Patent Application
20050184253
The present invention relates generally to semiconductor processing systems, and more specifically to an apparatus and method for controlling a quality and precision of motion of a substrate during ion implantation.
In the semiconductor industry, various manufacturing processes are typically carried out on a substrate (e.g., a semiconductor wafer) in order to achieve various results on the substrate. Processes such as ion implantation, for example, can be performed in order to obtain a particular characteristic on or within the substrate, such as limiting a diffusivity of a dielectric layer on the substrate by implanting a specific type of ion. Conventionally, ion implantation processes are performed in either a batch process, wherein multiple substrates are processed simultaneously, or in a serial process, wherein a single substrate is individually processed. Traditional high-energy or high-current batch ion implanters, for example, are operable to achieve a short ion beam line, wherein a large number of wafers may be placed on a wheel or disk, and the wheel is simultaneously spun and radially translated through the ion beam, thus exposing all of the substrates surface area to the beam at various times throughout the process. Processing batches of substrates in such a manner, however, generally makes the ion implanter substantially large in size.
In a typical serial process, on the other hand, an ion beam is either scanned in a single axis across a stationary wafer, or the wafer is translated in one direction past a fan-shaped, or scanned ion beam. The process of scanning or shaping a uniform ion beam, however, generally requires a complex and/or long beam line, which is generally undesirable at low energies. Furthermore, a uniform translation and/or rotation of either the ion beam or the wafer is generally required in order to provide a uniform ion implantation across the wafer. However, such a uniform translation and/or rotation can be difficult to achieve, due, at least in part, to substantial inertial forces associated with moving the conventional devices and scan mechanisms during processing.
Therefore, a need exists for a device for scanning an ion beam across a substrate, wherein the substrate is uniformly translated and/or rotated with respect to the ion beam.
The present invention overcomes the limitations of the prior art. Consequently, the following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the invention. It is intended to neither identify key or critical elements of the invention nor delineate the scope of the invention. Its purpose is to present some concepts of the invention in a simplified form as a prelude to the more detailed description that is presented later.
The present invention is directed generally toward a scanning mechanism for processing a substrate, wherein the scanning mechanism further comprises a two-link rotary subsystem. According to one exemplary aspect of the invention, a base portion is provided, wherein a first link is rotatably coupled to the base portion by a first joint, and wherein the first link is operable to rotate in a first rotational direction about a first axis associated with the first joint. A second link is further rotatably coupled to the first link by a second joint spaced a predetermined distance from the first joint, and wherein the second link is further operable to rotate in a second rotational direction about a second axis associated with the second joint. The second link further comprises an end effector, wherein the end effector is further spaced the predetermined distance from the second joint.
According to another exemplary aspect of the invention, a first actuator and a second actuator are provided, wherein the first and second actuators are operable to respectively rotate the first link and the second link about the respective first axis and second axis. The first actuator, for example, is operable to continuously rotate the first link in the first rotational direction, and the second actuator is operable to continuously rotate the second link in the second rotational direction. According to one exemplary aspect, the first rotational direction and the second rotational direction are opposite one another, wherein the end effector is operable to oscillate in a generally linear first scan path. According to another exemplary aspect, the end effector is further coupled to the second link via a third joint, wherein the end effector is operable to rotate and/or tilt with respect to the second link.
In accordance with another exemplary aspect of the invention, the first link and the second link are of approximately equal length, wherein a continuous oscillatory motion along the first scan path is generally permitted, and wherein the first and second joints rotate in a single respective direction.
In accordance with still another exemplary aspect of the invention, a generally constant velocity of the end effector can be maintained in a predetermined range of motion along the first scan path, wherein a rotational velocity of the respective first link and second link is controlled, and wherein the rotational velocities are maintained at non-zero values throughout the movement of the end effector.
According to yet another exemplary aspect, a translation mechanism is further provided, wherein the base portion and associated rotary subsystem is further operable to translate along a second scan path, generally referred to as a slow scan axis, wherein the second scan path is generally perpendicular to the first scan path.
According to another exemplary aspect of the invention, a scanning system is provided, wherein a controller is operable to control the respective rotational velocity of the first link and second link such that the movement of the substrate within the predetermined range is maintained at a substantially constant value. Also, a method for scanning a substrate is provided, wherein the method comprises rotating the first link and second link in a predetermined manner, wherein the substrate is translated within the predetermined range along the first scan path at a generally constant velocity. Furthermore, the method comprises maintaining the respective rotational velocity of the first link and second link such that the rotational velocities do not cross zero velocity.
