JP4939009B2 - Target assembly and sputtering apparatus provided with the target assembly - Google Patents

Description

  The present invention relates to a target assembly formed by joining a target and a backing plate, and a sputtering apparatus including the target assembly.

  In the sputtering method, ions in plasma are accelerated and bombarded toward a target formed in a predetermined shape according to the composition of the film to be formed on the surface of the processing substrate, and target atoms are scattered to the surface of the processing substrate. A thin film is formed. In this case, since the target is subjected to ion bombardment and becomes high temperature, the target may be melted or cracked.

  For this reason, the target is bonded to a copper backing plate, for example, via a bonding material made of a material having high thermal conductivity such as indium or tin to form a target assembly. The target is indirectly removed by cooling the backing plate with cooling water (refrigerant).

In this case, in the conventional target assembly, the outer shape of the backing plate is set larger than the outer shape of the target in consideration of increasing the cooling efficiency of the target and considering the mounting to the sputtering cathode by a fixing means such as a bolt. The portion protruding outward from the outer periphery was fixed to the sputtering cathode (Patent Document 1).
JP-A-7-26375 (see, for example, FIG. 1).

  By the way, in recent years, a thin film is frequently formed by a sputtering method on a substrate having a large area such as a glass substrate for manufacturing an FPD. In this case, it is proposed that the sputtering apparatus be configured as follows so that the film thickness distribution and the uniformity of the film quality distribution when performing reactive sputtering can be kept high on a large-area substrate. Has been.

  That is, a plurality of targets formed in the same shape, such as a rectangular parallelepiped, are arranged in parallel to face the substrate, and one AC power source is allocated and connected to two targets adjacent to each other via the AC power source. In addition, a negative potential is applied to one of the targets and a ground potential or a positive potential is applied to the other target, and the target to which the ground potential or the positive potential is applied serves as an anode. Thus, the target to which a negative potential is applied is sputtered, and each target is sequentially sputtered by alternately switching the target potential according to the frequency of the AC power supply (see the specification of Japanese Patent Application No. 2004-69413). In this case, in order to install the targets close to each other, the lateral width of the backing plates in the parallel arrangement direction is made to coincide with the width of the targets in the parallel arrangement direction.

  If the sputtering apparatus is configured as described above, it is not necessary to provide any components such as an anode or a shield between the targets, so that the space where the sputtered particles are not emitted can be made as small as possible (between the targets). There is an advantage that the interval can be reduced, and the film can be formed on a substrate having a large area while maintaining high uniformity of film thickness distribution and film quality distribution.

  However, in the above sputtering apparatus, in order to increase the utilization efficiency of each target, a magnet assembly is provided behind the target, and when the magnet assembly is reciprocated along the parallel direction of the target, plasma generated in front of the target is generated. However, there is a possibility that the bonding surface of the target and the backing plate is exposed to the plasma and the bonding material melts and oozes out between the target assemblies. If the bonding material oozes out, abnormal discharge is induced during sputtering, and good film formation cannot be performed.

  Therefore, in view of the above points, the present invention does not expose the joint surface between the target and the backing plate to the plasma even when sputtering is performed in a state where the target assemblies are arranged side by side. It is an object of the present invention to provide a target assembly capable of preventing the induction of electric discharge and a sputtering apparatus including the target assembly.

In order to solve the above problems, a sputtering apparatus according to the present invention includes a sputtering target having a rectangular shape in plan view and a backing plate having a rectangular shape in plan view bonded to the back side of the sputtering surface of the target via a bonding material. a filter Getto assembly, and a plurality of the target assembly in the vacuum chamber is arranged at a predetermined interval, to those of at least two forming an inner pair of each target to be juxtaposed An AC power supply for applying an AC voltage, and a plurality of magnets that are arranged behind the backing plate to form a magnetic flux in front of the sputtering surface of each target, with the sputtering surface side of the target in front and the back surface as the back. And a magnet assembly so that the magnetic flux is movable in parallel with the target in the direction in which the targets are arranged side by side. In a sputtering apparatus comprising a driving means for driving, the distance between the backing plates bonded to these targets is set larger than the distance between the targets adjacent to each other. The area is smaller than the maximum cross-sectional area of the target .

