JP2002025964A - Method of manufacturing semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To protect electrodes or wirings formed of high-melting metal nitride against etching at cleaning after the electrodes or wirings are formed in the manufacture of a semiconductor device provided with the electrodes or wirings formed of high-melting metal nitride. SOLUTION: A semiconductor device manufacturing method comprises a first process of forming conductor films that contain high-melting point nitride films on a semiconductor substrate, a second process of patterning the conductor films into required forms, and a third process of cleaning the patterned conductor films. A cleaning solution used in the third process of cleaning the patterned conductor films is a mixed solution of quaternary ammonium hydroxide represented by general formula, [(R1)nN(R)4-n]+OH- (R1 is a 1-2C alkyl group, R is a 1-2C alkyl group or a 1-2C hydroxy-substituted alkyl group, and R1 and R may be identical to each other or different from each other. n is an integer of 1 to 3), a hydrogen peroxide solution, and pure water.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for manufacturing a semiconductor device using a refractory metal nitride for an electrode or a wiring.

[0002]

2. Description of the Related Art MOSFETs (Metal Oxide) forming integrated circuits
The gate electrode of a Semiconductor Field Effect Transistor (MOS type field effect transistor) was generally made of polycrystalline silicon. However, as the gate length of the gate electrode becomes shorter due to the higher integration of LSI,
The wiring resistance of the gate electrode is increased, which causes a problem of delay in signal propagation speed. Therefore, using an alloy (silicide) of silicon and a refractory metal such as WSi ₂ , TiSi ₂ , or MoSi ₂ which is a material having a lower resistance than polycrystalline silicon, the silicide layer and the polycrystalline silicon layer are stacked to form two layers. It has been proposed to use a gate electrode having a structure.

FIG. 1A shows an example of a method of manufacturing a gate electrode having a two-layer structure of polycrystalline silicon and tungsten silicide.
This will be described with reference to (c).

First, a field oxide film 13 for element isolation and a p-type well layer 12 are formed on a silicon substrate 11. Next, a gate oxide film 14 is formed by a thermal oxidation method (FIG. 1A).

Thereafter, a polycrystalline silicon film 15,
A tungsten silicide film 16, an oxide film 17, and a silicon nitride film 18 are formed by a chemical vapor deposition method (hereinafter referred to as a CVD method) (FIG. 1B).

Next, patterning is performed by a usual photolithography method, and a total of four layers of a polycrystalline silicon film 15, a tungsten silicide film 16, an oxide film 17 and a silicon nitride film 18 are processed into a shape of a gate electrode by dry etching. (FIG. 1 (c)).

After forming the gate electrode, cleaning is performed with a generally used cleaning liquid, for example, a mixed solution of aqueous ammonia, hydrogen peroxide and ultrapure water. This is because during the dry etching, the photoresist and the gas used for the dry etching and the material constituting the gate electrode react to remove compounds generated on the sidewalls of the gate electrode and particles generated during the dry etching. is there.

However, as the degree of integration of LSI further increases,
A gate electrode having a lower resistance than the gate electrode having the two-layer structure is required, and tungsten is attracting attention as a gate electrode material satisfying such a requirement. As an example, K. Kasai et al., “W / WNx / Poly-Si Gate Technolog
y for Future High Speed Deep Submicron CMOS LSI
s ", 1994, International Electron Device Conference
e Conference), a MOSFET with a three-layer structure consisting of a polycrystalline silicon layer, a tungsten nitride layer, and a tungsten layer
Has been proposed. In this structure, the tungsten nitride layer is disposed to prevent the polycrystalline silicon layer and the tungsten layer from reacting to form a high-resistance silicide layer. Note that the tungsten nitride layer is deposited by a reactive sputtering method.

