A microwave plasma reactor equipped with an emitter and an absorber, and a method for plasma treatment of a workpiece using the microwave plasma reactor.

Abstract

The microwave plasma reactor 1 of the present invention comprises a plasma chamber 2, a work holder 6, a gas flow system, one or more microwave generators, and a microwave emitter 10, each of which comprises an amplifier, a phase shifter, and a radiating element. Each microwave emitter 10 is connected to at least one of the one or more microwave generators, and the radiating elements of the multiple microwave emitters 10 are mounted in the plasma chamber 2. The microwave plasma reactor 1 further comprises one or more microwave absorbing units 11, each of which comprises an absorbing element, and the absorbing elements of one or more microwave absorbing units 11 are mounted in the plasma chamber 2. Furthermore, the microwave plasma reactor 1 comprises an emitter control unit adapted to individually control the amplification of the amplifiers and the phase shift of the phase shifter for each or most of the microwave emitters 10, and to generate microwave output from the emitter array to one or more desired locations in the plasma chamber 2 in a desired distribution. In a further aspect of the present invention, a method is provided for plasma processing a workpiece 7, such as a substrate / wafer, using such a microwave plasma reactor 1.

Description

[Technical Field]

[0001] The present invention relates to a microwave plasma reactor and a plasma processing method for workpieces such as substrates and wafers using this microwave plasma reactor. [Background technology]

[0002] Plasma-assisted (or activated) chemical vapor deposition (PECVD) and plasma-assisted reactive ion etching (PERIE) are widely used in various applications in the semiconductor industry. For example, they are used to process workpieces such as silicon or glass substrates and wafers. In general processing, plasma generated by frequency (Radio Frequency, RF: less than 300 MHz, usually less than 30 MHz, standard operating frequency 13.56 MHz) is the most widely used. However, plasma generation using microwave sources (Microwave, MW: 300 MHz or higher, usually more than 900 MHz, standard operating frequency 2.45 MHz), especially magnetrons, can generate higher density plasma. However, with conventional microwave sources for plasma generation, it is often difficult to ensure plasma uniformity, and spatial changes and adjustments to the plasma density are also difficult. The main reason for this is that the plasma shape is constrained by the shape of the plasma reactor and the waveguide used to transmit microwaves from the magnetron to the processing chamber. Because plasma control is difficult, it becomes challenging to address edge effects when processing large substrates, for example, those with a diameter of 300 mm or more.

[0003] High plasma density is required for the deposition of diamond-like carbon (DLC) films and the production of synthetic diamonds using CVD technology, particularly requiring high-power power supplies. In the field of CVD diamond synthesis, microwave plasma has been confirmed to be the most efficient CVD diamond deposition method in terms of balancing power efficiency, growth rate, growth area, and product purity. To form a uniform and stable large-area plasma across the entire surface of a large-area substrate and achieve uniform CVD diamond growth over a wide area, it is necessary to improve conventional configurations. This requires, for example, securing a wider CVD growth area, improving uniformity, increasing the growth rate, ensuring reproducibility, achieving high power efficiency, and reducing production costs.

[0004] Therefore, there is a need for an improved microwave plasma reactor that can solve these problems and meet the required specifications, particularly one suitable for microwave plasma CVD diamond synthesis. [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] The present invention aims to provide an improved microwave plasma reactor that can generate a stable and uniform plasma, achieve both cost-effectiveness and energy efficiency, and allow for spatial variation and adjustment of plasma density. In particular, for example, when processing large substrates with a diameter of 300 mm or more, the present invention aims to provide an improved microwave plasma reactor suitable for microwave plasma CVD diamond synthesis that has a structure that allows for plasma adjustment to address edge effects, and further, for example, secures a wider CVD growth area, improves uniformity, increases growth rate, ensures reproducibility, achieves high output efficiency, and reduces production costs. The object of the present invention is realized by the microwave plasma reactor described in claim 1.

[0006] A further object of the present invention is to provide an improved method for processing workpieces such as substrates and wafers with high cost efficiency and energy efficiency. In particular, for example, a large substrate or wafer with a diameter of 300 mm or more is processed with high uniformity. Furthermore, for example, a wider CVD growth region is secured, the uniformity is improved, the growth rate is increased, the reproducibility is ensured, a high output efficiency is realized, and a method suitable for microwave plasma CVD diamond synthesis that suppresses production costs is provided. The object of the present invention is achieved by the method described in claim 20.

[0007] Specific embodiments of the apparatus and method according to the present invention are described in the dependent claims.

Means for Solving the Problems

[0008] The microwave plasma reactor according to the present invention - is a plasma chamber having a base, an upper part, and a side wall part extending from the base to the upper part. In particular, it is a plasma chamber having a prism shape or a cylindrical shape, and the upper part forms a curved dome. - a workholder disposed at the base of the plasma chamber and having a support surface for supporting a workpiece such as a substrate. - a gas flow system for supplying a process gas to the plasma chamber and / or discharging gas from the plasma chamber. - one or more microwave generation units configured to generate microwaves of frequency f. - a plurality of microwave emitters each having an amplifier, particularly a solid-state amplifier, a phase shifter, and a radiation (or supply) element, particularly an antenna. Each microwave emitter is connected to at least one of the one or more microwave generation units. The radiation elements of the plurality of microwave emitters are installed in the plasma chamber, particularly the side wall part, and form an emitter array. - One or more microwave absorbing parts configured to absorb microwaves of a frequency f, each microwave absorbing part having an absorbing element, particularly an antenna terminated with a matching load such as a 50 Ω load, and the absorbing elements of the one or more microwave absorbing parts being installed in a plasma chamber, particularly in a side wall part, and the one or more microwave absorbing parts forming an absorber array, and - An emitter control (or beam steering) unit configured to individually control amplification by an amplifier and phase shift by a phase shifter for each or most of the microwave emitters, and generate a desired distribution of microwave output from the emitter array to one or more desired positions in the plasma chamber, and comprises.

