Plasma reactor, method for plasma processing workpiece

Abstract

The plasma reactor includes a chamber body, a gas distribution port, a workpiece support, an antenna array, and an AC power source, wherein the chamber body has an inner space providing a plasma chamber, the gas distribution port is used to deliver a processing gas to the plasma chamber, the workpiece support is used to hold the workpiece, the antenna array includes a plurality of monopole antennas partially extending into the plasma chamber, and the AC power source is used to supply a first AC power to the plurality of monopole antennas.

Description

[0001] This application is a divisional application of the invention patent application with application number 201880034861.8 filed on May 25, 2018 and invention name “Plasma reactor, method for plasma processing workpiece”. Technical Field

[0002] The present disclosure relates to wafer processing systems and related methods. Background Art

[0003] For example, treatment of a workpiece, such as a semiconductor wafer, can be performed using a form of electromagnetic energy, such as RF power or microwave power. For example, power can be used to generate a plasma for performing a plasma-based process, such as plasma enhanced chemical vapor deposition (PECVD) or plasma enhanced reactive ion etching (PERIE). Some processes require extremely high plasma ion densities and extremely low plasma ion energies. This is true for processes such as deposition of diamond-like carbon (DLC) films, where the time required to deposit some types of DLC films can be several hours, depending on the desired thickness and plasma ion density. Higher plasma densities require higher source powers and generally translate into shorter deposition times.

[0004] Microwave sources typically produce very high plasma ion density while producing plasma ion energy less than that of other sources (such as inductively coupled RF plasma sources or capacitively coupled RF plasma sources). Therefore, microwave sources are ideal. However, microwave sources cannot meet the stringent uniformity required for deposition rate or etch rate distributed across the entire workpiece. Minimum uniformity may correspond to less than 1% process rate variation across a 300 mm diameter workpiece. Summary of the invention

[0005] In one aspect, a plasma reactor includes a chamber body having an interior space providing a plasma chamber, a gas distribution port for delivering a process gas to the plasma chamber, a workpiece support for holding a workpiece, an antenna array including a plurality of monopole antennas partially extending into the plasma chamber, and an AC power source for supplying a first AC power to the plurality of monopole antennas.

[0006] Implementations may include one or more of the following features.

[0007] The workpiece support may be configured to hold the workpiece so that the front surface of the workpiece faces the antenna array. The plurality of monopole antennas may extend into the plasma chamber in parallel. The portion of each monopole antenna extending into the plasma chamber may be cylindrical. The portion of each monopole antenna extending into the plasma chamber may be conical.

[0008] A plurality of monopole antennas may extend through a plate portion of the chamber body. The plate portion may provide a ceiling of the plasma chamber. Each monopole antenna may include an outwardly extending flange located on a far side of the plate portion away from the plasma chamber. The plate portion may be conductive. Each of a plurality of insulating sheaths may surround a portion of the monopole antenna extending through the plate portion to insulate the monopole antenna from the plate portion. Each monopole antenna may have an outwardly extending flange located on a far side of the plate portion away from the plasma chamber, and each insulating sheath may have an outwardly extending flange to separate the flange of the monopole antenna from the plate portion.

[0009] The workpiece support may be configured to hold the workpiece such that the front surface of the workpiece is perpendicular to the long axis of the plurality of monopole antennas. The workpiece support may be configured to hold the workpiece such that the front surface of the workpiece faces the antenna array. The plurality of monopole antennas face the workpiece support without an intervening barrier.

[0010] There may be a plurality of microwave or RF transparent window sheaths, and each window sheath may surround a portion of the monopole antenna that protrudes into the plasma chamber. The plurality of window sheaths include a material selected from ceramic and quartz.

[0011] The monopole antennas may be evenly spaced across the panel portion. The monopole antennas may have a uniform size and shape. The monopole antennas may have a non-uniform size or shape. Multiple monopole antennas may be arranged in a hexagonal pattern.

[0012] The first gas distribution plate may have a first plurality of gas injection orifices, a first process gas plenum covering the first gas distribution plate, and a first process gas supply conduit coupled to the first process gas plenum. The plurality of monopole antennas may extend through the gas distribution plate. The plurality of gas injection orifices may be positioned in spaces between the monopole antennas.

[0013] The second gas distribution plate may have a second plurality of gas injection orifices coupled to a third plurality of gas injection orifices in the first gas distribution plate, a second process gas plenum covering the second gas distribution plate, and a second process gas supply conduit coupled to the second process gas plenum. A plurality of monopole antennas may extend through the first gas distribution plate and the second gas distribution plate.

[0014] The AC power source may be configured to apply microwave power to the plurality of monopole antennas. The AC power source may be configured to apply microwave power to the plurality of monopole antennas to generate plasma in the plasma chamber. The AC power source may include a plurality of auto-tuners, each auto-tuner coupled to a different monopole antenna.

