Patent Application
20100065761
The present invention is directed to ion implantation systems, and more particularly pertains to deflection optics in ion implantation systems.
Ion implanters are advantageous because they allow for precision with regard to the quantity or concentration of dopants implanted into a workpiece, as well as to the placement of dopants within the workpiece. In particular, ion implanters allow the dose and energy of implanted ions to be varied for given applications. Ion dose controls the concentration of implanted ions, where high current implanters are typically used for high dose implants, and medium current implanters are used for lower dose applications. Ion energy is used to control the junction depth or the depth to which ions are implanted into a semiconductor workpiece.
It can be appreciated that given the trend in the electronics industry to scale down electronic devices to produce smaller, yet more powerful devices (e.g., cell phones, digital cameras, etc.), that the semiconductors and integrated circuits (e.g., transistors, etc.) utilized in these devices are continually being reduced in size. The ability to “pack” more of these devices onto a single semiconductor substrate, or portion thereof (known as a die) also improves fabrication efficiency and yield. It can be appreciated that reducing the energy of the ion beam may allow implants to be performed to shallower depths to produce thinner devices and enhance packing densities. It can also be appreciated that increasing the dose in shallower implants can facilitate desired conductivity, and that beam current of lower energy ion beams may have to increase to facilitate increased packing densities. In other instances, it may be desirable to use a higher energy beam to selectively implant ions relatively deeply into the substrate, so as to create volumes with varying semiconducting properties (e.g., diodes) and/or to tailor the field distribution between different regions or devices in the substrate. Presently different tools (e.g., medium current vs. high current implanters) are used for these different applications.
It can be appreciated that it would be desirable at least for economic reasons to have a single ion implantation system perform a wide range of ion implants. However, low energy or high current implanters typically are made to have a short beam path, while high energy and medium current implanters typically have relatively longer beam paths. Low energy implanters are made short to, among other things, mitigate beam blow up, or the tendency for the beam to expand radially outwardly since it comprises like charged particles that repel one another. High energy implanters, on the other hand, comprise a stream of quickly moving particles that have substantial momentum. These particles have gained their momentum by passing thru one or several acceleration gaps which add to the length of the beam line. Furthermore, to modify the trajectory of particles that have acquired substantial momentum, a focusing element has to be relatively long to apply a sufficient focusing force. Thus, high energy beamlines are made relatively longer than low energy or high current beam lines. Accordingly, there is a need to provide an arrangement that allows the effective length of at least some components of an ion implantation system to be adjusted.
The following presents a simplified summary in order to provide a basic understanding of some aspects of the disclosure. This summary is not an extensive overview, and is intended neither to identify key or critical elements nor to delineate the scope of the claimed subject matter. Rather, its primary purpose is merely to present one or more concepts in a simplified form as a prelude to the more detailed description that is presented later.
An electric and/or magnetic deflection component suitable for use in an ion implantation system comprises multiple electrodes that can be selectively biased to cause an ion beam passing therethrough to bend, deflect, decontaminate, focus, accelerate, decelerate, converge and/or diverge. Since the electrodes can be selectively biased, and thus one or more of them can remain unbiased or off, the effective length of a deflection region of the beam path within the electric component can be selectively adjusted as desired, e.g., based upon beam properties, such as energy, dose, species, etc.
In one embodiment, an ion implantation system comprises an ion beam source for generating an ion beam and a component for mass resolving the ion beam. Additionally, the implantation system comprises at least one deflection component that is variably adjustable downstream of the mass resolving component for deflecting the beam to an effective length and an endstation located downstream of the deflection component and configured to support a workpiece that is to be implanted with ions by the ion beam. The deflection component comprises a first electrode, a second electrode defining a gap with the first electrode, and a biasing element for applying an electric voltage to at least one of the first and second electrodes. An electric field is developed between the first and second electrodes to deflect ions of the ion beam traveling through the gap. At least one of the first and second electrodes is segmented to create a plurality of electrode segments along the path of travel of the beam and each electrode segment can be independently biased for selectively controlling an effective length of the deflecting component.
