Patent ID: 12191156

DETAILED DESCRIPTION

The present embodiments will now be described more fully hereinafter with reference to the accompanying drawings, wherein some embodiments are shown. The subject matter of the present disclosure may be embodied in many different forms and is not to be construed as limited to the embodiments set forth herein. These embodiments are provided so this disclosure will be thorough and complete, and will convey certain exemplary aspects of the subject matter to those skilled in the art. In the drawings, like numbers refer to like elements throughout.

Referring toFIG.1A, a schematic cross-sectional view illustrating a ribbon beam plasma enhanced chemical vapor deposition system10(hereinafter “the system10”) in accordance with an exemplary embodiment of the present disclosure is shown. The system10may generally include a plasma source12disposed adjacent a process chamber14. The plasma source12may be adapted to generate an energetic plasma16in a plasma chamber18, and to emit the plasma16(e.g., through a nozzle20of the plasma chamber18) as further described below. While the plasma chamber18is depicted as being generally cylindrical in shape, the present disclosure is not limited in this regard, and the plasma chamber18may be implemented in a variety of alterative shapes and configurations.

The process chamber14may contain a platen22adapted to support a substrate24(e.g., a silicon wafer) in a confronting relationship with the nozzle20of the plasma chamber18. In various embodiments, the platen22may be adapted to forcibly retain the substrate24, such as via electrostatic clamping or mechanical clamping. Additionally, the platen22may include a heating element (not shown) for controllably heating the substrate24to a desired temperature (e.g., a temperature in a range between room temperature and 450 degrees Celsius) to enhance deposition processes.

The plasma source12of the system10may be configured to generate the plasma16from a gaseous species supplied to the plasma chamber18by one or more gas sources30. The gaseous species may include one or more of SiH4, CH4, NH3, O2, N2, SiCl4, GeH4, Ar, WF6, etc. The present disclosure is not limited in this regard. The plasma16(and particularly free radicals within the plasma) may be projected through the nozzle20in the form of a ribbon beam32directed at the substrate24as further described below. In various embodiments, the plasma source12may be a radio frequency (RF) plasma source (e.g., an inductively-coupled plasma (ICP) source, a capacitively coupled plasma (CCP) source, a helicon source, an electron cyclotron resonance (ECR) source, etc.). For example, the plasma source12may include electrodes34a,34b, an RF generator36, and an RF matching network38for igniting and sustaining the plasma16in a manner familiar to those of ordinary skill in the art. The present disclosure is not limited in this regard.

The plasma16generated in the plasma chamber18may contain ionized gas species (ions), electrons, excited neutrals, and free radicals. In conventional plasma enhanced chemical vapor deposition (PECVD) systems, a substrate is located in the same chamber as a plasma, and free radicals within the plasma are distributed over the surface of the substrate in a directionally-nonspecific, isotropic manner to form a thin film of generally uniform thickness on the exposed surface(s) of the substrate. By contrast, the plasma chamber18of the system10is separate from the process chamber14where the platen22and the substrate24reside, and a collimated ribbon beam32containing free radicals of the plasma16is extracted from the plasma chamber18and is directed at the substrate24in a directionally-specific, anisotropic manner. This is achieved by establishing a pressure differential between the plasma chamber18and the process chamber14, and by collimating the extracting the ion beam. In a non-limiting example, the ion beam may be extracted through a nozzle20having an elongated profile (described in greater detail below). With regard to the pressure differential, the process chamber14may be maintained at a first pressure, and the plasma chamber18may be maintained at a second pressure higher than the first pressure. In various examples, the first pressure in the process chamber may be in a range of 10−6torr to 10−2torr, and the second pressure in the plasma chamber18may be in a range of 1 millitorr to 1 torr. The present disclosure is not limited in this regard. Thus, the pressure differential between the plasma chamber18and the process chamber14may provide a motive force for driving free radicals in the plasma16from the plasma chamber18into the process chamber14in the form of a ribbon beam32.

The ribbon beam32may be given its shape and may be collimated using various structures, devices, and techniques. In one example, the ribbon beam32may be given its shape and may be collimated by the elongated, low-profile nozzle20of the plasma chamber18. The nozzle20is illustrated in greater detail in the isometric cross-sectional views shown inFIGS.2A and2B. As depicted, the nozzle20may define an aperture40having a width measured in a direction parallel to the X-axis (and parallel to a longitudinal axis of the plasma chamber18) of the illustrated Cartesian coordinate system, and having a height measured in a direction parallel to the Y-axis of the illustrated Cartesian coordinate system. In various embodiments, an aspect ratio of the width of the aperture40relative to the height of the aperture40may be in a range of 12:1 to 60:1. In specific examples, the aperture40may have a width of 300 millimeters and a height in a range of 5 millimeters to 25 millimeters. The present disclosure is not limited in this regard.

