Plasma processing method and apparatus

Abstract

An embodiment plasma processing apparatus includes: a plasma generating source; a nozzle in the plasma chamber capable of directing plasma from a plasma generating source to a wafer to be processed, the plasma being in the form of a plasma beam at an outlet of the nozzle; a gas shield disposed in the plasma chamber and over the wafer, the gas shield including a first circular opening in a top surface of the gas shield, a second circular opening in a bottommost surface of the gas shield, and a gas chamber in which the nozzle is disposed, the gas plenum is configured to be maintained at a first pressure, a first region between the second circular opening and the top surface of the wafer is configured to be maintained at a second pressure, the first pressure and the second pressure being different.

Description

[0001] Cross Reference to Related Patents and Applications

[0002] This application claims priority to and the benefit of the filing date of U.S. Non-Provisional Patent Application No. 18 / 350,519 filed July 11, 2023, which is incorporated by reference herein in its entirety. TECHNICAL FIELD

[0003] The present invention relates generally to plasma processing, and in particular embodiments, to plasma processing methods and apparatus. BACKGROUND

[0004] Semiconductor manufacturing processes can involve various manufacturing techniques, including forming, patterning, and removing multiple layers on a substrate. Plasma processes are commonly used in various steps of semiconductor manufacturing processes. For example, reactive ion etching (RIE), plasma enhanced CVD (PECVD), and plasma enhanced atomic layer deposition (PEALD) are common process steps in semiconductor device manufacturing.

[0005] Semiconductor wafer die manufacturing processes can include film etching processes during pattern transfer. Such processes can encounter a number of problems that impact wafer die yield, productivity, reliability, and cost. Such problems can become more prevalent as patterns become smaller and tolerances are more limited. In plasma manufacturing processes, problems can arise due to wafer and film thickness non-uniformity. For example, a wafer thickness toward a center of the wafer can be less than at an edge of the wafer. There is therefore a need to be able to controllably etch different regions of a wafer to allow for thickness differences between different regions of the wafer.

[0006] Local or partial plasma etching can be used to remove material in a first region of a wafer using plasma, while leaving material in other surrounding regions of the wafer. As plasma processes in the semiconductor industry continue to evolve, there is a need to improve existing plasma etching processes. These improvements are needed to reduce etch damage caused by unused etching radicals during local or partial plasma etching, and to reduce contamination of surrounding regions of the wafer by etch byproducts and unreacted neutrals. Improvements are also needed to allow for better control of etching across a wafer surface, thereby improving uniformity across the wafer. SUMMARY

[0007] According to an embodiment, a plasma processing apparatus includes: a plasma generation source; a nozzle in a plasma chamber, the nozzle being capable of directing plasma from the plasma generation source to a wafer to be processed, the plasma assuming the form of a plasma beam at an exit of the nozzle; a gas shroud disposed in the plasma chamber and above the wafer, the gas shroud encircling the nozzle, the gas shroud including a first circular opening in a top surface of the gas shroud, a second circular opening in a bottom most surface of the gas shroud, and a gas plenum, the nozzle being disposed in the first circular opening and the second circular opening, the gas plenum being configured to be maintained at a first pressure, a first region between the second circular opening and a top surface of the wafer being configured to be maintained at a second pressure, the first pressure and the second pressure being different.

[0008] According to an embodiment, a plasma processing method includes: generating plasma from a plasma source; directing the plasma into a processing chamber and to an outer surface of a wafer using a vertical nozzle, the plasma exiting at an end of the vertical nozzle disposed above the outer surface of the wafer, the plasma exiting in the form of a plasma beam, the vertical nozzle extending through a gas shroud encircling the vertical nozzle and disposed above the wafer, the plasma beam being disposed in a first region, the first region including a space between an opening in a bottom most surface of the gas shroud and the outer surface of the wafer; supplying an inert gas to a gas plenum of the gas shroud to maintain a first pressure in the gas plenum; and distributing the inert gas from the gas plenum to the first region to maintain a second pressure in the first region, the first pressure being higher than the second pressure.

[0009] According to an embodiment, an apparatus includes: a radical source; a nozzle configured to deliver radicals from the radical source into a processing chamber; a gas shroud disposed in the processing chamber above a wafer to be processed, the gas shroud including a first opening in a top most surface of the gas shroud, a second opening in a bottom most surface of the gas shroud, a gas plenum, and a first orifice arranged in an annular pattern around the second opening, a first region being disposed between the second opening and a top surface of the wafer, the first orifice acting as a conduit for gas flow between the gas plenum and the first region, an exit of the nozzle being disposed in the first region and above the wafer, the nozzle extending through the first opening, the second opening, and the gas shroud.

[0010] The foregoing has outlined rather broadly the features and technical advantages of the present disclosure in order that the detailed description of the present disclosure that follows can be better understood. Additional features and advantages of the present disclosure will be described below, which form the subject of the claims of the present disclosure. It should be appreciated by those skilled in the art that the conception and specific embodiments disclosed can be readily utilized as a basis for modifying or designing other structures or processes for carrying out the same purposes of the present disclosure. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the present disclosure as set forth in the appended claims. BRIEF DESCRIPTION OF DRAWINGS

[0011] For a more complete understanding of the present disclosure and its advantages, reference is now made to the following description taken in conjunction with the accompanying drawings in which:

[0012] Figure 1 A block diagram of a plasma processing system is shown in accordance with various embodiments of the present disclosure;

[0013] Figure 2 A block diagram of a plasma processing system is shown in accordance with various embodiments of the present disclosure; Figure 1 A cross-sectional view of a gas shield of the plasma processing system is shown;

[0014] Figure 3A and Figure 3B A cross-sectional view of a gas shield of the plasma processing system is shown; Figure 2 A cross-sectional view of a gas shield of the plasma processing system is shown;

[0015] Figure 4A A top view of a plasma processing tool is shown in accordance with various embodiments of the present disclosure;

[0016] Figure 4B A cross-sectional view of a gas shield of the plasma processing system is shown; Figure 4A A cross-sectional view of a gas shield of the plasma processing system is shown; and

[0017] Figure 5 A flow diagram of a method of using a plasma processing system and plasma processing tool application is shown in accordance with various embodiments of the present disclosure; Figures 1 to 4B

[0018] Unless otherwise indicated, corresponding numbers and symbols in different figures generally refer to corresponding parts. The figures are drawn to illustrate relevant aspects of various embodiments clearly, and the figures are not necessarily drawn to scale. DETAILED DESCRIPTION

[0019] ​The manufacture and use of the currently preferred embodiments will now be discussed in detail below. It should be appreciated, however, that the present disclosure provides many applicable creative concepts that can be embodied in a wide variety of specific contexts. The specific embodiments discussed are merely illustrative of specific ways to make and use the disclosure and do not limit the scope of the disclosure.

[0020] The present disclosure will be described in connection with preferred embodiments in a specific context, namely in an apparatus and method for local or partial plasma etching, which includes a nozzle directing plasma and radicals from a plasma source towards a wafer to be etched. The plasma and radicals are directed at the nozzle outlet in the form of a plasma beam (also referred to as plume hereinafter). The wafer to be etched and the nozzle outlet are located in a plasma chamber. The apparatus and method further include a gas shroud for generating a sonic flow in a first region between a base of the gas shroud and a top surface of the wafer being etched (e.g. using a jet of inert gas travelling at the speed of sound). The nozzle is mounted within the shroud. The sonic flow can be used to control the pressure in the first region and allows a pressure differential to be maintained between the first region and other regions within the plasma chamber. The lateral width of the plasma plume at the nozzle outlet depends on the pressure in the first region and since the pressure in the first region depends on the flow rate of the sonic flow of the gas shroud, the lateral width of the plasma plume can be controlled using appropriate gas shroud design choices. The lateral width is the width between the outermost points of the plasma plume that physically contact the top surface of the wafer. The plasma plume can be concentrated on a small area of the wafer surface directly below the nozzle (e.g. the plasma plume has a small etch spot size) and the amount of material to be etched from the wafer can be controlled. The sonic flow from the gas shroud directs etch by-products, unused radicals and unreacted neutrals from the plasma upwards through the shroud and out of the plasma chamber. In addition, the sonic flow separates the first region from surrounding regions and prevents the etch by-products, unused radicals and unreacted neutrals from coming into contact with undesired etched surfaces of the wafer in these surrounding regions.

