JPS61261472A - Bias sputtering method and its apparatus - Google Patents

Abstract

PURPOSE:To obtain a flat thin film of high purity not contg. the constituent substance of a substrate by depositing the constituent element of a target on the substrate by sputtering without applying bias to the substrate, applying negative potential, and depositing the constituent element of the target by sputtering. CONSTITUTION:A target 3 is placed in a vacuum chamber 1 so that it confronts a substrate 2 in the chamber 1, and the constituent element of the target 3 is deposited on the substrate 2 by sputtering the target 3 with ions without applying negative potential to the substrate 2. After the lapse of a fixed time, negative potential is applied to the substrate 2, and the constituent element of the target 3 is deposited on the substrate 2 under the potential to form a thin film.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a bias sputtering method for forming a thin film with a flat surface and a dense structure on an uneven substrate when manufacturing semiconductor integrated circuits. and a bias sputtering device.

[Conventional technology]

Sputtering has been widely used as a method for depositing thin films on substrates in the manufacturing process of semiconductor integrated circuits and the like. However, with normal sputtering method.

It has been difficult to form a thin film that continuously covers uneven stepped portions with a surface similar to that of flat portions.

A bias sputtering method has been proposed as a method for improving the above-mentioned drawbacks of the conventional sputtering method. In this method, a negative potential is applied to the substrate to be sputtered so that accelerated ions are incident on the surface of the substrate, thereby forming a thin film having a flat surface on an uneven substrate.

[Problem that the invention seeks to solve]

Since the bias sputtering method described above injects accelerated ions onto the substrate surface, sputter etching progresses at the same time as deposition on the substrate surface. Therefore, in the early stage when the deposited film is not sufficiently deposited on the substrate, the structure of the sputter etched substrate is The elements will be mixed into the deposited film, reducing the purity of the formed deposited film. Furthermore, since the structure of the deposited film is changed at the same time, it not only becomes impossible to form a high-quality thin film, but also has the inherent disadvantage that damage to the substrate becomes a problem. The bias sputtering method is shown by two lines,
Since aluminum crystal grain growth is suppressed by oxygen and silicon scattered from the substrate, columnar crystals with gaps between crystal grains grow. The aluminum film described above exhibits an infinite resistance value.

[Means for solving problems]

In the present invention, constituent elements of a target are sputter-deposited with no bias applied to the substrate, and then, after a certain time delay, a bias is applied to the substrate to perform sputter deposition.

[Effect]

As described above, in the present invention, first, the target power source is operated, sputtering is performed without applying a bias to the substrate, and target constituent elements are deposited on the substrate. This deposited film is formed of highly pure target constituent elements that are not mixed with substrate constituent substances. Next, bias sputtering is performed by applying a bias to the substrate, but at this time, the deposited film is subjected to an etching action, and there is a possibility that constituent materials may be mixed into the newly formed deposited film, but the deposited film itself Since it is a highly pure target constituent material, its contamination will not reduce the purity of the newly formed deposited film. Furthermore, since the bias sputtering does not directly hit the substrate surface with ions, the substrate is less likely to be damaged.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a bias sputtering apparatus according to the present invention, FIG. 2 is a diagram showing an example of power input between the target power supply and the substrate power supply in the above embodiment, and FIG. Fig. 4 shows a scanning electron micrograph of the surface of the bias sputtered aluminum film when t1 is 60 seconds, and Fig. 5 shows the change in resistivity of the aluminum film with respect to the waiting time of t□. A diagram showing the relationship between the step coverage (ratio of d and do) with respect to the initial film thickness when the thickness (initial film thickness + bias sputtering film thickness) is 1.5-. It is a figure which shows the cross-sectional photograph taken by the scanning electron microscope when bias-sputtering an aluminum film on the board|substrate with the 0.8-depth groove|channel. In FIG. 1, a substrate 2 and a target 3 are provided facing each other in a vacuum chamber l, and a target power source 4 electrically connected to the target 3 is either a direct current or a high frequency power source. A high frequency power source is used when the power source is made of an insulator. The substrate side power supply 5 electrically connected to the substrate 2 can be a high frequency generator or a DC voltage generator. The substrate side power supply 5, the target power supply 4, the vacuum exhaust device 6, the gas controller 9. The shutter 10 and the like are each held in a driven or stopped state by a signal sent from the sequence controller 8.

A substrate 2 is installed in a vacuum chamber 1, and the vacuum chamber 1 is evacuated by a vacuum exhaust device 6, and a sputtering gas is introduced into the vacuum chamber 1 using a gas controller 9 to maintain a constant pressure.
An inert gas such as argon is used as the sputtering gas at this time. Next, the target power source 4 is activated. At this time, if the target electrode 3 is a parallel plate type bipolar sputter, plasma 7 is generated between the target electrode 3 and the substrate 2. Furthermore, when a magnetron attached to the target electrode 3 is used, plasma 7' is generated near the target electrode 3. At this time, target electrode 3
The target constituent elements tend to be deposited on the substrate 2 due to the sputtering effect due to the bias generated between the plasma 7 or 7'. The shutter 10 is opened and the target constituent elements are deposited on the substrate 2, and after a time t1 has elapsed, deposition is performed by applying high frequency or DC bias to the substrate 2. In this case, since the deposition is performed in the presence of etching action due to ion bombardment, a film having a flat surface can be deposited even if the surface of the substrate 2 is uneven.

