JP2010053452A - Sputtering system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sputtering system improved in a film thickness distribution by arranging a gas jet tube is arranged around a cathode case housing a cathode, thereby spreading a process gas uniformly near the center of a substrate. <P>SOLUTION: Among three magnetron cathodes, the cathodes 54a, 54c on both the sides are fitted to a vacuum vessel 32 in such a manner that their angles can be adjusted. After the inside of the vacuum vessel 32 is exhausted to 1×10^4 Pa, a process gas (a gaseous mixture of argon and oxygen) 88 is introduced from a gas jet tube 82 belonging to the cathode case 50. In total, the flow rate of the argon gas is set to 120SCCM and the flow rate of the oxygen gas is set to 90SCCM, and the pressure at the inside of the vacuum vessel is set to 0.7 Pa. Direct current power of 1 kW is fed from respective direct current power sources 72 to the cathodes 54a, 54b, 54c, and a target 78 made of chromium is sputtered, so as to form a chromium oxide thin film on a substrate 10. When a film thickness of 200 nm is obtained, a film thickness distribution reaches ±4%. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to a sputtering apparatus, and more particularly to a sputtering apparatus used for film formation processing of a large substrate.

In the manufacturing process of a liquid crystal display device, there is a step of forming a predetermined thin film on the surface of a relatively large substrate. In forming such a thin film, a sputtering method in which a thin film of a target material is deposited on a substrate by sputtering a target made of a predetermined material is widely used (see, for example, Patent Documents 1 to 7). The substrates of liquid crystal display devices are usually made of glass, and the size of the substrates continues to increase in order to produce as many liquid crystal display devices as possible from a single substrate. Recently, the substrate size is 500 mm × 600 mm or more.

FIG. 9 is a side sectional view of a conventional reactive sputtering apparatus. The substrate 10 is transferred from the load lock chamber (not shown) to the substrate holder 14 through the opening of the gate valve 12 by a transfer robot (not shown). After the vacuum vessel 18 is evacuated to a predetermined pressure by an exhaust system connected to the exhaust port 16, a process gas (from a gas ejection pipe 21 disposed near the periphery of the magnetron cathode 20 (which contains the magnet 23 therein) ( Argon and oxygen mixed gas) is introduced to a predetermined pressure. Then, DC power is supplied from the DC power source 22 to the cathode 20 to generate a discharge in the vacuum vessel 18, and a chromium target 24 is sputtered to form a chromium oxide thin film on the substrate 10.

Japanese Patent Laid-Open No. 06-264239 Japanese Patent Laid-Open No. 09-015585 Japanese Patent Laid-Open No. 10-030175 Japanese Patent Application Laid-Open No. 08-035064 JP-A-11-209872 JP 05-078831 A Japanese Utility Model Publication No. 02-131547

In order to improve the film thickness distribution on the substrate 10, the size of the target 24 is preferably larger than the size of the substrate 10. When the size of the substrate 10 is 500 mm × 600 mm, the size of the target 24 is 600 mm × 700 mm, for example. FIG. 10 is a graph showing the film thickness distribution of the chromium oxide thin film on the substrate when the film is formed on the substrate of the above size. The distance between the target 24 and the substrate 10 is 100 mm. When the average film thickness is 200 nm, the film thickness distribution is ± 8%.

This film thickness distribution is obtained by measuring at 40 mm intervals on the center line 26 of the substrate 10 as shown in FIG. That is, the change in film thickness from one end of the substrate to the other end through the center of the substrate is measured on a center line 26 parallel to the longitudinal direction of the substrate 10 having a size of 500 mm × 600 mm. . The center line 26 is parallel to the transport direction of the substrate 10 in FIG. 9 (the left-right direction in FIG. 9). As shown in FIG. 9, since the gas ejection pipe 21 is arranged near the periphery of the large target 24, even if the process gas is sufficiently supplied near the end of the substrate 10, the gas is near the center of the substrate 10. The film becomes thin due to insufficient supply.