[0021] Advantages can be realized by using a gas shroud to create a sonic flow in the first region in order to maintain pressure in the first region. This includes the ability to control the lateral width of the plasma plume, resulting in better etch control, improved concentration of the plasma plume, and better etch spot size control. As a result, this will allow for high resolution etching and achieve better uniformity across the surface of the wafer. Further advantages are realized by the sonic flow directing etch byproducts, unused radicals, and unreacted neutrals from the plasma up through the shroud and out of the plasma chamber, and by the sonic flow separating the first region from the surrounding regions to prevent the etch byproducts, unused radicals, and unreacted neutrals from coming into contact with the surface of the wafer in these surrounding regions. These advantages include reducing accidental etch damage by unused etch radicals during partial plasma etching, and reducing contamination of the surrounding regions of the wafer by etch byproducts and unreacted neutrals. Various embodiments will be explained in detail in the following with reference to the drawings.

[0022] Figure 1 A schematic cross-sectional view of an example of a plasma processing system 100 according to the techniques described herein is shown. Depending on the implementation, the plasma processing system 100 can be a capacitively coupled plasma (CCP) processing system, an inductively coupled plasma (ICP) processing system, a microwave generated plasma system, etc. The use of the example plasma processing system 100 is described subsequently in the context of an etching operation. However, aspects of the embodiments described herein can be used for other plasma operations, including ashing, deposition, cleaning, plasma polymerization, plasma enhanced chemical vapor deposition (PECVD), plasma enhanced atomic layer deposition (PEALD), etc. The plasma processing can be performed within a plasma processing chamber 114, which can be a vacuum chamber made of a metal such as aluminum or stainless steel.

[0023] A microwave generator 104 generates electromagnetic waves (microwaves) that are distributed to a plasma source 106, in which a plasma is generated. In other embodiments, the frequency of the electromagnetic wave source can range from tens of MHz (e.g., radio frequency (RF)) to 1-30 GHz (microwave). The plasma source 106 is disposed above the plasma processing chamber 114 and can include a plasma cavity and plasma elements for generating a plasma in the plasma cavity. In embodiments, the plasma source 106 can be a remote plasma source disposed in a different location, where the plasma is directed to the surface to be etched after generation. The plasma elements can generate a mixture of plasma and radicals, which is then flowed through a nozzle 108 into the plasma processing chamber 114. Thus, the plasma is generated outside of the plasma processing chamber 114 and then introduced into the plasma processing chamber using a gas flow.

[0024] A process gas is introduced into a plasma cavity of the plasma source 106, where it is ionized and excited by the plasma. This gas can be a mixture of one or more reactive gases (such as oxygen, nitrogen, hydrogen, fluorine, etc.), depending on the particular process being performed. In embodiments, the process gas can be a fluorine-rich precursor, such as NF3, SF6, etc. The process gas is supplied using a process gas supply 118 and introduced into the plasma cavity through a gas inlet. The process gas can be mixed with a carrier gas (such as argon or helium) to ensure uniform distribution and stable plasma operation. The gas mixture is then excited by the plasma, which dissociates the gas molecules into reactive species, such as radicals, ions, or excited molecules.

[0025] The plasma and radicals generated in the plasma source 106 then flow through the vertical nozzle 108 into the plasma processing chamber 114, with the outlet of the nozzle 108 positioned above a wafer support 117 (e.g., a wafer chuck, etc.) in the plasma processing chamber 114. The wafer support 117 is configured to hold a wafer 126 (or e.g., a substrate, etc.) to be etched, such that the radicals and plasma are ejected from the outlet of the nozzle 108 toward a top surface of the wafer 126. The plasma and radicals are directed at the top surface of the wafer 126 in the form of a plasma plume 112 (also referred to as a plasma beam) at the outlet of the nozzle 108. The plasma plume 112 comprises a narrow column or beam of plasma and radicals. However, as the plasma plume 112 travels away from the outlet of the nozzle 108 (e.g., in a vertically downward direction), the plasma plume 112 has a tendency to widen or diverge, and spread over a larger area as it encounters the underlying wafer 126. It is desirable for the plasma plume 112 to be more concentrated over a smaller area of the surface of the wafer 126 (e.g., the plasma plume 112 has a smaller etch spot size), so that the amount of material to be etched from the wafer 126 during the etching process can be controlled.

[0026] The plasma processing system 100 can include a gas shroud 110 for controlling the lateral width of the plasma plume 112 and allowing the plasma plume 112 to be focused on a smaller area of the surface of the wafer 126 (e.g., by reducing the lateral width of the plasma plume 112). The lateral width can be the width between the outermost points of the plasma plume 112 that are in physical contact with the top surface of the wafer 126. The gas shroud 110 is disposed in the plasma processing chamber 114 above the wafer support 117 and the wafer 126. The gas shroud 110 has a circular shape when viewed in a top view and has a first opening in the topmost surface of the gas shroud 110 and a second opening in the bottommost surface of the gas shroud 110. The first opening has a circular shape and is disposed at the center of the top surface of the gas shroud 110 when viewed in a top view. The cylindrical nozzle 108 is fitted through the first and second openings such that the gas shroud 110 encircles the vertical sidewalls of the nozzle 108 and the fit between the nozzle 108 and the top surface of the gas shroud 110 is sealed with respect to the gas.

[0027] The gas shroud 110 includes a gas plenum 116 designed to create an inward sonic flow 119 (e.g., formed by a jet of inert gas flowing at a speed equal to the speed of sound) in a first region between the base of the gas shroud 110 and the wafer 126. The plasma plume 112 and the outlet of the nozzle 108 are disposed within this first region. The sonic flow 119 of the gas shroud 110 can be used to maintain the pressure within the first region and, since the lateral width of the plasma plume 112 depends on the pressure within the first region, the lateral width of the plasma plume 112 can be controlled. The sonic flow is generated from an inert gas supplied by an inert gas supply 124 to the gas plenum 116. The inert gas can include argon, nitrogen, etc. The gas plenum 116 then distributes this inert gas uniformly into the first region through a series of small orifices or channels in the base of the gas shroud 110 to form the sonic flow 119. The gas shroud 110 is connected with a vacuum pump 120 for removing etching byproducts, unused radicals, and unreacted neutrals from the plasma plume 112 by moving them upward through the gas shroud 110 and out of the plasma processing chamber 114 through a gas outlet.

[0028] During an etching process using the plasma processing system 100, the wafer 126 can be moved or scanned underneath the plasma plume 112 in order to etch material from the wafer 126. Alternatively, the combination of the nozzle 108 and the gas shroud 110 can be scanned across the surface of the wafer 126 during the etching process. The wafer scan speed and dwell time during the etching process can be controlled to control the uniformity across the wafer 126 and allow for a uniform etch to be achieved across the entire surface of the wafer 126.

[0029] A vacuum pump 122 is connected to the plasma processing chamber 114 through a gas outlet, and the vacuum pump 122 helps maintain a desired pressure in the region 115 of the plasma processing chamber 114.

[0030] Figure 2 A cross-sectional view of the gas shield 110 is shown. The gas shield 110 is shown disposed above a wafer 126. In particular, the gas shield is disposed above a region of the wafer 126 that is to be etched. The gas shield 110 can comprise a material such as aluminum oxide (AI2O3), aluminum, or the like. In some embodiments, the gas shield comprises a material that is resistant to the etchant of the particular etching process being performed. It should be noted that although the gas shield 110 and the nozzle 108 are described as being used in the context of an etching process, the embodiments described herein, including the gas shield 110 and the nozzle 108, can also be used in the context of other types of plasma operations. These operations include ashing, deposition, cleaning, plasma polymerization, plasma-enhanced chemical vapor deposition (PECVD), plasma-enhanced atomic layer deposition (PEALD), and the like.

