Patent Document

BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     Embodiments of the invention generally relate to a physical vapor deposition chamber. 
     2. Description of the Related Art 
     Many semiconductor processes are typically performed in a vacuum environment. For example, physical vapor deposition (PVD) is generally performed in a sealed chamber having a pedestal for supporting the substrate disposed thereon. The pedestal typically includes a substrate support that has electrodes disposed therein to electrostatically hold the substrate against the substrate support during processing. A target generally comprised of a material to be deposited on the substrate is supported above the substrate, typically fastened to a top of the chamber. A plasma formed from a gas, such as argon, is supplied between the substrate and the target. The target is biased, causing ions within the plasma to be accelerated toward the target. Ions impacting the target cause material to become dislodged from the target. The dislodged material is attracted toward a substrate and deposits a film of material thereon. 
     Generally, two conditioning operations are performed in the PVD chamber to ensure process performance. A first conditioning process is known as burning-in the target. Target burn-in generally removes oxides and other contaminants from the surface of the target and is typically performed after the chamber has been exposed to atmosphere or idled for a period of time. During the burn-in process, a utility wafer or shutter disk is disposed on the substrate support to prevent deposition of target material on the support. The burn-in process generally comprises forming a plasma within the chamber and using that plasma to remove the surface layer of material from the target. 
     A second conditioning process is known as pasting. Pasting generally applies a covering over material deposited on chamber components during a conventional PVD process. For example, PVD application of titanium nitride generally results in a layer of titanium nitride on the PVD chamber surfaces. The titanium nitride layer is typically brittle and may flake off during subsequent processes. Pasting generally applies a layer of titanium over the titanium nitride layer. The titanium layer substantially prevents the underlying titanium nitride from flaking or peeling. Typically, the chamber is pasted at predetermined intervals, such as after every 25 substrates are processed using a conventional titanium nitride PVD process. As with target burn-in, a shutter disk is disposed on the substrate support to prevent deposition of target material thereon during the pasting process. 
     Additionally, in PVD processes where titanium and titanium nitride are sequentially applied in-situ, the target requires cleaning prior to each titanium deposition to remove nitrides that be present on the target from titanium nitride deposited on the prior substrate. Generally, target cleaning is similar to a burn-in process having a few second duration and includes protecting the substrate support with a shutter disk. 
     After completion of each burn-in, pasting and cleaning process, the shutter disk is rotated by a robotic arm disposed within the PVD chamber to a cleared position where the shutter disk does not interfere with the deposition process within the chamber. To center the position of the shutter disk, a sensor is employed on a shaft coupled to the robotic arm to detect the rotational position of the arm. 
     A problem with this arrangement for detecting the position of the shutter disk in the cleared position is that the sensor does not have the capability of confirming the relative position of the shutter disk to the robotic arm. For example, misalignment between the shutter disk and the robotic arm may result in a portion of the shutter disk remaining in the path of the ceramic substrate support. As the ceramic support is elevated into a process position, a portion of the substrate may contact the shutter disk, which may result in damage to the substrate or misalignment of the substrate on the ceramic support. Moreover, if the shutter disk comes in contact with the ceramic support, the ceramic support may become chipped or damaged and necessitate replacement. Additionally, if the shutter disk is not properly aligned on the robotic arm, the disk may be misaligned relative to the ceramic support during the burn-in and pasting process, thereby resulting in unwanted deposition on a portion of the ceramic support. Deposition material on the ceramic support may lead to particular generation, scratching of the wafer and a deterioration of process performance. 
     Therefore, there is a need for a PVD processing chamber having an improved shutter disk sensing system. 
     SUMMARY OF THE INVENTION 
     A physical vapor deposition chamber and a method for detecting a position of a shutter disk within a physical vapor deposition chamber are generally provided. In one embodiment, a physical vapor deposition chamber includes a chamber body having a shutter disk mechanism disposed therein. A housing is sealingly coupled to a sidewall of the chamber body and communicates therewith through a slot formed through the sidewall. At least a first sensor is disposed adjacent to the housing and is orientated to detect the presence of a shutter disk mechanism within the housing. 
     In another embodiment, a physical vapor deposition processing chamber includes a chamber body that has a shutter blade and a substrate support disposed therein. The shutter blade is adapted to support a shutter disk and is rotatable between a first position at least partially disposed in the housing and a second position within the chamber body proximate the substrate support. A housing is sealingly coupled to a sidewall of the chamber body and communicates therewith through a slot formed through the sidewall. A first sensor is disposed proximate the housing and is orientated to detect the presence of the shutter disk viewed by the first sensor through a first window formed in the housing when the blade is in the first position. 
