JPH0547707A - Thin film forming method, and semiconductor device - Google Patents

Abstract

PURPOSE:To obtain a film excellent in step coverage by generating plasma in a plasma generation chamber by the action of an electric field by microwaves and a magnetic field by an exciting coil, using specified inorganic gas and metallic gas, and introducing it into a reaction chamber. CONSTITUTION:First, the inside of a device body 3 is decompressed, and metallic gas is supplied from a first introduction pipe 13 into a reaction chamber 1. Moreover, Ar, N2, and H2 gas is supplied from a second introduction pipe 15 into a plasma generation chamber 1. Next, microwaves are introduced into the plasma generation chamber 1 through a waveguide pipe 5, and also a DC power source is connected to an exciting coil 4 so as to generate a magnetic field inside the plasma generation chamber 1 and generate plasma. Next, this plasma is introduced from a second hole 12 into the reaction chamber 2 so as to form a metallic nitride film on the surface of the sample 9 which is placed on a sample stage 8 and has a contact hole high in aspect ratio. Hereby, a film excellent in step coverage can be formed, and the reliability can be improved.

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 thin film and a semiconductor device, and more particularly to a method for forming a thin film such as a TiN film formed as a barrier layer on the inner surface of a contact hole in a semiconductor device and the thin film. The present invention relates to a formed semiconductor device.

[0002]

2. Description of the Related Art A contact portion in a semiconductor device such as an LSI has a diffusion layer on the surface of a substrate as an underlayer and is connected to a wiring such as Al through a contact hole.

However, as miniaturization and higher integration of LSI progress, the diffusion layer formed on the surface of the substrate becomes shallower,
Problems such as Al spikes in the shallow diffusion layer to break the junction, or Si deposits on the bottom of the contact hole to increase the contact resistance have arisen.

In order to solve these problems, Al alloy in which about 0.5 to 2% of Si is mixed in advance in Al (Al-
1% Si, etc.) is used as an electrode wiring material, but recently the contact hole diameter has become smaller, so these
Al alloys are becoming insufficient to prevent Si precipitation.

Therefore, it has been considered to form a diffusion preventing thin film called a barrier metal between the Al alloy and the Si substrate. The TiN film has attracted attention as a barrier metal because it has low electric resistance and is chemically stable. (Yamanishi, Yoshiwara,
Kitahara, Hosokawa; "Vacuum", Vol. 30, No. 5, p347, 19
1987).

The TiN film is formed by the conventional reactive sputtering method (Reactive
It was formed by the Sputtering method). The reactive sputtering method uses an apparatus as shown in FIG.
Ti is used for 0 and Ar and N ₂ are supplied as a sputtering gas to form a TiN film on the substrate 31 (Kanamori; "Vacuum", Vol. 29, No. 9, p418, 1986).
Year). Incidentally, reference numeral 32 in the drawing denotes a coil.

However, in this method, the step coverage (St
ep Coverage) is bad, and the TiN film is applied to the contact part as shown in Fig.
It is formed as shown in FIG. As the high integration of semiconductor devices progresses to 64M DRAM and 256M DRAM, the aspect ratio (=
(Hole depth / hole diameter) gradually increases. Therefore, in this method, almost all TiN is formed at the bottom of the contact hole 35.
The membrane 33 will not stick and this method cannot be used.
That is, even if an electrode material such as W (tungsten) or Al is embedded from the state shown in FIG. 22A, voids 36 are generated inside the contact hole 35 as shown in FIG. Since the wiring is easily broken inside 35 and the TiN film 33 becomes thin at the bottom of the hole, it does not function as a barrier metal and the reliability of the manufactured LSI device cannot be ensured.

Then, as a method for forming a thin film having good step coverage, the LPCVD method (Low Pressure Chemical V
One of the thermal CVD methods called the apor Deposition method) has begun to attract attention. This method uses an apparatus as shown in FIG.
This is a method of forming a TiN film on a substrate by thermal reaction using TiCl ₄ and NH ₃ or N ₂ gas (N. Yokoyamaet
al., Vol. 136 No. 3, J. Electrochem. Soc., p8
82) (N. Yokoyama et al., Vol. 138 No. 1, J. El.
ectrochem.Soc., p190).

However, due to the reaction of TiCl ₄ + N ₂ + H ₂
Since a high temperature of about 900 to 1000 ° C. is required to form the TiN film, which adversely affects the device characteristics,
There was a problem that it could not be applied to the manufacture of LSI devices (Arthur Sherman, Extended Abstract of
the 1991 International Conference on Solid State
Devices and Materials, 1991 p177-179).

