Patent Publication Number: US-2021166940-A1

Title: Substrate processing apparatus having electrostatic chuck and substrate processing method

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of and priority to U.S. Provisional Application No. 62/942,660, filed on Dec. 2, 2019 in the United States Patent and Trademark Office, the disclosure of which is incorporated herein in its entirety by reference. 
    
    
     TECHNICAL FIELD 
     Examples are described which relate to a substrate processing apparatus and a substrate processing method. 
     BACKGROUND 
     U.S. Pat. No. 9,881,788 B discloses a method and an apparatus for depositing a stress compensation layer and a sacrifice layer on one of a front surface and a back surface of a substrate. Specifically, back side deposition is performed in a state where a front surface of a wafer is oriented upward. Such deposition of a layer on the front surface or the back surface can be executed to reduce stress to be introduced by deposition of a wafer on the front surface. The back side deposition may be executed to minimize a problem relating to back side particles generated during post-processing of deposition such as photolithography. Improvement of such a technique has been desired. 
     SUMMARY 
     Some examples described herein may address the above-described problems. Some examples described herein may provide a substrate processing apparatus and a substrate processing method which enable plasma processing to be performed on a lower surface of a substrate. 
     In some examples, a substrate processing apparatus includes a chamber, an upper cover provided inside the chamber, an electrostatic chuck which includes an annular portion of a dielectric body and an embedded electrode embedded into the annular portion, the electrostatic chuck being provided inside the chamber, and a plasma unit configured to generate plasma in a region below the upper cover and the electrostatic chuck, wherein the annular portion includes an annular first upper surface located immediately below the upper cover, and a second upper surface located immediately below the upper cover and surrounding the first upper surface, the second upper surface having a height higher than a height of the first upper surface. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a sectional view illustrating a configuration example of a substrate processing apparatus; 
         FIG. 2  is a plan view of an electrostatic chuck; 
         FIG. 3  is a sectional view illustrating that a rotating arm is rotated; 
         FIG. 4  is a plan view illustrating a configuration example of the rotating arm; 
         FIG. 5  is a plan view of the rotating arm and the electrostatic chuck; 
         FIG. 6  is a sectional view illustrating introduction of a substrate; 
         FIG. 7  is a sectional view illustrating contact between the substrate and the electrostatic chuck; 
         FIG. 8  is a plan view of the substrate supported by the electrostatic chuck; 
         FIG. 9  is a sectional view illustrating an example of plasma processing; 
         FIG. 10A  is a sectional view illustrating a configuration example of a substrate processing apparatus according to another example; 
         FIG. 10B  is an enlarged view of a portion in  FIG. 10A ; 
         FIG. 11  is a sectional view illustrating a configuration example of a substrate processing apparatus including a microwave plasma generating apparatus; 
         FIG. 12  is a sectional view illustrating a configuration example of a substrate processing apparatus including an inductively coupled plasma apparatus; and 
         FIG. 13  is a sectional view illustrating another configuration example of the substrate processing apparatus including the inductively coupled plasma apparatus. 
     
    
    
     DETAILED DESCRIPTION 
     A substrate processing apparatus and a substrate processing method will be described with reference to the drawings. There is a case where the same reference numerals are assigned to the same or corresponding components, and repetition of description is omitted. 
       FIG. 1  is a sectional view illustrating a configuration example of a substrate processing apparatus according to an embodiment. This substrate processing apparatus is a parallel plate type plasma processing apparatus. A door  12  is attached to a chamber  10  so as to be able to provide a substrate to inside of the chamber  10  or take out a substrate from the chamber  10 . The chamber  10  can be provided as part of a Dual Chamber Module (DCM) or part of a Quad Chamber Module (QCM). An upper cover  14  is provided inside the chamber  10 . According to an example, the upper cover  14  is provided as a ground electrode. The ground electrode is an electrode for grounding. 
     The upper cover  14  includes a shaft portion  14   a  and a disk portion  14   b  connected to the shaft portion  14   a . The shaft portion  14   a  is fixed at a first lifting mechanism  16  which can move in a z positive-negative direction, and can move in the z positive-negative direction. According to an example, the first lifting mechanism  16  is provided by a plate  16   a  fixed at the shaft portion  14   a  being fixed at an upper end of a bellows  16   b , and a plate  16   c  fixed at the chamber  10  being fixed at a lower end of the bellows  16   b . As the first lifting mechanism  16 , various configurations which move the upper cover  14  up and down inside the chamber  10  can be employed. 
