JP2010236051A - Sputtering method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sputtering method by which film hanging of an outer peripheral part of a substrate to be treated is prevented by a simple method so as to uniform a film thickness distribution. <P>SOLUTION: In the sputtering method, at least three pairs of targets are disposed side by side on a same plane, magnetic circuits 301c to 303d are disposed in parallel behind the targets 301a to 303b, powers higher than that of a sputtering power source E2 connected to the pair of targets 302a and 302b sandwiched by the pairs of targets of both ends are supplied from sputtering power sources E1 and E3 connected to the pairs of targets 301a to 301b and 303a to 303b of both ends in the disposed direction according to a prescribed power ratio and magnetic field intensity of both end parts in a direction perpendicular to the magnetic circuit disposed direction is increased. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a sputtering method for forming a thin film on a substrate to be processed, and more particularly to a multi-cathode sputtering method in which a plurality of targets are arranged side by side and a thin film is formed on a substrate to be processed having a large area.

  In recent years, a sputtering technique for forming a thin film on a large-area substrate has become important mainly in the display field such as liquid crystal. In the case where a thin film is formed on a substrate to be processed having a large area by sputtering, a method is adopted in which a plurality of targets are arranged in parallel on the same plane so as to face the substrate to be processed in a vacuum chamber.

  However, when the target surfaces are all arranged in parallel with the substrate to be processed and the film is formed on the substrate to be processed having an outer dimension larger than the overall dimension of the target arranged in parallel, Since the amount of sputtered particles that arrive is insufficient compared to the central portion of the substrate to be processed, there has been a disadvantage that so-called film dripping occurs and the film thickness becomes non-uniform.

  Conventionally, in order to solve such an inconvenience, among the sputtering sources to which the respective targets are attached, the sputtering sources facing both ends of the substrate to be processed are inclined toward the substrate to be processed and reach both ends of the substrate surface. A method of making the film thickness distribution uniform by supplementing the amount of sputtered particles has been proposed (see, for example, Patent Document 1).

  In the prior art described above, since the sputtering sources at both ends are inclined, the mechanism is complicated, and the adjustment of the inclination angle is complicated.

  In the above prior art, a DC sputtering method in which a DC voltage is applied from a sputtering power source has been adopted. In the DC sputtering method, a target is disposed on each cathode electrode, and an anode electrode is disposed between adjacent cathode electrodes. Therefore, the substrate to be processed directly under the anode electrode faces the gap between the targets, and thus the thickness of this portion becomes inconvenient.

  In order to eliminate this inconvenience with a simple structure, in recent years, an AC sputtering method in which an AC power source is connected to each of a plurality of target pairs is frequently used. In the AC sputtering method, since the target pair repeats a cathode potential and an anode potential with each other, it is not necessary to install an anode electrode between the targets, and the above disadvantages do not occur.

  However, in the DC sputtering method, the plasma spreads to the outer periphery of the target to some extent due to the presence of the anode electrode. However, in the AC sputtering method, the potential changes alternately as described above. The electric field strength was lower than that of the portion, the plasma was not spread uniformly, and the supply of sputtering particles was insufficient as compared with the central portion of the substrate to be processed.

  Therefore, in the case where the sputtering method using the sputtering source having the complicated mechanism of the above prior art is not adopted, the film dripping at both ends of the substrate to be processed is more noticeably generated by the AC sputtering method using the AC power source. .

  By the way, in recent years, in order to maintain a higher plasma density on the substrate to be processed, a method called magnetron sputtering that forms a closed-loop magnetic field orthogonal to the electric field formed between the target and the substrate to be processed has been mainstream. It has become. In general, in the magnetron sputtering method, a magnetic circuit composed of a central magnet and an outer peripheral magnet that surrounds the central magnet and has a magnetic pole opposite to the central magnet is arranged in parallel behind the target and arranged in parallel corresponding to each target. ing.

  In magnetron sputtering using an alternating current power source, the magnetic field strength is weakened at both ends of the magnetic circuit in the direction orthogonal to the direction in which the electric field is formed, so that the film dripping occurs due to the electric field strength decreasing. There has been a problem in that film dripping occurs at both ends other than both ends of the substrate, resulting in film dripping over the entire outer periphery of the substrate to be processed.