On the other hand, since the reaction of TiCl ₄ + NH ₃ is carried out at a low temperature, it is suitable for forming a barrier metal for an LSI device.
The method using NH ₃ gas was considered promising. However, TiCl ₄ and NH ₃ are mixed in the gas phase (Complex) (TiCl ₄
・ NNH ₃ ) formed, which turned into a yellow powder, which was a cause of particle generation in the equipment (MJBuiting, et al, J. Electrochem. Soc., Vol. 1).
38, No2, Feb. 1991 p500).

A TiN film is conformally formed on the contact portion by the LPCVD method as shown in FIG. In the case of the LPCVD method, the TiN film 33 is sufficiently formed at the bottom of the contact hole 35, which is preferable as the barrier metal, but the contact hole 35
The TiN film 33 having the same film thickness as the bottom portion is formed on the side wall portion of the. When the thick TiN film 33 is formed also on the side wall in this way, the diameter of the hole remaining in the contact hole 35 becomes small, and the state is substantially the same as when the contact hole having a large aspect ratio is formed. .. Therefore, when W (tungsten), Al, or the like is buried in the next step, a void 36 is generated inside the contact hole 35 as shown in FIG. 24B, and the reliability of the LSI device can be secured. There was a problem that I could not do it.

Incidentally, as described above, the apparatus shown in FIG. 23 is used for the LPCVD method. Reference numeral 40 in the figure denotes a chamber, and a gas nozzle 41 is provided in the chamber 40.
Further, the sample holder 42 is arranged, and the substrate 43 is placed on the sample holder 42. A booster pump 44 and a rotary pump 45 are connected below the chamber 40, and a pipe 47 for supplying NH ₃ is connected to the gas nozzle 41.

[0013]

In consideration of the above problems, the present inventors have conducted extensive research and completed the invention described below.

[0014] The present invention is Ar, using H _2, N ₂ gas and metal based gas, plasma is generated in the plasma generating chamber by the action of the magnetic field by the excitation coils disposed in the electric field and the ambient by the microwave, The main content is to introduce the generated plasma into a reaction chamber and form a thin film of a metal nitride film on a sample placed on a sample table.

By using such a method, a thin film having excellent step coverage is formed on the contact portion, and the thickness of the thin film formed on the side wall of the contact hole is smaller than the thickness of the thin film formed on the bottom of the contact hole. It is intended to be thin.

Another object of the present invention is to provide a method capable of forming a thin film at a low temperature that does not adversely affect the LSI device and not generating particles such as yellow powder.

More specifically, in the method for forming a thin film according to the present invention, plasma is generated in the plasma generation chamber by the action of the electric field generated by the microwave and the magnetic field generated by the exciting coil disposed around the plasma, and the generated plasma is generated. In the method of forming a thin film on the sample placed on the sample table by introducing into the reaction chamber, Ar, H ₂ and N ₂ gas is introduced into the plasma generation chamber, while a metal-based gas is introduced into the reaction chamber. To form a metal nitride film on the sample (1), and the plasma in the plasma generation chamber is generated by the action of the electric field of the microwave and the magnetic field of the exciting coil arranged around the microwave. is generated, a method of forming a thin film on the sample placed on the sample stage by introducing said to generate plasma in the reaction chamber, the plasma producing an Ar, H _2, N ₂ gas and the metallic gas A metal nitride film is formed on the sample by introducing it into a chamber (2), and further, in the thin film forming method described in (1) or (2) above, an insulating film is formed on a substrate. The titanium tetrachloride gas is used as the metal-based gas on the substrate for semiconductor device formation in which the contact hole is formed in the insulating film, and the pressure in the reaction chamber is 2.
A Ti nitride film is formed in the contact hole under the condition of 0 mTorr or less and the temperature of the sample substrate is 450 ° C. or more (3), and the semiconductor device according to the present invention has the contact hole bottom portion. Is thicker than the thickness of the Ti nitride film on the side wall of the contact hole (4), and the method for forming a thin film according to the present invention further includes the above (1), (2) ) Or (3), the method is characterized in that the film is formed while applying RF to the microwave introduction window (5), and the above (1),
The method according to (2), (3) or (5) is characterized in that after forming the Ti nitride film, H ₂ plasma treatment is performed (6).

That is, according to the method described in (1) above, Ar and H ₂ gas for promoting film formation are supplied to the plasma generation chamber, while metal-based gas such as TiCl ₄ is supplied to the reaction chamber. A direct current is passed through the exciting coil, and a microwave is introduced into the plasma generation chamber through the microwave waveguide and the microwave introduction window.

