JP2001131746A - Tantalum-carbon-base thin film and method for depositing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a barrier layer of relatively low specific resistance and a method for depositing this barrier layer at a low temperature. SOLUTION: The layer which is deposited on a substrate by pyrolyzing a tantalum-containing organic metallic compound by a chemical vapor deposition method and contains much carbon is exposed to a plasma while the substrate is biased, by which the tantalum-carbon-base thin film of the low specific resistance useful as the barrier layer is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a barrier layer for preventing a reaction between a wiring material and an underlayer and an insulating layer in a wiring step of a semiconductor device, and a method for forming the same. The present invention relates to a forming method.

[0002]

2. Description of the Related Art As a method for producing a barrier layer for wiring, a chemical vapor deposition method using an organometallic compound has been conventionally known. When forming a barrier layer by this chemical vapor deposition method,
It is important to lower the specific resistance (resistivity) of the obtained layer and improve the barrier properties. For example, when forming a tantalum-nitrogen (TaN) layer at about 400 ° C. by a chemical vapor deposition method, the specific resistance of the obtained layer is several thousand μΩ · cm.
This value is higher than the actually required value of several hundred μΩ · cm. Therefore, at present, a barrier layer having a low specific resistance (for example, about 1000 μΩ · cm) is obtained at a high temperature of about 600 ° C.

Assuming that the bulk layer has a low specific resistance, a TaN thin film (about 200 μΩ ·
cm), tantalum-carbon (TaC) thin film (about 30 μΩ)
Cm) is known. However, when a barrier layer is formed by a chemical vapor deposition method, as described above, a barrier layer having a certain low resistivity is known for a TaN thin film, but a low resistivity barrier layer is known for a TaC thin film. Layers have not yet been developed.

[0004]

In the conventional chemical vapor deposition method, as described above, a barrier layer (for example, a TaN layer) having a low resistivity is formed by forming a film at a high temperature. This causes a defect in a subsequent semiconductor device manufacturing process. Therefore, it is desired to form a barrier layer having a low specific resistance at a low temperature.

The present invention has been made to solve the above problems, and provides a method of forming a tantalum-carbon thin film at a low temperature as a low resistivity barrier layer, and an obtained low resistivity film. Make it an issue.

[0006]

Means for Solving the Problems The present inventors can form a barrier layer having a low specific resistance by a chemical vapor deposition method by using a TaC thin film having a low specific resistance in a bulk layer. As a result of various studies, the present inventors have completed the present invention.

The method for forming a tantalum-carbon thin film according to the present invention comprises the steps of: thermally decomposing a tantalum-containing organometallic compound by chemical vapor deposition to deposit a carbon-rich layer deposited on a substrate;
By exposing the substrate to plasma while applying a bias, a low resistivity tantalum-carbon based thin film useful as a barrier layer is obtained. Further, the tantalum of the present invention
The carbon-based thin film is formed as described above and has a specific resistance of 350 to 2000 μΩ · cm.

[0008] The depositing step comprises the steps of:
Preferably, it is performed at 00 ° C. Substrate temperature is 250 ℃
If it is lower than this, it is difficult to obtain a thin film having a low specific resistance and the film forming rate is low, so that it is not practical. If it exceeds 400 ° C., a defect occurs in a subsequent device manufacturing process.

The tantalum-containing organometallic compound is represented by the following formula: RN = Ta [N (R ′) ₂ ] ₃ and Ta [N (R ″) ₂ ] _n (where R, R ′, And R ″ are each C ₁ -C
₆ alkyl groups, which may be the same or different from each other, and n is 4 or 5. ), An alkyl-substituted amino tantalum compound selected from the group consisting of: C ₁ -C ₆ alkyl groups include methyl, ethyl, propyl, butyl, pentyl, hexyl,
Or their isomers. For example, C ₂ H ₅ N = T
a [N (C ₂ H ₅ ) ₂ ] ₃ (light yellow liquid, boiling point 120 ° C./0.1
Torr), (CH ₃ ) ₃ CN = 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 T
orr), Ta [N (CH ₃ ) ₂ ] ₅ (solid, boiling point 80 ° C. /
0.1 Torr) or an alkyl-substituted amino tantalum compound such as Ta [N (C ₂ H ₅ ) ₂ ] ₅ . These are organic metal compounds that do not contain oxygen, are relatively stable, and are easily available.

