JP7727174B2 - Sputtering Equipment - Google Patents

Description

The present invention relates to a sputtering device that uses plasma to sputter a target and form a film on a substrate.

In addition to magnetron sputtering devices, other sputtering devices include those described in Patent Documents 1 and 2, for example, which place an antenna near the target and generate plasma for sputtering by passing a high-frequency current through the antenna. In these sputtering devices, the plasma density is smaller than in so-called magnetron sputtering devices, which generate plasma using a magnet. This smaller plasma density is expected to improve target utilization efficiency and film formation uniformity.

Japanese Patent Application Laid-Open No. 2018-154875 JP 2014-37555 A

While the sputtering devices disclosed in Patent Documents 1 and 2 can improve the uniformity of film formation to a certain extent, they are still not sufficient. For example, in the case of Patent Document 1, the volume of the discharge space varies depending on the position of the substrate to be sputtered, and the plasma density distribution also varies, resulting in variations in film formation depending on the position on the substrate. In particular, the discharge volume is larger near the edges of the substrate than in the center of the substrate, resulting in lower plasma density and reduced film thickness. Furthermore, in the case of Patent Document 2, the deposition shield used to prevent film deposition on the rear of the substrate is located closer to the target than the substrate, resulting in more shielding from sputtered particles than necessary. In particular, the deposition shield is positioned so that it slightly overlaps the edge of the substrate to prevent film deposition on the rear of the substrate, resulting in reduced film thickness at the edge of the substrate.

One aspect of the present invention aims to further improve the uniformity of film formation in a sputtering device that uses plasma generated by an antenna.

In order to solve the above problems, one aspect of the present invention provides a sputtering apparatus that uses plasma to sputter a target to form a film on a substrate, and includes a vacuum vessel that is evacuated and into which gas is introduced, a substrate holder that holds the substrate within the vacuum vessel, and an extension member that extends the surface of the substrate on the film-forming side, the extension member being positioned on the substrate holder so as to contact or be in close proximity to the edge of the substrate when the substrate is held by the substrate holder.

One aspect of the present invention can improve the uniformity of film formation on a substrate.

1 is a vertical cross-sectional view perpendicular to the longitudinal direction of an antenna, schematically illustrating the configuration of a sputtering apparatus according to a first embodiment of the present invention. 2 is a perspective view showing a state in which a substrate on which a film is formed by the sputtering apparatus shown in FIG. 1 is held by a substrate holding member. FIG. 2 is a schematic diagram showing the positional relationship between the antenna, the target, and the substrate in the embodiment. FIG. FIG. 4 is a cross-sectional view taken along line AA′ in FIG. 3 . FIG. 3 is a schematic diagram showing the diffusion distribution of sputtered particles in the embodiment. 2 is a vertical cross-sectional view perpendicular to the longitudinal direction of the antenna, schematically illustrating the density of sputtered particles in a vacuum chamber during film formation in the sputtering apparatus shown in FIG. 1. FIG. 2 is a vertical cross-sectional view perpendicular to the longitudinal direction of the antenna, schematically illustrating the density of sputtered particles in a vacuum chamber during film formation when an extension plate is not provided on a substrate in the sputtering apparatus shown in FIG. 1. FIG. 1. FIG. 4 is a vertical cross-sectional view perpendicular to the longitudinal direction of the antenna, schematically showing the density of sputtered particles in a vacuum chamber during film formation in the sputtering apparatus shown in FIG. 1, with the substrate being transported in the scanning direction. FIG. 2 is a vertical cross-sectional view perpendicular to the longitudinal direction of the antenna, which schematically shows the density of sputtered particles in a vacuum chamber during film formation when an extension plate is not placed on the substrate and the substrate is transported in the scanning direction in the sputtering apparatus shown in FIG. 10 is a graph showing the film thickness distribution with and without an extension plate. 10 is a graph showing the film thickness distribution depending on the width of the extension plate.

[Embodiment 1]
Hereinafter, one embodiment of the present invention will be described in detail.

(Overview of sputtering equipment)
1 is a schematic cross-sectional view of a sputtering apparatus 100 according to this embodiment. The sputtering apparatus 100 sputters a target T using an inductively coupled plasma P to form a film on a substrate W. Here, the substrate W is, for example, a substrate for a flat panel display (FPD) such as a liquid crystal display or an organic EL display, a flexible substrate for a flexible display, or the like.