[0009] By using such a microwave plasma reactor, it is possible to generate a variable electric field (E field) in the plasma chamber and form a plasma with a desired density in a specific region in the plasma chamber. Since the plasma can be controlled by changing this E field, for example, when forming a film layer of a material or performing etching, the plasma can be adjusted as necessary to achieve the desired uniformity.

[0010] The outer wall of the plasma chamber is formed of metal, for example, aluminum, and the inner wall is formed of metal or a microwave absorbing material.

[0011] The workholder (or pedestal) is made of metal, and for example, molybdenum is used (particularly for applications in synthetic diamond manufacturing). In order to reduce E field spikes at the workholder, the edges of the workholder may be filleted.

[0012] Instead of using a plurality of absorbing elements, for example, a single absorbing element may be employed as a continuous piece of absorbing material essentially intervening or scattered between the radiating elements or antennas. Such a single absorbing element is considered to form an absorber array as before by being arranged (complementarily) with respect to the plurality of radiating elements constituting the emitter array.

[0013] Plasma intensity and uniformity can be achieved, for example, by establishing a time-independent distribution of the E-field in the plasma region, or by changing the E-field distribution on the plasma region with a time period shorter than the plasma extinction time. This can be achieved, for example, by periodically "scanning" the E-field focus / spot across the plasma region. In the latter case, it is possible to change the scanning speed, residence time, or point density (or the distance between consecutive locations where the focus / spot temporarily resides in a particular region) at specific locations of the focus / spot.

[0014] In one embodiment of the reactor, one or more microwave absorbers are arranged and configured to absorb a portion of the microwave output emitted from the radiating element, particularly scattered and reflected microwave output. This ensures that the radiation from the radiating element is unaffected by the plasma chamber, and in particular, free-field radiation essentially arises from the radiating element. More specifically, this approximates a hypothetical situation with infinitely open radiation boundary conditions.

[0015] In a further embodiment of the reactor, the emitter array and absorber array are conformal arrays having a common central axis coinciding with the central axis of the plasma chamber, and the emitter array is, in particular, arranged alternately with or nested within the absorber array, at least partially.

[0016] The radiating / supplying elements are positioned parallel to the workpiece holder so that the tangential characteristics of the emitted E-field propagate across the support surface where the workpiece is placed for processing. By appropriately adjusting the phase (and amplitude) of each radiating element, the E-field on the workpiece can be focused and guided, allowing the focal point / spot position to be moved as needed.

[0017] In a further embodiment of the reactor, radiating / supplying elements forming an emitter array and absorbing elements forming an absorber array are arranged in one or more layers stacked on top of each other between the base and the top of the plasma chamber, on the sidewall. In particular, the radiating and absorbing elements are arranged alternately in several layers. In particular, all other layers consist solely of absorbing elements, forming a first number of upper layers and / or a second number of lower layers.

[0018] In a further embodiment of the reactor, the radiating and / or absorbing elements are arranged in a continuous rotational manner from one layer to the next successive layer, from lower to upper layers, and in particular, the radiating and absorbing elements are arranged in a helical or spiral pattern.

[0019] In a further embodiment of the reactor, the radiating element and the absorbing element have essentially the same shape.

[0020] In a further embodiment of the reactor, the lowest layer comprising the radiating element is positioned coplanar with the workpiece holder, particularly the support surface that supports the workpiece.

[0021] In a further embodiment of the reactor, the radiating and absorbing elements consist of a shortened waveguide, a horn antenna, or a double-ridged horn antenna, and in particular have a coaxial feed section, adapted for operation at frequency f.

[0022] In particular, the radiating / supplying elements / antennas and the absorbing elements / antennas do not extend into the internal space of the plasma chamber. Specifically, the radiating / supplying elements / antennas and the absorbing elements / antennas are flush with the inner surface of the side wall of the plasma chamber.

[0023] In further embodiments of the reactor, the frequency f is in the range of 500 MHz to 15 GHz, particularly in the range of 900 MHz to 5.8 GHz, and especially in the range of 2 GHz to 2.5 GHz. The frequency f belongs to the industrial, scientific, and medical (ISM) bands, for example, 915 MHz, 2.45 GHz, or 5.8 GHz.

[0024] In a further embodiment of the reactor, the emitter control unit is configured to move the focal point / spot of the microwave output (E-field) emitted by the emitter array along a desired two-dimensional or three-dimensional path on the workpiece holder, thereby generating a plasma of a desired shape (and density) within a desired limited space on the workpiece holder. The scanning pattern of the microwave output (E-field) may be, for example, a spiral shape (in a plane or in three dimensions). In particular, the scanning pattern may be a three-dimensional scanning pattern, for example, to process a non-planar workpiece / substrate.

[0025] In a further embodiment of the reactor, in order to maintain the plasma within a desired confined space, the emitter control unit is configured to essentially repeatedly move the focus of the microwave output along a two- or three-dimensional path that determines the desired confined space. Each repetition time is set to be shorter than the plasma extinction time in particular.

[0026] In a further embodiment of the reactor, the emitter control unit corrects non-uniformity in film deposition or etching (and achieves uniform film deposition or etching of the workpiece) by adjusting the length of time (i.e., dwell time) and / or output level at which microwaves emitted by the emitter array are focused on a specific point or area on the workpiece holder, or by adjusting the point density (or the distance between consecutive locations where a focus / spot temporarily dwells within a specific area). In this way, the scanning speed or dwell time, or point density, at a specific location of the focus / spot can be changed. For example, these may be increased or decreased as needed to obtain a desired level of film deposition or etching of the workpiece (particularly at different locations or areas of the workpiece).

