US-12626885-B2 - Wire or rod shaped extraction electrode optics

US12626885B2US 12626885 B2US12626885 B2US 12626885B2US-12626885-B2

Abstract

An electrode apparatus for an ion implantation system has a base plate having a base plate aperture and at least one securement region. A securement apparatus is associated with each securement region, and a plurality of electrode rods are selectively coupled to the base plate by the securement apparatus. The plurality of electrode rods have a predetermined shape to define an optical region that is associated with the base plate aperture. An electrical coupling electrically connects to the plurality of electrode rods and is configured to electrically connect to an electrical potential. The plurality of electrode rods have a predetermined shape configured to define a path of a charged particle passing between the plurality of electrode rods based on the electrical potential. The plurality of electrode rods can define a suppressor or ground electrode downstream of an extraction aperture of an ion source.

Inventors

Neil Colvin
Paul Silverstein
Joshua Abeshaus

Assignees

AXCELIS TECHNOLOGIES, INC.

Dates

Publication Date: 20260512
Application Date: 20221031

Claims (20)

1 . An electrode apparatus for an ion implantation system, the electrode apparatus comprising: a base plate having a base plate aperture defined therein, and wherein the base plate comprises at least one securement region; a securement apparatus associated with each of the at least one securement region; a plurality of electrode rods selectively fixedly coupled to the base plate via the securement apparatus, wherein the plurality of electrode rods have a predetermined shape to define an optical region therebetween, and wherein the optical region is associated with the base plate aperture, wherein each of the plurality of electrode rods respectively comprise an optical portion and one or more mounting portions, wherein the securement apparatus selectively engages the one or more mounting portions to fixedly locate the optical portion of each of the plurality of electrode rods at a predetermined position with respect to the base plate; and an electrical coupling, wherein the electrical coupling is electrically coupled to the plurality of electrode rods and configured to electrically connect to an electrical potential, and wherein the predetermined shape of the plurality of electrode rods is configured to define a path of an ion beam passing between the plurality of electrode rods based on the electrical potential, wherein the optical portion of each of the plurality of electrode rods has a curvilinear shape with respect to the path of the ion beam and wherein a portion of the one or more mounting portions has a shape that differs from the curvilinear shape.
2 . The electrode apparatus of claim 1 , wherein the one or more mounting portions are associated with a respective first end and second end of each of the plurality of electrode rods.
3 . The electrode apparatus of claim 2 , wherein the one or more mounting portions respectively comprise an elongate leg portion extending from the optical portion of each of the plurality of electrode rods.
4 . The electrode apparatus of claim 3 , wherein the base plate comprises a base hole configured to selectively receive the respective elongate leg portion of each of the plurality of electrode rods, wherein the securement apparatus comprises an electrode fastener associated with at least one elongate leg portion of each electrode rod, respectively, wherein the electrode fastener is configured to selectively secure the respective elongate leg portion to the base plate.
5 . The electrode apparatus of claim 4 , wherein the electrode fastener comprises a set screw.
6 . The electrode apparatus of claim 4 , wherein each respective base hole is a blind hole having a predetermined depth, wherein the predetermined depth defines the predetermined position of the optical portion of each of the plurality of electrode rods with respect to the base plate.
7 . The electrode apparatus of claim 3 , wherein the securement apparatus comprises a mounting plate, wherein the one or more mounting portions of each of the plurality of electrode rods are selectively coupled to the mounting plate, and wherein the mounting plate is selectively coupled to the base plate in the at least one securement region.
8 . The electrode apparatus of claim 7 , wherein the mounting plate comprises at least one mounting hole configured to respectively selectively receive one of the respective first end and second end of each of the plurality of electrode rods, wherein the securement apparatus comprises an electrode fastener associated with at least one elongate leg portion of each electrode rod, respectively, wherein the electrode fastener is configured to respectively selectively secure at least one elongate leg portion to the mounting plate, respectively, and wherein the securement apparatus further comprises at least one mounting plate fastener configured to selectively secure the mounting plate to the base plate.
9 . The electrode apparatus of claim 8 , wherein the base plate comprises at least one threaded base hole configured to respectively receive the at least one mounting plate fastener, wherein the at least one mounting plate fastener comprises a screw.
10 . The electrode apparatus of claim 9 , wherein the electrode fastener comprises a set screw.
11 . The electrode apparatus of claim 3 , wherein the securement apparatus comprises a clamp member having a central member and one or more cantilevered members separated from the central member by a respective one or more predetermined gaps, wherein the clamp member is configured to selectively control the respective one or more predetermined gaps to selectively position and secure each of the plurality of electrode rods respectively between the one or more cantilevered members and the central member.
12 . The electrode apparatus of claim 11 , wherein the clamp member further comprises one or more stop members configured to selectively contact the respective first end and second end of each of the plurality of electrode rods, thereby respectively controlling a position of each of the plurality of electrode rods with respect to the clamp member.
13 . The electrode apparatus of claim 1 , wherein the plurality of electrode rods are parallel to each other when viewed along the path of the ion beam.
14 . The electrode apparatus of claim 1 , wherein each of the plurality of electrode rods are comprised of one or more of a refractory metal or graphite, and wherein the base plate is comprised of one or more of a refractory metal or graphite.
15 . The electrode apparatus of claim 1 , wherein the plurality of electrode rods define a suppressor electrode positioned downstream of an extraction aperture of an ion source, wherein the electrical potential is a predetermined non-zero voltage.
16 . The electrode apparatus of claim 1 , wherein the plurality of electrode rods define a ground electrode, wherein the electrical potential is a source of electrical ground.
17 . The electrode apparatus of claim 1 , wherein the plurality of electrode rods are comprised of one of tungsten (W), tantalum (Ta), molybdenum (Mo) or graphite.
18 . An electrode assembly for controlling an ion beam in an ion implantation system, the electrode assembly comprising: a base plate comprising at least one securement region; one or more electrode rods having one or more predetermined shapes, wherein the one or more predetermined shapes comprise a mounting portion and a optical portion associated with a desired characteristic of the ion beam, and wherein the optical portion has a curvilinear shape, with respect to a path of the ion beam, that differs in shape from the mounting portion; and a securement apparatus configured to selectively fixedly couple the one or more electrode rods to the at least one securement region of the base plate, wherein the securement apparatus comprises a clamp member having a central member and one or more cantilevered members separated from the central member by a respective one or more predetermined gaps, wherein the clamp member is configured to selectively control the respective one or more predetermined gaps to selectively position and secure the one or more electrode rods respectively between the one or more cantilevered members and the central member.
19 . The electrode assembly of claim 18 , wherein the clamp member further comprises one or more stop members configured to selectively contact a respective end of the one or more electrode rods, thereby controlling a position of the one or more electrode rods, respectively.
20 . The electrode apparatus of claim 1 , wherein the optical portion of each of the plurality of electrode rods generally conforms to a contour of an extraction aperture of an ion source, and wherein the optical portion of each of the plurality of electrode rods is operable to control a shape of the ion beam.

