Tunable selective lateral ETCH of silicon using radical species

Abstract

A method for selectively etching silicon with respect to at least one of a silicon oxide, silicon nitride, and silicon germanium containing layer in a stack is provided. An etchant gas comprising a halogen containing component is provided. A radicalizer gas is provided, wherein the radicalizer gas causes the halogen containing component to provide halogen radicals without providing a plasma. The stack is exposed to the halogen radicals causing the silicon to be selectively etched.

Description

TUNABLE SELECTIVE LATERAL ETCH OF SILICON USING RADICAL SPECIES CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of priority of U.S. Application No. 63 / 611,052, filed December 15, 2023, which is incorporated herein by reference for all purposes.BACKGROUND

[0002] The disclosure relates to a method of forming semiconductor devices on a semiconductor wafer.

[0003] The background description provided here is for the purpose of generally presenting the context of the disclosure. Information described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.

[0004] Substrate processing systems may be used to treat substrates such as semiconductor wafers. The substrate treatments may include deposition, etching, cleaning, and / or other treatments. During processing, a substrate may be arranged on a substrate support in a processing chamber of the substrate processing system. Gas mixtures are introduced into the processing chamber using a gas delivery device. In some processes, plasma may be used to initiate chemical reactions.SUMMARY

[0005] To achieve the foregoing and in accordance with the purpose of the present disclosure, a method for selectively etching silicon with respect to at least one of a silicon oxide, silicon nitride, and silicon germanium containing layer in a stack is provided. An etchant gas comprising a halogen containing component is provided. A radicalizer gas is provided, wherein the radicalizer gas causes the halogen containing component to provide halogen radicals without providing a plasma. The stack is exposed to the halogen radicals causing the silicon to be selectively etched.

[0006] In another manifestation, an apparatus for selectively etching silicon with respect to at least one of silicon germanium, silicon oxide, and silicon nitride in a stack is provided. A substrate support is configured to support the stack in a chamber. A halogen containing component source provides a halogen containing component to the chamber. A radicalizer gas source provides a radicalizer gas to the chamber. A heater heats the substrate support. A pump removes vapor from the chamber. A controller is controllably connected to the heater, the halogen containing component source, and the radicalizer gas source and is configured to provide a halogen containing component from the halogen containing component source andprovide a radicalizer gas from the radicalizer gas source.

[0007] These and other features of the present disclosure will be described in more detail below in the detailed description and in conjunction with the following figures.BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The present disclosure is illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings and in which like reference numerals refer to similar elements and in which:

[0009] FIG. 1A is a functional block diagram of an example of a substrate processing system for selective thermal etchant using thermally generated radicals according to the present disclosure.

[0010] FIG. IB is a functional block diagram of another example of a substrate processing system for selective thermal and radical etching according to the present disclosure.

[0011] FIG. 2 is a flowchart of an example of a method for selective thermal and radical etching according to the present disclosure.

[0012] FIGS. 3A-E are schematic cross-sectional views of stacks that are processed according to various processes.

[0013] FIG. 4A is a schematic view of a substrate processing chamber that is used in an embodiment.

[0014] FIG. 4B is a schematic view of a substrate processing chamber that is used in an embodiment.

[0015] FIG. 5 is a schematic cross-sectional view of features etched in a stack according to an etch provided by the processing chamber shown in FIG. 4A.

[0016] FIGS. 6 is a schematic cross-sectional view of features etched in a stack according to an etch provided by the processing chamber shown in FIG. 4B.

[0017] FIG. 7 illustrates a computer system for implementing a controller used in some embodiments.

[0018] In the drawings, like reference numerals are sometimes used to designate like structural elements. It should also be appreciated that the depictions in the figures are diagrammatic and not to scale.DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] The present disclosure will now be described in detail with reference to a few preferred embodiments thereof as illustrated in the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understandingof the present disclosure. It will be apparent, however, to one skilled in the art, that the present disclosure 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 disclosure.

[0020] Traditional selective etching of silicon (Si) usually leverages plasma-based processes containing nitrogen trifluoride (NF3), carbon tetrafluoride (CF4), or silicon hexafluoride (SiFe). While plasma processes are quite robust, the ions and radicals produced typically span a broad energy range, thus causing them to routinely fall short when it comes to uniform lateral etch and often lack the needed sensitivity to ensure sufficient selectivity between Si and other silicon containing materials such as silicon nitride (SiN), silicon germanium (SiGe), and silicon oxide (SiCh). Without the ability to provide selective and uniform lateral etch, there is a wide swath of applications, such as three dimensional “not and” devices (3D-NAND) and three dimensional random access memory (3D-DRAM) that are unattainable with plasma alone, thus leaving a major gap for any process with such capabilities. The use of these plasma processes inherently limits the scope of Si etch to applications with low feature aspect ratios and a minimal need for high degrees of selectivity.

[0021] Some embodiments pair a traditional thermal etchant, Fz / Ar (fluorine gas in Argon), with a species that is capable of generating radicals thermally and adding chemical additives to generate thermal radicals for a tunable selective lateral Si etch.

[0022] Achieving uniform lateral recess across the entire depth of a high aspect ratio (HAR) structure is challenging. Some embodiments provide a selective lateral etch of silicon with respect to at least one of SiCh, SiN, and SiGe, by exposing the silicon to an etch gas and a radicalizer gas. The etch gas comprises a halogen containing component. The radicalizer gas causes the halogen containing component to provide halogen radicals without requiring a plasma. An additive gas may be provided to increase selectivity and also improve lateral silicon etch uniformity along the depth of high aspect ratio features.Apparatus

[0023] To facilitate understanding, FIG. 1A depicts a cross-sectional side view of an example apparatus in accordance with disclosed embodiments. As detailed below, this apparatus 100 is capable of rapidly and precisely controlling the temperature of a substrate, including performing thermal etching operations. The apparatus 100 includes a processing chamber 102, apedestal 104 having a substrate heater 106 and a plurality of substrate supports 108 configured to support a substrate 118, and a gas distribution unit 110.

[0024] The processing chamber 102 includes side chamber walls 112A, a top 112B, and a bottom 112C, that at least partially define the chamber interior 114, which may be considered a plenum volume. As stated herein, it may be desirable in some embodiments to actively control the temperature of the processing chamber walls 112A, top 112B, and bottom 112C in order to prevent unwanted condensation on their surfaces. Some emerging semiconductor processing operations flow vapors, such as water and / or alcohol vapor, onto the substrate which adsorb onto the substrate, but they may also undesirably adsorb onto the chamber’s interior surfaces. This can lead to unwanted deposition and etching on the chamber interior surfaces which can damage the chamber surfaces and cause particulates to flake off onto the substrate thereby causing substrate defects. In order to reduce and prevent unwanted condensation on the chamber’s interior surfaces, the temperature of the chamber’s walls, top, and bottom may be maintained at a temperature at which condensation of chemistries used in the processing operations does not occur.

