Transformer-type isolator with RF shielding structure for effective magnetic power transmission

Abstract

An apparatus for a transformer-type isolator used to transmit power to elements of a substrate support used in a plasma chamber is provided. The primary of the transformer-type isolator includes a primary base plate configured to be electrically coupled to ground. A primary ferrite disposed above the primary base plate has a primary circular channel. A primary coil is wound within the primary circular channel. A primary shield is disposed to cover the primary ferrite and the primary coil. The primary shield includes a first plurality of radial segments extending from a primary central region to outside the periphery of the primary ferrite. The extended region of the primary shield has a curved portion for connecting the primary shield to the primary base plate. In one example, the secondary of the transformer-type isolator has a structure similar to the primary and is used together as part of the transformer-type isolator.

Description

[Background technology]

[0001] The present embodiment relates to an isolation transformer having a shielding structure that improves magnetic power transfer and provides isolation from electrostatic field currents. Plasmas have long been employed to process substrates (e.g., wafers) into semiconductor products such as integrated circuits. In many modern plasma processing systems, a substrate may be placed on an RF chuck for plasma processing within a plasma processing chamber. The RF chuck may be biased with an RF signal, using RF voltages ranging from tens to thousands of volts and RF frequencies ranging from tens of kilohertz to hundreds of megahertz. Because the RF chuck also functions as a substrate support, proper control of the RF chuck temperature is an important consideration to ensure reproducible process results.

[0002] Typically, the temperature of the RF chuck is maintained by one or more electric heaters, which may be integrated into or coupled to the substrate support. Power to the electric heaters is typically derived from line AC voltage via appropriate control circuitry to maintain the substrate support at a desired temperature range. By way of example, the electric heaters may be powered by DC, line frequency (e.g., 50 / 60 Hz AC), or AC power in the KHz range.

[0003] Thus, the substrate support must be exposed to significant levels of RF power while simultaneously powering the heaters. The AC circuits powering these heaters can inadvertently draw RF power from the plasma in the chamber, resulting in loss of etch rate, reduced power transfer to the heaters, and / or damage to the AC circuits. In an attempt to solve these problems, it is common to incorporate filters to block static currents. These filters typically employ large LC tank circuits, for example, using a coil wound on a core to provide inductance and a capacitor bank to provide high impedance at selected frequencies.

[0004] Unfortunately, conventional filters suffer from several drawbacks. One is unit-to-unit variability in the coil windings. This variability leads to repeatability issues in the primary resonance. Additionally, parasitic resonances in such RF filters introduce further unpredictability.

[0005] It is against this background that embodiments of the present disclosure arise. Summary of the Invention

[0006] Generally, the embodiments described herein provide an efficient transformer-type isolator that is optimized for efficient power transfer from primary to secondary while implementing a unique shielding configuration that provides efficient isolation from currents returning from the secondary to the primary.

[0007] In one embodiment, an apparatus is provided for a transformer-type isolator used to transmit power to a substrate support element used in a plasma chamber. The primary of the transformer-type isolator includes a primary base plate configured to be electrically coupled to ground. A primary ferrite disposed above the primary base plate has a primary circular channel. A primary coil is wound within the primary circular channel. A primary shield is disposed to cover the primary ferrite and the primary coil. The primary shield includes a first plurality of radial segments extending from a primary central region to outside the periphery of the primary ferrite. The extended region of the primary shield has a curved portion for connecting the primary shield to the primary base plate. In one example, the secondary of the transformer-type isolator has a structure similar to the primary and is used together as part of the transformer-type isolator.

[0008] Another embodiment provides a transformer-type isolator for transmitting power to a substrate support element used in a plasma chamber. The primary of the transformer-type isolator includes a primary base plate configured to be electrically coupled to ground. A primary ferrite is disposed above the primary base plate. The primary ferrite has a primary circular channel. A primary coil is wound within the primary circular channel. A primary shield is disposed to cover the primary ferrite and the primary coil. The primary shield includes a first plurality of radial segments extending from a primary central region to outside a periphery of the primary ferrite and a first bend for connecting the primary shield to the primary base plate. The transformer-type isolator includes a secondary having a secondary base plate configured to be electrically coupled to a radio frequency (RF) ground return of the plasma chamber. The secondary ferrite is disposed above the secondary base plate. The secondary ferrite has a secondary circular channel. A secondary coil is wound within the secondary circular channel of the secondary ferrite. The secondary shield is disposed to cover the secondary ferrite and the secondary coil. The secondary shield includes a second plurality of radial segments extending from the secondary central region to an outer periphery of the secondary ferrite, and a second curved portion connecting the secondary shield to the secondary base plate. The primary shield is oriented to face the secondary shield, spaced apart from the secondary shield.

[0009] In yet another embodiment, a shielding structure for use in a transformer-type isolator is provided. The shielding structure includes a dielectric substrate having a central portion, a substantially flat surface extending radially from the central portion to a peripheral edge, and a curved extension extending from the peripheral edge. A conductive pattern is formed above the dielectric substrate, the conductive pattern forming a plurality of radial segments. Each radial segment has a plurality of slits extending across the substantially flat surface and the curved extension, and each of the plurality of radial segments includes a segment end located near the central portion of the dielectric substrate. The conductive pattern includes a central segment aligned with the central portion, and selected ones of the segment end portions are connected to the central segment.

[0010] Other aspects of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention. [Brief explanation of the drawings]

[0011] The present invention is illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings in which like reference numerals refer to similar elements and in which:

[0012] [Figure 1] FIG. 1 illustrates a system used to process wafers under plasma conditions, according to one embodiment.

[0013] [Figure 2] FIG. 2 provides a more detailed example of a power transmission isolator, including a transformer-type isolator, according to one embodiment.

[0014] [Figure 3A] FIG. 3A shows an exemplary transformer configuration.

[0015] [Figure 3B] FIG. 3B shows a cross-sectional view of the transformer of FIG. 3A and the magnetic field (H) lines.

[0016] [Figure 4] FIG. 4 illustrates a transformer-type isolator, according to one embodiment.