[0031] As shown, in various embodiments, the gas shield 110 has a circular shape in a top view and has a circular opening 123a on a top-most surface of the gas shield 110 and a circular opening 123b at a bottom-most surface of the gas shield 110. The diameter of the opening 123b can be larger than the diameter of the opening 123a, and the opening 123a can overlap and connect with the opening 123b. In a top view, the opening 123a is disposed at the center of the top surface of the gas shield 110. The nozzle 108 (previously described in Figure 1 the nozzle 108 can have a cylindrical shape and can be mounted into the opening 123a and the opening 123b in the gas shield 110 such that the gas shield 110 encircles the vertical sidewalls of the nozzle 108, and the fit between the nozzle 108 and the top surface of the gas shield 110 is sealed with respect to the gas. In this way, the nozzle 108 can extend into the openings 123a and 123b and extend through the gas shield 110. The nozzle 108 can comprise aluminum oxide (AI2O3) or the like. The gas shield 110 comprises a closed space having interconnected sections of different sizes. For example, the gas shield 110 can comprise a first section 129, a second section 130, and a third section 131 arranged in a concentric manner, with the third section 131 disposed above the second section 130, and the second section 130 disposed above the first section 129. Gas can flow from one of these sections (e.g., the first section 129, the second section 130, or the third section 131) to the other sections, and the flow direction and the gas flow rate will depend on the pressure difference between the sections.

[0032] Each of the first section 129, the second section 130, and the third section 131 includes an annular (e.g., ring-like structure with a space in the middle) structure. The first section 129 has a first inner diameter D1 between first inner sidewalls of the first section 129. The second section 130 has a second inner diameter D2 between second inner sidewalls of the second section 130. The third section 131 has a third inner diameter D3 between third inner sidewalls of the third section 131. In embodiments, the third inner diameter D3 is greater than the second inner diameter D2, and the second inner diameter D2 is greater than the first inner diameter D1.

[0033] The opening 123b of the gas shroud 110 is disposed vertically below the first section 129. The opening 123b includes a first space disposed between sidewalls of a base of the gas shroud 110. The first region 128 includes a combination of the first space of the opening 123b and a second space disposed vertically below and overlapping the opening 123b, the second space being between the opening 123b and a top surface of the wafer 126.

[0034] The nozzle 108 (shown in Figure 1 and Figure 3A ) can be mounted to be disposed within the gas shroud 110, in the opening 123a and the opening 123b. An axis (also referred to as a length, subsequently) of the nozzle 108 can extend completely through the third section 131, the second section 130, and the first section 129. In embodiments, the axis of the nozzle 108 extends completely through the third section 131 and the second section 130, and only partially through the first section 129. In embodiments, the axis of the nozzle 108 extends completely through the third section 131, the second section 130, and the first section 129, and only partially through the first region 128. An outlet of the nozzle 108 is disposed in the first region 128, above the surface of the wafer 126. During an etching process that etches material from the wafer 126 in the first region 128, radicals and plasma are ejected from the outlet of the nozzle 108 in the form of a plasma plume 112 (previously described in Figure 1 ) toward the top surface of the wafer 126 in the first region 128. The plasma plume 112 travels away from the outlet of the nozzle 108 (e.g., in a vertically downward direction) and through the first region 128 until it encounters the top surface of the wafer 126 to be etched.

[0035] The gas shroud 110 also includes a gas plenum 116. The gas plenum 116 is a volume or chamber that surrounds the first section 129 along the perimeter of the first section 129. There is no direct connection or passageway for gas flow between the gas plenum 116 and the first section 129. In embodiments, the gas plenum 116 also surrounds a lower portion of the second section 130 along the perimeter of the second section 130. There is no direct connection or passageway for gas flow between the gas plenum 116 and the second section 130. The gas plenum 116 is used to create an inward sonic flow 119 (shown in Figure 1 and Figure 3A ) in the first region 128. The sonic flow 119 is formed by uniformly distributing an inert gas from the gas plenum 116 to the first region 128 via a series of small orifices 121 (shown in Figure 2 and Figure 3B ) in the base of the gas shroud 110. The orifices 121 can also be referred to as passages subsequently. In embodiments, the orifices 121 are arranged in an annular pattern in the base of the gas shroud 110, where the annular pattern is disposed around the opening 123b. In embodiments, the gas shroud 110 can include multiple rings of orifices 121 in the base of the gas shroud 110. In embodiments, at least one of the multiple rings of orifices 121 is disposed in the sidewall of the opening 123b. The multiple rings of orifices 21 can be arranged in a concentric pattern, where each ring has a different diameter than the other rings.

[0036] The orifices 121 directly connect the gas plenum 116 and allow gas flow from the gas plenum into the first region 128 (e.g., as a conduit or passageway). The orifices 121 can be uniformly distributed around the perimeter of the first region 128, and each orifice 121 can have a diameter D4 (shown in Figure 3B ) that can be in the range of 0.3 mm to 2.0 mm. In embodiments, any number and placement of orifices 121 can be used to create the sonic flow 119.

[0037] The gas plenum 116 is maintained at a much higher pressure than the first region 128, and due to this pressure differential, and due to the diameter D4 of the orifices 121 being in the range of 0.3 mm to 2.0 mm, the inert gas is forced to travel through the orifices 121 into the first region 128 at a speed equivalent to the speed of sound (also referred to as the sonic flow 119). The placement of the orifices 121 directs the sonic flow 119 (e.g., in the form of a jet of inert gas from each orifice 121) at an angle toward the surface of the wafer 126 and toward the plasma plume 112 (e.g., an inward sonic flow). For example, the orifices 121 are angled such that a topmost portion of the sonic flow 119 can be further from a vertical line A-A through the center of the first region 128 than a bottommost portion of the sonic flow 119 that encounters the top surface of the wafer 126. In this way, an inward sonic flow 119 can be created in the first region 128 that completely surrounds the plasma plume 112 and isolates the plasma plume 112 and the first region 128 from the second region 133. The second region 133 is a region adjacent to and surrounding the first region 128, the second region 133 including the space between the base of the gas shield 110 and the top surface of the wafer 126. Additionally, the inward sonic flow 119 isolates the plasma plume 112 and the first region 128 from other regions of the plasma processing chamber 114.

[0038] The inert gas supplied to the gas plenum 116 is supplied through a gas inlet of the gas plenum 116. The inert gas is supplied at a high pressure by an inert gas supply source 124, and the inert gas can include argon, nitrogen, etc.

[0039] Gas can flow from the first region 128 to any section of the gas shield 110 (e.g., the first section 129, the second section 130, or the third section 131), and the direction of flow and the rate of gas flow will depend on the pressure differential between the sections. During the etching process, etching byproducts, unused radicals, unreacted neutrals, and the inert gas used to create the sonic flow 119 are removed upward through the gas shield 110 and out of the gas shield 110 through a gas outlet connected to a vacuum pump 120. The vacuum pump 120 maintains the first section 129, the second section 130, and the third section 131 at a lower pressure than the first region 128, so the flow path for the etching byproducts, unused radicals, unreacted neutrals, and the inert gas used to create the sonic flow 119 can include the etching byproducts, unused radicals, unreacted neutrals, and the inert gas traveling vertically upward from the first region 128, through the first section 129, the second section 130, and then into the third section 131. The third section 131 can include the gas outlet connected to the vacuum pump 120. The etching byproducts, unused radicals, unreacted neutrals, and the inert gas are exhausted from the gas shield 110 through this gas outlet.

[0040] Figure 3A and Figure 3B A cross-sectional view of the gas shield 110 is shown during an etching process that etches material from a top surface of a wafer 126 in the first region 128. Figure 3B A cross-sectional view of the gas shield 110 is shown during an etching process that etches material from a top surface of a wafer 126 in the first region 128. Figure 3A The region 134 of the gas shield 110 shown in FIG. 1 is illustrated. Plasma and radicals generated in the plasma source 106 flow into the plasma processing chamber 114 through the nozzle 108. The radicals and plasma are ejected from the outlet of the nozzle 108 and travel in the form of a plasma plume 112 through the first region 128 toward the top surface of the wafer 126. The radicals in the plasma plume 112 are used to etch material of the wafer 126 in the first region 128.