JP 2004-346388 (8 pages, FIG. 4)

  In view of the above points, an object of the present invention is to provide a sputtering method that prevents film dripping at the outer periphery of the substrate to be processed and makes the film thickness distribution uniform by a simple method.

  In order to solve the above-described problem, the sputtering method of the present invention is arranged such that at least three targets are arranged in parallel on the same plane so as to face a substrate to be processed in a vacuum chamber, and magnetic circuits are arranged in parallel behind the targets. Then, electric power is supplied from the sputtering power source connected to each target to form an electric field between the target and the substrate to be processed to generate plasma, and a magnetic field is formed in a direction orthogonal to the electric field, A sputtering method for forming a thin film on the substrate to be processed by sputtering each of the above targets, from a sputtering power source connected to the targets at both ends in the juxtaposed direction, to the targets at both ends according to a predetermined power ratio It is characterized by supplying a larger electric power than the sputtering power source connected to the sandwiched target.

  According to this method, it is possible to increase the electric field strength of the target surface at both ends in the juxtaposition direction while the targets are juxtaposed on the same plane.

  Further, in place of the at least three targets, at least three target pairs are arranged in parallel on the same plane, the magnetic circuits are arranged in parallel corresponding to each target pair, and each target pair serves as the sputtering power source. If an AC power source is connected to the AC power source and the AC power source connected to the target pair at both ends is supplied with larger power than the AC power source connected to the target pair sandwiched between the target pair at both ends according to a predetermined power ratio, Good.

  When an AC voltage is applied from each AC power source, the two targets constituting each target pair are alternately switched between an anode electrode and a cathode electrode, and a glow discharge is generated between the anode electrode and the cathode electrode, thereby generating the plasma. Can be generated. In this case, according to the predetermined power ratio, the power of the AC power source connected to the target pair at both ends in the juxtaposed direction becomes larger than the power of the AC power source connected to the target pair sandwiched between the target pairs at both ends. It should be set as follows. Note that the predetermined power ratio of the AC power source may be set to a value that does not cause film dripping at both ends of the substrate to be processed and corrects uneven film thickness at both ends and the center.

  By the way, when the electric field strength is increased, the plasma density is improved at both ends of the target in parallel, but the magnetic field strength is reduced at the other end portions of each target. Become lower. For this reason, if the configuration in which the magnetic field strength at the other end is increased is adopted, the plasma density at the other end can be increased, and the plasma density of the entire outer periphery of the substrate to be processed is increased. Differences from plasma density can be corrected. In order to increase the magnetic field strength in this way, for example, auxiliary magnet pieces may be additionally installed at both ends in a direction orthogonal to the parallel arrangement direction of the magnetic circuits.

  As described above, the sputtering method of the present invention can improve the plasma density at both ends of the substrate to be processed facing both ends in the parallel direction of the target without constructing a complicated mechanism. It is possible to prevent dripping of the substrate to be processed and to make the film thickness distribution uniform.

  In addition, when an AC power source is used, an auxiliary magnet piece is additionally installed at the other end of the target, so that the magnetic field strength at the other end of the target can be increased. There is an effect that dripping of the entire film can be prevented.

The block diagram of the sputtering device which enforces the sputtering method concerning this invention. (A) Top view showing a state in which auxiliary magnet pieces are additionally installed, (b) Side view of the state in which auxiliary magnet pieces are additionally installed as viewed from the direction A, (c) B showing a state in which auxiliary magnet pieces are additionally installed. The side view seen from the direction. The graph which shows the change of the film thickness by the presence or absence of correction | amendment of power ratio. The graph which shows the change of the film thickness by the presence or absence of the additional installation of an auxiliary magnet piece.

  Referring to FIG. 1, reference numeral 1 denotes a multi-cathode sputtering apparatus using an AC power source. The sputtering apparatus 1 includes a sputtering chamber 11 that is maintained at a predetermined degree of vacuum using a vacuum exhaust unit (not shown). A substrate to be processed S is disposed in the upper part of the sputtering chamber 11. The substrate S to be processed is sequentially transferred to a position facing a plurality of target pairs, which will be described later, by a substrate transfer means (not shown).

