JPH1032248A - Formation of tungsten film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a load of a heat history to a base and also to simplify a treatment of the formation of a W film in a method of forming the W (tungsten) film. SOLUTION: A contact hole 22a is formed in an insulating film 22 covering the surface of a substrate 20 and thereafter, a Ti layer 24a and a TiN layer 24b are formed in order on the film 22 by a sputtering treatment in such a way as to cover the hole 22a. After the surface of the layer 24b is renitrided by an N2 plasma treatment in a reaction chamber for WCVD use, the formation of a W film is conducted in the following three steps. After the initiation step, in which SiH4 gas is flowed to form an amorphous Si film, the new creation step, in which WF6 +SiH4 gas is made to flow to form nuclei of W, is conduct and thereafter, the main step, in which WF6 +H2 gas is flowed to form the W film, is conducted. The layer 24b may be formed by a method wherein the surface of the layer 24a is nitrided by a plasma treatment and the layer 24b is formed on the nitrided surface of the layer 24a.

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 W (tungsten) film suitable for forming wiring of an LSI, and more particularly to a TiN (titanium nitride) film formed by plasma treatment in a reaction chamber used for vapor deposition of a W film. 3) Re-nitriding the exposed portion of the layer reduces the thermal history load on the base and simplifies the W film formation process.

[0002]

2. Description of the Related Art Conventionally, it has been known that in forming an LSI wiring, the flatness of the wiring is improved by embedding a W plug in a connection hole provided in an insulating film. As a method of forming a W film used for forming a W plug, a method shown in FIG. 8 has been proposed.

In step 10, as shown in FIGS. 9 and 10, S covering the surface of a semiconductor substrate 20 such as Si (silicon) is used.
After forming the contact hole 22a in the insulating film 22 of iO ₂ or the like, sequentially forming a Ti (titanium) layer 24a and a TiN layer 24b by sputtering. The connection hole 22a allows a wiring to be connected to the N ⁺ -type impurity-doped region 20a provided on the surface of the P-type semiconductor substrate 20 as an example. The TiN layer 24b is a conductive layer having a barrier property that improves the adhesion of W to the insulating film 22 and prevents interdiffusion between the semiconductor and W, and the Ti layer 24a is a conductive layer for reducing the contact resistance.

[0004] Next, in step 12, the substrate was set 20 to a predetermined position of the processing chamber of the lamp annealing apparatus, N ₂
The exposed portion of the Ti layer 24a and the exposed portion of the TiN layer 24b are nitrided by performing an annealing process in a (or NH ₃ ) gas atmosphere. When such nitriding is finished,
The substrate 20 is taken out of the processing chamber of the lamp annealing apparatus.

Next, in step 14, the substrate 20 is set at a predetermined position in a reaction chamber used for CVD (chemical vapor deposition) of W, and the Ti layer 24a is nitrided by flowing SiH ₄ gas into the reaction chamber. Part and TiN layer 2
Amorphous Si film covering nitrided portion 4b (not shown)
To form Then, in step 16, WF is added to the reaction chamber.
By flowing ₆ + SiH ₄ gas, a W nucleus (not shown) is formed on the amorphous Si film. Thereafter, in step 18, a WF ₆ + H ₂ gas is supplied to the reaction chamber to cover the W nucleus and form a W film 26 having a desired thickness.

Steps 14 and 16 are called an initiation step and a nucleation step, respectively.
8 is a preparation process.

The first purpose of performing the nitriding process in step 12 is to prevent the W film 26 from peeling off.
That is, at the stage after the sputtering process, Ti and Ti
Since there is a difference in coverage between N and N (Ti is more likely to wrap around), the Ti layer 24a is not covered with the TiN layer 24b near the end of the substrate (wafer) 20 as shown in FIG. Often. Step 1 in such a state
8, the W film 26 is formed as shown in FIG.
Is formed in direct contact with the Ti layer 24a near the end of the substrate 20. W formed in direct contact with Ti layer 24a
The film portion is easily peeled, causing particles to be generated. Therefore, in step 12, the exposed portion of the Ti layer 24a is nitrided (TiN-ized) to prevent the W film 26 from peeling.

