PLASMA SOURCE WITH MULTIPLE EXTRACTION APERTURES

A plasma source having two extraction apertures is disclosed. The extraction apertures are not co-planar, allowing a scanned workpiece to be impacted by particles or ions from two different directions during a single scan pass. The chamber housing of the plasma source may be cylindrical or may have a polygonal cross-section. In some embodiments, external plates are mounted to the chamber housing to provide defining apertures which serve to further collimate the particles or ions that exit each extraction aperture. Various different plasma generators may be utilized with this plasma source, including internal antenna elements, external coils, cathodes, filaments and other mechanisms.

FIELD

Embodiments of the present disclosure relate to a plasma source with multiple extraction apertures.

BACKGROUND

The fabrication of a semiconductor device involves a plurality of discrete and complex processes. Accordingly, many prior art designs were optimized for ion implantation. Recently, in addition to ion implantation, there has been a transition to other processes, such as deposition, etching and other material changing processes, such as amorphization.

Angled processes refer to those in which the beam strikes the substrate at a non-zero angle. For consistency, an angle of 0° is defined as one in which the beam strikes the substrate at an angle perpendicular to the surface of the substrate. Angled beams have many applications. For example, they may be used to implant a sidewall of a fin structure or a trench. Angled beams may also be used for etching processes, deposition processes and other applications. Previous designed have proven to yield angles which were typically less than 45° and had low flux and a broad distribution of angles.

In some systems, a plasma source directs a beam toward the workpiece at an non-zero angle. However, in some applications, it is beneficial to perform symmetric processing of the workpiece. For example, it may be beneficial to treat a 3D feature on both sides with a beam of ions or radicals. Currently this is done by scanning the workpiece through the angled beam, and after the entire workpiece has been processed, the workpiece is rotated 180° and then scanned again.

This process is effective but may be time consuming as it uses two scanning passes of the workpiece with a 180° rotation between these two passes.

Additionally, there is value in achieving high angles, such as greater than 60°, with a small distribution of angles and high flux, which may be ions and/or radicals.

Therefore, it would be advantageous if there was a system that had multiple extraction apertures, so that both surfaces of a 3D feature may be processed during a single scan. Further, it would be beneficial if this source was able to create large angles with a small distribution of angles and high flux.

SUMMARY

A plasma source having two extraction apertures is disclosed. The extraction apertures are not co-planar, allowing a scanned workpiece to be impacted by particles or ions from two different directions during a single scan pass. The chamber housing of the plasma source may be cylindrical or may have a polygonal cross-section. In some embodiments, external plates are mounted to the chamber housing to provide defining apertures which serve to further collimate the particles or ions that exit each extraction aperture. Various different plasma generators may be utilized with this plasma source, including internal antenna elements, external coils, cathodes, filaments and other mechanisms.

According to one embodiment, a plasma source is disclosed. The plasma source comprises a chamber housing defining a plasma chamber; and a plasma generator to create a plasma within the plasma chamber; wherein a first portion of the chamber housing includes a first extraction aperture; and a second portion of the chamber housing includes a second extraction aperture, wherein the first portion and the second portion are not coplanar. In some embodiments, a first line perpendicular to the first portion and passing through the first extraction aperture and a second line perpendicular to the second portion and passing through the second portion intersect within the plasma chamber. In certain embodiments, the first line and the second line form an angle of between 30 and 150 degrees. In certain embodiments, the first line and the second line intersect at a center of the plasma chamber. In some embodiments, the plasma source comprises a first external plate having a first defining aperture disposed outside the plasma chamber proximate the first extraction aperture, and a second external plate having a second defining aperture disposed outside the plasma chamber proximate the second extraction aperture, wherein the first external plate and the second external plate are biased at a same voltage as the chamber housing, such that the first defining aperture narrows a path of travel for particles exiting the first extraction aperture and the second defining aperture narrows a path of travel for particles exiting the second extraction aperture. In some embodiments, the plasma source comprises a first external plate having a first electrode aperture disposed outside the plasma chamber proximate the first extraction aperture, and a second external plate having a second electrode extraction aperture, wherein the first external plate and the second external plate are negatively biased relative to the chamber housing using an electrode power supply so as to attract ions through the first extraction aperture and the second extraction aperture. In certain embodiments, the plasma source comprises at least a second set of external plates, wherein the second set of external plates are disposed outside the first external plate and second external plate, respectively, and are biased at a different voltage than the first external plate and the second external plate. In some embodiments, the chamber housing comprises a cylindrical body, wherein the first extraction aperture and the second extraction aperture are disposed on the cylindrical body. In some embodiments, the chamber housing comprises a body having a polygonal cross-section, and the first extraction aperture and the second extraction aperture are disposed on different sides of the polygon. In certain embodiments, the different sides are adjacent. In certain embodiments, the different sides are not adjacent.