As shown in FIG. 1, the sputtering apparatus 100 comprises a vacuum vessel 2, a substrate holder 3 for holding a substrate W, a target holder 4 for holding a target T, multiple linear antennas 5, and a high-frequency power supply 6 for applying high-frequency power to the multiple antennas 5. When high-frequency power is applied to the multiple antennas 5 from the high-frequency power supply 6, a high-frequency current IR flows through the multiple antennas 5, generating an inductive electric field within the vacuum vessel 2 and generating an inductively coupled plasma P.

The vacuum vessel 2 is, for example, a metal vessel, and its interior is evacuated to a vacuum by a vacuum exhaust device (not shown). The vacuum vessel 2 is electrically grounded. A sputtering gas or a reactive gas is introduced into the vacuum vessel 2. The sputtering gas and the reactive gas may be selected according to the processing to be performed on the substrate W. The sputtering gas is, for example, an inert gas such as argon (Ar). The reactive gas is, for example, oxygen (O ₂ ) or nitrogen (N ₂ ).

As shown in FIG. 2, the substrate holding unit 3 is a holder that holds a flat substrate W. The substrate holding unit 3 also holds extension plates 20a and 20b. The extension plates 20a and 20b are extension members that expand the film-forming surface of the substrate W. The extension plates 20a and 20b are arranged on the substrate holding unit 3 so that they contact or are close to the ends W1 and W2 of the substrate W when the substrate W is held by the substrate holding unit 3. In this case, the extension plates 20a and 20b do not have to be arranged to contact both ends W1 and W2, but may be arranged close to both ends W1 and W2. Furthermore, instead of being arranged close to both ends W1 and W2, the extension plate 20a (20b) may be arranged to contact one end W1 (W2) and the extension plate 20b (20a) may be arranged close to the other end W2 (W1). The extension plates 20a and 20b are detachably fixed to the substrate holder 3 by screws or the like. Therefore, after film formation is completed, the substrate W is removed from the substrate holder 3, but the extension plates 20a and 20b remain in place. The substrate holder 3 holds the substrate W, for example, horizontally within the vacuum chamber 2 together with the extension plates 20a and 20b, and is configured to be scanned back and forth linearly within the vacuum chamber 2 as described below.

The extension plates 20a and 20b are arranged on both sides of the substrate W so that their surfaces (surfaces facing the target T) are flush with the surface of the substrate W (surface on the film formation side). In this embodiment, an example is described in which the extension plates 20a and 20b are arranged so as to contact the longitudinal ends W1 and W2 of the substrate W, but they may also be arranged so as to contact or be close to all ends of the substrate W, including the lateral ends. In this case, the extension plates may not only be in contact with all ends, but may also be arranged so as to be close to all ends. Furthermore, instead of being arranged so as to be close to all ends, the extension plates may be arranged so as to contact some ends and be close to the remaining ends.

The target holder 4 holds the target T, facing the substrate W and extension plates 20a and 20b held by the substrate holder 3. In this embodiment, the target T is a flat, rectangular plate in plan view. The target holder 4 is provided on the side wall 2a (e.g., the upper wall) that forms the vacuum vessel 2. An insulating part 9 with a vacuum sealing function is provided between the target holder 4 and the side wall 2a of the vacuum vessel 2. A target bias power supply 10 that applies a target bias voltage to the target T is connected to the target T via the target holder 4. The target bias voltage is a voltage that attracts ions in the plasma P to the target T, causing sputtering.

In this embodiment, multiple target holders 4 are provided. The multiple target holders 4 are arranged in parallel on the same plane on the front surface side of the substrate W in the vacuum chamber 2, along the front surface of the substrate W (e.g., substantially parallel to the rear surface of the substrate W). The multiple target holders 4 are arranged at equal intervals so that their longitudinal directions are parallel to one another. As a result, the multiple targets T arranged in the vacuum chamber 2 are arranged at equal intervals so that they are substantially parallel to the front surface of the substrate W and so that their longitudinal directions are parallel to one another, as shown in Figures 1 and 4. Note that each target holder 4 has the same configuration.

The multiple antennas 5 are arranged in parallel on the same plane on the surface side of the substrate W inside the vacuum vessel 2, along the surface of the substrate W (e.g., substantially parallel to the surface of the substrate W). The multiple antennas 5 are arranged at equal intervals so that their longitudinal directions are parallel to one another. As shown in Figure 3, each antenna 5 has a linear shape and the same configuration in a plan view, and its length is several tens of centimeters or more.