[0017] [Figure 5A] FIG. 5A illustrates an example of slits formed on a dielectric substrate to define multiple radial segments, according to one embodiment. [Figure 5B] FIG. 5B illustrates an example of slits formed on a dielectric substrate to define multiple radial segments, according to one embodiment. [Figure 5C] FIG. 5C illustrates an example of slits formed on a dielectric substrate to define multiple radial segments, according to one embodiment. [Figure 5D]FIG. 5D illustrates an example of slits formed on a dielectric substrate to define multiple radial segments, according to one embodiment.

[0018] [Figure 5E] FIG. 5E shows an exemplary pattern that can be used to construct each of the radial segments, according to one embodiment. [Figure 5F] FIG. 5F shows an exemplary pattern that can be used to construct each of the radial segments, according to one embodiment. [Figure 5G] FIG. 5G shows an exemplary pattern that can be used to construct each of the radial segments, according to one embodiment.

[0019] [Figure 6A] FIG. 6A is an example of modeling that shows how the center region of the shield, without the central patterned cover, leaks current back from the secondary to the primary, according to one embodiment.

[0020] [Figure 6B] FIG. 6B illustrates an example configuration of a conductive pattern that forms a central segment of conductive material, according to one embodiment.

[0021] [Figure 7A] FIG. 7A illustrates an example configuration of a primary and secondary shield used in a transformer-type isolator, according to one embodiment.

[0022] [Figure 7B] FIG. 7B shows another example of a primary and secondary shield having sides that include minimal curvature at the transition to the sides, according to one embodiment.

[0023] [Figure 8] FIG. 8 shows an exemplary orientation of the slits in the primary shield 402, according to one embodiment.

[0024] [Figure 9A] FIG. 9A illustrates an example of a primary shield including a primary side defining an extension having a curved portion, according to one embodiment.

[0025] [Figure 9B] FIG. 9B shows how the primary shield has a top surface that is substantially flat and then curves around the periphery, according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0026] The present invention will now be described in detail with reference to several embodiments illustrated in the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be apparent to one skilled in the art that the present invention may be practiced without some or all of these specific details. In other instances, well-known process steps and / or structures have not been described in detail in order to not unnecessarily obscure the present invention.

[0027] In etch tools, heating the electrostatic chuck is one way to adjust and improve process uniformity. The alternating current (AC) circuits that power these heaters can inadvertently draw RF power from the chamber, resulting in a slower etch rate.

[0028] Radio frequency (RF) filters are commonly employed to block this RF power from returning to the AC circuit of the heater's AC / DC power supply. These filters are traditionally designed as a parallel LC tank with a coil wound on a core (or air core), which, together with a capacitor bank, provides inductance and high impedance at a selected resonant frequency. This filtering approach has inherent drawbacks because the coil windings and their associated primary and parasitic resonances present repeatability challenges. In one embodiment, a transformer approach to RF filtering is believed to help solve some of these problems. Because transformers provide a capacitive rejection response and are resonance-free, this approach is more resistant to repeatability challenges.

[0029] In one configuration, the primary and secondary of the transformer are separated by a physical gap to avoid capacitive coupling of RF from the secondary to the primary, the latter being connected to sensitive AC and / or DC circuits. RF is inherently present in the secondary of the transformer due to common-mode coupling, for example, to the RF ground of the chamber hardware. However, simply having a large physical gap between the primary and secondary of the transformer to solve the aforementioned problem would dramatically reduce the efficiency of power transmission. According to one embodiment, the isolation transformer is configured with an RF shield to block electromagnetic field penetration and / or electrostatic currents returning to the primary, while also allowing efficient magnetic force transmission and penetration from the primary to the secondary to power the chuck heater. In one embodiment, the physical gap may be between about 0.5 mm and about 30 mm and may be configurable in the range of several kilovolts (KVs) to prevent RF power loss from the secondary to ground and the primary circuit. For example, the DC voltage across the gap may be between 1 KV and 15 KV. Therefore, one purpose of the physical gap between the secondary and primary is to provide RF isolation as well as DC isolation, yet provide efficient power transfer.

[0030] For example, the RF shield must be able to block RF frequencies from 400 kHz to 300 MHz at 500 W to 50 kW RF power, while also transmitting magnetic power (0.5 kW to 50 kW) at switching frequencies from 100 kHz to 1 MHz. In one embodiment, the RF shield disclosed herein has multiple slits in multiple layers to minimize losses due to eddy currents that occur when magnetic fields couple through the shield. Generally, incorporating slits into the RF shields (primary and secondary shields) allows currents generated by RF power in the chamber to be directed to ground. Furthermore, the slits are designed to prevent excessive eddy current swirling, which would otherwise reduce magnetic penetration and efficient power delivery to the heater. Increasing the number of slits also limits the area in which eddy currents can loop. Therefore, reducing eddy currents increases the coupling efficiency of the current required to induce it in the secondary coil. Therefore, the RF shield configuration of this embodiment not only reduces capacitive coupling, thereby blocking most, if not all, of the current returning from the RF power in the chamber, but also includes slits designed to reduce eddy currents that reduce the magnetic penetration efficiency from the primary to the secondary.

[0031] FIG. 1 illustrates a system 100 used to process a wafer 106 under plasma conditions, according to one embodiment. The system 100 is a general system including a substrate support 102 that supports the wafer 106. The substrate support 102 includes a load 108 and is shown receiving power from an RF supply 116. The RF supply 116 is coupled to a match 114, the output of which provides power across an RF supply rod 270 that couples to the substrate support 102. Other structural features of the plasma chamber 101 are not shown, although it is understood that other structural features of the plasma chamber 101 may be included as known in the art. In this example, the load 108 represents a heater 110 that receives power from a power transfer isolator 120. The power transfer isolator 120 is coupled to an AC line 118. The AC line 118 communicates through a transformer-type isolator 122 that provides power to the heater 110 within the substrate support 102. Exemplary components and circuits used to provide a type of universal RF isolation are shown and described in U.S. Patent RE47,276E, reissued March 5, 2019, which is incorporated herein by reference.

[0032] In one embodiment, the transformer-type isolator 122 is configured to effectively transfer power via magnetic intrusion across a transformer structure with one or more RF shields, while substantially blocking current intrusion from RF power used to generate plasma in the plasma chamber 101 during processing. Also, the heater 110 is shown as a single heater. However, in some embodiments, multiple heaters will be incorporated into the substrate support 102. For example, some embodiments use four multi-zone heaters, while other configurations will utilize an array of individually controlled heaters to strategically provide micro-controlled heating levels in different regions of the substrate support 102. By way of example, some heater arrays may include up to 150 or more individual heaters, depending on the design of the substrate support.

