JP5157101B2 - Gas supply apparatus and substrate processing apparatus - Google Patents

Description

  The present invention uses, for example, a gas supply device that supplies a processing gas into a processing container from a large number of gas supply holes facing the substrate in order to perform a predetermined film forming process on the substrate, and the gas supply device. The present invention relates to a substrate processing apparatus.

  One of the semiconductor manufacturing processes is a film forming process, and this process is usually activated by, for example, plasmaizing or thermally decomposing a processing gas in a vacuum atmosphere to deposit active species or reaction products on the substrate surface. Is done. In the film formation process, there is a process of forming a film by reacting a plurality of types of gases. As this process, a metal such as Ti, Cu, or Ta, a metal compound such as TiN, TiSi, or WSi, or The formation of a thin film such as an insulating film such as SiN or SiO 2 can be mentioned.

  An apparatus for performing such a film forming process includes a mounting table for mounting a substrate in a processing container forming a vacuum chamber, a gas supply device provided in the processing container, and energy to the gas. A heating device, plasma generating means, and the like, which are means for giving, are provided in combination. The gas supply device is generally called a gas shower head, and is provided so as to close an opening formed in the ceiling portion of the processing container and to face the mounting table. As for a more specific structure of the gas supply device, a gas diffusion space is formed in a flat cylindrical body, a shower plate having a large number of gas supply holes is arranged on the lower surface, and processing gas diffuses from the outside. The gas flows into the space and is blown out from the gas supply hole to the processing space.

  The shower plate has a uniform number of gas supply holes per unit area so that gas can be uniformly supplied onto the substrate. As an arrangement pattern of the gas supply holes, a pattern arranged in a matrix form vertically and horizontally as shown in FIG. 10 and a pattern arranged at equal intervals on concentric circles as shown in FIG. 11 are known. Are described in Patent Document 1 and Patent Document 2, respectively. 10 and 11, 1 is a shower plate and 11 is a gas supply hole. In an actual shower plate used for a 300 mm wafer, the diameter of the gas supply holes is smaller, and the number of holes and the number of concentric circles are larger.

  Incidentally, in the process of forming a Ti film on a semiconductor wafer (hereinafter referred to as a wafer) using a mixed gas of TiCl4, H2 and Ar, particles on the wafer were evaluated. As shown in FIG. In addition, it has been found that a region where particles 12 are excessively adhered on the wafer W is formed in a cross shape. This cross-shaped particle adhesion pattern P (actually dense particles are shown by hatching for convenience) is when the flow velocity of the gas flowing from the shower plate 1 into the processing atmosphere is increased. It occurs when the flow rate is exceeded, and the generation point shifts to the higher flow rate as the overall gas flow rate increases. In other words, if the gas flow rate is reduced, a cross-shaped particle adhesion pattern is generated even at a low flow rate.

  As a result of various studies on this reason, it was found that the gas flow from the central part of the wafer toward the outer peripheral part is related to the flow velocity distribution in the circumferential direction. That is, since this type of film forming apparatus exhausts at the lower part of the processing container, the gas flow on the wafer surface is dominant from the central part toward the outer peripheral part. There is a region where the gas flow velocity is extremely slow. For example, for the shower plate 1 in which the gas supply holes 11 are arranged in a matrix, the gas supply holes 11 are parallel from the center of the shower plate 1 toward the outer periphery, that is, in the radial direction, as shown in FIG. There are regions that are lined up in a straight line.

  In FIG. 13, only one region is shown. However, on the shower plate 1, this region is shifted 90 degrees from the center and extends in four directions, and has a cross shape as a whole. Focusing on the area within the frame, if expressed in a macro manner, gas is not blown to the part facing the inside of the frame on the wafer W side, so the gas at the part toward the outer periphery from the center C of the wafer W The flow velocity of the flow A is extremely slower than the flow velocity of the gas flow on both sides. When a region having a high flow velocity and a region having a low flow velocity are adjacent to each other, turbulent flow is generated at the boundary portion, and as a result, product deposition occurs abnormally, in other words, Ti grows abnormally. Thus, the locally abnormally grown portion is an aggregate region of particles when viewed from other regions, and adversely affects the electrical characteristics of the chip including this region. It is intuitively understood that the faster the flow rate of the gas flow blown out from the shower plate 1, the greater the degree of turbulent flow at the boundary, and the more likely the cross-shaped particle adhesion pattern P is likely to occur. Consistent with experimental results.