     The disk portion  14   b  has a circular shape or a substantially circular shape in planar view. A lower surface of the disk portion  14   b  which is a lower surface of the upper cover  14  has, for example, a first lower surface  14   c , and a second lower surface  14   d  which surrounds the first lower surface  14   c  and which is located below the first lower surface  14   c . Therefore, the lower surface of the disk portion  14   b  has a shape having a dent at the center. 
     The upper cover  14  which is a ground electrode, functions as an upper electrode having a parallel plate structure. To enable plasma coupling and prevent or reduce electric discharge, a difference in height between the first lower surface  14   c  and the second lower surface  14   d  can be made, for example, equal to or less than 1 mm. 
     An electrostatic chuck  20  is provided inside the chamber  10 . The electrostatic chuck  20  includes a support body  20   a , an annular portion  20   b  connected to a lower end of the support body  20   a , and an embedded electrode  20   c  embedded into the support body  20   a  and the annular portion  20   b . The support body  20   a  is fixed at a second lifting mechanism  22 . The second lifting mechanism  22  is configured to move the electrostatic chuck  20  up and down inside the chamber  10 . According to an example, the second lifting mechanism  22  is provided by a plate  22   a  fixed at the support body  20   a  being fixed at the upper end of the bellows  22   b , and a plate  22   c  fixed at the chamber  10  being fixed at the lower end of the bellows  22   b . As the second lifting mechanism  22 , various configurations which move the electrostatic chuck  20  up and down inside the chamber  10  can be employed. 
     The support body  20   a  and the annular portion  20   b  can be formed with, for example, a dielectric body. The annular portion  20   b  has an annular shape in planar view. The annular portion  20   b  includes an annular first upper surface  20   d  located immediately below the upper cover  14  and a second upper surface  20   e  which is located immediately below the upper cover  14  and which surrounds the first upper surface  20   d . A height of the second upper surface  20   e  is higher than a height of the first upper surface  20   d . A difference in height between the first upper surface  20   d  and the second upper surface  20   e  is, for example, greater than a thickness of the substrate to be processed. 
       FIG. 2  is a plan view of the electrostatic chuck  20 . The annular portion  20   b  is formed in a circular shape or a substantially circular shape. The first upper surface  20   d  provides an annular surface, and the second upper surface  20   e  provides an annular surface surrounding the first upper surface  20   d . A dashed line in  FIG. 2  indicates the embedded electrode  20   c . The embedded electrode  20   c  is embedded into the support body  20   a  and the annular portion  20   b . When a positive or negative voltage is applied to the embedded electrode  20   c  from an external power supply, dielectric polarization occurs at the annular portion  20   b  which is a dielectric body. 
       FIG. 1  illustrates that the embedded electrode  20   c  is located immediately below the first upper surface  20   d . Therefore, when a voltage is applied to the embedded electrode  20   c , the first upper surface  20   d  and its vicinity dielectrically polarize. When a substrate which easily polarizes, such as a silicon substrate, is put on the first upper surface  20   d  while charged in this manner, attractive force is generated due to clone force at the annular portion  20   b  and the substrate, so that the substrate can be retained by the annular portion  20   b . Because the substrate is retained by the annular portion  20   b , it is not necessary to cause the support body  20   a  to dielectrically polarize. Therefore, for example, it is possible to provide a ceramic tube as the support body  20   a  and pass the embedded electrode  20   c  through the ceramic tube. 
       FIG. 1  illustrates a rotating arm  30  located in the vicinity of an inner wall of the chamber  10 . The rotating arm  30  is provided to transfer the substrate to inside of four chambers which constitute, for example, the QCM. 
