).

The obtained metal film is made of an organometallic precursor.
C_TwoH_FiveN = Ta [N (C_TwoH_Five)_Two]_ThreeAnd Ta [N (C_TwoH_Five)_Two]_FourWhen
, Ie, (C_TwoH_FiveN = Ta [N (C_TwoH_Five)_Two]_Three)
/ (C _TwoH_FiveN = Ta [N (C_TwoH_Five)_Two]_Three+ Ta [N (C
_TwoH_Five)_Two]_Four)) (Volume ratio) (mixing ratio 0 to 0)
1.0), the value of x of the TaNx film for this mixture ratio and the resistance
The relationship with the resistivity (μΩ · cm) was measured, and the results were shown in FIG.
Shown in As is clear from FIG.
8, that is, when x = 0.7 to 0.9, the resistivity is 2
The value was as low as 000 to 4000 μΩ · cm.

A similar metal film was obtained when the two kinds of organometallic precursors were separately introduced into the reaction vessel using different introduction systems.

[0015]

As described above, according to the present invention, T
By reacting a plurality of precursors comprising a Ta-containing organometallic precursor having an a = N double bond and a Ta-containing organometallic precursor having no double bond with ammonia, a TaNx film as a barrier layer is formed. Since the precursors are formed, the reactivities of the respective precursors and ammonia are different, so that TaNx films having different stoichiometric ratios can be formed. Therefore, by changing the ratio of a plurality of precursors to be used, x of TaNx can be changed, and the obtained TaNx can be changed.
The specific resistance of the x film can be reduced.

[Brief description of the drawings]

FIG. 1 is a side view schematically showing a configuration of a thermal CVD apparatus used in the present invention.

FIG. 2 is a cross-sectional view schematically illustrating a substrate in which a TaNx film as a barrier layer is formed on a substrate having a wiring hole according to the first embodiment of the present invention.

FIG. 3 is a graph showing a relationship between x and a resistivity with respect to a mixing ratio of a precursor.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Reaction container 2 Material container 3 Liquid mass flow controller 4 Vaporizer 5 Mass flow controller 6 Preheater 7 Mass flow controller 8 Hot plate with electrostatic chuck 9 Substrate 9'Si substrate or lower wiring layer 10 Insulating layer 11 Ti layer 12 Barrier layer (TaNx) Film) a Pressurized gas b Carrier gas c Ammonia gas H Heater

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takashi Komatsu 523 Yokota, Yamatake-cho, Yamatake-gun, Chiba Japan Nippon Vacuum Engineering Co., Ltd. Inside Chiba Super Materials Laboratory, Technology Co., Ltd. (72) Inventor Yasuhiro Taga 523 Yokota, Yamatake-cho, Sanmu-gun, Chiba Prefecture Japan Vacuum Technology Co., Ltd. Chiba Super Materials Lab. BB32 DD45 FF16

Claims (4)

[Claims] 1. A wafer provided in a reaction vessel is heated,
A gaseous Ta-containing organometallic precursor, an ammonia gas and a carrier gas are introduced into a reaction vessel, and at a predetermined pressure and temperature, the organometallic precursor is reacted with ammonia;
TaNx (where x is 0.3 to 1.5)
A metal film formed on the wafer, the Ta-containing organometallic precursor comprising: a precursor containing a double bond of Ta and N (Ta = N); A method for forming a metal film, comprising a plurality of precursors comprising: 2. The Ta-containing organometallic precursor has the following formula: RN = Ta (N (R ′) ₂ ) ₃ and Ta (N (R ″) ₂ ) _n (where R, R 'And R''are C _{1 to} C _6, respectively.
Alkyl groups, which may be the same or different, and n is 4 or 5. 2) a plurality of precursors comprising a precursor containing Ta = N and a precursor not containing Ta = N selected from the group consisting of:
The method for forming a metal film according to the above. 3. The plurality of Ta-containing organometallic precursors,
The method for forming a metal film according to claim 1, wherein the mixture is introduced into the reaction vessel as a pre-mixed mixture, individually, or partially as a pre-mixed mixture, and the remainder individually. 4. The ratio of the precursor containing Ta = N is 20
The method for forming a metal film according to any one of claims 1 to 3, wherein the content is from 80% to 80%.