[0027] In a further embodiment of the reactor, the matching load is provided with cooling means. This cooling means includes, for example, a heat sink using a cooling fluid such as air or liquid, such as water.

[0028] In a further embodiment of the reactor, the plasma chamber is vacuum-sealed.

[0029] In a further embodiment of the reactor, a dielectric window, such as a pressurized quartz window, is positioned in front of or inside the radiating and absorbing elements, or the coaxial feed section is equipped with a hermetic feedthrough coaxial connector, in order to properly seal the plasma chamber.

[0030] In a further embodiment of the reactor, to reduce the E-field around the coaxial pin of the coaxial feed section and to avoid undesirable spike plasma around the coaxial pin, a (thin) dielectric layer such as an alumina layer is placed in front of the waveguides of the radiating and absorbing elements, or a (thin) dielectric cylinder or tube, such as a cylinder or tube made of alumina or ceramic, is placed around the coaxial pin.

[0031] In a further embodiment of the reactor, a container made of a dielectric and microwave-transmitting material (which substantially does not absorb microwaves emitted at frequency f), such as alumina, fused silica, quartz, or a glass container, is placed inside the plasma chamber. A work holder is placed inside the container or the container is attached to the work holder. The container is vacuum-sealed to the plasma chamber, which may be filled with air. Plasma is formed inside the container. The top of the container may be a curved dome or ellipsoid shape.

[0032] In a further embodiment, the reactor further comprises temperature control means, such as cooling and / or heating means, configured to regulate the temperature of the work holder. The temperature control means is controlled, for example, by a temperature control unit.

[0033] In a further embodiment, the reactor further comprises cooling means configured to cool the plasma chamber. The plasma chamber may be cooled to remove heat from the microwave output that was not dissipated by the plasma or the absorption element.

[0034] In a further embodiment, the reactor includes means for electrically biasing the workpiece / substrate and / or the workpiece / substrate holder.

[0035] The number of radiating / supplying and absorbing elements and antennas may be changed depending on the required dimensions and shape of the plasma chamber.

[0036] The phase shifter may be implemented using analog and / or digital circuits.

[0037] The total radiated power is, for example, in the range of 100W to 10kW.

[0038] The total number of radiating / supplying elements / antennas is, for example, in the range of 10 to 40, particularly 24, and the total number of absorbing elements / antennas is, for example, in the range of 20 to 100, particularly 48.

[0039] The intensity of the E-field ranges from 0.1 kV / m to 22 kV / m.

[0040] If a dielectric chamber is not used, the workpiece holder extends to the side wall above the plasma chamber, and there is a gap between the workpiece holder and the side wall ranging from 0.5 mm to 10 mm (determined by the frequency f).

[0041] The overall diameter of the microwave plasma reactor ranges from 400 mm to 800 mm, with a particularly notable diameter of 520 mm.

[0042] According to a further aspect of the present invention, a method for processing a workpiece such as a substrate or wafer is proposed, and this method is: -Providing a microwave plasma reactor according to any one of the above embodiments, - Place the workpiece in the workpiece holder, - The process gas is supplied to and / or discharged from the plasma chamber. -One or more microwave generators supply microwave power to multiple microwave emitters, -By individually controlling amplification by amplifiers and phase shift by phase shifters for each or most of the microwave emitters, a desired distribution of microwave output is generated by the radiating elements forming the emitter array, and a plasma with a desired plasma density is ignited and / or maintained at one or more desired locations within the plasma chamber, particularly within a desired limited space within the plasma chamber. -A portion of the microwave output emitted by multiple microwave emitters is absorbed by multiple microwave absorbers. - This method involves forming a material layer, particularly a material layer such as diamond or diamond-like carbon (DLC), on the surface of a workpiece, or etching the surface of the workpiece.

[0043] The pressure of the process gas in the plasma chamber or dielectric container is in the range of 10 to 120 Torr, especially for diamond deposition. For plasma ignition, the pressure may be as low as 4 Torr. For plasma etching applications, the pressure may be lower than 10 Torr.

[0044] In one embodiment, the method is part of a chemical vapor deposition (e.g., plasma-assisted / activated / enhanced, PECVD) process, particularly part of a process for depositing a diamond layer or a diamond-like carbon (DLC) layer on a workpiece (using methane as the process gas), or part of an etching process (e.g., plasma-enhanced reactive ion etching, PERIE), particularly part of a soft etching process, where the energy of the ions in the plasma is less than 10 eV.

[0045] In a further embodiment of this method, the amplification and phase shift control of the microwave emitter are adjusted so that the plasma is confined to the upper hemisphere of the workpiece, and in particular to contact the workpiece in the case of processing using chemical vapor deposition (CVD).

[0046] In a further embodiment of this method, the amplification and phase shift control of the microwave emitter are adjusted so that the plasma does not come into contact with the workpiece, particularly in temperature-sensitive processes, especially when the plasma is used to generate radicals, by confining it to a spot or sphere above the workpiece.

[0047] In a further embodiment of this method, the amplification and phase shift control of the microwave emitter are adjusted so that the plasma is confined to a small space within the plasma chamber, such as a spot or a sphere, and so that the plasma moves within the plasma chamber along a desired two-dimensional or three-dimensional path. While the plasma moves along the path, the plasma's moving speed and / or plasma intensity are varied, particularly to achieve uniform deposition or etching of the workpiece.

[0048] By combining the embodiments described above, even more specific embodiments can be obtained.

