JPH05179438A - Sputtering device - Google Patents

Abstract

PURPOSE:To enable uniform film formation on a stepped part having a high aspect ratio with satisfactory step coverage and to enable film formation with high efficiency of utilization of a target. CONSTITUTION:In this sputtering device, a target 4 is put in the boundary region between a plasma generating region 2 and a sample arranged region 3. The target 4 has plural holes or is composed of plural tubes so that the regions 2, 3 are allowed to communicate with each other. A means to apply a high-frequency or DC electric field to a sample holder and a mechanism for rotating the sample holder are arranged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for forming a thin film in the manufacture of a semiconductor device, and more particularly to an apparatus for forming a thin film on a semiconductor substrate having an uneven surface, and more specifically, a wiring material and a barrier on the semiconductor substrate. The present invention relates to an apparatus for forming a thin film of metal or insulating material.

[0002]

2. Description of the Related Art With the high integration of LSIs, the device structure has become 3
It is becoming more and more dimensional to use multilayer wiring technology. In this multi-layer wiring technique, a film forming technique on the step portion and a film forming flattening technique are important. In particular, the aspect ratio (depth / width) of the wiring structure is increased with the increase in the degree of integration, and the technology of burying the wiring material in the through holes and contact holes, which are fine and have a large aspect ratio, and the flattening of the interlayer insulating film. Technology is important.

The bias sputtering method is known as one of the embedding technology and planarization technology. FIG. 4 is a schematic vertical sectional view of a conventional parallel plate type bias sputtering apparatus. The filling of the contact hole of Al, which is the wiring material, is performed as follows. The sample S is placed on the sample table 32 in the reaction chamber 31.
The reaction chamber 1 is evacuated to a vacuum by an unillustrated exhaust system, and Ar gas is introduced from the gas introduction system 36 to place an Al target.
A high frequency electric field is applied to 33 by a high frequency power supply 35 to generate plasma, a target 33 is sputtered, and Al is deposited on the sample S.

Since a high frequency electric field is applied to the sample stage 32 by the high frequency power source 34, Ar ions also enter the sample S. Therefore, among the Al atoms attached to the sample S, the Al atoms attached to the portion where the incident angle of the ion is large are re-sputtered, and the film is formed with good step coverage as compared with the case where the high frequency electric field is not applied. The flattening of the insulating film SiO ₂ is performed by using SiO ₂ as the target 33. In this case as well, due to the high-frequency electric field applied to the sample table,
Ar ions are incident on the sample S, and the etching rate of the SiO ₂ film by Ar ions is higher in the inclined portion than in the portion having the surface parallel to the substrate, so that the surface of the SiO ₂ film is flattened.

However, in the parallel plate type device, the aspect ratio (depth / depth /
If the (width) becomes large, there is a problem that the step coverage deteriorates and a void is generated. This is because, since the operating pressure is high, the particles sputtered from the target collide on the way and are obliquely incident on the step. Resputtering due to the high-frequency electric field applied to the sample stage results in insufficient recovery of step coverage.

On the other hand, there has been proposed an ECR bias sputtering apparatus (Japanese Patent Laid-Open No. 61-218134) which utilizes ECR (electron cyclotron resonance) using microwaves. Figure 5
FIG. 4 is a schematic vertical sectional view of a conventional ECR bias sputtering apparatus. It comprises a plasma generation chamber 41 and a sample chamber 42 in which the sample S is arranged, a plasma extraction window 43 is provided between them, and a cylindrical target 44 is arranged around the plasma extraction window. A negative DC power source 50 is connected to the target 44, and a high frequency power source 49 is connected to the sample table on which the sample S is placed.

The operation of this ECR bias sputtering apparatus will be described. First, the plasma generation chamber 41 and the sample chamber 42 are evacuated to a vacuum by an unillustrated exhaust system, and Ar or the like is introduced into the plasma generation chamber 41 through a gas introduction system 47. Excitation coil 46
Thus, a magnetic field required for ECR is formed in the plasma generation chamber 41, and microwaves are introduced through the waveguide 45 to generate plasma in the plasma generation chamber 41. The generated plasma is drawn into the sample chamber 42 by the divergent magnetic field generated by the exciting coil and sputters the cylindrical target 44 on the way. The generated sputtered particles are introduced onto the sample S to form a thin film. The step coverage is improved by applying a high frequency electric field to the sample stage when forming this thin film.