     In another aspect of the invention, a method for detecting the position of a shutter disk within a physical vapor deposition chamber having a substrate support is provided. In one embodiment, a method for detecting the position of a shutter disk within a physical vapor deposition chamber having a substrate support includes moving the shutter disk from a first position substantially concentric with the substrate support to a second position clear of the substrate support, and sensing the edge of the shutter disk in the clear position. 
     In another embodiment, a method for detecting the position of a shutter disk within a physical vapor deposition chamber having a substrate support includes moving the shutter disk away from the substrate support, and changing the state of a first sensor in response to a position of an edge the shutter disk. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A more particular description of the invention, briefly summarized above, may be had by reference to the embodiments thereof, which is illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. 
     FIG. 1 depicts a semiconductor processing chamber having one embodiment of a sensor assembly adapted to detect a position of a shutter disk mechanism; 
     FIGS. 2A-B are sectional and plan views of a portion of the process chamber of FIG. 1; and 
     FIG. 3 depicts a sectional view of the sensor assembly taken along section line  3 — 3  of FIG.  4 . 
     To facilitate understanding, identical reference numerals having been used, wherever possible, to designate identical elements that are common to the figures. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The invention generally provides a semiconductor processing system having a sensor assembly adapted to detect a cleared position of a utility wafer, such as a shutter disk. The cleared position is defined as a position where a substrate support (and substrate seated thereon) may move vertically without contacting the shutter disk or mechanisms associated with the movement of the shutter disk. Although the invention is described in a physical vapor deposition chamber, the disclosure is one of illustration, and accordingly, the invention finds utility in other semiconductor processing chambers where it is advantageous to confirm a cleared position of a utility wafer or other device which may be disposed over a substrate support between substrate processing operations. 
     FIG. 1 depicts a semiconductor process chamber  100  that includes one embodiment of a sensor assembly  110  adapted to detect a cleared position of a utility wafer or shutter disk  114 . Generally, the sensor assembly  110  is utilized to ensure that the shutter disk  114  is not in a position that would contact a substrate support  104  or a substrate  112  seated thereon during processing. One example of a process chamber  100  that may be adapted to benefit from the invention is an IMP VECTRA™ PVD process chamber, available from Applied Materials, Inc., located in Santa Clara, Calif. 
     The exemplary process chamber  100  includes a chamber body  102  and lid assembly  106  that define an evacuable process volume  160 . The chamber body  102  is typically fabricated from a unitary block of aluminum or welded stainless steel plates. The chamber body  102  generally includes sidewalls  152  and a bottom  154 . The sidewalls generally contain a plurality of apertures that include an access port, pumping port and a shutter disk port  156  (access and pumping ports not shown). The sealable access port provides for entrance and egress of the substrate  112  from the process chamber  100 . The pumping port is coupled to a pumping system (also not shown) that evacuates and controls the pressure within the process volume  160 . The shutter disk port  156  is configured to allow at least a portion of the shutter disk  114  therethrough when the shutter disk  114  is in the cleared position. A housing  116  generally covers the shutter disk port  156  to maintain the integrity of the vacuum within the process volume  160 . 
     The lid assembly  156  of the body  102  generally supports an annular shield  162  suspended therefrom that supports a shadow ring  158 . The shadow ring  158  is generally configured to confine deposition to a portion of the substrate  112  exposed through the center of the shadow ring  158 . 
     The lid assembly  156  generally includes a target  164  and a magnetron  166 . The target  164  provides material that is deposited on the substrate  112  during the PVD process while the magnetron  166  enhances uniform consumption of the target material during processing. The target  164  and substrate support  104  are biased relative each other by a power source  184 . A gas such as argon is supplied to the process volume  160  from a gas source  182 . A plasma is formed between the substrate  112  and the target  164  from the gas. Ions within the plasma are accelerated toward the target  164  and cause material to become dislodged from the target  164 . The dislodged target material is attracted towards the substrate  112  and deposits a film of material thereon. 