It is preferable that the deposition step and the subsequent plasma exposure step be performed without removing the substrate from the vacuum environment. In particular, it is preferable that the deposition step and the plasma exposure step be performed in one vacuum processing chamber. This is to prevent the oxidation of the thin film and increase the work efficiency. The plasma preferably contains at least one of nitrogen ions, nitrogen-containing ions, argon ions, krypton ions, and xenon ions, and the nitrogen-based gas already contained in the film or an inert gas as described above. By using, side reactions can be prevented. Further, the deposition step and the plasma exposure step are
This is preferably repeated a plurality of times as a cycle. As a result, the obtained thin film is densified, so that the specific resistance is easily reduced, and a barrier layer having a desired film thickness can be obtained.

After the deposition step and the plasma exposure step are completed, the obtained tantalum-carbon thin film may be thermally annealed in a silane-based gas atmosphere.
Thereby, the barrier property of the side wall such as the wiring hole where the plasma exposure treatment is insufficient due to the straightness of the particles can be improved.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. 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 tantalum-carbon thin film was formed as a barrier layer.

Tantalum-containing organic metallization in raw material container 2
As a compound, C_TwoH_FiveN = Ta [N (C _TwoH_Five)_Two]_ThreeAnd put
Mass flow of the compound of formula
After passing through the controller (MFC) 3 to the vaporizer 4,
This was preheated to a temperature of 150 ° C. Preheated
10SCCM of compound-containing gas as carrier gas in vaporizer 4
b (N_Two) After mixing with 1000 SCCM, the mixture is
Through a nozzle in the reaction vessel 1 (with a shower head
If you do, introduce it through the showerhead)
A layer rich in carbon is deposited on the substrate 5 for 2 minutes,
An Angstrom thick film was formed. This process
Medium, the substrate 5 placed on the hot plate 6 is heated to 400 ° C.
And the pressure in the reaction vessel 1 is maintained at 66.5 Pa.
Was. This carrier gas b is a mass flow controller
-7 and introduced into the heat exchanger 8 where it is brought to 150 ° C
After being preheated, it was introduced into the vaporizer 4. Also vaporization
The path between the vessel 4 and the container 1 is such as a heater H or a heating medium.
Heating and heating can be performed by heating means. This
And the composition ratio of tantalum and carbon on the substrate 5
Is approximately 1: 1 and the layer containing more carbon than nitrogen
Stacked. The specific resistance of the obtained layer is high, several thousand μΩ · c
m.

Next, the plasma forming gas c (Ar) is passed through the mass flow controller 9 at a flow rate of 100 SCCM.
With the inside of the reaction vessel kept at 13.3 Pa, RF power of 500 W was applied to the substrate 5 from the RF source 10 for 30 seconds,
Exposure to plasma with argon, ie, plasma annealing, was performed for 30 seconds to obtain a tantalum-carbon thin film of about 50 Å.

The above-described deposition step and plasma annealing step were defined as one cycle, and this cycle was repeated four times, and the desired tantalum-carbon thin film was laminated on the substrate 5. The thickness of the obtained thin film was about 200 Å, and its specific resistance was 370 μΩ · cm.

In the above operation, the substrate 5 placed on the hot plate 6 is placed on a Si substrate (or a lower wiring layer).
An insulating layer or the like is formed in advance. As shown in FIG. 2, a carbon-rich layer 23 deposited by thermal decomposition of a tantalum-containing organometallic compound is formed on an insulating layer 22 provided on a substrate 21 as described above, Tantalum-
A carbon-based thin film was formed.