[0041] Inert gas is supplied to the gas plenum 116 through a gas inlet of the gas plenum 116 at high pressure. The inert gas can include argon, nitrogen, etc., and can be supplied by an inert gas supply source 124. The inert gas is supplied to the gas plenum 116 at high pressure such that there is a large pressure differential between the gas plenum 116 and the first region 128. The pressure PI in the gas plenum 116 is maintained to be much greater than the pressure P2 in the first region 128. The pressure PI is maintained by supplying inert gas through the gas inlet of the gas plenum 116. For example, the pressure PI can be in the range of 1 Torr to 50 Torr, and the pressure P2 can be in the range of 0.1 Torr to 5 Torr. Each orifice 121 that allows inert gas to enter the first region 128 from the gas plenum 116 has a diameter D4 in the range of 0.3 mm to 2.0 mm. Due to the pressure differential between the first region 128 and the gas plenum 116, and due to each of the orifices 121 having a relatively small diameter D4 in the range of 0.3 mm to 2.0 mm, the inert gas is forced to enter the first region 128 through the orifices 121 at a velocity that is equivalent to the speed of sound (e.g., the sonic flow 119). The pressure P2 in the first region 128 can be maintained using the sonic flow 119 that enters the first region 128 from the gas plenum 116. The flow rate of the sonic flow 119 can affect the pressure P2 that can be maintained. For example, a gas shield 110 with more orifices 121 will have a higher flow rate of inert gas entering the first region 128, and thus can maintain a higher pressure P2. A gas shield 110 with fewer orifices 121 will have a lower flow rate of inert gas entering the first region 128, and thus can only maintain a lower pressure P2.

[0042] An inert gas jet (also referred to as sonic flow 119) flows into the first region 128 from the orifice 121 at a speed equivalent to the speed of sound. The sonic flow 119 flows at an angle toward the surface of the wafer 126. The flow pattern of the sonic flow 119 also causes it to move laterally toward the plasma plume 112 (also referred to as inward sonic flow 119). For example, as... Figure 3A As shown, the topmost portion of the sonic flow 119 can be further away from the vertical line AA passing through the center of the first region 128 and the nozzle 108 than the bottommost portion of the sonic flow 119 that encounters the top surface of the wafer 126. In this way, an inward sonic flow 119 can be generated that completely surrounds the plasma plume 112 and isolates the plasma plume 112 and the first region 128 from the second region 133. The second region 133 is the region adjacent to and surrounding the first region 128, and the second region 133 includes the space between the base of the gas shield 110 and the top surface of the wafer 126. In addition, the inward sonic flow 119 isolates the plasma plume 112 and the first region 128 from the other regions of the plasma processing chamber 114. The sonic flow 119 acts as an interface (also called a boundary) between the first region 128 and the second region 133. For example, the first region 128 and the second region 133 have different flows that are kept separate from each other by the sonic flow 119. In this way, the first region 128 can have a different pressure than the second region 133 and be maintained under that different pressure.

[0043] The formation of a sonic flow 119, comprising an inert gas jet flowing into the first region 128 and surrounding the plasma plume 112, allows the maintenance of a pressure difference between pressure P2 in the first region 128 and pressure P3 in the second region 133. Additionally, the formation of a sonic flow 119, comprising an inert gas jet flowing into the first region 128 and surrounding the plasma plume 112, allows the maintenance of a pressure difference between pressure P2 in the first region 128 and pressures in other regions of the plasma processing chamber 114. The pressures in other regions of the plasma processing chamber 114 may be equal to pressure P3. Pressure P3 may be greater than pressure P2. In an embodiment, pressure P3 may be in the range of 0.1 Torr to 10 Torr.

[0044] By forming the inward sonic flow 119 that completely surrounds the plasma plume 112, and the sonic flow 119 forms a boundary interface to isolate the plasma plume 112 and the first region 128 from the second region 133, advantages can be realized. The boundary interface prevents etch byproducts, unused radicals, and unreacted neutrals produced by the etching process from traveling or diffusing from the first region 128 to the second region 133. As a result, they do not come into contact with the surface of the wafer 126 in the second region 133. This results in a reduction of unwanted etching caused by unused etching radicals, and a reduction of contamination of the portion of the wafer 126 in the second region 133 by etch byproducts and unreacted neutrals. If the jet of inert gas from the orifice 121 travels at a speed below the sonic speed, a boundary interface will not be formed between the first region 128 and the second region 133, and it will not be possible to maintain a pressure differential between the pressure P2 in the first region 128 and the pressure P3 in the second region 133.

[0045] Gas can flow from the first region 128 to any section of the gas shroud 110 (e.g., the first section 129, the second section 130, or the third section 131), and the direction of flow and the rate of gas flow will depend on the pressure difference between the sections. As described above, due to the sonic flow 119, a pressure P2 can be maintained in the first region 128. The vacuum pump 120 maintains the first section 129, the second section 130, and the third section 131 of the gas shroud 110 at a lower pressure than the first region 128. Thus, etch byproducts from the etching process, unused radicals, unreacted neutrals, and inert gas used to generate the sonic flow 119 travel from the higher pressure first region 128 to the lower pressure first section 129, second section 130, and third section 131. The etch byproducts, unused radicals, unreacted neutrals, and inert gas used to generate the sonic flow 119 are removed by passing up through the gas shroud 110 and exiting through a gas outlet of the gas shroud 110 that is connected to the vacuum pump 120. In embodiments, the gas shroud 110 can be connected with more than one gas outlet and one or more vacuum pumps 120 to allow for different pumping capabilities. By using the sonic flow 119 to maintain the pressure P2 in the first region 128 to be higher than the pressure in the first section 129, the second section 130, and the third section 131 of the gas shroud 110, an advantage can be realized. This allows the etch byproducts, unused radicals, and unreacted neutrals generated by the etching process to be removed by passing up through the gas shroud 110 and exiting through a gas outlet of the gas shroud 110 that is connected to the vacuum pump 120. Thus, the etch byproducts, unused radicals, and unreacted neutrals have reduced contact with the surface of the wafer 126 in the second region 133. This results in reduced etch damage from unused etch radicals and reduced contamination of the portion of the wafer 126 in the second region 133 by etch byproducts and unreacted neutrals.

[0046] As described above, forming the sonic flow 119 comprising a jet of inert gas flowing into the first region 128 and around the plasma plume 112 allows a pressure differential between the pressure P2 in the first region 128 and the pressure P3 in the second region 133 to be maintained. Additionally, forming the sonic flow 119 comprising a jet of inert gas flowing into the first region 128 and around the plasma plume 112 allows a pressure differential between the pressure P2 in the first region 128 and the pressure in other regions of the plasma processing chamber 114 to be maintained. The plasma plume 112 can have a lateral width Wl, where the lateral width Wl is the width between the outermost points of the plasma plume 112 that are in physical contact with the top surface of the wafer 126. The lateral width Wl is dependent on the pressure P2 in the first region 128, such that the higher the pressure P2, the smaller the lateral width Wl of the plasma plume 112. The lower the pressure P2, the larger the lateral width Wl of the plasma plume 112. Appropriate design choices of the gas shield 110 and its corresponding sonic flow 119 can be used to control the lateral width Wl of the plasma plume 112. In embodiments, the lateral width Wl of the plasma plume 112 can be in the range of 2 mm to 20 mm.

[0047] The flow rate of the sonic flow 119 can affect the pressure P2 that can be maintained. For example, a gas shield 110 with more orifices 121 will have a higher flow of inert gas flowing into the first region 128, and thus can maintain a higher pressure P2. A gas shield 110 with fewer orifices 121 will have a lower flow of inert gas flowing into the first region 128, and thus can only maintain a lower pressure P2.