     The substrate processing apparatus includes a plasma unit which is configured to generate plasma in a region below the upper cover  14  and the electrostatic chuck  20 . According to an example, it is sufficient when plasma can be provided immediately below a region surrounded by the annular portion  20   b . In the example in  FIG. 1 , the plasma unit includes a shower plate  34 , gas sources  41  and  42  and an RF power supply  43 . The shower plate  34  is provided below the upper cover  14  so as to face the upper cover  14 . The shower plate  34  includes plates  36  and  40  which have slits for providing gas in a z positive direction from the gas sources  41  and  42 , and a spacer  38  provided between the plates. The whole of the shower plate  34  can be formed with a metal. According to another example, at least the plate  40  is formed with a metal. The gas sources  41  and  42  provide gas necessary for plasma processing. The RF power supply  43  provides high-frequency power for putting gas into a plasma state, to the shower plate  34 . 
     In this manner, the substrate processing apparatus can perform plasma processing with a parallel plate structure including the upper cover  14  and the shower plate  34 . 
     An example of a substrate processing method using this substrate processing apparatus will be described.  FIG. 3  is a sectional view of the substrate processing apparatus immediately before the substrate is transferred to inside of the chamber. As illustrated in  FIG. 3 , the upper cover  14  is evacuated upward by, for example, a motor  50  moving the first lifting mechanism  16 . Further, the electrostatic chuck  20  is evacuated upward by, for example, a motor  52  moving the second lifting mechanism  22 . 
     Thereafter, a support pin which is part of the rotating arm is provided to a substrate receiving position inside the chamber  10  by the rotating arm  30  rotating.  FIG. 4  is a plan view illustrating a configuration example of the rotating arm  30 . In this example, a QCM having four chambers is provided. Support pins  30   a ,  30   b  and  30   c  for supporting the substrate are provided to one of the four chambers  10  by the rotating arm  30  rotating. 
       FIG. 5  is a plan view of the support pins  30   a ,  30   b  and  30   c  and the electrostatic chuck  20 . The support pins  30   a ,  30   b  and  30   c  are disposed at positions surrounded by the annular portion  20   b , of the electrostatic chuck  20 . 
     Then, after the electrostatic chuck  20  is moved downward, and the annular portion  20   b  is located below upper ends of the support pins  30   a ,  30   b  and  30   c , the substrate is put on the support pins  30   a ,  30   b  and  30   c  provided immediately below the upper cover  14 .  FIG. 6  is a view illustrating that the substrate  54  is put on the support pins  30   a ,  30   b  and  30   c . For example, an external arm which supports the substrate  54  provides the substrate  54  on the support pins  30   a ,  30   b  and  30   c  through the door  12 . The substrate  54  includes an upper surface  54   a  and a lower surface  54   b . The substrate  54  is, for example, a wafer formed with silicon or a wide bandgap semiconductor. 
     Then, the annular first upper surface  20   d  is brought into contact with an outer edge portion of a lower surface of the substrate  54  by the annular portion  20   b  being moved upward.  FIG. 7  is a view illustrating a state where the first upper surface  20   d  comes into contact with the outer edge portion of the lower surface  54   b  of the substrate  54 . In the process of the annular portion  20   b  moving to a position above upper ends of the support pins  30   a ,  30   b  and  30   c , the support pins  30   a ,  30   b  and  30   c  are separated from the substrate  54 , and a central portion of the lower surface of the substrate  54  is exposed as the first upper surface  20   d  supports the outer edge portion of the lower surface of the substrate  54 . Thereafter, the support pins are evacuated from positions immediately below the upper cover  14  by the rotating arm  30  rotating. 
       FIG. 8  is a plan view of the electrostatic chuck  20  and the substrate  54  in  FIG. 7 . In  FIG. 8 , as a result of the substrate  54  contacting the first upper surface  20   d , the whole or the most portion of the first upper surface  20   d  cannot be viewed in planar view, and the second upper surface  20   e  appears. An inner edge of the first upper surface  20   d  is indicated with a dashed line. 
     Then, the second upper surface  20   e  is brought into close contact with the upper cover  14  while contact between the upper cover  14  and the substrate  54  is avoided.  FIG. 9  illustrates that the second upper surface  20   e  of the electrostatic chuck  20  is brought into close contact with the second lower surface  14   d  of the upper cover  14 . In this example, the second upper surface  20   e  is brought into close contact with the second lower surface  14   d  by the upper cover  14  being moved downward. According to an example, it is possible to prevent contact between the upper cover  14  and the substrate  54  by providing the first lower surface  14   c  located above the second lower surface  14   d  at the upper cover  14 . 