When the same operation as above was repeated using nitrogen instead of argon as the plasma forming gas, similar results were obtained.

Table 1 below shows the composition change and the specific resistance change in the thin film before and after the plasma annealing performed as described above. The composition of this thin film was identified based on Auger electron spectroscopy (AES). (Table 1)

As is clear from Table 1, the composition ratio of tantalum and carbon in the obtained tantalum-carbon thin film is almost 1: 1 in both the plasma annealing using argon and the plasma annealing using nitrogen. There was almost no change before and after the plasma annealing treatment, and the specific resistance of the obtained thin film was one digit lower than that before the annealing. In addition, the carbon content is higher than the nitrogen content before and after the treatment without releasing carbon atoms by the plasma annealing treatment. For this reason, the obtained thin film was used as a tantalum-carbon thin film. (Example 2) The method described in Example 1 was repeated. However,
The plasma annealing time was changed to 0, 15, 30, and 60 seconds, and a tantalum-carbon based thin film was formed by only one cycle of the deposition step and the plasma annealing step, and the specific resistance was measured. The relationship between the annealing time and the specific resistance was examined. Table 2 shows the results. (Table 2)

As apparent from Table 2, the annealing time 3
Saturation was achieved in 0 seconds, and a thin film with low specific resistance was obtained. (Embodiment 3) In Embodiment 1, a deposition step and a plasma annealing step are alternately performed in the same reaction vessel to produce a tantalum-carbon thin film, but in this embodiment, the deposition step and the plasma annealing step are performed. Performed alternately in separate reaction vessels.

The apparatus used is, as schematically shown in FIG. 3, centered on a core chamber 31 in which a robot for transporting a substrate such as a silicon substrate is assembled. In this core chamber, a substrate storage chamber 32 and a deposition step are provided. The CVD chamber 33 for performing the annealing and the annealing chamber 34 for performing the plasma annealing are connected to each other via a gate valve 35. The CVD chamber 33 and the annealing chamber 34 are connected to a vacuum evacuation system (not shown) such as a vacuum pump, and the annealing chamber 34 can heat the substrate by a heating means such as an IR lamp. , And so that RF power can be applied to the substrate. The known substrate transfer robot provided in the core chamber 31 can load and unload substrates from the substrate storage chamber 32, the CVD chamber 33, and the annealing chamber 34 around the core chamber, and into and out of these chambers. In addition, it is designed such that it can be freely transferred from the substrate storage chamber 32 to the CVD chamber 33 and from the CVD chamber to the annealing chamber 34.

First, the substrate is transferred from the substrate storage chamber 32 into the CVD chamber 33 via the core chamber 31.
Under the same conditions as above, a layer rich in carbon was deposited on the substrate. The substrate on which the carbon-rich layer was deposited was transported from the CVD chamber 33 into the annealing chamber 34 and placed on the susceptor. The temperature of the susceptor was almost the same as the temperature of the CVD chamber. Next, the plasma forming gas (Ar) was supplied into the annealing chamber 34 through the mass flow controller at 100 SCCM.
While flowing the substrate and heating the substrate with an IR lamp, 500 W of RF power was applied to the substrate from the RF source for 30 seconds from the RF source while the inside of the chamber 34 was maintained at 13.3 Pa, as in Example 1, and argon was applied. Exposure to plasma, that is, plasma annealing was performed for 30 seconds to obtain a tantalum-carbon thin film of about 50 angstroms.

The above-described deposition step and plasma annealing step were defined as one cycle, and this cycle was repeated four times to stack the desired tantalum-carbon thin film on the substrate. The obtained thin film has the same composition ratio as in Example 1, the thickness is about 200 Å,
The specific resistance was 370 μΩ · cm. Example 4 The method described in Example 1 was repeated to form a tantalum-carbon thin film on a substrate having wiring holes (or trenches) of a semiconductor device.
With SiH ₄ gas, gas amount 10 SCCM, substrate temperature 4
Thermal annealing was performed under the conditions of 00 ° C. and a pressure of 0.1 Torr in the reaction vessel. Thereby, the tantalum on the side wall of the wiring hole is
It was clear that the film quality of the carbon-based thin film was modified and densified, and the barrier property was improved.