[0015] The AC power source can be configured to generate AC power of multiple different phases on multiple power lines, multiple monopole antennas can be divided into multiple groups, and different groups of monopole antennas can be coupled to different power lines. The number of different power lines can be at least 4. The monopole antennas of each group can be defined by the spatially continuous area of ​​adjacent monopole antennas. The monopole antennas in the spatially adjacent area can be coupled to the power line that provides AC power with sequentially adjacent phases. Multiple monopole antennas can be divided into N groups, and the AC power source is configured to generate AC power on the N power lines with phases separated by 360 / N. N can be 4 or 6 or 8. The spatially continuous area can be a plurality of linear rows. The spatially continuous area can be a plurality of circular sectors.

[0016] In another aspect, a method of plasma processing a workpiece includes the steps of supporting the workpiece in a plasma chamber, delivering a process gas to the plasma chamber, and generating plasma in the chamber by applying AC power to an antenna array including a plurality of monopole antennas extending partially into the plasma chamber.

[0017] In another aspect, a plasma reactor includes a chamber body having an interior space providing a plasma chamber, a process gas distribution system for delivering process gas to the plasma chamber, a workpiece support for holding the workpiece, and an antenna array including a plurality of monopole antennas. The process gas distribution system includes a first gas distribution plate having a first plurality of gas injection orifices, a first process gas plenum covering the gas distribution plate, and a first process gas supply conduit coupled to the first process gas plenum. The plurality of monopole antennas extend through the first gas distribution plate and partially into the plasma chamber.

[0018] Implementations may include one or more of the following features.

[0019] A plurality of gas injection orifices may be positioned in portions of the first gas distribution plate separating the monopole antennas. The process gas distribution system may include a gas plenum plate having a recess on a surface facing the first gas distribution plate, the recess providing a plenum. A plurality of monopole antennas may extend through the gas plenum plate. A plurality of monopole antennas may extend through unrecessed areas between the recesses of the gas plenum plate. Each monopole antenna may be surrounded by a respective portion of the recess.

[0020] The second gas distribution plate may have a plurality of passages coupled to a second plurality of gas injection orifices in the first gas distribution plate. A second process gas plenum may cover the second gas distribution plate, and a second process gas supply conduit may be coupled to the second process gas plenum. A plurality of monopole antennas may extend through the first gas distribution plate and the second gas distribution plate.

[0021] The plurality of monopole antennas may be arranged in a hexagonal pattern. The plurality of gas injection orifices may be arranged in a hexagonal pattern. The plurality of monopole antennas may extend in parallel into the plasma chamber. The AC power source may be configured to apply microwave or RF power to the plurality of monopole antennas to generate plasma in the plasma chamber.

[0022] In another aspect, a plasma reactor includes a chamber body, a grid filter, a gas distribution port, a workpiece support, an antenna array, and an AC power source, wherein the chamber body has an interior space providing a plasma chamber, the grid filter extends across the interior space and divides the plasma chamber into an upper chamber and a lower chamber, the gas distribution port is used to deliver a process gas to the upper chamber, the workpiece support is used to hold the workpiece in the lower chamber, the antenna array includes a plurality of monopole antennas partially extending into the upper chamber, and the AC power source is used to supply a first AC power to the plurality of monopole antennas.

[0023] Implementations may include one or more of the following features.

[0024] The plurality of monopole antennas may extend in parallel into the upper chamber. The plurality of monopole antennas may extend perpendicular to the grid filter. The workpiece support may be configured to hold the workpiece parallel to the grid filter. The grid filter may be positioned between the plurality of monopole antennas and the workpiece support. The AC power source is configured to apply microwave power to the plurality of monopole antennas to generate plasma in the upper chamber.

[0025] The second process gas distribution system may deliver the second process gas to the lower chamber. The grid filter may include a gas distribution plate having a first plurality of gas injection orifices and a gas plenum plate covering the gas distribution plate. A recess in the bottom surface of the gas plenum plate may provide a plenum for flowing the second process gas to the gas injection orifices. The grid filter may have a plurality of apertures through the gas plenum plate and the gas distribution plate for flowing plasma or electrons from the upper chamber to the lower chamber.

[0026] In another aspect, a plasma reactor includes a chamber body having an inner space providing a plasma chamber, a gas distribution port for delivering a process gas to the plasma chamber, a workpiece support for holding a workpiece, an antenna array including a plurality of monopole antennas partially extending into the plasma chamber, and an AC power source for supplying a first AC power to the plurality of monopole antennas. The plurality of monopole antennas are divided into a plurality of groups of monopole antennas, and the AC power source is configured to generate a plurality of AC powers of different phases on a plurality of power lines, and different groups of monopole antennas are coupled to different power lines.

[0027] Implementations may include one or more of the following features.

[0028] Each group of monopole antennas may be defined by a spatially contiguous region of adjacent monopole antennas. The monopole antennas in the spatially contiguous region are coupled to a power line that provides AC power in sequentially adjacent phases. The spatially contiguous region may be a plurality of linear rows. The spatially contiguous region may be a plurality of sectors arranged at an angle around a central axis.

[0029] Multiple monopole antennas can be divided into N groups, and the AC power source is configured to generate AC power on the N power lines with a phase separated by 360 / N. The group can form a plurality of linear rows, and the linear rows can have equal widths. The group can form a plurality of sectors arranged at an angle around a central axis, and the plurality of sectors can present equal angles around the central axis. The plurality of sectors can be circular sectors or triangular sectors.