     The second upper surface  20   e  is located immediately below the second lower surface  14   d , and, when the second lower surface  14   d  comes into contact with the second upper surface  20   e , flow of gas through space between the upper cover  14  and the electrostatic chuck  20  is inhibited. In another example, in a case where a lower surface of the disk portion  14   b  of the upper cover  14  is made flat, as a result of the lower surface of the upper cover contacting the second upper surface  20   e , flow of gas through space between the lower surface of the upper cover and the second upper surface  20   e  is inhibited. Further, the whole of the outer edge portion of the lower surface  54   b  of the substrate  54  is attracted to the first upper surface  20   d  by the electrostatic chuck  20 . 
     According to an example, in a state illustrated in  FIG. 9 , space surrounded by the substrate  54 , the electrostatic chuck  20  and the upper cover  14  becomes enclosed space. In this case, gas supplied from the gas sources  41  and  42  and plasma provided between parallel plates are not virtually provided to the enclosed space. 
     Then, plasma processing is performed on the lower surface  54   b  of the substrate  54 . Specifically, in a state where the substrate  54  is attracted to the first upper surface  20   d  by the electrostatic chuck  20 , plasma processing is performed on the central portion of the lower surface of the substrate  54  using the above-mentioned plasma unit. According to an example, significant plasma processing on the upper surface  54   a  of the substrate  54  is prevented by making space surrounded by the substrate  54 , the electrostatic chuck  20  and the upper cover  14  enclosed space during the plasma processing. 
     It can be said that a side of the upper surface  54   a  of the substrate  54  is a device surface on which a device is formed. In this case, it is possible to protect the device by avoiding contact between the substrate  54  and the upper cover  14 . It is possible to ensure this avoidance of contact by providing a concave portion illustrated in  FIG. 1  on the lower surface of the upper cover  14 . 
     As the plasma processing, it is possible to employ film formation, reformulation of a film formed on the substrate or etching. According to an example, in the plasma processing, an oxide film or a nitride film is formed at the central portion of the lower surface  54   b  of the substrate  54 . In this plasma processing, it is possible to form a film on the lower surface  54   b  of the substrate  54  while suppressing film formation on the upper surface  54   a  of the substrate  54 . According to an example, the film formed at the central portion of the lower surface  54   b  of the substrate  54  through the plasma processing alleviates warpage of the substrate  54 . 
     In this manner, by causing the upper cover  14  to face the upper surface  54   a  of the substrate  54  while the electrostatic chuck  20  holds the outer edge portion of the lower surface  54   b  of the substrate  54 , space above the upper surface  54   a  of the substrate  54  is made enclosed space covered with the upper cover  14 . It is possible to perform plasma processing on the central portion of the lower surface of the substrate  54  in a state where the substrate  54  is electrostatically attracted by the electrostatic chuck  20 . Note that whether or not the substrate  54  is retained by the electrostatic chuck  20  can be switched at an arbitrary timing. 
       FIG. 10A  is a sectional view of a substrate processing apparatus according to another example.  FIG. 10A  shows a cross-sectional view of a simplified version of an apparatus  400  capable of depositing on the back side of a wafer  451  (wafer  451  is shown as a black horizontal line in  FIG. 10A ).  FIG. 10B  shows a close up view of a portion of the apparatus  400 . In particular,  FIG. 10B  illustrates how the wafer  451  is supported in the apparatus  400 . The wafer  451  is supported at or near its periphery by a wafer support ring  453 . The support ring  453  may contact the wafer  451  on the wafer&#39;s bottom surface, near the wafer edge in a region referred to as the support contact region. The support contact region is annularly shaped, and may be very small such that substantially the entire back side of the wafer (e.g., at least about 95%, or at least about 99%, as measured by surface area) is exposed during deposition. In some embodiments, the support contact region on the bottom of a wafer extends from the edge of the wafer inwards by about 5 mm or less, for example by about 1 mm or less. In the example of  FIG. 10B , the support contact region is on the bottom of wafer  451 , extending inwards from the periphery of the wafer by distance  461 . The support ring  453  may also contact the top side of a wafer near the wafer edge. In these cases, the support contact region extends to the top side of the wafer. In this embodiment, the support ring may have a local cross-section that is C-shaped (rather than L-shaped as shown in  FIG. 10B ), extending both under and over a portion of the wafer at its periphery. Where the support ring contacts the top side of a wafer, care should be taken to ensure that the support ring does not damage the front side of the wafer. Such care may include ensuring that the support ring only contacts the wafer front side in a small defined area (the support contact area), and not in an active area. In some embodiments, the support contact area on the top of the wafer extends radially inward from the edge of the wafer by no more than about 0.5 mm, or by no more than about 0.25 mm. 