[0009]

However, according to the study by the inventors, when manufacturing a MOSFET having a gate electrode having a three-layer structure of the above-mentioned polycrystalline silicon layer, tungsten nitride layer and tungsten layer, it is difficult to form a gate electrode. In the subsequent cleaning, it has been found that the resistance of the tungsten nitride layer to the cleaning solution becomes a problem. That is, when a MOSFET having the three-layered gate electrode is manufactured by a generally known method, the tungsten nitride layer may be dissolved in the cleaning solution and disappear. This is further shown in FIG.
This will be described using (c). When manufacturing a MOSFET having this three-layered gate electrode by a generally known method,
First, a field oxide film 23 for element isolation and a p-type well layer 22 are formed on a silicon substrate 21. Next, after forming a gate oxide film 24 by a thermal oxidation method, a polycrystalline silicon film 25 is deposited thereon by a chemical vapor deposition method (hereinafter referred to as a CVD method) (FIG. 2A).

On this polycrystalline silicon film 25, a tungsten nitride film 26 and a tungsten film 27 are formed by a sputtering method. Thereafter, the plasma CV is formed on the tungsten film 27.
A silicon nitride film 28 is formed by the method D (FIG. 2B).

Next, patterning is performed by a usual photolithography method, and a total of four layers of a polycrystalline silicon film 25, a tungsten nitride film 26, a tungsten film 27 and a silicon nitride film 28 are processed by dry etching into a shape of a gate electrode. (FIG. 2 (c)). During the dry etching, the gas for etching and the material of the three layers constituting the resist or the gate electrode react to generate a compound,
This compound adheres to the side wall of the gate electrode. for that reason,
After completion of the dry etching, the substrate shown in FIG. 2C is washed to remove a product film attached to the side wall of the gate electrode.

Thereafter, a source region and a drain region are formed in the p-type well layer 22, and a source electrode, a drain electrode, an insulating layer and the like are formed to complete the MOSFET.

According to the evaluations of the inventors, in the above-mentioned cleaning step, cleaning liquids generally used in a semiconductor manufacturing process, for example, a mixed solution of ammonia water, hydrogen peroxide water and ultrapure water, and hydrochloric acid and hydrogen peroxide are used. When a mixed solution of hydrogen oxide water and ultrapure water or a mixed solution of hydrofluoric acid, hydrogen peroxide solution and ultrapure water is used, the tungsten nitride film 26 is easily dissolved in the cleaning solution. I understood. Therefore, in the cleaning step, the tungsten nitride film 26
In the worst case, etching may be performed from the side surface of the gate electrode, or the upper layer of the tungsten nitride film 26 may be lost, which causes a problem that device characteristics are deteriorated.

The present invention has been made in view of the above problems, and is a method of manufacturing a semiconductor device using a high melting point metal nitride for an electrode or a wiring. It is an object of the present invention to provide a method of manufacturing a semiconductor device capable of suppressing nitride etching.

[0015]

In order to achieve the above object, the present invention provides a process for forming a plurality of conductive films including a refractory metal nitride film on a semiconductor substrate, and forming the conductive film into a desired shape. A processing step of patterning, and a step of cleaning the processed conductor film, the cleaning liquid used in the cleaning step, at least a general formula

[0016]

Embedded image

(R ¹ is an alkyl group having 1 to 2 carbon atoms, R is an alkyl group having 1 to 2 carbon atoms or a hydroxy-substituted alkyl group having 1 to 2 carbon atoms, and R ¹ and R are the same and N is an integer of 1 to 3). By washing with a mixed solution containing a quaternary ammonium hydroxide, a hydrogen peroxide solution, and pure water, This is to prevent the etching of the refractory metal nitride film. Here, the refractory metal nitride film includes titanium nitride, tungsten nitride, tantalum nitride, and the like.

The quaternary ammonium hydroxide used in the cleaning solution for the semiconductor device of the present invention includes tetramethylammonium hydroxide, tetraethylammonium hydroxide, trimethylethylammonium hydroxide, dimethyldiethylammonium hydroxide, triethylmethylammonium. Hydroxide, trimethyl (2-hydroxyethyl) ammonium hydroxide and the like can be mentioned.

Among these quaternary ammonium hydroxides, it is preferable that R ¹ and R have a small number of carbon atoms, especially tetramethyl ammonium hydroxide (hereinafter referred to as TM).
AH) is preferred.