[0033] FIG. 2 provides a more detailed example of a power transfer isolator 120, including a transformer-type isolator 122, according to one embodiment. As shown, the power transfer isolator 120 includes a power factor correction (PFC) circuit 202 configured to receive an AC line 118 signal and output a line direct current (DC). The AC line 118 signal may be a 50 Hz or 60 Hz signal, depending on the supply. The line DC is then fed to a chopper circuit 204. The chopper circuit 204 converts the line DC to an AC signal using an inverter. In one example, the AC signal output from the chopper circuit 204 generates a square AC signal at a frequency between about 20 kHz and about 1000 kHz. In one example, the square AC signal may have a frequency of about 85 kHz. The power provided by the square AC signal may be between about 0.5 kilowatts (kW) and about 50 kW, and in one example, about 16 kW.

[0034] Thus, a square AC signal is provided to the primary coil 230a of the transformer-type isolator 122. As shown schematically, a primary ferrite 232a is used to contain the primary coil 230a, as will be described in more detail below. A primary shield 240a is shown positioned over the primary coil 230a and primary ferrite 232a. The primary shield 240a is coupled to ground 250. The secondary coil 230b, secondary ferrite 232b, and secondary shield 240b are shown oriented opposite the primary shield 240a while maintaining a separation gap. The secondary shield 240b is shown connected to ground 250 via an RF ground return 252 of the plasma chamber 101.

[0035] As described above, when plasma 104 is generated in plasma chamber 101, RF returning from plasma 104 to ground travels through ground 250, and secondary shield 240b is connected to ground 250. Thus, transformer-type isolator 122 has complementary and opposing shields separated by a gap, the shields having a slit pattern designed to reduce eddy currents and improve magnetic field transmission of power to a load (e.g., one or more heaters in the substrate support) while substantially blocking currents arising from RF returning to plasma chamber 101.

[0036] In one example, the gap separation between shields 240a / 240b may range from about 0.5 mm to about 30 mm. This gap separation may create a capacitance of about 30 picofarads (pF) to about 100 pF. The voltage across the gap separation may be between about 0.5 kilovolts (KV) to about 50 KV. In some embodiments, the voltage across the gap separation may be between about 1 kilovolt (KV) to about 15 KV.

[0037] The secondary coil 230b in FIG. 2 is shown connected to a secondary circuit 210. The secondary circuit 210 can include programming circuitry for controlling the power level of a particular heater within the substrate support. A controller interface 208 can be coupled to the secondary circuit 210, which communicates with the system controller 206. The system controller 206 can configure the secondary circuit 210 to apply a programmed amount of power to each of the heaters within the substrate support to achieve fine-tuning of the temperature across the surface of the substrate, thereby improving etch uniformity. A rectifier circuit 214 can be provided and implemented to adjust the supply of power to a particular heater based on control from the secondary circuit 210. Accordingly, the output of the rectifier circuit 214 is configured to connect to one or more heaters 110 within the substrate support of the plasma chamber 101.

[0038] As mentioned above, the number of heaters will depend on the heater configuration within the substrate support. Some substrate supports are multi-zone substrate supports that are provided with specific levels of power. Some substrate supports include an array of heaters that are controlled and fine-tuned according to the needs of the process and temperature changes to improve the uniformity of the etch operation. Lam Research Corporation, the assignee of the present application, has implemented these types of heater arrangements, which are referred to as "Hydra heaters" or "Hydra-ESCs." Examples of such heaters can be found in U.S. Patent Application Publication No. 2014 / 0220709A1, which is incorporated herein by reference.

[0039] FIG. 3A illustrates an exemplary transformer configuration. This transformer configuration is provided to illustrate an exemplary structure of the component parts. With respect to the primary, the component includes a primary base plate 302a, a primary ferrite 232a, and a primary coil 230a. With respect to the secondary, the component includes a secondary base plate 302b, a secondary ferrite 232b, and a secondary coil 230b. In this illustration, the primary is configured and positioned opposite the secondary such that the primary and secondary coils 230a, 230b face each other. This illustration also illustrates an exemplary direction in which current 231 flows through the primary coil 230a and the secondary coil 230b. Each of the coils 230a, 230b, in one embodiment, is wound into an annular configuration within a circular channel formed within the respective ferrite 232a, 232b.

[0040] In one configuration, the coils 230a, 230b are made from Litz wire. Litz wire is a multi-strand wire or cable used to transmit alternating current (AC) at radio frequencies. Therefore, the primary and secondary coils 230a / b are shown as blocks in the diagram. However, the coils are actually wound multiple times around channels defined in each of the primary ferrite 232a and secondary ferrite 232b. The number of turns in each of the coils 230a, 230b will vary depending on the voltage and ratio being transmitted across the transformer.

[0041] 3B shows a cross-sectional view of the transformer configuration of FIG. 3A and illustrates how magnetic fields (H) are generated when current flows in the direction of current 231. These induced magnetic fields (H) show a concentration of magnetic fields returning in a direction 330 based on the direction of current 231 through a central region of the transformer configuration.

[0042] FIG. 4 illustrates a transformer-type isolator 122 according to one embodiment. In this embodiment, a primary shield 402a is positioned to cover the primary ferrite 232a and the primary coil 230a. A secondary shield 402b is positioned to cover the secondary ferrite 232b and the secondary coil 230b. The primary shield 402a is configured to face the secondary shield 402b, thereby separating the shields 402a, 402b by a gap. As also shown, the primary shield 402a extends downward to connect to the primary base plate 302a. The primary shield 402a is also shown to include a plurality of slits defining radial segments extending from the center of the shields 402a / 402b to an extension region 504d outside the periphery 504e. The extension region 504d is shown extending downward to the primary base plate 302a. The perimeter 504e is shown as the diameter where the top of the shield 402a begins to bend, curve, or curl toward one of the base plates 302a, 302b. Thus, outside the perimeter 504e of each shield 402a, 402b, there is an annular region that extends beyond the substantially flat top surface of each shield 402a, 402b. It should be understood that the "substantially flat" top surface of each shield 402a, 402b may have surface variations, slight slopes, or small curvatures introduced during manufacturing and / or design. The annular region is shown to bend relative to the base plates 302a, 302b.