  It can be easily imagined that the above phenomenon occurs even when the gas supply holes are arranged at equal intervals on the concentric circles. That is, even in this case, there are ten regions in which the gas supply holes 11 are arranged in parallel and linearly from the center portion of the shower plate 1 toward the outer peripheral portion.

As described above, in the conventional shower plate, since the cross-shaped particle adhesion pattern P is generated depending on the process condition, there is a problem that the degree of freedom in setting the process condition is limited. For example, there is a disadvantage that the gas flow rate cannot be set large in order to improve the throughput.
Patent Document 1 and Patent Document 2 do not have such attention at all, and the shower plate described in these documents is adopted from the viewpoint that the number of gas supply holes per unit area is uniform and the design is easy. Is.

Japanese Patent Laid-Open No. 5-152218: FIG. JP 2004-76023 A: FIG. 22, paragraph 0100

  The present invention has been made under such circumstances, and an object of the present invention is to provide a gas supply device for supplying a processing gas into a processing container, in a circumferential direction with respect to a gas flow from the central portion of the substrate toward the outer peripheral portion. It is an object of the present invention to provide a shower plate and a substrate processing apparatus using the shower plate that can suppress the generation of particles and expand the degree of freedom of process conditions.

The present invention provides a shower plate that is arranged to face a mounting table in order to supply processing gas into a processing container provided with a mounting table on which a substrate is mounted, and has a large number of gas supply holes. In the gas supply device provided,
The gas supply holes are arranged circumferentially at equal intervals on a number of concentric circles, and the number of concentric gas supply holes on the outer and outer concentric circles is equal to the number of concentric gas supply holes on the outer side. Arranged to increase ,
The arrangement pattern of the gas supply holes is:
B) For any concentric circle except the outermost and innermost circumferences, the gas supply holes on the concentric circles and the gas supply holes immediately adjacent to the concentric circles adjacent to the inside and the concentric circles adjacent to the outside are on the radius of the concentric circles. Configured not to line up,
B) Arrange one gas supply hole among the gas supply holes arranged on each concentric circle so as to be arranged on the radius of the concentric circle, and form an algebraic spiral curve in which the gas supply holes arranged on the radius extend from the center of the concentric circle. The arrangement pattern is the same as the arrangement pattern formed by rearranging the arrangement pitches in the circumferential direction at equal intervals so as to be arranged along the line .
The gas supply hole arrangement pattern preferably has the same number of gas supply holes per unit area (for example, a square area of 2 cm × 2 cm).

  The present invention can also be used as a substrate processing apparatus, for example, a film forming apparatus. This apparatus is provided with an airtight processing container, a mounting table provided in the processing container, and a gas in the processing container. An exhaust means for exhausting the gas supply apparatus according to the present invention is provided, and the substrate on the mounting table is processed with a processing gas supplied from the gas supply apparatus.

  In the present invention, the gas supply holes of the shower plate are arranged on a number of concentric circles, and the gas supply hole arrangement pattern is such that the gas supply holes on the concentric circles are adjacent to the concentric circles adjacent to the inside and the concentric circles adjacent to the outside. The arrangement pattern of the gas supply holes is set so that the supply holes are not aligned on the radius of the concentric circle. For this reason, a strip-like so-called dead space extending in the radial direction of the concentric circles and not including the gas supply holes is not formed, so the flow rate of the gas flow from the center of the concentric circles toward the outer periphery of the shower plate is extremely slow. Formation of the region is suppressed. As a result, it is possible to prevent a problem that an abnormal process is performed in a region extending in a specific direction when viewed from the center of the substrate, like the above-described cross-shaped particle adhesion pattern. Conventionally, such a problem can be avoided by adjusting the process conditions. However, in the present invention, the restriction of the process conditions is relaxed, so that the degree of freedom in setting the process conditions is widened. It is possible to set conditions such as increasing the number.