The second purpose of performing the nitriding treatment in step 12 is to improve the barrier properties of TiN layer 24b. That is, at the end of the sputtering process,
The TiN layer 24b has a columnar structure and lacks barrier properties. When the W film 26 is formed in step 18 in such a state, as shown in FIG.
Enters the N ⁺ -type region 20a as shown by the broken line B,
The leakage current of the PN junction may increase. Therefore,
In step 12, the exposed portion of the TiN layer 24b is nitrided to improve the barrier property.

In steps 14 and 16, the formation of the amorphous Si film and the formation of the W nucleus are performed by the TiN layer 24b.
This is because the barrier property of the W film 26 is supplemented and the quality of the W film 26 is improved.

After forming the W film 26 as shown in FIGS. 9 and 10, when forming the wiring, as an example, the W film 26 and the TiN / Ti layer 24 are exposed until the upper surface of the insulating film 22 is exposed.
Is etched back, and the W film 26 and T
The iN / Ti layer 24 is left. Then, an Al alloy layer is deposited as a wiring material layer on the upper surface of the insulating film 22, and the Al alloy layer is patterned by photolithography and selective etching to form the W film 26 and the TiN /
A wiring layer connected to the Ti layer 24 is formed.

[0011]

According to the conventional above technique [0005], since the nitriding treatment by lamp annealing, large load of thermal history for foundation, Ti layer 24a and the N ⁺ -type, as shown in FIG. 10 The titanium silicide layer S may be formed by the reaction with the region 20a. The insulating film 22 is an interlayer insulating film, and the layers 24a, 24b,
When the conductive layer 26 is connected to the lower wiring made of Al alloy or the like through the connection hole 22a, defects such as hillocks, nodules, and voids may occur in the Al alloy layer forming the lower wiring.

In addition, the CV of W after the lamp annealing process
Since the substrate 20 is exposed to the atmosphere before the D treatment, the TiN
Moisture, contaminants, and the like easily adhere to the surface of the layer 24b. Therefore, the initiation step 14 and the nucleation step 16 are indispensable for preventing abnormal growth of W, and the process is complicated. In addition, particles may be generated due to abnormal growth of W.

Further, when the W film 26 is formed, a void V may be generated in the W film 26 as shown in FIG. That is, in the W CVD process, the thickness of the TiN layer 24b at the bottom of the connection hole 22a is important,
4b does not have good coverage at the bottom of the connection hole 22a. In order to obtain required coverage at the bottom of the connection hole 22a, it is necessary to increase the deposition thickness of the TiN layer 24b. However, in this case, as shown in FIG. 10, a part of the TiN layer 24b protrudes near the opening end of the connection hole 22a, suppressing the W deposition near the bottom of the connection hole 22a and generating a void V.

A first object of the present invention is to provide a novel W film forming method capable of reducing the load of thermal history on a base and simplifying the W film forming process.

A second object of the present invention is to provide a novel method capable of reducing the load of thermal history on the underlayer, simplifying the W film formation process, and preventing the occurrence of voids in the W film. An object of the present invention is to provide a W film forming method.

[0016]

A first W according to the present invention is provided.
The film forming method includes a step of forming a titanium layer on an insulating film covering a substrate, a step of forming a titanium nitride layer on the titanium layer, and a step of forming the titanium layer in a reaction chamber for vapor-depositing tungsten. Nitriding the exposed portion of the nitride layer and the exposed portion of the titanium layer by plasma treatment; and vapor-depositing tungsten over the nitrided portion of the titanium nitride layer and the nitrided portion of the titanium layer in the reaction chamber. Forming a tungsten film.

According to such a method, the nitriding treatment is performed by the plasma treatment which can be performed at a lower temperature than the lamp annealing treatment, so that the load of the thermal history on the base can be reduced. Further, since the nitridation process and the W film formation process are continuously performed in the reaction chamber for WCVD, the process can be shifted to the W film formation process without exposing the target substrate to the atmosphere, and the initiation step and the nucleation step can be performed. It can be shortened or omitted.