[0048] By using the gas shroud 110 to generate a sonic flow 119 in the first region 128 in order to maintain a pressure P2 in the first region 128, advantages can be realized. For example, a design choice of the gas shroud 110 with a larger number of orifices 121 will increase the flow of the sonic flow 119 into the first region 128 and allow a higher pressure P2 to be maintained in the first region 128. This will cause the lateral width Wl of the plasma plume 112 to decrease. A design choice of the gas shroud 110 with a smaller number of orifices 121 will decrease the flow of the sonic flow 119 into the first region 128 and allow a lower pressure P2 to be maintained in the first region 128. This will cause the lateral width Wl of the plasma plume 112 to increase. Being able to control the lateral width Wl of the plasma plume 112 in this manner allows for better etch control, improved concentration of the plasma plume 112, and better etch spot size control, allowing for high resolution etching and achieving better uniformity on the surface of the wafer 126. Additionally, it is more convenient and easier to maintain the pressure P2 in the first region 128 during plasma processing than to maintain the pressure in the entire plasma processing chamber 114. This is because the volume of the first region 128 is much smaller than the volume of the plasma processing chamber 114. For example, by varying the flow of inert gas supplied to the gas plenum 116, the pressure P2 in the first region 128 can be adjusted in a dynamic manner, allowing for more dynamic control of the lateral width Wl of the plasma plume 112. In contrast, changing the pressure of the entire plasma processing chamber 114 would take a longer time to accomplish because the volume of the plasma processing chamber 114 is larger than the volume of the first region 128.

[0049] In alternative embodiments, the inert gas supplied to the gas plenum 116 at high pressure can be forced to pass through the orifices 121 into the first region 128 at a subsonic velocity (e.g., in a range between 90 to 99 percent of the speed of sound). The jet of inert gas (also referred to as a subsonic flow) can flow from the orifices 121 into the first region 128 at a velocity that is less than the speed of sound. The subsonic flow can flow at an angle toward the surface of the wafer 126. The manner in which the subsonic flow flows will also cause it to move a lateral distance toward the plasma plume 112. In this manner, a subsonic flow can be generated that completely surrounds the plasma plume 112.

[0050] The vacuum pump 120 maintains the first section 129, the second section 130, and the third section 131 of the gas shield 110 at a lower pressure than the first region 128 and other regions of the plasma processing chamber 114. The subsonic flow causes the pressure in the first region 128 to increase and forces the overall flow upward toward the vacuum pump 120. The subsonic flow can push etch byproducts, unused radicals, and unreacted neutrals from the etching process into and confine them to the first region 128 and prevent them from traveling to the second region 133. By pushing the etch byproducts, unused radicals, and unreacted neutrals into and confining them to the first region 128, an increased amount of the etch byproducts, unused radicals, and unreacted neutrals can be removed from the gas outlet of the gas shield 110 through the first section 129, the second section 130, and the third section 131. By using the subsonic flow to push the etch byproducts, unused radicals, and unreacted neutrals from the etching process into and confine them to the first region 128 and prevent them from traveling to the second region 133, advantages can be realized. These advantages include that the amount of etch byproducts, unused radicals, and unreacted neutrals produced by the etching process that are removed from the first region 128 upward through the gas shield 110 and out of the gas outlet of the gas shield 110 that is connected to the vacuum pump 120 is increased. As a result, the contact of the etch byproducts, unused radicals, and unreacted neutrals with the surface of the wafer 126 in the second region 133 is reduced. This results in a reduction of etching damage caused by unused etching radicals and a reduction of contamination of the portion of the wafer 126 in the second region 133 by the etch byproducts and unreacted neutrals.

[0051] Figure 4A A top view of an example plasma processing tool 210 according to some embodiments is shown. The plasma processing tool 210 includes features previously described in Figures 1 to 3B and additional features that provide further advantages. Unless otherwise noted, the same reference numerals are used in Figure 4A and Figure 4B to refer to the same components previously described and illustrated in Figures 1 to 3B and formed by the same processes. Accordingly, process steps and applicable materials are not repeated here. Subsequently described Figure 4AThe example plasma processing tool 210 is used in the context of an etch operation. However, aspects of the embodiments described herein can be used for other plasma operations, including ashing, deposition, cleaning, plasma polymerization, plasma-enhanced chemical vapor deposition (PECVD), plasma-enhanced atomic layer deposition (PEALD), etc. In particular, the plasma processing tool 210 can be used to perform a variety of processes, and these processes can be etch processes or deposition processes that utilize successive etching and / or deposition steps to achieve atomic layer deposition (ALD) or atomic layer etching (ALE) or a combination of both to achieve area-selective etching or deposition.

[0052] The example plasma processing tool 210 according to embodiments disclosed herein can be used to perform a variety of etch processes (e.g., etch process 138, etch process 139, etch process 140, and etch process 141). The plasma processing tool 210 can perform any number of different etch processes.

[0053] Figure 4A The illustrated plasma processing tool 210 can include a rotatable pedestal 136 (also referred to as a circular turntable) in a processing chamber. The pedestal 136 can include a plurality of vacuum chucks or electrostatic chucks disposed about a center of the pedestal 136 to enable a plurality of wafers 126 to be held or retained in place against a top surface of the pedestal 136. The vacuum chucks or electrostatic chucks can be disposed equidistant from one another on the pedestal 136. In Figure 4A In the example of FIG. 1, four wafers 126 (e.g., wafer 126A, wafer 126B, wafer 126C, and wafer 126D) are shown being held against the top surface of the pedestal 136 using vacuum chucks for processing. However, the pedestal 136 can hold or support any number of wafers 126 for processing. In Figure 4A In the example of FIG. 1, the wafers 126 are shown in dashed lines.

[0054] The plasma processing tool 210 can include a load port (not shown) and a handler (not shown). The load port can be used to load the wafers 126 into the plasma processing tool 210 and then unload the wafers 126 after the plasma processing has been completed. The handler can be used to transfer each wafer 126 to a prescribed location on the pedestal 136 where it is held or retained against the top surface of the pedestal 136 by a corresponding vacuum chuck or electrostatic chuck. The handler can include a robotic machine, an automated machine, or a transfer robot adapted to mechanically position and manipulate the wafers 126 within the plasma processing tool 210 during processing. Figure 4AFour wafers 126 are shown being held or retained on a top surface of a pedestal 136 using vacuum chucks or electrostatic chucks. Each wafer 126 (e.g., wafer 126A, wafer 126B, wafer 126C, and wafer 126D) is disposed under a respective gas shield 110 (e.g., gas shield 110A, gas shield 110B, gas shield 110C, and gas shield 110D) and a respective nozzle 108 of the plasma processing tool 210. Each wafer 126 under a respective gas shield 110 and a respective nozzle 108 can be subjected to a plasma etching process using a plasma plume 112 at an outlet of the respective nozzle 108 in a similar manner as previously described in Figures 1 to 3B the previous section. Each wafer 126 subjected to an etching process can be subjected to a different etching process than the etching process subjected to by the other wafers 126, where the etching process uses a different etchant than the etchant of the other etching processes.

[0055] Each gas shield 110 and its corresponding nozzle 108 can be configured to facilitate a plasma etch process that is different (e.g., different by using a different etchant) from the plasma etch processes facilitated by the other gas shields 110 and their corresponding nozzles 108. To perform an etch process, the susceptor 136 is rotated to position a wafer 126 under a gas shield 110 and its corresponding nozzle 108, after which the etch process is performed. In embodiments, different wafers 126 can be simultaneously etched in the plasma processing tool 210 using different etch processes while positioned under different gas shields 110 and their corresponding nozzles 108. Additionally, the susceptor 136 can also be rotated so that a single wafer 126 can sequentially undergo different types of etch processes within the same plasma processing tool 210. For example, wafer 126A can be positioned under gas shield 110A, where etch process 138 is performed on wafer 126A. Wafer 126B can be positioned under gas shield 110B, where etch process 139 is performed on wafer 126B. Wafer 126C can be positioned under gas shield 110C, where etch process 140 is performed on wafer 126C. Wafer 126D can be positioned under gas shield 110D, where etch process 141 is performed on wafer 126D. Each of etch process 138, etch process 139, etch process 140, and etch process 141 can be different from the other etch processes. The etchant of each of etch process 138, etch process 139, etch process 140, and etch process 141 can be different from the etchant of the other etch processes. When in the plasma processing tool 210, a first wafer 126A under gas shield 110A is undergoing a first etch process (e.g., one of etch process 138, etch process 139, etch process 140, or etch process 141), and an adjacent second wafer 126B under gas shield 110B is undergoing another simultaneous etch process (e.g., one of etch process 138, etch process 139, etch process 140, or etch process 141), the sonic flow 119 can be used to isolate and prevent etch byproducts, unused radicals, and unreacted neutrals from the first etch process from contacting the second wafer 126B, and to isolate and prevent etch byproducts, unused radicals, and unreacted neutrals from the second etch process from contacting the first wafer 126A.