  An embodiment in which the gas supply apparatus of the present invention is incorporated in a film forming apparatus for forming a film by plasma CVD will be described. First, the general configuration of the film forming apparatus will be described based on the schematic diagram of FIG. In FIG. 1, reference numeral 2 denotes a processing vessel which is a vacuum chamber made of, for example, aluminum. The processing vessel 2 has a so-called mushroom shape in which a cylindrical portion 2a having a large diameter on the upper side and a cylindrical portion 2b having a small diameter on the lower side are continuously provided. And a heating mechanism (not shown) for heating the inner wall is provided. In the processing container 2, a stage 21 is provided as a substrate mounting table for horizontally mounting, for example, a semiconductor wafer (hereinafter referred to as a wafer) W, which is a substrate, and this stage 21 is supported on the bottom of the small diameter portion 2b. It is supported via the member 22.

  In the stage 21, a heater (not shown) that forms a temperature adjusting means for the wafer W and a conductive member (not shown) that becomes a lower electrode described later are provided. An electrostatic chuck (not shown) for electrostatically adsorbing the wafer W is provided as necessary. Further, the stage 21 is provided with, for example, three support pins 23 for holding and lifting the wafer W so as to be able to protrude and retract with respect to the surface of the stage 21. It is connected to an elevating mechanism 25 outside the processing container 2. One end of an exhaust pipe 26 is connected to the bottom of the processing container 2, and a vacuum pump 27, which is a vacuum exhaust means, is connected to the other end of the exhaust pipe 26. A transfer port 29 that is opened and closed by a gate valve 28 is formed on the side wall of the large diameter portion 2 a of the processing container 2.

  Furthermore, an opening 31 is formed in the ceiling of the processing container 2, and a gas shower head 4 that is a gas supply device of the present invention is provided so as to close the opening 31 and face the stage 21. Here, the gas shower head 4 and the stage 21 also serve as an upper electrode and a lower electrode, respectively. The gas shower head 4 is connected to the high-frequency power supply unit 33 through the matching unit 32, and the stage 21 serving as the lower electrode is Grounded. In FIG. 1, the wiring diagram is shown in a simplified manner. Actually, however, the stage 21 is electrically connected to the processing container 2 and grounded from above the processing container 2 through a matching box (not shown). A conductive path surrounds the processing space.

  As shown in FIG. 2, the gas shower head 4 is provided on the lower side of the bottom portion of the base member 41 and a base member 41 made of a flat bottomed cylindrical body that closes the upper opening of the processing container 1. Shower plate 5. Since the base member 41 also has a role of partitioning the vacuum atmosphere and the atmospheric atmosphere in the processing container 1, the flange portion 42 at the upper peripheral edge and the peripheral edge 43 of the opening of the processing container 1 are ring-shaped resin seal members. The O-ring 44 is airtightly joined.

  Further, two gas supply pipes 61 and 62 are connected to the central portion of the base member 41, and the gas supply holes 7 (7a) of the shower plate 5 from which the gases of the gas supply pipes 61 and 62 are separated, respectively. And 7 (7b). That is, a diffusion plate 64 having a space 63 communicating with one gas supply pipe 61 is laminated on the shower plate 5, and the upper side of the diffusion plate 64 communicates with the other gas supply pipe 62. In addition, the space 63 is formed as a partitioned space 65. One gas supply hole 7 (7a) communicates with the space 63, and the other gas supply hole 7 (7b) communicates with the space 65. The shower plate 6 will be described in detail later.

  The one gas supply pipe 61 is connected to, for example, a TiCl4 gas source 102, an Ar gas source 103, and a ClF3 gas source 104 as shown in FIG. 1, and the other gas supply pipe 62 is connected to, for example, an H2 gas source 106 and An NH3 gas source 107 is connected. Note that a portion indicated by 108 surrounded by a chain line is a group of gas supply devices such as valves and mass flow controllers provided in each gas supply path.