     In some embodiments, the support ring may be replaced with another wafer support mechanism that supports the wafer at/near its periphery. One example is a series of three or more disconnected pegs that support the wafer at different locations around its edge. In some cases the pegs may wrap around the wafer to better secure it in place during processing. The pegs (or other support mechanisms) may contact the wafer within the support contact regions described above. 
     In any case, the mechanism for holding the substrate may be designed such that the front side of the wafer does not substantially contact any portion of the reactor. As used herein, this means that any contact between the front side of the wafer  451  and the wafer support mechanism  453  (e.g., support ring, pegs, etc.) or other portion of the apparatus happens only near the edge of the wafer. The front side of the wafer includes an active region, where devices are fabricated, surrounded by a non-active peripheral region. The non-active peripheral region is present due to the geometry of the wafer and the need to handle the wafer during processing. By ensuring that the active region on the front side of the wafer does not contact any portion of the reactor, damage to the front side of the wafer may be minimized or avoided altogether. Contact that occurs at the very edge of the front side is not problematic in many cases, because the peripheral non-active region is typically removed and discarded when the substrate is cut into individual devices. As such, contact that happens in this region is not fatal to the final devices formed on the wafer. 
     Returning to the embodiment of  FIGS. 10A and 10B , the support ring  453  holds the wafer  451  over the deposition region  459 . The deposition region  459  is the area where reactant gases are introduced, reacted, and deposited on the wafer  451 . The deposition region  459  is at least about coextensive with the area of the wafer  451 . The bottom of the deposition region  459  may be defined by a lower surface  463 , which in this embodiment also acts as a showerhead  463 . The lower surface  463  is typically substantially parallel to the wafer  451 . The height of the deposition region  459  (measured as the distance between the bottom side of the wafer  451  and the lower surface) may be relatively small in many cases. For example, the deposition region  459  may have a height between about 5-30 mm, for example between about 15-25 mm. In some embodiments, at least one of the lower electrode/showerhead surface  463  and support ring  453  is movable such that the height of the deposition region  459  may be tuned. 
     As mentioned, the lower surface  463  defines the bottom of the deposition region  459 . In various implementations, the bottom surface  463  is powered (e.g., with an RF power source). In some embodiments, the lower surface  463  is adapted to act as a showerhead to provide process gases as needed. In other embodiments, the lower surface  463  may be simpler, and process gases may be provided through alternate inlets. Various different types of plasma may be used. For instance, the plasma may be generated directly in the deposition region  459  (i.e., a direct plasma) or may be generated at a different location and piped into the deposition region (i.e., a remote plasma). Any appropriate plasma generator may be used. In various embodiments the plasma is a capacitively coupled plasma generated between a powered lower electrode/showerhead  463  below the wafer  451  and a grounded upper electrode/top surface  455  above the wafer. 
