JPH0375361A - Formation of film by sputtering - Google Patents

Abstract

PURPOSE:To control force per unit width of a thin film and to obtain a thin film hardly causing peeling or cracking by changing vias voltage on a substrate, the interval between a target and the substrate, the rate of film formation or the pressure of sputtering during film formation. CONSTITUTION:A target 2 and a sample stand 3 for setting a substrate 4 are arranged in the vacuum vessel 1 of a dipole magnetron sputtering device and a thin film is formed on the surface of the substrate 4 by sputtering. During this film formation, the substrate 4 is moved up or down by vertically driving a driving mechanism 6 for moving the stand 3 up or down to change the interval between the target 2 and the substrate 4. The pressure of gaseous Ar fed from a tank 9 may be changed with a mass flow controller 11. Layers with applied compressive force and layers with applied tension are alternately formed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a sputtering film forming method used particularly for forming a thin film of about 1 μm or more.

[Prior Art and Problems] Conventionally, sputtering thin film forming apparatuses that apply the sputtering action of ion particles have been widely used in the manufacture of semiconductor devices, research into highly functional thin films, surface modification of metals, and the like. Incidentally, in recent years, thin films used in LSIs are required to have less distortion. Further, in applications to metal surface modification, a film thickness of 1 μm or more is often required, so it is extremely important to produce a thin film with small distortion in order to prevent cracking and peeling.

Recently, the general properties of thin films formed by sputtering have been investigated. Regarding internal stress, the dependence on sputtering gas pressure is shown in Figure 4 (film deposition rate r+'+JE
Plate bias voltage 0. The distance between the target and the board is ),
The film formation rate dependence is shown in Figure 5 (sputtering gas pressure PL, substrate bias voltage O.

The dependence on the bias voltage applied to the substrate is shown in Figure 6 (sputtering gas pressure P l + deposition rate r0. target-substrate distance), and the dependence on the target-substrate distance is Figure 7 (Sputtering gas pressure Pl
, film formation rate r9. It is a well-known fact that the distance between the target and the substrate is expressed as: It is clear from FIG. 4 that tensile or compressive internal stress is likely to be applied due to slight fluctuations in sputtering gas pressure. It is clear from FIG. 5 that tensile or compressive internal stress is likely to be applied due to slight variations in the film forming rate. It is clear from FIG. 6 that tensile or compressive internal stress is likely to be applied due to slight variations in substrate bias voltage. From FIG. 7, it is clear that tensile or compressive internal stress is likely to be applied due to slight variations in the target substrate distance. For this reason, in order to reduce the internal stress, it is necessary to form a film strictly within a narrow range of film forming conditions. Further, the product of internal stress σ and film thickness d is called force per unit width or total stress, which is proportional to the deflection of the substrate and is independent of the type.

However, the film thickness dependence of this force per unit width (total stress) is
p1856-1867) As is clear from J, it gradually increases with the film thickness. Moreover, the relationship between the internal stress σ and the film thickness d of the sputtered thin film as described above is as shown in Figure 8, which will be described later, and the force per unit width (total stress)
The relationship between σ·d and film thickness is as shown in FIG.

Thus, in order to suppress the internal stress to a small value, it is necessary to strictly limit the film forming conditions. However, although the internal stress changes only slightly as the film thickness increases, the force per unit width (total stress) increases significantly as the film thickness increases. As the force per unit width (total stress) increases, the thicker the film is, the more likely it is to crack or peel off. Furthermore, internal stress is intricately linked to the thin film growth mechanism, and a simple method such as periodically changing the sputtering gas pressure near zero internal stress based on Figure 4 is not sufficient. No improvements were made.

The present invention was made in view of the above circumstances, and is a sputtering method that suppresses the force per unit width of the thin film (total stress) within a small range and produces a thin film that is less prone to peeling (swelling) and cracking. The purpose is to provide a membrane method.

[Means for Solving the Problems] The present invention uses a sputtering apparatus that includes a vacuum chamber, a target placed in the vacuum chamber, and a sample stage on which the vacuum chamber in-vacuum viewing table is set. The method of forming a sputtering film on the main surface of the substrate is characterized in that during film formation, at least one of the bias voltage applied to the substrate, the distance between the target and the substrate, the film formation rate, or the sputtering gas pressure is changed. This is a sputtering film forming method.