[0025] This active temperature control of the chamber’s surfaces may be achieved by using heaters to heat the chamber walls 112A, the top 112B, and the bottom 112C. As illustrated in FIG. 1A, chamber heaters 116A are positioned on and configured to heat the chamber walls 112 A, chamber heaters 116B are positioned on and configured to heat the top 112B, and chamber heaters 116C are positioned on and configured to heat the bottom 112C. The chamber heaters 116A-116C may be resistive heaters that are configured to generate heat when an electrical current is flowed through a resistive element. Chamber heaters 116A-116C may also be fluid conduits through which a heat transfer fluid may be flowed, such as a heating fluid which may include heated water. In some instances, the chamber heaters 116A-116C may be a combination of both heating fluid and resistive heaters. The chamber heaters 116A-116C are configured to generate heat in order to cause the interior surfaces of each of the chamber walls 112A, the top 112B, and the bottom 112C to the desired temperature, which may range between about 40° C. and about 150° C., including between about 80° C. and about 130° C., about 90° C. or about 120° C., for instance. It has been discovered that under some conditions, water and alcohol vapors do not condense on surfaces kept at about 90° C. or higher.

[0026] The chamber walls 112 A, top 112B, and bottom 112C may also be comprised of various materials that can withstand the chemistries used in the processing techniques. These chamber materials may include, for example, aluminum, anodized aluminum, aluminum with apolymer, such as a plastic, a metal or metal alloy with a yttria coating, a metal or metal alloy with a zirconia coating, and a metal or metal alloy with aluminum oxide coating; in some instances the materials of the coatings may be blended or layers of differing material combinations, such as alternating layers of aluminum oxide and yttria, or aluminum oxide and zirconia. These materials are configured to withstand the chemistries used in the processing techniques, such as anhydrous HF, water vapor, methanol, isopropyl alcohol, chlorine, fluorine gases, nitrogen gas, hydrogen gas, helium gas, and the mixtures thereof.

[0027] The apparatus 100 may also be configured to perform processing operations at or near a vacuum, such as at a pressure of about 0.1 Torr to about 100 Torr, or about 20 Torr to about 200 Torr, or about 0.1 Torr to about 10 Torr. This may include a vacuum pump 184 configured to pump the chamber interior 114 to low pressures, such as a vacuum having a pressure of about 0.1 Torr to about 100 Torr, including about 0.1 Torr to about 10 Torr, and about 20 Torr to about 200 Torr, or about 0.1 Torr to about 10 Torr.

[0028] Various features of the pedestal 104 will now be discussed. The pedestal 104 includes a heater 122 (encompassed by the dashed rectangle in FIG. 1 A) that has a printed circuit board (PCB) 126 and a plurality of LEDs 124 that are configured to emit visible light having wavelengths including and between 400 nm to 800 nm, including 450 nm. The heater LEDs emit this visible light onto the backside of the substrate which heats the substrate. Visible light having wavelengths from about 400 nm to 800 nm is able to quickly and efficiently heat silicon wafers from ambient temperature, e.g., about 20° C., to about 600° C. because silicon absorbs light within this range. In contrast, radiant, including infrared radiant, heating may ineffectively heat silicon at temperatures up to about 400° C. because silicon tends to be transparent to infrared at temperatures lower than about 400° C. Additionally, radiant heaters that directly heat the topside of a wafer, as in many conventional semiconductor processes, can cause damage or other adverse effects to the topside films. Many “hot plate” heaters that rely on solid-to-solid thermal transference between the substrate and a heating platen, such as a pedestal with a heating coil, have relatively slow heating and cooling rates and provide non-uniform heating which may be caused by substrate warping and inconsistent contact with the heating platen. For example, it may take multiple minutes to heat some pedestals to a desired temperature, and from a first to a second higher temperature, as well as to cool the pedestal to a lower temperature.

[0029] The pedestal may include reflective material on its internal surfaces that, during operation, reflects and directs the light emitted by the LEDs onto the backside of the substrate supported by the pedestal. In some such embodiments, the substrate heater may include suchreflective material positioned on a top surface 140, as shown in FIG. 1A, of the PCB 126 on which the plurality of LEDs 124 is positioned. The reflective material may be comprised of aluminum, such as polished aluminum, stainless steel, aluminum alloys, nickel alloys, and other protective layers that can prevent oxidation of the metal and / or enhance the reflectivity at specific wavelengths, such as reaching greater than 99% reflectivity for specific wavelengths, and other durable reflective coatings. Additionally or alternatively, the pedestal 104 may have a bowl 146 in which the substrate heater 122 is at least partially positioned. The bowl 146 may have exposed internal surfaces 148 of the pedestal sidewalls 149 upon which the reflective material may be positioned. This reflective material increases the heating efficiency of the substrate heater and reduces the unwanted heating of the PCB 126 and pedestal 104 by advantageously directing light back onto the substrate that would have otherwise been absorbed by the PCB 126 and the pedestal 104.

[0030] In some embodiments, the substrate heater may also include a pedestal cooler that is thermally connected to the LEDs such that heat generated by the plurality of LEDs can be transferred from the LEDs to the pedestal cooler. This thermal connection is such that heat can be conducted from the plurality of LEDs to the pedestal cooler along one or more heat flow pathways between these components. In some instances, the pedestal cooler is in direct contact with one or more elements of the substrate heater, while in other instances other conductive elements, such as thermally conductive plates (e.g., that comprise a metal) are interposed between the substrate heater and the pedestal cooler. The substrate heater includes a pedestal cooler 136 in direct contact with the bottom of the PCB 126. Heat is configured to flow from the LEDs, to the PCB 126, and to the pedestal cooler 136. The pedestal cooler 136 also includes a plurality of fluid conduits 138 through which a heat transfer fluid, such as water, is configured to flow in order to receive the heat and thus cool the LEDs in the substrate heater 122. The fluid conduits 138 may be connected to a reservoir and pump, not pictured, located outside the chamber. In some instances, the pedestal cooler may be configured to flow water that is cooled, such as between about 5° C. and 20° C.