  Next, the shower plate 5 will be described in detail. The shower plate 5 in this example is used for a 300 mm wafer, and is equally spaced along 19 concentric circles 51 centering on the center of a circular plate body 50 as shown in FIGS. The gas supply hole 7 is drilled, and the gas supply hole 7 is drilled at the center of the concentric circle (the center of the shower plate 5). The gas supply holes 7 include gas supply holes 7a and 7b through which different gases blow out, but these gas supply holes 7a and 7b are alternately arranged in the circumferential direction. It will be described as hole 7. The diameter of the gas supply hole 7 is 1 mm, for example. In the 19 concentric circles 51, the radius of the outermost concentric circle 51 is 163 mm, and the intervals between the concentric circles are set to be equal. About the number of gas supply holes 7 of each concentric circle 51, 8, 12, 18, 24, 30, 36, 42, 48, 54, 60, 66, 72, 78, 84, 90, 96, 102, from the inside. 108 and 114.

Regarding the design method of the arrangement pattern of the gas supply holes 7, first, the gas supply holes 7 of the concentric circles 51 are once arranged so as to be aligned on the radii of the concentric circles 51, and then, as shown in FIG. Can be formed by rearranging the arrangement pitches in the circumferential direction at equal intervals so that the gas supply holes 7 arranged in a row are arranged along the algebraic spiral curve S extending from the center of the concentric circle 51.
The algebraic spiral curve S is an Archimedean spiral curve represented by r = aθ, where r and θ are distances in polar coordinates and the angle from the reference direction with the center of the concentric circle 51 as the zero point, and a is a variable.

  Regarding the arrangement pitch of the gas supply holes 7 in each concentric circle 51 and the setting of the algebraic spiral curve S, the arrangement density of the gas supply holes 7 in the minute region extending in the radial direction of the concentric circle 51 is made uniform between the respective directions. Do. That is, as shown in FIG. 6, a band-like region (elongated rectangular region) L that does not include the center C of the concentric circle 51 but includes the innermost concentric circle 51 and the outermost concentric circle 51 in the circumferential direction. The number of gas supply holes 7 in the belt-like region L at each angular position is measured, and the distribution of the number is acquired. FIG. 7 shows the distribution of the number of gas supply holes obtained by rotating the belt-like region L from 1 degree to 90 degrees. The width 2d of the belt-like region L corresponds to the angular resolution, and at least the width 2d is the arrangement pitch. For example, it is set to 4 mm so as to be below. As shown in FIG. 7, the number of the gas supply holes 7 at each angular position is within 15-20.

  The gas supply holes 7 are arranged so that the number of the gas supply holes 7 per unit area is uniform. Per unit area means that when the region in the outermost concentric circle 51 is divided into squares of 2 cm × 2 cm, for example (excluding the region in contact with the outermost concentric circle 51), the gas supply holes between the divided regions In this example, the minimum value of the number of holes in each divided region is five, and the maximum value is seven.

  The processing of the wafer W in the film forming apparatus of FIG. 1 will be described. First, a wafer W, which is a substrate, is loaded into the processing container 2 through a transfer port 29 with the gate valve 28 opened by a transfer arm (not shown), and is transferred onto the stage 21 by a cooperative action with the support pins 23. After the gate valve 28 is closed, a mixed gas of TiCl 4 gas and Ar gas, which is the first gas, is sent from the gas supply sources 102 and 103 to the gas shower head 4 through the gas supply pipe 61, and the gas supply source 106 H 2 gas as the second gas is sent to the gas shower head 4 through the gas supply pipe 62. Then, the first gas and the second gas are separately supplied to the processing atmosphere from the gas supply holes 7 (7a) and (7b) of the shower plate 5.

  On the other hand, the inside of the processing vessel 2 is evacuated by the vacuum pump 27, and a pressure adjusting valve (not shown) provided in the exhaust pipe 26 is adjusted to set the pressure in the processing vessel 2 to a set pressure. The high-frequency power is supplied between the gas shower head 4 and the stage 21 which is the lower electrode, the processing gas, that is, the first gas and the second gas are turned into plasma, and TiCl4 is reduced by H2 to reduce the wafer W. A Ti film is formed on the surface. At this time, the reaction by-product HCl is exhausted together with the unreacted gas.