In a second W film forming method according to the present invention, a step of forming a titanium layer on an insulating film covering a substrate and a step of forming an exposed portion of the titanium layer in a reaction chamber for vapor-phase deposition of tungsten are performed. Forming a titanium nitride layer covering the titanium layer by nitriding by plasma treatment, and forming a tungsten film by vapor-phase deposition of tungsten covering the titanium nitride layer in the reaction chamber. .

According to such a method, the exposed portion of the titanium layer is nitrided to form the titanium nitride layer by the plasma treatment which can be performed at a lower temperature than the lamp annealing treatment. Load can be reduced. Further, since the nitriding process and the W film forming process are performed in the reaction chamber for WCVD, the process can be shifted to the W film forming process without exposing the substrate to be processed to the atmosphere, and the initiation step and the nucleation step can be shortened or reduced. Can be omitted.

In addition, since the titanium nitride layer is formed by nitriding the titanium layer, the titanium nitride layer protrudes near the opening end of the connection hole as in the case where the titanium nitride layer is formed by sputtering. Is not formed, and generation of voids in the W film can be prevented.

[0021]

FIG. 1 shows a method of forming a W film according to an embodiment of the present invention.

In step 10, as shown in FIGS. 2 and 3, a connection hole 22a is formed in an insulating film 22 of SiO ₂ or the like covering the surface of a semiconductor substrate 20 of Si or the like, and then a Ti layer 24a and a TiN The layers 24b are sequentially formed. 1 to 3, the same parts as those in FIGS. 7 to 9 are denoted by the same reference numerals, and detailed description thereof will be omitted.

In the sputtering process for forming the Ti layer 24a, the processing conditions are as follows: temperature: 100 to 200 [° C.] power: 800 to 2000 [W] pressure: 3 to 5 [mTorr] Thickness of the layer 24a: 20 ４０40 [nm].

In the sputtering process for forming the TiN layer 24b, the processing conditions are as follows: temperature: 100 to 200 [° C.] power: 4000 to 6000 [W] pressure: 3 to 5 [mTorr] Thickness of the layer 24b: 60 １２０120 [nm].

The Ti layer 24a and the TiN layer 24b can be formed by a chemical vapor deposition (CVD) method using ECR plasma instead of the sputtering process.

The conditions for forming the Ti layer 24a can be set as follows: Gas: TiCl ₄ + N ₂ + Ar Pressure: 1 to 5 [mTorr] Microwave power: 2 to 5 [kW]

The conditions for forming the Ti layer 24b are as follows: Gas: TiCl ₄ + NH ₃ + N ₂ + H ₂ + Ar Pressure: 1 to 5 [mTorr] Microwave power: 2 to 5 [kW] .

The TiN layer 24b formed by the sputtering process or the CVD method has not only a columnar structure as described above, but also a Ti _x N ₍ N) having a stoichiometric composition. _1-x)
Includes defects at the atomic level.

The growth of the Ti layer 24a and a TiN layer 24b is connected the thickness of the periphery of the hole 22a and T _A, and the thickness at the bottom of the connection hole 22a and T _B, usually, T _B <T
Proceed to become _A. For example, in the case of the Ti layer 24a, if T _A = 20 [nm], T _B = 5 to 10 [n
m], and in the case of the TiN layer 24b, T _A = 100 [n]
When m], T _B = 8~12 a [nm]. From this, it can be seen that Ti has better bottom coverage than TiN.

Next, in step 12A, the substrate 20 is set at a predetermined position in the reaction chamber for WCVD without being exposed to the air, and the exposed portions of the Ti layer 24a and the TiN layer 24b are nitrided by plasma processing. The processing conditions at this time may be, for example, gas: nitrogen (N ₂ ) temperature: 400 to 500 [° C.] power: 300 to 800 [W] pressure: 0.5 to 5 [Torr].

In the plasma treatment, not limited to nitrogen gas, ammonia NH ₃ , hydrazine N ₂ H ₄ , monomethylhydrazine (MMH) CH ₃ NH.NH ₂ , dimethylhydrazine (DMH) (CH ₃ ) ₂ N.NH ₂
Etc. can be used as a source gas.