[0043] The secondary shield 402b has a similar structure whereby the shield 402b includes a plurality of slits that define radial segments that extend from the center to the periphery of the secondary shield 402b before extending upward toward the secondary base plate 302b. As discussed above, when the transformer-type isolator 122 is implemented in a configuration similar to that of Figure 1 or 2 for supplying power to the heater, the primary base plate 302a is connected to ground and the secondary base plate 302b is connected to plasma chamber ground.

[0044] 5A-5D show examples of slits 560 formed on a dielectric substrate to define multiple radial segments 502. As shown, the radial slits 560 are configured to divide the surfaces of the primary and secondary shields 402a, 402b into regions that reduce the swirling of eddy currents 350. The direction of the H-field is shown concentrated in the central region of each primary and secondary shield 402a, 402b. This is identified as the H-field 330 entering the primary shield 402a, marked with an "x," while the H-field 340 exiting the primary shield 402a is marked with a "dot." It should be understood that the H-field 340 exiting the primary shield 402a occurs across the entire surface of the shield 402a.

[0045] Therefore, by dividing the shields 402a, 402b with the slits 560 to form radial segments 502, the swirling of eddy currents that occurs when the H-field 340 passes through the shields 402a, 402b can be reduced. Furthermore, because each shield 402a, 402b extends beyond the periphery 504e facing the opposing shield 402a, 402b and extends toward, or downward or upward from, its respective grounded base plate 302a, 302b, the effects of power consumption due to eddy currents can be reduced. More specifically, by creating the radial segments 502 and extension regions 504d outside the periphery 504e facing each shield 402a, 402b, the resistance of the path that the eddy currents must traverse in each radial segment 502 is increased.

[0046] As is well known, power is equal to the square of the current multiplied by the resistance. In the configurations shown in FIGS. 5A-5D, resistance is shown to increase as eddy currents travel along each radial segment 502 as the segments 502 extend beyond the periphery 504e and into the respective base plates 302a, 302b, increasing the length the eddy currents must travel between the center of the shields 402a, 402b and ground. Thus, the radial segments 502 and their extended regions 504d also act to reduce power dissipation, thereby reducing heat generated by the flowing eddy currents. Therefore, increasing the resistance path in each radial segment 502 reduces the current flow of eddy currents in each radial segment 502. By way of example, the contribution of current to power dissipation may be more significant than the contribution of resistance due to a quadratic term.

[0047] This combination of features allows the greatest amount of magnetic flux to be transferred between the primary and secondary in the area where the ferrites 232 a, 232 b face each other. This structure also provides reduced capacitive coupling, thereby substantially blocking current flowing from the plasma from penetrating from the secondary back into the primary of the transformer isolator 122. Overall, this structure provides efficient magnetic force transfer between the primary and secondary to power the heater of the substrate support in the plasma chamber, while reducing current penetrating back into the primary.

[0048] 5E-5G show exemplary patterns that can be used to construct each of the radial segments 502. FIG. 5E shows how each radial segment 502 itself can have a slit 560. The radial segments 502 can have a segment end 503 closest to the center of their respective shields 402a and 402b. Each radial segment 502 is defined throughout the dielectric material on which the conductive patterns 820 are formed. Between the conductive patterns 820, slits 560 leave the dielectric material exposed. As described below, the dielectric material is preferably defined by a single substrate upon which all of the radial segments 502 are patterned, on which the slits 560 that define the radial segments 502 and the slits 560 formed within the radial segments 502 are also formed.

[0049] 5F shows one example in which conductive pattern 820 can take on any number of configurations. In some embodiments, shield 402a or 402b may have slits 560 within radial segment 502, in addition to the slits 560 that define radial segment 502-1. Other configurations may have fewer or more slits, depending on the operating frequency, power transmission needs, and the particular implementation of transformer-type isolator 122.

[0050] To increase the efficiency of power transfer between the primary and secondary, a number of patterns, shapes, and configurations can be selected to fine-tune and control the flow of eddy currents in each radial segment 502. That is, by reducing the flow of eddy currents in the shields 402a, 402b, the coupling efficiency of the currents being induced through the primary to the secondary can be increased. FIG. 5G shows another example of a radial segment 502-2, in which the conductive pattern 820 includes more slits 560 oriented toward the center of the radius of the radial segment 502. In some embodiments, it may be desirable to increase the number of slits 560 closer to the center of the shields 402a, 402b. In other embodiments, it may be desirable to increase the number of slits 560 in regions of the shields 402a, 402b that have more surface area, such as the outer diameter. By way of example, it may be desirable to decrease the number of slits 560 in the central region and increase the number of slits 560 in the outer region to controllably reduce the flow of eddy currents and maximize the efficiency of power transfer between the primary and secondary.

[0051] FIG. 6A illustrates an example of modeling that shows how an undesirable direct coupling 602 can occur if the central regions of shields 402a and 402b are left without conductive patterning. In this modeling, it is assumed that the slits 560 forming radial segments 502 act to adequately block electric field leakage. However, the central hole region is shown to represent optical transparency that may allow current to penetrate from the secondary to the primary. In the context of the example, "hole" refers to the absence of a conductive pattern, since shields 402a and 402b are formed from a dielectric substrate having a conductive pattern formed thereon. As described above, the transformer-type isolator is configured to substantially block current penetration from the secondary to the primary while allowing efficient magnetic field penetration from the primary to the secondary, thereby powering a heater in a substrate support.

[0052] FIG. 6B illustrates an example configuration of the conductive pattern forming the central segment 502b. The central segment 502b is shown to include four sections defined by dividing a circular conductive pattern into four. These sections, in one embodiment, are four pie sections. It should be understood that other patterns may be formed for the central segment 502b. However, in this configuration, it is desirable that not all of the radial segment ends 502a of the radial segments 502 are in electrical contact with the central segment 502b. By way of example, one configuration is designed so that the connection 604 of one of the radial segment ends 502a is in electrical contact with each portion of the central segment 502b. As illustrated, the central segment 502b has four sections, and only one radial segment end 502a makes a connection 604 with each portion of the central segment 502b. In this manner, each portion of the central segment 502b functions as a kind of extension to the radial segment 502 to which its radial segment end 502a is connected.