  In some cases, the Ti film is nitrided to form the TiN film following the Ti film formation. In this case, the supply of the TiCl4 gas as the first gas and the H2 gas as the second gas is stopped. At the same time, the supply of NH3 (ammonia) gas is started. Also at this time, high-frequency power is supplied to the processing space, and the surface of the Ti thin film already formed on the wafer W is nitrided by NH3 active species. After the nitridation is completed, the supply of high frequency power and the supply of NH3 gas are stopped, and then the wafer W is unloaded from the processing container 2 by an operation reverse to the above-described loading operation.

  The effect of the shower plate 5 will be described. The conventional shower plate has focused only on the number of gas supply holes per unit area, but in the shower plate 5 of the above-described embodiment, the gas flow from the center to the outer periphery is dominant on the wafer W. Focusing on the relationship between the occurrence of a region in which the flow velocity of the gas flow in the radial direction (generally including the radial direction as apparent from FIG. 10) becomes extremely slow and the arrangement pattern of the gas supply holes 7, It is devised so that the flow velocity of the gas flow in each direction is almost uniform as seen from the section.

  Specifically, the number of gas supply holes 7 is arranged on a large number of concentric circles 51, and the gas supply holes 7 are arranged at equal intervals for each concentric circle 51. The reason why the intervals are equal is to make the number of the gas supply holes 7 uniform per unit area. In order to eliminate the strip-shaped blank area shown in FIG. 12 in the background art column, an arbitrary concentric circle 51 excluding the outermost and innermost circumferences is adjacent to the gas supply hole 7 on the concentric circle 51 and inside. The concentric circle 51 and the adjacent gas supply holes 7 of the concentric circles 51 adjacent to each other on the outside do not line up on the radius of the concentric circle 51, that is, in the concentric circles 51 adjacent to each other, the three gas supply holes 7 should be on the radius. Design so that it does not. In order to obtain such an arrangement pattern, in this embodiment, the gas supply holes 7 of the concentric circles 51 are shifted using a spiral curve as described above.

  FIG. 8 is obtained by rotating the belt-like region L shown in FIG. 6 in the circumferential direction by 1 degree and calculating the flow velocity from the central part of the concentric circle 51 in the belt-like region L toward the outer periphery for each angular position. It shows the flow velocity distribution in the circumferential direction. Specifically, the shower plate is divided into three concentric circles by four circles having radii of 170 mm, 120 mm, 60 mm, and 40 mm, and a, b, and c indicate flow velocity distributions in these divided regions, respectively. For the flow velocity distribution, the flow rate per unit area is determined from the number of gas supply holes 7 existing in each of the three divided regions, and the flow rate and the number of gas supply holes 7 in the band-like region at the corresponding angle are obtained from The flow velocity in each angular region (band-like region L) was calculated.

  This flow velocity distribution corresponds to the distribution of the number of gas supply holes shown in FIG. 7, and it can be seen that the flow velocity in each direction is uniform. FIG. 9 shows a flow velocity distribution in the plane on the wafer W, which is obtained by color coding and copied as a black and white image. FIG. 9A shows the case where the shower plate 5 of the above-described embodiment is used. FIG. 9B shows the results when a shower plate (see FIG. 10) in which the gas supply holes are arranged in a matrix is used. As can be seen from this result, in the conventional shower plate, the region where the flow velocity is extremely small is formed in a cross shape, and corresponds to the cross-shaped particle adhesion pattern on the wafer W as described in the background art section. Yes. Therefore, it can be understood that the cause of the cross-shaped particle adhesion pattern corresponds to the arrangement pattern of the gas supply holes of the shower plate through the result of the flow velocity distribution.

  On the other hand, in the shower plate 5 of the above-described embodiment, the circumferential flow velocity is almost uniform, and an extremely slow flow velocity region is not seen, so the occurrence of the crossed particle adhesion pattern is eliminated. For this reason, the restriction on the process condition is relaxed, so that the degree of freedom in setting the process condition is widened. For example, the condition can be set such as increasing the gas flow rate in order to improve the throughput.