As a result of the nitriding treatment, the exposed portion of the TiN layer 24b is renitrided, and the TiN layer 24b is not stoichiometric in composition only by being formed by sputtering or CVD.
_{Since xN (1-x)} is converted to stoichiometric TiN, the exposed portion of the TiN layer 24b is completely converted to TiN,
Further, defects at the atomic level are reduced. For this reason, TiN
The barrier properties of the layer 24b are improved. In the vicinity of the end of the substrate 20, the exposed portion of the Ti layer 24a is nitrided as shown in FIG.
It is covered with the iN layer 24c.

Next, in step 14, step 12A
A flow of SiH ₄ gas into the same reaction chamber as that used in Step 1 was applied to cover the TiN layers 24b and 24c to form amorphous Si.
A film (not shown) is formed. This is an initiation step, and the processing conditions are as follows: temperature: 400 to 500 [° C.] Pressure: 0.5 [Torr] SiH ₄ flow rate: 10 to 50 [sccm] Processing time: 30 to 60 [seconds] be able to.

Next, in step 16, a nucleus of W is formed on the amorphous Si film by flowing WF ₆ + SiH ₄ gas into the same reaction chamber used in step 14.
This is a nucleation step, and the processing conditions are as follows: temperature: 400 to 500 [° C.] pressure: 1 [Torr] WF ₆ flow rate: 20 [sccm] SiH ₄ flow rate: 10 [sccm] Processing time: 60 to 120 [Second] Thickness of W nucleus: 10 to 50 [nm].

Next, in step 18, a blanket-shaped W film 26 is formed by flowing WF ₆ + H ₂ gas into the same reaction chamber used in step 16 to cover the W nucleus. This is the main step, the treatment conditions, temperature: 400 to 500 [° C.] pressure: 40~90 [Torr] WF ₆ flow rate: 50~100 [sccm] H ₂ flow rate: 400 to 2,000 [sccm] film 26 thickness: 400 to 1000 [nm].

According to the W film forming method described above, step 1
By the nitriding treatment of 2A, Ti _x N _(1-x) of the layer 24b becomes complete TiN, and the barrier property of the TiN layer 24b is improved. Therefore, the tear as shown by the broken line B in FIG. 10 can be prevented. Further, in the vicinity of the end of the substrate 20, the W film 26 is formed on the TiN layer 24c covering the Ti layer 24a as shown in FIG. Particle generation can be prevented.

Since the nitriding treatment of step 12A is performed at a low temperature of about 400 to 500 ° C. by the N ₂ plasma treatment, the load of the thermal history on the base is reduced. Therefore, as shown in FIG. 3, when making contact with the N ⁺ type region 20a, Ti of the layer 24a and Si of the region 20a are formed.
Does not react to form titanium silicide.

The steps of nitriding TiN and Ti by plasma processing 12A, the initiation step 14 for forming nuclei of W, the nucleation step 16, and the step 18 of forming blanket W are all performed by a single reaction. Since the process is performed in a chamber, the substrate 20 to be processed is subjected to the W film forming process without being exposed to the air after the nitriding process, and the moisture and the contaminants on the surfaces of the TiN layers 24b and 24c are formed. Etc. can be avoided. Accordingly, in the initiation step 14 and the nucleation step 16, the processing time can be reduced by about 30 to 50% as compared with the related art. In some cases, steps 16 and 14 can be omitted. If steps 14 and 16 are omitted, dangerous SiH ₄ gas is not used, so that the equipment is simplified and safety is improved. Further, the TiN layers 24b, 2
Since the W film 26 is grown on the clean surface of 4c, abnormal growth hardly occurs, and generation of particles due to abnormal growth can be prevented.

4 and 5 show a W film formation state by a W film formation method according to another embodiment of the present invention. FIG. 4 shows a state of a substrate end portion, and FIG. Indicates the situation. 4 and 5, the same parts as those in FIGS. 2 and 3 are denoted by the same reference numerals, and detailed description will be omitted.