FIG. 2 shows an example of temporal changes in substrate power and target power in the above process. Although such time control can be performed manually, control using signals from the sequence controller 8 allows highly accurate control. The thin film deposited by time t1 is of high purity and is free from contamination with substrate constituent substances because no high frequency or direct current bias is applied to the substrate 2. Next t1
If the deposition is performed with a bias applied after the above t□ waiting time, there is a possibility that the thin film deposited on the substrate 2 will be mixed into the deposited film due to the etching action, but this thin film itself is a highly pure target composition. Since it is a substance, it does not deteriorate the purity of the deposited film. Furthermore, since the surface of the substrate 2 is not directly bombarded with ions, damage to the substrate is reduced. t when forming an aluminum film by bias sputtering using Sio as the substrate 2
□The relationship between waiting time and resistivity of the aluminum film is shown in Figure 3. When the t1 time is 0, that is, when aluminum is deposited with a bias applied to the substrate from the beginning, the resistivity becomes infinite. The surface condition of the aluminum at this time is as shown in FIG. As can be seen from the scanning electron micrograph shown in FIG. 7, grain growth occurs with gaps between crystals. On the other hand, t1 time is 3.6.15.2
As the time increases to 00 seconds, the resistivity decreases and the variation becomes smaller, allowing the deposition of an aluminum film with a more uniform and smooth surface as shown in the scanning electron micrograph of FIG. In addition, if the t process is too long, the thickness of the film deposited without applying a bias to the substrate 2 will become thicker, so if a bias is subsequently applied and aluminum is deposited to obtain the desired film thickness, It becomes impossible to obtain a flat surface shape with good coverage.

The initial deposited film thickness (
After the deposition was performed by varying the deposition time (without bias, t process time), the total film thickness (initial film thickness + bias sputtering film thickness) was increased to 1.5. When ca (d,), the distance from the edge of the groove to the film surface on the center line of the groove (
Figure 5 shows the relationship between the ratio of d and /d and the initial deposited film thickness. It can be seen that the ratio becomes smaller and the coverage becomes worse. FIG. 6 shows that, using the method and apparatus according to the present invention, two lines and spaces are
4-2-1 This is a scanning electron micrograph showing an aluminum film deposited on a substrate with a groove of 0.8t1m in depth by selecting an appropriate t4. It is completely embedded in the groove, forming a film with very good coverage.

As explained above, by selecting an appropriate t-process and performing high-precision control using the sequence controller 8, a high-quality thin film with a smooth surface, low resistivity, little damage to the substrate, and uniform coverage can be produced. can be deposited.

〔Effect of the invention〕

As described above, the bias sputtering method and bias sputtering apparatus according to the present invention sputters a target provided facing the substrate with ions while applying a negative potential to the substrate in a vacuum chamber, and sputters the sputtered target. In the bias sputtering method for depositing constituent elements on the substrate, the target constituent elements are deposited on the substrate without applying a negative potential to the substrate, and then the target constituent elements are deposited on the substrate while a negative potential is applied to the substrate. By depositing the elements on the above substrate to form a thin film, the substrate constituent materials do not mix into the thin film, resulting in high purity, flat and uniform even if the substrate surface has irregularities, and very good coverage. , thin films can be deposited with less damage to the substrate. Therefore, even when the wiring of a semiconductor integrated circuit is multilayered, there is an effect that highly reliable wiring can be formed without any breakage in one step.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing an embodiment of a bias sputtering apparatus according to the present invention, FIG. 2 is a diagram showing an example of power input between the target power supply and the substrate power supply in the above embodiment, and FIG. Figure 4 shows the change in resistivity of the aluminum film. Figure 4 is a scanning electron micrograph of the surface of the bias sputtered aluminum film when t1 is 60 seconds.
The figure shows the relationship between the step coverage and the initial film thickness when the total film thickness is λ and 5Is. In Fig. 6, the line and space is 2pm, 2Bra, and the depth is 0.8. Figure 7 shows a cross-sectional photograph taken by a scanning electron microscope when an aluminum film was bias-sputtered onto a substrate having grooves. It is a figure showing a photograph. 1...Vacuum chamber 2...Substrate 3...Target 4...Target power supply 5...Substrate side power supply 8...Sequence control system 51゛Applicant Telegraph and Telephone? TG type company representative patent attorney Junnosuke Nakamura Figure 2 Time Figure 3 Time 1 (sec) Figure 4 2P'''L Figure 5 - (, Lm) Section 1 m Procedural amendment (voluntary) Showa June 28, 1960 Manabu Shiga, Commissioner of the Patent Office1, Indication of the case Patent Application No. 99505 of 19852, Title of the invention Bias sputtering method and its device3, Relationship with the amendment person case Name of patent applicant (422) Nippon Telegraph and Telephone Corporation 5,
Target of amendment: Drawing 6 and details of amendment: Drawing 3 will be corrected as attached. No=-＼＼ Fig. 3 Time of 1 (sec)

Claims (2)

[Claims] (1) In the bias sputtering method, a target provided opposite to the substrate is sputtered with ions while a potential is applied to the substrate in a vacuum chamber, and constituent elements of the sputtered target are deposited on the substrate. The target constituent element is deposited on the substrate in a state where no negative potential is applied to the substrate, and then the target constituent element is deposited on the substrate while a negative potential is applied to the substrate,
A bias sputtering method characterized by forming a thin film. (2) In the bias sputtering method, a target provided opposite to the substrate is sputtered with ions while a potential is applied to the substrate in a vacuum chamber, and constituent elements of the sputtered target are deposited on the substrate. A target power source that applies a DC voltage or high frequency voltage to the electrode of the target, a substrate side power source that applies a DC voltage or high frequency voltage to the substrate, and a substrate side power source that operates after a certain time delay after the target power source is activated. A bias sputtering apparatus characterized by comprising a sequence control mechanism for controlling application and stopping of each of the above-mentioned power supplies.