Patent Publication Number: US-2010129940-A1

Title: Vibration monitoring of electronic substrate handling systems

Description:
TECHNICAL FIELD 
     The invention is directed, in general, to an electronic device substrate handling system, and more specifically, to detecting substrate handling errors by vibration monitoring, and, to the manufacture of electronic devices by fabrication processes that include such vibration monitoring. 
     BACKGROUND 
     The manufacture of electronic devices often includes multiple transfers of a device substrate to and from and within various tools used in the device&#39;s fabrication. Transferring a device substrate to and from and within each tool, or between tools, is often facilitated by the use of a substrate handling system. Often the substrate handling system is automated or semi-automated, using computer-controlled robotic machines to perform the repetitive motions of introducing and removing the substrate from and within the tool, and coordinating the movement of multiple substrates between multiple tools. 
     Over a period of use, however, components of the substrate handling system or the tools can become misaligned or worn, causing errors in the handling of the substrate. Handling error, in turn, can damage or alter the substrate. For example, a handling system may accidentally cause a substrate to contact the wall of a tool while introducing or removing a substrate from the tool. The contact can cause material to become dislodged from the wall of the tool and fall onto the substrate. Or, contacting the wall can cause a scratch, chip, break or other physical damage to the substrate. In other cases, the handling error may result in the substrate not being positioned at the proper location in the tool, and therefore the substrate does not receive the intended processing performed by the tool. 
     Accordingly, what is needed is a method of manufacturing electronic devices by a process that includes the use of a substrate-handling system that minimizes damage or alteration to electronic device substrates by reducing handling errors, and thereby increase device yields. 
     SUMMARY 
     One embodiment is an electronic device substrate handling system. The system comprises an electronic device fabrication tool and a mechanical handling structure. The fabrication tool is configured to hold at least one substrate on a mounting body of the tool. The mechanical handling structure is configured to actuate the substrate such that the substrate is transferred to or from the mounting body. The system further comprises a vibration monitor coupled to at least one of the mechanical handling structure, or, the tool. The vibration monitor is configured to measure vibrations of the mechanical handling structure, or, the tool, while the mechanical handling structure is actuating the substrate. The vibration monitor is also configured to convert the measured vibrations into a time-dependent electrical signal. 
     Another embodiment is a vibration monitoring module. the module comprises a vibration monitor and an analyzer module. The vibration monitor is coupleable to at least one of a mechanical handling structure or an electronic device fabrication tool. The vibration monitor is configured to measure and convert vibrations to electrical signals as described above. The analyzer module is coupleable to the vibration monitor. The analyzer module is configured to receive the electrical signal and detect a change in the electrical signal. 
     Still another embodiment is a method of manufacturing an electronic device. The method comprises performing a stage in a fabrication process flow. Performing the stage includes placing a substrate into a substrate handling system and actuating the substrate to or from a mounting body of a electronic device fabrication tool used in the stage. Actuating is performed using a mechanical handling structure of the substrate handling system. The method also comprises monitoring for a substrate-handling error while performing the actuating. Monitoring includes measuring vibrations from the substrate handling system using one or more vibration monitors coupled to the handling structure, or, the tool. Monitoring also includes converting the measured vibrations into time-dependent electrical signals. Monitor further includes determining whether or not the substrate-handling error has occurred by comparing the time-dependent electrical signals to a threshold value. 
    
    
     
       DRAWINGS 
         FIG. 1  presents a perspective view of an example embodiment of an electronic device handling system of the disclosure; 
         FIG. 2  presents a perspective view of an example embodiment of vibration monitoring module of the disclosure; and 
         FIG. 3  presents a flow diagram of an example method of an embodiment of manufacturing an electronic device in accordance with the disclosure. 
     
    
    
