Large-diameter porous plug for argon conveying and two-stage flexible clamping method

Abstract

The present disclosure relates to a substrate support assembly for reducing evacuation time when using argon. In one embodiment, a substrate support assembly includes a porous plug within the substrate support assembly. The porous plug includes a first cylindrical section having a first volume and an axial length, a second cylindrical section having a second volume and an axial length. The first cylindrical section has a larger volume than the second cylindrical section. The first cylindrical section and the second cylindrical section have a volume ratio of between about 2 and about 12. The first cylindrical section axial length and the second cylindrical section axial length have a length ratio of between about 2 and about 10.

Description

[0001] Cross-references to related applications

[0002] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 412,271, filed on September 30, 2022, the entire contents of which are incorporated herein by reference. background Technical Field

[0004] Embodiments of the present invention generally relate to semiconductor processing and manufacturing. In semiconductor processing, plasma processes are often performed in a vacuum by evacuating gas from a processing chamber. In such processes, a substrate is placed on an electrostatic chuck (ESC) disposed on a workbench in the processing chamber. The electrostatic chuck includes a conductive sheet-type clamping electrode disposed between dielectric members (e.g., dielectric layers).

[0005] Prior Art

[0006] Helium is a commonly used backside gas in semiconductor processing. However, helium is expensive and increases the cost of processing substrates when this gas is used. In addition, when the clamping voltage of the electrostatic chuck is increased, the combined force can cause additional vacuum leaks when helium is used due to its small atomic size. Therefore, the processing chamber may experience pressure and vacuum instabilities when helium is used as a backside gas.

[0007] Therefore, there is a need for apparatus and methods for improving backside gas processing during semiconductor processing operations.

[0008] In semiconductor processing, plasma processes are often performed in a vacuum by evacuating the gas from the processing chamber. In such processes, the substrate is placed on an electrostatic chuck (ESC) disposed on a workbench in the processing chamber. The electrostatic chuck includes a conductive sheet-type clamping electrode disposed between dielectric members (e.g., dielectric layers).

[0009] When a plasma process is performed, a voltage from a DC voltage source is applied from the voltage source to the clamping electrode so that the substrate is "clamped" to the surface of the electrostatic chuck by the Coulomb or Johnson-Rahbek force generated from the voltage application. After the plasma process is completed, the voltage applied to the clamping electrode of the electrostatic chuck is typically turned off or set to a low value to compensate for any residual charge left on the wafer so that the substrate can be unclamped from the electrostatic chuck.

[0010] In some cases, to de-chuck the substrate, a discharge process is performed, which involves introducing an inert gas into the process chamber to maintain the pressure within the process chamber at a predetermined pressure level; applying a voltage of opposite polarity relative to the voltage applied to the electrostatic chuck during the plasma process, and then turning off or setting it to a low value to compensate for any residual charge left on the wafer during the voltage application, so that the charge of the electrostatic chuck and the substrate can be discharged. Then, the support pins are raised so that the substrate can be lifted and de-chucked from the electrostatic chuck.

[0011] During the process of "chucking" the substrate, when a high voltage is applied to the chucking electrodes to clamp the substrate to the ESC, the forces generated on the substrate due to the sudden application of voltage can be quite high. In addition, when the temperature of the substrate equilibrates to match the surface temperature of the electrostatic chuck, the coefficient of thermal expansion (CTE) mismatch between the surfaces of the substrate and the electrostatic chuck causes relative motion between the back side of the substrate and the surface of the electrostatic chuck. The relative motion between the two components in turn causes a relative sliding motion, which in turn has been found to generate particles on the back side of the substrate and / or cause scratches and damage to the back side surface of the substrate.

[0012] Therefore, there is a need for improved methods to reduce deleterious effects on a substrate when clamping and unclamping the substrate from an ESC. Summary of the invention

[0013] In one embodiment, a substrate support assembly includes a porous plug within the substrate support assembly. The porous plug includes a first cylindrical segment having a first volume and an axial length, a second cylindrical segment having a second volume and an axial length. The first cylindrical segment has a larger volume than the second cylindrical segment. The first cylindrical segment and the second cylindrical segment have a volume ratio between about 2 and about 12. The first cylindrical segment axial length and the second cylindrical segment axial length have a length ratio between about 2 and about 10.

[0014] In another embodiment, a processing chamber includes one or more walls surrounding a processing volume and a substrate support assembly disposed in the processing volume. The substrate support assembly includes an electrostatic chuck disposed above an insulating plate and a porous plug disposed within the insulating plate. The porous plug includes a material having porosity; a first cylindrical section having a first volume, a first diameter, and a first axial length; and a second cylindrical section having a second volume less than the first volume, a second diameter less than the first diameter, and a second axial length less than the first axial length.

[0015] In another embodiment, the porous plug includes a cross-linked polystyrene material having uniform porosity; a first cylindrical segment having a first volume, a first diameter, and a first axial length; and a second cylindrical segment having a second volume less than the first volume, a second diameter less than the first diameter, and a second axial length less than the first axial length. A volume ratio between the volume of the first cylindrical segment and the volume of the second cylindrical segment is between about 2 and about 12. The first cylindrical segment is disposed between the second cylindrical segment and the treatment volume. A length ratio between the first axial length and the second axial length is between about 2 and about 10.