  A gas introduction system 20 is provided in the sputtering chamber 11. The gas introduction system 20 supplies a constant amount of a sputtering gas such as argon or a reactive gas such as oxygen used for reactive sputtering into the sputtering chamber 11 from a gas source 20a through a gas pipe 20c provided with a mass flow controller 20b. It can be introduced at a flow rate.

  A multi-cathode body 30 is disposed in the lower part of the sputtering chamber 11. The multi-cathode body 30 has three target pairs 301, 302, and 303 in which targets formed in the same shape such as a substantially rectangular parallelepiped are paired. Each of the targets 301a and 301b, 302a and 302b, and 303a and 303b constituting the target pair 301, 302, and 303 has a composition of a thin film to be formed on the substrate S to be processed, such as an Al alloy, Mo, or ITO. Accordingly, each is manufactured by a known method and joined to a cooling backing plate (not shown). The target pairs 301, 302, and 303 are juxtaposed so that their unused sputtering surfaces are located on the same plane parallel to the substrate S to be processed.

  The external dimension in which the target pairs 301, 302, and 303 are arranged side by side is set to be larger than the external dimension of the substrate S to be processed.

  On the back surface of each of the targets 301 a to 303 b, electrodes and insulating plates formed in the same outer shape as these targets are respectively attached (not shown) and disposed on the multi-cathode body 30.

  Each of the electrodes is connected to three AC power sources E1, E2, and E3 arranged outside the sputtering chamber 11, so that an AC voltage can be applied to the target pairs 301, 302, and 303, respectively. That is, the target pair 301 will be described as an example. When the AC power supply E1 is connected to the targets 301a and 301b and a negative potential is applied to one of the targets 301a, the target 301b has a ground potential or a positive potential. Is applied to act as an anode. Therefore, the target 301a to which a negative potential is applied is sputtered, and the targets 301a and 302b are sputtered by alternately switching the potential of the target 301a and the target 301b in accordance with the frequency of the AC power supply. Other targets 302a, 302b, 303a, and 303b are sputtered in the same manner as described above.

  The multi-cathode body 30 is provided with magnetic circuits 301c and 301d, 302c and 302d, 303c and 303d behind the targets 301a to 303b, respectively. Each of the magnetic circuits 301c to 303d has a support portion 305 provided in parallel with each of the targets 301a to 303b. A central magnet 306 and outer peripheral magnets 307 and 308 surrounding the central magnet 306 and having magnetic poles opposite to the central magnet 306 are arranged in parallel on the support portion 305. The central magnet 306 and the outer peripheral magnets 307 and 308 are rod-shaped along a direction orthogonal to the parallel arrangement direction of the targets 301a to 303b.

  A closed loop magnetic field is formed on the target surface by the central magnet 306 and the outer peripheral magnets 307 and 308 of each of the magnetic circuits 301c to 303d, and electrons are confined by this magnetic field to generate high-density plasma in this portion.

  And the to-be-processed substrate S is conveyed to the position facing each target 301a-303b, sputtering gas is introduce | transduced into the sputtering chamber 11 by the gas introduction system 20, and each target 301a-303b is passed via each AC power supply E1-E3. When electric power is supplied to the substrate, an electric field perpendicular to each of the targets 301a to 303b is formed, and a magnetic field in a closed loop shape perpendicular to the electric field is formed by each of the magnetic circuits 301c to 303d. The

  At this time, when the power supplied from each of the AC power sources E1 to E3 is the same, the potentials are alternately changed, so that both ends of the target (the targets 301a and 303b in the present embodiment) face each other. The plasma does not spread uniformly to both ends of the substrate to be processed S, and the supply of sputtering particles is insufficient as compared with the central portion of the substrate to be processed S.

  If the supply of the sputtered particles is insufficient, the both end portions of the substrate S to be processed are not sufficiently formed, and so-called film dripping occurs.

  Therefore, among the AC power supplies E1 to E3, the power of the AC power supplies E1 and E3 connected to the target pairs 301 and 303 at both ends in the juxtaposed direction is made larger than E2, and the supply of the sputtering particles at the both ends is performed at the center. It was made uniform with the part.