According to another embodiment, a processing system is disclosed. The processing system comprises the plasma source described above and a workpiece holder, movable in a scanning direction, wherein a workpiece disposed on the workpiece holder is exposed to particles or ions exiting the first extraction aperture at some locations along the scanning direction, and is exposed to particles or ions exiting the second extraction aperture at other locations along the scanning direction.

According to another embodiment, a processing system is disclosed. The processing system comprises a plasma source, comprising: a chamber housing including a cylindrical body and two ends that define a plasma chamber; a first extraction aperture and a second extraction aperture disposed along the cylindrical body; and at least one antenna element disposed within the plasma chamber to generate a plasma; a scan motor; and a workpiece holder, movable in a scanning direction by the scan motor, wherein a workpiece disposed on the workpiece holder is exposed to particles or ions exiting the first extraction aperture at some locations along the scanning direction, and is exposed to particles or ions exiting the second extraction aperture at other locations along the scanning direction. In some embodiments, a first line perpendicular to the cylindrical body and passing through the first extraction aperture and a second line perpendicular to the cylindrical body and passing through the second portion intersect within the plasma chamber and form an angle of between 30° and 150°. In certain embodiments, the at least one antenna element comprises three antenna elements, wherein the three antenna elements are arranged such that a peak plasma density is located at an intersection of the first line and the second line. In some embodiments, the processing system comprises a first external plate having a first defining aperture disposed outside the plasma chamber proximate the first extraction aperture, and a second external plate having a second defining aperture disposed outside the plasma chamber proximate the second extraction aperture, wherein the first external plate and the second external plate are biased at a same voltage as the chamber housing, such that the first defining aperture narrows a path of travel for particles exiting the first extraction aperture and the second defining aperture narrows a path of travel for particles exiting the second extraction aperture. In some embodiments, the processing system comprises a first external plate having a first electrode aperture disposed outside the plasma chamber proximate the first extraction aperture, and a second external plate having a second electrode extraction aperture, wherein the first external plate and the second external plate are negatively biased relative to the chamber housing using an electrode power supply so as to attract ions through the first extraction aperture and the second extraction aperture. In certain embodiments, the processing system comprises at least a second set of external plates, wherein the second set of external plates are disposed outside the first external plate and second external plate, respectively, and are biased at a different voltage than the first external plate and the second external plate.

According to another embodiment, a processing system is disclosed. The processing system comprises a plasma source, comprising: a chamber housing including a body having a polygonal cross-section and two ends that define a plasma chamber; a first extraction aperture and a second extraction aperture disposed on two different sides of the body; and at least one antenna element disposed within the plasma chamber to generate a plasma; a scan motor; and a workpiece holder, movable in a scanning direction by the scan motor, wherein a workpiece disposed on the workpiece holder is exposed to particles or ions exiting the first extraction aperture at some locations along the scanning direction, and is exposed to particles or ions exiting the second extraction aperture at other locations along the scanning direction.

DETAILED DESCRIPTION

As described above, angled semiconductor processes, such as angled implant, deposition and etch processes are becoming increasing common in the semiconductor industry. Therefore, a system that allows 3D features of a workpiece to be processed on both sides during a single scanning pass, would be very beneficial.

FIG.1shows a cross-sectional view of a plasma source10having multiple extraction apertures which allows for the extraction of two beams of angled ions and/or neutral particles according to one embodiment. The plasma source10includes a chamber housing100, having a cylindrical body, and two closed ends, which define a plasma chamber101. The two ends are parallel to the surface of the page and are not shown for clarity. The body of the chamber housing100has an inner surface having an inner diameter and an outer surface having an outer diameter. Additionally, the chamber housing100also includes a first extraction aperture110aand a second extraction aperture110bdisposed along the perimeter of the cylindrical body. Each extraction aperture110a,110bis an opening in the chamber housing100and has a width, which is the direction between the two ends. Each extraction aperture110a,110balso has a height, which is in the circumferential direction. In some embodiments, the extraction apertures110a,110bextend across the entire width of the chamber housing100. In other embodiments, the extraction apertures110a,110bmay not extend to the two ends.

A first line161amay be formed between the center of the plasma chamber101and the center of the first extraction aperture110a. This first line161amay be perpendicular to the chamber housing100at the position where it passes through the first extraction aperture110a. A second line161bmay be formed between the center of the plasma chamber101and the center of the second extraction aperture110b. Similarly, this second line161bmay be perpendicular to the chamber housing100at the position where it passes through the second extraction aperture110b. The angle, θ, formed between the first line161aand the second line161brepresents a difference in the extraction angles between the two extraction apertures110a,110b. In some embodiments, this angle, θ, may be between 30° and 150°. Assuming that the plasma source10is configured such that the tilt angles are complementary, this allows tilt angles between 15° and 75°. In other words, whileFIG.1shows the tilt angles as 45° and −45°, the extraction apertures110a,110bmay be arranged such that the tilt angles are larger or smaller than this value. Note that while two extraction apertures are shown, additional extraction apertures may be added.