[0016] In another embodiment, a method of clamping a substrate to a surface of an electrostatic chuck (ESC) is provided. The method includes applying a first voltage to a clamping electrode in the ESC during a clamping time interval; supplying an inert gas at a first pressure to a back side of the substrate during the clamping time interval; applying a second voltage to the clamping electrode after the clamping time interval, the second voltage being higher than the first voltage; and supplying an inert gas at a second pressure to the back side of the substrate after the clamping time interval, the second pressure being higher than the first pressure of the inert gas.

[0017] In another embodiment, a method of unclamping a substrate from a surface of an electrostatic chuck (ESC) is provided. The method includes: reducing a back gas pressure at a lower surface of the substrate; reducing a voltage applied to a clamping electrode in the ESC to a unclamping voltage after reducing the pressure; increasing a substrate temperature for a unclamping interval; reducing the back gas pressure after the unclamping interval and reducing the unclamping voltage.

[0018] In another embodiment, a substrate processing chamber is provided. The chamber includes an electrostatic chuck (ESC) in fluid communication with a cryogenic freezer and a controller. The controller includes a central processing unit (CPU), support circuits, and a non-transitory computer-readable medium. The computer-readable medium includes instructions for clamping a substrate. When executed, the instructions cause a first voltage to be applied to a clamping electrode in the ESC for a first time interval; a first pressure of an inert gas to be applied to the back side of the substrate for a first time interval; after the first time interval, a second voltage is applied to the clamping electrode for a second time interval, the second voltage being higher than the first voltage; and a second pressure of an inert gas is applied to the back side of the substrate for a second time interval, the second amount of the inert gas being lower than the first amount of the inert gas. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to be able to understand the above-mentioned features of the present disclosure in detail, the present disclosure briefly summarized above can be described more particularly with reference to the embodiments, some of which are shown in the accompanying drawings. However, it should be noted that the accompanying drawings only show exemplary embodiments and therefore should not be considered as limiting the scope thereof, and other equally effective embodiments may be allowed.

[0020] Figure 1 A schematic cross-sectional view of a plasma processing chamber according to an embodiment of the present disclosure is shown.

[0021] Figure 2 A schematic cross-sectional view of a substrate support assembly according to an embodiment of the present disclosure is shown.

[0022] Figure 3 A schematic cross-sectional view of a porous plug within a chamber according to an embodiment of the present disclosure is shown.

[0023] Figure 4 A method of clamping a substrate is shown.

[0024] Figure 5 A method of declamping a substrate is shown.

[0025] To facilitate understanding, identical reference numerals have been used, where possible, to designate elements that are shared among the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation. DETAILED DESCRIPTION

[0026] Embodiments described herein provide a substrate support assembly having a porous plug that enables operation of an electrostatic chuck (ESC) using a backside gas that is more economical than helium, such that a substrate disposed on the ESC is maintained at a temperature below -20°C during substrate processing while other surfaces of the processing chamber are maintained at a different temperature.

[0027] Although the substrate support assembly is described below in an etch processing chamber, the substrate support assembly can be used in other types of plasma processing chambers, such as physical vapor deposition chambers, chemical vapor deposition chambers, ion implantation chambers, and other chambers, as well as other systems where processing requires maintaining a substrate at a temperature below -20° C. The substrate support assembly disclosed herein can also be utilized at temperatures below -20° C.

[0028] It has been found that using argon has advantages in many substrate processes, including reduced vacuum leakage when compared to helium. In addition, when utilizing argon as the backside gas, the backside gas rate into the processing region can be controlled at a substantially constant rate. In contrast, as the vacuum pressure increases, helium is observed to leak into the processing region at a higher rate, which results in potentially reduced gas rate control. Because argon is a larger molecule than helium, the argon delivery time is longer than the helium delivery time when the same backside gas delivery apparatus is used.

[0029] Embodiments described herein provide a plug design that enables argon to have similar back gas pump down times as helium while retaining the advantages of less leakage in an isolated vacuum and less back gas leakage at higher pressures.

[0030] Figure 1 A schematic cross-sectional view of an exemplary plasma processing chamber 100 is shown, which is shown configured as an etching chamber, having a substrate support assembly 101. The substrate support assembly 101 can be used in other types of plasma processing chambers, such as plasma processing chambers, annealing chambers, physical vapor deposition chambers, chemical vapor deposition chambers, and ion implantation chambers, among other chambers, and in other systems where the ability to uniformly maintain a surface or workpiece, such as a substrate 124, at a temperature below about -20°C is desirable. Dry reactive ion etching of the substrate 124 can be performed at a variety of temperatures, including temperatures below -20°C or above 300°C, so that the ions can bombard the upward-facing surface of the material disposed on the substrate 124 with reduced spontaneous etching, so that grooves with smooth, vertical sidewalls are formed. One of the many advantages of such techniques includes improved selectivity for etching one material relative to another material at temperatures below -20°C. For example, the selectivity between silicon (Si) and silicon dioxide (SiO2) increases exponentially as the temperature decreases.

[0031] The plasma processing chamber 100 includes a chamber body 102 having sidewalls 104, a bottom 106, and a lid 108 surrounding a processing region 110. An injection device 112 is coupled to the sidewalls 104 and / or the lid 108 of the chamber body 102. A gas panel 114 is coupled to the injection device 112 to enable the delivery of process gases into the processing region 110. The injection device 112 may be one or more nozzles or inlet ports, or alternatively, a showerhead. The process gases, along with any process byproducts, are removed from the processing region 110 through an exhaust port 116 formed in the sidewalls 104 or the bottom 106 of the chamber body 102. The exhaust port 116 is coupled to a pump system 140 that includes a throttle valve and a pump for controlling the vacuum level within the processing region 110.