  The above-described gas shower head 4 is a post-mix type in which the first gas and the second gas are separately supplied into the processing container 2, but the two gases are mixed in advance and then supplied to the processing atmosphere. It can be applied to the premix type.

  Further, the present invention is not limited to Ti film formation, and when performing gas treatment such as film formation under high temperature performed in a semiconductor manufacturing process, for example, metals such as W, Cu, Ta, Ru, Hf, Alternatively, it can be applied to the formation of a thin film such as a metal compound such as TiN, TiSi, or WSi, or an insulating film such as SiN or SiO2. Furthermore, the substrate processing apparatus to which the gas showerhead of the present invention is applied is not limited to a plasma CVD apparatus, and can be applied to a thermal CVD apparatus, an etching apparatus, an ashing apparatus, a sputtering apparatus, an annealing apparatus, and the like.

It is a longitudinal cross-sectional view which shows the film-forming apparatus incorporating the gas supply apparatus which concerns on embodiment of this invention. It is a longitudinal cross-sectional view which shows the gas supply apparatus which concerns on said embodiment in detail. It is a top view which shows the arrangement pattern of the gas supply hole of the shower plate in the gas supply apparatus which concerns on said embodiment. It is a top view which expands and shows a part of arrangement pattern of the gas supply hole of a shower plate. It is explanatory drawing for demonstrating the formation method of the arrangement pattern of the gas supply hole of a shower plate. It is explanatory drawing which shows the method for obtaining the distribution of the number of the gas supply holes of 1 degree | times about the circumferential direction of a shower plate. It is explanatory drawing which shows distribution of the number of the gas supply holes of 1 degree | times for the circumferential direction of a shower plate. It is explanatory drawing which shows the simulation result of the distribution of the flow rate of 1 degree | times for the circumferential direction of a shower plate. It is explanatory drawing which shows the simulation result of distribution of the flow velocity of the circumferential direction about a shower plate. It is a top view which shows the arrangement pattern of the gas supply hole of the conventional shower plate. It is a top view which shows the arrangement pattern of the gas supply hole of the conventional shower plate. It is a top view which shows the particle distribution on the semiconductor wafer in the case of using the conventional shower plate. It is explanatory drawing for demonstrating the estimation factor of the particle generation in the conventional shower plate.

Explanation of symbols

2 Processing container 21 stage (substrate mounting table)
31 Opening 4 Gas Shower Head (Gas Supply Device)
5 Shower plate 51 Concentric circles 61, 62 Gas supply pipes 7, 7a, 7b Gas supply holes W Semiconductor wafer S Algebraic spiral curve

Claims (2)

Gas supply provided with a shower plate which is arranged to face the mounting table in order to supply processing gas into a processing container provided with a mounting table on which a substrate is mounted, and which has a large number of gas supply holes. In the device
The gas supply holes are arranged circumferentially at equal intervals on a number of concentric circles, and the number of concentric gas supply holes on the outer and outer concentric circles is equal to the number of concentric gas supply holes on the outer side. Arranged to increase ,
The arrangement pattern of the gas supply holes is:
B) For any concentric circle except the outermost and innermost circumferences, the gas supply holes on the concentric circles and the gas supply holes immediately adjacent to the concentric circles adjacent to the inside and the concentric circles adjacent to the outside are on the radius of the concentric circles. Configured not to line up,
B) Arrange one gas supply hole among the gas supply holes arranged on each concentric circle so as to be arranged on the radius of the concentric circle, and form an algebraic spiral curve in which the gas supply holes arranged on the radius extend from the center of the concentric circle. A gas supply device characterized in that the arrangement pattern is the same as the arrangement pattern formed by rearranging the arrangement pitches in the circumferential direction so that the arrangement pitches are arranged at equal intervals so as to be arranged along . An airtight processing container, a mounting table provided in the processing container for mounting a substrate, an exhaust means for exhausting gas in the processing container, and the gas supply device according to claim 1. A substrate processing apparatus for processing a substrate on a mounting table with a processing gas supplied from a gas supply apparatus.

Images