This point will be explained in more detail. In reactive sputtering equipment, a part of the components contained in the process gas (for example, oxygen) is taken into the composition of the thin film (for example, as an oxide), so a process gas at a predetermined flow rate is always supplied near the substrate. There is a need to. However, when the substrate becomes large, a part of the process gas is consumed in the vicinity of the edge of the substrate while the process gas diffuses from the gas ejection tube near the periphery of the cathode toward the center of the substrate. The concentration of the process gas decreases near the center. When the concentration is reduced, the film formation rate is reduced, and the film thickness is reduced near the center of the substrate.

As described above, in the conventional sputtering apparatus, when a film is formed on a large substrate, the supply of process gas to the vicinity of the center of the substrate becomes insufficient, and it is difficult to obtain a good film thickness distribution.

The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a sputtering apparatus that can obtain a good film thickness by uniformizing the supply of process gas when forming a film on a large substrate. It is to provide.

A sputtering apparatus according to the present invention includes an evacuable vacuum vessel, a substrate holder that holds a substrate inside the vacuum vessel, a cathode that is disposed at a position facing the substrate, to which a target is attached, and a cathode case that fixes the cathode. A gas introduction mechanism for introducing a process gas into the interior of the vacuum vessel, and the cathode case can adjust the mounting angle with respect to the vacuum vessel so that the surface of the target attached to the cathode is non-parallel to the surface of the substrate, The gas introduction mechanism includes a gas jet pipe fixed to the cathode case.

By providing the gas ejection pipe around the cathode case in this manner, the process gas is distributed evenly to the vicinity of the center of the substrate as compared with the conventional example in which the gas ejection pipe is provided only in the vicinity of the periphery of a single large cathode. As a result, it is possible to prevent the film thickness from decreasing near the center of the substrate and to improve the film thickness distribution. In addition, since the size of one target is reduced, the present invention is effective even when using a target material that is difficult to manufacture a large target.

As the arrangement of the cathodes, it is preferable to arrange a plurality of elongated rectangular cathodes so that their longitudinal directions are parallel to each other. Thereby, the plurality of cathodes become a large rectangle as a whole.

In the sputtering apparatus of the present invention, since the gas ejection pipe is arranged around the cathode case whose angle can be adjusted with respect to the vacuum vessel, compared with the conventional example in which the gas ejection pipe is provided only in the vicinity of the periphery of a single large cathode. The gas can be distributed uniformly to the vicinity of the center of the substrate, the decrease in the film thickness near the center of the substrate can be prevented, and the film thickness distribution can be improved.

It is a front sectional view showing one embodiment of the reactive sputtering device of this invention. It is the sectional view on the AA line (plan sectional drawing) of FIG. It is a BB sectional view (side sectional view) of Drawing 1. It is an enlarged view of the front cross section of a cathode assembly. It is an enlarged view of the D section of FIG. FIG. 2 is a front cross-sectional view showing a state where the cathodes on both sides are inclined in the reactive sputtering apparatus of FIG. 1. It is a graph of film thickness distribution when forming into a film with the reactive sputtering apparatus of the state of FIG. It is a top view which shows the film thickness distribution measurement line on a board | substrate. It is side surface sectional drawing of the conventional reactive sputtering apparatus. FIG. 10 is a graph of film thickness distribution when the film is formed by the conventional apparatus of FIG. 9. FIG.

FIG. 1 is a front cross-sectional view showing one embodiment of a reactive sputtering apparatus of the present invention. 2 is a cross-sectional view taken along the line AA in FIG. 1 (planar cross-sectional view), and FIG. 3 is a cross-sectional view taken along the line BB in FIG. 1 is a cross-sectional view taken along the line CC of FIG. That is, in FIG. 1, the left cathode assembly 28a of the three cathode assemblies is viewed from the front of the cathode support mechanism 30, and the central cathode assembly 28b is a plane including the center line of the cathode. FIG. 4 is a cross-sectional view taken along the right side, and a cathode assembly 28c on the right side is viewed from between the cathode assembly 28c and the cathode support mechanism.