In such an ECR sputtering apparatus,
Compared to the parallel plate type device, it is possible to operate at a lower gas pressure, so the sputtered particles have better directivity, and the aspect ratio (depth / width) is 1 even when burying through holes and contact holes. Even in the above cases, it is possible to form a film with good step coverage. Further, since the plasma generation power and the sputtering power are independent, the number of ions bombarding the target 44 and the plasma energy can be controlled independently, so that the sputtering conditions suitable for the material of the target 44 can be set.

[0009]

However, this conventional ECR bias sputtering apparatus has a problem common to the conventional ECR sputtering apparatus. That is, since the target has a large diameter, sputtered particles that have jumped out of the target often fly out of the sample, so the rate of attachment to the sample is low, and because the surface area is smaller than the size of the target, the utilization efficiency of the target is low. However, since the target is located at the peripheral portion of the sample S, the in-plane uniformity of film formation is also poor. An object of the present invention is to solve such a problem, and it is an object of the present invention to provide an apparatus which is compatible with a high aspect ratio, can form a uniform film, and has high target utilization efficiency.

[0010]

The present inventor has previously used a target having a plurality of holes for communicating the plasma generation region and the sample placement region in the ECR sputtering apparatus, or the plasma generation region and the sample placement region. By constructing the target with multiple cylinders communicating with each other, it was found that the utilization efficiency of the target can be increased, and the directivity and uniformity can be formed at a high film forming speed. And applied for a patent. (Japanese Patent Application No. 3-26
(No. 7237)

Based on this knowledge, the inventors attempted to improve the uniformity and target utilization efficiency, which are the main problems of the ECR bias sputtering apparatus. That is, although this improved target was used in the ECR bias sputtering device, if a high frequency or DC electric field was simply applied to the sample stage of the ECR sputtering device incorporating this improved target,
Since the plasma density distribution on the sample is slightly different depending on whether it is behind the target or not, the result is that the bias potential generated when a high frequency or DC electric field is applied to the sample stage varies depending on the position within the sample. It was found that the other problem that the film forming speed and the step coverage are different caused by.

The present inventor applies a high frequency or direct current electric field to the sample stage, and at the same time rotates the sample stage, the bias potential applied to the sample is made uniform, so that the step coverage can be formed with good step coverage even for a structure having a high aspect ratio. I found that I could make a film and solved it. That is, the present invention is as follows.

(1) A plasma generation region for generating plasma by using an electric field generated by microwaves and a magnetic field generated by an electromagnetic coil or a permanent magnet; a sample arrangement region provided with a sample stage for mounting a sample; In a sputtering device comprising a target supported by a target support between the region and the sample placement region, the target has a plurality of holes that communicate the plasma generation region and the sample placement region, A sputtering apparatus comprising: a means for applying a high frequency electric field or a direct current electric field to the sample stage and a rotating mechanism for rotating the sample stage.

(2) A plasma generation region for generating plasma by using an electric field generated by microwaves and a magnetic field generated by an electromagnetic coil or a permanent magnet; a sample arrangement region provided with a sample stage for mounting a sample; In a sputtering apparatus including a target supported by a target support between the region and the sample placement region, the target is composed of a plurality of cylinders that communicate the plasma generation region and the sample placement region. And a means for applying a high frequency electric field or a direct current electric field to the sample stage, and a rotating mechanism for rotating the sample stage.

[0015]

When the target has a plurality of holes that connect the plasma generation region and the sample placement region (FIG. 2), or when the target is composed of a plurality of cylinders that connect the plasma generation region and the sample placement region. (Fig. 3)
The case where a plurality of holes are provided will be described as a representative. FIG. 6 simply shows the directions of the trajectories of particles sputtered from the target. FIG. 6 (a) shows the case of the target of the conventional ECR sputtering apparatus, and FIG. 6 (b) shows the case of the target having a plurality of holes of the present invention. From this figure, it is understood that the target having a plurality of holes of the present invention has a higher directivity of sputtered particles and a higher probability of being incident on the sample.
Also, the surface area of the target per unit length is large because the surface area of each hole is small but the number of holes is large, and the utilization efficiency of the target is high. Further, by combining the position and size of the holes of the target as compared with the conventional sputtering apparatus, it is possible to make the film forming rate uniform on the sample.