[0032] The process gas is energized to form a plasma within the process region 110. In one embodiment, the process gas is energized by capacitively or inductively coupling RF power or pulsed DC to the process gas. Figure 1 In this depicted embodiment, which may be combined with other embodiments described herein, a plurality of coils 118 are disposed above a lid 108 of a plasma processing chamber 100 and are coupled to an RF power source 122 through a matching circuit 120 .

[0033] The substrate support assembly 101 is disposed below an implantation device 112 in a processing region 110. The substrate support assembly 101 includes an electrostatic chuck (ESC) 103 and an ESC base 105. The ESC base 105 is coupled to the ESC 103 and a facility plate 107. The facility plate 107 supported by a ground plate 111 is configured to facilitate electrical, cooling, heating, and gas connections to the substrate support assembly 101. The ground plate 111 is supported by a bottom 106 of the processing chamber. An insulator plate 109 insulates the facility plate 107 from the ground plate 111.

[0034] The ESC substrate 105 includes a substrate channel 115 coupled to a cryogenic refrigerator 117. The cryogenic refrigerator 117 is in fluid communication with the substrate channel 115 through a substrate inlet conduit 123 connected to the inlet of the substrate channel 115 and through a substrate outlet conduit 125 connected to the outlet of the substrate channel 115, so that the ESC substrate 105 is maintained at a temperature below -20°C. The cryogenic refrigerator 117 is coupled to an interface box (not shown) to control the flow rate of the base fluid. The base fluid may contain a material capable of maintaining a temperature below -50°C. The cryogenic refrigerator 117 provides a base fluid that circulates through the substrate channel 115 of the ESC substrate 105. The base fluid flowing through the substrate channel 115 enables the ESC substrate 105 to be maintained at a temperature below -20°C, which helps to control the lateral temperature distribution of the ESC 103, so that the substrate 124 disposed on the ESC 103 is uniformly maintained at a temperature below -20°C or above 300°C. In one embodiment that may be combined with other embodiments described herein, the cryogenic freezer 117 is a single stage freezer operable to maintain the base fluid at a temperature below about -50° C. In another embodiment that may be combined with other embodiments described herein, the cryogenic freezer 117 is a freezer that utilizes a refrigerant inside the freezer to maintain the base fluid at a temperature below -50° C.

[0035] The facility plate 107 includes a facility channel 113 coupled to a freezer 119. The freezer 119 is in fluid communication with the facility plate 107 through a facility inlet conduit 129 so that the facility plate 107 is maintained at a predetermined ambient temperature. The cryogenic freezer 117 is coupled to the interface box to control the flow rate of the facility fluid. The facility fluid may include a material that can maintain an ambient temperature between about -10°C and about 60°C. The freezer 119 provides the facility fluid, which circulates through the facility plate 107. The facility fluid enables the facility plate 107 to be maintained at a predetermined ambient temperature, which helps maintain the insulator plate 109 at a predetermined ambient temperature.

[0036] The ESC 103 has a support surface 130 and a bottom surface 132 opposite to the support surface 130. In one embodiment that can be combined with other embodiments described herein, the ESC 103 is made of a ceramic material such as aluminum oxide (Al2O3), aluminum nitride (AlN) or other suitable materials. Alternatively, the ESC 103 can be made of a polymer such as polyimide, polyetheretherketone, polyaryletherketone, etc.

[0037] The ESC 103 includes a clamping electrode 126 disposed therein. The clamping electrode 126 can be configured as a monopolar or bipolar electrode, or other suitable arrangement. The clamping electrode 126 is coupled to a clamping power supply 134 through an RF filter (not shown) and a facility board 107, which provides DC power to electrostatically fasten the substrate 124 to a support surface 130 of the ESC 103. The RF filter prevents the RF power used to form a plasma (not shown) within the plasma processing chamber 100 from damaging electrical equipment or creating electrical hazards outside the chamber.

[0038] The ESC 103 includes one or more resistive heaters 128 embedded therein. If necessary, the resistive heaters 128 are used to raise the temperature of the ESC 103 to a temperature suitable for processing the substrate 124 disposed on the support surface 130. The resistive heaters 128 are coupled to a heater power supply 136 through the facility board 107 and an RF filter (not shown). The RF filter prevents the RF power used to form a plasma (not shown) within the plasma processing chamber 100 from damaging electrical equipment or causing electrical hazards outside the chamber. The heater power supply 136 may include a heater controller (not shown) for controlling the operation of the heater power supply 136, which is generally configured to heat the substrate 124 when necessary so as to maintain the substrate temperature at a desired temperature. In other embodiments, the controller is separate from the heater power supply 136. In other words, the heat from the resistive heaters 128 and the cooling from the base fluid circulating through the ESC base 105 are balanced to maintain the substrate 124 at a desired temperature at or below -20°C. For example, the resistive heater 128 and the base fluid circulated through the ESC substrate 105 maintain the substrate 124 at a temperature suitable for processing below about -20°C, such as between about -20°C and about -150°C.