The embodiment shown in FIGS. 4 and 5 differs from the embodiment shown in FIGS. 1 to 3 in that the TiN layer 24b is formed by nitriding the Ti layer 24a, and is otherwise the same as the embodiment shown in FIGS. is there. That is, in the step corresponding to step 10 in FIG. 1, the connection hole 22a is covered on the insulating film 22 and the sputtering process is performed to 20 to 40 [nm] in the same manner as described above.
A Ti layer 24a having a thickness of 10 nm is formed. In a step corresponding to step 12A in FIG. 1, the exposed portion of the Ti layer 24a is nitrided by N ₂ plasma treatment in a reaction chamber for WCVD to form a TiN layer 24 having a thickness of 5 to 20 [nm].
b is formed. The conditions of the nitriding treatment at this time can be the same as those described above. Thereafter, the TiN layer 24b is processed in the same manner as in steps 14, 16, and 18 of FIG.
400 to 1000 so as to fill the connection hole 22a
A W film 26 having a thickness of [mm] is formed.

According to the W film forming method described above with reference to FIGS. 4 and 5, the same operation and effects as those of the W film forming method described above with reference to FIGS. 1 to 3 can be obtained, and the generation of void V as shown in FIG. There is an effect that can be prevented. That is, as illustrated above, at the bottom of the connection hole 22a, Ti is
The coverage is better, and in the N ₂ plasma treatment, nitriding proceeds almost uniformly inside and outside the connection hole 22a.
For this reason, as shown in FIG.
The iN layer 24b has a smaller protrusion near the opening end of the connection hole 22a than the TiN layer 24b in FIG. 3, and does not hinder the W deposition near the bottom of the connection hole 22a. Therefore, the W film 26 can be formed without generating a void.

According to the W film forming method shown in FIGS.
Since the iN sputtering process is unnecessary, there is an advantage that the process is simplified.

After the W film 26 is formed by the W film forming method of FIGS. 1 to 3 or the W film forming method of FIGS. 4 and 5, wirings can be formed as shown in FIG. That is, the insulating film 22
Film 26 and TiN / Ti layer 2 until the upper surface of
4 is etched back to leave the W film 26 and the TiN / Ti layer 24 in the connection hole 22a. Then, the insulating film 22
An Al alloy layer is deposited as a wiring material layer on the upper surface of the substrate, and the Al alloy layer is patterned by photolithography and selective dry etching to form a wiring layer 28 connected to the W film 26 and the TiN / Ti layer 24 in the connection hole 22a. To form

In such a wiring forming method, TiN
/ Ti layer 24 is left without being etched back, and TiN
The laminate of the / Ti layer 24 and the wiring material layer may be patterned according to a desired wiring pattern. Also, T
When the iN / Ti layer 24 is etched back, a base layer of TiN or the like may be laid below the wiring material layer, and the lamination of the base layer and the wiring material layer may be patterned.

FIG. 7 shows an example in which the W film forming method of the present invention is applied to the formation of the second and subsequent wiring layers.

After an interlayer insulating film 34 is formed on the insulating film 30 so as to cover the wiring layer 32, a connection hole 34a reaching the wiring layer 32 is formed in the insulating film 34 by photolithography and selective dry etching. Then, the TiN / Ti layer 36 and the W film 38 are formed on the insulating film 34 by the W film forming method of FIGS. 1 to 3 or the W film forming method of FIGS. Thereafter, in the same manner as described above with reference to FIG. 6, the W film 38 and the TiN / Ti layer 36 are etched back (etching back of the W film 38 alone is also possible), and the wiring material layer is deposited (TiN under the wiring material layer). And the like, and a process such as patterning of the adhered layer can be performed.
A wiring layer 40 connected to the W film 38 and the TiN / Ti layer 36 in 4a is formed.

In the method of forming a W film according to the present invention, since the thermal history load on the base is reduced as described above, the wiring layer 32 is formed when the TiN / Ti layer 36 and the W film 38 are formed. The load of the thermal history on the Al or Al alloy layer that constitutes is small, and defects such as hillocks, nodules, and voids in the Al or Al alloy layer can be reduced.