The plasma source10may also include one or more liners disposed within the plasma chamber101along the interior wall of the chamber housing100. In some embodiments, one or more magnets140may be disposed in the chamber housing100. The plasma source10also includes a gas inlet150, which is in communication with a gas source155.

In this embodiment, one or more antenna elements160a,160bare disposed within the plasma chamber101. In some embodiments, the antenna elements160a,160bare constructed of a conductive material, such as a metal, and may be protected by an insulating cover165. The insulating cover165may be quartz in some embodiments. The antenna elements160a,160bmay be powered using an RF power supply167. These antenna elements160a,160bserve as a plasma generator. Note that the disclosure is not limited to this plasma generator. For example, in other embodiments, the plasma generator may include a coil disposed outside the chamber housing100, a cathode disposed within the plasma chamber101, a filament disposed within the plasma chamber101, or another plasma generator.

In one particular embodiment, there may be two antenna elements160a,160b, as shown inFIG.1, wherein the current flows in opposite directions through the two antenna elements160a,160b.

In another embodiment, shown inFIG.2, the plasma source11may include three antenna elements, where current flows through two antenna elements160a,160bin one direction and through the third antenna element160cin the opposite direction. As shown inFIG.2, the third antenna element160cmay be located along a third line161cthat is equidistant from the two extraction apertures110a,110b. Further, the other two antenna elements160a,160bmay be configured to center the peak plasma density at the center of the plasma chamber101.

Additionally, in certain embodiments, such as those shown inFIGS.1-4, two external plates170a,170bare affixed to the chamber housing100. Each of these external plates170a,170bmay include a respective aperture, referred to as a defining aperture175a,175b. Each defining aperture175a,175bis aligned with a respective extraction aperture110a,110b. The defining apertures175a,175bprovide additional collimation of the particles that exit the extraction apertures110a,110b.

In some embodiments, the external plates170a,170bare electrically connected to the chamber housing100. In n these embodiments, the external plates170a,170bdo not attract charged ions from the plasma chamber101. Rather, the defining apertures175a,175bserve to confine the path of neutral particles and radicals that are extracted from the plasma chamber101.

In other embodiments, such as that shown inFIG.5, the external plates176a,176bmay be electrically isolated from the chamber housing100, such as through the use of an insulator. The first external plate176ais disposed outside the first extraction aperture110aand the second external plate176bis disposed outside the second extraction aperture110b. In these embodiments, a voltage different from the voltage applied to the chamber housing100may be applied to the external plates176a,176b. In certain embodiments, the external plates176a,176bmay be negatively biased relative to the chamber housing100using electrode power supply178. This negative bias is applied so as to attract positive ions from the plasma chamber101. Thus, in this embodiment, the external plates176a,176bserve as extraction electrodes. Furthermore, in some embodiments, a second set of external plates177a,177bmay be disposed beyond the external plates176a,176b, respectively. This second set of external plates177a,177bmay be positively biased or grounded and may serve as suppression electrodes. Additional sets of electrodes may also be present. The external plates are aligned such that an electrode aperture179a,179bis created and is aligned with the respective extraction aperture110a,110b.

The workpiece180is disposed on a workpiece holder190. The workpiece holder190may be scanned in a scanning direction191using scan motor195.

Thus, in operation, one or more processing gasses are supplied from the gas source155to the plasma chamber101through the gas inlet150. RF power from the RF power supply167is provided to the antenna elements160. The antenna elements160create RF energy, which causes the processing gasses within the plasma chamber101to become ionized and form a plasma. Magnets140serve to direct the plasma toward the center of the plasma chamber101and away from the chamber housing100.

In the embodiment shown inFIG.1where the external plates170a,170bare electrically connected to the chamber housing100, particles, which may be neutrals or radicals, drift out of the plasma chamber101through the extraction apertures110a,110b. Some of these particles then pass through the defining apertures175a,175band proceed toward the workpiece180. Through use of the defining apertures, a more collimated beam of particles may be created.

In the embodiment shown inFIG.5where the external plates176a,176bare electrically biased separate from the chamber housing100, ions are drawn through the extraction apertures110a,110bby the voltage applied to the external plates176a,176b. These ions then pass through the electrode apertures179a,179band proceed toward the workpiece180.