     DESCRIPTION 
     As part of the present disclosure, it was found that existing methods of monitoring of the performance of substrate handling systems can result in unacceptably high numbers of damaged substrates. For instance, the periodic inspection (e.g., particle counts or visual inspection) of device substrates, or, the testing of end-product electronic devices (e.g., integrated circuits, ICs, or, liquid crystal displays, LCDs) fabricated from the substrates, can reveal damage caused by substrate handling errors. However, hundreds of substrates may be processed before problems are detected, and, it may not be apparent where in the process the handling error occurred. 
     Sometimes, a vibration monitor can be attached directly to a substrate, and the vibrations that the substrate experiences while being fabricated can be recorded. The recording can then be examined for vibration anomalies to help identify where in the fabrication process a substrate handling error occurred. In some cases, however, it may not be desirable, or possible, to attach the vibration monitor to a substrate that is actually used in the fabrication of the electronic device. 
     For example, a substrate with a monitor attached to it does not have the same mass or shape as an actual device substrate (e.g., a substrate from which end products are actually made). The attached vibration monitor may change the mass and geometric shape of the substrate sufficiently to alter the ability of a substrate handler to move the monitor-attached substrate as compared to a device substrate. In some cases, therefore, the test substrate does not provide an accurate measure of substrate handling errors that actually occur for device substrates. 
     As another example, certain steps in the fabrication process may cause material from the vibration sensor to become deposited onto the substrate and thereby contaminate the substrate. These contaminants may alter the function of end-product electronic devices. To avoid such detrimental effects, the vibration monitor can be attached to a test substrate instead of an actual device substrate. However, as noted above, the presence of the vibration monitor may affect the movement of the substrate through the handler and therefore not provide accurate indications of handling errors. 
     As a third example, it may not be possible to expose the vibration monitor to all of the processes that a substrate is exposed to during a device&#39;s fabrication. For example, a vibration monitor may be damaged if it is exposed to dry or wet etching processes or to high-temperature thermal processes. Therefore it may not be possible to monitor potential handling errors for certain steps in the fabrication process. 
     As part of the present disclosure, it was discovered that vibration monitoring of the substrate handler itself, or, of a tool in the fabrication process, can be used to identify substrate handling errors. One might expect that placing a vibration monitor in locations that are remote from the substrate would detrimentally dampen the vibrations that the substrate experiences and that correspond to handling errors. It was surprising that indirect monitoring can provide useful information about substrate handling errors, given that there can be multiple vibrations occurring in the wafer handler or tool which are unrelated to errors in handling. It was unexpected that vibrations reflecting substrate handling errors can be effectively detected above background noise of other vibrations produced by the substrate handler or tool. 
     Moreover, there are advantages associated with vibration monitoring of the substrate handler or tool as compared to the direct vibration monitoring of a substrate. The vibrations of the substrate handler can be monitored at any step in the fabrication process, because the vibration monitor is not necessarily subjected to the processing environment of the substrate. Additionally, because the monitoring is indirect, monitoring for handling errors can be done for individual device substrates, and in some cases each and every device substrate. 
     One aspect of the disclosure is an electronic device substrate handling system.  FIG. 1  presents a perspective view of an example embodiment of a substrate handling system  100  of the disclosure. 
     The system  100  comprises an electronic device fabrication tool  110  configured to hold at least one substrate  115  on a mounting body  120  of the tool  110 . The system  100  also comprises a mechanical handling structure  125  configured to actuate the substrate  115  such that the substrate  115  is transferred to or from the mounting body  120  of the tool  110 . The system  100  further comprises a vibration monitor  130  coupled to at least one of the mechanical handling structure  125 , or, the tool  110 . The vibration monitor  130  is configured to measure vibrations of the mechanical handling structure  125 , or, the tool  110  while the mechanical handling structure  125  is actuating the substrate  115 . The vibration monitor  130  is also configured to convert the measured vibrations into a time-dependent electrical signal. 
     The tool  110  can be any structure that is configured to hold a substrate as part of the fabrication of an electronic device. Non-limiting examples of tools  110  include semiconductor wafer holding cartridges, such as a front opening unified pod (FOUP), plasma or wet etching tools, chemical mechanical polishers (CMP), photolithography processors, thermal diffusion, ashing ovens, or, other conventional tools familiar to those skilled in the art. The mounting body  120  can be any conventional location in the tool where substrates are normally held for some period during a fabrication process. For example, the mounting body  120  can be an orienteering structure of the FOUP, a platen in the CMP, or a pad or pedestal in an etching tool, a photolithography processor tool or an ashing tool. Transfers of the substrate  115  to or from the mounting body  120  can include inserting or removing the substrate  115  from the tool  110 , as well as moving the substrate  115  within the tool  110  (e.g., from one mounting body  120  to a different mounting body  120  of the tool  110 ). 
     The mechanical handling structure  125 , which is configured to actuate the substrate  115 , can include or be any machine component part involved in the handling of a substrate. For example, the mechanical handling structure  125  can be or include one or more of a motor housing  140 , arm  142 , wrist  144 , blade  146 , or other component parts familiar to those skilled in the art. In preferred embodiments, the movement of the mechanical handling structure  125  is under robotic control. One skilled in the art would be familiar with other types of machine components (e.g., conveyer belts, stackers etc. . . . ) that the mechanical handling structure  125  could have to facilitate moving the substrate  115  to or from the desired mounting location  120 . 