The nozzle20may extend radially from the plasma chamber18, thus providing the aperture40with a depth as measured in a direction parallel to the Z-axis of the illustrated Cartesian coordinate system. In various embodiments, the aperture40may have a depth in a range of 7 millimeters to 20 millimeters. In a particular embodiment, the aperture40may have a depth of 10 millimeters. The present disclosure is not limited in this regard. Thus, the radially-elongated nozzle20may funnel or channel free radicals exiting the plasma chamber18in the ribbon beam32, and may tend to collimate the free radicals and facilitate a long mean free path of the free radicals, where the free radicals (and the ribbon beam32generally) may otherwise tend to diverge after exiting the plasma chamber18. An intended directionality of the ribbon beam32may thus be preserved when used to selectively deposit a thin film on the substrate24. In various embodiments, the nozzle20may be omitted, and the plasma chamber18may have an extraction aperture formed in a sidewall thereof. The present disclosure is not limited in this regard.

Referring toFIGS.3A and3B, an alternative embodiment of the nozzle20is shown, wherein the nozzle20includes a plurality of vertically oriented cross members42disposed in a parallel, spaced apart relationship across the width of the aperture40. The cross members42may facilitate further funneling and channeling of the free radicals exiting the plasma chamber18relative to the embodiment of the nozzle20shown inFIGS.2A and2B. Referring toFIG.4, an alternative embodiment of the system10is shown wherein a barrier46defining a secondary aperture48is disposed between the plasma chamber18and the substrate24, with the secondary aperture48located in the path of the ribbon beam32. The secondary aperture48may operate to further collimate, or “re-collimate,” the ribbon beam32at a location nearer the substrate24than the aperture40(also referred to hereinafter as “the primary aperture40”), thus improving collimation of the ribbon beam32relative to the embodiment of the system10show inFIG.1.

Referring back toFIG.1, the platen22may be rotatable and movable for pivoting and scanning the substrate24relative to the plasma chamber18as indicated by arrows50and52. Additionally or alternatively, the plasma chamber18may be rotatable about its long axis as indicated by the arrow54. Thus, the collimated, free radical-containing ribbon beam32may be projected onto the substrate24at various oblique angles in a highly directional, anisotropic manner to deposit films on specific sides and/or portions of surface features (e.g., trenches, fins, etc.) of the substrate24while keeping other sides and/or portions of such surface features free of such depositions. In a non-limiting example, the movement and/or rotation of the platen22and/or the plasma chamber18may facilitate projecting the ribbon beam32onto the substrate24at angles in a range of 30 degrees to 80 degrees relative to a surface of the platen22with angle spreads in a range of +/−5 degrees to +/−30 degrees.

For example,FIG.5depicts a directional deposition of a thin film62on a set of patterned features64(e.g., fins, castellations, etc.), where the film62is deposited just on right sidewalls and upper surfaces of the patterned features64by directing the ribbon beam32toward the patterned features64from the upper right of the figure. The left sidewalls and floors between the patterned features64, being shielded/shadowed by the right sidewalls and upper surfaces of the patterned features64, are kept free of deposition.

In various embodiments, the system10may further include a bias supply70coupled to the plasma chamber18and the process chamber14. The bias supply70may selectively apply a voltage difference between the plasma chamber18and the substrate24for extracting ions from the plasma chamber18via the nozzle20, making the ribbon beam32rich in free radicals and in ions. The ions in the ribbon beam32may increase the affinity of the substrate surface with respect to the free radicals in the ribbon beam32, thus enhancing thin film deposition. In various embodiments, the system10may be operated in an “ion beam mode,” wherein the bias supply70is activated/implemented to extract ions from the plasma chamber18and to provide an ion rich ribbon beam32, and a “radical mode,” wherein the bias supply70is deactivated or otherwise not used to extract ions from the plasma chamber18to produce a ribbon beam rich in free radicals and not rich in ions.

Referring toFIG.6, a flow diagram illustrating an exemplary method for operating the above-described system10in accordance with the present disclosure is shown. The method will now be described in conjunction with the illustrations of the system10shown inFIGS.1-4.

At block1000of the exemplary method, a gaseous species may be supplied to the plasma chamber18from the gas source30. The gaseous species may include one or more of SiH4, CH4, NH3, O2, N2, SiCl4, GeH4, Ar, WF6, etc. The present disclosure is not limited in this regard. At block1100of the method, the gaseous species in the plasma chamber18may be ignited to produce an energetic plasma16

At block1200of the exemplary method, a pressure differential may be established between the plasma chamber18and the process chamber14to extract a collimated ribbon beam32containing free radicals from the plasma chamber18, wherein the collimated ribbon beam32is directed toward a substrate24disposed on the platen22within the process chamber14. For example, the process chamber14may be maintained a first pressure, and the plasma chamber18may be maintained at a second pressure higher than the first pressure. In various examples, the first pressure in the process chamber may be in a range of 10−6torr to 10−2torr, and the second pressure in the plasma chamber18may be in a range of 1 millitorr to 1 torr. The present disclosure is not limited in this regard.