[0048]

As described above, according to the present invention, the surface of the titanium nitride layer is renitrided by the plasma treatment or the titanium nitride layer is formed on the surface of the titanium layer. The effect of reducing the heat history load and improving the wiring formation yield can be obtained.

Further, since the W film forming process is performed in the reaction chamber for WCVD after the nitriding process without exposing the substrate to be processed to the atmosphere, the initiation step and the nucleation step can be shortened or omitted. There is also an effect that the process can be simplified.

Further, since the W film is formed on the stoichiometric TiN layer without being formed on the Ti layer, the W film is hardly peeled off, and the generation of particles due to the peeling of the W film is prevented. There are also effects that can be done.

[Brief description of the drawings]

FIG. 1 is a flowchart showing a W film forming method according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a state of forming a W film on an edge of a substrate by the method of FIG. 1;

FIG. 3 is a cross-sectional view showing a W film formation state of a connection hole by the method of FIG. 1;

FIG. 4 is a cross-sectional view showing a W film formation state at an edge of a substrate by a W film formation method according to another embodiment of the present invention.

FIG. 5 is a cross-sectional view showing a W film formation state of a connection hole according to the embodiment of FIG. 4;

FIG. 6 is a cross-sectional view for explaining a wiring forming method as one application example of the W film forming method of the present invention.

FIG. 7 is a cross-sectional view for explaining a wiring forming method as another application example of the W film forming method of the present invention.

FIG. 8 is a flowchart showing a conventional W film forming method.

9 is a cross-sectional view showing a state of forming a W film at an end of a substrate when nitriding is not performed in the method of FIG. 8;

FIG. 10 is a cross-sectional view for explaining a problem in the method of FIG. 8;

[Explanation of symbols]

Reference numeral 20: semiconductor substrate, 22: insulating film, 22a: connection hole, 2
4: TiN / Ti layer, 24a: Ti layer, 24b: TiN
Layer, 26: W film.

Claims (6)

[Claims] A step of forming a titanium layer on an insulating film covering a substrate; a step of forming a titanium nitride layer on the titanium layer; and forming the titanium layer in a reaction chamber for vapor-phase deposition of tungsten. Nitriding the exposed portion of the nitride layer and the exposed portion of the titanium layer by plasma treatment; and vapor-depositing tungsten in the reaction chamber to cover the nitrided portion of the titanium nitride layer and the nitrided portion of the titanium layer. Forming a tungsten film by performing the method. A step of forming a connection hole for wiring in an insulating film covering the substrate; a step of forming a titanium layer on the insulating film so as to cover the connection hole; Forming a nitride layer in a reaction chamber for vapor-phase deposition of tungsten; nitriding the exposed portion of the titanium nitride layer and the exposed portion of the titanium layer by plasma processing; and forming the titanium nitride in the reaction chamber. Forming a tungsten film by vapor-depositing tungsten so as to cover the nitrided portion of the ride layer and fill the connection hole. 3. The step of forming the tungsten film,
3. The tungsten film forming method according to claim 1, further comprising a step of forming an amorphous silicon film and a nucleus of tungsten sequentially before forming the tungsten film. 4. A step of forming a titanium layer on an insulating film covering the substrate, and covering the titanium layer by nitriding an exposed portion of the titanium layer by plasma treatment in a reaction chamber for vapor-phase deposition of tungsten. A tungsten film forming method, comprising: forming a titanium nitride layer; and forming a tungsten film by vapor-depositing tungsten in the reaction chamber so as to cover the titanium nitride layer. 5. A step of forming a connection hole for wiring in an insulating film covering the substrate; a step of forming a titanium layer on the insulating film so as to cover the connection hole; A step of forming a titanium nitride layer covering the titanium layer by nitriding an exposed portion of the titanium layer by plasma treatment in the reaction chamber; and covering the titanium nitride layer and filling the connection hole in the reaction chamber. Forming a tungsten film by vapor-phase deposition of tungsten. 6. The step of forming the tungsten film,
6. The tungsten film forming method according to claim 4, further comprising a step of sequentially forming an amorphous silicon film and a nucleus of tungsten before forming the tungsten film.