[Function] In the present invention, in order to keep the force per unit width of the thin film (total stress) small at all times, it is necessary to keep the force (total stress) per unit width of the thin film small. Depending on the film thickness, the sputtering gas pressure, deposition rate, bias voltage, target
It is sufficient to change at least one of the distances between the substrates. In other words, in order to prevent a thin film from peeling or cracking, it is sufficient to keep the force per unit width (total stress) within an allowable range, so it is not necessary to keep the conditions constant until the desired film thickness.
The film can be formed by changing the conditions several times, or by changing the film forming conditions when a preset film thickness is reached, so that a layer with tensile force and a layer with compressive force can be formed depending on the film forming conditions. It is best to stack them alternately. As a result, the force per unit width (total stress) of the entire thin film can be kept within a small range, and as a result, peeling and cracking can be avoided.

Furthermore, the steepness of the crystallographic structure and stress transition between layers having opposing forces can be optimized by smoothing the way in which the film forming conditions are varied.

Examples of the present invention will be described below.

[Example 1] FIG. 1 is an explanatory diagram of a two-pole magnetron sputtering device according to the present invention.

1 in the figure is a vacuum chamber, which is evacuated by an exhaust system (not shown). A target 2 is arranged on the exhaust system side (lower side) of the vacuum chamber 1.

On the upper side of the vacuum chamber 1, a sample stage 3 whose potential can be varied with respect to ground is arranged parallel to the main surface of the target 2. At the bottom of the sample stage 3, a substrate (trade name: Corning 7059 glass, manufactured by Corning Incorporated) is installed.
4 is set. A shutter 5 is arranged between the target 2 and the sample stage 3. This shutter 5 closes the target 2 before starting film formation on the substrate 4.
It has the function of preventing flying particles from being deposited on the substrate 4.

A vertical drive mechanism 6 for moving the sample stage 3 up and down is provided at the top of the vacuum chamber 1. By vertically driving this vertical drive mechanism 6, the substrate 4 moves up and down, and the distance between the target 2 and the substrate 4 changes. The vertical drive mechanism 6
A digital-analog converter (D/A) 7 is electrically connected to.

Further, a bipolar DC power source 8 is connected between the sample stage 3 and the converter 7. This DC power supply 8 has the function of changing the potential of the sample stage 3.

A mass flow controller (MFC) 11 is provided on the side wall of the vacuum chamber 1 to control the flow rate of sputtering gas such as Ar gas IO in the tank 9 .

Here, A of the exhaust system "Since the amount of gas exhaust is constant,
Increasing the gas flow rate from MFCll increases the sputtering gas pressure, and decreasing the Ar gas flow rate decreases the sputtering gas pressure. The converter 7 is also connected to the MFCII.

The target 2 and the converter 7 are electrically connected via a sputtering power source 12. Here, if the output of the sputtering power source 12 is increased, the film formation rate will be increased, and if the output of the sputtering power source 12 is decreased, the film formation rate will be decreased. From the converter 7, the vertical drive mechanism 6
, the bipolar DC power supply 8 and the mass flow controller 11
and the distance between the target and the substrate for the sputtering power source 12,
Bias voltage.

A: “Signals are sent to adjust the gas pressure and film formation speed.

A microcomputer 13 that controls the signal is connected to the converter 7.

In Example 1, the apparatus shown in FIG. 1 was used, and Ar gas was used as the sputtering gas. Then, every time a film of 0.25 μm is formed, the mass flow controller 11
A Til32 thin WI4 (sputtered thin film) with a total thickness of 5 μm was formed on the substrate 4 by changing the pressure of r gas (as shown in Figure 3) and alternately forming layers to which compressive force was applied and layers to which tensile force was applied. It was filmed.

According to Example 1, a mass flow controller 11 is provided on the side wall of the vacuum chamber 1, and the pressure of Ar gas is changed from the mass flow controller 111 every time a film of 0.25 μm is formed to form a thin film on the substrate 41: TiB. As a result of forming a film, it is possible to finally obtain a TiB thin film with 1M peeling and no cracks. In fact, after forming TiB2 thin films of appropriate thickness on several substrates under the above conditions, the substrates were taken out and
When the warpage of the substrate was measured and the force per unit width (total stress) was determined, the characteristic diagram shown in FIG. 3 was obtained. From the same figure,
It is clear that the total stress is suppressed within a small range of about ±0.5 K g f /cm.

C Example 2] In this Example 2, a TiB thin film having a total thickness of 5 μm was formed on the substrate 4 by changing the film forming rate every time a film of 0.25 μm was formed. According to this second embodiment, the same effects as in the first embodiment can be obtained.

[Example 3] In this Example 3, a TiB2 thin film having a total thickness of 5 μm was formed on the substrate 4 by changing the bias voltage using the bipolar DC power supply 8 every time a 0.times.25 μm film was formed.