[0031] As provided herein, it may be advantageous to actively heat the exterior surfaces of the processing chamber 102. In some instances, it may similarly be advantageous to heat the exterior surfaces of the pedestal 104 in order to prevent unwanted condensation and deposition on its external surfaces. As illustrated in FIG. 1A, the pedestal 104 may further include a pedestal heater 144 inside of the pedestal 104 that is configured to heat the exterior surfaces of the pedestal 104, including its sides 142A and bottom 142B. The pedestal heater 144 mayinclude one or more heating elements, such as one or more resistive heating elements and fluid conduits in which a heating fluid is configured to flow. In some instances, the pedestal cooler and the pedestal heater may both have fluid conduits that are fluidically connected to each other such that the same heat transfer fluid may flow in both the pedestal cooler and the pedestal heater. In these embodiments, the fluid may be heated to between 50° C. and 130° C. including about 90° C. and 120° C.

[0032] The pedestal may also include a window to protect the substrate heater, including the plurality of LEDs, from damage caused by exposure to the processing chemistries and pressures used during processing operations. As illustrated in FIG. 1A, the window 150 may be positioned above the substrate heater 122 and may be sealed to the sidewall 149 of the pedestal 104 in order to create a plenum volume within the pedestal that is fluidically isolated from the chamber interior. This plenum volume may also be considered the inside of the bowl 146. The window may be comprised of one or more materials that are optically transparent to the visible light emitted by LEDs, including light having wavelengths in the range of 400 nm to 800 nm. In some embodiments, this material may be quartz, sapphire, quartz with a sapphire coating, or calcium fluoride (CaF). The window may also not have any holes or openings within it. In some embodiments, the heater may have a thickness of 15 to 30 mm, including 20 mm and 25 mm.

[0033] As shown in FIG. 1A, the pedestal’s 104 substrate supports 108 are configured to support the substrate 118 above and offset from the window 150 and the substrate heater 122. In certain embodiments, the temperature of the substrate can be rapidly and precisely controlled by thermally floating, or thermally isolating, the substrate within the chamber. The heating and cooling of a substrate are directed at both the substrate’s thermal mass and the thermal masses of other items in contact with the substrate. For instance, if the substrate is in thermal contact with a large body, such as the entirety of the substrate’s back side resting on a large surface of a pedestal or electrostatic chuck as in many conventional etching apparatuses, this body acts as a heat sink for the substrate which affects the ability to accurately control the substrate temperature and reduces the quickness of substrate heating and cooling. It is therefore desirable to position the substrate so that the smallest thermal mass is heated and cooled. This thermal floating is configured to position the substrate so that it has minimal thermal contact (which includes direct and radiation) with other bodies in the chamber.

[0034] The pedestal 104 is therefore configured, in some embodiments, to support the substrate 118 by thermally floating, or thermally isolating, the substrate within the chamber interior 114. The pedestal’s 104 plurality of substrate supports 108 are configured to support thesubstrate 118 such that the thermal mass of the substrate 118 is reduced as much as possible to the thermal mass of just the substrate 118. Each substrate support 108 may have a substrate support surface 120 that provides minimal contact with the substrate 118. The number of substrate supports 108 may range from at least 3 to, for example, at least 6 or more. The surface area of the support surface 120 may also be the minimum area required to adequately support the substrate during processing operations (e.g., in order to support the weight of the substrate and prevent inelastic deformation of the substrate). In some embodiments, the surface area of one support surface 120 may be less than about 0.1%, less than about 0.075%, less than about 0.05%, less than about 0.025%, or less than about 0.01%, for instance.

[0035] In some embodiments, the pedestal 104 is also configured to move vertically. This may include moving the pedestal such that a gap 186 between a faceplate 176 of the gas distribution unit 110 and the substrate 118 is capable of being in a range of 2 mm and 70 mm. As provided in more detail below, moving the pedestal vertically may enable active cooling of the substrate as well as rapid cycling time of processing operations, including flowing gas and purging, due to a low volume created between the gas distribution unit 110 and the substrate 118. This movement may also enable the creation of a small process volume between the substrate and the gas distribution unit which can result in a smaller purge and process volume and thus reduce purge and gas movement times and increase throughput.

[0036] The gas distribution unit 110 is configured to flow process gases, which may include liquids and / or gases, such as a reactant, modifying molecules, converting molecules, or removal molecules, onto the substrate 118 in the chamber interior 114. The gas distribution unit 110 includes one or more fluid inlets 170 that are fluidically connected to one or more gas sources 172 and / or one or more vapor sources 174. In some embodiments, the gas lines and mixing chamber may be heated to prevent unwanted condensation of the vapors and gases flowing within. These lines may be heated to at least about 40° C., at least about 80° C., at least about 90° C., at least about 120° C., at least about 130° C., or at least about 150° C. The one or more vapor sources may include one or more sources of gas and / or liquid that is vaporized. The vaporizing may be a direct inject vaporizer, a flow over vaporizer, or both. The gas distribution unit 110 also includes the faceplate 176 that includes a plurality of through-holes 178 that fluidically connect the gas distribution unit 110 with the chamber interior 114. These through- holes 178 are fluidically connected to the one or more fluid inlets 170 and also extend through a front surface 177 of the faceplate 176, with the front surface 177 configured to face thesubstrate 118. In some embodiments, the gas distribution unit 110 may be considered a top plate and in some other embodiments, it may be considered a showerhead.

[0037] The through-holes 178 may be configured in various ways in order to deliver uniform gas flow onto the substrate. In some embodiments, these through-holes may all have the same outer diameter, such as between about 0.03 inches and 0.05 inches, including about 0.04 inches (1.016 mm). These faceplate through-holes may also be arranged throughout the faceplate in order to create a uniform flow out of the faceplate.

[0038] The gas distribution unit 110 may also include a unit heater 180 that is thermally connected to the faceplate 176 such that heat can be transferred between the faceplate 176 and the unit heater 180. The unit heater 180 may include fluid conduits in which a heat transfer fluid may be flowed. Similar to the above, the heat transfer fluid may be heated to a temperature range of about 20° C. and 120° C., for example. In some instances, the unit heater 180 may be used to heat the gas distribution unit 110 to prevent unwanted condensation of vapors and gases; in some such instances, this temperature may be at least about 90° C. or 120° C.

[0039] In some embodiments, the gas distribution unit 110 may include a second unit heater 182 that is configured to heat the faceplate 176. This second unit heater 182 may include one or more resistive heating elements, fluid conduits for flowing a heating fluid, or both. Using two heaters 180 and 182 in the gas distribution unit 110 may enable various heat transfers within the gas distribution unit 110. This may include using the first and / or second unit heaters 180 and 182 to heat the faceplate 176 in order to provide a temperature-controlled chamber, as described above, in order to reduce or prevent unwanted condensation on elements of the gas distribution unit 110.