[0049] Non-limiting embodiments of the present invention will be described with reference to the drawings. In the drawings, the same reference numerals indicate the same parts. [Brief explanation of the drawing]

[0050] [Figure 1] This is a schematic side cross-sectional view of an embodiment of the microwave plasma reactor of the present invention. [Figure 2] This is a schematic side cross-sectional view of an embodiment of the microwave plasma reactor of the present invention (in which a quartz container is placed inside a plasma chamber). [Figure 3] This is a perspective view of an embodiment of the present invention, taken from slightly above, particularly emphasizing the emitter and absorber arrays of the microwave plasma reactor. [Figure 4] This is a slightly downward perspective view of a microwave plasma reactor, a further embodiment of the present invention, particularly highlighting the emitter and absorber arrays. [Figure 5a)] This figure shows a top cross-sectional view of an embodiment of the microwave plasma reactor of the present invention, illustrating a first layer having both a radiating element and an absorbing element. [Figure 5b)] This figure shows a top cross-sectional view of an embodiment of the microwave plasma reactor of the present invention, illustrating a second continuous layer having both a radiating element and an absorbing element. [Figure 6] Figure 4 is a side view of the microwave plasma reactor of an embodiment, particularly showing the connectors and coaxial pins of the radiating and absorbing elements. [Figure 7] This is an illustrative block diagram of the microwave output generation of the emitter array of the present invention. [Figure 8] This figure shows an exemplary spiral-shaped path / scanning pattern of the focus / spot of the microwave output (E-field) emitted by the emitter array of the microwave plasma reactor of the present invention. [Modes for carrying out the invention]

[0051] The gist of this invention relates to a microwave plasma reactor. This reactor can generate a variable E-field over time within a limited space, and as a result, it can form a desired distribution of microwave power within the plasma chamber so that the plasma density can be spatially changed / adjusted as needed. Such a microwave plasma reactor will be described in detail below.

[0052] Figure 1 is a schematic side cross-sectional view of an embodiment of the microwave plasma reactor 1 of the present invention. The microwave plasma reactor 1 comprises a plasma chamber 2. The plasma chamber 2 has a base 3, an upper part 4, and a side wall 5 extending from the base 3 to the upper part 4. A workpiece holder 6 has a pedestal shape and is provided with a support surface for supporting a workpiece 7 such as a substrate or wafer, and is positioned on the base 3. The microwave plasma reactor 1 further comprises a gas flow system. The gas flow system supplies process gas into the plasma chamber 2 via a gas inlet 8 and / or removes / exhausts gas (e.g., process gas or air) from the plasma chamber 2 via a gas outlet 9. The microwave plasma reactor 1 comprises a plurality of microwave emitters 10 (shown in dark colors / hatching in Figures 1 and 2). Each microwave emitter 10 comprises an amplifier, particularly a solid-state amplifier, a phase shifter, and a radiating (or supplying) element / antenna. Each microwave emitter 10 is connected to a microwave generator configured to generate microwaves of frequency f. Alternatively, two or more (lower-power) microwave generators may be used (instead of a single higher-power microwave generator), so that each microwave emitter 10 is connected to at least one of these microwave generators. The radiating elements of the multiple microwave emitters 10 are mounted in the form of an emitter array on the sidewall 5 of the plasma chamber 2. An emitter control unit is used to individually control amplification by an amplifier and phase shift by a phase shifter (i.e., beam steering) for each microwave emitter 10. The emitter control unit is configured to generate a desired distribution of microwave output from the emitter array to one or more desired locations within the plasma chamber 2. The emitters 10 and absorbers 11 (particularly the radiating and absorbing elements) are (essentially) flush with the inner surface of the sidewall 5 of the plasma chamber 2. A feature of the present invention is that the microwave absorbing section 11, configured to absorb microwaves of frequency f, is attached to the side wall 5 of the plasma chamber 2 in the form of an absorber array. Each microwave absorbing section 11 has an absorbing element, in particular an antenna terminated with a matching load such as a 50Ω load.

[0053] The microwave absorption unit 11 is positioned and configured to absorb a portion of the microwave output emitted from the radiating element, particularly the scattered and reflected microwave output. The purpose of the microwave absorption unit 11 is to ensure that the radiation from the radiating element is not affected by the plasma chamber 2, and that the radiating element essentially emits "free-field" radiation. In this way, it approximates a hypothetical situation with essentially an infinite open radiation boundary condition.

[0054] The amplifier and phase shifter of the microwave emitter 10 may be located near one or more microwave generators, particularly before the coaxial line leading to the radiating (or supplying) element antenna. Similarly, the absorbing element of the microwave absorber 11 may be located away from the absorbing element (microwave cavity). This is also true when the microwave emitter 10 and microwave absorber 11 are shown (in a simplified manner) on the side wall 5 of the plasma chamber 2. (However, only the radiating and absorbing elements are directly mounted on the side wall 5.)

[0055] The plasma chamber 2 is prism-shaped or cylindrical, for example, a cube, with a central axis a, and the upper part 4 can be formed as a curved dome, for example (shown by dashed lines in Figures 1 and 2). The outer wall of the plasma chamber 2 is made of metal, for example, aluminum, and the inner wall is made of metal or an absorbing microwave material.

[0056] The emitter array and absorber array are conformal arrays having a common central axis that coincides with the central axis a of the plasma chamber 2. As is clear from Figures 3 and 4, the emitter array is nested within the absorber array.