[0030] The AC power source may be configured to apply a common phase shift to the phases on the N power lines. The AC power source may be configured to increase the phase shift linearly over time. The AC power source may be configured so that the phases on each power line have a phase shift frequency between 1 and 1000 Hz.

[0031] The AC power source is configured to apply microwave or RF power to a plurality of monopole antennas to generate plasma in a plasma chamber. The AC power source includes a plurality of auto-tuners, each auto-tuner coupled to a different monopole antenna. The reactor may include a supplemental monopole antenna. The supplemental monopole antenna may be positioned at the center of the array. The center monopole antenna may be driven using a one-phased signal.

[0032] In another aspect, a method of plasma processing a workpiece includes the steps of supporting the workpiece in a plasma chamber, delivering a process gas to the plasma chamber, and generating plasma in the chamber by generating a plurality of different phases of AC power on a plurality of power lines and applying the plurality of different phases of AC power from the power lines to different respective groups of monopole antennas extending partially into the plasma chamber.

[0033] The foregoing advantages may include, but are not limited to, those described below and elsewhere herein. A plasma reactor according to certain aspects may provide improved processing uniformity (e.g., improved uniformity of deposition or etching of a material layer on a substrate). A plasma reactor may be able to more efficiently use ions or radicles for processing, thereby providing improved processing speeds (e.g., deposition rates or etching rates), and thereby increasing throughput. A plasma reactor may have better temperature control, thereby providing more stable processing.

[0034] The details of one or more implementations of the subject matter described in this specification are set forth in the accompanying drawings and the description below. Other potential features, aspects, and advantages will become apparent from the description, drawings, and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 is a schematic cross-sectional side view of a plasma reactor according to a first embodiment.

[0036] Figure 2 for Figure 1 Schematic bottom view of the top plate of the plasma reactor.

[0037] Figure 3 is a schematic cross-sectional side view of a plasma chamber according to a second embodiment.

[0038] Figure 4 for Figure 1 An enlarged view of a portion of.

[0039] Figure 5 for Figure 4 Examples of different implementations of the parts in .

[0040] Figure 6is a schematic top view of an antenna array according to a first embodiment.

[0041] Figure 7 is a schematic top view of an antenna array according to a second embodiment.

[0042] Figure 8 is a schematic top view of an antenna array according to a third embodiment. DETAILED DESCRIPTION

[0043] Processing of workpieces, such as semiconductor wafers, can be performed in a plasma reactor. For example, electromagnetic energy, such as RF power or microwave (MW) power, can be used to generate a plasma in a chamber to perform a plasma-based process, such as plasma enhanced chemical vapor deposition (PECVD) or plasma enhanced reactive ion etching (PERIE). Some processes, such as deposition of diamond-like carbon (DLC) films, require high plasma ion density and low plasma ion energy. Higher plasma density requires higher source power and generally results in shorter deposition times.

[0044] An advantage of a microwave source is that it can produce very high plasma ion densities while producing plasma ion energies that are lower than those of other sources (e.g., inductively coupled RF plasma sources or capacitively coupled RF plasma sources). Another advantage of a microwave plasma source is that it can produce plasma over a wide range of chamber pressures, typically from above atmospheric pressure to 10 -6 This enables microwave plasma processing to be used in a very wide range of processing applications.

[0045] However, many microwave sources cannot meet the stringent uniformity requirements for semiconductor processing. Minimum uniformity may correspond to less than 1% variation in processing rate across a 300 mm diameter workpiece. In systems where microwaves propagate into the chamber through slots in a waveguide, the antenna may have a periodic power deposition pattern that reflects the wave pattern of the microwave emission and the slot layout, resulting in a non-uniform distribution of processing rate. This prevents the desired uniformity of processing rate across the workpiece from being obtained. One technique to reduce uniformity issues is to use a rotating antenna in the plasma chamber. Unfortunately, this technique may have various setbacks, such as microwave leakage through the timing belt slots where the antenna rotates, and difficulties in microwave auto-tuning due to antenna rotation. In addition, the gas distribution from the center to the edge of the substrate may not be uniform.

[0046] However, microwave power can be delivered to the chamber through an array of monopole antennas. The microwaves propagate into the chamber through the antennas. This can alleviate the problem of slots in the antennas producing a periodic power deposition pattern. In addition, significant improvements in uniformity can be obtained by, for example, applying power to the antenna groups at different phases, thereby emulating a rotating source.

[0047] Another limitation on the processing rate is the amount of microwave power that can be delivered to the processing chamber without damaging the gas plate or grid filter or causing the gas plate or grid filter to overheat. Conventional gas plates provide the vacuum boundary of the chamber and may therefore be subject to significant mechanical stresses, making the gas plate susceptible to overheating and damage. Such gas plates can only withstand relatively low microwave power levels. Therefore, some processes (e.g., DLC deposition processes) may require several hours to achieve the desired DLC film thickness. This problem can be solved by providing a window sheath around each monopole antenna protruding into the plasma chamber, thereby reducing the risk of mechanical stress and increasing the power that can be applied.

[0048] Reference Figure 1 The plasma reactor 10 includes a chamber body 101 having, for example, a cylindrical sidewall 102 to close the chamber 100. The sidewall 102 is formed of a material that is opaque to microwaves to confine the microwaves within the chamber. The sidewall may be a conductive material (eg, metal).