  According to the present invention, a target assembly in which a target and a backing plate are assembled is attached to a sputtering cathode, and the target is indirectly removed by cooling the backing plate with a refrigerant during sputtering, It prevents melting and cracking. In this case, since the area of the bonding surface between the backing plate and the target is set smaller than the maximum cross-sectional area of the target, a part of the bonding surface between the target and the backing plate is located inside the one end of the target and extends outward. The target side wall prevents the plasma from wrapping around the bonding surface at that location.

  In addition, when the outer shape of the target is a polygon, if the distance between the backing plates is set large over the entire side of the target facing each other, in order to increase the use efficiency of each target, Even when a magnet assembly is provided at the rear and reciprocating along the target parallel direction, the plasma generated in front of the target wraps around between the target parallel to the joint surface between the target and the backing plate. However, the induction of abnormal discharge during sputtering is prevented, and favorable film formation becomes possible.

  The distance from the end surface of the target to the end surface of the backing plate is preferably 5 mm or more. If it is smaller than 5 mm, there is a risk of exposure to plasma when a target is installed adjacently. On the other hand, the upper limit may be within a range in which the target can be cooled during sputtering.

  In this case, the use efficiency of each target may be improved by providing driving means for integrally driving each magnet assembly so that the magnetic flux is movable in parallel with respect to the target.

  As described above, in the target assembly of the present invention and the sputtering apparatus including the target assembly, the bonding surface between the target and the backing plate is not exposed to plasma during sputtering, and as a result, during sputtering. Induction of abnormal discharge can be prevented and good film formation can be achieved.

  Referring to FIGS. 1 to 3, reference numeral 1 denotes a magnetron type sputtering apparatus (hereinafter referred to as “sputtering apparatus”) having a cathode in which the cathode assembly of the present invention is arranged. The sputtering apparatus 1 is of an in-line type, and has a vacuum chamber 11 that can be maintained at a predetermined degree of vacuum via a vacuum exhaust means (not shown) such as a rotary pump or a turbo molecular pump. A substrate transfer means (not shown) is provided in the upper space of the vacuum chamber 11. This substrate transport means has a known structure, for example, has a carrier on which the processing substrate S is mounted, and intermittently drives the driving means to place the processing substrate S at a position facing a parallel target described later. Can be transported sequentially.

  A gas introducing means 2 is provided in the vacuum chamber 11. The gas introduction means 2 communicates with a gas source 23 via a gas pipe 22 provided with a mass flow controller 21, and a sputtering gas such as argon or a reactive gas such as oxygen used in reactive sputtering is supplied to the sputtering chamber 11. It can be introduced at a constant flow rate. A cathode assembly 3 is disposed below the vacuum chamber 11.

  The cathode assembly 3 has six targets 31a to 31f formed in a substantially rectangular parallelepiped shape. Each of the targets 31a to 31f is prepared by a known method according to the composition of a thin film to be formed on the processing substrate S such as Al alloy, Mo, or ITO, and bonded to the backing plates 32a to 32f via the bonding material Bo. The target assembly is attached to the cathode assembly 3 in this state.

  The backing plates 32a to 32f are made of, for example, copper and are formed in a rectangular parallelepiped shape having a water channel therein, and an input portion and an output portion (not shown) of circulating water are provided on one side thereof. As the bonding material Bo, a known material having a high thermal conductivity such as indium or tin is used. During sputtering, the cooling water is circulated in the backing plates 32a to 32f to cool the backing plates 32a to 32f, thereby indirectly removing the targets 31a to 31f, and the targets 31a to 31d due to ion bombardment during sputtering. It prevents melting and cracking of 31f.