     The substrate support  104  is generally disposed on the bottom  154  of the chamber body  102  and supports the substrate  112  during processing. The substrate support  104  is coupled to the bottom  154  by a lift mechanism (not shown) that is configured to move the substrate support  104  between a lower (as shown) and an upper position. The substrate support  104  is moved into the upper position for processing. In the upper position, the substrate  112  is disposed on the substrate support  104  and engages the shadow ring  158 , lifting the shadow ring  158  from the shield  162 . 
     In the lower position, the substrate support  104  is positioned below the shield  162  that allows the substrate  112  to be removed from the chamber  100  through the port in the sidewall  152  while clearing the ring  158  and shield  162 . Lift pins (not shown) are selectively moved through the substrate support  104  to space the substrate  112  from the substrate support  104  to facilitate securing of the substrate  112  by a wafer transfer mechanism disposed exterior to the process chamber  100  such as a single blade robot (not shown). A bellows  186  is typically disposed between the substrate support  104  and the chamber bottom  154  and provides a flexible seal therebetween, thereby maintaining vacuum integrity of the chamber volume  160 . 
     The substrate support  104  is typically fabricated from aluminum, stainless steel, ceramic or combinations thereof. One substrate support  104  that may be adapted to benefit from the invention is described in U.S. Pat. No. 5,507,499, issued Apr. 16, 1996 to Davenport et al., which is incorporated herein by reference in its entirety. 
     A shutter disk mechanism  108  is generally disposed proximate the substrate support  104 . The shutter disk mechanism  108  generally includes a blade  118  that supports the shutter disk  114  and an actuator  126  coupled to the blade  118  by a shaft  120 . A rotary seal  122  is disposed through the chamber bottom  154  to allow rotation of the shaft  120  without vacuum leakage from the process volume  160 . 
     The actuator  126  generally controls the angular orientation of the blade  118 . Typically, the blade  118  is moved between the cleared position shown in FIG. 1 and a second position that places the shutter disk  114  substantially concentric with the substrate support  104 . In the second position, the shutter disk  114  may be transferred (by utilizing the lift pins) to the substrate support  104  during the target burn-in and chamber pasting process. Typically, the blade  118  is returned to the cleared position during the target burn-in and chamber pasting process. 
     The actuator  126  may be any device that may be adapted to rotate the shaft  120  through an angle that moves the blade  118  between the cleared and second positions. The actuator  126  may be an electric, hydraulic or air motor, a pneumatic or hydraulic cylinder, or a solenoid among other motion devices. The actuator  126  may include a shaft sensor  124  that detects when the shaft  120  is rotated to the second position. The shaft sensor  124  may be directly coupled to the actuator  126 , as with a rotary encoder or limit switch, or may interface with the shaft  120 , as with a limit switch. Other sensors  124  that may be adapted to detect the angular position of the shaft  120  may also be utilized. 
     The blade  118  generally supports the shutter disk  114  in a horizontal orientation. The blade  118  typically has a flat body  142  that includes a hub  128  that is coupled to the shaft  120 , and at least three disk support pins  130  extending therefrom. The pins  130  generally support the shutter disk  114  in a spaced-apart relation to the blade  118 . The blade  118  is configured to allow rotation of the blade  118  from the second position to the cleared position without contacting the lift pins extending from the blade  118 . The blade  118  additionally includes a tab  220  (shown in FIG. 2A) that extends beyond the perimeter of the shutter disk  114 . 
     A portion of the shutter disk  114  is disposed in the housing  116  when in the cleared position. The housing  116  is typically fabricated from the same material as the chamber body  102 . The housing  116  is sealingly fastened to the chamber body  102 , and in one embodiment, is continuously welded at the interface between the housing  116  and body  102  to ensure a vacuum tight joint. 
     The housing  116  generally includes at least a first window  134  sealingly disposed through the housing  116 . The first window  134  is positioned to allow the sensor assembly  110  to detect the presence of the shutter disk  114  and/or the blade  118  within the housing  116 . In the embodiment depicted in FIG. 1, the housing  116  additionally includes a second window  136  formed in a bottom section  140  of the housing  116  opposite the first window  134  that is formed in a top section  138  of the housing  116 . The windows  134 ,  136  are fabricated from a material substantially transparent or non-invasive to the detection mechanism of the sensor assembly  110 , for example, quartz. 
     The sensor assembly  110  is generally disposed proximate the housing  116 . The sensor assembly  110  generally includes at least one sensor that is adapted to detect the presence of the blade  118  and/or shutter disk  114  within the housing  116 , preferably when in the cleared position. 