The mixed solution of the quaternary ammonium hydroxide, the hydrogen peroxide solution and the ultrapure water, which is the cleaning solution for the semiconductor device of the present invention, has a quaternary ammonium hydroxide concentration of 0.05 to 0.3 mol in the whole solution. / L and the concentration of hydrogen peroxide solution are desirably 0.1 mol / L or less in the whole solution. The reason is that, when the quaternary ammonium hydroxide concentration is too low, the etching rate of the refractory metal nitride film is suppressed, but the desired cleaning effect cannot be obtained. While the fourth
When the concentration of ammonium hydroxide is high, the refractory metal nitride film is hardly etched, but the surface of silicon or polycrystalline silicon is roughened and the cleaning effect is impaired. Hydrogen peroxide solution is necessary to prevent the above-described surface roughness of silicon and polycrystalline silicon. However, when the concentration of hydrogen peroxide solution is high, the etching rate of the refractory metal nitride film is high and high. This is because the melting point metal nitride film may disappear.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings.

(First Embodiment) FIG. 3 shows the results of etching rates of a mixed solution of quaternary ammonium hydroxide, hydrogen peroxide and ultrapure water on a tungsten nitride film.
The concentration of aqueous hydrogen peroxide in the mixture was 0.02 mol / L.
, And the etching amount of the tungsten nitride film was measured by a stylus type step meter (detection lower limit: 50 °).

The quaternary ammonium hydroxide concentration is 0.004
In the region of mol / L or less, the etching rate of the tungsten nitride film increases as the concentration increases, regardless of the type of the quaternary ammonium hydroxide. However, in the region where the quaternary ammonium hydroxide concentration is higher than 0.004 mol / L,
The behavior of the tungsten nitride film for etching differs depending on the type of quaternary ammonium hydroxide.

When the number of carbon atoms of the functional group bonded to the nitrogen atom of the quaternary ammonium ion is 2 or less,
In the case of tetramethylammonium hydroxide, tetraethylammonium hydroxide, choline, and the like, the etching rate of the tungsten nitride film decreases as the quaternary ammonium hydroxide concentration increases. In the case of tetrapropylammonium hydroxide, in which the functional group bonded to the nitrogen atom of the quaternary ammonium ion has 3 carbon atoms, the carbon number is 2 or less in the concentration range of 0.004 to 0.05 mol / L. However, the etching rate increases again at 0.05 mol / L or more. Tetrabutylammonium hydroxide in which the functional group bonded to the nitrogen atom of the quaternary ammonium ion has 4 carbon atoms is 0.004 to 0.01 mo
In 1 / L, the etching rate increases with the concentration of tetrabutylammonium hydroxide.
Above / L, the etching rate is constant.

It is unknown at present why the etching behavior of the tungsten nitride film varies depending on the type or concentration of the quaternary ammonium hydroxide.
It is presumed that the reason why the etching of the tungsten nitride film is suppressed in the specific concentration region is that quaternary ammonium ions are adsorbed on the surface of the tungsten nitride and hinder the etching. In addition, with quaternary ammonium ions having a specific size or more, it is considered that the etching density is not sufficiently suppressed because the adsorption density on the surface of the tungsten nitride decreases.

Assuming that the cleaning time is 5 minutes and the effect of etching on an electrode or wiring having a width of 0.2 μm is considered, it is considered that the etching rate of the tungsten nitride film is desirably 20 ° / min or less. Therefore, the concentration of a quaternary ammonium hydroxide (TMAH, tetraethylammonium hydroxide, choline, etc.) satisfying the above conditions must be at least 0.05 mol / L or more. In consideration of cost, the quaternary ammonium hydroxide is preferably used in a concentration range of 0.05 to 0.3 mol / L.

(Second Embodiment) The evaluation results of the cleaning liquid of the present invention and the conventional cleaning liquid on the Si particle removing power will be described.

As an example of the cleaning solution of the present invention, tetramethylammonium hydroxide for semiconductor industry (hereinafter referred to as “tetramethylammonium hydroxide”)
TMAH), a mixture of hydrogen peroxide and ultrapure water (concentrations of TMAH and hydrogen peroxide in the whole solution were 0.1 mol /
L, 0.02 mol / L) and a mixture of ammonia water, hydrogen peroxide solution, and ultrapure water as conventional cleaning liquids (the ammonia concentration and hydrogen peroxide solution concentration in the whole solution are 0.8, 0.02 mol / L, respectively)
L) was used. The Si particle-adhered wafer for evaluation was prepared in a 0.5 wt% HF solution in which Si particles were dispersed.
A wafer with an inch natural oxide film was immersed for 10 minutes.