[0040] The apparatus 100 may also be configured to cool the substrate. This cooling may include flowing a cooling gas onto the substrate, moving the substrate close to the faceplate to allow heat transfer between the substrate and the faceplate, or both. Actively cooling the substrate enables more precise temperature control and faster transitions between temperatures which reduces processing time and improves throughput. In some embodiments, the first unit heater 180 that flows the heat transfer fluid through fluid conduits may be used to cool the substrate 118 by transferring heat away from the faceplate 176 that is transferred from the substrate 118. A substrate 118 may therefore be cooled by positioning it in close proximity to the faceplate 176, such as by a gap 186 of less than or equal to 5 mm or 2 mm, such that the heat in the substrate 118 is radiatively transferred to the faceplate 176 and transferred away from thefaceplate 176 by the heat transfer fluid in the first unit heater 180. The faceplate 176 may therefore be considered a heat sink for the substrate 118 in order to cool the substrate 118.

[0041] In some embodiments, the apparatus 100 may further include a cooling fluid source 173 which may contain a cooling fluid (a gas or a liquid), and a cooler (not pictured) configured to cool the cooling fluid to a desired temperature, such as less than or equal to at least about 90° C., at least about 70° C., at least about 50° C., at least about 20° C., at least about 10° C., at least about 0° C., at least about -50° C., at least about -100° C., at least about -150° C., at least about -190° C., at least about -200° C., or at least about -250° C., for instance. The apparatus 100 includes piping to deliver the cooling fluid to the one or more fluid inlets 170, and the gas distribution unit 110 which is configured to flow the cooling fluid onto the substrate. In some embodiments, the fluid may be in a liquid state when it is flowed to the chamber 102 and may turn to a vapor state when it reaches the chamber interior 114, for example, if the chamber interior 114 is at a low pressure state, such as described above, e.g., between about 0.1 Torr and 10 Torr, or between about 0.1 Torr and 100 Torr, or between about 20 Torr and 200 Torr, for instance. The cooling fluid may be an inert element, such as nitrogen, argon, or helium. In some instances, the cooling fluid may include, or may only have, a non-inert element or mixture, such as hydrogen gas. In some embodiments, the flow rate of the cooling fluid into the chamber interior 114 may be at least about 0.25 liters per minute, at least about 0.5 liters per minute, at least about 1 liters per minute, at least about 5 liters per minute, at least about 10 liters per minute, at least about 50 liters per minute, or at least about 100 liters per minute, for example. In certain embodiments, the apparatus may be configured to cool a substrate at one or more cooling rates, such as at least about 5° C. / second, at least about 10° C. / second, at least about 15° C. / second, at least about 20° C. / second, at least about 30° C. / second, or at least about 40° C. / second.

[0042] A pyrometer may include an emitter configured to emit infrared signals and a detector configured to receive emissions. The pyrometer 188 has an emitter within the pyrometer 188 and a detector 190. The pyrometer 188 may be configured to emit signals on one side of the substrate, either the top or the bottom, and configured to receive signals on the other side of the substrate. For instance, the emitter may emit signals on the top of the substrate and the detector is under the substrate and receives signals emitted through and under the substrate. The apparatus may therefore have at least a first port 192A on the top of the chamber 102, such as the port 192A through the center of the gas distribution unit 110, and a second port 192B through the pedestal 104 and substrate heater 122. The emitter in the pyrometer 188 may beconnected to one of the ports 192A or 192B via a fiberoptic connection, such as the first port 192 A as shown in FIG. I A, and the detector is optically connected to the other port, such as the second port 192B. The first port 192A may include a port window 194 to seal the first port 192A from the chemistries within the chamber interior 114. The second port 192B is seen in FIG. 1A extending through the pedestal 104 and the substrate heater such that the emitter’s emissions can pass through the substrate, through the window 150, into the second port 192B, and to the detector 190 that may be positioned in the second port or optically connected to the second port through another fiberoptic connection (not shown). In some other embodiments, the emitter and the detector are flipped, such that the emitter emits through the second port 192B and the detector detects through the first port 192A.

[0043] The apparatus 100 may also include one or more optical sensors 198 to detect one or more metrics of the visible light emitted by the LEDs. In some embodiments, these optical sensors may be one or more photodetectors configured to detect the light and / or light intensity of the light emitted by the LEDs of the substrate heater. In FIG. 1A, a single optical sensor 198 is shown as connected to the chamber interior 114 via a fiberoptic connection such that the optical sensor 198 is able to detect light emitted by the substrate heater 122. The optical sensor 198, and additional optical sensors, can be positioned in various locations in the top and sides, for instance, of the chamber 102 in order to detect the emitted light at various locations within the chamber 102. This may enable the measurement and adjustment of the substrate heater, such as the adjustment of one or more independently controllable zones of the LEDs. In some embodiments, there may be a plurality of optical sensors 198 arranged along a circle or multiple concentric circles in order to measure various regions of the LEDs throughout the chamber 102. In some embodiments, the optical sensors may be positioned inside the chamber interior 114.

[0044] In some embodiments, the apparatuses described herein may include a controller that is configured to control various aspects of the apparatus in order to perform the techniques described herein. Apparatus 100 includes a controller 131 (which may include one or more physical or logical controllers) that is communicatively connected with and that controls some or all of the operations of a processing chamber. The system controller 131 may include one or more memory devices 133 and one or more processors 135. In some embodiments, the apparatus includes a switching system for controlling flow rates and durations, the substrate heating unit, the substrate cooling unit, the loading and unloading of a substrate in the chamber, the thermal floating of the substrate, and the process gas unit, for instance, when disclosed embodiments are performed. In some embodiments, the apparatus may have a switching time of up to about 500ms, or up to about 750 ms. Switching time may depend on the flow chemistry, recipe chosen, reactor architecture, and other factors. In some embodiments, the apparatus 100 corresponds to a Prevos® processing chamber available from Lam Research Corporation of Fremont, CA that is shown and described in US Patent Publication 20230131233, which is hereby incorporated by reference in its entirety for all purposes.

[0045] Referring now to FIG. IB, another example of a substrate processing chamber 200 that may be used in an embodiment. In some examples, the substrate processing chamber 200 corresponds to a Selis® processing chamber available from Lam Research Corporation of Fremont, CA.

[0046] The substrate processing chamber 200 includes a lower chamber region 202 and an upper chamber region 204. The lower chamber region 202 is defined by chamber sidewall surfaces 208, a chamber bottom surface 210, and a lower surface of a gas distribution device 214. In some examples, the gas distribution device 214 is omitted.