Further, by applying a high frequency or direct current electric field to the sample stage, the ions are made incident on the sample. As a result, among the sputtered particles adhered on the sample S, the sputtered particles adhered to a portion having a large ion incident angle are re-sputtered and re-adhered to the side wall portion to improve the step coverage.

However, although the ECR sputtering apparatus for this target is originally capable of forming a very uniform film, this uniformity deteriorates when a high frequency or DC electric field is applied.
This is because there is a slight change in the plasma distribution depending on whether it is shaded on the sample with respect to the shape of the target, and this is emphasized as a difference in bias potential depending on the position when a high frequency electric field is applied. This is because the uniformity of speed and step coverage distribution deteriorates. That is, since the plasma density of the shadow area of the target is low, the amount of ions jumping into the sample is small and the bias potential is small, so film formation by sputtered particles proceeds, but resputtering decreases, so film formation is reduced. This is because the speed is high but the step coverage is inferior, and conversely, the non-shadowed portion has a low film formation speed but good step coverage. By applying a high frequency or a DC electric field to the sample while rotating the sample table, the bias potential distribution is made uniform and deterioration of the uniformity is prevented.

[0018]

Embodiments of the present invention will be specifically described below with reference to the drawings. FIG. 1 is a schematic cross-sectional view of a sputtering apparatus which is an embodiment of the present invention, in which 1 denotes a reaction vessel. The reaction container 1 is composed of an ECR plasma generation region 2 and a sample placement region 3 in which a sample stand 12 on which a sample S is placed is placed, and a target 4 is placed at the boundary between the two.

A microwave oscillator 6 is connected to the upper portion of the plasma generation region 2 via a waveguide 5. Further, an exciting coil 7 for generating a magnetic field is arranged around the upper part of the reaction container, and a gas introduction system 8 for supplying gas into the reaction container is arranged on the upper part of the reaction container. Then, the sample table having the electrode 13 in the sample placement area
12 is provided, and a high frequency power source 14 is connected to this electrode 13
A drive motor 15 for rotating the sample table 12 is connected to the sample 12. The gas introduction system 9 is also connected to the peripheral wall of the sample placement area. A DC power supply 10 for drawing ions is connected to the target 4. A plasma shielding plate 11 is arranged above the target 4 so that the upper surface of the target does not receive unnecessary spatter.

Next, the operation will be described. The reaction vessel 1 is evacuated to an unillustrated exhaust system, Ar gas is introduced into the reactor 1 from the gas introduction system 8, and a predetermined degree of vacuum is set. The sample S is placed on the sample table 12, and the sample motor 12 is rotated by the drive motor 15.
The pressure in the plasma generation region 2 is 10 ⁻⁴ to 10 ⁻² Torr.
In the pressure region of, the magnetic field required for ECR (electron cyclotron resonance) is generated in the plasma generation region by the excitation coil 7, and the microwave is generated from the microwave generation source 6 in the waveguide 5
It is introduced into the plasma generation region 2 via and the plasma is generated by ECR. Ar ions in this plasma are extracted toward the sample by the divergent magnetic field, and due to the negative potential of the DC power source added to the target 4, the Ar ions are attracted to the target 4 and sputter the target 4 to sputter the sample S.
Form a thin film on top. When this thin film is formed, a high frequency electric field is applied to the sample base electrode 13 to perform resputtering at the same time, thereby forming a thin film with good step coverage.