[0024]

According to the thin film forming method of the present invention, a tantalum-carbon based thin film can be formed as a barrier layer at a low film forming temperature. The effect of solving problems such as generation of defects due to the treatment is obtained, and the tantalum-carbon thin film of the present invention has a low specific resistance and is useful as a barrier layer.

[Brief description of the drawings]

FIG. 1 is a configuration diagram schematically showing an example of the configuration of a thermal CVD apparatus used in the present invention.

FIG. 2 is a cross-sectional view of a substrate schematically showing a state in which a layer containing a large amount of carbon is formed on the substrate according to the present invention.

FIG. 3 is a configuration diagram schematically showing another example of the configuration of the thermal CVD apparatus used in the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Reaction container (vacuum reaction tank) 2 Raw material container 3, 7, 9 Mass flow controller 4 Vaporizer 5 Substrate 6 Hot plate 8 Heat exchanger 10 RF source 21 Si substrate (or lower wiring diagram) 22 Insulating layer 23 Contains much carbon Radar layer 31 Core room 32 Substrate storage room 33 CVD room 34 Annealing room 35 Gate valve a Pressurized gas b Carrier gas c Plasma forming gas H Heater

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Yasushi Higuchi 523 Yokota, Yamatake-cho, Yamatake-gun, Chiba Japan Semiconductor Technology Laboratory (72) Inventor Kenzo Nagano 523 Yokota, Yamatake-cho, Yamatake-gun, Chiba Japan Nippon Vacuum Engineering (72) Inventor Yasuhiro Takuma 523 Yokota, Yamatake-cho, Yamatake-gun, Chiba Prefecture F-term (reference) 4K030 AA11 AA16 AA18 BA17 BA27 DA08 DA09 FA10 HA01 JA10 LA01 LA15 4M104 BB34 DD45 DD77 DD78 FF18 HH20 5F033 HH36 JJ36 MM13 NN07 PP02 PP11 QQ00 QQ73 QQ85 QQ98 WW00 XX10

Claims (9)

[Claims] 1. A step of thermally decomposing a tantalum-containing organometallic compound by a chemical vapor deposition method to deposit a carbon-rich layer on a substrate, and applying a bias to the substrate to remove the carbon-rich layer by plasma. Exposing to a tantalum-carbon thin film. 2. The method according to claim 1, wherein the step of depositing the carbon-rich layer is performed at a substrate temperature of 250 to 400 ° C. 3. The method according to claim 1, wherein the tantalum-containing organometallic compound is an alkyl-substituted amino tantalum compound. 4. The method of claim 1, wherein the step of depositing the carbon-rich layer and the step of exposing to the plasma are performed without removing the substrate from a vacuum environment.
3. The forming method according to any one of 3. 5. The method according to claim 1, wherein the step of depositing the carbon-rich layer and the step of exposing to the plasma are performed in a single vacuum processing chamber. 6. The method according to claim 1, wherein the plasma contains at least one of nitrogen ions, nitrogen-containing ions, argon ions, krypton ions, and xenon ions. Method. 7. The method according to claim 1, wherein the step of depositing the layer containing a large amount of carbon and the step of exposing to the plasma constitute one cycle, and the cycle is repeated a plurality of times. Forming method. 8. The step of depositing a layer rich in carbon according to claim 1 and the step of exposing the layer rich in carbon to plasma while applying a bias to the substrate have been completed. Thereafter, a method of forming a tantalum-carbon thin film, further comprising thermally annealing the substrate in a silane-based gas atmosphere. 9. A tantalum-carbon thin film obtained by the method according to claim 1, wherein the specific resistance is 35.
A tantalum-carbon thin film having a thickness of 0 to 2000 μΩ · cm.