[0047] The upper chamber region 204 is defined by an upper surface of the gas distribution device 214 and an inner surface of an upper chamber wall 218 (for example a dome-shaped chamber). In some examples, the upper chamber wall 218 rests on a first annular support 221. In some examples, the first annular support 221 includes one or more gas flow channels and / or holes 223 for delivering process gas to the upper chamber region 204, as will be described further below. The gas flow channels and / or holes 223 may be uniformly spaced around a periphery of the upper chamber region 204. In some examples, the process gas is delivered by the one or more gas flow channels and / or holes 223 in an upward direction at an acute angle relative to a plane including the gas distribution device 214, although other angles / directions may be used. In some examples, a plenum 234 in the first annular support 221 supplies gas to the one or more spaced gas flow channels and / or holes 223.

[0048] The first annular support 221 may rest on a second annular support 225 that defines one or more gas flow channels and / or holes 227 for delivering process gas to the lower chamber region 202. In some examples, holes 231 in the gas distribution device 214 align with the gas flow channels and / or holes 227. In other examples, the gas distribution device 214 has a smaller diameter and the holes 231 are not needed. In some examples, the process gas is delivered by the one or more spaced gas flow channels and / or holes 227 in a downward direction towards the substrate at an acute angle relative to the plane including the gas distribution device 214, although other angles / directions may be used.

[0049] In other examples, the upper chamber region 204 is cylindrical with a flat top surface and one or more flat inductive coils may be used. In still other examples, a single chamber may be used with a spacer located between a showerhead and the substrate support.

[0050] A substrate support 222 is arranged in the lower chamber region 202. In some examples, the substrate support 222 includes an electrostatic chuck (ESC), although other types of substrate supports can be used. A substrate 226 is arranged on an upper surface of the substrate support 222 during etching. In some examples, the temperature of the substrate 226 may be controlled by a heater plate 241, an optional cooling plate with fluid channels, and one or more sensors (not shown); although any other suitable substrate support temperature control system may be used. In some examples, a temperature controller 243 may be used to control the heating and cooling of the substrate support 222. Heating may be performed by the heater plate 241 and cooling may be performed by the cooling plate with fluid channels 245.

[0051] A temperature controller 247 may be used to control the temperature of the gas distribution device 214 by supplying heating / cooling fluid to a plenum in the gas distribution device 214. The temperature controllers 243 and / or 247 may further include a source of fluid, a pump, control valves, and a temperature sensor (all not shown).

[0052] In some examples, the gas distribution device 214 includes a showerhead (for example, a plate 228 having a plurality of spaced holes 229). The plurality of spaced holes 229 extends from the upper surface of the plate 228 to the lower surface of the plate 228.

[0053] One or more inductive coils 240 are arranged around an outer portion of the upper chamber wall 218. When energized, the one or more inductive coils 240 create an electromagnetic field inside of the upper chamber wall 218. In some examples, an upper coil and a lower coil are used. A gas injector 242 injects one or more gas mixtures from a gas delivery system 250-1 into the upper chamber region 204.

[0054] In some examples, a gas delivery system 250-1 includes one or more gas sources 252, one or more valves 254, one or more mass flow controllers (MFCs) 256, and a mixing manifold 258, although other types of gas delivery systems may be used. A gas splitter (not shown) may be used to vary the flow rates of a gas mixture. Another gas delivery system 250-2 may be used to supply the chemical additive or other gas mixtures to the gas flow channels and / or holes 223 and / or 227 (in addition to or instead of etch gas from the gas injector 242).

[0055] In some examples, the gas injector 242 includes a center injection location that directs gas in a downward direction and one or more side injection locations that inject gas at an angle with respect to the downward direction.

[0056] A plasma generator 270 may be used to generate radio frequency (RF) power that is output to the one or more inductive coils 240. RF power may have a sinusoidal or other waveform. Plasma is generated in the upper chamber region 204. In some examples, the plasma generator 270 includes an RF generator 272 and a matching network 274. The matching network 274 matches the impedance of the RF generator 272 to the impedance of the one or more inductive coils 240. In some examples, the gas distribution device 214 is connected to a reference potential such as ground. A valve 278 and a pump 280 may be used to control pressure inside of the lower and upper chamber regions 202, 204 and to evacuate reactants.

[0057] A controller 276 communicates with the gas delivery systems 250-1 and 250-2, the valve 278, the pump 280, and / or the plasma generator 270 to control the flow of process gas, purge gas, tuning gas, RF plasma, and chamber pressure. In some examples, plasma is sustained inside the upper chamber wall 218 by the one or more inductive coils 240. One or more gas mixtures are introduced from a top portion of the chamber using the gas injector 242 (and / or gas flow channels and / or holes 223) and plasma is confined within the upper chamber wall 218 using the gas distribution device 214.

[0058] In other examples, an RF bias generator 284 is provided and includes an RF generator 286 and a matching network 288. The RF bias can be used to create plasma between the gas distribution device 214 and the substrate support or to create a self-bias on substrate 226 to attract ions. The controller 276 may be used to control the RF bias.

[0059] During selective etching according to the present disclosure, a gas mixture including etchant gas and radicalizer gas is supplied together with an optional chemical additive gas and is mixed in the upper chamber. In other examples, the optional chemical additive gas is supplied to the processing chamber separately from the etchant gas and the radicalizer gas. For example, when ammonia is used as the chemical additive, it can be supplied separately to prevent chemical interactions in gas supply lines. In some examples, the RF generator and / or RF bias generator and related structures are omitted.Process

[0060] To facilitate understanding, FIG. 2 is a flow chart of a process that may be used in some embodiments. A stack is placed in a process chamber (step 290). FIG. 3A is a schematic cross-sectional view of a stack 304 that may be processed according to some embodiments, where the stack is under a mask 312, such as a carbon containing mask, such as photoresist or amorphous carbon. In some embodiments, the stack 304 may be formed over a substrate 308.The stack 304 may comprise at least one silicon layer 316. In some embodiments, the stack further comprises at least one silicon containing layer 320 comprising at least one of SiO2, SiN, and SiGe. In some embodiments, the stack is a plurality of layers. In some embodiments, the stack is a plurality of bilayers, trilayers, or more multiple layers. In some embodiments, one or more layers may be between the mask 312 and the stack 304. In some embodiments, one or more layers may be between the substrate 308 and the stack 304.

[0061] In some embodiments, a break through step may be provided to remove or break through a native oxide layer on the stack 304. Such a break through may be accomplished before transferring the stack to the etch chamber or may be performed in the etch chamber.

[0062] In some embodiments, the chamber pressure is set to a set or predetermined pressure (step 291). In some embodiments, the set pressure is in the range of 20 millitorr (mTorr) to 9000 mTorr. In some embodiments, the set pressure is in the range of 500 mTorr to 4000 mTorr. In some embodiments, setting the pressure is an optional step. In some embodiments, the pressure is set during a subsequent step.