In FIG. 1, the reactive sputtering apparatus includes three cathode assemblies 28 a, 28 b, and 28 c inside a vacuum vessel 32. As shown in FIG. 2, the cathodes 54a, 54b, 54c of the cathode assemblies 28a, 28b, 28c have an elongated rectangular shape in plan view, and are arranged so that their longitudinal directions are parallel to each other. . In this embodiment, for the substrate 10 having a size of 500 mm × 600 mm, the sizes of the cathodes 54 a, 54 b, 54 c (that is, the target size) in plan view are 200 mm × 700 mm, respectively. By the way, when the dimension W1 of the short sides of the cathodes 54a, 54b, 54c is larger than 200 mm, the shortest inner dimension W2 of the hollow portion of the annular gas ejection pipe 82 is further expanded, thereby making the process gas uniform. The effect that can be spread over is reduced. Accordingly, the short side dimension W1 of the cathode is preferably set to 200 mm or less. On the other hand, the lower limit of the short side dimension W1 is about 50 mm. Therefore, the short side dimension W1 is preferably in the range of 50 to 200 mm. Returning to FIG. 1, there is a substrate holder 34 below the cathode assemblies 28a, 28b, 28c, on which the substrate 10 can be held. The distance between the target 78 and the substrate 10 is 80 to 120 mm. The vacuum vessel 32 is provided with a gate valve 33 for carrying the substrate 10 and an exhaust port 35 connected to an exhaust system.

Next, the structure of the cathode assembly will be described. FIG. 4 is an enlarged view of a front cross section of the central cathode assembly 28b. The other two cathode assemblies 28a and 28c have the same structure. The top plate 36 of the vacuum vessel has a rectangular opening 38, and a cathode mounting plate 40 is fixed with bolts so as to cover the opening 38. The cathode mounting plate 40 and the top plate 36 are vacuum sealed with an O-ring 42. A circular opening 44 is provided at the center of the cathode mounting plate 40, and the upper end of the bellows 46 is joined to the inner periphery of the opening 44. The lower end of the bellows 46 is joined to a hollow disk-like cathode support 48. A cathode case 50 is fixed to the lower surface of the cathode support 48 with bolts. The cathode support 48 and the cathode case 50 are vacuum sealed with an O-ring 52. The cathode case 50 is grounded via the cathode support 48, the bellows 46, the cathode mounting plate 40 and the top plate 36. As will be described later, the bellows 46 is for absorbing a change in the distance between the cathode support 48 (inclined with the cathode case 50) and the top plate 36 when the cathode case 50 is inclined.

A magnetron cathode 54 b is arranged inside the cathode case 50. The back surface of the cathode 54b and the inner surface of the cathode case 50 are electrically insulated by a ceramic first insulating stone 56, and a pipe 58 (joined integrally with the cathode 54b) that supports the cathode 54 is used. The outer surface and the inner surface of the opening of the cathode case 50 are electrically insulated by a ceramic second insulating stone 60. The space between the second insulating stone 60 and the pipe 58 is vacuum-sealed with an O-ring 62, and the space between the second insulating stone 60 and the cathode case 50 is vacuum-sealed with an O-ring 64. A screw 66 is formed on the outer periphery of the upper portion of the pipe 58. The cathode 54 b can be fixed to the cathode case 50 by tightening the first nut 68 on the screw 66.

A second nut 70 is further engaged with the screw 66 of the pipe 58, and a DC power source 72 is connected to the second nut 70. DC power can be supplied from the DC power source 72 to the cathode 54b.

A magnet 55 is accommodated in the cathode 54b. A target 78 is fixed to the surface side (the lower side of the drawing) of the cathode 54b. Two water cooling tubes 74 pass through the pipe 58. The cooling water 76 passing through the water cooling pipe 74 flows inside the cathode 54 b and cools the target 78. The peripheral edge of the target 78 is covered with a target shield 80. The target shield 80 is fixed to the cathode case 50.

A gas ejection pipe 82 is fixed around the cathode case 50 so as to surround the cathode case 50. The gas ejection pipe 82 has a substantially rectangular annular structure as shown in FIG. Returning to FIG. 4, the gas ejection pipe 82 has a large number of gas ejection holes 84. A metal flexible tube 86 is connected to the gas ejection pipe 82. The process gas 88 enters the gas ejection pipe 82 through the flexible tube 86 and exits from the gas ejection hole 84 into the vacuum container. The flexible tube 86 is for absorbing the change in the distance between the gas ejection pipe 82 (inclined with the cathode case 50) and the top plate 36 when the cathode case 50 is inclined as will be described later. The gas introduction mechanism of this reactive sputtering apparatus includes three gas ejection pipes 82 and three flexible tubes 86 connected thereto.