  The targets 31a to 31f are juxtaposed such that the unused sputtering surface 311 is positioned on the same plane parallel to the processing substrate S, and the anodes 31a to 31f are disposed between the opposing side surfaces 312 between the anodes 31a to 31f. There are no components such as or shields. The external dimensions of the targets 31a to 31f are set to be larger than the external dimensions of the processing substrate S when the targets 31a to 31f are arranged side by side.

  Six magnet assemblies 33a to 33f are respectively provided behind the targets 31a to 31f. Each magnet assembly 33a to 33f is formed in the same structure, and has a flat plate-like support portion 331 made of a magnetic material provided in parallel to the targets 31a to 31f. On the support portion 331, the lengths of the targets 31a to 31f A bar-shaped central magnet 332 along the direction and a peripheral magnet 333 provided along the outer periphery of the support portion 331 are provided. In this case, the volume when converted to the same magnetization of the central magnet 332 is equal to the sum of the volumes when converted to the same magnetization of the peripheral magnets 333 (peripheral magnet: center magnet: peripheral magnet = 1: 2: 1). It is designed to be.

  As a result, balanced closed-loop tunnel-shaped magnetic fluxes are formed in front of the targets 31a to 31f, respectively, and the ions ionized in front of the targets 31a to 31f and secondary electrons generated by sputtering are captured. The plasma density can be increased by increasing the electron density in front of 31a to 31f.

  Three AC power supplies E1 to E3 for applying an AC voltage are connected to the targets 31a to 31f. In this case, when one AC power source E1 is assigned to two adjacent targets (for example, 31a and 31b) and a negative potential is applied to one target 31a, the other target 31b is grounded. A potential or a positive potential is applied.

  And after processing substrate S is conveyed to the position facing each target 31a-31f arranged in parallel, and predetermined sputtering gas is introduced via gas introduction means 2, for example, via each AC power supply E1-E3 A negative potential is applied to one target 31a, 31c, 31e, and a ground potential or a positive potential is applied to the other target 31b, 31d, 31f. In this case, the other target serves as the anodes 31b, 31d, and 31f, and plasma is generated between the targets 31a to 31f respectively connected to one AC power source E1 to E3, and a negative potential is applied. The targets 31a, 31c, and 31e are sputtered, the potentials of the targets 31a to 31d are switched according to the frequencies of the AC power supplies E1 to E3, and the other targets 31b, 31d, and 31f are sputtered. .About.31 f are alternately sputtered to form a film over the entire surface of the processing substrate S.

  Thereby, since it is not necessary to provide any components such as an anode and a shield between the targets 31a to 31f from which the sputtered particles are not emitted, the region where the sputtered particles are not emitted can be made as small as possible. As a result, the film thickness distribution in the processing substrate S surface can be made substantially uniform.

  When each of the magnet assemblies 33a to 33f is configured as described above, the plasma density above the central magnet 332 is low, and the amount of erosion of the targets 31a to 31f accompanying the progress of sputtering is reduced as compared with the surrounding area. . For this reason, the width | variety along the juxtaposition direction of the targets 31a-31f of the support part 331 was set smaller than the width | variety of the juxtaposition direction of each target 31a-31f. The cathode assembly 3 is provided with the air cylinder 4, the magnet shafts 33a to 33f are attached to the drive shaft 41, and two horizontal positions (L point) along the parallel direction of the targets 31a to 31f. , R point), the magnet assemblies 33a to 33f are integrally reciprocated in parallel to change the position of the tunnel-like magnetic flux M. In this case, the peripheral magnet 333 moves to the outside from the end in the direction in which the targets 31a to 31f are arranged in parallel.