     Above the wafer  451  is a small front side gap  457 . This gap  457  extends between the top surface of the wafer  451  and an upper surface  455  in the reaction chamber. The size of the gap in  FIG. 10A  is exaggerated for the purpose of illustration. The upper surface  455  may be a heater, a ground plate, a chamber ceiling, or another type of plate/surface. In many cases this upper surface  455  acts as an electrode. In some embodiments, the height of the front side gap  457  is about 0.5 mm or smaller, for example about 0.35 mm or smaller. In these or other embodiments, the height of the front side gap  457  may be at least about 0.1 mm or bigger, for example at least about 0.25 mm or bigger. In many cases this upper surface  455  is substantially parallel to the wafer. This upper surface/electrode  455  may also extend around the edge of the substrate as shown in  FIG. 10B  such that it comes into contact with the wafer support ring  453 . During deposition, inert gas (e.g., N2, Ar, etc.) is introduced from a front side inlet  465  and passes over the front side of the wafer  451 . The front side inlet  465  may be positioned at or near the center of the wafer  451 , such that the inert gas flows from the center of the wafer outward. This outward flowing inert gas helps ensure that no deposition-causing gases enter the front side gap  457  or come into contact with the front side of the wafer  451 . In other words, the inert gas flow helps ensure that no material is able to deposit on the front side of the wafer  451  during back side deposition. To further protect the front side of the wafer  451 , the front side gap  457  may be designed such that it is smaller than the thickness of the plasma sheath. This helps ensure that the plasma does not enter the front side gap where it could damage the substrate. 
     In many cases, the plasma is a capacitively coupled plasma that is generated between an upper electrode and a lower electrode. In certain cases the upper electrode may be connected with ground, and the lower electrode may connected with an RF source. The lower electrode may operate in part to collect electrons from the plasma. Dual RF (e.g., using and controlling both LF and HF frequencies and powers) may be used to modulate the stress of a deposited film in various cases. 
     In some embodiments, the back side deposition reactor is a bevel cleaning apparatus that has been modified to perform back side deposition. One example of a processing apparatus that may be modified is the Coronus® plasma bevel clean apparatus from Lam Research of Fremont, Calif. This apparatus is further discussed in the following U.S. patents, each of which is incorporated by reference in its entirety: U.S. Pat. No. 7,858,898, filed Jan. 26, 2007, and titled “BEVEL ETCHER WITH GAP CONTROL”; U.S. Pat. No. 7,943,007, filed Jan. 26, 2007, and titled “CONFIGURABLE BEVEL ETCHER”; and U.S. Pat. No. 8,562,750, filed Dec. 17, 2009, and titled “METHOD AND APPARATUS FOR PROCESSING BEVEL EDGE.” 
     Modifications useful for performing back side deposition typically include installation of a different wafer holder (e.g., an annular wafer holder that supports the wafer at its periphery and allows the back side of the wafer to remain exposed to plasma during processing), and installation of (or modification to) a different gas delivery system (e.g., to deliver deposition gases to the deposition region under the back side of the wafer, while also delivering inert gas to the front side gap above the front side of the wafer). Further, a heater and/or ground plate may be added above the wafer, if not already present. 
     As shown in  FIGS. 10A and 10B , embedded electrode  453   a  is embedded in the wafer support ring  453  so that the wafer support ring  453  can function as an electrostatic chuck as explained above. In some examples, the embedded electrode  453   a  may be placed right below the wafer  451  to ensure electrostatic chuck function. In other words, the embedded electrode  453   a  extends to the position right below the distance  461 . 
       FIG. 11  is a sectional view of a substrate processing apparatus according to another example. In this example, as the plasma unit, a microwave plasma generating apparatus is provided. A plurality of rods  64  are provided inside the chamber  10 . The rods  64  include a conductor  60  and a dielectric body  62  surrounding the conductor  60 . A microwave is provided to inside of this dielectric body  62  from a coaxial waveguide. That is, the microwave fed from a microwave feeding portion of the coaxial waveguide ultimately reaches the plurality of rods  64 . Then, microwave energy generates an electric field outside the dielectric body  62  of the rods  64 , thereby plasma  70  is generated. In this manner, at the microwave plasma generating apparatus, plasma is generated at the plurality of rods  64 . The substrate  54  can be electrostatically attracted to the first upper surface  20   d  by the electrostatic chuck  20 . 
     In a case where the microwave plasma generating apparatus is used, the upper cover  14  is not used as a parallel plate, and functions as a cover of the substrate  54 . Therefore, it is possible to increase a difference in height between the first lower surface  14   c  and the second lower surface  14   d  to avoid contact between the substrate  54  and the upper cover  14 . In other words, it is possible to provide a deep concave portion at the central portion of the lower surface of the upper cover  14 . Further, while, in a case of a parallel plate, a distance from the substrate to the upper cover varies due to variation of warpage of the substrate  54 , which can vary plasma density, such a problem does not occur by using the microwave plasma generating apparatus. 