[0039] The resistive heater 128 includes a plurality of laterally separated heating zones, wherein the heater controller enables at least one zone of the resistive heater 128 to be preferentially heated relative to the resistive heaters 128 positioned in one or more other zones in the other zones. For example, the resistive heaters 128 may be arranged concentrically in a plurality of separate heating zones. The separate heating zones of the resistive heater 128 help control the temperature uniformity of the lateral edge to the center of the substrate 124. The substrate support assembly 101 may also include one or more probes (not shown) disposed therein. The ESC 103 is coupled to a controller 138. The probes disposed in the ESC base 105 are communicatively coupled to the controller 138 and may be utilized together to calibrate the temperature of the substrate based on the temperature of the ESC base 105. The controller 138 is coupled to a heater power supply 136 so that each zone of the resistive heater 128 is independently heated so that the lateral temperature distribution of the ESC 103 is substantially uniform based on the temperature measurement results so that the substrate 124 disposed on the ESC 103 is uniformly maintained at a temperature below -20°C.

[0040] In some embodiments of the present disclosure, an apparatus for clamping and de-clamping a substrate from a surface of an ESC in a processing chamber includes a controller 138. The controller 138 includes a programmable central processing unit (CPU) 138A that is operable with a memory 138B (e.g., non-volatile memory) and support circuits 138C. The CPU 138A of the controller 138 includes one or more processors to execute instructions stored in the memory 138B to implement a method for performing a two-stage soft clamping process. The support circuits 138C are conventionally coupled to the CPU 138A and include caches, clock circuits, input / output subsystems, power supplies, etc. and combinations thereof, which are coupled to various components of the substrate processing chamber 100 to facilitate control thereof. The CPU 138A is a general-purpose computer processor in any form of a general-purpose computer processor used in an industrial environment, such as a programmable logic controller (PLC) for controlling various components and subprocessors of a processing system. The memory 138B coupled to the CPU 138A is a non-transitory computer readable medium and is typically one or more readily available memories such as random access memory (RAM), read only memory (ROM), a floppy disk drive, a hard disk, or any other form of local or remote digital storage device.

[0041] Typically, the memory 138B is in the form of a non-transitory computer-readable storage medium containing instructions (e.g., non-volatile memory) that, when executed by the CPU 138A, facilitates the operation of the chamber 100. The instructions in the memory are in the form of a program product, such as a program that implements the methods of the present disclosure. The program code may conform to any of a variety of different programming languages. In one example, the present disclosure may be implemented as a program product stored on a computer-readable storage medium for use with a computer system. The program of the program product defines the functionality of various embodiments, including the methods described herein.

[0042] Illustrative non-transitory computer-readable storage media include, but are not limited to: (i) non-writable storage media (e.g., read-only memory devices within a computer, such as CD-ROM disks readable by a CD-ROM drive, flash memory, ROM chips, or any type of solid-state non-volatile semiconductor memory device, such as a solid state drive (SSD)), on which information can be permanently stored; and (ii) writable storage media (e.g., a floppy disk in a disk drive or hard disk drive or any type of solid-state random access semiconductor memory), on which variable information can be stored. Such computer-readable storage media, when carrying computer-readable instructions that direct the functions of the methods described herein, are embodiments of the present disclosure. In some embodiments, the methods described herein or portions thereof are performed by one or more application specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other types of hardware implementations. In some other embodiments, the substrate processing and / or treatment methods described herein are performed by a combination of software routines, ASICs, FPGAs, and / or other types of hardware implementations. One or more system controllers 138 may be used with one or any combination of the various modular polishing systems described herein and / or individual polishing modules thereof.

[0043] Figure 2 An illustrative cross section of the substrate support assembly 101 is shown. The substrate support assembly 101 includes the ESC 103, the ESC base 105, the facility plate 107, the insulator plate 109, the ground plate 111, and the edge ring 209.

[0044] The clamping electrodes 126 within the ESC 103 provide a clamping force when a voltage is applied to the clamping electrodes and there is a voltage difference between the substrate 124 and the ESC clamping electrodes 126. In order for the clamping force to exist, the substrate lower surface 203 needs to be in contact with the ESC support surface 130.

[0045] The support surface 130 includes the top surface of the ESC 103 and the tops of a plurality of pillars 207 disposed within the backside gas cavity 205 of the ESC 103. When clamped by the clamping electrode 126, the cavity 205 can be sealed or partially sealed from the processing region 110 ( Figure 1 ) separated by .

[0046] The backside gas cavity may be supplied and exhausted with gas through the backside gas conduit 221. When the cavity 205 is filled with the backside gas, it further facilitates the transfer of thermal energy between the ESC 103 and the substrate 124. The backside gas supplied by the backside gas conduit passes through the porous plug 201. In some embodiments, the porous plug is disposed in the insulator plate 109.

[0047] Figure 3 A plug 201 for delivering a backside gas to a substrate disposed on an ESC 103 of a substrate support assembly 101 is shown. The plug 201 is configured to reduce the backside gas supply and pump down time when using a gas having an atomic mass greater than the atomic mass of helium, such as when utilizing argon or another inert gas. The fluid flow rate exhibited by the plug 201 depends on the porosity of the material used to make the plug 201. In some embodiments, the plug 201 is made of a cross-linked polystyrene material having a uniform porosity. In some embodiments, the plug 201 material has a dielectric constant between about 2 and about 3, such as about 2.5. In one embodiment, the porosity of the plug 201 is a function of the particle size of the material used to make the plug 201. In one embodiment, the particle size of the plug is between about 50 μm and about 200 μm, such as between about 100 μm and about 150 μm, such as between about 115 μm and about 130 μm. The selected particle size can affect the porosity of the plug 201. In one embodiment, a single particle size is used to make the plug 201. In this embodiment, the porosity of the plug 201 is substantially uniform. In another embodiment, a plurality of particle sizes can be used to make the plug 201. In this embodiment, the porosity of the plug 201 is uniform or non-uniform depending on the distribution of the different particle size materials within the plug 201.