[0049] The chamber 100 may be divided into an upper chamber 100a and a lower chamber 100b by a grid filter 112. The lower chamber 100b is a drift space because there is no substantial electric field when no bias is applied. The sidewall 102 may include an upper sidewall 102a surrounding the upper chamber 100a and a lower sidewall 102b surrounding the lower chamber 100b.

[0050] The top plate 104 may be formed of a conductive material and cover the upper chamber 100 a. The top plate 104 may be provided by a showerhead 118.

[0051] Reactor 10 further includes an array 108 of monopole antennas 116 connected to an AC power source 110, which is configured to generate power at microwave or RF frequencies. Monopole antenna array 108 includes a plurality of monopole antennas 116 that partially extend into upper chamber 100a. Antenna 116 is formed of a conductive material (e.g., copper or aluminum), or is formed of another metal coated with a highly conductive layer. In some embodiments, antenna 116 protrudes parallel to upper chamber 100a. Antenna 116 can protrude through top plate 104 of chamber body 101. The bottom surface of each antenna 116 can face grid filter 112.

[0052] In some embodiments, the bottom surfaces of antennas 116 are coplanar (e.g., antennas 116 protrude into chamber 100 by the same amount). Alternatively, the bottom surfaces of some antennas 116 (e.g., antennas in the center of array 108) may be recessed relative to other antennas. In this case, antennas 116 at the edge of array 108 protrude further into chamber 100 than antennas 116 at the center of array 108.

[0053] The antenna array 108 may be divided into antenna groups (eg, groups having an equal number of antennas). This allows different powers at different phases to be provided to different groups of antennas 116 within the antenna array 108.

[0054] In one example, the perimeter of the antenna array 108 forms a hexagonal configuration (see Figure 6 ). This allows the array to be divided into six triangular groups, each with an equal number of antennas (see Figure 7 The perimeter can also be configured in other shapes (e.g., square, pentagon, heptagon, or octagon). These shapes can also be divided into groups (e.g., four, five, seven, or eight groups) each covering a triangular shaped segment.

[0055] The antennas may be arranged at substantially uniform intervals within array 108. Within array 108, the antennas may be arranged in a hexagonal or rectangular pattern (see Figure 2 ). The pitch of the antennas in the array can be about 1 / 2 to 2 inches. The cross-section of the antenna 116 can have a uniform size and shape (e.g., the antenna can have a circular cross-section). Alternatively, some antennas can have different cross-sectional dimensions (e.g., the antenna in the center can have a larger diameter). The portion 116c of the antenna 116 that protrudes into the cavity can have a length L that is greater than the width W (see Figure 4 ).

[0056] In some embodiments, the antenna protrudes through the showerhead 118 (eg, a dual channels showerhead (DCSH)). The showerhead 118 may include a gas distribution plate 120 and a gas plenum plate 122. The long axis of the antenna 116 may be perpendicular to the lower surface of the showerhead 118.

[0057] The workpiece support base 106 for supporting the workpiece 124 in the lower chamber 100b has a workpiece support surface 106a. The workpiece support base 106 can be moved in an axial direction, for example, by a linear actuator, to adjust the height of the workpiece support base in the chamber 100. The workpiece support surface 106a can face the grid filter 112. The long axis of the antenna 116 can be perpendicular to the support surface 106a of the support base 106.

[0058] In some embodiments, the pedestal 106 includes one or more heating elements 107 configured to apply heat to the workpiece 124. When the workpiece is supported on the pedestal 106 and the precursor gas (if used) has been introduced into the chamber 100b, the heat from the heating element 107 is sufficient to anneal the workpiece 124. The heating element 107 can be a resistive heating element. In the case where the heating element 107 is positioned (e.g., embedded) in the pedestal 106, the workpiece 124 is heated by contact with the pedestal. Examples of the heating element 107 include separate heating coils. Wires connect a power source (such as a voltage source) (not shown) to the heating element, and one or more heating elements 107 can be connected to a controller.

[0059] The pedestal 106 can be configured to hold the workpiece 124 so that the front surface 124a of the workpiece faces the grid filter 112; the front surface 124a can be parallel to the grid filter 112. In another example, as discussed in further detail below, the pedestal 106 can be configured so that the front surface 124a of the workpiece faces the antenna array.

[0060] In some embodiments, the pedestal 106 can be mechanically rotated about an axis of rotation that coincides with the symmetry axis 106b of the pedestal. Such rotation can improve plasma uniformity of processing on the workpiece 124. The pedestal 106 can be rotated by a rotation motor (not shown) attached to the pedestal.

[0061] An AC power source 110 is connected to the monopole antenna 116. For example, the power source 110 can be coupled to the antenna array 108 via one or more coaxial cables. The power source 110 can operate in a frequency range of 30 Hz to 30 GHz. For example, the power source 110 can generate power at a microwave frequency (e.g., 300 MHz to 30 GHz), an RF frequency (e.g., 300 kHz to 30 MHz), and / or a VHF frequency (e.g., 30 MHz to 300 MHz). The power source 110 is configured or controlled to apply microwave or RF power to the plurality of monopole antennas to generate plasma in the chamber 100. In some embodiments, the power source 110 can also apply a DC voltage.