       FIG. 12  is a sectional view of a substrate processing apparatus according to another example. In this example, as the plasma unit, an inductively coupled plasma apparatus is provided. The ICP reactor  120  can process substrates with high density plasma. Suitable ICP reactors include TCP™ systems from LAM Research Corp., Fremont, Calif. See also Ogle, U.S. Pat. No. 4,948,458 which is incorporated herein. The reactor includes a process chamber  121  in which plasma  122  is generated adjacent substrate  123 . Upper cover  124  is provided above the substrate  123 . 
     Temperature control of the substrate  124  is achieved by supplying helium gas through conduit  125  to a space between the substrate and the upper cover  124 . The upper cover  124  can comprise an anodized aluminum electrode, which may be heated, or a ceramic material having a buried electrode therein, the upper cover  124  being powered by an RF source  126  and associated circuitry  127  for providing RF matching, etc. The temperature of the substrate  123  during processing thereof is monitored by temperature monitoring equipment  128  attached to temperature probe  129 . 
     In order to provide a vacuum in chamber  121 , a turbo pump is connected to outlet port and a pressure control valve can be used to maintain the desired vacuum pressure. Process gases can be supplied into the chamber  121  by conduits  131 ,  132  which feed the reactant gases to gas distribution rings extending around the dielectric window  133  or the process gases can be supplied through a dielectric showerhead window. 
     An external ICP coil  134  located outside the chamber in the vicinity of the window is supplied with RF power by RF source  135  and associated circuitry  136  for impedance matching, etc. 
     As is apparent, the external induction coil  134  is substantially planar and generally comprises a single conductive element formed into a planar spiral or a series of concentric rings. The planar configuration allows the coil to be readily scaled-up by employing a longer conductive element to increase the coil diameter and therefore accommodate larger substrates or multiple coil arrangements could be used to generate a uniform plasma over a wide area. When a substrate is processed in the chamber, the RF source  135  supplies the coil  134  with RF current preferably at a range of about 100 kHz-27 MHz, and more preferably at 13.56 MHz and the RF source  126  supplies the cover  124  with RF current preferably at a range of about 100 kHz-27 MHz, and more preferably at 400 kHz, 4 MHz or 13.56 MHz. A large DC sheath voltage below the surface of a substrate can be provided by supplying RF power to the electrode. 
     RF bias is applied to the substrate to generate ion bombardment of the growing film during the gap filling step. The RF frequency can be anything above the value necessary to sustain a steady state sheath, which is a few hundred kHz. Substrate bias has numerous beneficial effects on film properties, and can also be used to simultaneously sputter the growing film in the gap-fill step. This allows narrow, high aspect ratio gaps to be rapidly filled with high quality dielectric. RF bias can be used during the cap layer deposition step. 
     ICP Reactor  120  can be used to carry out the gap filling process of the invention wherein a heavy noble gas is used to increase the etch-to-deposition rate ratio (EDR) for void-free filling of sub 0.5 . mu.m high aspect ratio gaps. Gap filling processes are further described in copending application Ser. No. 08/623,825 filed on Mar. 29, 1996 entitled “IMPROVED METHOD OF HIGH DENSITY PLASMA CVD GAP-FILLING,” which application is incorporated herein. 
     At the substrate processing apparatus in  FIG. 12 , the above-mentioned electrostatic chuck  20  is provided. The electrostatic chuck  20  is provided to electrostatically attract an outer edge portion of a lower surface of the substrate  123 . The substrate  123  is held by the electrostatic chuck  20 , and plasma processing such as, for example, film formation, is performed on the lower surface of the substrate  123 . 
       FIG. 13  is a sectional view of a substrate processing apparatus according to another example. While the apparatus in  FIG. 13  is similar to the apparatus in  FIG. 12 , the apparatus in  FIG. 13  is different from the apparatus in  FIG. 12  in a configuration where the upper cover  124  comes into contact with the second upper surface  20   e . Providing enclosed space by the substrate  123 , the electrostatic chuck  20  and the upper cover  124  on a side of the upper surface of the substrate  123  contributes to suppression of plasma processing on the upper surface of the substrate  123 .