[0048] Plug 201 has a top section 303 and a bottom section 307. Top section 303 has a top diameter 321, a top axial length 305, a top cross-sectional area, and a top volume. Bottom section 307 has a bottom diameter 319, a bottom axial length 309, a bottom cross-sectional area, and a bottom volume.

[0049] The top diameter 321 is between about 0.45 inches and about 0.55 inches. The top axial length 305 is between about 1 inch and about 1.3 inches. The top cross-sectional area is between about 0.15 square inches and about 0.2 square inches. The top volume is between about 0.2 cubic inches and about 0.3 cubic inches.

[0050] The bottom diameter 319 is between about 0.35 inches and about 0.45 inches. The bottom axial length 309 is between about 0.1 inches and about 0.3 inches. The bottom cross-sectional area is between about 0.1 square inches and about 0.2 square inches. The bottom volume is between about 0.02 cubic inches and about 0.04 cubic inches.

[0051] The top diameter 321 is greater than the bottom diameter 319. The top axial length 305 is greater than the bottom axial length 309. The cross-sectional area of ​​the bottom segment 307 is less than the cross-sectional area of ​​the top segment 303. The top segment 303 and the bottom segment 307 have a volume ratio between about 2 and about 12, such as between about 4 and about 10, for example, between about 7 and about 7.4. The top axial length 305 and the bottom axial length 309 have a ratio between about 2 and about 10, such as between about 4 and about 6, for example, between about 5.05 and about 5.07. In this embodiment, the plug 201 enables a larger amount of backside gas (e.g., argon) to flow through the plug 201, which results in an increase in the argon flow rate and ultimately an increase in production output.

[0052] Alternatively, the porosity, diameter, volume ratio, and axial length of the plug 201 may be varied to achieve an increased backside gas flow rate.

[0053] Plug 201 is disposed within insulator plate 109 having a top plug segment face 331 opposite bottom segment 307. Top segment 303 is disposed adjacent to or in contact with the bottom of facility plate 107. The upper surface of insulator plate 109, the lower surface of facility plate 107, and top plug segment face 331 are disposed in substantially the same plane. Plug 201 is at a connection to backside gas conduit 330. The backside gas conduit may be a single central flow line, or may be a network of conduits that pass through facility plate 107, ESC base 105, and ESC 103 to provide and exhaust backside gas to base plate 124.

[0054] The plug 201 is configured to allow gas to pass through but prevent arcing between the processing volume 110 and the ground plate 111 .

[0055] An elastomeric seal 313 surrounds the top plug segment face 331. The seal 313 is disposed between the insulator plate 109 and the facility plate 107. Alternatively, the seal 313 is recessed into the facility plate 107. The seal 313 enables sealing of gases at both high and low temperatures, and is capable of sealing against atmospheric and sub-atmospheric pressures. In another embodiment, the plug 201 is disposed within or adjacent to the ESC substrate 105, and the plug is configured to deliver gas through the plug to the back side of a substrate 124 disposed on the ESC 103.

[0056] Although the leakage rate of helium is generally greater than that of argon, utilizing the plug 201 to deliver argon to the back side of the substrate can significantly increase the leakage rate of argon therethrough and make the argon delivery rate comparable to or even greater than the helium delivery rate. Thus, by utilizing the plug 201, the time for argon back side gas delivery can be reduced and throughput gains can be achieved.

[0057] The plugs described herein allow helium to be replaced by argon as the backside gas. Helium is a known backside gas that enables high flow through other conventional plugs due to its smaller molecular size. Helium is expensive, which increases the cost of semiconductor manufacturing. Due to its larger molecular size, argon is incompatible with conventional backside gas plugs.

[0058] In addition to plugging, embodiments described herein also include methods of clamping substrates. In order to minimize the deleterious effects of suddenly applying high voltage to the clamping electrodes (which results in high forces on the substrate), the present disclosure provides a two-stage "soft" clamping process. That is, instead of applying the high voltage for clamping in a nearly instantaneous manner, the voltage is increased in two stages and ramped up from a lower set point to a higher set point. Although the exemplary embodiments discussed herein describe a two-stage clamping process, in other embodiments there may be three or more stages.

[0059] The rapid increase in clamping force can result in damage to the back side of the substrate. Generally speaking, the substrate is initially at room temperature prior to processing. In some processes, a single moderate to relatively high clamping voltage, such as 2,000 V, is applied by an electrostatic chuck (ESC) that applies force to the substrate. During some processes, the substrate temperature drops from room temperature to values ​​as low as -90°C as the substrate is in contact with the cooled ESC. Due to the significant temperature drop experienced by the clamped substrate (an electrostatic chuck maintained at a low temperature (e.g., ≤-90°C)), the substrate contracts radially. In some cases, the temperature of the substrate cannot be fully stabilized or equilibrated with the ESC temperature before the clamping process is completed and subsequent substrate processing steps are initiated. This, in turn, can result in damage to the substrate and / or the surface on which the substrate is located, as well as increased release of particles from the back side of the substrate.