  In order to suppress the occurrence of abnormal discharge, the magnet assemblies 33a to 33f are held at the L point or the R point. For example, film formation on the processing substrate S is completed, and application of an alternating voltage to the targets 31a to 31f is performed. After stopping the discharge and temporarily stopping the discharge, when the next processing substrate S is transported to the position facing the targets 31a to 31f, the air cylinder 4 is driven to bring the magnet assemblies 33a to 33f into a tunnel shape. It is preferable to move the magnetic flux between the point L and the point R. Thereby, it can erode substantially uniformly over the whole surface including the outer periphery part of the targets 31a-31f, and utilization efficiency increases.

  By the way, when the magnet assemblies 33a to 33f are reciprocated as described above, the plasma wraps around from the space between the side surfaces 312 of the targets 31a to 31f to the joint surface between the targets 31a to 31f and the backing plates 32a to 32f. There is a fear. For this reason, it is necessary to prevent the bonding surfaces of the targets 31a to 31f and the backing plates 32a to 32f from being exposed to plasma and melting the bonding material.

  As shown in FIG. 3, in the present embodiment, the targets 31a to 31f adjacent to each other are arranged such that the area of the bonding surface of the backing plates 32a to 32f with the targets 31a to 31f is smaller than the cross-sectional area of the targets. The distances D2 and D3 between the backing plates were set larger than the distance D1 between them (set in the range of 2 mm to 10 mm). In this case, the width Bwc along the juxtaposed direction of the backing plates 32b, 32c, 32d, 32e having a rectangular cross section joined to the four targets 31b, 31c, 31d, 31e in the center among the juxtaposed targets 31a-31f. Is smaller than the width Tw along the parallel arrangement direction of the targets 31b, 31c, 31d, 31e, and the backing plate 32b is equidistant from both ends along the parallel arrangement direction of the targets 31b, 31c, 31d, 31e. , 32c, 32d, and 32e are positioned at both ends so that the distance D2 between the backing plates 32b, 32c, 32d, and 32e is substantially constant.

  The width Bwe along the juxtaposition direction of the backing plates 32a and 32f joined to the targets 31a and 31f located on both sides is equal to the distance D2 between the adjacent backing plates 32b and 32e, and the backing D The outer end surfaces of the plates 32a and 32f are sized so as to be flush with the outer end surfaces of the targets 31a and 31f. On the other hand, the direction (longitudinal direction of the targets 31a to 31f) perpendicular to the parallel arrangement direction of the backing plates 32a to 32f is formed so as to extend outward from the end faces of the targets 31a to 31f. It is made to fix to the cathode assembly 3 by fastening means T, such as a volt | bolt, in the location (refer FIG. 2).

  Thereby, even if the magnet assemblies 33a to 33f are reciprocated between the L point and the R point as described above, the joint surfaces of the targets 31a to 31f and the backing plates 32a to 32f are arranged in parallel with the targets 31a to 31f. The side walls 312 of the targets 31a to 31f, which are located on the inner side of the end along the direction and extend outward, can prevent the plasma from wrapping around the bonding surface, and thus prevent the induction of abnormal discharge during sputtering, Good film formation becomes possible.

  The distances D2 and D3 are 10 mm or more (the ends along the juxtaposed direction of the backing plates 32a to 32f are positioned at an interval of 5 mm or more from the end along the juxtaposed direction of the targets 31a to 31f). ). If it is smaller than 5 mm, the joint surface may be exposed to plasma. Moreover, about an upper limit, what is necessary is just the range which can cool a target during sputtering so that melting and a crack of targets 31a-31f can be prevented.

  Further, when the targets 31a to 31f are provided close to each other as described above, the interval between the magnet assemblies 33a to 33f becomes small. In this case, the magnetic field strength in the vertical direction and the magnetic field in the horizontal direction along the juxtaposed direction of the magnet assemblies 33a to 33f at positions spaced apart from the upper surfaces of the magnets 332 and 333 of the magnet assemblies 33a to 33f. When the strength is measured, the peripheral magnets 333 having the same polarity in the same direction come close to each other and magnetic field interference occurs, and the magnetic flux density at the location is above the peripheral magnets 333 of the magnet assemblies 33a and 33f located at both ends. It becomes higher than the magnetic flux density, and the magnetic field balance is lost.