Description

FIELD OF THE INVENTION The present invention relates generally to ion implantation systems and more specifically to an ion source having an ion source having extraction electrode optics that are rod-shaped to reduce cost and maintenance issues associated with replacement of the extraction electrode optics. BACKGROUND OF THE INVENTION In the manufacture of semiconductor devices and other ion related products, ion implantation systems are used to impart dopant elements into semiconductor wafers, display panels, or other types of workpieces. Typical ion implantation systems or ion implanters impact a workpiece with an ion beam utilizing a known recipe or process in order to produce n-type or p-type doped regions, or to form passivation layers in the workpiece. When used for doping semiconductors, the ion implantation system injects selected ion species to produce the desired extrinsic material. Typically, dopant atoms or molecules are ionized and isolated, sometimes accelerated or decelerated, formed into a beam, and implanted into a workpiece. The dopant ions physically bombard and enter the surface of the workpiece, and subsequently come to rest below the workpiece surface in the crystalline lattice structure thereof. Ion implantation has become the technology preferred by industry to dope semiconductors with impurities in the large-scale manufacture of integrated circuits. Ion dose and ion energy are the two most important variables used to define an implant step. Ion dose relates to the concentration of implanted ions for a given semiconductor material. Typically, high current implanters (generally greater than 10 milliamperes (mA) ion beam current) are used for high dose implants, while medium current implanters (generally capable of up to about 10 mA beam current) are used for lower dose applications. Ion energy is the dominant parameter used to control junction depth in semiconductor devices. The energy levels of the ions that make up the ion beam determine the degree of depth of the implanted ions. High energy processes such as those used to form retrograde wells in semiconductor devices require implants of up to a few million electron-volts (MeV), while shallow junctions may demand ultra low energy (ULE) levels below one thousand electron-volts (1 keV). A typical ion implanter comprises four sections or subsystems: (i) an ion source for generating an ion beam, (ii) an ion beam extraction system, (iii) a beamline including a mass analysis magnet for mass resolving the ion beam, and (iv) a target chamber which contains the semiconductor wafer or other substrate to be implanted by the ion beam. The continuing trend toward smaller and smaller semiconductor devices is driving beamline constructions to deliver high beam currents at low energies. High beam currents provide the desired dosage levels, while low energies permit shallow implants. Source/drain extensions in CMOS devices, for example, make it desirable for such a high current, low energy application. Ion sources in ion implanters typically generate an ion beam by ionizing a source gas containing a desired dopant element within an ion source chamber, and an extraction system extracts the ionized source gas in the form of an ion beam. The ionization process is effected by an electron beam, which may take the form of a thermionic emitter such as a thermally heated filament, or a radio frequency (RF) antenna. A thermionic emitter is typically electrically biased so that emitted electrons gain sufficient energy to ionize, while an RF antenna delivers a high energy RF signal into the source chamber to energize ambient electrons. The high-energy electrons thus ionize the source gas in the ion source chamber to generate desired ions. Examples of desired dopant ions produced from the source gas may include boron (B), phosphorous (P) or arsenic (As). In an ion source utilizing a thermionic emitter for ionization, the local emitter temperature typically exceeds 2500° C., and the source chamber being thermally irradiated by the emitter may attain temperatures on the order of 700° C. FIG. 1 illustrates a conventional extraction electrode system 10, whereby ions generated within an ion source 12 are extracted through a source aperture 14 to generally define an ion beam (not shown). The conventional extraction electrode system 10 comprises an extraction electrode 16 that is electrically biased with respect to the ion source 12 and a ground electrode 18 that is electrically grounded. Typically, the extraction electrode 16 electrode and the ground electrode 18 have a respective focusing slits 20, 22 that are defined in respective solid plate members 24, 26. In designing an ion implanter, it is desirable for the ion beam to accurately follow a desired predetermined beam path. The precise position of the extraction electrode 16 with respect to the source aperture 14, for example, is important to ensure that the ion beam follows the desired predetermined beam path. T