[0060] However, the inventors have discovered that when a lower clamping voltage is applied in a first phase, and the substrate temperature is allowed to stabilize or equilibrate before a higher clamping voltage is applied in a second phase, the lower clamping voltage, and therefore the lower clamping force applied to the substrate during the first phase, results in fewer particles being generated on the back side of the substrate while the temperature of the substrate is equilibrated during this first phase. Since less force is applied while the temperature of the substrate is rapidly changing from room temperature to the temperature of the electrostatic chuck, the lower contact stress interaction between the back side of the substrate and the top surface of the electrostatic chuck minimizes the amount of physical damage to the substrate or the surface of the ESC on which the substrate is located.

[0061] The inventors have found that if a relatively low first stage clamping voltage is applied, such as between about 700V and about 900V, temperature stabilization between about -70°C and about -100°C is achieved in about 20 seconds to about 30 seconds. Once the substrate temperature has stabilized, a higher second stage clamping voltage, such as a voltage between about 1,900V and about 2,000V, can be applied to the clamping electrode to complete the clamping process and increase thermal contact between the back side of the substrate and the top surface of the ESC. Since the temperature difference between the back side of the substrate and the top surface of the electrostatic chuck is relatively small during the second stage, the relative movement between the back side of the substrate and the top surface of the electrostatic chuck due to thermal mismatch is small. For example, the temperature difference between the ESC and the base is less than 20°C, or less than 10°C, or less than 5°C, or even less than 3°C.

[0062] It should be understood that the specific voltage applied in each phase may be variable. For example, in other embodiments, the first phase voltage may be a value other than 800V, and the second phase voltage may be a value other than 2000V.

[0063] Preliminary testing indicates that using a two-stage soft clamping process with a 25 second first stage interval has no measurable effect on the amount of helium or argon leaking from the back side of the substrate at a set back side gas pressure when compared to a single stage clamping process. Therefore, using the two-stage clamping process discussed herein does not result in any increase in back side gas leakage compared to a single stage clamping process.

[0064] The results show an analysis of the number of particles released from the back side of the substrate in two embodiments. In the first embodiment, the back side gas applied to the substrate was helium. For this embodiment, when a 30 second time interval was used for the first stage duration, the number of particles larger than 2 microns was reduced from about 30,000 for the baseline (or single stage) clamping process to about 19,000 for the two stage clamping process. This resulted in a reduction of about 34% in the number of particles released from the back side of the substrate.

[0065] In a second embodiment, the backside gas applied to the substrate was argon. For this embodiment, the number of particles larger than 2 microns was reduced from about 30,000 for the baseline clamping process to about 5,000 for the two-stage clamping process, where a 30 second time interval was used for the first stage duration. This resulted in an approximately 83% reduction in the number of particles released from the backside of the substrate.

[0066] Figure 4 103. Figure 1 ) A clamping process 400 for clamping the substrate 124. The memory 138B includes instructions for executing and causing the process 400.

[0067] At operation 401, a substrate 124 is placed on an ESC 103 in a processing chamber 100. The processing chamber 100 may be under vacuum. The ESC temperature of the ESC 103 is below 0°C. For example, the temperature of the ESC 103 is below -10°C. For example, the temperature of the ESC 103 is below -50°C. For example, the temperature of the ESC 103 is between about -80°C and about -100°C, such as about -90°C.

[0068] At operation 403, the ESC 103 applies a first voltage to the clamping electrode 126. The first voltage is between about 700 V and about 900 V, for example, 800 V. The first voltage is generated by applying a voltage to the clamping electrode 126 ( Figure 2 ) to apply force to the substrate 124.

[0069] At operation 405, a backside gas is flowed to the substrate lower surface 203 at a first pressure from the ESC 103. The backside gas helps equalize the temperature between the ESC 103 and the substrate 124. In some embodiments, the substrate 124 enters the chamber 100 at a substrate temperature of about 10° C. to about 40° C., such as about 15° C. to about 30° C., such as about 20° C. The backside gas flows into the cavity 205 ( Figure 2 ). The first pressure is between about 10 Torr and about 20 Torr, such as between about 12 Torr and about 16 Torr. The backside gas helps equalize the substrate temperature and the ESC 103 temperature by increasing the transfer of thermal energy. In some embodiments, the backside gas is argon. In some embodiments, the backside gas is helium.

[0070] At operation 407, the ESC cools the substrate 124. The cooling is accomplished by transferring heat energy from the substrate to the ESC 103 through the backside gas. The substrate 124 is cooled to between about 10°C and about -100°C, for example, the substrate is cooled from about 25°C to -40°C. In some embodiments, the substrate is cooled from about -40°C to about -90°C in steps of 10°C. For example, -40°C to -50°C, to -60°C, to -70°C, to -80°C, to -90°C. The clamping time interval is between about 20 seconds and about 30 seconds. Operations 403, 405, and 407 occur within the clamping time interval. The operations may occur in the order shown or may occur simultaneously. During the clamping time interval, the substrate temperature is equalized to the ESC temperature. Equalization includes the substrate temperature differing from the ESC temperature by less than 100°C. Equalization includes the substrate temperature differing from the ESC temperature by less than 10°C. By allowing the substrate 124 to equilibrate at the first voltage and pressure, any deflection of the substrate occurs at a lower clamping force. A lower clamping force is less likely to damage the substrate 124 or generate particles from scratching.