  Therefore, on both sides of the magnet assemblies 33a to 33f arranged side by side, the rod-shaped auxiliary magnets 5 are respectively matched with the polarities of the peripheral magnet 333 of the adjacent magnet assembly 33a and the peripheral magnet 333 of the magnet assembly 33f. The supporting portion 51 provided and supporting the auxiliary magnet 5 is attached to the drive shaft 41 of the air cylinder 4 so as to move integrally with the magnet assemblies 33a to 33f. Thereby, the magnetic flux density at both ends of the magnet assemblies 33a to 33f can be increased, the magnetic field balance is improved, and as a result, the film thickness distribution in the processing substrate S plane and the film quality distribution when reactive sputtering is performed can be made substantially uniform. .

  In addition, as long as a magnetic field balance can be aimed at when a magnet assembly is arranged in parallel, it is not limited to what provides an auxiliary magnet. For example, the width dimension of only the peripheral magnets located on both outer sides of the magnet assemblies arranged side by side may be increased, or the material may be changed to a material that increases the magnetic flux density generated from the magnets.

  In this example, the sputtering apparatus 1 shown in FIG. 1 was used, a glass substrate (1000 mm × 1200 mm) was used as the processing substrate S, and this glass substrate was transported to a position facing the targets 31a to 31f by the substrate transporting means. Al is used as the targets 31a to 31f, and each target 31a to 31f is formed into a rectangular parallelepiped having an outer dimension of 200 mm × 1700 mm and a thickness of 10 mm by a known method, and bonded to the backing plates 32a to 32f, respectively. Three-dimensional.

  In this case, when In is used as the bonding material and each target assembly 31, 32 is attached to the cathode assembly 3, the distance D1 between the targets 31a to 31f is 2 mm, the distance D2 between the backing plates, D3 was set to 10 mm. Further, the distance between the targets 31a to 31f and the glass substrate was set to 160 mm.

  As sputtering conditions, argon, which is a sputtering gas, is introduced into the vacuum chamber 11 by controlling the mass flow controller 21 of the gas introducing means 2 so that the pressure in the vacuum chamber 11 being evacuated is maintained at 0.3 Pa. did. Moreover, the input power to the targets 31a to 31f by the AC power supply E1 was set to 40 kW, and the frequency was set to 50 kHz. Then, power is applied so that any one of a negative potential and a positive potential or a ground potential is alternately applied to each of the targets 31a to 31f arranged in parallel at a frequency of 50 kHz, and sputtering is performed on one glass substrate. A film was formed. During sputtering, the magnet assemblies 33a to 33f were fixed at the position of the L point.

In the graph shown in FIG. 4, a transition of the number of times of detecting abnormal discharge (number of arcs) with an increase in integrated power when sputtering is performed under the above conditions is indicated by a line E1. In this case, an abnormal discharge is detected when either one of the sputtering current and sputtering voltage during sputtering fluctuates beyond a certain range within a predetermined time (2 minutes). Further, when the integrated power reaches 100 kWh, the sputtering is temporarily stopped and the vacuum chamber is once opened to the atmosphere.
(Comparative Example 1)

  As Comparative Example 1, the sputtering conditions were the same as those in Example 1, but after the target assembly was fabricated, the side surfaces of the target and the backing plate along the parallel direction of the target assembly were covered with copper by thermal spraying. Things were used.

In the graph shown in FIG. 4, a transition of the number of times of detecting abnormal discharge (number of arcs) with an increase in accumulated power when sputtering is performed under the above conditions is indicated by a line C1. In this case, the abnormal discharge is detected in the same manner as in Example 1, and when the integrated power reaches 100 kWh, the sputtering is temporarily stopped and the vacuum chamber is once opened to the atmosphere.
(Comparative Example 2)

  As Comparative Example 2, the sputtering conditions were the same as in Example 1, but the width along the parallel direction of the backing plate was the same as the width along the parallel direction of the target.