[0062] As will be described further below, AC power source 110 may be configured to generate AC power of different phases on multiple power lines and supply power to different groups of monopole antennas 116 through these lines.

[0063] In some embodiments, a conductive shield 134 including a cylindrical sidewall 136 surrounds the upper sidewall 102a and extends above the top plate 104 (eg, above the showerhead 118). The conductive shield 134 can be electrically grounded.

[0064] In some embodiments, an upper gas injector assembly provides process gas into the upper chamber 100a. In some embodiments, the upper gas injector assembly can include a plurality of upper gas injectors 138 to provide gas, for example, from a ceiling 104 of the chamber 100. The gas injectors 138 allow for uniform gas injection into the plasma chamber 100a.

[0065] For example, gas is supplied from a gas source 126 through a gas conduit 130 to one or more gas distribution ports 128. The gas distribution ports 128 may be coupled to a gas plenum. For example, a recess 122a in the underside of a gas plenum plate 122 may provide a plenum for the flow of gas from the conduit 130. The gas plenum plate 122 overlies a gas distribution plate 120. The gas distribution plate 120 has a plurality of gas injection orifices 120a extending through the gas distribution plate 120 and fluidly coupled to the gas plenum to distribute gas into the upper chamber 100a. The orifices 120a and a portion of the optional recess 122a may provide an upper gas injector 138.

[0066] The gas injection orifices are positioned in the space between the monopole antennas 116. For example, referring to Figure 2 If the monopole antennas 116 are arranged in a hexagonal array, the gas injection orifices 120a may be similarly arranged in a hexagonal array (e.g., each monopole antenna 116 is surrounded by six orifices 120a). Similarly, the recessed portion 122a in the bottom surface of the gas filling portion plate 122 may be honeycomb-shaped, with the antennas 116 extending through the non-recessed portion (i.e., the center of each cell of the honeycomb).

[0067] although Figure 1A plenum formed by a recess in the bottom of the plenum plate is shown, but a volume 146 above the array 108 of monopole antennas 116 may provide a plenum for gas supply. In this case, for some embodiments, the plenum plate 122 is omitted, and the passage extends completely through the showerhead 118 (actually the gas distribution plate 120) to connect directly to the volume 146. The volume is closed by a cover 134, and the gas will be supplied through the port extending through the cover 134. Alternatively, the plenum plate 122 may serve as a second gas distribution plate, which serves as a recess in the plenum and as a plurality of passages coupled to another plurality of gas injection orifices in the first gas distribution plate 120. In this case, the volume 146 may provide a second process gas plenum covering the second gas distribution plate 122, and a second process gas supply conduit coupled to the second process gas plenum may be provided. This allows two different process gases to be supplied to the chamber. The monopole antenna 116 extends through both the first gas distribution plate 120 and the second gas distribution plate 122.

[0068] Back to Figure 1 Although a showerhead 118 in the ceiling of the chamber is shown, the gas may alternatively or additionally be supplied through the sidewalls (eg, through apertures in the upper sidewall 102a).

[0069] In some embodiments, the lower gas injector assembly provides the process gas into the lower chamber 100b. The lower gas injector assembly may include a plurality of lower gas injectors 158 to provide gas, for example, from the ceiling 104 of the chamber 100. The gas injectors 158 allow for uniform gas injection into the lower chamber 100b. The lower gas injectors may be part of, in place of, or below the grid filter 112.

[0070] For example, the lower gas injector assembly can be similar to the upper gas injector assembly. More specifically, the grid filter 112 can include a gas distribution plate 150 and a gas plenum plate 152. A recess 152a in the underside of the gas plenum plate 152 can provide a plenum for the flow of gas from the conduit 130 through the second distribution port 148. The gas distribution plate 150 has a plurality of gas injection orifices 150a extending through the gas distribution plate 150 and fluidly coupled to the gas plenum to distribute gas into the lower chamber 100b.

[0071] Again, although gas injection apertures 150a in the grid filter 112 are shown, the gas may alternatively or additionally be supplied through the sidewalls, such as through apertures in the lower sidewall 102b.

[0072] In such an embodiment, the gas types and gas flow rates entering the upper chamber 100a and the lower chamber 100b are independently controlled. In one example, an inert gas is supplied to the upper chamber 100a, and a process gas is supplied to the lower chamber 100b. The inert gas flow rate can be controlled to substantially prevent the gas from being introduced or diffused from the lower chamber 100b into the upper chamber 100a to provide substantial chemical isolation of the upper chamber 100a. The gas delivery system may include an exhaust system 140 (e.g., including a vacuum pump) to exhaust the precursor gas from the upper chamber 100a, thereby depressurizing the chamber 100.

[0073] In some embodiments, the AC power source 110 includes a plurality of auto-tuners, each auto-tuner coupled to a different monopole antenna 116. The level of RF power from the RF generator 110 is highly controllable. This can allow the plasma density in the upper chamber 100a to be substantially controlled (enhanced) by the RF power from the RF power generator. Thus, the formation of lattice defects or voids in the deposited material can be reduced.