[0071] At operation 409, a second voltage is applied to the clamping electrode 126 in the ESC 103. The second voltage is applied when the substrate temperature differs from the ESC temperature by less than 50°C. For example, the second voltage is applied when the temperature of the substrate is approximately the same as the temperature of the ESC. In some embodiments, the back gas pressure is also increased to a second pressure that is higher than the first pressure. The second voltage is applied after the clamping time interval. The second voltage is higher than the first voltage. In some embodiments, the second voltage is between about 1,800V and about 2,200V, such as 2,000V. Once the substrate temperature has been equalized with the temperature of the ESC, the second voltage is applied. In some embodiments, the change from the first voltage to the second voltage can be a linear rate, continuously increasing from the first voltage to the second voltage. In some embodiments, the second voltage is applied after about 25 seconds. The second pressure of the back gas is between about 10 Torr and about 20 Torr, such as between about 12 Torr and about 16 Torr.

[0072] Process 400 may include additional intermediate operations such that the voltage is increased in three or more increments. For example, process 300 may include four voltage increases. The voltage change between the first voltage and the second voltage may be a continuously changing voltage such that a linear slope (V / s) causes the voltage to ramp up from the first voltage to the second voltage.

[0073] Figure 5 A process 500 is shown for dechucking the substrate 124 from the ESC 103. The process 500, which includes a two-stage soft dechucking process, is performed after processing the substrate 124. The memory 138B includes instructions for executing and invoking the process 500.

[0074] At operation 501, the cavity 205 ( Figure 2 ) of the backside gas flow and / or pressure. In some embodiments, the backside gas flow to the cavity 205 is stopped and / or evacuated. In some embodiments, the backside gas pressure is reduced from the second pressure to the first pressure discussed previously. Once the backside gas pressure is reduced, the thermal energy transfer rate is reduced and the substrate temperature begins to increase.

[0075] At operation 503, the applied voltage is reduced. The applied voltage is between about 1,800 V and 2,200 V, such as 2,000 V. The applied voltage is reduced to a de-clamping voltage. The de-clamping voltage is between about 700 V and about 900 V, such as 800 V. The de-clamping voltage is determined by the clamping electrode 126 ( Figure 2 ) is imposed.

[0076] At operation 505, the substrate 124 is allowed to equilibrate to the ambient chamber temperature for a de-chucking interval. The de-chucking interval is between about 10 seconds and about 40 seconds, for example, about 12 seconds. In embodiments where the backside gas pressure is reduced, the backside gas pressure can be reduced during the de-chucking interval. For example, when the substrate temperature reaches between about -30°C and -50°C, the backside gas pressure is reduced from the second pressure to the first pressure. In some embodiments, the backside gas pressure is reduced from the second pressure to the first pressure in a shorter time than the de-chucking interval. In some embodiments, the applied voltage at the end of the de-chucking interval is reduced to the de-chucking voltage.

[0077] At operation 507, the backside gas pressure is further reduced from the first pressure to less than the first pressure. In some embodiments, the backside gas is stopped and / or evacuated and no longer applies force to the substrate.

[0078] At operation 509, the voltage is again reduced. In some embodiments, the voltage is reduced from the de-chucking voltage to 0V. In another embodiment, the voltage is reduced from the de-chucking voltage to a non-zero voltage, such as + / -200V. In yet another embodiment, the voltage is reduced from the de-chucking voltage to a non-zero voltage, such as ±50V, to balance any residual charge on the wafer. After operation 509, the substrate is no longer subject to the clamping force and can be removed from the processing chamber.

[0079] As described above, by applying a voltage to the substrate while equalizing the temperature and pressure, damage to the substrate and generated contaminants can be reduced.

[0080] While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope of the disclosure, and the scope of the disclosure is determined by the claims that follow.

Claims

1. A substrate support assembly, comprising: Electrostatic chuck; Insulator board; and A porous plug, the porous plug being disposed in the insulator plate, wherein the porous plug comprises: a first cylindrical section having a first volume and a first axial length; and a second cylindrical section having a second volume and a second axial length, wherein: The first volume is greater than the second volume; and The first axial length is greater than the second axial length.

2. The substrate support assembly of claim 1, wherein the porous plug further comprises a porosity as a function of a grain size, the grain size being between about 50 μm and about 200 μm.

3. The substrate support assembly of claim 1, wherein the first axial length is between 0.9" and 1.1".

4. The substrate support assembly of claim 1, wherein the first cylindrical section further comprises a first diameter and the second cylindrical section further comprises a second diameter, the second diameter being smaller than the first diameter.

5. The substrate support assembly of claim 4, wherein a ratio between the first diameter and the second diameter is between about 1 and about 1.

4.

6. The substrate support assembly of claim 1, wherein the first cylindrical section further comprises a first cross-sectional area, and the second cylindrical section further comprises a second cross-sectional area, the second cross-sectional area being smaller than the first cross-sectional area. 7 . The substrate support assembly of claim 6 , wherein a ratio between the first cross-section and the second cross-section is between about 1 and about 2. 8 . 8 . The substrate support assembly of claim 1 , wherein a length ratio between the first axial length and the second axial length is between about 2 and about 10. 9 . 9 . The substrate support assembly of claim 1 , wherein a volume ratio between the first volume and the second volume is between about 2 and about 12. 10 .

10. A processing chamber, comprising: one or more walls, the one or more walls enclosing a processing volume; and a substrate support assembly disposed in the processing volume, the substrate support assembly comprising: an electrostatic chuck disposed above the insulator plate; and A porous plug, the porous plug being disposed in the insulator plate, wherein the porous plug comprises: Materials, having porosity; a first cylindrical section having a first volume, a first diameter, and a first axial length; and A second cylindrical section has a second volume less than the first volume, a second diameter less than the first diameter, and a second axial length less than the first axial length.

