JPH08188877A - Formation of titanium nitride film and device therefor - Google Patents

Abstract

PURPOSE: To lower the Cl, content in a TiN film and to form a film on the bottom of a contact hole with good step coverage by improving the magnetic field distribution on a wafer. CONSTITUTION: The plasma of a gas contg. TiCl4 , H2 and N2 is produced by utilizing electron cyclotron resonance. The distribution of the magnetic field vertical to a sample carrying face in the radial direction on the carrying face is allowed to have the maximum value outside a sample placed on the face. The sample 31 placed on a sample holder 14 is irradiated with the plasma produced by utilizing a magnetic field with the maximum value >=140 Gauss higher than that on the peripheral part of the sample 31 to form a TiN film on the sample.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a TiN film forming method mainly used as a barrier film in manufacturing a semiconductor device, and a plasma processing apparatus used for forming and etching a thin film.

[0002]

2. Description of the Related Art With the miniaturization and high integration of semiconductor devices,
A diffusion prevention film (hereinafter referred to as a barrier film) is used for the contact hole and the via hole.

The barrier film is W (tungsten) or Al formed in a contact hole or a via hole.
The purpose is to prevent the (aluminum) plug (electrode) from reacting with the underlayer or diffusing into the underlayer. Since the TiN film is a conductive film and is chemically stable, it is used as a barrier film.

The ECR plasma CVD method utilizing electron cyclotron resonance (ECR) is used for forming this TiN film. This is because the ECR plasma has excellent directivity of the plasma flow and can form a film with good step coverage even on the bottom of a hole having a high aspect ratio.

FIG. 4 is a schematic vertical sectional view of a conventional ECR plasma CVD apparatus. This ECR plasma CVD apparatus is mainly composed of an apparatus main body, an ECR magnetic field generating means, and a microwave introducing means. The device body is a plasma generation chamber 4
And a reaction chamber 10. As ECR magnetic field generation means,
An ECR magnetic field generating coil 9 is provided around the plasma generating chamber 4. A DC power source (not shown) is connected to the ECR magnetic field generating coil 9. The microwave introduction means includes a waveguide 1 for introducing microwaves oscillated from a microwave oscillator (not shown) into the plasma generation chamber 4.

The plasma generating chamber 4 is formed in a substantially cylindrical shape. A microwave introduction port 4a is opened in the center of the upper wall of the plasma generation chamber 4, and the microwave introduction window 3 made of quartz is used.
It is vacuum sealed with. The microwave introduction port 4a is connected to the waveguide 1. An electrode 2 to which a high-frequency oscillator (not shown) is connected is provided near the microwave introduction window 3. This is for preventing the microwave from being blocked here by forming a conductive film on the surface of the microwave introduction window 3 on the side of the plasma generation chamber when forming a conductive film such as a TiN film. That is, this conductive film is sputtered by applying a high frequency to the microwave introduction window 3 during plasma generation. A first gas introduction pipe 5 is connected to the upper wall of the plasma generation chamber 4. A cooling water passage 6 is provided on the wall of the plasma generation chamber 7.

The reaction chamber 10 has a larger diameter than the plasma generation chamber 4 and is provided below the plasma generation chamber 4. The reaction chamber 10 and the plasma generation chamber 4 are partitioned by a partition plate 8 and communicate with each other through a plasma outlet 8a opened in the partition plate 8. Reaction chamber 10
The inside of the wafer 31 faces the plasma outlet 8a.
A sample table 14 on which a sample such as the above is placed is provided. The sample stage 14 is internally provided with a heater (not shown) for maintaining the wafer 31 at a predetermined high temperature. Also, the reaction chamber 10
A second gas introduction pipe 11 is connected to the side wall of the reaction chamber 1
Exhaust pipe 1 connected to an exhaust system (not shown) at the bottom of 0
2 is connected.

A plasma generation chamber 4 is provided below the sample table 14.
A magnetic field generating coil 21 for controlling a plasma flow is provided in order to efficiently irradiate the wafer 31 with the plasma generated in (3).

This plasma flow control magnetic field generating coil 21
Is an outer coil 21a connected to a DC power source,
The inner coil 21b and the pure iron yokes 21c and 21d,
21e.

Next, a method of forming a TiN film by using this ECR plasma CVD apparatus will be described.