In Example 3, the edge of the substrate 4 was thinly coated with copper to establish electrical conduction with the thin film. According to the third embodiment, effects similar to those of the first embodiment can be obtained.

[Example 4] In this Example 4, the distance between the target 2 and the substrate 4 was changed by the vertical drive mechanism 6 every time 0.25 μm was deposited, and a TiB2 thin film with a total thickness of 5 μm was deposited on the substrate 4. .

According to this fourth embodiment, effects similar to those of the first embodiment can be obtained.

[Example 5] In Example 5, a TiB2 thin film having a total thickness of 5 μm was formed on the substrate 4 while changing the pressure of Ar gas as shown in FIG. 2 every time a film of 0.25 μm was formed. According to this Example 5, in addition to being able to obtain the same effects as in Example 1, a thin film was formed in which the film structure gradually changed as the film forming conditions changed.

[Comparative example]

TiB was deposited on the substrate using a two-pole magnetron sputtering device.
2 thin film 21 was formed, and the warpage of the substrate was measured to determine the internal stress σ of the thin film, and the results shown in FIG. 8 were obtained.

For comparison, the relationship between the film thickness d and the total stress σ·d was also determined, and a characteristic diagram as shown in FIG. 9 was obtained. 8th
From the figure, it is clear that the internal stress does not change much even when the film thickness increases. On the other hand, it is clear from FIG. 9 that the total stress changes significantly as the film thickness increases.

However, in both figures, the straight line (A) is at an Ar gas pressure of 5 m.
In case of T orr, direct I! (B) is A “Gas pressure 5 m
This is the case for Torr. Further, in both (a) and (b), the film formation rate was 11.5λ, and the substrate bias Ov1 was 50 sv between target and substrate. By the way, the thickness of the thin film is 1.8
When the thickness of the thin film was 2.0 μm, peeling 22 occurred as shown in FIG. 1O, and when the thickness of the thin film was 2.0 μm, cracks 23 occurred as shown in FIG. 11.

In the above embodiment, Corning 7059 is used as the substrate.
Although the case using glass has been described, it is not limited to this.
Effects similar to those of the above embodiments can be obtained when a metal plate such as copper is used.

Furthermore, in each of the above embodiments, the sputtering gas pressure.

The case where the film formation rate, the bias voltage applied to the substrate, and the distance between the target and the substrate are individually varied has been described; however, the present invention is not limited to this, and it is also possible to vary any number of each variation factor in any combination. .

[Effects of the Invention] As detailed above, according to the present invention, the force per unit width of the thin film (total stress) can be suppressed to a small range, and a thin film that is less prone to peeling (swelling) or cracking can be created. It is possible to provide a highly reliable sputtering film-forming method.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a two-pole magnetron sputtering device according to the present invention, FIG. 2 is a characteristic diagram showing the relationship between film thickness and A gas pressure according to Example 5 of the present invention, and FIG. Thickness and total stress, A
Figure 4 is a characteristic diagram showing the relationship between sputtering gas pressure and stress in the film. Figure 5 is a characteristic diagram showing the relationship between film formation rate and stress in the film. Figure 6 is a characteristic diagram showing the relationship between substrate bias voltage and stress in the film, Figure 7 is a characteristic diagram showing the relationship between target-substrate distance and stress in the film, and Figure 8 is a diagram showing the relationship between film thickness and internal stress. Characteristic diagram showing the relationship, No. 9
The figure is a characteristic diagram showing the relationship between film thickness and total stress, and FIGS. 10 and 11 are cross-sectional views of the substrate for explaining the drawbacks of the prior art, respectively. DESCRIPTION OF SYMBOLS 1... Vacuum chamber, 2... Target, 3... Sample stage, 4... Substrate, 5... Shutter 6... Vertical drive mechanism, 7... Digital-to-analog converter, 8... ... Bipolar DC power supply, 9 ... Tank, 10 ... Sputter gas, 11 ... Mass flow controller, 12 ... Power source for sputtering, 13 ... Microcomputer. Figure 1

Claims (1)

[Claims] A vacuum chamber, a target placed in this vacuum chamber,
In the method of forming a sputtered thin film on the main surface of the substrate using a sputtering apparatus equipped with a sample stage on which a substrate placed in the vacuum chamber is set, during film formation,
A sputtering film forming method characterized by changing at least one of the bias voltage applied to the substrate, the distance between the target and the substrate, the film forming rate, or the sputtering gas pressure.