  According to this method, since the film dripping of the substrate S to be processed can be corrected only by correcting the power ratio of the AC power supplies E1 to E3, it is easy without using a sputtering apparatus having a special structure. By this method, highly reliable film formation becomes possible.

  In FIG. 1, the AC power supply has been described as having three E1 to E3, but the present invention is not limited to this. Even when the number of target pairs to be arranged in parallel increases in accordance with the area of the substrate S to be processed, the film dripping occurs at the both end portions. What is necessary is just to carry out by two alternating current power supplies connected to the target pair.

  In this embodiment, the AC sputtering method in which an AC power source is connected has been described. However, the present invention is not limited to this, and the power of the DC power source connected to the targets at both ends in the juxtaposed direction is not limited to this. The ratio may be corrected.

  FIG. 2 is a schematic view showing a second embodiment of the sputtering method according to the present invention. Hereinafter, parts corresponding to those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the first embodiment described with reference to FIG. 1, when the power ratio of the power source E1 to the power source E3 is corrected and the electric field strength at the both end portions is increased, the plasma density is at both end portions in the parallel arrangement direction of the targets 301a to 303b. Although improved, the plasma density is lower at the other end of each target because the magnetic field strength is lower than at the center.

  In order to increase the plasma density at the other end, the magnetic field strength at each end in the direction orthogonal to the direction in which the magnetic circuits 301c to 303d are arranged may be increased.

  As a method for increasing the magnetic field strength, for example, auxiliary magnet pieces may be additionally installed at the other end portions.

  FIG. 2A shows auxiliary magnet pieces 306a and 306b, 307a and 307b, and 308a and 308b at the other ends of the central magnet 306 and outer magnets 307 and 308 of the magnetic circuits 301c to 303d. It is the figure which looked at the state installed additionally from the upper surface of the sputtering device. Further, the side view from the A direction is shown in FIG. 2B, and the side view from the B direction is shown in FIG. 2C.

  In FIG. 2B, the additional installation of the auxiliary magnet pieces 306a to 308b makes the inclination of the film dripping at both ends of the substrate S to be processed viewed from the direction A, which is improved from F1 to F2. Show.

  FIG. 2 (c) shows that the inclination of the film dripping at both ends of the substrate to be processed S viewed from the B direction has become gentle due to the correction of the power ratio, and has been improved from F3 to F4.

  That is, by correcting the power ratio and reinforcing the magnetic field strength by additionally installing auxiliary magnet pieces 306a to 308b, the sputtered particles at the central portion and all the peripheral portions of the substrate S to be processed are compared with the conventional sputtering method. Can be reached uniformly.

  In this embodiment, the method of correcting the power ratio of the AC power source described in FIG. 1 was performed. The sputtering conditions were such that the pressure in the sputtering chamber being evacuated was 0.3 Pa, seven Al target pairs were juxtaposed, and an AC power source was connected to each target pair.

  The supply power of the AC power source connected to the target pair at both ends of the parallel arrangement direction is 80 kW, the supply power of the five AC power sources sandwiched between the AC power sources at both ends is 75 kW, and as a comparative example, under the same conditions, The power ratio was not corrected, and the power supplied to all AC power sources was 75 kW.

  A graph showing the results of this example is shown in FIG. The horizontal axis indicates the distance on the target substrate in the same direction as the target pair juxtaposition direction as the target substrate X-axis direction (mm), and the vertical axis indicates the film thickness (Å). The measurement position was 922 mm above the Y-axis direction orthogonal to the X-axis direction of the substrate to be processed.

  When the power ratio was corrected, the maximum value of the film thickness was 3062 mm on 882 mm of the substrate to be processed, and the minimum value was 2683 mm on 2378 mm of the substrate to be processed. The average film thickness was 2883 mm, and the film thickness distribution was 6.6%.

  On the other hand, when the power ratio was not corrected, the maximum value of the film thickness was 3084 mm on 1918 mm of the substrate to be processed, and the minimum value was 2526 mm on 2378 mm of the substrate to be processed. The average film thickness was 2878 mm and the film thickness distribution was 9.9%.

  Comparing the film thickness at both ends in the X-axis direction of the substrate to be processed, on one end 22 mm, the film thickness was 2708 mm when the power ratio was corrected, and 2614 mm when the power ratio was not corrected. It was. On the other end 2378 mm, as described above, the minimum values were obtained (when the power ratio was corrected: 2683 mm, when the power ratio was not corrected: 2526 mm).