As shown in Figures 1 and 3, in this embodiment, the antennas 5 are arranged on both sides of the target T held by each target holder 4. In other words, the antennas 5 and targets T are arranged alternately, with each target T sandwiched between two antennas 5. Here, the longitudinal direction of each antenna 5 is the same as the longitudinal direction of the target T held by each target holder 4. Furthermore, as shown in Figure 4 in particular, the targets T are arranged so that the pitch width of the multiple targets T and the pitch width of the multiple antennas 5 are the same (both are pitch width Y). Furthermore, the antenna 5 arranged between two targets T is arranged equidistant from those two targets T.

The material of each antenna 5 may be, for example, copper, aluminum, alloys thereof, stainless steel, etc., but is not limited to these. The antenna 5 may also be hollow and a refrigerant such as cooling water may be passed through it to cool the antenna 5.

Furthermore, the portion of each antenna 5 located inside the vacuum vessel 2 is covered by a straight tubular insulating cover 12 made of an insulating material. There is no need to seal between both ends of this insulating cover 12 and the vacuum vessel 2. Even if gas enters the space inside the insulating cover 12, the space is small and the electrons have a short travel distance, so plasma P is not normally generated in the space. The material of the insulating cover 12 may be, for example, quartz, alumina, fluororesin, silicon nitride, silicon carbide, silicon, etc., but is not limited to these.

A high-frequency power supply 6 is connected to the antennas 5. The antennas 5 may be provided with an impedance adjustment circuit such as a variable capacitor or variable reactor to adjust the impedance of each antenna 5. By adjusting the impedance of each antenna 5 in this way, the density distribution of the plasma P in the longitudinal direction of the antenna 5 can be made uniform, and the film thickness in the longitudinal direction of the antenna 5 can be made uniform.

With the above configuration, a high-frequency current IR can be passed from the high-frequency power supply 6 to the antenna 5. The frequency of the high-frequency current is, for example, the common 13.56 MHz, but is not limited to this.

The sputtering apparatus 100 of this embodiment also has a reciprocating scanning mechanism 15 that reciprocally scans the substrate holder 3. The reciprocating scanning mechanism 15 reciprocally scans the substrate holder 3 along the arrangement direction X of the antenna 5, thereby causing the substrate W and extension plates 20a and 20b held by the substrate holder 3 to reciprocally scan along the arrangement direction X of the antenna 5.

The reciprocating scanning mechanism 15 mechanically scans the substrate holder 3 back and forth along the arrangement direction X of the antenna 5, thereby scanning the substrate W and extension plates 20a and 20b held by the substrate holder 3 back and forth on the same plane along the arrangement direction X. The forward and backward movements of the substrate W by this reciprocating scanning mechanism 15 are linear movements, and the forward and backward movements are configured to overlap. The reciprocating scanning mechanism 15 may, for example, include an actuator provided outside the vacuum vessel 2 and a linear guide connected to the substrate holder 3 and driven by the actuator.

Furthermore, as shown in Figures 3 and 4, the reciprocating scanning mechanism 15 is configured so that the scanning range SR of the substrate W and extension plates 20a and 20b is the pitch width Y. Specifically, a control device (not shown) that controls the reciprocating scanning mechanism 15 is configured so that the scanning range SR of the substrate W is the pitch width Y. In other words, the substrate W and extension plates 20a and 20b are scanned reciprocally with an amplitude of ±Y/2, with the initial position as the center position O.

In a configuration in which multiple targets T and multiple antennas 5 are arranged alternately, as in this embodiment, the diffusion ranges of sputtered particles emitted from each target T overlap, as shown in Figure 5. On the other hand, if the substrate W and extension plates 20a and 20b are not scanned, a distribution of film thickness and film quality with a period a may occur on the substrate surface. Here, the scanning range SR of the substrate W by the reciprocating scanning mechanism 15 has the same pitch width Y as the pitch width Y of the targets T, so the distribution of film thickness and film quality with a period a that may occur on the substrate surface can be leveled out, improving the uniformity of the film formation. Note that providing extension plates 20a and 20b on the substrate W can further improve the uniformity of the film formation. This point will be explained below.

(Improvement of uniformity of film formation)
As shown in FIG. 6 , when extension plates 20a and 20b are provided at the ends (W1 and W2) of the substrate W and positioned approximately in the center of the vacuum chamber 2, the extension plates 20a and 20b suppress the spread of plasma P. As a result, the densities of sputtered particles (indicated by the thick arrows in the figure) on the surfaces of the substrate W and the extension plates 20a and 20b are approximately the same. In this case, the provision of extension plates 20a and 20b at the ends (W1 and W2) of the substrate W prevents the plasma P from spreading at the ends of the substrate W, and therefore the density of sputtered particles at the ends (W1 and W2) of the substrate W does not decrease. This prevents the thickness of the film formed from the center of the substrate W toward the ends (W1 and W2) from decreasing, thereby improving the uniformity of the film formation.