In another embodiment, the implantation system comprises a measurement component configured to measure one or more beam characteristics and a controller operatively coupled to the measurement component, beam generating component, mass resolving component and deflection component and configured to adjust the operation of at least one of the beam generating component, mass resolving component and deflection component in response to measurements taken by the measurement component. The measurement component is configured to measure at least one of current, mass, voltage, and/or charge current. The ion beam may be deflected by the deflection component while concurrently being decelerated by the deflection component. Alternatively, the ion beam is deflected by the deflection component while concurrently being focused by the deflection component.
To the accomplishment of the foregoing and related ends, the following description and annexed drawings set forth in detail certain illustrative aspects and implementations. These are indicative of but a few of the various ways in which one or more aspects may be employed. Other aspects, advantages and novel features will become apparent from the following detailed description when considered in conjunction with the annexed drawings.
a-3c are illustrations depicting electrodes in a deflector as described herein.
The claimed subject matter is now described with reference to the drawings, wherein like reference numerals are used to refer to like elements throughout. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the claimed subject matter. It may be evident, however, that the claimed subject matter may be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form in order to facilitate describing the claimed subject matter.
The present invention pertains to a segmented deflector mechanism that provides for independently and spatially controlling an intensity and geometry of a deflection field as a function of at least one of: beam energy, current, voltage, mass, and/or charge. The segmented deflector mechanism can comprise a first electrode and a second electrode, at least one comprising electrode segments capable of being biased all together or as individually selected while other electrode segments of the deflector are held to a predetermined voltage (e.g., ground). By selectively biasing all, one, or some of the electrode segments an electric field can be maintained in order to tune the amount of deflection and distribution of beam plasma. In this manner, beam neutralization can be maintained while still deflecting a beam of high energy and/or low energy. The present invention is applicable to various types of beam implantation systems, such as both pencil beam and ribbon beam implantation systems.
To generate the ions, a gas of a dopant material (not shown) to be ionized is located within a generation chamber 121 of the ion source 120. The dopant gas can, for example, be fed into the chamber 121 from a gas source (not shown). In addition to the power supply 122, it will be appreciated that any number of suitable mechanisms (not shown) can be used to excite free electrons within the ion generation chamber 121, such as RF or microwave excitation sources, electron beam injection sources, electromagnetic sources and/or a cathode which creates an arc discharge within the chamber, for example. The excited electrons collide with the dopant gas molecules and ions are generated thereby. Generally, positive ions are generated although the disclosure herein is applicable to systems wherein negative ions are generated as well. The ions are controllably extracted through a slit 118 in the chamber 121 by an ion extraction assembly 123, which comprises a plurality of extraction and/or suppression electrodes 125a-125b. The extraction assembly 123 can include, for example, a separate extraction power supply (not shown) to bias the extraction and/or suppression electrodes 125a-125b to accelerate the ions from the generation chamber 121.
In one example, the beamline assembly has a beam guide, a mass analyzer, a scanning system, and at least one deflector. In another example, as shown in
The scanning system 135 in the illustrated example of
In one example, the scanned beam 124 is then passed through a particle trap (not shown) to decontaminate the beam, which may contain a number of different traps using electric and/or magnetic fields. In another example, the scanned beam is passed through a parallelizer 139, which comprises two dipole magnets 139a, 139b in the illustrated example.
It will be appreciated that different types of end stations 116 may be employed in the implanter 110. The end station 116 in the illustrated example is a “serial” type end station that supports a single workpiece 130 along the beam path for implantation. A dosimetry system 152 can also be included in the end station 116 near the workpiece location for calibration measurements prior to (and also throughout) implantation operations. In one embodiment, during calibration, the beam 124 passes through the dosimetry system 152. The dosimetry system 152 includes one or more profilers 156 that may traverse a profiler path 158, thereby measuring the profile of the beam. The profiler 156 may comprise a current density sensor, such as a Faraday cup, for example, and the dosimetry system can, in one example, measure both beam density distribution and angular distribution as described in R. D. Rathmell, D. E. Kamenitsa, M. I. King, and A. M. Ray, IEEE Proc. of Intl. Conf. on Ion Implantation Tech., Kyoto, Japan 392-395 (1998), U.S. Pat. No. 7,329,882 to Rathmell et al. entitled ION IMPLANTATION BEAM ANGLE CALIBRATION and U.S. Pat. No. 7,361,914 to Rathmell et al. entitled MEANS TO ESTABLISH ORIENTATION OF ION BEAM TO WAFER AND CORRECT ANGLE ERRORS the entirety of which are hereby incorporated herein by reference.