11. The processing chamber of claim 10, wherein the porosity is a function of a grain size, the grain size being between about 50 μm and about 200 μm.

12. The processing chamber of claim 11, wherein the porous plug is configured to allow flow of an inert gas.

13. The processing chamber of claim 12, wherein the inert gas is argon at a temperature below about -40°C.

14. The processing chamber of claim 10, wherein the substrate support assembly further comprises a facility plate disposed between the processing volume and an insulator plate, the porous plug being disposed within the insulator plate.

15. The processing chamber of claim 10, wherein the material is cross-linked polystyrene.

16. The processing chamber of claim 10, wherein the material has a dielectric constant between about 2 and about 3.

17. The processing chamber of claim 10, wherein: a volume ratio between the volume of the first cylindrical section and the volume of the second cylindrical section of between about 2 and about 12; The first cylindrical section is disposed between the second cylindrical section and the processing volume; and A length ratio between the first axial length and the second axial length is between about 2 and about 10.

18. A porous plug, comprising: Cross-linked polystyrene material with uniform porosity; a first cylindrical section having a first volume, a first diameter, and a first axial length; and a second cylindrical section having a second volume less than the first volume, a second diameter less than the first diameter, and a second axial length less than the first axial length, wherein: a volume ratio between the volume of the first cylindrical section and the volume of the second cylindrical section of between about 2 and about 12; The first cylindrical section is disposed between the second cylindrical section and a processing volume; and A length ratio between the first axial length and the second axial length is between about 2 and about 10.

19. The porous plug of claim 18, wherein a ratio between the first diameter and the second diameter is between about 1 and about 1.

4.

20. The porous plug of claim 18, wherein the porosity is a function of grain size, the grain size being between about 50 μm and about 200 μm.

21. A method of clamping a substrate to a surface of an electrostatic chuck (ESC) in a processing chamber, the method comprising: applying a first voltage to a clamping electrode in the ESC during a clamping time interval; supplying an inert gas at a first pressure to a back side of the substrate during the clamping time interval; applying a second voltage to the clamping electrode after the clamping time interval, the second voltage being higher than the first voltage; as well as The inert gas is supplied to the back side of the substrate at a second pressure after the chucking time interval, the second pressure being higher than the first pressure of the inert gas.

22. The method of claim 21, wherein the inert gas is argon.

23. The method of claim 21, further comprising: Prior to applying the second voltage, a substrate temperature and an ESC temperature are equalized such that the substrate temperature and the ESC temperature differ by less than about 50° C., wherein the substrate temperature decreases during the clamping time interval.

24. The method of claim 21, wherein the first voltage is between about 700V and about 900V.

25. The method of claim 21, wherein the second voltage is between about 1900V and about 2100V.

26. The method of claim 21, wherein the clamping time interval is between about 20 seconds and about 30 seconds.

27. The method of claim 21, further comprising: The substrate is cooled to a first temperature during the clamping time interval.

28. The method of claim 21, further comprising: The substrate temperature and the ESC temperature are equalized during the clamping time interval.

29. The method of claim 21, wherein the ESC is at a temperature lower than the temperature of the substrate.

30. A method of de-chucking a substrate from a surface of an electrostatic chuck (ESC) in a processing chamber, the method comprising: reducing a backside gas pressure at a lower surface of the substrate; reducing a voltage applied to a clamping electrode within the ESC to a de-chucking voltage after reducing the pressure; Increase the substrate temperature to the de-clamping interval; reducing the backside gas pressure after the dechucking interval; and The de-chucking voltage is reduced.

31. The method of claim 30, wherein the ESC temperature of the ESC is maintained at a temperature below -10°C.

32. The method of claim 30, wherein the de-clamping interval is between about 10 seconds and about 40 seconds.

33. The method of claim 30, wherein reducing the applied voltage to a de-chucking voltage comprises: The applied voltage is reduced from between about 1900V and about 2100V to between about 700V and about 900V.

34. The method of claim 30, wherein equalizing the substrate temperature comprises: The substrate temperature is increased during the dechucking interval.

35. A substrate processing chamber, the substrate processing chamber comprising: an electrostatic chuck (ESC) in fluid communication with the cryogenic freezer; as well as A controller comprising a central processing unit (CPU), supporting circuits, and a non-transitory computer readable medium comprising instructions for clamping a substrate, the instructions when executed resulting in: applying a first voltage to a clamping electrode in the ESC for a first time interval; applying an inert gas at a first pressure to the back side of the substrate for the first time interval; applying a second voltage to the clamping electrode for a second time interval after the first time interval, the second voltage being higher than the first voltage; as well as An inert gas at a second pressure is applied to the back side of the substrate for the second time interval, the second amount of the inert gas being lower than the first amount of the inert gas.

36. The substrate processing chamber of claim 35, wherein the instructions further result in: The backside gas pressure decreases at the lower surface of the substrate; After reducing the pressure, reducing the voltage applied to the clamping electrode to a de-clamping voltage; allowing the temperature of the substrate to increase for a dechucking interval; reducing the backside gas pressure after the dechucking interval; and The de-chucking voltage is reduced after the de-chucking interval.

37. The substrate processing chamber of claim 36, wherein the inert gas is argon.

38. The substrate processing chamber of claim 35, wherein the first voltage is between about 700V and about 900V.

39. The substrate processing chamber of claim 35, wherein the first time interval is between about 20 seconds and about 40 seconds.

40. The substrate processing chamber of claim 35, wherein the second time interval is greater than two seconds.

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