The microwave introduced into the plasma generating chamber decomposes the Ar, H ₂ and N ₂ gas supplied into the plasma generating chamber to generate plasma. When the generated plasma is introduced into the reaction chamber by the divergent magnetic field formed by the exciting coil, the metal-based gas reacts with the plasma, and the metal nitride is deposited on the sample surface placed in the reaction chamber. The supplied metal nitride film is formed.

According to the method described in (2) above, Ar,
Supplying H _2, N ₂ gas and TiCl ₄ or the like of the metal-based gas into the plasma generation chamber, the DC current with flowing to the exciting coil, a microwave waveguide, the plasma generating chamber microwaves through microwave introduction window When introduced into the plasma generation chamber, the microwave introduced into the plasma generation chamber decomposes the Ar, H ₂ and N ₂ gases supplied into the plasma generation chamber to generate plasma. When the generated plasma is introduced into the reaction chamber by the divergent magnetic field formed by the exciting coil,
The metal-based gas reacts with N _{2 and the} like, metal nitride is supplied to the surface of the sample placed in the reaction chamber, and a metal nitride film is formed.

As a reaction mechanism for forming the metal nitride film, the following reaction formula is considered.

2TiCl ₄ + N ₂ + 4H ₂ → 2TiN + 8HCl ↑ To completely decompose TiCl ₄ into Ti + Cl, 400 kc
It requires a very high energy of al mol ^-1 or more.

In the method according to the invention, plasma CVD, in particular electron cyclotron resonance excitation (ECR) plasma CV
High-energy electrons are generated by causing a resonance phenomenon such as D, and the decomposition / reduction reaction is promoted by the collision of these electrons.

Therefore, the metal nitride film is formed on the sample surface without raising the sample temperature to a high temperature of 900 to 1000 ° C.

Ar is introduced to stabilize the plasma discharge, and RF is applied to the microwave introduction window to prevent the conductive film from adhering to the window. Sputtering of the conductive film at this time is performed. Ar also acts as a gas.

In the method of forming a thin film according to the present invention, the generated plasma is supplied to the sample with good directivity, and therefore a metal nitride film as shown in FIG. 9A is formed at the contact portion. .. Therefore, in the next step, the contact hole 35
Voids do not occur even when a wiring material such as W or Al is embedded in the portion, and the filling is performed as shown in FIG. 9B, and the wiring is flattened.

[0027]

[Preferred Embodiments and Comparative Examples] (Embodiment 1) In this embodiment, the case where a thin film of TiN is formed on a sample having holes with different aspect ratios on its surface by using the plasma CVD method will be described in detail.

FIG. 1 is a sectional view schematically showing a plasma CVD apparatus used in the method of forming a thin film according to this embodiment.

The plasma CVD apparatus comprises an apparatus main body 3 consisting of a plasma generation chamber 1 and a reaction chamber 2, and an exciting coil 4 arranged around the plasma generation chamber 1 and connected to a DC power source (not shown). And a waveguide 5 for introducing microwaves oscillated from a microwave oscillator (not shown) into the plasma generation chamber 1. Reference numeral 6 is a microwave introduction window formed of quartz glass or the like, 7 is a high frequency generation source for applying a high frequency (RF) power source to the microwave introduction window, and 8 is a sample table on which a sample 9 is placed. ..

The plasma generating chamber 1 is formed in a substantially cylindrical shape, and a first hole 10 for introducing a microwave is formed in a substantially central portion of an upper wall of the plasma generating chamber 1. A reaction chamber 2 having a larger diameter than the plasma generation chamber 1 is integrally formed below the plasma generation chamber 1. Further, the reaction chamber 2 and the plasma generation chamber 1 are partitioned by a partition plate 11, and a second hole (plasma extraction window) 12 is formed at a substantially central portion of the partition plate 11.

Further, a first introducing pipe 13 is connected to the side wall of the reaction chamber 2, and an exhaust pipe 14 communicating with an exhaust system (not shown) is connected to the bottom of the reaction chamber 2. In addition, the upper wall of the plasma generation chamber 1 has a second introduction pipe 15
Are connected.

The high frequency generator 7 is composed of a high frequency oscillator 16 and a matching box 17, and is connected to the microwave introduction window 6 through a plate electrode 18 sandwiched between the microwave introduction window 6 and the waveguide 5. A high frequency (RF) is applied.

An RF high frequency oscillator 21 for applying an RF high frequency to the sample 9 is connected to the sample table 8 via a matching box 20. This RF high frequency oscillator 2
By applying a predetermined RF high frequency to the sample 9 according to No. 1 and performing the above-described thin film forming method, a bias voltage applied to the sample 9 can form a thin film with good step coverage even when the aspect ratio is high. it can.