[0056] Figure 4B It is shown that Figure 4AA cross-sectional view of one of the gas shrouds 110A / 110B / 110C / 110D is shown. The example etching process described subsequently is explained in the context of an example etching process for etching a wafer 126A underneath the gas shroud 110A. However, the gas shroud 110B, the gas shroud 110C, and the gas shroud 110D can be similar to the gas shroud 110A, and unless otherwise noted, the same description of the example etching process can apply to etching of any of the wafer 126B, the wafer 126C, and the wafer 126D underneath the gas shroud 110B, the gas shroud 110C, and the gas shroud 110D, respectively. Figure 4B The gas shroud 110A can exhibit a width along the line A-A that is greater than a width of the gas shroud 110 along the line A-A. Figure 4A A cross-sectional view along the line B-B is shown.

[0057] Figure 4A Figure 4B The gas shroud 110A can differ from the gas shroud 110 previously described in Figures 1 to 3B The gas shroud 110A can have a width that is greater than a width of the gas shroud 110 previously described in Figures 1 to 3B The gas shroud 110A has a circular shape in a top view and has a circular opening 123c on a top-most surface of the gas shroud 110A and a circular opening 123d at a bottom-most surface of the gas shroud 110A. The diameter of the opening 123d can be greater than the diameter of the opening 123c, and the opening 123c can overlap and connect with the opening 123d. The diameter of the opening 123d of the gas shroud 110A is also greater than the diameter of the opening 123b of the gas shroud 110 previously described in Figures 1 to 3B The opening 123d of the gas shroud 110A includes a first space disposed between sidewalls of a base of the gas shroud 110A. The first region 128 includes a combination of the first space of the opening 123d and a second space disposed vertically below and overlapping the opening 123d, the second space being between the opening 123 and a top surface of the pedestal 136. Due to the larger opening 123d, the entire wafer 126A is contained within the first region 128.

[0058] The gas plenum 116 is used to create an inward acoustic velocity flow 119A in the first region 128 and an outward acoustic velocity flow 119B outside the first region 128. The inward acoustic velocity flow 119A is created by passing an inert gas through a series of small orifices 121A Figure 4B ​(As shown) is formed by uniformly distributing gas from gas chamber 116 into first region 128. Orifice 121A may also be referred to as channel. In an embodiment, orifice 121A is arranged in an annular pattern in the base of gas shroud 110, wherein the annular pattern is arranged around opening 123d. The placement of orifice 121A directs the sonic flow 119A (e.g., in the form of an inert gas jet from each orifice 121A traveling at a speed equal to the speed of sound) at an angle toward the surface of base 136 and toward plasma plume 112 (e.g., inward sonic flow). For example, orifice 121A is angled such that the topmost portion of sonic flow 119A can be further away from the vertical line CC passing through the center of first region 128 and nozzle 108 than the bottommost portion of sonic flow 119A encountering the top surface of base 136. In this way, an inward sonic flow 119A can be generated that completely surrounds the plasma plume 112 and the wafer 126A in the first region 128.

[0059] The outward sonic flow 119B is achieved by passing inert gas through a series of small orifices 121B in the base of the gas shield 110. Figure 4B (As shown) The gas is uniformly distributed from the gas chamber 116 to the third region 135. The third region 135 is adjacent to and surrounds the first region 128, and includes the space between the base of the gas shield 110 and the top surface of the base 136. The orifice 121B may also be referred to as a channel. In an embodiment, the orifice 121B is arranged in an annular pattern in the base of the gas shield 110, wherein the annular pattern surrounds the opening 123d and the annular pattern of the orifice 121A. In an embodiment, the annular patterns of the orifice 121A and the orifice 121B are arranged concentrically, wherein the diameter of the annular pattern of the orifice 121A is smaller than the diameter of the annular pattern of the orifice 121B. The placement of orifice 121B directs the sound velocity flow 119B (e.g., in the form of an inert gas jet traveling at a speed equal to the speed of sound from each orifice 121B) at an angle toward the surface of base 136 and away from the plasma plume 112 (e.g., an outward sound velocity flow). For example, orifice 121B is angled such that the topmost portion of the sound velocity flow 119B can be closer to the vertical line CC passing through the center of the first region 128 and nozzle 108 than the bottommost portion of the sound velocity flow 119B encountering the top surface of base 136. In this way, an outward sound velocity flow 119B that completely surrounds the inward sound velocity flow 119A and the first region 128 can be generated.

[0060] The inward sonic flow 119A completely surrounds the plasma plume 112 and the wafer 126A in the first region 128 and isolates them from the third region 135 and other regions of the processing chamber of the plasma processing tool 210. The outward sonic flow 119B completely surrounds the first region 128 and further isolates the plasma plume 112 and the wafer 126A from other regions of the processing chamber of the plasma processing tool 210. The inward sonic flow 119A acts as a demarcation (also referred to as a boundary) between the first region 128 and the third region 135. The outward sonic flow 119B also acts as a demarcation between the first region 128 and the third region 135. For example, the first region 128 and the third region 135 have different flows that are kept separate from each other by the sonic flows 119A and 119B. In this way, the first region 128 can have a different pressure from the third region 135 and be maintained at that different pressure.

[0061] The formation of the sonic flow 119A including a jet of inert gas flowing into the first region 128 allows a pressure differential between the pressure P4 in the first region 128 and the pressure P5 in the third region 135 to be maintained. The formation of the sonic flow 119A including a jet of inert gas flowing into the first region 128 allows the pressure P4 in the first region 128 to be maintained. The formation of the sonic flow 119B including a jet of inert gas flowing into the third region 135 and surrounding the first region 128 and the inward sonic flow 119A allows the pressure P5 in the third region 135 to be maintained. Additionally, the formation of the sonic flow 119A flowing into the first region 128 allows a pressure differential between the pressure P4 in the first region 128 and the pressure in other regions of the processing chamber of the plasma processing tool 210 to be maintained. The pressure in other regions of the processing chamber of the plasma processing tool 210 can be equal to the pressure P6. The pressure P6 can be greater than the pressure P4 and the pressure P5. In embodiments, the pressure P4 in the first region 128 can be in the range of 0.1 Torr to 5.0 Torr. In embodiments, the pressure P5 in the third region 135 can be in the range of 0.1 Torr to 5.0 Torr. In embodiments, the pressure P6 in other regions of the processing chamber of the plasma processing tool 210 can be in the range of 0.1 Torr to 5.0 Torr.

[0062] An advantage can be realized by forming the inward acoustic velocity flow 119A in the first region 128 that completely surrounds the plasma plume 112 and the wafer 126A, and by forming the outward acoustic velocity flow 119B in the third region 135 that surrounds the inward acoustic velocity flow 119A and the first region 128. Each of the inward acoustic velocity flow 119A and the outward acoustic velocity flow 119B forms an interface to isolate the plasma plume 112, the wafer 126A, and the first region 128 from the second region 133. These interfaces prevent etch byproducts, unused radicals, and unreacted neutrals produced by the etching process performed on the wafer 126A in the first region 128 from traveling or diffusing to the second region 133 and other regions of the processing chamber of the plasma processing tool 210. As a result, they do not come into contact with the surfaces of other adjacent wafers 126 (e.g., wafer 126B, wafer 126C, and wafer 126D) in the processing chamber of the plasma processing tool 210. This results in a reduction of etch damage caused by unused etching radicals, and a reduction of contamination of other wafers 126 (e.g., wafer 126B, wafer 126C, and wafer 126D) in the processing chamber by etch byproducts and unreacted neutrals. In addition, etch byproducts, unused radicals, and unreacted neutrals produced by the etching process performed on other wafers 126 (e.g., wafer 126B, wafer 126C, and wafer 126D) are prevented from traveling to the first region 128 or diffusing into the first region. This also allows different wafers 126 to be simultaneously subjected to different etching processes (e.g., etching process 138, etching process 139, etching process 140, and etching process 141) in the same processing chamber without the etch byproducts, unused radicals, and unreacted neutrals from one of these etching processes adversely affecting adjacent wafers 126. It should be noted that although the above advantages relate to the use of the plasma processing tool 210 for performing etching processes, the plasma processing tool 210 can also be used to perform deposition processes, or a cyclic combination of etching processes and deposition processes, where the inward acoustic velocity flow 119A and the outward acoustic velocity flow 119B likewise perform the function of forming an interface to isolate the plasma plume 112, the wafer 126A, and the first region 128 from the second region 133.