[0053] FIG. 7A illustrates an example configuration of a primary shield 402a and a secondary shield 402b used in a transformer-type isolator 122. In this example, the shields 402a and 402b each have a gap-facing surface. As described herein, the gap-facing surfaces of each shield 402a / 402b are respective regions of the shield 402 that are oriented to face each other, e.g., from a central region to an outer region. The opposing gap-facing surfaces are oriented to define a gap separating the primary from the secondary. In one embodiment, the gap-facing surfaces of each shield 402a / 402b are aligned with each other. In another embodiment, the gap-facing surfaces of each shield 402a / 402b are not aligned with each other, e.g., may be misaligned. Additionally, the primary base plate 302a is shown connected to AC ground 250. The secondary base plate 302b is connected to RF common ground return 260. The opposing gap-facing surfaces of the shields 402 are configured to be substantially flat, with curved portions without sharp edges extending to peripheral edges 504e where they transition to the respective primary and secondary sides 402a' and 402b'. As shown, the curved portions are substantially free of hard corners or edges to allow eddy currents to flow efficiently within the segments.

[0054] The bends that transition the gap-facing surfaces of the primary shield 402a to the primary side 402a' are shown connected to the primary base plate 302a by the primary ring 702a. The primary ring 702a electrically connects the primary shield 402a to AC ground 250. Similarly, the bends of the secondary shield 402b connect the gap-facing surfaces of the secondary shield 402b to the secondary side 402b', which is then connected to the secondary base plate 302b by the secondary ring 702b. Incorporating bends into the transitions at the periphery 504e of each shield 402 has the beneficial effect of reducing eddy current power losses. That is, eddy currents are allowed to efficiently traverse from the opposing gap-facing surfaces along the radial segment 502 gradually to the extended regions of the shield 402 without causing heat buildup that would occur if the edges were sharp. The extended regions are shown as the primary side 402a' and the secondary side 402b', respectively.

[0055] Additionally, the extended regions of the shield 402, including the bends and sides, i.e., primary side 402a' and secondary side 402b', effectively extend the length that eddy currents must traverse, thereby increasing resistance and helping to reduce power dissipation. As an example, one eddy current simulation operating at 80 kHz found that the patterned radial segments 502 with bends were effective in achieving eddy current power dissipation of less than 50 watts, even considering the higher dissipation areas aligned with the ferrite regions. In some regions throughout the grooved shield 402, eddy current power dissipation was substantially lower, e.g., in the range of 2 to 20 watts. The bends also significantly reduce the risk of arc-over events and provide better standoff for high voltages.

[0056] In some embodiments, the shield 402 can extend radially outward without including bends. However, including bends can reduce the overall diameter of the shield 402 of the transformer isolator 122, thereby reducing capacitive coupling. Overall, these features act to increase the efficiency of power flux transfer between the primary and secondary ferrites while blocking current intrusion from the plasma chamber back to the primary.

[0057] FIG. 7B illustrates another example in which the primary shield 402a and secondary shield 402b each include minimal curvature at the transition between the gap-facing surface and the side. For example, the primary shield 402a is shown transitioning to the primary side 402a″ with a reduced curvature connection, as is the transition between the secondary shield 402b and the secondary side 402b″. This illustration is shown as an alternative embodiment where a smaller diameter footprint is desired, frequency and power requirements do not require as much eddy current reduction to achieve desired operating parameters, and high voltage standoff requirements are less restrictive. In one embodiment, the coils 230a, 230b are made from Litz wire, with strands shown by way of example in FIG. 7B. The coils 230a, 230b in FIG. 7A are shown as block diagrams for simplicity, although it should be understood that in one embodiment they may also be defined by Litz wire.

[0058] FIG. 8 illustrates an exemplary orientation of the slits 560 in the primary shield 402a. As illustrated, the inner region 504a of the radial segment 502 is closer to the central segment 502b of the transformer-type isolator 122. As described above with reference to FIG. 6B, the segment end 503 may be connected to the central segment 502b. The radial segment 502 includes a middle region 504b disposed substantially above the primary coil 230a. As illustrated, more slit area is present in the middle region 504b relative to the inner region, resulting in more slits 560 and, respectively, more conductive patterns 820. In the outer region 504c, the slits 560 and conductive patterns 820 extend from the middle region 504b. In one embodiment, the conductive patterns 820 are made of copper. In another embodiment, the conductive pattern material can be silver-plated copper. In another embodiment, the conductive pattern material can be aluminum. The thickness of the conductive pattern 820 is selected for efficient isolation of RF return current (e.g., flow from the plasma through the secondary and back to the primary). In one embodiment, the thickness is selected based on a skin depth defined for a particular operating frequency. It should be understood that the skin depth may vary with different frequencies and materials used for the conductive pattern 820.

[0059] The extension region 504d extends beyond the periphery 504e of the flat portion of the primary shield 402a. In one embodiment, as shown in FIG. 7A, the extension region 504d can include a curved portion and a primary side 402a' that connects to ground. As described above, the primary coil 230a is defined by wrapping Litz wire multiple times within a channel defined in the primary ferrite 232a. This description is provided for the primary; however, a similar structure is provided for the secondary. In one embodiment, each of the multiple radial segments 502 of the primary shield 402a has a conductive pattern that defines radial slits. The conductive pattern extends from the center to the outer edge of the primary shield 402a, thereby electrically connecting the conductive pattern to the primary base plate 302a, which is coupled to ground.

[0060] FIG. 9A illustrates an example of a primary shield 402a including a primary side 402a' that defines an extended region 504d. As shown, each radial segment 502 of the primary shield 402a transitions to the primary side 402a' with a curvature that lacks sharp edges. The primary side 402a' is shown connected to the primary base plate 302a using a primary ring 702a. In this example, the central segment 502b is connected to the segment end 503, and connections 604 provide electrical connections between the shield's respective conductive patterns, as described in FIG. 6B. FIG. 9B illustrates how the primary shield 402a includes a substantially flat top surface having a length L1. The extended region 504d of the primary shield 402a extends the length traversed by eddy currents by an additional length L2. As discussed above with reference to FIG. 7A, the additional length of the radial segments 502 increases resistance and, therefore, reduces power dissipation due to eddy currents generated during operation.