At block1300of the exemplary method, the ribbon beam32containing free radicals may be collimated and directed toward the substrate24. In a non-limiting example, the ribbon beam32containing free radicals may be extracted through the radially elongated nozzle20. The nozzle20may have an elongated profile and may define an aperture40having a width measured in a direction parallel to the X-axis (and parallel to a longitudinal axis of the plasma chamber18) of the illustrated Cartesian coordinate system shown inFIG.2B, and having a height measured in a direction parallel to the Y-axis of the illustrated Cartesian coordinate system. In various embodiments, an aspect ratio of the width of the aperture40relative to the height of the aperture40may be in a range of 12:1 to 60:1. In specific examples, the aperture40may have a width of 300 millimeters and a height in a range of 5 millimeters to 25 millimeters. The present disclosure is not limited in this regard. The aperture40may have a depth as measured in a direction parallel to the Z-axis of the illustrated Cartesian coordinate system. In various embodiments, the aperture40may have a depth in a range of 7 millimeters to 20 millimeters. In a particular embodiment, the aperture40may have a depth of 10 millimeters. The present disclosure is not limited in this regard. Thus, the radially-elongated nozzle20may funnel or channel free radicals exiting the plasma chamber18in the ribbon beam32, and may tend to collimate the free radicals and facilitate a long mean free path of the free radicals, where the free radicals (and the ribbon beam32generally) may otherwise tend to diverge after exiting the plasma chamber18. An intended directionality of the ribbon beam32may thus be preserved when used to selectively deposit a thin film on the substrate24.

In various embodiments, the nozzle20may be provided with a plurality of vertically oriented cross members42disposed in a parallel, spaced apart relationship across the width of the aperture40to facilitate further funneling and channeling of the free radicals exiting the plasma chamber18. In various embodiments, a barrier46defining a secondary aperture48may be disposed between the plasma chamber18and the substrate24, with the secondary aperture48located in the path of the ribbon beam32. The secondary aperture48may operate to direct and further collimate, or “re-collimate,” the ribbon beam32at a location nearer the substrate24than the aperture40(also referred to hereinafter as “the primary aperture40”), thus improving collimation of the ribbon beam32.

At block1400of the exemplary method, the platen22may be rotated and/or moved for pivoting and/or scanning the substrate24relative to the plasma chamber18as indicated by arrows50and52inFIG.1. Additionally, or alternatively, the plasma chamber18may be rotated about its long axis as indicated by the arrow54. Thus, the collimated, free radical-containing ribbon beam32may be projected onto the substrate24at various oblique angles in a highly directional, anisotropic manner to deposit films on specific sides and/or portions of surface features (e.g., trenches, fins, etc.) of the substrate24while keeping other sides and/or portions of such surface features free of such depositions.

At block1500of the exemplary method, the system10may be operated in an “ion beam” mode by activating the bias supply70to extract ions from the plasma chamber18to provide an ion rich ribbon beam32. At block1600of the method, the system10may be operated in a “radical mode” by deactivating (or not activating) the bias supply70to produce a ribbon beam rich in free radicals and not as rich in ions.

Those of ordinary skill in the art will appreciate numerous advantages provided by the system10and corresponding method described above. A first advantage is the ability to facilitate directionally-specific, anisotropic deposition on a target substrate (e.g., depositing at specific, oblique angles relative to a surface of a substrate for depositing films on specific sides and/or portions of surface features while keeping other sides and/or portions of such surface features free of such depositions). A second advantage provided by the system10and corresponding method of the present disclosure is the ability to be selectively perform directionally-specific, anisotropic deposition on a target substrate in either an “ion beam” mode by activating the bias supply70to extract ions from the plasma chamber18to provide an ion rich ribbon beam32, or a “radical mode” by deactivating (or not activating) the bias supply70to produce a ribbon beam rich in free radicals and not as rich in ions

The present disclosure is not to be limited in scope by the specific embodiments described herein. Indeed, other various embodiments of and modifications to the present disclosure, in addition to those described herein, will be apparent to those of ordinary skill in the art from the foregoing description and accompanying drawings. Thus, such other embodiments and modifications are intended to fall within the scope of the present disclosure. Furthermore, while the present disclosure has been described herein in the context of a particular implementation in a particular environment for a particular purpose, those of ordinary skill in the art will recognize its usefulness is not limited thereto. Embodiments of the present disclosure may be beneficially implemented in any number of environments for any number of purposes. Accordingly, the claims set forth below shall be construed in view of the full breadth and spirit of the present disclosure as described herein.