[0063] In some embodiments, the substrate support is heated to a set temperature (step 292). In some embodiments, the substrate support is heated to a temperature in the range of -40° C to 500° C. In some embodiments, the substrate support is heated to a temperature in the range of 40° C to 130° C. In some embodiments, the etching may be provided at room temperature, so that heating is not needed.

[0064] An etchant gas and radicalizer gas are flowed into the chamber. In some embodiments, the etchant gas comprises a halogen containing component. In some embodiments, the halogen containing component comprises at least one of fluorine (F2), CIF3, xenon difluoride (Xe t), interhalogens, chlorine fluoride (C1F), sulfur hexafluoride (SFe), nitrogen trifluoride (NF3), and hydrogen fluoride (HF). In some embodiments, the interhalogens comprise bromine trifluoride (BrF3), bromine pentafluoride (BrFs), and iodine pentafluoride (IF5). In some embodiments, the radicalizer comprises at least one of nitric oxide (NO), nitrogen dioxide (NO2), ozone (O3), chlorine dioxide (CIO2), hypochlorous acid (HOC1), hydrogen peroxide (H2O2), hypobromous acid (HOBr), chlorine trifluoride (CIF3), tert-Butyl hydroperoxide (TBHP), and other groups of chemicals including but not limited to interhalogens, polymer initiators, and other liquid / vapor phase free radicals. In some embodiments, an additional combination of additives may also be provided. The combination of a component additives may comprise at least one of ammonia (NH3), hydrogen (H2), methane (CH4), oxygen (O2), ozone (O3), chlorine (Ch), hydrogen fluoride (HF), nitrogen (N2), nitrous oxide (N2O), nitrogen dioxide (NO2), boron trichloride(BCh), silicon tetrachloride (SiCh), hydrogen bromide (HBr), hydrogen chloride (HC1), hydrogen iodide (HI), water (H2O), bromine (Br ), and fluorocarbons, such as hexafluoro methane (CzFe). In some embodiments, the radicalizer gas is different from the etchant gas, so that when the radicalizer gas is mixed with the etchant gas the radicalizer gas causes the etchant gas to form radicals, by processes such as oxidation, reduction, or dissociation. In some embodiments, an inert carrier gas may also be used to help with flow control. In some embodiments, the inert carrier gas is one or more of argon (Ar), nitrogen (N2), and helium (He).

[0065] The radicalizer gas causes the etch gas to form halogen radicals. The halogen radicals selectively laterally etch at least one silicon layer 316 with respect to the at least one silicon containing layer 320 comprising at least one of SiOz, SiN, and SiGe. FIG. 3B is a schematic cross-sectional view of a stack 304 after the at least one silicon layer 316 has been etched with respect to the at least one silicon containing layer 320 comprising at least one of SiCF, SiN, and SiGe.

[0066] In some embodiments, the etch process leaves a residue on the stack 304. A post treatment process may be provided to remove any residue (step 294). A fluorine-based gas or plasma may be used to remove an oxide residue. The stack 304 is then removed from the chamber (step 295).

[0067] The selectivity of the lateral etch of the silicon with respect to at least one of comprising at least one of SiOz, SiN, and SiGe, the etch rate, and the uniformity of the etch rate between the top of the stack and the bottom of the stack is controlled by one or more of the pressure, the temperature of the substrate support, the ratio of the etch gas and the radicalizer gas, and the additive. In addition, some embodiments may add a plasma before, after, or during providing the etch gas and the radicalizer to further improve selectivity, the etch rate, and the uniformity. Generally, the etchant and the radicalizer are provided simultaneously, so that the radicalizer may form radicals of the etchant. In some embodiments, the radicalizer and etchant are mixed in the chamber. In some embodiments, the radicalizer and etchant are mixed before reaching the chamber.

[0068] FIG. 3C is a schematic cross-sectional view of a stack 304 after the at least one silicon layer 316 has been etched with respect to the at least one silicon containing layer 320 comprising at least one of SiOz, SiN, and SiGe using only a plasma etch without using a radicalizer to provide thermal radical etching. FIG. 3C illustrates how a plasma only lateral etch may provide more of a lateral etch near the top of the stack, but further down the stack, the lateral etch decreases until there is almost no lateral etch near the bottom of the stack.

[0069] FIG. 3D is a schematic cross-sectional view of a stack 304 after the at least one silicon layer 316 has been etched with respect to the at least one silicon containing layer 320 comprising at least one of SiOz, SiN, and SiGe using a thermal etch process with only an etchant and a radicalizer and optionally a carrier gas and where the flow of the radicalizer is less than the flow of the etchant, by flow rate of standard cubic centimeters per minute (seem). In some embodiments, the ratio of the flow of the etchant to the flow of the radicalizer is in the range from 100:1 to 2:1. The lateral etch from top to bottom of the stack 304 is more uniform than the lateral etch by plasma only. However, the etch rate is slow being indicated by showing that only a small amount was laterally etched.

[0070] FIG. 3E is a schematic cross-sectional view of a stack 304 after the at least one silicon layer 316 has been etched with respect to the at least one silicon containing layer 320 comprising at least one of SiOz, SiN, and SiGe using a thermal etch process with only an etchant and a radicalizer and optionally a carrier gas and where the flow of the radicalizer is greater than the flow of the etchant, by seem. In some embodiments, the ratio of the flow of the etchant to the flow of the radicalizer is in the range from 1:1 to 1:100. The lateral etch from top to bottom of the stack 304 is slightly tapered where there is more lateral etch near the top of the stack than the bottom of the stack. However, the etch rate is faster than the thermal etch where the flow of the radicalizer is less than the flow of the etchant by volume.

[0071] The addition of additives and possibly a plasma etch provides a faster and more uniform lateral etch, as shown in FIG. 3B. In some embodiments, the chemical additive can play a variety of roles, ranging from radical quencher to modifying the degree of etch radical character, surface passivation, or even etch front control. Additionally, the use of an additive can normalize uneven etch rates due to material impurities, the presence of grain boundaries, and crystalline faceting. Chemical additives may be coflowed or intermittently exposed by cycling flows. Ultimately, the degree of radical characteristic can be tuned through the modulation of the ratio between the radicalizer, etchant, and additive, thus enabling tunable top to bottom lateral etch control over Si recess. In some embodiments, the additive may be used to help achieve a surface reaction limited regime through modulation of the concentration of the etch species. By moving from a mass transport limited regime to a surface reaction limited regime, an additive will help to provide a uniform lateral etch from top to bottom.