The evaluation of cleaning was performed on a wafer with Si particles attached.
After immersion cleaning in a cleaning liquid at 40 ° C. for 5 minutes, overflow rinsing with ultrapure water for 10 minutes and drying, the number of particles of 0.2 μm or more before and after cleaning was measured with a foreign matter inspection device, and the particle removal ratio was calculated and compared. .

As a result, as shown in Table 1, the removal rate of the Si particles was higher in the mixed solution of TMAH, hydrogen peroxide solution and ultrapure water, which was the cleaning solution of the present invention, in the ammonia solution and in the cleaning solution of the conventional cleaning solution. It is higher than the mixed solution of hydrogen oxide water and ultrapure water, and it is clear that the particle removing power is superior to the conventional cleaning liquid.

[0031]

[Table 1]

(Third Embodiment) In this embodiment, a method for manufacturing a MOS field effect transistor (MOSFET) using a three-layer film containing tungsten nitride as a gate electrode will be described.

First, as shown in FIG. 2A, after a field oxide film 23 for element isolation is formed on a silicon substrate 21 by a known method, a p-type well layer 22 is formed. Further, the surface of the silicon substrate 21 between the field oxide films 23 is thermally oxidized to form a silicon oxide film having a thickness of about 10 nm. This silicon oxide film is called a gate oxide film 24. Next, a polycrystalline silicon film 25 doped with phosphorus is formed on the gate oxide film 24 by chemical vapor deposition (CVD).
(FIG. 2A).

Next, a tungsten nitride film 26 and a tungsten film 27 are formed on the polycrystalline silicon film 25 by sputtering at a thickness of 10 nm and 100 nm, respectively.
As a target at the time of this sputtering, tungsten is used for both the tungsten nitride film 26 and the tungsten film 27. When the tungsten nitride film 26 is formed, nitrogen gas is introduced into the plasma to nitride and deposit tungsten. Next, the silicon nitride film 28 is formed on the tungsten film 27 at a low temperature of about 400 ° C. by a plasma CVD method.
Is formed to a thickness of 200 nm (FIG. 2B).

Next, patterning is performed by a usual photolithography method, and a total of four layers of a polycrystalline silicon film 25, a tungsten nitride film 26, a tungsten film 27, and a silicon nitride film 28 are processed into a shape of a gate electrode by dry etching. (FIG. 2 (c)). Of these four layers, three layers of a polycrystalline silicon film 25, a tungsten nitride film 26, and a tungsten film 27 function as the gate electrode 29.
At the time of dry etching, the etching gas and the resist or the material of the three layers constituting the gate electrode react with each other to generate a compound, and this compound adheres to the gate electrode wall. After finishing, Figure 2
(c) The substrate is washed to remove a product film adhering to the side wall of the gate electrode, particles generated during dry etching, and the like. Cleaning is 22wt% for electronics industry
Tetramethylammonium hydroxide (TMA
H), and a mixed solution of 30 wt% hydrogen peroxide solution and ultrapure water for electronics industry. The concentrations of TMAH and hydrogen peroxide in the whole solution were 0.1 mol / L and 0.02 mol / L, respectively,
The wafer on which the gate electrode was patterned as shown in FIG. 2C was immersed in the solution heated for 5 minutes to be washed.
After the washing, overflow rinsing was performed in ultrapure water for 10 minutes, followed by drying.

Thereafter, as shown in FIG. 4D, the p-type well layer 22 is formed.
Inside, an n (+) type source region 30 and an n (+) type drain region 31
And the side surfaces of the four layers of the polycrystalline silicon film 25, the tungsten nitride film 26, the tungsten film 27, and the silicon nitride film 28 are covered with the silicon nitride film 32. After further covering the entire surface with the insulating film 33, n (+)
A source electrode 34 and a drain electrode 35 that reach the type source region 30 and the n (+) type drain region 31, respectively, are formed to complete the MOSFET (FIG. 4E).