Further, the sample 9 is heated by a predetermined heater or the like,
If the temperature of the sample 9 is kept at a predetermined value, for example, 200 to 600 ° C., crystallization of the formed thin film is promoted, and the thin film has good electric conductivity.

When DC power is supplied to the exciting coil 4, a predetermined magnetic field is generated in the plasma generating chamber 1. As a result, the angular frequency ω of the microwave introduced into the plasma generation chamber 1 from the microwave oscillator and the angular frequency ω of the electron cyclotron are
It is also possible to form a magnetic field such that _c and _c become equal in the plasma generation chamber 1 to cause electrons to perform resonance motion. The condition for causing this resonance, that is, the ECR condition can be easily obtained by solving the classical mechanical equation and is represented by the following equation.

Ω = ω _c = eB / m ... Here, e is an electron charge (= 1.6 × 10 ⁻¹⁹ C), B
Is the magnetic flux density (T), m is the mass of the electron (= 9.1 × 10
^-31 kg) respectively.

The angular frequency ω of the microwave is set to 2.45 GHz in this embodiment, and the magnetic flux density B satisfying the ECR condition is set to 8.75 × 10 ^-2 T from the above equation.

To form a thin film using the above apparatus, first, the exhaust system is operated to reduce the pressure inside the apparatus main body 3 to a pressure of 1 × 10 ^-6 Torr or less, and then TiCl ₄ is adjusted to ₅ to 15 SCCM. While supplying into the reaction chamber 2 from the first introduction pipe 13 at a flow rate,
Ar43SCCM, N ₂ 15SCCM and H ₂ 50SCCM were supplied into the plasma generation chamber 1 through the second introduction pipe 15. After that, the inside of the apparatus main body 3 was set to a predetermined pressure, for example, 2 × 10 ⁻³ Torr.

Further, the high-frequency generator 7 was energized to apply a voltage to the microwave introducing window 6 to prevent the TiN thin film from adhering to the microwave introducing window 6 due to the RF sputtering effect.

On the other hand, a microwave having an output of 800 W is introduced from the microwave oscillator into the plasma generation chamber 1 through the waveguide 5, and a DC power source is connected to the exciting coil 4 to generate a magnetic field in the plasma generation chamber 1. Caused. Then, in the plasma generation chamber 1, high-energy electrons collide with the source gas,
This raw material gas was decomposed and ionized to generate plasma.

Next, this plasma passes through the second hole 12, is accelerated in the direction of arrow A in the figure by the divergent magnetic field, is guided into the reaction chamber 2, and is placed on the sample stage 8 with an aspect ratio of 0.2. On the surface of the sample 9 with a hole of ~ 1.0
A thin film of iN was formed.

FIG. 3 shows the relationship between the TiCl ₄ gas flow rate, the film formation rate and the specific resistance obtained in this example. As is clear from FIG. 3, a film formation rate of 700 Å / min and a specific resistance of 180 μΩcm were obtained at a TiCl ₄ gas flow rate of 10 SCCM.

(Embodiment 2) FIG. 2 is a sectional view showing another plasma CVD apparatus used in the method for forming a TiN thin film according to the present invention.

The difference in structure between this plasma device and the plasma device in the first embodiment is only that the first introducing pipe 13 connected to the side wall of the reaction chamber 2 is not provided, and other structures are the same. Since it is the same as the plasma device in the first embodiment, detailed description thereof will be omitted.

In order to form a thin film using the plasma apparatus, first, Ar, H ₂ , N ₂ gas and TiCl ₄ which is a metallic gas are introduced into the second introduction pipe 15 connected to the plasma generation chamber 1.
Introduce gas.

The plasma gas formed by the action of the microwave introduced into the plasma generation chamber 1 through the microwaveguide 5 and the magnetic field of the exciting coil 4 is excited by the exciting coil 4.
It is introduced into the reaction chamber 2 by the divergent magnetic field formed by. Then, the plasma gas is supplied to the surface of the sample 9 and T
An iN film is formed on the surface of the sample 9.

In this embodiment, the flow rate of Ar gas is set to 4
3SCCM, N ₂ gas flow rate is 15 SCCM, H ₂ gas flow rate is 50
Set the flow rate of SCCM and TiCl ₄ gas to 10 SCCM,
The temperature of Sample 9 was set to 600 ° C.

Also in this embodiment, TiCl ₄ shown in FIG. 3 is used.
A film forming rate and a specific resistance value almost equal to those of 10 SCCM were obtained.