The dosimetry system 152 is operably coupled to a control system 154 to receive command signals therefrom and to provide measurement values thereto. For example, the control system 154, which may comprise a computer, microprocessor, etc., may be operable to take measurement values from the dosimetry system 152 and calculate a current density, an energy level and/or an average angle distribution of the beam, for example. The control system 154 can likewise be operatively coupled to the terminal 112 from which the beam of ions is generated, as well as the mass analyzer 126 of the beamline assembly 114, parallelizer 139, and the deflectors of 136, 138 and 157 (e.g., via power supplies 149, 150, 159, 160).
In one embodiment, one or more deflection stages 157 can be located downstream of the mass analyzer 126. Up to this point in the system 110, the beam 124 is generally transported at a relatively high energy level, which mitigates the propensity for beam blow up, especially where beam density is elevated such as at the resolving aperture 134. Similar to the ion extraction assembly 123, scanning element 136 and focusing and steering element 138, the deflection stage 157 comprises one or more electrodes 157a, 157b operable to decelerate the beam 124.
It will be appreciated that while two electrodes 125a and 125b, 136a and 136b, 138a and 138b and 157a and 157b are respectively illustrated in the exemplary ion extraction assembly 123, scanning element 136, deflection component 138 and deflection stage 157, that these elements 123,136,138 and 157 may comprise any suitable number of electrodes arranged and biased to accelerate and/or decelerate ions, as well as to focus, bend, deflect, converge, diverge, scan, parallelize and/or decontaminate the ion beam 124 in a manner substantially similar to that provided in U.S. Pat. No. 6,777,696 to Rathmell et al. the entirety of which is hereby incorporated herein by reference. Additionally, the focusing and steering element 138 may comprise electric deflection plates (e.g., one or more pairs thereof), as well as an Einzel lens, quadrupoles and/or other focusing elements to focus the ion beam. Although not necessary it can be advantageous to apply voltages to the deflecting plates within element 138 so that they average to zero, the effect of which is to avoid having to introduce an additional Einzel lens to mitigate the distortion of the focusing aspect of element 138. It will be appreciated that “steering” the ion beam is a function of the dimensions of deflection electrodes of 138a, 138b and the steering voltages applied thereto, among other things, as the beam direction is proportional to the steering voltages and the length of the plates, and inversely proportional to the beam energy.
By way of further example, it will be appreciated that the deflection component 157 of
In one embodiment, the deflector 157 can comprise multiple electrodes such as a first electrode 157a and a second electrode 157b that can comprise at least one upper electrode and at least one lower electrode respectively that has a deflection region of a certain effective length (not shown) and can be selectively biased to bend, deflect, converge, diverge, focus, accelerate, decelerate, and/or decontaminate the ion beam 124. The deflection region of the deflector 157 comprises the region where electric fields act upon the beam in a manner operable to induce bending of the beam. For example, the effective length of the deflection region can vary depending upon the amount of electric field space produced, as will be discussed further infra. A power supply 160 can be operatively coupled to the deflection component 157 to selectively bias the electrodes. It will be appreciated that the effective length of the deflection region of deflector 157 can be adjusted by selectively biasing the electrodes. For example, the effective length of the deflector 157 can be decreased by biasing one or more of the electrodes to the same electric potential as the surrounding of the implanter (e.g., zero or ground), which essentially deactivates or turns off those electrodes. Similarly, the effective length of the deflector 157 can be increased by biasing the electrodes to a deflecting potential (typically different from zero or ground) to thereby enlarge the electric field generated by the electrodes therein.
Turning to
In the illustrated example, the ion beam 124 passing through an aperture 210 can be deflected from the axis 212 by an angle θ′ 227 which may be between about 7 and 20 degrees, about 12 degrees for example, and can be focused at a point 228 downstream from the aperture 210.
a illustrates one embodiment of a segmented deflection mechanism 336 that can be representative of the deflection component 226 of
The electrode segments of the segmented deflection mechanism can each be independently biased for selectively controlling an effective length of the deflecting component. The deflection mechanism 336 can be coupled to a controller 316 and a measurement component 314 configured to measure one or more beam characteristics that can comprise at least one of energy, voltage, current, current density, mass, charge, and species of the beam 324. The controller can be operatively coupled to the measurement component, beam generating component, mass resolving component and/or deflection component and configured to adjust the operation of at least one of the beam generating component, mass resolving component and deflection component in response to measurements taken by the measurement component.