[0061] In one embodiment, it is desirable for the thickness of the conductive pattern 820 to be no thicker than the skin depth so as to achieve efficient magnetic penetration from the primary to the secondary. Thus, a trade-off is made in selecting the thickness of the conductive pattern 820: on the one hand, it must be thick enough to block return current penetration from the plasma, while at the same time allowing efficient magnetic penetration from the primary to the secondary to power the heater in the substrate support of the plasma chamber. It should be understood that the skin depth may vary depending on the operating frequency and the plasma chamber in which the transformer-type isolator 122 is used.

[0062] In some embodiments, the thickness of the conductive pattern 820 is optimized when multiple frequencies are used. For example, higher frequencies, e.g., frequencies above 60 MHz, may be used, while lower frequencies, e.g., frequencies below 400 kHz, may be used. In such cases, the skin depth and material used for the conductive pattern 820 are considered to determine an appropriate thickness for the conductive pattern 820 that achieves a balance between insulation from the electromagnetic field penetrating back from the plasma and the efficiency of magnetic penetration transferred from the primary to the secondary. That is, a thickness of the conductive pattern 820 less than the skin depth can still provide efficient insulation and efficient power transmission. In various implementations, the operating frequency may range from below 400 kHz to approximately 100 MHz.

[0063] In one embodiment, the shielding structure itself is disclosed. The shielding may be used on one side of the transformer (e.g., either the primary or secondary) or on both sides, as shown in the exemplary transformer-type isolator 122. The shielding structure includes a dielectric substrate having a circular shape extending from a center of the circular shape to an outer diameter. In another example, the top or gap-facing surface of the shielding structure may be square, rectangular, or n-sided. The substrate has a flat surface extending from the center to the periphery and a curved extension extending from the periphery to the outer diameter. A conductive pattern is formed above the dielectric substrate. The conductive pattern includes multiple radial segments that extend to the outer diameter to cover the flat surface and the curved extension. Each radial segment includes multiple slits. Each of the multiple radial segments includes a segment end located near the center of the dielectric substrate. The conductive pattern includes a central segment, and selected ones of the segment ends connect to the central segment.

[0064] In some embodiments, the shielding structure may be a consumable part: over time, the shielding may wear out and need to be replaced to maintain the transformer-type isolator.

[0065] Embodiments may be practiced with a variety of computer system configurations, including handheld devices, microprocessor systems, microprocessor-based or programmable domestic appliances, minicomputers, mainframe computers, etc. Embodiments may also be practiced in distributed computing environments where tasks are performed by remote processing devices that are linked through a network.

[0066] With the above embodiments in mind, it should be understood that the embodiments can employ various computer-implemented operations involving data stored in computer systems. These operations require physical manipulation of physical quantities. Any of the operations described herein that form part of the embodiments are useful machine operations. The embodiments also relate to devices or apparatus for performing these operations. The apparatus may be specially configured for the required use, such as a special-purpose computer. When defined as a special-purpose computer, the computer may be operable for the special use, yet may also perform other processes, program execution, or routines that are not part of the special use. Alternatively, the operations can be processed by a general-purpose computer selectively activated or configured by one or more computer programs stored in computer memory, cache, or retrieved over a network. If the data is retrieved over a network, the data may be processed by other computers on the network, e.g., a cloud of computing resources.

[0067] One or more embodiments may also be fabricated as computer-readable code on a computer-readable medium. A computer-readable medium is any data storage device that can store data which can then be read by a computer system. Examples of computer-readable media include hard drives, network-attached storage (NAS), read-only memory, random-access memory, CD-ROMs, CD-Rs, CD-RWs, magnetic tape, and other optical and non-optical data storage devices. The computer-readable medium may include computer-readable tangible media distributed over network-coupled computer systems so that the computer-readable code is stored and executed in a distributed fashion.

[0068] The foregoing description of the embodiments has been provided for purposes of illustration and description. The foregoing description of the embodiments is not intended to be exhaustive or to limit the invention. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment and, where applicable, can be interchanged and used in selected embodiments even if not specifically shown or described. Furthermore, individual elements or features of a particular embodiment may be varied in various ways. Such variations should not be considered a departure from the invention, and all such modifications are intended to be included within the scope of the invention.