FIG. 4 compares the results of Examples 1 and 2 and the experimental results disclosed in Japanese Patent Application Laid-Open No. 3072/1990 as a conventional technique with the aspect ratio and the hole bottom / outer surface film forming rate. The relationship was shown. It can be seen from FIG. 4 that the hole bottom / outer surface portion film formation rate is excellent at high aspect ratios.

(Embodiment 3) Next, an insulating film of SiO ₂ is formed on a P-type Si substrate, a contact hole is formed in this insulating film, and a contact hole is formed by using this as a sample and using the apparatus shown in FIG. A TiN thin film was formed on the inner surface of the hole.

First, the exhaust system is operated to move the inside of the apparatus main body 1 to 1
The pressure was reduced to × 10 ^-6 Torr, and then TiCl ₄ 10 SCCM was supplied into the reaction chamber 2 through the first introduction pipe 13, while A
r: 43 SCCM, H ₂ : 50 SCCM, N ₂ : 15 SCCM are supplied into the plasma generation chamber 1 through the second introduction pipe 15. Under these conditions, the gas pressure inside the apparatus was changed to examine the situation of TiN film formation, especially the situation of TiN film deposition on the inner surface of the contact hole. As a result, a good deposition condition was shown at 2.0 mTorr or less, but deposition failure occurred at a gas pressure higher than this. FIG. 5 is a diagram based on an SEM scanning electron microscope photograph in which a TiN film is actually deposited on the inner surface of a contact hole having an aspect ratio of 2. The processing conditions at this time are as follows: gas pressure 1.3 mTorr, microwave power 2.8 kw, substrate temperature 550 ° C., TiCl ₄ : 10 SCCM, H ₂ : 50 SCCM, N ₂ : 1.
It was 5 SCCM and Ar: 43 SCCM.

From FIG. 5, it can be seen that the TiN film 33 is deposited on the side and bottom of the contact hole 35.
The film thickness deposited on the bottom is about 500 to 600Å, the film thickness on the side wall is 200 to 300Å, while the film thickness on the insulating film is 100.
It was 0Å. That is, the film formation amount at the bottom of the contact hole 35 could exceed 50% of the substrate surface film formation amount. As a comparative example, the pressure in the device body 3 was 3 mTorr, 5
SE when mTorr and other conditions are the same
Figures based on the M photograph are shown in FIGS. 6 and 7. Depending on these conditions, a sufficient deposition state is not shown.

(Example 4) The figure based on the SEM photograph of FIG. 8 shows a pressure of 0.7 mTorr, TiCl ₄ : 5 SCCM, Ar: H ₂ : 50.
SCCM, N ₂ : 15SCCM, microwave 2.8kw, substrate temperature 5
The film-forming state when formed under the condition of 50 ° C. is shown. As is clear from this figure, the film formation amount at the bottom of the contact hole 35 was 70%, which was a very excellent value with respect to the film formation amount on the substrate surface.

As is apparent from Examples 3 and 4, the pressure inside the apparatus main body 3 is 2.0 mTorr, preferably 1.3 mTorr.
It is better to set it below rr.

In the plasma CVD method of the present invention, the gas is activated by making it into plasma, and the activated gas is guided onto the sample according to the divergence of magnetic force lines, and the gas is activated on the sample.
It forms TiN. Therefore, the activated gas molecules are directed by the divergent magnetic field, so that they have directivity and are irradiated almost perpendicularly to the sample, and the surface of the insulator around the contact hole and the TiN thin film at the bottom of the contact hole are thick. However, the side wall of the contact hole becomes thinner. Therefore, the TiN film has a good barrier property because it is thick at the bottom of the contact hole, while the side wall of the contact hole is thin. Therefore, the diameter of the contact hole is not so small and the aspect ratio after TiN film formation is not so high. Therefore, the probability of void formation in the subsequent step of burying the electrode material with Al and tungsten is reduced, and highly reliable wiring is possible.

FIG. 9 (a) shows how the TiN film 33 is attached in the vicinity of the contact hole 35 by the plasma CVD method of the present invention, and FIG. 9 (b) shows the case where the TiN film 33 is then filled with tungsten. Further, Table 1 shows data of film thickness formed by each film formation.

[0057]

[Table 1]

As described above, in the ECR plasma CVD method, a thick film is formed on the bottom, and no void is observed when tungsten is embedded in the next step.