[0074] In some embodiments, the grid filter 112 is in the shape of a flat disk. The grid filter may extend through the chamber 100. The grid filter 112 is formed as an array having a plurality of openings 112-1. The openings 112-1 may be evenly spaced across the grid filter 112. The axial thickness T of the grid filter 112 and the diameter d of the plurality of openings 112-1 may be selected to facilitate the flow of high energy directional beam electrons through the grid filter 112 while blocking the flow of non-beam (low energy) electrons and plasma ions through the grid filter 112.

[0075] The plasma in the lower chamber 100b may have different characteristics from the plasma in the upper chamber 100a. The grid filter 112 may act as a filter to substantially electrically isolate the upper chamber 100a and the lower chamber 100b from each other. In some embodiments, the grid filter 112 is formed of a conductive or semi-conductive material. For example, the grid filter 112 may be a metal (such as aluminum). The grid filter 112 may be connected to ground, or may be electrically floating. Depending on whether the substrate is grounded or RF hot, the grid filter 112 may be RF hot or grounded. In some embodiments, the grid filter 112 is formed of a non-conductive material. In some embodiments, the grid filter 112 is coated with a process compatible material (such as silicon, carbon, a silicon carbon compound, or a silicon oxide compound) or an oxide material (e.g., aluminum oxide, yttrium oxide, or zirconium oxide).

[0076] Now refer to Figure 3, the single chamber plasma reactor 10 includes a plasma chamber 100 including a workpiece support 106. In general, except as described below, Figure 3 The reactor and Figure 1 For example, the plasma reactor can use the same monopole antenna array.

[0077] and Figure 1 The embodiments shown are different. Figure 3 The plasma reactor shown in FIG. 1 is not divided into an upper chamber and a lower chamber; there is no grid filter extending across the chamber. Therefore, the reactor has only a single chamber 100. So the monopole antenna array 108 will generate plasma in the same chamber as the workpiece support. The chamber 100 is surrounded by a side wall 102, which is formed of a microwave opaque material (such as metal). In some embodiments, the side wall 102 includes a transparent window, or is a transparent material (such as a dielectric material).

[0078] In this example, the gas injector assembly includes a plurality of gas injectors 138 to distribute gas directly into the plasma chamber 100 where the workpiece 124 is located. Gas is supplied from a gas source 126 through a gas conduit 130. One or more gas distribution ports 128 are coupled to a gas plenum provided by a recess 122a in the underside of a gas plenum plate 122. The gas plenum plate 122 overlies a gas distribution plate 120. The gas distribution plate 120 has a plurality of gas injection orifices 120a extending through the gas distribution plate 120 and fluidly coupled to the gas plenum. The orifices 120a (optionally together with a portion of the recess 122a) can provide the gas injectors 138 to distribute gas into the chamber 100. The gas injection orifices are positioned in the space between the monopole antennas 116.

[0079] AC power source 110 provides the MW frequencies required by monopole antenna array 108. Monopole antenna 116 extends in parallel into plasma chamber 100. Potential advantages of this configuration are the ability to provide high density plasma to processes requiring high energy, such as DLC deposition, and the ability to increase plasma efficiency and wafer temperature.

[0080] Now refer to Figure 4, the dual channel showerhead 118 includes a gas filling portion 122 and a gas distribution plate 120. In one example, the showerhead is made of, for example, aluminum. In some embodiments, the showerhead includes a disc-shaped plate with perforations on the bottom surface to provide an orifice 120a for evenly distributing the reaction gas over a second parallel flat surface (such as a grid filter or a workpiece). In some embodiments, the orifice provides a nozzle with a narrow passage 120b to pass from the filling portion to a trumpet-shaped nozzle 120c at the bottom surface of the showerhead 118.

[0081] In addition, the showerhead 118 includes apertures 118a extending from the top surface to the bottom surface, each aperture being sized to hold a separate monopole antenna 116. The spacing between the apertures 118a can be selected to effectively maximize the number of antennas 116 in the showerhead 118 in consideration of power and current. For example, the spacing between the antennas 116 can be such that adjacent antennas 116 are close but not touching (e.g., less than 10 mm apart). The antennas 116 should not be so close that a short circuit may occur. For example, adjacent antennas 116 can be spaced more than 2 mm apart.

[0082] like Figure 4 As shown, each monopole antenna 116 may have a cylindrical shaft 116a protruding into the chamber 100a. However, monopole antennas of different shapes and lengths may be suitable for different purposes and applications during deposition or etching processes. For example, Figure 5 As shown, the portion 216a of the monopole antenna that protrudes into the cavity 100a may have a conical shape. Figure 4 , the antenna 116 may have an outwardly protruding flange or shoulder 116b. The flange or shoulder 116 may be a circular protrusion extending laterally from the shaft 116a. The flange or shoulder 116 is positioned above the showerhead 118. The aperture 118a allows the shoulder 116b of the monopole antenna 116 to be located on the top surface of the showerhead 118 while allowing the shaft 116a to protrude out of the showerhead 118 and into the plasma chamber 100. This can fix the vertical position of the bottom of the antenna 116 within the chamber 100.