On the other hand, when the extension plates 20a and 20b are not provided and the substrate W is placed approximately in the center of the vacuum chamber 2, as shown in Figure 7, the plasma P spreads from the edges (W1 and W2) of the substrate W to the outside of the substrate W. As the plasma P spreads, even if the density of sputtered particles on the surface of the substrate W (thick arrows in the figure) is approximately the same, the plasma P spreads outward from the edges (W1 and W2) of the substrate W, making the density of sputtered particles slightly lower than at the center of the substrate W. As a result, the thickness of the film formed decreases as the distance to the edges (W1 and W2) of the substrate W increases. This results in variations in the thickness of the film formed on the substrate W.

Furthermore, when extension plates 20a and 20b are arranged so as to contact the respective ends (W1 and W2) of the substrate W, even if sputtering is performed while the substrate is moved within the vacuum chamber 2 by the reciprocating scanning mechanism 15, as shown in Figure 8, there is no decrease in film thickness from the center of the substrate W toward the ends (W1 and W2), just as there is when the substrate W is stationary, as shown in Figure 6. In other words, even if the plasma P spreads as the substrate W moves and the density of sputtered particles decreases, this effect is felt by extension plate 20a, which is arranged so as to contact end W1 of the substrate W, and not by the end W1 side of the substrate W.

On the other hand, if extension plates 20a and 20b are not provided at the ends (W1 and W2) of the substrate W, and sputtering is performed while the substrate W is moved within the vacuum chamber 2 using the reciprocating scanning mechanism 15, as shown in Figure 9, the film thickness decreases from the center of the substrate W toward the ends (W1 and W2). In other words, as the substrate W moves, the plasma P spreads and the density of sputtered particles decreases, and this effect is felt on the end W1 side of the substrate W, resulting in a decrease in the film thickness formed on the end W1 side of the substrate W.

Furthermore, the surfaces of the extension plates 20a and 20b arranged at each end (W1 and W2) of the substrate W are flush with the surface of the substrate W on the film-forming side, so the boundary between the substrate W and the extension plates 20a and 20b is also flush. This makes it possible to eliminate volume fluctuations in the discharge space at the ends W1 and W2 of the substrate W, which are included in this boundary, thereby eliminating variations in the film thickness of the film formed on the substrate W and further improving the uniformity of the film formation.

In this way, to eliminate variations in the thickness of the film formed and improve the uniformity of the film formed, it is preferable to position the extension plates 20a and 20b as close as possible to each of the ends (W1 and W2) of the substrate W. For this reason, as described above, it is most preferable to position the extension plates 20a and 20b so that they are in contact with each of the ends (W1 and W2) of the substrate W. However, the extension plates 20a and 20b may also be positioned close to each of the ends (W1 and W2) of the substrate W without contacting them. In this way, when positioning the extension plates 20a and 20b close to the ends W1 and W2 of the substrate W, the extension plates should be positioned at a distance from the ends of the substrate that prevents variations in the thickness of the film formed at the ends W1 and W2 of the substrate W.

(Relationship between film distribution and extension plate)
The graph shown in Figure 10 shows the difference in film thickness distribution during film formation depending on whether or not extension plates 20a and 20b are provided, which are arranged to contact the edges W1 and W2 of the substrate W during film formation. In the graph shown in Figure 10, the horizontal axis represents the distance (arrangement position (mm)) from the center of the substrate to be film-formed to the edge, with 0 representing the center, and the vertical axis represents the measured film thickness at each arrangement position. The conditions for obtaining this graph were as follows: in the sputtering apparatus 100, the power supplied to the antenna 5 was 20 kW, the bias voltage applied to the target T was 400 V, the pressure in the vacuum chamber 2 was 0.5 Pa, and the _O2 ratio to the inert gas in the vacuum chamber 2 was 2.5%. The graph shown in Figure 10 shows the film thickness distribution with and without extension plates 20a and 20b.

As can be seen from the graph shown in Figure 10, when extension plates 20a and 20b are provided on the substrate W (with extension plates), there is less variation in the film thickness distribution than when extension plates 20a and 20b are not provided on the substrate W (without extension plates). In other words, it can be seen that when extension plates 20a and 20b are provided on the substrate W, the film formation uniformity is superior.