(Embodiment 5) The curve shown by (●) in FIG. 10 is the resistivity of a thin film and the temperature of the substrate produced under the microwave power of 1 kw and the gas pressure of 1.3 mTorr in the above CVD apparatus. Shows the relationship. That is, the substrate temperature is 450 ° C
In the above, the specific resistance value of the TiN film produced is compared with 523 μΩcm by the LPCVD method described in the prior art,
The value was extremely small at 200 μΩcm or less, and a very good value was obtained in terms of the function of electrically connecting the diffusion layer portion of the semiconductor device and the electrode portion of the metal wiring. On the other hand, when the substrate temperature is 450 ° C. or lower, the specific resistance value of the TiN film to be produced increases sharply and cannot be used.

The curve indicated by ◯ in FIG. 10 shows the relationship between the deposition rate of the TiN film and the substrate temperature under microwave power of 1 kw and gas pressure of 1.3 mTorr.
It can be understood from this curve that there is no particular correlation between the two. Therefore, the temperature of the substrate should be 450 ° C. or higher, preferably 550 ° C.

Example 6 FIG. 11 shows the relationship between the microwave power and the deposition rate (∘) and the relationship between the microwave power and the specific resistance (). From FIG. 11, it was confirmed that a specific resistance of 200 μΩcm or less can be obtained at a microwave power of 1 kw or more and 100 μΩcm or less at a microwave power of 2 kw or more.

These results show that the method of using the thermal reaction energy and the plasma energy of the present invention in combination is far superior to the specific resistance of 525 μΩcm by the LPCVD method utilizing only the thermal reaction of the prior art, and that a practical level can be realized. Is shown.

Example 7 Next, FIGS. 12 to 15 show drawings based on SEM photographs of the TiN film deposited in the contact hole portion. The processing conditions at this time were the same as the processing conditions shown in FIG. 5 except that the microwave power was 1 kw and the flow rate of TiCl ₄ was changed. TiN deposited from this Figure 12
It was confirmed that the film did not have a columnar structure but a uniform microstructure. Therefore, it was expected that the barrier properties would be good.

FIG. 13 shows TiCl ₄ : 5SCCM, and FIG. 14 shows TiCl ₄ .
₄ : 15SCCM, FIG. 15 shows the case of TiCl ₄ : 20SCCM, respectively, and shows the change of the structure of the TiN film when the flow rate of TiCl ₄ was changed. 14 and 15, the TiN film has a columnar structure, and it can be seen that the TiN film of FIG. 13 has a uniform fine structure like that of FIG.

When the microwave power is constant, the TiN film tends to have a columnar structure when the flow rate of TiCl ₄ is increased as described above, but when the microwave power is increased,
Even if the flow rate of TiCl ₄ is high, the TiN film can have a uniform microstructure.

Next, Table 2 shows the results of investigation of the relationship between the microwave power, the flow rate of TiCl ₄ and the structure of the TiN film.

[0067]

[Table 2]

From this result, even if the flow rate of TiCl ₄ is increased,
It has been found that if the microwave power is increased correspondingly, the generation of the columnar structure can be prevented.

(Example 8) FIG. 16 shows an experimental result showing that the barrier property is excellent. This Figure 16 shows A
It shows that the curves of l and Ti do not spread laterally.

In FIG. 16, a TiN film having a thickness of 1000 Å is formed on a Si substrate, and Al is further vapor-deposited on the SiN film without heat treatment.
30 minutes at 500 ℃, 30 minutes at 600 ℃, 30 minutes at 650 ℃
Heat treatment for 4 minutes and RBS as 4 samples
It is a graph which shows the result measured by (Rutherford backscattering spectroscopy). RBS is a method of irradiating a substrate with He atoms having a constant energy and examining the element distribution in the film thickness direction in the film from the energy of reflected He. The energy loss of He that collides with each element is determined by the element (atomic weight), and the lighter the element, the more it goes to the left. Therefore, the film structure is Al / TiN / Si, but Si,
A peak appears in the order of Ti and Al. Further, the width of each peak means that it corresponds to the film thickness, and when it spreads out, it means that it diffuses. (Si is a substrate, so the width is wide,
Only one end can be seen). As is clear from FIG. 16, this peak hardly changes even after the heat treatment, and shows a high barrier property (diffusion preventing effect) even after the heat treatment at 650 ° C. for 30 minutes.

The figure in the upper frame shows that in the film structure, Al / TiN / Si, He is irradiated from the direction of Al and partially scattered backward.
It shows that the yield of ions was measured.

In the next step after forming the TiN film, wiring of W alloy or Al or Al alloy such as Al--Si--Cu is provided on the TiN film. However, if chlorine remains in the TiN film. If so, the wiring such as Al is strongly corroded by chlorine. In some cases, AlCl ₃ which is an insulating material is generated, and corrosion of the Al wiring is observable with the naked eye. Therefore, it is an essential step to remove chlorine from the TiN film as much as possible.