To the accomplishment of the foregoing and related ends, the invention comprises the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative embodiments of the invention. These embodiments are indicative, however, of a few of the various ways in which the principles of the invention may be employed. Other objects, advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the drawings.
The present invention is directed generally towards a scanning mechanism for moving a substrate relative to a beam. More particularly, the scanning mechanism limits the amount of inertial force seen by the substrate, wherein a motion of the scanning mechanism oscillates via a two-link rotary subsystem. Accordingly, the present invention will now be described with reference to the drawings, wherein like reference numerals are used to refer to like elements throughout. It should be understood that the description of these aspects are merely illustrative and that they should not be taken in a limiting sense. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be evident to one skilled in the art, however, that the present invention may be practiced without these specific details.
Referring now to the figures,
According to one example, the first link 115 is rotatably coupled to the base portion 105 via a first joint 125, wherein the first link is operable to continuously rotate about a first axis 127 in a first rotational direction 128 (e.g., the first link is operable rotate clockwise or counter-clockwise with respect to the first joint). The second link 120 is further rotatably coupled to the first link 115 via a second joint 130, wherein the second joint is spaced a predetermined distance L from the first joint 125. The second link is further operable to continuously rotate about a second axis 132 in a second rotational direction 133 (e.g., the second link is operable to rotate clockwise or counter-clockwise with respect to the second joint). The first link 115 and the second link 120, for example, are further operable to rotate in separate, yet generally parallel first and second planes (not shown), respectively, wherein the first and second planes are generally perpendicular to the respective first and second axes 127 and 132. Furthermore, the first link 115 and second link 120 are operable to continuously rotate 360° in a respective first rotational path 134 and second rotational path 135 about the respective first joint 125 and second joint 130.
According to one exemplary aspect of the invention, the first rotational direction 128 is generally opposite the second rotational direction 133, wherein an end effector 140 associated with the second link 120 is operable to linearly translate along a first scan path 142 associated with the predetermined movement of the first link 115 and the second link. The end effector 140, for example, is operably coupled to the second link 120 via a third joint 145 associated with the second link, wherein the third joint is spaced the predetermined distance L from the second joint 130. The third joint 145, for example, is operable to provide a rotation 147 of the end effector 140 about a third axis 148. Furthermore, according to another example, the third joint 145 is further operable to provide a tilt (not shown) of the end effector 140, wherein, in one example, the end effector is operable to tilt about one or more axes (not shown) which are generally parallel to the second plane (not shown).
The end effector 140, for example, is further operable to secure the substrate (not shown) thereto, wherein the movement of the end effector generally defines a movement of the substrate. The end effector 140, for example, may comprise an electrostatic chuck (ESC), wherein the ESC is operable to substantially clamp or maintain a position of the substrate with respect to the end effector. It should be noted that while an ESC is described as one example of the end effector 140, the end effector may comprise various other devices for maintaining a grip of a payload (e.g., the substrate), and all such devices are contemplated as falling within the scope of the present invention.
The predetermined movement of the first link 115 and second link 120, for example, can be further controlled in order to linearly oscillate the end effector 140 along the first scan path 142, wherein the substrate (not shown) can be moved in a predetermined manner with respect to the ion beam (e.g., an ion beam coincident with the first axis 127). A rotation of the third joint 145, for example, can be further controlled, wherein the end effector 140 is maintained in a generally constant rotational relation with the first scan path 142. It should be noted that the predetermined distance L separating the first joint 125 and second joint 130, as well as the second joint and third joint 145, provides a general congruity in link length when measured between the respective joints. Such a congruity in length of the first link 115 and second link 120, for example, generally provides various kinematic advantages, such as those which will be described hereafter.
Maintaining constant rotational directions 128 and 133 of the respective first link 115 and second link 120 can provide various mechanical and kinematic advantages associated with moving the end effector 140 along the generally straight first scan path 142. For example, during the oscillation of the end effector 140, a substantially constant velocity of the end effector 140 is generally desirable within a predetermined range of motion thereof.