Next, a sample of Si using an Al target was used.
The filling of the SiO ₂ contact hole on the substrate will be specifically described. A target having a plurality of holes shown in FIG. 2 was used as the target. Si sample S, which is a sample, is mounted on the sample stand 12
It was placed on top and the sample stage 12 was rotated at 5 rpm. And Ar
Gas is introduced into the plasma generation region 2 through the gas introduction system 8 at a flow rate of 43 sccm, and the pressure in the plasma generation region 2 is set to 1 ×.
Set to 10 ^-3 Torr. Then, the magnetic field required for ECR is applied by the excitation coil 7, and the microwave power (frequency 2.45 GHz)
Was introduced at 2.0 kW and plasma was generated by ECR to perform sputter deposition. A voltage of −600 V was applied to the Al target 4 by the DC power supply 10. High frequency power (1
(3.56 MHz) was applied at 150 W.

FIG. 7 shows the in-plane distribution of the deposition rate of the thin film thus obtained. The vertical axis is the film formation rate (Å / mi
n), the horizontal axis is the position (mm) from the center. In the figure, ◯ indicates the distribution in the X axis direction, and □ in the figure indicates the distribution in the Y axis direction. X
The axis is the XX 'direction of the target in FIG. 2, the Y axis is the direction perpendicular to it, and the origin is the center of the sample. The uniformity of the film formation rate within the surface of the sample is ± 4.6 in the X-axis and Y-axis directions, respectively.
%, ± 4.2%.

FIG. 8 shows the results when 150 W of high frequency power was applied to the sample table but the sample table was not rotated. The uniformity of the in-plane deposition rate is ± 4.8% in the X-axis direction and ± 9% in the Y-axis direction.
It was 8%. The reason why the uniformity in the Y-axis direction deteriorated is that
Since Y = 25mm in the axial direction is the shadow of the target,
This is because the film forming speed is increasing. From these two results, it can be seen that it was possible to prevent the uniformity of the in-plane distribution from being deteriorated by applying rotation.

FIGS. 9, 10, and 11 show an apparatus using an improved target, in which the sample stage is rotated while the high frequency is applied to the sample stage of the present invention, when the high frequency is not applied to the conventional sample stage, It is a figure which shows the cross section of the contact hole part obtained in each case when a high frequency is applied to a stand but a sample stand is not rotated. For each of (a) and (b), X = 25mm,
It is at the position of Y = 25 mm. The high frequency power added is
It was 150W. From this result, it is understood that the step coverage is improved by applying the high frequency electric field, and the uniformity of the in-plane distribution is improved by rotating the sample stage.

From these results, it can be seen that the uniformity and step coverage are improved as compared with the conventional ECR bias sputtering apparatus. Although the exciting coil is used as the magnetic field generating means in this embodiment, a permanent magnet may be used instead of the coil. Further, although the present embodiment is the case of ECR, it is possible to reduce the pressure of plasma generation by applying a magnetic field without particularly using ECR, and there is an effect due to the reduction of pressure.

Further, although 13.56 MHz is used as the frequency of the high frequency electric field applied to the sample stage, any frequency may be used as long as a bias potential can be applied to the sample, and the effect can be obtained by using other frequencies such as 2 MHz and 400 kHz. Further, although 5 rpm was used as the rotation speed of the sample stage, other rotation speeds may be used, and the rotation angle may be a rotation angle at which the target is symmetric from the point on the sample (30 ° in this embodiment). The reciprocating rotation of is also acceptable. The center of rotation does not have to be the center of the sample,
On the contrary, shifting the center of rotation is effective for equalizing the bias potential.

In this embodiment, the contact hole was filled with Al, and Al was used as the target. However, since it was used for forming a thin film of a material other than this, the target was used.
Other materials than Al, such as Al alloy (Ai-Si-Cu), Cu,
W, WSi ₂ , Ti, TiN, TiSi ₂ , TiW, Ta, Si, SiO ₂
Etc.), and if the gas introduced into the plasma generation region together with these targets is Ar + O ₂ , then oxides of the above target materials, such as Al ₂ O _{3 in} the case of Al targets, and Si targets In case Si
In the case of O ₂ or Ta target, a thin film of Ta ₂ O ₅ can be formed. Similarly, when Ar + N ₂ or Ar + NH ₃ is introduced, it is possible to form a thin film of AlN in the case of an Al target, Si ₃ N _{4 in} the case of a Si target, and TiN in the case of a Ti target.