Next, a structure for supporting the cathode assembly so as to be adjustable in angle will be described. As shown in FIG. 2, in the vacuum vessel 32, two horizontally elongated support plates 90 and 91 are arranged in parallel and spaced apart from each other. As shown in FIG. 1, both ends of the support plates 90 and 91 are fixed to the top plate 36 of the vacuum vessel 32 by a fixing plate 92 extending in the vertical direction. In FIG. 2, three cathode support mechanisms 30 with fixing screws are fixed on one support plate 90, and three cathode support mechanisms 31 without fixing screws are on the other support plate 91. Is fixed. As shown in FIG. 3 (cross-sectional view taken along the line BB in FIG. 1), one cathode assembly is supported by a pair of cathode support mechanisms 30 and 31 so that the angle can be adjusted.

FIG. 5 is an enlarged view of a portion D in FIG. The cathode support mechanism 30 includes a housing 94, a bearing 96, and a fixing screw 98. The housing 94 is fixed on the support plate 90. On the other hand, shafts 51 are fixed to end faces at both ends in the longitudinal direction of the cathode case 50. A bearing 96 is provided inside the housing 94, and the shaft 51 is rotatably supported by the bearing 96. A fixing screw 98 is engaged with the housing 94. When the fixing screw 98 is screwed in, the tip of the fixing screw 98 is pressed against the end surface of the shaft 51, and the shaft 51 is fixed to the housing 94. When the fixing screw 98 is loosened, the shaft 51 becomes rotatable with respect to the housing 94. That is, when the fixing screw 98 is loosened, the cathode case 50 can be inclined as will be described later. Thereby, the attachment angle of the cathode with respect to a vacuum vessel can be adjusted. In FIG. 3, the right-side cathode support mechanism 31 is not provided with a fixing screw.

Next, the inclination of the cathode will be described. FIG. 6 shows a state in which the cathodes on both sides are inclined in the reactive sputtering apparatus of FIG. The left cathode 54a is inclined from the horizontal state by an angle θ around the center line of the shaft 51 in the counterclockwise direction. That is, the left cathode 54a is inclined such that the direction of the normal line 79a of the surface of the target attached to the cathode 54a is inclined toward the center of the substrate 10. In this state, the surface of the target attached to the cathode 54 a is not parallel to the surface of the substrate 10. On the other hand, the right cathode 54c is inclined from the horizontal state by the same angle θ in the clockwise direction. With respect to the cathode 54c on the right side, the direction of the normal line 79c of the target surface is inclined toward the center of the substrate 10, and the target surface becomes non-parallel to the surface of the substrate 10. The angle θ is set to 5 degrees in this embodiment. The central cathode 54b remains horizontal. Thus, the thickness distribution on the substrate 10 is improved by inclining the targets on both sides inward from the horizontal state.

When three cathodes are provided as in this embodiment, the mounting angle can be adjusted for at least the cathodes on both sides. Since the central cathode is not normally inclined, the mechanism for adjusting the mounting angle can be omitted. When a plurality of elongated rectangular cathodes are arranged in parallel, the number of cathodes can be any number of 2 or more, but at least two cathodes on both sides (all cathodes when there are two cathodes) It is preferable to provide a mechanism for adjusting the mounting angle.

Next, the operation of this reactive sputtering apparatus will be described. In FIG. 6, a substrate 10 is transferred from a load lock chamber (not shown) to a substrate holder 34 through an opening of a gate valve 33 by a transfer robot (not shown). After the gate valve 33 is closed, the vacuum chamber 32 is exhausted to “1 × 10 minus fourth power” Pa by the exhaust system connected to the exhaust port 35. Then, a process gas (a mixed gas of argon and oxygen) 88 is introduced from each gas ejection pipe 82 attached to the cathodes 54a, 54b, 54c. In total, the flow rate of argon gas is 120 SCCM, the flow rate of oxygen gas is 90 SCCM, and the pressure in the vacuum vessel is set to 0.7 Pa from the three gas ejection pipes 82. Then, 1 kW DC power is supplied from each DC power source 72 to each of the three magnetron cathodes 54a, 54b, 54c to generate a discharge in the vacuum vessel 32, and a chromium target 78 is sputtered to form a substrate. A chromium oxide thin film is formed on 10. When the film is formed under such conditions, a chromium oxide thin film having a thickness of 200 nm can be obtained by sputtering for 20 minutes. In this case, since the gas ejection pipes 82 are provided around the respective cathodes, the film thickness distribution is improved. Further, since the cathodes 54a and 54c on both sides are inclined inward, the film thickness distribution is further improved.