The plasma generation chamber 4 and the reaction chamber 10 are exhausted to a predetermined pressure. N ₂ , H from the first gas introduction pipe 5
₂ and Ar gas are supplied into the plasma generation chamber 4, and TiCl ₄ is supplied into the reaction chamber 10 from the second gas introduction pipe 11 to a predetermined pressure. A direct current is passed through the ECR magnetic field generating coil 9 to form a magnetic field required for ECR in the plasma generation chamber. The magnetic field required for ECR is 875 Gauss when the microwave frequency is 2.45 GHz. Plasma generation chamber 4 through waveguide 1 and microwave introduction window 3
Microwave is introduced into the inside to generate plasma. At this time, a high frequency is applied to the electrode 2 to prevent the TiN film from adhering to the microwave introduction window 3.

The generated plasma is the plasma outlet 8a.
Further, the wafer 31 introduced into the reaction chamber 10 and placed on the sample table 14 is irradiated with the wafer 31. The wafer 31 is heated to a predetermined temperature in advance, and a TiN film is formed on this wafer 31. At this time, the plasma flow is efficiently irradiated onto the wafer 31 by the plasma flow control magnetic field generating coil 21. The control of the plasma flow by the magnetic field generating coil 21 for controlling the plasma flow is performed as follows. A DC current is applied to the outer coil 21a in the same direction as the ECR magnetic field generating coil 9 to form a mirror magnetic field, and a DC current is applied to the inner coil 21b in the opposite direction to the ECR magnetic field generating coil 9 to form a cusp magnetic field. As a result, the central portion of the plasma flow is widened by the cusp magnetic field, and the outer portion of the plasma flow is confined by the mirror magnetic field, and the plasma flow is uniformized and irradiated onto the wafer 31.

[0013]

However, in the TiN film forming method using the above-described conventional ECR plasma device, the content of Cl (chlorine) in the TiN film at the periphery of the wafer is high. There was a problem. If the content of Cl in the TiN film is large, there arises a problem that the resistance of this portion increases and a problem that the Al electrode in contact with the TiN film is corroded.

The present invention has been made to solve the above problems, and an object thereof is to provide a method and apparatus for forming a TiN film having a small Cl content regardless of the center and the periphery of the wafer. I am trying.

[0015]

In order to achieve the above object, a TiN film forming method of the present invention utilizes electron cyclotron resonance to generate a plasma of a gas containing TiCl ₄ , H ₂ and N _2. Then, the sample placed on the sample table is irradiated with the plasma generated by using the magnetic field, and TiN is deposited on the sample.
In a TiN film forming method for forming a film, a radial distribution of a magnetic field perpendicular to the sample mounting surface on the sample mounting surface has a maximum value outside the mounted sample, and It is characterized in that the maximum value is 140 Gauss or more larger than the value of the peripheral portion of the mounted sample.

Further, as shown in FIG. 1, the plasma processing apparatus used in the TiN film forming method is in communication with the plasma generation chamber 4 and the plasma generation chamber 4, and the sample table 14 is provided therein. The reaction chamber 10, the plasma generation chamber 4 or a means for introducing a gas into the reaction chamber 10, a means for introducing a microwave into the plasma generation chamber 4, and an ECR magnetic field generation coil 9 arranged around the plasma chamber. And a magnetic field generating coil 21 for controlling the plasma flow arranged below the sample table 14.
And a yoke ring 22 arranged near the outer periphery of the sample table.
And characterized in that:

The yoke ring 22 is made of a magnetic material such as pure iron, and serves to change the magnetic field distribution on the sample table 14.

[0018]

The function of TiCl ₄ is H (hydrogen) according to the following reaction formula.
Is reduced in plasma by the method to form a TiN film on the sample.

2TiCl ₄ + N ₂ + 4H ₂ = 2TiN + 8HCl However, if H is not sufficiently present, TiCl ₄ is not sufficiently reduced, and C is contained in the TiN film formed on the sample.
l will be included.

In the plasma of TiCl ₄ , N ₂ , H ₂ and Ar gas, H, which has an important role in the reaction, is an atom lighter than other gas molecules. Therefore, in the conventional magnetic field distribution, the ratio of H ions in the periphery is smaller than that in the center,
As a result, the Cl content in the TiN film at the peripheral portion was increased.