The graph shown in Figure 11 shows the difference in film thickness distribution during film formation due to differences in the width of the extension plate. Similar to the graph shown in Figure 10, the horizontal axis of the graph shown in Figure 11 represents the distance (arrangement position (mm)) from the center of the substrate to be film-formed to the edge, with 0 representing the center, and the vertical axis represents the measured film thickness at each arrangement position. The conditions for obtaining this graph were: in the sputtering apparatus 100, the power supplied to the antenna 5 was 20 kW, the bias voltage applied to the target T was 400 V, the pressure in the vacuum chamber 2 was 0.5 Pa, and the _O2 ratio to the inert gas in the vacuum chamber 2 was 2.5%. The graph shown in Figure 11 shows the film formation distribution when the widths of the extension plates 20a and 20b (the length in the direction away from the edges W1 and W2 of the substrate W) were 250 mm and 300 mm.

As can be seen from the graph in Figure 11, the wider the extension plates 20a and 20b, the less variation there is in the film thickness distribution. In other words, the wider the extension plates 20a and 20b, the better the uniformity of the film formation.

In order to prevent a decrease in film thickness on the edge W1 and W2 sides of the substrate W, it is preferable that the extension plates 20a and 20b are wide, but it is sufficient if the width is the same as the spread of the sputtered particles. That is, as shown in Figure 4, when the pitch width of the multiple targets T is Y and the width of the extension plates 20a and 20b is Z, it is preferable that the following relational expression (1) holds true.

Y≦Z≦2Y (1)
For example, if the pitch width Y of the targets T is 200 mm, the width Z of the extension plates 20a and 20b will be approximately 250 to 400 mm.

The upper limit of the width of the extension plates 20a and 20b should be set taking into account the size of the sputtering apparatus 100, and the lower limit should be set so that there is no decrease in film thickness at the edges W1 and W2 of the substrate W. In this way, the width of the extension plates 20a and 20b should be set based on the pitch width of the target T and the size of the sputtering apparatus 100.

In addition, in this embodiment, the example of plate-shaped extension plates 20a and 20b has been described as extension members arranged at the ends of the substrate to extend the surface of the substrate on the film-deposition side, but this is not limited to this. For example, the extension members may be of any shape as long as they have at least one surface that extends the surface of the substrate on the film-deposition side.

Furthermore, although an example has been described in which the surfaces of the extension plates 20a and 20b arranged to contact the respective ends (W1 and W2) of the substrate W are flush with the surface of the substrate W on the film formation side, this is not limited to this. For example, the extension plates 20a and 20b may be arranged behind the substrate W, i.e., in a direction away from the target T. Furthermore, the extension plates 20a and 20b may be arranged so that they are inclined diagonally upward (towards the target T) from the ends W1 and W2 of the substrate W, respectively.

The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention.

2 Vacuum vessel 2a Side wall 3 Substrate holder 4 Target holder 5 Antenna 6 High frequency power supply 9 Insulation section 10 Target bias power supply 12 Insulation cover 15 Reciprocating scanning mechanism (scanning mechanism)
20a, 20b: expansion plate (expansion member)
100 Sputtering device IR High frequency current P Plasma SR Scanning range T Target W Substrates W1, W2 End X Array direction Y Pitch width Z Width of extension plate

Claims (3)

A sputtering apparatus that sputters a target using plasma to form a film on a substrate,
a vacuum vessel that is evacuated and into which a gas is introduced;
a substrate holder that holds the substrate in the vacuum chamber;
a plurality of target holders that hold the targets facing the substrates in the vacuum chamber;
a plurality of antennas arranged in parallel at a distance from a film-forming side surface of the substrate held by the substrate holding unit, and arranged alternately with the targets held by the target holding unit;
an expansion member that expands the film-forming side surface of the substrate,
the extension member is disposed on the substrate holding portion so as to be in contact with or in proximity to an edge of the substrate when the substrate is held by the substrate holding portion ;
a surface of the extension member disposed on the substrate holding part is flush with a film-forming side surface of the substrate held by the substrate holding part,
the plurality of target holders are arranged at equal intervals,
When the pitch width of the target is Y and the width of the extension member is Z, the following relational expression (1) holds:
Y≦Z≦2Y (1)
Sputtering equipment. 2. The sputtering apparatus according to claim 1 , wherein the extension member is disposed on the substrate holding portion so as to contact or be in proximity to all edges of the substrate held by the substrate holding portion. 3. The sputtering apparatus according to claim 1 , further comprising a reciprocating scanning mechanism for reciprocally scanning said substrate holder.