[0063] The plasma plume 112 can have a lateral width W2, where the lateral width W2 is the width between the outermost points of the plasma plume 112 that are in physical contact with the top surface of the wafer 126A. The lateral width W2 depends on the pressure P4 in the first region 128, such that the higher the pressure P4, the smaller the lateral width W2 of the plasma plume 112. The lower the pressure P4, the larger the lateral width W2 of the plasma plume 112. Thus, the design choice of the gas shroud 110A can be used to maintain an appropriate pressure P4 within the first region 128 in order to achieve a plasma plume 112 with a desired lateral width W2. In embodiments, the lateral width W2 of the plasma plume 112 can be in the range of 2.0 mm to 350.0 mm.

[0064] The pressure P4 in the first region 128 can be maintained by using the sonic flow 119A into the first region 128. The flow rate of the sonic flow 119A can affect the pressure P4 that can be maintained. For example, a gas shroud 110A with more orifices 121A will have a higher flow rate of inert gas into the first region 128 and thus can maintain a higher pressure P4. A gas shroud 110 with fewer orifices 121A will have a lower flow rate of inert gas into the first region 128 and thus can only maintain a lower pressure P4.

[0065] By using the gas shroud 110A to create a sonic flow 119A in the first region 128 to maintain a pressure P4 in the first region 128, advantages can be achieved. For example, using a sonic flow 119A to maintain a higher pressure P4 in the first region 128 will result in a decrease in the lateral width W2 of the plasma plume 112, while using a sonic flow 119A to maintain a lower pressure P4 in the first region 128 will result in an increase in the lateral width W2 of the plasma plume 112. Being able to control the lateral width W2 of the plasma plume 112 allows for better etch control, improved concentration of the plasma plume 112, and better etch spot size control, allowing for high resolution etching and achieving better uniformity on the surface of the wafer 126. Additionally, maintaining the pressure P4 in the first region 128 during plasma processing is more convenient and easier than adjusting the pressure in the entire processing chamber of the plasma processing tool 210. This is because the volume of the first region 128 is much smaller than the volume of the processing chamber of the plasma processing tool 210.

[0066] The vacuum pump 120 will draw gas from the first section 129, the second section 130, and the third section 131 (previously described in FIG. 1) of the gas shroud 110A, the first region 128, and the second region 129. The vacuum pump 120 will draw gas from the first section 129, the second section 130, and the third section 131 of the gas shroud 110A, the first region 128, and the second region 129 at a rate that is dependent on the pressure P4 in the first region 128. The higher the pressure P4 in the first region 128, the higher the rate at which the vacuum pump 120 will draw gas from the first section 129, the second section 130, and the third section 131 of the gas shroud 110A, the first region 128, and the second region 129. The lower the pressure P4 in the first region 128, the lower the rate at which the vacuum pump 120 will draw gas from the first section 129, the second section 130, and the third section 131 of the gas shroud 110A, the first region 128, and the second region 129. Figure 2The first region 128 is maintained at a higher pressure than the first section 129, the second section 130, and the third section 131 (shown in FIG. 1). Thus, etching byproducts, unused radicals, unreacted neutrals, and inert gas used to create the sonic flow 119A from the etching process travel from the higher pressure first region 128 to the lower pressure first section 129, the second section 130, and the third section 131. The etching byproducts, unused radicals, unreacted neutrals, and inert gas used to create the sonic flow 119A are then removed using the flow path 132 up through the gas shield 110A and out of the gas outlet of the gas shield 110A connected to the vacuum pump 120. In embodiments, the gas shield 110A can be connected with more than one gas outlet and one or more vacuum pumps 120 to allow for different pumping capabilities. By using the sonic flow 119A to maintain the pressure P4 in the first region 128 to be higher than the pressure in the first section 129, the second section 130, and the third section 131 of the gas shield 110A, an advantage can be realized. This allows the etching byproducts, unused radicals, and unreacted neutrals produced by the etching process to be removed up through the gas shield 110A and out of the gas outlet of the gas shield 110A connected to the vacuum pump 120. Thus, the etching byproducts, unused radicals, and unreacted neutrals have reduced contact with the surfaces of other wafers 126 (e.g., wafer 126B, wafer 126C, and wafer 126D) in the processing chamber. This results in reduced etching damage from unused etching radicals and reduced contamination of other wafers 126 in the processing chamber of the plasma processing tool 210 by etching byproducts and unreacted neutrals.

[0067] Figure 5 A flowchart 300 is shown that includes methods of generating a plasma from a plasma source (block 302) and directing the plasma into a processing chamber and to an outer surface of a wafer using a vertical nozzle (block 304). The plasma processing methods further include supplying (block 306) an inert gas to a gas plenum of a gas shield to maintain a first pressure in the gas plenum and distributing (block 308) the inert gas from the gas plenum to a first region to maintain a second pressure in the first region, the first pressure being higher than the second pressure. These method steps can be implemented using the embodiments previously described in detail in Figures 1 to 4B

[0068] While embodiments of the disclosure and the advantages thereof have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the disclosure as defined by the appended claims.

[0069] Example embodiments of the present application are described below. Other embodiments can be understood according to the entire specification and claims submitted herewith. ​

[0070] Example 1. A plasma processing apparatus comprising a plasma generation source, a nozzle in a plasma chamber, the nozzle capable of directing plasma from the plasma generation source to a wafer to be processed. The plasma assumes the form of a plasma beam at an exit of the nozzle. The plasma processing apparatus further comprises a gas shield disposed in the plasma chamber and above the wafer, the gas shield encircling the nozzle. The gas shield comprises a first circular opening in a top surface of the gas shield, a second circular opening in a bottom most surface of the gas shield, the nozzle disposed in the first circular opening and the second circular opening. The gas shield further comprises a gas plenum configured to be maintained at a first pressure, a first region between the second circular opening and a top surface of the wafer configured to be maintained at a second pressure, the first pressure and the second pressure being different.

[0071] Example 2. The plasma processing apparatus of example 1, wherein the first pressure is greater than the second pressure.

[0072] Example 3. The plasma processing apparatus of one of examples 1 or 2, wherein the first pressure is in a range of 1.0 Torr to 50.0 Torr, and the second pressure is in a range of 0.1 Torr to 5.0 Torr.

[0073] Example 4. The plasma processing apparatus of one of examples 1 to 3, further comprising apertures directly connecting the gas plenum and the first region and allowing gas to flow between the gas plenum and the first region.

[0074] Example 5. The plasma processing apparatus of example 4, wherein the apertures are arranged in the form of an annular pattern, the annular pattern disposed around the second circular opening.

[0075] Example 6. The plasma processing apparatus of one of examples 4 to 5, wherein the flow of gas between the gas plenum and the first region through the apertures is in the form of gas jets, and wherein the gas jets encircle the plasma beam.

[0076] Example 7. The plasma processing apparatus of example 6, wherein the gas jets travel at a speed equal to the speed of sound.

[0077] Example 8. The plasma processing apparatus of one of examples 4 to 7, wherein a diameter of each of the apertures is in a range of 0.3 mm to 2.0 mm.

[0078] Example 9. The plasma processing apparatus of one of Examples 1 to 8, wherein a lateral width of the plasma beam is in a range of 2 mm to 20 mm, the lateral width being a width between outermost points of the plasma beam that are in physical contact with the top surface of the wafer.