  As is apparent from the graph of FIG. 3, by correcting the power ratio, the film dripping at both ends in the X-axis direction of the substrate to be processed is improved, and the film thickness distribution is compared with the case where the power ratio is not corrected. Can now be made uniform.

  In this embodiment, a method of reinforcing the magnetic field strength by additionally installing the auxiliary magnet piece described in FIG. The sputtering conditions were the same as in Example 1, with the pressure in the sputtering chamber being evacuated being 0.3 Pa, and an AC power source was connected to each of the seven Al target pairs. The auxiliary magnet pieces were respectively installed at both ends in the direction orthogonal to the direction in which the magnetic circuits are arranged side by side. In the comparative example, no auxiliary magnet piece is additionally installed.

  A graph showing the results of this example is shown in FIG. The abscissa indicates the film thickness (、), and the ordinate indicates the distance on the substrate to be processed in the direction orthogonal to the direction in which the target pairs are juxtaposed, as the Y-axis direction (mm) of the substrate to be processed. The measurement position was 922 mm above the X-axis direction of the substrate to be processed.

  When the auxiliary magnet piece was additionally installed, the maximum value of the film thickness was 3205 mm on 2000 mm of the substrate to be processed, and the minimum value was 2852 mm on 2180 mm of the substrate to be processed. The average film thickness was 3045.7 mm, and the film thickness distribution was 5.8%.

  On the other hand, when no auxiliary magnet piece was additionally installed, the maximum value of the film thickness was 3195 mm on 1900 mm of the substrate to be processed, and the minimum value was 2617 mm on 20 mm of the substrate to be processed. The average film thickness was 3004.3 mm, and the film thickness distribution was 9.9%.

  Comparing the film thickness at both ends in the Y-axis direction of the substrate to be processed, the film thickness is 2864 mm when an auxiliary magnet piece is additionally installed on one end 20 mm, and the minimum value as described above when no additional magnet is installed. (2617 cm). At the other end 2180 mm, when the auxiliary magnet piece was additionally installed, the minimum value (2852 mm) was obtained as described above, and when the additional magnet piece was not additionally installed, it was 2672 mm.

  As is apparent from the graph of FIG. 4, the additional installation of the auxiliary magnet piece improves the film dripping at both ends in the Y-axis direction of the substrate to be processed, and the film is thinner than the case where no additional auxiliary magnet piece is installed. The thickness distribution can be made uniform.

DESCRIPTION OF SYMBOLS 1 Sputtering apparatus 11 Sputtering chamber 20 Gas introduction system 30 Multi-cathode bodies 301 to 303 Target pairs E1 to E3 AC power source S Substrate

Claims (4)

In a vacuum chamber, at least three targets are arranged in parallel on the same plane so as to face the substrate to be processed, and a magnetic circuit is arranged in parallel behind the targets, and power is supplied from a sputtering power source connected to each target. Supplying an electric field between the target and the substrate to be processed to generate plasma, forming a magnetic field in a direction perpendicular to the electric field, and sputtering each of the targets, thereby A sputtering method for forming a thin film on
A sputtering method characterized by supplying a larger electric power from a sputtering power source connected to targets at both ends in the juxtaposed direction than a sputtering power source connected to targets sandwiched between the targets at both ends in accordance with a predetermined power ratio.   Instead of the at least three targets, at least three target pairs are arranged in parallel on the same plane, and the magnetic circuits are arranged in parallel in correspondence with each target pair. A power supply is connected, and from the AC power source connected to the target pair at both ends, according to a predetermined power ratio, larger power is supplied than the AC power source connected to the target pair sandwiched between the target pairs at both ends. The sputtering method according to claim 1.   The sputtering method according to claim 2, wherein the magnetic field strength at both ends in a direction orthogonal to the parallel arrangement direction of the magnetic circuits is increased. The sputtering method according to claim 3, wherein auxiliary magnet pieces are additionally installed at both ends of the magnetic circuit in a direction orthogonal to the parallel arrangement direction to increase the magnetic field strength at the both ends.

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