As illustrated in
It should be therefore noted that while the rotational directions 128 and 133 remain constant (i.e., unchanged), the movement of the end effector 140 and substrate 165 oscillates along the first scan path 142, thus changing direction at the maximum positions 155 and 160. Such a change in direction of the end effector 140 (and hence, the substrate 165) is associated with a change in velocity and acceleration of the end effector and substrate. In ion implantation processes, for example, it is generally desirable for the end effector 140 to maintain a substantially constant velocity along the scan path 142 when the substrate 165 passes through an ion beam (not shown), such as an ion beam which is generally coincident with the first axis 127. Such a constant velocity provides for the substrate 165 to be generally evenly exposed to the ion beam throughout the movement through the ion beam. However, due to the oscillatory motion of the end effector 140, acceleration and deceleration of the end effector is inevitable; such as when the third joint 145 (e.g., associated with the end effector and substrate 165) approaches the maximum positions 155 and 160 at either extent of the linear oscillation. Such an acceleration and deceleration near the maximum positions 155 and 160 (e.g., during scan path turn-around), should be maintained at reasonable levels in order to minimize inertial forces and associated reaction forces transmitted to the base portion 105 of the scanning mechanism 100. Variations in velocity of the end effector 140 during exposure of the substrate 165 to the ion beam, for example, can lead to a non-uniform ion implantation across the substrate.
Therefore, a generally constant velocity is desired for a predetermined range 168 associated with the movement of the substrate 165 through the ion beam. For example, the predetermined range 168 is associated with the physical dimensions of the substrate 165 (e.g., twice a diameter of the substrate), such that the acceleration and deceleration of the end effector can be generally accommodated within the overshoot 167. Accordingly, once the substrate 165 completely passes through the ion beam, the acceleration and deceleration of the end effector 140 will not substantially affect an ion implantation process or dose uniformity across the substrate.
The scanning system 200 of
The general scheme of motion control of the present invention generally provides a smoothness of motion of the end effector 140, and can minimize velocity errors associated therewith. According to another example, the controller 225 further comprises an inverse kinematic model (not shown), wherein the articulated motion of the end effector 140 is derived for each joint 125 and 130 at each duty cycle. The controller 225, for example, is further operable to control each actuator 205 and 210 by calculating a feed forward, model-based complimentary torque for each respective joint 125 and 130 during each control duty cycle.
As discussed in the above example, the amount of power 230 and 235 provided to the respective first and second rotary actuators 205 and 210 is based, at least in part, on the positions sensed by the respective first and second sensing elements 215 and 220. Accordingly, the position of the end effector 140 of the scanning mechanism 100 can be controlled by controlling the amount of power provided to the first and second actuators 205 and 210, wherein the amount of power is further associated with a velocity and acceleration of the end effector along the first scan path 142 of
According to another exemplary aspect of the present invention, a rotational velocity profile and acceleration profile of the first and second links 115 and 120 of
According to another exemplary aspect of the invention, proper inverse kinematics techniques can be utilized to overcome singularities when the first and second links 115 and 120 of
According to still another exemplary aspect of the present invention,
As illustrated in
The scanning mechanism 100 (e.g., an articulated arm) of the present invention provides sufficient dexterity such that the scanning mechanism can further easily participate in material handling tasks. Such material handling tasks, for example, may comprise placing or transferring processed wafers to another transfer mechanism. Conversely, loading or picking of un-processed wafers can further be accomplished by mating with another transfer device.
In accordance with another exemplary aspect of the present invention, the scanning mechanism 100 can be further utilized in a process chamber (not shown) that is in state of high vacuum, wherein no mechanical components such as lubricated bearings or actuators are directly exposed to the environment. In order to achieve such ends, the joints of the mechanism 100, for example, are further provided with vacuum seals, such as Ferro-fluidic seals. It should be understood that any type of movable vacuum seal that provides an integrity of cleanliness of the process is contemplated as falling within the scope of the present invention. Therefore, the present invention is further operable to provide a motion generation and wafer scanning in a clean, vacuum environment.
Although the invention has been shown and described with respect to a certain preferred embodiment or embodiments, it is obvious that equivalent alterations and modifications will occur to others skilled in the art upon the reading and understanding of this specification and the annexed drawings. In particular regard to the various functions performed by the above described components (assemblies, 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 embodiments of the invention. In addition, while a particular feature of the invention may have been disclosed with respect to only one of several embodiments, such feature may be combined with one or more other features of the other embodiments as may be desired and advantageous for any given or particular application.