[0083] Due to the high voltage applied during processing, the monopole antenna 116 can reach elevated temperatures (e.g., 30° C. to 400° C.). Temperature control can be provided by channels (not shown) in the antenna's support (e.g., channels in the gas distribution plate 120). The channels carry a coolant to absorb excess heat from the antenna 116 and surrounding components. A heat exchanger located outside the chamber can be used to remove heat from the coolant.

[0084] Each monopole antenna 116 is partially surrounded by an insulator dielectric sheath 152. More specifically, the sheath 152 can closely cover at least the portion 116c of the antenna 116 extending into the chamber 110. The sheath can also cover the entire shaft 116a (e.g., the entire portion extending through the gas distributor 120 and the plenum 122 and the portion extending into the chamber 100a). The sheath 152 is transparent to the radiation generated by the monopole antenna (e.g., the sheath 152 can be a microwave or RF transparent window sheath).

[0085] The jacket 152 may include a cylindrical section 152a surrounding the axis 116a of the monopole antenna 116 and a base plate 152b covering the bottom of the monopole antenna 116. The jacket 152 may also include an outwardly protruding flange or shoulder 152c extending from the top of the cylindrical section 152. The flange or shoulder 152c separates the flange 116b of the monopole antenna 116 from the top surface of the showerhead 118. The conical monopole antenna 216 is surrounded by the conical jacket 252 (see FIG. Figure 5 ).

[0086] The window shield 152 may be formed of an electrically insulating material such as ceramic, alumina, or quartz. The shield 152 can electrically isolate the antenna 116 from the gas distribution plate 120 and the gas filling plate 122, and can protect the conductors from the environment in the chamber 100a. The shield can also prevent contamination of the process (e.g., metal sputtering off the antenna 116).

[0087] Reference Figure 6 and Figure 7 As described above, AC power source 110 may be configured to supply power at multiple different relative phases to different groups of monopole antennas 116. To provide the different groups, monopole antennas 116 may be phase controlled individually or in groups. Power source 110 may include a single signal source 306, the output of which is then split and then phase shifted (e.g., using analog circuitry). Alternatively, power source 110 may include multiple power sources (e.g., multiple digital signal generators 306) to generate multiple signals at different phases.

[0088] Typically, where the array 108 is divided into N groups, the AC power source can generate power with N different phases (e.g., the N phases are 360 / N degrees apart). The AC power source can be configured to generate AC power with phases 360 / N apart on the N supply lines. The antennas 116 can be divided into different numbers of groups 308 / 408 (e.g., 4, 5, or more groups). The antennas of each group can occupy a spatially contiguous area of ​​the antenna array.

[0089] Figure 6An example of an array having groups arranged in linear rows is shown. More specifically, Figure 6 An example of a linear phase array is shown. The array may be divided into N groups 308. The groups may be provided by different rows 308 of antennas 116 (e.g., each region may cover a substantially linear strip across the array). N conductor lines 304 may be used to connect the power supply 110 to the N groups of antennas 116 to provide a different phase to each group of antennas. Figure 6 The monopole antenna array 108 is shown arranged in a hexagonal configuration, but this is not required.

[0090] Figure 7 An example of an array with groups angularly spaced about a central axis is shown. For example, each region may cover a circular sector; if the N regions are equal in size, the arc would be 360 / N degrees. In the example shown, the antenna 116 is divided into six different groups 408. Each group 408 is coupled to a different conductor line 404, thereby providing a different phase to each group of the antenna. The groups may be triangular regions of equal area on the array.

[0091] Areas that are spatially adjacent to each other can be provided with power from sequentially adjacent phases of a plurality of different phases. Figure 7 In the embodiment, there are six regions 410, and the signals applied to two adjacent regions (e.g., regions 410-1 and 410-2) are 60° apart. For example, power with relative phases of 0°, 60°, 120°, 180°, 240°, and 300° can be applied to regions 410-1, 410-2, 410-3, 410-4, 410-5, and 410-6.

[0092] As another example, in Figure 6 In the example, there are N regions 310, and the signals applied to two adjacent regions 310-1 and 310-2 are separated by N / 360°. For example, power with relative phases of 0°, (1 / N)*360°, ..., and (N-1 / N)*360° may be applied to regions 310-1, 310-2, ..., and 310-N. Although the phases are separated by equal intervals in these examples, this is not required.

[0093] A polar phased array or a linear phased array for controlling the monopole antenna 116 may be used in different configurations. Figure 7 As shown, the polar phase array can use a six-phase power control configuration through the digital signal generator 406 to send different signals to the group of antennas 116 in increments of 60. Similar to having a rotating antenna, this increases the uniformity of the plasma. In another example, as Figure 6As shown, a linear phase array may be used in an n-phase power control configuration using a digital signal generator 306. This allows a high degree of controllability of the antenna frequency and therefore a more uniform plasma.

[0094] Phase shifting the power applied to different antenna groups can increase the uniformity of plasma deposition. In effect, this approach mimics a mechanically rotating rotating antenna during the plasma deposition process, albeit at extremely high rotation rates. The phase shift frequency (i.e., the frequency at which a given region returns to the same phase offset) can be set between 1 and 1000 Hz.