[0057] The workholder 6 is made of metal, for example, molybdenum is used (especially for applications in synthetic diamond production). In order to reduce the E-field spikes in the workholder 6, the edges of the workholder 6 may be filleted. The workholder 6 has a base or bottom 6 B and a central upper part 6 T and comprises. The base or bottom 6 B extends almost to the side wall part 5 of the plasma chamber 2 (there is a slight gap of less than 10 mm between the side wall part 5 and the base 6 B ). The central upper part 6 T which provides a support surface for supporting the workpiece 7) is arranged away from the side wall part 5 of the plasma chamber 2 (for example, the diameter of the upper part 6 T is 3 / 4 or less of the diameter of the plasma chamber 2). The plasma 12 is configured to exist only on or above the upper part 6 T , for example, on or above the workpiece 7. For example, it is desirable to generate and maintain a plasma 12 comprising an inner plasma region 12 i and an outer toroidal plasma region 12 o . In this way, the higher E-field strength in the outer toroidal plasma region 12 i compared to the inner plasma region 12 o is to achieve uniform film formation and / or etching over the entire workpiece 7, and in particular, to compensate for the loss of plasma species to the periphery of the plasma 12 and the workpiece 7 in order to reduce the edge effect when processing large substrates with a diameter of 300 mm or more.

[0058] The radiation element arranged at the lowermost part of the side wall part 5 of the plasma chamber 2 is arranged on the same plane as the workholder 6, that is, at the same height as the support surface for supporting the workpiece 7.

[0059] The radiating and absorbing elements have essentially the same shape, are implemented as a shortened waveguide (or horn antenna or double-ridged horn antenna), and have a coaxial feed. The operating frequency f belongs to the industrial, scientific, or medical (ISM) bands, for example, 915 MHz, 2.45 GHz, or 5.8 GHz. This is because standard RF components corresponding to these frequencies are readily available.

[0060] In the microwave plasma reactor 1 shown in Figure 1, the plasma chamber 2 is vacuum-sealed. To achieve this, dielectric windows (such as pressurized quartz windows) are placed in front of or inside the radiating and absorbing elements, or the coaxial power supply section is equipped with a hermetic feedthrough coaxial connector.

[0061] Figure 2 is a schematic side cross-sectional view of another embodiment of the microwave plasma reactor 1 of the present invention. The embodiment shown in Figure 2 differs from the embodiment shown in Figure 1 in the following ways: A container 13 (or 13') made of a dielectric and microwave-transmitting material such as alumina, fused silica, quartz, or a glass container is placed inside the plasma chamber 2. The container 13 is mounted on a work holder 6. Alternatively, the work holder 6 may be placed inside the container 13' (as shown by fine dashed lines in Figure 2). The work holder 6 has a diameter of 2 / 3 or less of the diameter of the plasma chamber 2, and is placed only in the central region of the plasma chamber 2, and does not extend into the side walls 5 (in contrast to the work holder 6 shown in Figure 1). The container 13 is vacuum-sealed in the plasma chamber 2, and the plasma chamber 2 may be filled with air. The plasma is configured to be formed inside the containers 13 and 13'. (Nevertheless, the entire enclosure 2 is referred to here as the "plasma chamber.") The top of the container may be a curved dome or ellipsoid shape (indicated by a long dashed line for container 13 and a short dashed line for the alternative container 13'). Process gas is supplied to containers 13, 13' through the gas inlet 8, and / or gas (e.g., process gas or air) is removed / discharged from containers 13, 13' through the gas outlet 9.

[0062] Since the process chamber 2 does not need to be vacuum-sealed, in the microwave plasma reactor 1 of the embodiment shown in Figure 2, no measures are required to vacuum-seal the radiating element 10 and the absorbing element 11.

[0063] Figure 3 is a slightly elevated perspective view of a microwave plasma reactor 1 according to one embodiment of the present invention, with particular emphasis on the emitter and absorber arrays. In this embodiment, the microwave plasma reactor 1 comprises 24 radiating / supplying elements (=emitter array) and 84 absorbing elements (=absorber array). As can be seen from the drawing, the radiating elements forming the emitter array and the absorbing elements forming the absorber array are arranged on the side wall 5 of the plasma chamber 2 and in multiple layers L stacked on top of each other between the base 3 and the upper part 4 parallel to the work holder 6. As a result, the radiating elements 10 and absorbing elements 11 are alternately arranged in four layers L1, and the remaining layer L2 consists only of absorbing elements 11. Layer L2 consists of four upper layers L1. 2、T and the lower two layers L 2、B This corresponds to the following. The radiating elements 10 and absorbing elements 11 within the four layers L1 are arranged from one layer to the next consecutive layer, in the lower layer L 1、L From upper L 1、U They are arranged in a continuous rotational manner. As a result, the radiating element 10 and the absorbing element 11 are arranged in a helical or spiral pattern. The lowest radiating element is positioned on the same plane as the work holder 6, that is, at the same height as the support surface that supports the workpiece 7, and two lower layers L consisting only of absorbing elements 2、B The upper layer L of the absorption element is positioned below the support surface that supports the workpiece 7. 2、T and lower layer L 2、B This ensures that the radiation from the radiating element is unaffected (or only slightly affected) by the plasma chamber 2, thereby enabling precise adjustment of the E-field. The size and shape of the work holder 6 are the same as those shown in Figure 2, and it is positioned exclusively in the central region of the plasma chamber 2.

[0064] Figure 4 is a slightly lower perspective view of a compact, i.e., height-reduced (compared to the one shown in Figure 3) microwave plasma reactor 1 embodiment of the present invention, particularly highlighting the emitter and absorber array. In this embodiment, the number of absorption elements has been reduced by 36, from 84 to 48 (compared to the one shown in Figure 3). As can be seen from the drawing, in this embodiment, the top two layers and the bottom two layers, which consist only of absorption elements, have been removed. On the other hand, the size and shape of the work holder 6 have been modified based on the work holder 6 shown in Figure 1. That is, the work holder 6 has a base 6 that extends almost to the side wall 5 of the plasma chamber 2. B And the central upper part 6, which is positioned away from the side wall portion 5 of the plasma chamber 2. T The system is equipped with the following features. By removing the lowest level / layer 2 and the highest level / layer 2 of the absorption element and reducing the height of the plasma chamber 2, the intensity of the E-field on the inner wall surface of the plasma chamber 6 is maintained at approximately the same level. This means that the degradation of the E-field absorption performance is essentially negligible.