[0069] The foregoing embodiments have been described in some detail for purposes of clarity of understanding. However, it will be apparent that certain changes and modifications may be practiced within the scope of the appended claims. The present embodiments are therefore to be considered as illustrative and not restrictive, and the embodiments are not to be limited to the details given herein, but may be modified within the scope and equivalents of the claims. The present invention can be realized, for example, in the following manner. Application example 1: 1. A transformer-type isolator for transmitting power to an element of a substrate support used in a plasma chamber, comprising: It is primary, a primary base plate configured to be electrically coupled to ground; a primary ferrite disposed above the primary base plate and having a primary circular channel; a primary coil wound within the primary circular channel; a primary shield disposed over the primary ferrite and the primary coil, the primary shield including a first plurality of radial segments extending from a primary central region to an outer periphery of the primary ferrite and a first curved portion for connecting the primary shield to the primary base plate; and a first order including It is secondary, a secondary base plate configured to electrically couple to a radio frequency (RF) ground return of the plasma chamber; a secondary ferrite disposed above the secondary base plate and having a secondary circular channel; a secondary coil wound within the secondary circular channel of the secondary ferrite; a secondary shield disposed over the secondary ferrite and the secondary coil, the secondary shield including a second plurality of radial segments extending from a secondary central region to an outer periphery of the secondary ferrite and a second curved portion for connecting the secondary shield to the secondary base plate; and a secondary including Equipped with 1. A transformer-type isolator, wherein the primary shield is oriented to face the secondary shield and spaced apart from the secondary shield. Application example 2: 2. The transformer-type isolator of claim 1, each of the first plurality of radial segments having a first plurality of conductive patterns defining a first plurality of radial slits extending from the primary central region to outside the periphery of the primary ferrite; the second plurality of radial segments having a second plurality of conductive patterns defining a second plurality of radial slits extending from the secondary central region to outside the periphery of the secondary ferrite. Application example 3: 2. The transformer-type isolator of claim 1, a transformer-type isolator, wherein each of the first plurality of radial segments of the primary shield and the second plurality of radial segments of the secondary shield is formed from a dielectric substrate, the dielectric substrate having the conductive pattern thereon, such that the conductive pattern on the primary shield faces the conductive pattern on the secondary shield. Application example 4: 4. The transformer-type isolator of claim 3, a transformer-type isolator, wherein the dielectric substrate of each of the primary shield and the secondary shield includes the first and second curved portions that extend outside the periphery. Application example 5: 2. The transformer-type isolator of claim 1, The primary shield and the secondary shield include corresponding center segments. Application example 6: 6. The transformer-type isolator of claim 5, A transformer-type isolator, wherein each central segment is defined from a dielectric substrate having a conductive pattern. Application example 7: 6. The transformer-type isolator of claim 5, a transformer-type isolator, wherein the first and second pluralities of radial segments of the primary and secondary shields extend to the respective central segments, and wherein fewer than all of the first and second pluralities of radial segments are connected to the respective central segments. Application example 8: 8. The transformer-type isolator of claim 7, Each central segment includes a plurality of portions; A transformer-type isolator, wherein each section is electrically connected to only one of the first plurality of radial segments or one of the second plurality of radial segments. Application example 9: 2. The transformer-type isolator of claim 1, the first plurality of radial segments includes a first plurality of radial slits, and the second plurality of radial segments includes a second plurality of radial slits; The first and second plurality of radial slits are configured to reduce current penetration toward the primary and simultaneously increase magnetic field penetration toward the secondary, the current being a return current from plasma in the plasma chamber to ground, and the magnetic field being used to transmit power to the element, a transformer-type isolator. Application example 10: 2. The transformer-type isolator of claim 1, the first plurality of radial segments includes a first plurality of radial slits, and the second plurality of radial segments includes a second plurality of radial slits; A transformer-type isolator configured such that the first and second plurality of radial slits help reduce swirling eddy currents and allow current generated from plasma in the plasma chamber to flow to the ground and to the RF ground return. Application example 11: 2. The transformer-type isolator of claim 1, A transformer-type isolator, wherein the first and second bends are free of sharp corners or edges. Application example 12: 12. The transformer-type isolator of claim 11, a transformer-type isolator, wherein each of the first and second curved portions includes an upper curve and a lower curve, the upper curve transitioning from a flat region to a side region, and the lower curve transitioning from the side region to a connection to the ground or RF ground return. Application example 13: 2. The transformer-type isolator of claim 1, the first plurality of radial segments includes a first plurality of radial slits, and the second plurality of radial segments includes a second plurality of radial slits; a transformer-type isolator, wherein the first and second pluralities of radial slits are configured to reduce swirling of eddy currents, and an outer diameter region of the primary shield includes a larger area with radial slits than an inner diameter region of the primary shield. Application 14: 2. The transformer-type isolator of claim 1, the primary and secondary shields are formed from a dielectric substrate and include a plurality of conductive patterns disposed on the dielectric substrate; A transformer-type isolator, wherein the thickness of the plurality of conductive patterns is approximately within a range of a skin depth depending on a target operating frequency of the plasma chamber and the type of material of the plurality of conductive patterns. Example 15: 2. The transformer-type isolator of claim 1, A transformer-type isolator, wherein the element is a heater. Application 16: 2. The transformer-type isolator of claim 1, A transformer-type isolator, wherein the primary coil is interconnected to an AC power source and the secondary coil is interconnected to the element, and the transformer-type isolator helps reduce capacitive coupling of RF return current back to the AC power source while effectively transferring power to the element through increased magnetic field penetration. Application 17: 2. The transformer-type isolator of claim 1, a transformer-type isolator, wherein the primary shield and the secondary shield are formed from a dielectric substrate and include a plurality of conductive patterns disposed on the dielectric substrate, the material type of the plurality of conductive patterns is one of copper, silver, or aluminum, the target operating frequency of the plasma chamber is between approximately 400 kHz and approximately 100 MHz, and the thickness of the plurality of conductive patterns is set based on a skin depth associated with the material type and the target operating frequency. Application 18: 1. An apparatus for a transformer-type isolator used to transmit power to an element of a substrate support used in a plasma chamber, the primary of the transformer-type isolator comprising: a primary base plate configured to be electrically coupled to ground; a primary ferrite disposed above the primary base plate and having a primary circular channel; a primary coil wound within the primary circular channel; a primary shield disposed over the primary ferrite and the primary coil, the primary shield including a first plurality of radial segments extending from a primary central region to outside a periphery of the primary ferrite; Equipped with The apparatus wherein the extension region of the primary shield has a bend for connecting the primary shield to the primary base plate. Application 19: 20. The apparatus of claim 18, the extension region increases the length of the primary shield away from the primary ferrite, thereby reducing power dissipation in a region of the primary shield where induced eddy currents are directed substantially above the primary ferrite. Example 20: 20. The apparatus of claim 18, each of the first plurality of radial segments of the primary shield has a conductive pattern defining a radial slit, the conductive pattern extending from the primary central region to an outer edge of the primary shield and electrically connecting to the primary base plate, which is coupled to ground. Example 21: 20. The apparatus of claim 18, each of the first plurality of radial segments of the primary shield is formed from a dielectric substrate having a conductive pattern thereon, the conductive pattern extending from the primary central region of the primary shield to the extended region of the primary shield having the curved portion. Application example 22: 20. The apparatus of claim 18, The apparatus, wherein the primary shield has a central segment. Application 23: 23. The apparatus of claim 22, the central segment has a conductive central pattern, the primary shield includes a conductive pattern defining the first plurality of radial segments and radial slits, and selected inner edges of the first plurality of radial segments electrically connect to selected ones of the conductive central patterns. Application 24: A shielding structure for use in a transformer-type isolator, comprising: a dielectric substrate having a central portion, a flat surface extending radially from the central portion to a peripheral edge, and a curved extension extending from the peripheral edge; a conductive pattern formed above the dielectric substrate, the conductive pattern forming a plurality of radial segments, each radial segment having a plurality of slits extending to cover the flat surface and the curved extension, each of the plurality of radial segments including a segment end located near the center of the dielectric substrate; Including, A shielding structure, wherein the conductive pattern includes a central segment aligned with the central portion, and selected ones of the segment ends are connected to the central segment. Example 25: 25. The shielding structure of claim 24, A shielding structure wherein said curved extension has no sharp corners or edges. Application 26: 25. The shielding structure of claim 24, The shield structure, wherein the flat surface has a circular shape. Application 27: 25. The shielding structure of claim 24, The shield structure wherein the central segment is defined by four pie sections. Application 28: 28. The shielding structure of claim 27, A shielding structure in which each of the four pie sections of the central segment is connected to only one segment end. Application 29: 25. The shielding structure of claim 24, The shielding structure, wherein the curved extension includes one or more curves and is configured to be attached to a ground connection for coupling the conductive pattern to ground. Example 30: 25. The shielding structure of claim 24, The dielectric substrate is configured to be disposed above a ferrite and a coil when used in the transformer-type isolator. Example 31: 31. The shielding structure of claim 30, The periphery of the shielding structure is located beyond the outer edge of the ferrite.