[0072] A thermal radical etch process, as defined in the present specification and claims, uses combining an etchant with a radicalizer, where the radicalizer is able to create radicals from the etchant without requiring a plasma. Therefore, chemical interactions, instead of plasma, are usedto initiate dissociation into radical species. In some embodiments, thermal heat is also added in the creation of the radicals. In some embodiments, thermal heat is not used. The resulting radicals have a lower energy distribution than radicals generated from a traditional plasma source, so that there is more control over the energy of the radicals and the radicals can be more easily tuned.

[0073] In some embodiments, it has been found that using an etchant of at least one of F2, CIF3, C1F, and NF3. with a radicalizer of at least one of NO, NO2, O3, and H2O2, a carrier gas of at least one of Ar, He, and N2, and an additive of at least one of NH3, H2, and O2 provides a uniform lateral etch with an increased etch rate without using a plasma and therefore is plasma free. In some embodiments, a temperature in the range of 40° C to 130° C is used to selectively etch Si.

[0074] In some embodiments, the method is used for forming 3D-NAND and 3D DRAM. The recessed silicon is used to grow layers of a material.

[0075] In some embodiments, the concentration of halogen radicals is tuned. In some embodiments, the concentration of halogen radicals is tuned by the amount of time that the radicalizer or additive is mixed with the halogen to provide a desired etch aggressiveness, etch rate, and relative top and bottom etch rates. FIG. 4A is a schematic view of a substrate processing chamber 400 that is used in an embodiment of the substrate processing chamber 200, shown in FIG. IB. A radicalizer gas source 460, a diluent gas source 464, an additive gas source 468, and a halogen gas source 472 provide gas to a mixing manifold 458. Gas is fed from the mixing manifold 458 to a gas injector 442. The gas injector 442 provides gas to an upper chamber 404 where the gas may be formed into a plasma. The gas or plasma is flowed from the upper chamber 404 to the lower chamber region 402 through the gas distribution device 414. The substrate 426 is supported in the lower chamber region 402 by the substrate support 422.

[0076] FIG. 4B is a schematic view of a substrate processing chamber 400 that is used in another embodiment of the substrate processing chamber 200, shown in FIG. IB. A radicalizer gas source 460, a diluent gas source 464, and an additive gas source 468 provide gas to a mixing manifold 458. Gas is fed from the mixing manifold 458 to a gas injector 442. A halogen gas source 472 feeds gas directly to the gas injector 442 without flowing through the mixing manifold 458. As a result, the radicalizer gas from the radicalizer gas source 460 is mixed with the halogen gas from the halogen gas source 472 for a shorter time period than they are mixed in the embodiment shown in FIG. 4A. The gas injector 442 provides gas to an upper chamber 404 where the gas may be formed into a plasma. The gas or plasma is flowed from the upperchamber 404 to the lower chamber region 402 through the gas distribution device 414. The substrate 426 is supported in the lower chamber region 402 by the substrate support 422.

[0077] FIG. 5 is a schematic cross-sectional view of features that were etched in a stack 504 below a mask 512 by the processing chamber 400, shown in FIG. 4A that mixes the radicalizer with a halogen containing component in the mixing manifold, allowing a tuning that mixes the radicalizer with the halogen containing component for a longer period of time. In some embodiments, the silicon 516a near the top of the features is laterally etched about the same as the silicon 516b near the middle of the features and the silicon 516c near the bottom of the features.

[0078] FIG. 6 is a schematic cross-sectional view of features etched in a stack 604 below a mask 612 by the processing chamber 400, shown in FIG. 4B that does not mix the radicalizer with a halogen containing component until they enter the gas injector 442, allowing a tuning that mixes the radicalizer with the halogen containing component for a shorter period of time and where all other parameters are the same as the process resulting in FIG. 5. In some embodiments, the silicon 616a near the top of the features is laterally significantly etched more than the silicon 616b near the middle of the features and the silicon 616c near the bottom of the features.

[0079] Without being bound by theory, it is believed that when the radicalizer and halogen containing component are mixed and form halogen radicals, over time the number or concentration of halogen radicals decreases as some of the halogen radicals become non-radical molecules. A sufficiently low concentration of halogen radicals results in a more uniform top to bottom lateral etch, resulting in features shown in FIG. 5. If the concentration of halogen radicals is too high, then the top of the features are laterally etched more than the bottom of the features, resulting in features shown in FIG. 6. If the concentration of halogen radicals is too low, then the lateral etch rate becomes too slow. In other embodiments, other tuning methods may be used to tune the concentration of halogen radicals. For example, the flow of inert carrier gas may be increased in order to decrease the concentration of the halogen radicals. In various embodiments, the concentration of the halogen radicals is tuned to provide a more uniform etch. In some embodiments, more etching at the top may be desired. In such embodiments, a tuning may be provided to increase the concentration of halogen radicals. In some embodiments, the concentration of halogen radicals can be changed by changing the concentration of the radicalizer or the concentration of the halogen containing gas. The concentration of the radicalizer or the concentration of the halogen containing gas may be tuned by changing theflow rate of the radicalizer or halogen containing gas or a diluent or a radical quenching additive. In some embodiments, the tuning by delaying the mixing time or lowering the concentration of radicalizer or halogen containing gas causes the formation of halogen radicals near the bottom of the features, providing a more uniform etch. This allows more halogen radicals near the bottom of the features, whereas if the halogen radicals are formed further away, by the time the halogen radicals reach the bottom of the features they may become non-radicals.

[0080] FIG. 7 is a high level block diagram illustrating a computer system 700 for implementing the controller 160 used in embodiments. The computer system may have many physical forms ranging from an integrated circuit, a printed circuit board, and a small handheld device up to a huge supercomputer. The computer system 700 may include one or more processors 702 and further can include an electronic display device 704 (for displaying graphics, text, and other data), a main memory 706 (e.g., random access memory (RAM)), storage device 708 (e.g., hard disk drive), removable storage device 710 (e.g., optical disk drive), user interface devices 712 (e.g., keyboards, touch screens, keypads, mice or other pointing devices, etc.), and / or a communication interface 714 (e.g. , wireless network interface). The communication interface 714 may allow software and / or data to be transferred between the computer system 700 and external devices via a link. The system may also include a communications infrastructure 716 (e.g., a communications bus, cross-over bar, or network) to which the aforementioned devices / modules may be connected.