[0095] Figure 8 The implementation is similar to Figure 7 106a, but includes an additional center antenna 420 located at the center of the array 108 of monopole antennas 116. The center antenna 420 can be larger (e.g., a larger diameter in a plane parallel to the array 108 and the support surface 106a) than the other antennas 116. The center antenna 420 can be driven using a single phase signal (e.g., generated by a digital signal generator). The center antenna 116 has the advantage of providing power adjustment for center-to-edge uniformity tuning in the process.

[0096] As an alternative or in addition to the above phase shift, power can be applied to the antenna in a pulsed manner. For example, power can be applied in a pulsed manner at a rate of 1 to 1000 Hz. The pulses can have a duty cycle of 5% to 95% (e.g., 25% to 75%). Within a given on-time of the duty cycle, power at RF or microwave frequencies (e.g., 300 kHz to 30 GHz) can be applied.

[0097] In some embodiments, a plasma reactor can be used for deposition of films in a PECVD process. In such a process, the deposited layer may have some empty atomic lattice positions. As additional layers are deposited, the additional layers cover the empty lattice positions, thus forming voids in the crystalline structure of the deposited material. Such voids are lattice defects and compromise the quality of the deposited material. A microwave source (such as, Figure 1 The microwave source may have a frequency of 2.45 GHz and produce a plasma with negligible ion energy levels.

[0098] Generally, the frequency of microwaves is not so accurate and has a fluctuation of about ±2%. Because the frequency of microwaves has fluctuations, the reflectivity of the microwave path may change significantly, resulting in a change in the electric power of the microwaves supplied to the antenna and a change in the plasma density. Therefore, in order to control the plasma density according to the electric power of the reflected wave, it is necessary to accurately monitor the frequency of microwaves to compensate for the change in the electric power of the reflected wave caused by the frequency fluctuation.

[0099] Although this document includes many specific implementation details, these should not be construed as limitations on any invention or on the scope of what may be claimed, but rather as descriptions of specific features of specific implementations of particular inventions. Certain features described in this document in the context of separate implementations may also be implemented in combination in a single implementation. Conversely, various features described in the context of a single implementation may also be implemented in multiple implementations individually or in any suitable subcombination. Furthermore, although the above features may be described as functioning in certain combinations and even initially claimed as such, in some cases one or more features from the claimed combination may be removed from the combination, and the claimed combination may involve subcombinations or variations of subcombinations.

[0100] A number of implementations have been described, however, it will be appreciated that various modifications may be made.

[0101] Accordingly, other implementations are within the scope of the following claims.

Claims

1. A plasma reactor, comprising: a chamber body having an interior space providing a plasma chamber, the chamber body including a plate portion providing a ceiling of the plasma chamber; a gas distribution port for delivering a process gas to the plasma chamber; a workpiece support, the workpiece support being used to hold a workpiece; an antenna array including a plurality of monopole antennas extending in parallel through the plate portion and from the top plate portion into the plasma chamber; and An AC power source is provided for supplying a first AC power to the plurality of monopole antennas to generate plasma in the plasma chamber. 2 . The plasma reactor of claim 1 , wherein a portion of each monopole antenna extending into the plasma chamber is cylindrical or conical.

3. The plasma reactor of claim 1 , wherein the plate portion is electrically conductive and comprises a plurality of insulating sheaths, each sheath surrounding a portion of the monopole antenna extending through the plate portion to insulate the monopole antenna from the plate portion.

4. The plasma reactor of claim 3 , wherein each monopole antenna includes an outwardly extending flange located on a far side of the plate portion away from the plasma chamber, and each insulating sheath includes an outwardly extending flange to separate the flange of the monopole antenna from the plate portion.

5. The plasma reactor of claim 1, comprising a plurality of microwave or RF transparent dielectric sheaths, each dielectric sheath surrounding at least a portion of a monopole antenna protruding into the plasma chamber.

6. The plasma reactor of claim 5, wherein each dielectric sheath covers the entirety of the monopole antenna protruding into the plasma chamber.

7. The plasma reactor of claim 1, wherein the plurality of monopole antennas extend through the plate portion to equal distances into the chamber.

8. The plasma reactor of claim 1, wherein the monopole antennas are evenly spaced across the plate portion.

9. The plasma reactor of claim 1, wherein the plurality of monopole antennas face the workpiece support without intermediate obstructions.

10. A method for plasma processing a workpiece, comprising the following steps: supporting a workpiece in the plasma chamber via a workpiece support; delivering a process gas to the plasma chamber; and Plasma is generated in the chamber by applying AC power to an antenna array including a plurality of monopole antennas extending in parallel through a plate portion forming a ceiling of the plasma chamber and partially into the plasma chamber.

11. The method of claim 10, wherein the board portion is electrically conductive and includes a plurality of insulating sheaths, each sheath surrounding a portion of a monopole antenna extending through the board portion to insulate the monopole antenna from the board portion.

12. The method of claim 10, wherein the plurality of monopole antennas extend an equal distance into the chamber through the plate portion.

13. The method of claim 10, wherein the monopole antennas are evenly spaced across the panel portion.

14. The method of claim 10, wherein the plurality of monopole antennas face the workpiece support without intermediate obstructions.

Images