Claims

1. 1. A transformer-type isolator for transmitting power to an element of a substrate support used in a plasma chamber, comprising: It is primary, a primary base plate configured to be electrically coupled to ground; a primary ferrite disposed above the primary base plate and having a primary circular channel; a primary coil wound within the primary circular channel; a primary shield disposed over the primary ferrite and the primary coil, the primary shield including a first plurality of radial segments extending from a primary central region to an outer periphery of the primary ferrite, and a first curved portion for connecting the primary shield to the primary base plate, the first curved portion having a curved shape without any sharp corners or edges; and a first order including It is secondary, a secondary base plate configured to electrically couple to a radio frequency (RF) ground return of the plasma chamber; a secondary ferrite disposed above the secondary base plate and having a secondary circular channel; a secondary coil wound within the secondary circular channel of the secondary ferrite; a secondary shield disposed over the secondary ferrite and the secondary coil, the secondary shield including a second plurality of radial segments extending from a secondary central region to an outer periphery of the secondary ferrite and a second curved portion for connecting the secondary shield to the secondary base plate, the second curved portion having a curved shape without any sharp corners or edges; and a secondary including Equipped with 1. A transformer-type isolator, wherein the primary shield is oriented to face the secondary shield and spaced apart from the secondary shield.

2. 2. The transformer-type isolator according to claim 1, each of the first plurality of radial segments having a first plurality of conductive patterns defining a first plurality of radial slits extending from the primary central region to outside the periphery of the primary ferrite; the second plurality of radial segments having a second plurality of conductive patterns defining a second plurality of radial slits extending from the secondary central region to outside the periphery of the secondary ferrite.

3. 3. The transformer-type isolator according to claim 2, a transformer-type isolator, wherein each of the first plurality of radial segments of the primary shield and the second plurality of radial segments of the secondary shield is formed from a dielectric substrate, the dielectric substrate having the first and second plurality of conductive patterns thereon such that the first plurality of conductive patterns on the primary shield face the second plurality of conductive patterns on the secondary shield.

4. 4. The transformer-type isolator according to claim 3, a transformer-type isolator, wherein the dielectric substrate of each of the primary shield and the secondary shield includes the first and second curved portions that extend outside the periphery.

5. 2. The transformer-type isolator according to claim 1, The primary shield and the secondary shield include corresponding center segments.

6. 6. The transformer-type isolator according to claim 5, A transformer-type isolator, wherein each central segment is defined from a dielectric substrate having a conductive pattern.

7. 6. The transformer-type isolator according to claim 5, a transformer-type isolator, wherein the first and second plurality of radial segments of the primary and secondary shields extend to the respective central segment, and a portion of the first and second plurality of radial segments is connected to the respective central segment.

8. 8. The transformer-type isolator according to claim 7, Each central segment includes a plurality of portions; A transformer-type isolator, wherein each portion is electrically connected to only one of the first plurality of radial segments or one of the second plurality of radial segments.

9. 2. The transformer-type isolator according to claim 1, the first plurality of radial segments includes a first plurality of radial slits, and the second plurality of radial segments includes a second plurality of radial slits; A transformer-type isolator, wherein the first and second plurality of radial slits are configured to reduce current penetration toward the primary and simultaneously increase magnetic field penetration toward the secondary, the current being a current returning from plasma in the plasma chamber to ground, and the magnetic field being used to transfer power to the element.

10. 2. The transformer-type isolator according to claim 1, the first plurality of radial segments includes a first plurality of radial slits, and the second plurality of radial segments includes a second plurality of radial slits; A transformer-type isolator configured such that the first and second plurality of radial slits help reduce swirling eddy currents in the first and second plurality of radial segments, allowing current generated from plasma in the plasma chamber to flow to the ground and to the RF ground return.

11. The transformer-type isolator according to claim 1, a transformer-type isolator, wherein each of the first and second curved portions includes an upper curve and a lower curve, the upper curve transitioning from a flat region to a side region, and the lower curve transitioning from the side region to a connection to the ground or RF ground return.

12. 2. The transformer-type isolator according to claim 1, the first plurality of radial segments includes a first plurality of radial slits, and the second plurality of radial segments includes a second plurality of radial slits; a transformer-type isolator, wherein the first and second plurality of radial slits are configured to reduce swirling of eddy currents in the first plurality of radial segments and the second plurality of radial segments, and an outer diameter region of the primary shield includes a larger area with radial slits than an inner diameter region of the primary shield.

13. 2. The transformer-type isolator according to claim 1, the primary and secondary shields are formed from a dielectric substrate and include a plurality of conductive patterns disposed on the dielectric substrate; A transformer-type isolator, wherein the thickness of the plurality of conductive patterns is within an approximate range of depths from the surfaces of the primary and secondary shields depending on the target operating frequency of the plasma chamber and the type of material of the plurality of conductive patterns.

14. 2. The transformer-type isolator according to claim 1, A transformer-type isolator, wherein the element is a heater.

15. 2. The transformer-type isolator according to claim 1, A transformer-type isolator, wherein the primary coil is interconnected to an AC power source and the secondary coil is interconnected to the element, and the transformer-type isolator helps reduce capacitive coupling between the primary and secondary of RF return current returning to the AC power source while effectively transferring power to the element through increased magnetic field penetration.

16. 2. The transformer-type isolator according to claim 1, A transformer-type isolator, wherein the primary and secondary shields are formed from a dielectric substrate and include a plurality of conductive patterns arranged on the dielectric substrate, the material type of the plurality of conductive patterns is one of copper, silver, or aluminum, the target operating frequency of the plasma chamber is between approximately 400 kHz and approximately 100 MHz, and the thickness of the plurality of conductive patterns is set based on the depth from the surface of the primary and secondary shields related to the material type and the target operating frequency.

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