The workpiece180is scanned in the scanning direction191. The scanning direction191is perpendicular to the width of the extracted beams. Note that, at some locations along the scanning direction191, the workpiece180is exposed to the particles or ions exiting the first extraction aperture110a. As the workpiece180continues along scanning direction191, there are other locations along the scanning direction191where the workpiece180is exposed to the particles or ions exiting the second extraction aperture110b. Thus, the entire workpiece180is exposed to both beams without rotating or otherwise reorienting the workpiece180.

Thus, in this embodiment, the plasma source has a chamber housing100that includes a cylindrical body and two ends, which define a plasma chamber101. The cylindrical body includes two or more extraction apertures110a,110bthat are positioned along the circumferential direction. A plasma generator, such as antenna elements, is used to generate a plasma within the plasma chamber101. The extraction apertures110a,110bmay be separated by between 30° and 150°. Further, external plates170a,170bmay be disposed outside the extraction apertures110a,110bto further collimate the ions and/or particles exiting the extraction apertures110a,110b.

WhileFIGS.1-2and5show a plasma source with a cylindrical body, other embodiments are also possible.FIG.3shows a plasma source12that includes a chamber housing102that includes a body having a hexagonal cross-section and two ends. In this embodiment, the extraction apertures110a,110bare disposed on two adjacent sides of the body. The angle between these two adjacent sides of the body determines the two tilt angles. For example,FIG.3shows a body having a cross-section of a regular hexagon, and thus, the angle, θ, between the first line161aand the second line161bis 60°, so the tilt angles are 30° and −30°. However, the angle between these two sides may be changed to achieve a different tilt angle. Further, whileFIG.3shows three antenna elements160a,160b,160cit is understood that a different number of antenna elements (such as is shown inFIG.1) may also be employed. Further, the antenna elements160a,160b,160cmay be replaced with a different plasma generator as noted earlier. The rest of the plasma source12may be as described above. Further, whileFIG.3shows the extraction apertures disposed on adjacent sides of the body, it is understood that the extraction apertures may be disposed on any two sides. Further, whileFIG.3shows the external plates170a,170belectrically connected to the chamber housing102, it is understood that the external plates176a,176band the electrode power supply178shown inFIG.5may be utilized with the chamber housing102ofFIG.3.

FIG.4shows a plasma source13having a chamber housing103that has a body having an octagonal cross-section and two ends. In this embodiment, the first extraction aperture110aand second extraction aperture110bare not disposed on adjacent sides of the chamber housing103. Rather, there is a side between the two sides that include the extraction apertures. Thus, if the body is a regular octagon, the angle, θ, between the first line161aand the second line161bis 90°, so the tilt angles are −45° and 45°. However, the angle between these two sides may be changed to achieve a different tilt angle. Further, whileFIG.4shows three antenna elements160a,160b,160c, it is understood that a different number of antenna elements (such as is shown inFIG.1) may also be employed. Further, the antenna elements160a,160b,160cmay be replaced with a different plasma generator as noted earlier. The rest of the plasma source13may be as described above. Further, whileFIG.4shows the external plates170a,170belectrically connected to the chamber housing103, it is understood that the external plates176a,176band electrode power supply178shown inFIG.5may be utilized with the chamber housing103ofFIG.4.

Note that if the embodiment shown inFIG.3is modified such that there is a side between the two sides that include the extraction apertures, the tilt angles become −60° and 60°. Further, note that if the embodiment ofFIG.4is modified such that there are two sides between the sides that include the extraction apertures, the tilt angles become −67.5° and 67.5°.

Further, as is clear from the above, the shape of the chamber housing may be any suitable shape. For example, the body of the chamber housing may be cylindrical. Alternatively, the body of the chamber housing may have a polygonal cross-section, where the two extraction apertures are located on different sides of the polygon. In some embodiments, these different sides may be adjacent to one another. However, in other embodiments, these different sides are not adjacent. For example, there may be one or more sides disposed between the sides that include the extraction apertures.

However, in all embodiments, the present disclosure utilizes two extraction apertures110a,110b, wherein these two extraction apertures are disposed on two portions of the chamber housing that are not co-planar. Further, as described above, the first line161aand the second line161bintersect within the plasma chamber101and form an angle that may be between 30° and 150°. In certain embodiments, the first line161aand the second line161bmeet at the center of the plasma chamber101. In some embodiments, the antenna elements160may be arranged so that the peak plasma density is located at the intersection of the first line161aand the second line161b.

The embodiments described above in the present application may have many advantages. First, as described above, conventionally, to perform two complementary directional processes, the workpiece is rotated by 180° after each scan pass. This is time consuming and reduces throughput. By incorporating multiple extraction apertures in the plasma source, two different directional processes may be performed during one scan pass. Further, by proper arrangement of the plasma generator, the flux exiting each extraction aperture110a,110bmay be greater than is typically achieved by existing systems. Further, the plasma sources described herein may be useful for various types of processes, including ion implantation, deposition, etching, and material changing processes, such as amorphization.