FIG. 17 and FIG. 18 are graphs of T prepared at microwave powers of 1 kw and 2.8 kw under the processing conditions of the embodiment of the present invention.
The EDX (energy dispersive X-ray analyzer) spectrum of the iN film is shown. At 1 kW, a chlorine Cl peak was confirmed, but at 2.8 kW, no chlorine Cl peak was confirmed.

As described above, chlorine Cl can be prevented from being mixed by increasing the microwave power, but it can also be reduced by performing H ₂ plasma treatment after forming the TiN film.

FIG. 19 shows an analysis by SIMS (Secondary Ion Mass Spectroscopy) in the depth direction (toward the Si substrate at right angles to the TiN film) from the surface of the sample subjected to H ₂ plasma treatment after forming the TiN film. The results are shown.

This SIMS is for irradiating oxygen ions to dig a film in the depth direction and measuring the distribution of elements or molecules (TiN etc.) existing in the depth direction. That is, by irradiating high-energy oxygen ions, the substance in the film is knocked out, and the ions (2
The signal intensity of the secondary ion) is measured in the depth direction.

The left side (on the vertical axis) of FIG. 19 is the surface side of the TiN film, which means that the depth to be dug increases toward the right side. Chlorine is reduced at the surface of the film, which is due to the H ₂ plasma treatment after TiN formation.

By performing the H ₂ plasma treatment in this way, the chlorine concentration on the surface of the TiN film can be reduced, and the corrosion of Al wiring or the like due to chlorine can be prevented.

Incidentally, the H ₂ plasma treatment means that at the end of the TiN film forming treatment, the supply of Ti compound gas such as TiCl ₄ and N ₂ gas is stopped and Ar gas and H ₂ gas are caused to flow to generate plasma. It is to maintain a good condition.

Next, T prepared by the method according to the embodiment
An X-ray diffraction pattern diagram of the iN film is shown in FIG. This pattern shows that the TiN crystal is (10) on the Si substrate (111).
It indicates that the orientation is only in the 0) direction. The processing conditions are microwave power of 1 kw, substrate temperature of 550 ° C., and N ₂ , H ₂ , and Ar gas flow rates of 15 SCCM, 50 SCCM, and 43 SCCM, respectively.
Met.

The (100) oriented film has excellent barrier properties, and TiN formed by the method according to the embodiment as described above.
It is speculated that the extremely strong (100) orientation of the film is due to the directivity of the plasma.

[0082]

As is clear from the above description, according to the thin film forming method of the present invention, it is possible to form a metal nitride film having excellent step coverage, and the LSI device is highly integrated. Even if the aspect ratio of the contact hole formed in the insulating layer is large, a thin film having sufficient barrier properties can be formed in the contact hole portion.

Moreover, the film thickness of the thin film formed on the side wall of the contact hole can be made smaller than the film thickness of the thin film formed on the bottom of the contact hole, and the thin film is formed while ensuring the barrier property at the bottom of the contact hole. It is possible to suppress an increase in the aspect ratio of the subsequent contact hole. Therefore, voids are not generated in the contact holes even at the time of embedding the wiring material in the subsequent step, and it is possible to prevent the disconnection of the wiring and improve the reliability of the LSI device.

Further, it is possible to form a thin film at a low temperature that does not adversely affect the production of an LSI device and to produce a more reliable LSI device without generating particles such as yellow powder. Is possible.

[Brief description of drawings]

FIG. 1 is a cross-sectional view schematically showing an example of a thin film forming apparatus used in a thin film forming method according to the present invention.

FIG. 2 is a sectional view schematically showing another example of the thin film forming apparatus.

FIG. 3 is a graph showing the relationship between the flow rate of TiCl ₄ gas, the film formation rate, and the specific resistance.

FIG. 4 is a graph showing the relationship between the hole bottom / outer surface portion film formation rate with respect to the aspect ratio of a contact hole.

FIG. 5 is a cross-sectional view showing a state of a TiN film formed on the inner surface of the contact hole at TiCl ₄ : 10 SCCM and gas pressure of 1.3 mTorr.

FIG. 6 is a cross-sectional view showing the state of the TiN film formed on the inner surface of the contact hole at TiCl ₄ : 10 SCCM and gas pressure of 3 mTorr.

FIG. 7 is a cross-sectional view showing a state of a TiN film formed on the inner surface of the contact hole at TiCl ₄ : 10 SCCM and gas pressure of 5 mTorr.