[0028]

As described above, in the apparatus of the present invention, the target has a plurality of holes that connect the plasma generation region and the sample placement region, or the target connects the plasma generation region and the sample placement region. Since it is composed of multiple cylinders, the target utilization efficiency is high, and it is possible to form a film at a high film formation rate. Furthermore, because the structure is such that a high frequency or DC electric field can be applied while rotating the sample stage. Thus, it is possible to form a film with good step coverage without lowering the uniformity of the film formation rate.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a sputtering apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic view of a target having a plurality of holes used in an example of the present invention, (a) a top view, and (b) an XX ′ cross-sectional view.

FIG. 3 is a schematic view of a target composed of a plurality of cylinders according to another embodiment of the present invention, (a) a top view, and (b) an XX ′ cross-sectional view.

FIG. 4 is a schematic view of a conventional parallel plate type bias sputtering apparatus.

FIG. 5 is a schematic diagram of a conventional ECR bias sputtering apparatus.

6A and 6B are schematic views of a flying direction of particles to be sputtered, (a) a conventional target and (b) a target of the present invention.

FIG. 7 is a diagram showing a distribution of a film forming rate in an example of the present invention.

FIG. 8 is a diagram showing a distribution of film formation rates when only high-frequency power is applied to the sample stage in the ECR sputtering apparatus previously proposed by the present inventor.

FIG. 9 is a diagram showing a cross section of a contact hole in an example of the present invention, where (a) X = 25 mm position, and (b) Y = 25 mm.
Is the position.

FIG. 10 is a view showing a cross section of a contact hole in the ECR sputtering apparatus previously proposed by the present inventor, (a)
X = 25 mm position, (b) Y = 25 mm position.

FIG. 11 is a diagram showing a cross section of a contact hole when only high-frequency power is applied to the sample stage in the ECR sputtering apparatus previously proposed by the present inventor, and (a) X = 25.
mm position, (b) Y = 25 mm position.

[Explanation of symbols]

 1 Reaction Vessel 2 Plasma Generation Area 3 Sample Placement Area 4 Target 5 Waveguide 6 Microwave Oscillator 7 Excitation Coil 8 Gas Introduction System 9 Gas Introduction System 10 DC Power Supply 11 Plasma Shielding Plate 12 Specimen Base 13 Electrode 14 High Frequency Power Supply 15 For Driving Motor 21 Target with multiple holes 22 Target unit (hole) 23 Target unit (hole) 24 Target consisting of multiple cylinders 25 Target case 26 Target cylinder 27 Target cylinder 31 Reaction chamber 32 Sample stand 33 Target 34 High frequency power supply 35 High-frequency power supply 36 Gas introduction system 41 Plasma generation chamber 42 Sample chamber 43 Plasma extraction window 44 Target 45 Waveguide 46 Excitation coil 47 Gas introduction system 48 Sample stage 49 High-frequency power supply 50 DC power supply

Claims (2)

[Claims] 1. A plasma generation region in which plasma is generated using an electric field generated by microwaves and a magnetic field generated by an electromagnetic coil or a permanent magnet, a sample arrangement region including a sample stage on which a sample is mounted, and the plasma generation region. In a sputtering device comprising a target supported by a target support between the sample placement region and the sample placement region, the target has a plurality of holes communicating the plasma generation region and the sample placement region, A sputtering apparatus comprising: a means for applying a high frequency electric field or a direct current electric field to the sample stage and a rotating mechanism for rotating the sample stage. 2. A plasma generation region in which plasma is generated using an electric field generated by microwaves and a magnetic field generated by an electromagnetic coil or a permanent magnet, a sample placement region including a sample stage on which a sample is mounted, and the plasma generation region. In a sputtering apparatus comprising a target supported by a target support between the sample placement region and the sample placement region, the target is composed of a plurality of cylinders that connect the plasma generation region and the sample placement region. A sputtering apparatus comprising: a means for applying a high frequency electric field or a direct current electric field to the sample stage; and a rotating mechanism for rotating the sample stage.