[0065] Figures 3 and 4 also show connectors 14 connected to the coaxial pins 15 of the radiating element 10 and the absorbing element 11, which in these examples are located on the underside of the respective radiating element 10 and absorbing element 11.

[0066] Figure 5a) shows a top cross-sectional view of the microwave plasma reactor 1 of the embodiment (i.e., a view in the direction of the central axis a of the plasma chamber 2), showing a first layer having both microwave emitters 10 and microwave absorbers 11 alternately. Figure 5b) shows a second continuous layer having both microwave emitters 10 and microwave absorbers 11 alternately, similar to the top cross-sectional view. As can be seen from the drawings, the microwave emitters 10 and microwave absorbers 11 arranged in the second continuous layer are rotated (15° in this example) with respect to the microwave emitters 10 and microwave absorbers 11 arranged in the vertically adjacent first layer.

[0067] Figure 6 is a side view of an embodiment of the microwave plasma reactor 1 shown in Figure 4, comprising four layers L1 and two layers L2 above the four layers L1. Each layer L1 contains six radiating elements 10 and six absorbing elements 11, and each layer L2 contains twelve absorbing elements 11. The six layers L are each rotationally offset relative to the layer directly below them. As an example, the dimensions of the cylindrical microwave plasma reactor 1 shown in Figures 4 / 6 are as follows: Diameter D of the plasma chamber 2 C The height is 410 mm, and the height from the base 3 to the top 4 of the plasma chamber 2 is h C It is 535mm. Work holder / base 6 base / bottom 6 B Diameter D P、B D P、B =D C -2mm = 408mm, and height h P、B It is 46mm, and the center / top center 6 of the work holder / base 6 T Diameter D P、T 300mm, height (height from base) h P、T The height is 100mm. This reduces the total height of the work holder / base 6 to h. P This is 146 mm. Typically, the outer torus plasma region 12 of the plasma 12 o The diameter is E field intensity | E pl At |=9.5e3V / m±10%, the value is 200mm. Inner plasma region 12 i The diameter is E field intensity | E pl At |=11.5e3V / m±10%, the value is 150mm. On the other hand, the E-field intensity |E in plasma chamber 2 is 150mm. C The voltage will be less than 18e3V / m.

[0068] The microwave cavities (waveguides) of the radiating and absorbing elements, and the connectors connected to the coaxial pins of the coaxial power supply unit to which microwave power is supplied from one or more microwave generating units, are shown in part 6a). Part 6b) is an enlarged side view showing in more detail the (left) side wall 5 of the microwave plasma reactor 1 in part 6a). Here, it can be seen that the microwave cavities 17 (waveguides) of the radiating and absorbing elements are arranged flush with the inner surface of the plasma chamber side wall 5. The coaxial pins 15 of the coaxial power supply unit are located inside the microwave cavity 17. In the example in part 6b), the connector 14 connected to the coaxial pins 15 is located on the lower surface of the microwave cavity 17, and the coaxial pins 15 are arranged vertically within the microwave cavity 17. To reduce the E-field around the coaxial pin 15 and prevent the generation of unwanted spike plasma around the coaxial pin 15, a dielectric cylinder 16 (or tube) is placed around the coaxial pin 15 in the microwave cavity 17. Near the emitter and absorber waveguide 17, particularly near the alumina cylinder 16 in the waveguide / microwave cavity 17, the E-field intensity may be higher than 18e3V / m. The cylinder 16 may be made of alumina or ceramic material.

[0069] Figure 7 is an exemplary block diagram of microwave output generation of an emitter array according to the present invention. As can be seen from the drawing, each microwave emitter 10 (for example, six emitters in Figure 7) comprises an amplifier 101 with adjustable amplification, a phase shifter 102 with adjustable phase shift, and a radiating element / antenna 103. Furthermore, each microwave emitter 10 is connected to a microwave generation unit 100 (for example, two generation units in Figure 7) that supplies microwave power to the emitter 10. The (beam control / forming) emitter control unit 200 individually adjusts the amplification of each amplifier 101 and the phase shift of each phase shifter 102 in order to focus and change the microwave output from the emitter array to a desired position in the plasma chamber 2. By changing the phase supplied to the emitter 10 by the emitter control unit 200, it is possible to concentrate the radiated E-field at different points P on the surface of the workpiece 7, as shown in Figure 8. By changing the amplification supplied to the emitter 10 by the emitter control unit 200, it is possible to change the intensity / strength of the emitted E-field, thereby changing the density of the plasma generated by the E-field.

[0070] Figure 8 illustrates the spiral-shaped path p / scanning pattern of the focusing points / spots P of the microwave output (E-field) emitted by the emitter array of the microwave plasma reactor of the present invention. The path p consists of a number of individual discrete points P. To ignite the plasma across the entire surface of the workpiece, the emitter control unit 200 successively focuses the microwave output from the emitter array along path p onto individual points P. The plasma is maintained by repeatedly "scanning" the focusing points P of the microwave output (E-field) along this path p (similar to the refresh of a raster display such as a cathode ray tube display, which needs to periodically (re)excite individual pixels to maintain its brightness). Thus, the duration of each repetition must be shorter than the plasma extinction time. The phase shift and amplification settings to achieve the desired plasma shape and density can be stored in the memory of the emitter control unit 200 as a set / array of N × M × 2 (phase and amplitude) values. Here, N is the number of emitters 10 (e.g., N=24), and M is the number of points included in path p (e.g., M=200). These values ​​may be predetermined (offline), calculated (online) based on plasma and process specifications, or calculated in real time as part of a closed-loop control system. In addition to the phase and amplitude values ​​of each point P along path p, a time value representing the length of time the microwave output is radiated to each point P by the emitter array (i.e., residence time) may be stored (→ set / array of N × M × 3 data values). Instead of (or in addition to) the residence time, the point density (i.e., the distance between points in a given region) may be adjusted to control the uniformity of material deposition or etching. [Explanation of Symbols]