For confirmation, the gate electrode 29 after the cleaning step
As a result of observing the cross section of the polycrystalline silicon film with a scanning electron microscope (SEM), the side walls of the polycrystalline silicon film 25, the tungsten nitride film 26, and the tungsten film 27 were hardly etched, and there was no problem in the shape of the gate electrode 29. .

For comparison, a mixed solution of ammonia water, a hydrogen peroxide solution and ultrapure water was used instead of a mixed solution of TMAH, hydrogen peroxide solution and ultrapure water as the cleaning solution in the above cleaning step. The same evaluation was performed. In addition, the ammonia concentration and the hydrogen peroxide solution concentration in all the solutions are each 0.
8, and 0.02 mol / L, and washed at 40 ° C. for 5 minutes. As a result of observing the cross section of the gate electrode 29 after cleaning by SEM, the tungsten nitride film 26 was completely etched by the cleaning solution, and the three layers of the tungsten nitride film 26, the tungsten film 27, and the silicon nitride film 28 disappeared. Was.

(Fourth Embodiment) In this embodiment, a method for manufacturing a wiring containing titanium nitride will be described.

First, after a CVD silicon oxide film 51 is formed on a Si substrate 11 on which a MOS type semiconductor element (not shown) is formed, a titanium nitride film 52 having a thickness of 500 ° is formed on the CVD silicon oxide film 51. , 1500 mm thick sputtered tungsten film 5
3. A 1500 .ANG. Thick CVD tungsten film 54 and a 500 .mu.m thick titanium nitride film 55 are formed as an antireflection film (FIG. 5A).

Next, after a positive resist layer 56 having a thickness of 1 μm was provided on the titanium nitride film 55, patterning was performed by ordinary photolithography (FIG. 5B).

Next, using the resist pattern as a mask,
The titanium nitride film 55, the tungsten films 53 and 54, and the titanium nitride film 52 were processed by dry etching to form metal wiring (FIG. 5C). The resist, the dry etching gas, and the wiring material react on the side wall of the wiring during dry etching to form a deposit 57.

Next, the resist pattern after the dry etching was removed by ashing treatment using plasma using oxygen gas (FIG. 5D).

Next, a mixed solution of TMAH, hydrogen peroxide solution and ultrapure water as the cleaning solution of the present invention (40 ° C., the TMAH concentration and the hydrogen peroxide concentration in the whole solution were 0.1 mol / L and 0.02 mol / L, respectively)
L) for 10 minutes. As a result, the deposit 57 formed on the side wall after the wiring processing was removed, and no etching of the wiring was observed (FIG. 5E). For comparison, cleaning was performed with a mixed solution of ammonia water, hydrogen peroxide solution, and ultrapure water instead of the above cleaning solution.
7 is insufficiently removed or the tungsten nitride film 5 is removed.
2, 55 and portions where the tungsten films 53 and 54 disappeared were observed.

[0045]

As described above, according to the present invention, a high melting point metal nitride such as tungsten nitride or titanium nitride is used.
In the manufacture of a semiconductor device used as one of the constituent materials of an electrode or a wiring, after formation of the electrode or the wiring, cleaning with a mixed solution of a quaternary ammonium hydroxide, a hydrogen peroxide solution, and ultrapure water is performed. Deposits and particles generated at the time of forming electrodes or wirings can be removed without etching the melting point metal nitride film, so that a highly reliable semiconductor device having stable element characteristics can be provided.

[Brief description of the drawings]

FIGS. 1A to 1C are cross-sectional views showing a procedure for forming a MOSFET having a two-layered gate electrode of a tungsten silicide film 16 and a polycrystalline silicon film 15 by a conventional general method.

FIGS. 2A to 2C are cross-sectional views showing a procedure for forming a MOSFET having a gate electrode having a three-layer structure of a tungsten film 27, a tungsten nitride film 26, and a polycrystalline silicon film 25.

FIG. 3 is a diagram showing an etching rate of a tungsten nitride film when a quaternary ammonium hydroxide concentration is changed while a hydrogen peroxide solution concentration is kept constant.

FIGS. 4D and 4E are cross-sectional views showing a procedure for forming a MOSFET having a gate electrode having a three-layer structure of a tungsten film 27, a tungsten nitride film 26, and a polycrystalline silicon film 25.