Therefore, the sample in which the distribution of the magnetic field in the direction perpendicular to the sample mounting surface in the radial direction on the wafer mounting surface has a maximum value outside the mounted sample, and this maximum value is mounted The magnetic field distribution is 140 Gauss or more larger than the value of the peripheral portion of. As a result, the effect of confining the plasma can be sufficiently enhanced as compared with the conventional case, H can be sufficiently supplied to the peripheral portion of the sample, and the Cl content in the TiN film at the peripheral portion of the sample can be reduced.

Further, since the effect of confining the plasma is enhanced by this magnetic field distribution as compared with the conventional case, the step coverage on the bottom of the hole can be improved.

Further, by providing the yoke ring in the vicinity of the outer periphery of the sample table, the plasma confinement effect can be easily enhanced without significantly changing the overall structure of the sample table.

The structure in which the yoke ring is provided in the vicinity of the outer peripheral portion of the sample table can easily enhance the effect of controlling the plasma flow, and thus can be applied to the etching apparatus.

The yoke ring does not necessarily have to be annular and integrated, and a plurality of yokes may be arranged in the vicinity of the outer periphery of the sample stage so as to surround the sample stage.

[0026]

EXAMPLES Examples of the TiN film forming method according to the present invention will be described below.

FIG. 1 is a schematic sectional view showing an embodiment of the ECR plasma CVD apparatus used in the TiN film forming method according to the present invention. A yoke ring 22 is provided on the outer periphery of the sample table 14.
Is provided. The yoke ring 22 is made by processing pure iron into a ring shape and coating the surface with a Ni—Cr alloy. The other parts are the same as those of the conventional ECR plasma CVD apparatus shown in FIG. The frequency of the microwave is 2.45 GHz.

Magnetic field distributions were measured for the apparatus of the present invention (having a yoke ring) and the conventional apparatus shown in FIG. 4 (having no yoke ring). The current of the ECR magnetic field generation coil 9 was set to 25 A, and the coil current of the plasma flow control coil 21 was set to the following two conditions.

Condition 1: Outer coil 21a (15A), Inner coil 21b (0A) Condition 2: Outer coil 21a (3A), Inner coil 21
b (−5 A) In addition, + (plus) of the coil current is a current in the same direction as the current of the ECR magnetic field generating coil 9, and − (minus) of the coil current is the reverse of the current of the ECR magnetic field generating coil 9. This is the case for the current in the direction of.

FIG. 2 shows the measurement results of the magnetic field distribution in the radial direction on the sample mounting surface of the apparatus of the present invention and the conventional apparatus. The measurement result of the device of the present invention is shown as an example of the present invention and the measurement result of the conventional device is shown as a conventional example. The horizontal axis represents the distance (mm) from the center of the sample mounting surface, and the vertical axis represents the magnetic field strength (Gauss) in the direction perpendicular to the sample mounting surface. Assuming an 8-inch wafer as a sample, the position of the peripheral edge of the wafer is set to 9
Evaluation was made at a position of 0 mm.

The case of condition 1 will be described. In the conventional example, the wafer peripheral portion (90 mm) has 320 Gauss, and the maximum value of the magnetic field is 350 Gauss (130 mm). On the other hand, in the example of the present invention, 300 Gauss at the wafer peripheral portion (90 mm),
The maximum value of the magnetic field was 630 Gauss (150 mm).
That is, the difference in magnetic field strength was 30 Gauss in the conventional example, while it was as large as 330 Gauss in the example of the present invention. The case of condition 2 will be described. In the conventional example, the wafer peripheral edge (90 mm) is 90 Gauss, and the maximum value of the magnetic field is 1.
It was 30 Gauss (140 mm). On the other hand, in the example of the present invention, the peripheral portion of the wafer (90 mm) was 80 Gauss, and the maximum value of the magnetic field was 220 Gauss (150 mm). That is,
Even in the case of condition 2, the difference in magnetic field strength is 40 Gaus in the conventional example.
However, in the example of the present invention, it is as large as 140 Gauss. By using the yoke ring 22,
It was possible to increase the maximum value of the magnetic field outside the wafer and form a magnetic field barrier of 140 Gauss or more between it and the peripheral portion of the wafer.