[0071] 1. Microwave Plasma Reactor 2 Plasma Chamber 3. Base of the plasma chamber 4. Top of the plasma chamber 5. Side wall of the plasma chamber 6. Work holder, base 6 B Work holder base / bottom 6 T Center / top of the work holder 7 Workpiece, for example, a substrate or wafer 8. Gas inlet for the gas flow system 9. Gas outlet of the gas flow system 10 Microwave emitters 11 Microwave absorption section 12 Plasma 12 i Inner plasma region 12 o Outer torus plasma region 13 Dielectric container mounted on the work holder 13' Dielectric container surrounding the work holder 14 Connector connected to the coaxial pin of the coaxial power supply section 15. Coaxial pins of the coaxial power supply section of the radiating and absorbing elements 16 Dielectric cylinder or tube around the coaxial pin 17. Microwave cavities (waveguides) of radiating and absorbing elements 100 Microwave generation unit 101 Amplifier 102 Phase shifter 103 Radiating elements / antennas 200 Emitter Control Unit / Beam Steering Unit a. The central axis of the plasma chamber (and the common central axis of the emitter and absorber arrays) D C Diameter of the plasma chamber D P、T Diameter of the top of the work holder D P、B Diameter of the work holder base h C Height of the plasma chamber h P Work holder height h P、T Height of the top of the work holder h P、B Height of the work holder base L Layer of radiating and absorbing elements L1 is a layer that includes both a radiating element and an absorbing element. Layer containing only L2 absorption element L 2、T Upper layer containing only an absorption element L 2、B Lower layer containing only absorption elements L 1、L The (lowest) layer contains both radiating and absorbing elements. L 1、U The uppermost layer contains both radiating and absorbing elements. The focus of the p-microwave output moves (repeatedly) along a two-dimensional / three-dimensional path that defines the desired limited space of the plasma. The point where the microwave / microwave power emitted from the P emitter array converges (i.e., the plasma spot).

Claims

1. - A plasma chamber (2) having a base (3), an upper part (4), and a side wall portion (5) extending from the base (3) to the upper part (4), - A work holder (6) is positioned on the base (3) and has a support surface for supporting a workpiece (7) such as a substrate, - A gas flow system that supplies process gas to the plasma chamber (2) and / or discharges gas from the plasma chamber (2), - One or more microwave generating units (100) configured to generate microwaves of frequency (f), - A plurality of microwave emitters (10), each having an amplifier (101), in particular a solid-state amplifier, a phase shifter (102), and a radiating element (103), in particular an antenna, wherein each microwave emitter (10) is connected to at least one of the one or more microwave generating units (100), and the radiating elements (103) of the plurality of microwave emitters (10) are installed in the plasma chamber (2), in particular the side wall (5), forming an emitter array, - One or more microwave absorbing units (11) configured to absorb microwaves of the aforementioned frequency (f), each of the microwave absorbing units (11) having an absorbing element, in particular an antenna terminated with a matching load such as a 50Ω load, and the absorbing elements of one or more of the microwave absorbing units (11) being installed in the plasma chamber (2), in particular the side wall (5), to form an absorber array, - An emitter control unit (200) is configured to individually control the amplification by the amplifier (101) and the phase shift by the phase shifter (102) for each or most of the microwave emitters (10) to generate a desired distribution of microwave output from the emitter array to one or more desired locations within the plasma chamber (2), A microwave plasma reactor equipped with [a specific feature].

2. One or more of the microwave absorbing units (11) are arranged and configured to absorb a portion of the microwave output emitted from the radiating element (103), particularly the scattered and reflected microwave output, so that the radiation from the radiating element (103) is not affected by the plasma chamber (2), and in particular, free-field radiation is essentially generated from the radiating element (103). The microwave plasma reactor according to claim 1.

3. The emitter array and the absorber array are conformal arrays having a common central axis that coincides with the central axis (a) of the plasma chamber (2), and the emitter array is, in particular, arranged alternately with the absorber array, or nested within the absorber array, at least partially. The microwave plasma reactor according to claim 1 or 2.

4. The radiating elements (103) forming the emitter array and the absorbing elements forming the absorber array are arranged on the side wall portion (5) of the plasma chamber (2) and in one or more layers (L) stacked on top of each other between the base portion (3) and the upper portion (4), and in particular the radiating elements (103) and the absorbing elements are arranged in several layers (L). １ ) are arranged alternately in all other layers (L ２ ) consists only of the aforementioned absorption element, and in particular the first number of upper layers (L ２、T ) and / or the lower layer of the second number (L ２、B ) form A microwave plasma reactor according to any one of claims 1 to 3.

5. The radiating element (103) and / or the absorbing element are arranged from one layer to the next consecutive layer, with the lower layer (L １、Ｌ ) to the upper layer (L １、Ｕ They are arranged in a continuous rotational manner, and in particular, the radiating element (103) and the absorbing element are arranged in a helical or spiral pattern. A microwave plasma reactor according to any one of claims 1 to 4.

6. The radiating element (103) and the absorbing element have essentially the same shape. A microwave plasma reactor according to any one of claims 1 to 5.