FIG. 5 shows a titanium nitride film 55 and tungsten films 53 and 54.
FIG. 4 is a cross-sectional view showing a procedure for forming a wiring having a three-layer structure of a titanium nitride film 52.

[Explanation of symbols]

11 silicon substrate, 12 p-type well layer, 13 field oxide film, 14 gate oxide film, 15 polycrystalline silicon film, 16 tungsten silicide film, 21 silicon substrate, 22 p-type well layer, 23 ... Field oxide film, 2
4 gate oxide film, 25 polycrystalline silicon film, 26 tungsten nitride film, 27 tungsten film, 28 silicon nitride film, 29 gate electrode, 30 n (+) type source region, 31 n (+) ) Type drain region, 32 ... silicon nitride film, 33 ... insulating film, 34 ... source electrode, 35 ... drain electrode, 51 ... silicon oxide film, 52 ... titanium nitride film, 53 ...
Sputtered tungsten film, 54 ... CVD tungsten film,
55: titanium nitride film, 56: positive resist, 57: sidewall deposit.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (Reference) H01L 29/43 H01L 29/62 G 29/78 29/78 301G (72) Inventor Tomonori Saeki Yokohama, Kanagawa 292, Yoshidacho, Totsuka-ku, Japan Hitachi, Ltd. Production Technology Laboratory (72) Inventor Hideki Tomioka 3-16, Shinmachi, Ome-shi, Tokyo 3 Hitachi, Ltd.Device Development Center Co., Ltd. (72) Inventor Masaki Ito Tokyo 6-16-16 Shinmachi, Ome-shi, Tokyo Inside the Device Development Center, Hitachi, Ltd. (72) Inventor Ken Tsugane 6-16-16 Shinmachi, Ome-shi, Tokyo 3 Inside the Device Development Center, Hitachi, Ltd. (72) Inventor Ito Haruo Kadomatsu City, Yamaguchi Prefecture 794, Higashi-Toyoi Inside the Kasado Plant of Hitachi, Ltd. (72) Inventor Norimasa Funabashi 5-20-1, Kamizuhoncho, Kodaira-shi, Tokyo F-term in Hitachi Semiconductor Group 4M104 BB01 BB40 CC05 DD37 DD42 DD65 FF13 5F033 HH04 HH19 HH33 HH34 MM08 QQ08 QQ10 QQ11 QQ19 QQ91 VV06 WW04FXXXX XX00 DA01 DC01 EC02 EC04 EC07 EK01 FA07 FA18 FC00 FC21

Claims (5)

[Claims] A step of forming a plurality of conductive films including a high melting point metal nitride film on a semiconductor substrate; a step of patterning the conductive film into a desired shape; and a step of cleaning the processed conductive film. And a cleaning solution used in the cleaning step is at least a compound represented by the general formula: (R ¹ represents an alkyl group having 1 to 2 carbon atoms, R represents an alkyl group having 1 to 2 carbon atoms or a hydroxy-substituted alkyl group having 1 to 2 carbon atoms, and R ¹ and R are different even if they are the same. Cleaning is performed with a mixed solution containing a quaternary ammonium hydroxide represented by the following formula (1), hydrogen peroxide solution, and pure water. . 2. The method according to claim 1, wherein said refractory metal nitride film is made of tungsten nitride, titanium nitride, or tantalum nitride. 3. The cleaning solution has a quaternary ammonium hydroxide concentration of 0.05 to 0.3 mol / L and a hydrogen peroxide solution concentration of 0.1 mol / L.
3. The method according to claim 1, wherein the ratio is not more than 1 / L. 4. The method according to claim 1, wherein said quaternary ammonium hydroxide is tetramethylammonium hydroxide. 5. The method of manufacturing a semiconductor device according to claim 1, wherein said semiconductor device is a field effect transistor, and said film forming step includes forming a polycrystalline silicon film, a tungsten nitride film as said conductor film. Film, tungsten film,
Alternatively, it is a step of laminating three layers of a polycrystalline silicon film, a titanium nitride film, and a tungsten film, and the processing step is a step of processing the conductor film into a shape of a gate electrode. Method.