[0081] Information transferred via communications interface 714 may be in the form of signals such as electronic, electromagnetic, optical, or other signals capable of being received by communications interface 714, via a communication link that carries signals and may be implemented using wire or cable, fiber optics, a phone line, a cellular phone link, a radio frequency link, and / or other communication channels. With such a communications interface, it is contemplated that the one or more processors 702 might receive information from a network or might output information to the network in the course of performing the above-described method steps. Furthermore, method embodiments may execute solely upon the processors or may execute over a network such as the Internet in conjunction with remote processors that share a portion of the processing.

[0082] The term “non-transient computer readable medium” is used generally to refer to media such as main memory, secondary memory, removable storage, and storage devices, such as hard disks, flash memory, disk drive memory, CD-ROM, and other forms of persistent memory and shall not be construed to cover transitory subject matter, such as carrier waves orsignals. Examples of computer code include machine code, such as produced by a compiler, and files containing higher level code that are executed by a computer using an interpreter.Computer readable media may also be computer code transmitted by a computer data signal embodied in a carrier wave and representing a sequence of instructions that are executable by a processor.

[0083] In some embodiments, the controller 160 is configured to provide a halogen containing component from the halogen containing component source and provide a radicalizer gas from the radicalizer gas source. In some embodiments, the controller 160 is further configured to provide a carrier gas of argon and an additive gas of at least one of NH3, H2, and O2. In some embodiments, the controller 160 is further configured to heat the substrate support to a temperature in a range of 40° C to 130° C. In some embodiments, the controller 160 is configured to provide a pressure in a range of 20 mTorr to 9000 mTorr.

[0084] In some embodiments, an endpoint measurement device may be used to determine the endpoint of an etch. An endpoint measurement device may comprise an interferometer for measuring the depth of an etch or a spectrometer that detects an endpoint indicator species or species concentration.

[0085] While this disclosure has been described in terms of several preferred embodiments, there are alterations, modifications, permutations, and various substitute equivalents, which fall within the scope of this disclosure. It should also be noted that there are many alternative ways of implementing the methods and apparatuses of the present disclosure. It is therefore intended that the following appended claims be interpreted as including all such alterations, modifications, permutations, and various substitute equivalents as fall within the true spirit and scope of the present disclosure. As used herein, the phrase “A, B, or C” should be construed to mean a logical (“A OR B OR C”), using a non-exclusive logical “OR,” and should not be construed to mean ‘only one of A or B or C. Each step within a process may be an optional step and is not required. Different embodiments may have one or more steps removed or may provide steps in a different order. In addition, various embodiments may provide different steps simultaneously instead of sequentially.

Claims

CLAIMSWhat is claimed is:

1. A method for selectively etching silicon with respect to at least one of a silicon oxide, silicon nitride, and silicon germanium containing layer in a stack, comprising: providing an etchant gas comprising a halogen containing component; providing a radicalizer gas, wherein the radicalizer gas causes the halogen containing component to provide halogen radicals without providing a plasma; and exposing the stack to the halogen radicals causing the silicon to be selectively etched.

2. The method, as recited in claim 1, wherein the radicalizer gas comprises at least one of nitric oxide (NO), nitrogen dioxide (NO2), ozone (O3), chlorine dioxide (CIO2), hypochlorous acid (HOC1), hydrogen peroxide (H2O2), hypobromous acid (HOBr), chlorine trifluoride (CIF3), and tert-Butyl hydroperoxide (TBHP).

3. The method, as recited in claim 1, further comprising providing an additive gas comprising at least one of ammonia (NH3), hydrogen (H2), methane (CH4), oxygen (O2), ozone (O3), chlorine (CI2), hydrogen fluoride (HF), nitrogen (N2), nitrous oxide (N2O), nitrogen dioxide (NO2), boron trichloride (BCI3), silicon tetrachloride (SiCL), hydrogen bromide (HBr), hydrogen chloride (HC1), hydrogen iodide (HI), water (H2O), bromine (Br2), and a fluorocarbon.

4. The method, as recited in claim 1, wherein the radicalizer gas comprises at least one of nitrous oxide, nitrogen dioxide, hydrogen peroxide, and ozone.

5. The method, as recited in claim 1, the halogen containing component comprises at least one of fluorine (F2), CIF3, xenon difluoride ( XeFi), interhalogens, and chlorine fluoride (C1F), sulfur hexafluoride (SFe), nitrogen trifluoride (NF3), and hydrogen fluoride (HF).

6. The method, as recited in claim 1, wherein the etchant gas further comprises a carrier gas.

7. The method, as recited in claim 6, wherein the carrier gas comprises at least one of argon, helium, and nitrogen.

8. The method, as recited in claim 1, wherein the etchant gas further comprises a carrier gas of at least one of argon, helium, and nitrogen, wherein the halogen containing component comprises at least one of F2, CIF3, C1F, and NF3, and wherein the radicalizer gas comprises at least one of NO, NO2, O3, and H2O2.

9. The method, as recited in claim 8, further comprising: placing the stack on a substrate support; and heating the substrate support to a temperature in a range of 90° C to 120° C.

10. The method, as recited in claim 8, further comprising providing an additive gas, wherein the additive gas comprises at least one of NH3, H2, CH4, O2, O3, CI2, HF, N2, N2O, NO2, BCI3, SiCH, HBr, HC1, HI, H2O, Bt2, and fluorocarbons.

11. The method, as recited in claim 1, further comprising: placing the stack on a substrate support; and heating the substrate support to a temperature in a range of 90° C to 120° C.

12. The method, as recited in claim 1, further comprising providing a pressure in a range of 20 mTorr to 9000 mTorr.

13. The method, as recited in claim 1, further comprising tuning a concentration of halogen radicals to which the stack is exposed.

14. The method, as recited in claim 13, wherein the tuning the concentration of halogen radicals comprises at least one of tuning a mixing time of the radicalizer gas and halogen containing component, tuning a concentration of the radicalizer gas, and tuning a concentration of the halogen containing component.

15. An apparatus for selectively etching silicon with respect to at least one of silicon germanium, silicon oxide, and silicon nitride in a stack, the apparatus comprising: a. a substrate support configured to support the stack in a chamber; b. a halogen containing component source for providing a halogen containing component to the chamber; c. a radicalizer gas source for providing a radicalizer gas to the chamber; d. a heater for heating the substrate support; e. a pump for removing vapor from the chamber; and f. a controller controllably connected to the heater, the halogen containing component source, and the radicalizer gas source, configured to: provide a halogen containing component from the halogen containing component source; and provide a radicalizer gas from the radicalizer gas source.

16. The apparatus, as recited in claim 15, further comprising a mixing manifold, wherein one of the halogen containing component source and radicalizer gas source is connected to the mixing manifold and one of the halogen containing component source and radicalizer gas source is not connected to the mixing manifold.

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