7. The lowest part (L) of the layer comprising the radiating element (103) １、Ｌ ) is arranged on the same plane as the support surface that supports the workpiece holder (6), in particular the workpiece (7), A microwave plasma reactor according to any one of claims 1 to 6.

8. The radiating element (103) and the absorbing element are composed of a shortened waveguide, a horn antenna, or a double-ridge horn antenna, and in particular have a coaxial feed section and operate in accordance with the frequency (f). A microwave plasma reactor according to any one of claims 1 to 7.

9. The aforementioned frequency (f) is in the range of 500 MHz to 15 GHz, particularly in the range of 900 MHz to 5.8 GHz, and especially in the range of 2 GHz to 2.5 GHz. A microwave plasma reactor according to any one of claims 1 to 8.

10. The emitter control unit (200) is configured to move the focusing point of the microwave output emitted by the emitter array along a desired two-dimensional or three-dimensional path (p) on the work holder (6) in order to generate a plasma (12) having a desired shape within a desired limited space on the work holder (6). A microwave plasma reactor according to any one of claims 1 to 9.

11. To maintain the plasma (12) within a desired confined space, the emitter control unit (200) is configured to essentially repeatedly move the point of focus of the microwave output along the two-dimensional or three-dimensional path (p) that determines the desired confined space, with each repetition time set to be shorter than the plasma extinction time. The microwave plasma reactor according to claim 10.

12. The emitter control unit (200) adjusts the duration and / or output level of the time during which microwaves emitted by the emitter array are concentrated and radiated at a specific point (P) or region on the work holder (6), or adjusts the density of the concentration, thereby correcting non-uniformity in film deposition and etching. A microwave plasma reactor according to any one of claims 1 to 11.

13. The matching load is equipped with a cooling means, which includes, for example, a heat sink using a cooling fluid such as air or liquid, such as water. A microwave plasma reactor according to any one of claims 1 to 12.

14. The plasma chamber (2) is sealed under vacuum. A microwave plasma reactor according to any one of claims 1 to 13.

15. To properly seal the plasma chamber (2), a dielectric window such as a pressurized quartz window is positioned in front of or inside the radiating element (103) and the absorbing element, or the coaxial power supply unit is equipped with a hermetic feedthrough coaxial connector. The microwave plasma reactor according to claim 14.

16. To reduce the E-field around the coaxial pin (15) of the coaxial power supply section and to avoid undesirable spike plasma around the coaxial pin (15), a dielectric layer such as an alumina layer is placed in front of the waveguides of the radiating element (103) and the absorbing element, or a dielectric cylinder or tube (16), such as an alumina or ceramic cylinder or tube (16), is placed around the coaxial pin (15). The microwave plasma reactor according to claim 14 or 15.

17. A container (13, 13') made of a dielectric and microwave-transmitting material such as alumina, fused silica, quartz, or glass container is placed inside the plasma chamber (2), the work holder (6) is placed inside the container (13') or the container (13) is attached to the work holder (6), the container (13, 13') is vacuum-sealed to the plasma chamber (2) which may be filled with air, and the plasma (12) is formed inside the container (13, 13'). A microwave plasma reactor according to any one of claims 1 to 13.

18. The system further includes temperature control means, such as cooling and / or heating means, configured to adjust the temperature of the work holder (6), A microwave plasma reactor according to any one of claims 1 to 17.

19. The plasma chamber (2) further comprises a cooling means configured to cool at least one side wall portion, A microwave plasma reactor according to any one of claims 1 to 18.

20. A method for processing a workpiece (7) such as a substrate, - To provide a microwave plasma reactor (1) according to any one of claims 1 to 19, - Place the workpiece (7) in the work holder (6), - Supply the process gas to the plasma chamber (2) and / or discharge the process gas from the plasma chamber (2), - Microwave power is supplied from one or more microwave generating units (100) to the multiple microwave emitters (10), - By individually controlling the amplification by the amplifier (101) and the phase shift by the phase shifter (102) for each or most of the microwave emitters (10), the radiating elements (103) forming the emitter array generate a desired distribution of microwave output, and ignite and / or maintain a plasma (12) having a desired plasma density at one or more desired locations within the plasma chamber (2), particularly within a desired limited space within the plasma chamber (2). - Form a material layer, particularly a material layer such as diamond or diamond-like carbon (DLC), on the surface of the workpiece (7), or etch the surface of the workpiece (7). method.

21. The method described above is part of a chemical vapor deposition process, particularly a process for depositing a diamond layer or a diamond-like carbon layer on the workpiece (using methane as the process gas). The method according to claim 20.

22. The above method is part of an etching process, particularly a soft etching process, and is particularly characterized in that the energy of the ions in the plasma is less than 10 eV. The method according to claim 20.

23. The amplification and phase shift control of the microwave emitter are adjusted so that the plasma (12) is confined to the upper hemisphere of the workpiece (7), and in particular, in the case of processing using chemical vapor deposition, so that it comes into contact with the workpiece (7). The method according to any one of claims 20 to 22.

24. The amplification and phase shift control of the microwave emitter are adjusted so that the plasma (12) does not come into contact with the workpiece (7), particularly in temperature-sensitive processes, especially when the plasma (12) is used to generate radicals, so that it is confined to a spot or sphere above the workpiece (7). The method according to any one of claims 20 to 22.

25. The amplification and phase shift control of the microwave emitter are adjusted to confine the plasma (12) to a small space within the plasma chamber (2), such as a spot or a sphere, and to move the plasma (12) within the plasma chamber (2) along a desired two-dimensional or three-dimensional path (p), and to change, in particular, the velocity of the plasma (12) and / or the intensity of the plasma (12) as the plasma (12) moves along the path (p). The method according to any one of claims 20 to 24.

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