  In the graph shown in FIG. 4, a transition of the number of times of abnormal discharge (number of arcs) detected with an increase in integrated power when sputtering is performed under the above conditions is indicated by a line C2. Also in this case, the detection of abnormal discharge is the same as in Example 1, and when the integrated power reaches 100 kWh, the sputtering is temporarily stopped and the vacuum chamber is once opened to the atmosphere.

  If it demonstrates with reference to FIG. 4, the number of times of the detection of abnormal discharge is large in Example 1, the comparative example 1, and the comparative example 2 for reasons, such as oxidation of a target surface at the beginning of sputtering. This is the same when sputtering is started again after the vacuum chamber is once opened to the atmosphere. Here, in Comparative Example 1, the number of detected abnormal discharges decreases and stabilizes as the integrated power increases, and after the vacuum chamber is once opened to the atmosphere, the target covered with copper and the side surface of the backing plate are visually confirmed. However, no arc marks were found.

  However, once the vacuum chamber is opened to the atmosphere, and the sputtering is started again after changing the glass substrate, the number of abnormal discharges detected is not suppressed until the integrated power reaches 100 kWh even if the integrated power increases. After the accumulated power reached about 220 kWh, the sputtering was stopped, the vacuum chamber was opened to the atmosphere, and the target covered with copper and the side surface of the backing plate were visually confirmed, and a plurality of arc marks were observed.

  In Comparative Example 2, the number of detected abnormal discharges is not stable even when the integrated power increases, and after the integrated power reaches 100 kWh, sputtering is stopped, the vacuum chamber is opened to the atmosphere, and the target and backing plate As a result of visual confirmation of the side surface, a plurality of arc marks were observed, and a oozing of the bonding material was also observed.

  On the other hand, in Example 1, after the start of sputtering and once opened to the atmosphere, the number of detected abnormal discharges decreases and stabilizes as the integrated power increases, and each time the vacuum chamber is opened to the atmosphere, the target and backing plate Even when the side surface was visually confirmed, no arc marks were found and no oozing of the bonding material was found.

Sectional drawing which illustrates roughly the structure of the sputtering device of this invention. The top view explaining the structure of a target assembly. Sectional drawing which expands and shows a part of target assembly shown in FIG. The graph which shows the relationship between input electric power and the frequency | count of arc discharge.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Magnetron sputtering apparatus 31a-31f Target 32a-32f Backing plate 33a-33f Magnet assembly E1-E3 AC power supply S Processing board

Claims (3)

A filter Getto assembly and a rectangular shape in plan view of the target and backing plate on the back side bonding material a rectangular shape in plan view which is joined through the sputtering surface of the sputtering target, the target within the vacuum chamber A plurality of assemblies arranged in parallel at a predetermined interval;
An AC power supply that applies an AC voltage to at least two pairs of targets arranged in parallel, and a sputtering surface side of the target in front, and a back surface side in the rear, are arranged behind the backing plate. A magnet assembly composed of a plurality of magnets, each of which forms a magnetic flux in front of the sputtering surface of each target, and a magnet assembly so that the magnetic flux can be translated relative to the target in the direction in which the targets are arranged side by side. In a sputtering apparatus comprising a driving means for driving,
By setting the distance between the backing plates joined to these targets larger than the distance between the targets adjacent to each other, the area of the joint surface is made smaller than the maximum cross-sectional area of the target . A sputtering apparatus characterized by that . Sputtering apparatus according to claim 1, characterized in that set to a large distance between the backing plate each other over one side entire mutually facing targets of the target. The sputtering apparatus according to claim 1 or 2, wherein a distance from an end surface of the target to an end surface of the backing plate is 5 mm or more.

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