FIG. 7 is a graph showing the film thickness distribution of chromium oxide on the substrate when the film is formed under the above-described conditions in the reactive sputtering apparatus in the state of FIG. 6 (the cathodes on both sides are inclined). This film thickness distribution is measured at intervals of 40 mm on the center line 26 of the substrate 10 as shown in FIG. That is, the change in film thickness from one end of the substrate to the other end through the center of the substrate is measured on a center line 26 parallel to the longitudinal direction of the substrate 10 having a size of 500 mm × 600 mm. . The center line 26 is parallel to the transport direction (the left-right direction in FIG. 1) of the substrate 10 in FIG. When the average film thickness was 200 nm, the film thickness distribution was ± 4%. The distance between the target and the substrate is 100 mm. As described above, the film thickness distribution was improved as compared with the film thickness distribution of FIG. 10 in the conventional apparatus. The following two points can be cited as reasons why the film thickness distribution is improved. (1) Since three cathodes are provided and gas ejection pipes are provided around each cathode, the process gas is transferred to the substrate as compared with the conventional example in which gas ejection pipes are provided only in the vicinity of the periphery of a single large cathode. It became possible to spread evenly to the vicinity of the center, and it was possible to prevent the film thickness from decreasing near the center of the substrate. (2) By tilting the cathodes on both sides inward, the particles flying from the cathodes on both sides are likely to gather at the center of the substrate, and a reduction in film thickness near the center of the substrate can be prevented.

Therefore, in order to examine how the above two factors contribute to the improvement of the film thickness distribution, the other conditions are the same as the above film forming conditions without tilting the cathodes on both sides. A chromium oxide thin film was formed on the substrate. As a result, the film thickness distribution was ± 5% when the average film thickness was 200 nm. Accordingly, the film thickness distribution (± 8%) obtained with the conventional apparatus was improved to ± 5% by arranging gas ejection pipes around the plurality of cathodes, and the cathodes on both sides were further improved. By tilting, it is improved to ± 4%. From this, it can be seen that the effect of improving the film thickness distribution by arranging the gas ejection pipes around the plurality of cathodes is larger than the effect of improving the film thickness distribution by inclining the cathodes on both sides.

10 Substrate 28a, 28b, 28c
Cathode assemblies 30, 31 Cathode support mechanism 32 Vacuum vessel 34 Substrate holder 46 Bellows 50 Cathode cases 54a, 54b, 54c
Cathode 72 DC power supply 78 Target 82 Gas ejection pipe 86 Flexible tube 88 Process gas

Claims (4)

An evacuable vacuum vessel,
A substrate holder for holding a substrate inside said vacuum vessel,
A cathode disposed at a position facing the substrate and to which a target is attached ;
A cathode case for fixing the cathode;
In scan sputtering apparatus provided with a gas introduction mechanism for introducing a process gas into said vacuum container,
The cathode case can adjust the mounting angle with respect to the vacuum vessel so that the surface of the target attached to the cathode is not parallel to the surface of the substrate,
The gas introduction mechanism, features and be away sputtering apparatus that includes a gas injection tube, which is fixed to the cathode case. Before ask Sword is a cathode fine long rectangular, the rectangular cathode, spatter ring according to claim 1 you, characterized in that the longitudinal direction is more parallel to each other apparatus. Scan sputtering apparatus according to claim 2 you, wherein a length of the rectangular cathode of the short side is in the range of 50 to 200 mm. Before SL cathode casing is connected to the vacuum container by a bellows, wherein the gas jet pipe which is fixed to the cathode casing with adjustable mounting angle, the process through the vacuum vessel disposed inside a metallic flexible tube scan sputtering apparatus according to claim 1 or 2 you characterized by receiving a supply of gas.