[0079] Example 10. A plasma processing method comprising: generating a plasma from a plasma source; and directing the plasma into a processing chamber and to an outer surface of a wafer using a vertical nozzle. The plasma exits at an end of the vertical nozzle disposed above the outer surface of the wafer, and the plasma exits in a form of a plasma beam. The vertical nozzle extends through a gas shroud that surrounds the vertical nozzle and is disposed above the wafer. The plasma beam is disposed in a first region that includes a space between an opening in a bottommost surface of the gas shroud and the outer surface of the wafer. The plasma processing method further comprises: supplying an inert gas to a gas plenum of the gas shroud to maintain a first pressure in the gas plenum; and distributing the inert gas from the gas plenum to the first region to maintain a second pressure in the first region, the first pressure being higher than the second pressure.

[0080] Example 11. The method of Example 10, wherein a second region adjacent to and surrounding the first region has a third pressure, the third pressure being different from the first pressure and the second pressure.

[0081] Example 12. The method of one of Examples 10 or 11, wherein distributing the inert gas from the gas plenum to the first region comprises flowing inert gas jets through channels disposed in a base of the gas shroud.

[0082] Example 13. The method of Example 12, wherein the inert gas jets travel at a speed equal to a speed of sound.

[0083] Example 14. The method of one of Examples 12 to 13, wherein topmost portions of the inert gas jets are further from a vertical line through a center of the first region and the vertical nozzle than bottommost portions of the inert gas jets that encounter the outer surface of the wafer.

[0084] Example 15. The method of one of Examples 10 to 14, wherein the first region encompasses the entire wafer.

[0085] Example 16. An apparatus comprising: a radical source; a nozzle configured to transport radicals from the radical source into a process chamber; and a gas shield disposed in the process chamber above a wafer to be processed. The gas shield comprises a first opening in a topmost surface of the gas shield and a second opening in a bottommost surface of the gas shield. A first region is disposed between the second opening and a top surface of the wafer. The gas shield further comprises a gas plenum and first orifices arranged in an annular pattern around the second opening. The first orifices act as conduits for gas flow between the gas plenum and the first region, and an outlet of the nozzle is disposed in the first region above the wafer. The nozzle extends through the first opening, the second opening, and the gas shield.

[0086] Example 17. The apparatus of Example 16, wherein the gas shield further comprises: a gas inlet through which an inert gas is supplied to the gas plenum to maintain the gas plenum at a first pressure; and a gas outlet connected to a vacuum pump to remove unused radicals and contaminants from the gas shield.

[0087] Example 18. The apparatus of Example 17, wherein the first region is maintained at a second pressure, the first pressure being higher than the second pressure.

[0088] Example 19. The apparatus of one of Examples 16-18, wherein gas flow between the gas plenum and the first region in the first orifices is in the form of first gas jets, and wherein the first gas jets travel at a speed equal to the speed of sound.

[0089] Example 20. The apparatus of one of Examples 18-19, further comprising second orifices arranged in an annular pattern around the first orifices, the second orifices acting as conduits for gas flow between the gas plenum and a second region, wherein the second region surrounds and is adjacent to the first region, wherein gas flow between the gas plenum and the second region in the second orifices is in the form of second gas jets, wherein the second gas jets travel at a speed equal to the speed of sound, wherein the second gas jets travel in a direction away from the nozzle, and wherein the second region has a pressure different from the first pressure and the second pressure.

[0090] Moreover, the scope of the application is not intended to be limited to particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the presently disclosed, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed, that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein can be utilized according to the present disclosure. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.

Claims

1. A plasma processing apparatus comprising: a plasma generation source; a nozzle in a plasma chamber, the nozzle capable of directing plasma from the plasma generation source to a wafer to be processed, the plasma assuming the form of a plasma beam at an outlet of the nozzle; a gas shroud disposed in the plasma chamber and above the wafer, the gas shroud encircling the nozzle, the gas shroud comprising: a first circular opening in a top surface of the gas shroud; a second circular opening in a bottom most surface of the gas shroud, the nozzle disposed in the first circular opening and the second circular opening; and a gas plenum configured to be maintained at a first pressure, a first region between the second circular opening and a top surface of the wafer configured to be maintained at a second pressure, the first pressure and the second pressure being different.

2. The plasma processing apparatus of claim 1, wherein, The first pressure is greater than the second pressure.

3. The plasma processing apparatus of claim 1, wherein, The first pressure is in a range of 1.0 Torr to 50.0 Torr and the second pressure is in a range of 0.1 Torr to 5.0 Torr.

4. The plasma processing apparatus of claim 1, further comprising orifices, the orifices directly connecting the gas plenum and the first region and allowing gas to flow between the gas plenum and the first region.

5. The plasma processing apparatus of claim 4, wherein, The orifices are arranged in an annular pattern disposed around the second circular opening.

6. The plasma processing apparatus of claim 5, wherein, Flow of gas between the gas plenum and the first region through the orifices is in the form of gas jets, and wherein the gas jets encircle the plasma beam.

7. The plasma processing apparatus of claim 6, wherein, The gas jets travel at a speed equal to the speed of sound.

8. The plasma processing apparatus of claim 7, wherein, A diameter of each of the orifices is in a range of 0.3 mm to 2.0 mm.

9. The plasma processing apparatus of claim 1, wherein, A lateral width of the plasma beam is in a range of 2 mm to 20 mm, the lateral width being a width between outermost points of the plasma beam in physical contact with the top surface of the wafer.

10. A plasma processing method comprising: generating a plasma from a plasma source; directing the plasma into a processing chamber and to an outer surface of a wafer using a vertical nozzle, the plasma exiting at an end of the vertical nozzle disposed above the outer surface of the wafer, the plasma exiting in the form of a plasma beam, the vertical nozzle extending through a gas shroud encircling the vertical nozzle and disposed above the wafer, the plasma beam disposed in a first region, the first region comprising a space between an opening in a bottom most surface of the gas shroud and the outer surface of the wafer; supplying an inert gas to a gas plenum of the gas shroud to maintain a first pressure in the gas plenum; and distributing the inert gas from the gas plenum to the first region to maintain a second pressure in the first region, the first pressure being higher than the second pressure.

11. The method of claim 10, wherein, A second region adjacent to and encircling the first region has a third pressure, the third pressure being different from the first pressure and the second pressure.

12. The method of claim 10, wherein, Distributing the inert gas from the gas plenum to the first region includes flowing inert gas jets through channels disposed in a base of the gas shroud.

13. The method of claim 12, wherein, The inert gas jets travel at a speed equal to the speed of sound.

14. The method of claim 13, wherein, The topmost portions of the jets of inert gas are further from a vertical line through the center of the first region and the vertical nozzle than the bottommost portions of the jets of inert gas that encounter the outer surface of the wafer.

15. The method of claim 10, wherein, The first region includes the entire wafer.

16. An apparatus comprising: a radical source; a nozzle configured to deliver radicals from the radical source into a process chamber; a gas shroud disposed in the process chamber above a wafer to be processed, the gas shroud comprising: a first opening in a topmost surface of the gas shroud; a second opening in a bottommost surface of the gas shroud, a first region disposed between the second opening and a top surface of the wafer; a gas plenum; and first orifices arranged in an annular pattern around the second opening, the first orifices acting as conduits for gas flow between the gas plenum and the first region, an outlet of the nozzle disposed in the first region and above the wafer, the nozzle extending through the first opening, the second opening, and the gas shroud.

17. The apparatus of claim 16, wherein, The gas shroud further comprises a gas inlet through which inert gas is supplied to the gas plenum to maintain the gas plenum at a first pressure, and a gas outlet connected to a vacuum pump to remove unused radicals and contaminants from the gas shroud.

18. The apparatus of claim 17, wherein, The first region is maintained at a second pressure, the first pressure being higher than the second pressure.

19. The apparatus of claim 18, wherein, Gas flow between the gas plenum and the first region in the first orifices is in the form of first gas jets, and wherein the first gas jets travel at a speed equal to the speed of sound.

20. The apparatus of claim 19, further comprising: second orifices arranged in an annular pattern around the first orifices, the second orifices acting as conduits for gas flow between the gas plenum and a second region, wherein the second region surrounds and is adjacent to the first region, wherein gas flow between the gas plenum and the second region in the second orifices is in the form of second gas jets, wherein the second gas jets travel at a speed equal to the speed of sound, wherein the second gas jets travel in a direction away from the nozzle, and wherein the second region has a pressure different from the first pressure and the second pressure.

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