In one embodiment, illustrated in
Alternatively, any one of the electrode segments depicted can be independently biased for selectively controlling the effective length 318 of the deflection region 320. This can be useful when trying to keep the deflection region 320 where the electric field acts upon the beam as short as possible by not using as many positive voltages, for example. In other words, a number of electrode segments that are less than all of the segments of an upper or lower electrode (e.g., one out of three, two out of three) can be utilized for low energy beams to make the electric field space (which can strip away plasma from the beam) to be physically shorter. Similar to
c illustrates an embodiment where high energy beams can be utilized. In one embodiment, all three of the upper electrode segments can be biased to high voltages V1 and the three lower electrode segments to lower voltages V2. This can effectively strip beam plasma, and therefore, provide an even longer effective length 318 of the deflection region 320. Once again, the effective length 318 by which the deflection region 320 interacts with the ion beam is approximated due to the various non-linear geometries of interacting electric field lines and thus an approximate length is depicted; however, the effective length may take on various geometries and lengths in relation to the amount of biasing and selectivity of the individual electrode segments. For example, in
Other biasing configurations can be utilized as well where individual electrode segments of the segmented deflection mechanism are selectively biased. For example, all the electrode segments can be grounded except the middle lower electrode 304, which may be biased negative. In this case, the bending action is provided still because the lower negative electrode is attracting the ion beam. This can be provided for low energy beams in order to get a better distribution of beam plasma to promote ion beam neutralization. Other electrode segments of the deflection component can be configured to be selectively biased independently of one another. This can be performed through a power source (not shown) coupled to a controller 316 that has received measurements from the measurement component 316 of the beam based on at least one of energy, current, mass and charge.
Turning to
The method 400 begins at 410 where an ion beam that is utilized to implant ions into a workpiece is generated in the ion implantation system. The beam is, for example, established to have a desired dopant species, energy and/or current. The method then advances to 412 where one or more implantation characteristics are measured, such as implant angle, beam species, beam energy, beam dose, etc. Such characteristics may be measured with a dosimetry system as described above, for example. More particularly, a dosimetry system may be utilized that determines the current density of the beam, for example. The measured characteristics can be compared to desired values stored in a control component of the system, for example, to ascertain what adjustments, if any, need to be made to obtain the desired result.
The operation of the system is then adjusted at 414 based upon the measurements taken at 412. For example, any one or more of the electrode segments of a deflection component may be adjusted as described above to obtain desired ion implantation. Bias voltages, for example, to be applied to one or more electrodes to achieve a desired effective length, degree of deflection and/or level of acceleration/deceleration can be obtained, for example. The method 400 is illustrated as ending thereafter, but may in fact continue to cycle through or be repeated to achieve desired ion implantation.
Although the disclosure has been shown and described with respect to one or more implementations, equivalent alterations and modifications will occur to others skilled in the art based upon a reading and understanding of this specification and the annexed drawings. The disclosure includes all such modifications and alterations and is limited only by the scope of the following claims. In particular regard to the various functions performed by the above described components (assemblies, elements, devices, circuits, etc.), the terms (including a reference to a “means”) used to describe such components are intended to correspond, unless otherwise indicated, to any component which performs the specified function of the described component (i.e., that is functionally equivalent), even though not structurally equivalent to the disclosed structure which performs the function in the herein illustrated exemplary implementations. In addition, while a particular feature may have been disclosed with respect to only one of several implementations, such feature may be combined with one or more other features of the other implementations as may be desired and advantageous for any given or particular application. Furthermore, to the extent that the terms “includes”, “having”, “has”, “with”, or variants thereof are used in either the detailed description or the claims, such terms are intended to be inclusive in a manner similar to the term “comprising.” Also, “exemplary” as utilized herein merely means an example, rather than the best.