Device of the present invention (with yoke ring)
With respect to the conventional device (without the yoke ring), a TiN film was formed under the magnetic field distributions of the conditions 1 and 2 described above, and the content of Cl at the position 90 mm from the center of the wafer was adjusted. evaluated. SIMS (secondary ion mass spectrometry) was used for evaluation of the content of Cl. Similarly, SEM
Using a (scanning electron microscope), the step coverage was evaluated. This evaluation was performed at three points: the center of the wafer, a position 60 mm from the center, and a position 90 mm from the center.

Table 1 shows the film forming conditions of the TiN film evaluated in this way. The diameter is 0.75 μm and the depth is 0.
The film was formed on an 8-inch wafer having a contact hole near 95 μm.

Table 2 shows the measurement results of the Cl content. Here, the measurement result of the device of the present invention is shown as an example of the present invention, and the measurement result of the conventional device is shown as a conventional example. By improving the magnetic field distribution using the yoke coil 22, in the case of the condition 1, the content of Cl is changed from 2.0 atm% to 1.4 atm%.
In the case of condition 2, the content of Cl is 2.0 atm% to 1.5.
It can be seen that it has been reduced to atm%.

Tables 3 (a) to 3 (d) show the results of the state of forming the TiN film in the vicinity of the contact hole. Table 3 (a)
Is the device of the present invention (condition 1), Table 3 (b) is the conventional device (condition 1), Table 3 (c) is the device of the present invention (condition 2), and Table 3 (d) is the conventional device (conditions). This is the result of 2). In the table, d is the diameter of the contact hole, h is the depth of the contact hole, t1 is the film thickness of TiN outside the contact hole, t2 is the minimum film thickness of TiN at the bottom of the contact hole,
t3 is the maximum film thickness of TiN at the bottom of the contact hole. These are shown schematically in FIG. R is the step coverage and was evaluated by t2 / t1. θ is the bottom slope, and tan θ = (t3−t2) / d is satisfied when the TiN film thickness has the minimum value t2 and the maximum value t3 at both ends of the hole bottom. By improving the magnetic field distribution using the yoke coil 22, the step coverage R is 0.31 to 0.51 and the bottom inclination θ is 2.0 ° to 1. I was able to improve to 5 °. In the case of condition 2, the step coverage R is 0.31 to 0.4.
4, it was possible to improve the bottom inclination θ from 1.8 ° to 1.7 °.

[0036]

[Table 1]

[0037]

[Table 2]

[0038]

[Table 3]

[0039]

As described in detail above, Ti according to the present invention
The N film forming method and apparatus can reduce the Cl content in the TiN film by improving the magnetic field distribution on the wafer. Along with that, it is possible to form a film on the bottom of the contact hole with good step coverage.

[Brief description of drawings]

FIG. 1 is a schematic vertical sectional view showing an ECR plasma CVD apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing measurement results of magnetic field distributions on sample mounting surfaces of an example of the present invention and a conventional example.

FIG. 3 is a schematic diagram illustrating d, h, t1, t2, t3, and θ that characterize the film formation state of a TiN film in a contact hole.

FIG. 4 is a schematic vertical sectional view showing a conventional ECR plasma CVD apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Waveguide 2 Electrode 3 Microwave introduction window 4 Plasma generation chamber 4a Microwave introduction port 8a Plasma extraction port 9 ECR magnetic field generation coil 10 Reaction chamber 14 Sample stage 21 Plasma flow control coil 22 Yoke ring

Claims (2)

[Claims] 1. TiC utilizing electron cyclotron resonance
A plasma of a gas containing l ₄ , H ₂ and N ₂ is generated, and the plasma generated by using a magnetic field is applied to a sample placed on a sample stage to form a TiN film on the sample. In the method of forming a TiN film, the radial distribution of the magnetic field in the direction perpendicular to the sample mounting surface has a maximum value outside the mounted sample, and this maximum value The method for forming a TiN film is characterized in that it is larger than the value of the peripheral portion of the prepared sample by 140 Gauss or more. 2. A plasma generation chamber, a reaction chamber in communication with the plasma generation chamber, in which a sample stage is arranged, a means for introducing gas into the plasma generation chamber or the reaction chamber, and a micro-chamber in the plasma generation chamber. A means for introducing a wave, an ECR magnetic field generation coil arranged around the plasma chamber, a plasma flow control magnetic field generation coil arranged below the sample stage, and a magnetic field generation coil disposed near the outer periphery of the sample stage. And a yoke ring.