FIG. 8 is a cross-sectional view showing the state of the TiN film formed on the inner surface of the contact hole at TiCl ₄ : 5 SCCM and gas pressure: 0.7 mTorr.

9A is a sectional view showing a state in which a TiN film is formed in a contact hole portion by the method according to the embodiment, FIG. 9B.
FIG. 6 is a cross-sectional view showing a state in which W (tungsten) is then embedded in the contact hole portion.

FIG. 10: TiN formed using a plasma CVD apparatus
3 is a graph showing the relationship between the specific resistance of the film and the substrate temperature, and the relationship between the deposition rate of the TiN film and the substrate temperature.

FIG. 11: TiN formed using a plasma CVD device
3 is a graph showing the relationship between the specific resistance of the film and the microwave power, and the relationship between the deposition rate of the TiN film and the microwave power.

FIG. 12 is a cross-sectional view showing a growth state of a TiN film deposited on a Si substrate at TiCl ₄ : 10 SCCM.

FIG. 13: Deposited on Si substrate at TiCl ₄ : 5 SCCM
FIG. 6 is a cross-sectional view showing a growth state of a TiN film.

FIG. 14 is a cross-sectional view showing a growth state of a TiN film deposited on a Si substrate when TiCl ₄ : 15 SCCM is used.

FIG. 15 is a cross-sectional view showing a growth state of a TiN film deposited on a Si substrate when TiCl ₄ : 20 SCCM is used.

FIG. 16 is a diagram showing RBS measurement results of a sample in which a TiN film is formed on a Si substrate and Al is vapor-deposited thereon.

FIG. 17 is a diagram showing an EDX spectrum of a TiN film formed on the inner surface of a contact hole with a microwave power of 1 kw.

FIG. 18 is a diagram showing an EDX spectrum of a TiN film formed on the inner surface of a contact hole with a microwave power of 2.8 kw.

FIG. 19 is a diagram showing SIMS-based analysis results of the surface of a Si substrate on which a TiN film is formed.

FIG. 20 is an X-ray diffraction diagram of a TiN film.

FIG. 21 is a sectional view schematically showing a reactive sputtering device.

FIG. 22A is a sectional view showing a state of a TiN film formed in a contact hole portion by a reactive sputtering method,
(B) is a sectional view showing a state in which W (tungsten) is embedded thereafter.

FIG. 23 is a sectional view schematically showing an apparatus used in the LPCVD method.

24A is a sectional view showing a state of a TiN film formed in a contact hole portion by an LPCVD method, and FIG. 24B is a sectional view showing a state where W (tungsten) is embedded thereafter.

[Explanation of symbols]

 1 Plasma generation chamber 2 Reaction chamber 4 Excitation coil 6 Microwave introduction window 8 Sample stage 9 Sample 35 Contact hole 37 Insulating film 38 Si substrate

Claims (6)

[Claims] 1. A plasma is generated in a plasma generation chamber by the action of an electric field generated by microwaves and a magnetic field generated by an exciting coil arranged around the plasma, and the generated plasma is introduced into a reaction chamber and placed on a sample table. In the method of forming a thin film on the sample, while introducing Ar, H ₂ and N ₂ gas into the plasma generation chamber, a metal nitride film on the sample by introducing a metal-based gas into the reaction chamber. A method for forming a thin film, which comprises forming the thin film. 2. A plasma is generated in a plasma generation chamber by the action of an electric field generated by microwaves and a magnetic field generated by an exciting coil arranged around the plasma, and the generated plasma is introduced into a reaction chamber and placed on a sample stage. In the method for forming a thin film on a sample, a thin film characterized by forming a metal nitride film on the sample by introducing Ar, H ₂ , N ₂ gas and the metal-based gas into the plasma generation chamber. Forming method. 3. A substrate for forming a semiconductor device in which an insulating film is formed on a substrate and a contact hole is formed in the insulating film, titanium tetrachloride gas is used as a metal-based gas, and the pressure in the reaction chamber is 2.0 mTorr. The method for forming a thin film according to claim 1 or 2, wherein a Ti nitride film is formed in the contact hole under the condition that the temperature of the sample substrate is 450 ° C or higher. 4. A semiconductor device, wherein the thickness of the Ti nitride film at the bottom of the contact hole is thicker than the thickness of the Ti nitride film at the sidewall of the contact hole. 5. The method for forming a thin film according to claim 1, wherein the film is formed while applying RF to the microwave introduction window. 6. The method for forming a thin film according to claim 1, 2, 3 or 6, wherein H ₂ plasma treatment is performed after forming the Ti nitride film.