     The sensor assembly  110  is coupled to a controller  190  that interfaces with and typically controls the processing system  100 . The controller  190  typically comprises a central processing unit (CPU)  194 , support circuits  196  and memory  192 . The CPU  194  may be one of any form of computer processor that can be used in an industrial setting for controlling various chambers and sub-processors. The memory  192  is coupled to the CPU  194 . The memory  192 , or computer-readable medium, may be one or more of readily available memory such as random access memory (RAM), read only memory (ROM), floppy disk, hard disk, or any other form of digital storage, local or remote. The support circuits  196  are coupled to the CPU  194  for supporting the processor in a conventional manner. These circuits include cache, power supplies, clock circuits, input/output circuitry, subsystems, and the like. The sensors, at least including one of the sensor assembly  110  and the shaft sensor  124 , provide information to the controller  190  regarding the position of the shutter disk  114  and/or the blade  118 . 
     FIGS. 2A-B depict top and sectional plan views of the housing  116  illustrating one embodiment of the sensor assembly&#39;s position relative to the shutter disk  114 , the blade  118  and the substrate support  104 . The reader is encouraged to refer to both  2 A- 2 B simultaneously. 
     In the embodiment depicted in FIGS. 2A-B, the sensor assembly includes a first sensor  202 , a second sensor  204  and a third sensor  206 . The sensors  202 ,  204  and  206  are respectfully coupled to the top  134  of the housing  116  by brackets  208 ,  210  and  212 . The sensors  202 ,  204  and  206  generally provide a signal indicative of the presence of the shutter disk  114  and/or blade  118  thereunder. 
     The first and second sensors  202 ,  204  typically are positioned on a line  224  defined between a center point  214  of the substrate support  104  and reference point  216 . The reference point  216  is generally located at the center of the shutter disk  114  when the shutter disk  114  is in the clear position (as shown). In one embodiment, the center and reference points  214 ,  216  are also equidistant from a central axis  218  of the shaft  120 . The position of the sensors  202 ,  204  along the line  224  allows the sensors to provide a reliable indication that the shutter disk  114  is clear of the substrate support  104  as the line  224  lies along the shortest distance between the shutter disk  114  (when positioned correctly on the blade  118 ) and the substrate support  104 . 
     The first sensor  202  generally detects the position of the shutter disk  114  when in the cleared position. The second sensor generally detects the shutter disk  222  when the disk is mis-positioned on the blade  118  but still detected by the first sensor  202  as shown by phantom shutter disk  222 . For example, the shutter disk  222  may be positioned off-centered on the blade  118 , which places the disk  222  further into the housing  116 . Although the off-center position of the shutter disk  222  will still enable the substrate support to be moved vertically without contacting the shutter disk  222 , the shutter disk  222  will be misaligned with the substrate support  104  when rotated to the second position for pasting or target burn-in, which will allow material to be advantageously deposited on the substrate support  104 . Thus, the second sensor  204  indicates shutter disk  114  misalignment to the controller  190  which signals the operator or stops the production sequence is an appropriate point for service. 
     The third sensor  206  is generally positioned to view a portion or tab  220  of the blade  118  to indicate that the blade  118  is in the cleared position. The tab  220  of the blade  118  may be covered by the shutter disk  114  or extend beyond the shutter disk  114  to allow detection of the blade  118  when the disk  114  is also in the cleared position. Alternatively, the third sensor  206  may be positioned to view the substrate through the second window  134  or other window disposed in the housing  116 . 
     FIG. 3 depicts a sectional view of one embodiment of the sensors  202 ,  204  taken along section line  3 — 3  in FIG.  2 A. The sensors  202 ,  204  generally include an emitter  302  and a receiver  304 . The emitter  302  generates a signal, such as a light beam  306 , that passes through the windows  134 ,  136  and impinges upon the receiver  304 . When the shutter disk  114  blocks or interrupts the beam  306 , the sensors  202 ,  204  change state to indicate the presence of the shutter disk  114 . Examples of sensors  202 ,  204  that may be utilized to detect the shutter disk  114  are available Banner Engineering Corporation, located in Minneapolis, Minn. Other types of sensors, including reflective sensors (i.e., a device having the emitter and receiver configured into a single unit) may alternatively be utilized. The third sensor  206  is similarly configured to detect the presence of the blade  118 . 
     While the foregoing is directed to the preferred embodiment of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

Technology Category: c