     The vibration monitor  130  as can be any mechanical or electronic apparatus that can measure mechanical vibrations, including sounds produced by mechanical vibrations, and that can convert these into electrical signals in real-time. That is, the vibration monitor  130  can measure moment-to-moment changes in the vibrations over time and convert these into a time-dependent electrical signal. It is an important to have the ability to measure real-time vibrations as a substrate is being handled so that unexpected handling error can be rapidly detected and localized to a particular stage, and substrate, in the fabrication process. For the purposes of the present disclosure, real-time measurements includes measurements that have a lag time (e.g., one to several seconds) between when a vibration occurs and when the corresponding electrical signal is formed and processed into useful information. The electrical signal can be, e.g., a current or voltage that is proportional to the amplitude of the vibration. 
     In some cases, the vibration monitor  130  includes or is an accelerometer sensor. One skilled in the art would be familiar with various type of accelerometers that can be used to measure mechanical vibrations, including piezoelectric, solid-state or strain-gage types of accelerometer mechanisms. A vibration monitor  130  having an accelerometer sensor has the advantage of being able to operate in a tool  110  with substantially no atmosphere. E.g., a plasma etch tool or chemical vapor deposition tool may operate at a chamber pressure of about 10 −3  atmospheres, and a physical vapor deposition tool or ion implantation tool may operate at chamber pressure of about 10 −   6  atmospheres. 
     In other cases, the vibration monitor  130  includes or is an acoustic sensor. Acoustic sensors may be limited for uses in environments having an atmosphere (e.g., about 1 atmosphere of air or other gases), because sound waves are not transmitted efficiently at low atmospheric pressure. However, in some cases, acoustic sensors can provide a more accurate detection of handling errors than an accelerometer sensor. For example, an acoustic sensor can potentially provide a broad range of acoustic frequencies during substrate handling. Because there is a broad range of acoustic frequency responses, it can be easier to distinguish vibrations caused by handling errors from normal vibrations that are unrelated to handling errors, as compared to using an accelerometer sensor. For example, if a substrate, due to a handling error contacts a chamber wall of a tool, a very different acoustic frequency may be emitted as compared to cases where a substrate does not contact the chamber wall. Moreover, in some cases there may be transient harmonic frequencies emitted about the frequency of the sound emitted when there is a handling error. In some cases, for example, the presence or absence, or the amplitude, of the transient harmonic frequencies can be advantageously used to better determine the location and type of handling error that has occurred. 
     The vibration monitor  130  can be directly coupled to a component part of the mechanical handling structure  125 , or, the tool  110 . As further illustrated in  FIG. 1  there can be a plurality of monitors  130  attached to different components of the handling structure  125  or the tool  110 . In some cases, a second vibration monitor  130  is coupled to the other of the handling structure  125  or tool  110 . For instance, the vibration monitor  130  can be attached to one or more of the motor housing  140 , arm  142 , wrist  144 , blade  146  parts of the handling structure  125 . Or, the vibration monitor  130  can be attached to one or more of a chamber  150 , or, to the mounting body  120  in the chamber  150  of the tool  110 . The use of multiple vibration monitors  130  can help to better determine the location and time when a handling error occurs. 
     Consider the case, e.g., when the vibration monitor  130  includes an acoustic sensor, and the chamber  150  is maintained at a low atmospheric pressure (e.g., less than about 0.1 atmosphere) during the time the wafer is transferred into or out of the tool  110 . In such cases, can be advantageous for an acoustic vibration monitor  130  to be attached to an outside surface  152  of a chamber wall  154 . However, in situations where the chamber  150  has a substantial atmosphere (e.g., greater than about 0.1 atmosphere), the acoustic vibration monitor  130  can be attached to the mounting body  120  of other location in the chamber  150  that is in close proximity to where the substrate  115  is actuated to or from. 
     In some cases, it can be advantageous to attach the vibration monitor  130  to a component part that is close to the substrate  115 , because vibrations due to handling errors can be more prominent as compared to other vibrations occurring in the normal course of substrate handling, and, that are unrelated to handling errors. E.g., it can be more desirable to attach the vibration monitor  130  to the blade  146  of the mechanical handling structure  125  as compared to the arm  142  or the wrist  144  because the substrate  115  directly contacts the blade  146  during its handling. Similarly, it can be more desirable to attach the vibration monitor  130  to the mounting body  120  as compared to the chamber wall  154  because the substrate  115  rests directly on the mounting body  120 . 
     In some embodiments, the vibration monitor  130  is configured to measure the vibrations from individual ones of each substrate  115  that is actuated by the mechanical handling structure. For instance, in some preferred embodiments, the substrate  115  is a device substrate, such as a semiconductor wafer, upon which electronic devices, such as an integrated circuit (IC) devices, are formed. Or, the substrate  115  is one or more of the thin film substrates (e.g., glass substrates), upon which electro-optical amplitude modulator devices, such as LCDs, are formed. Even more preferably, each and every device substrate  115  that is passed through the system  100  is monitored for vibrations to identify potential handling errors. This is in contrast to embodiments where a test substrate  115  is only periodically run through the system  100  to check for handling errors. 
     In some embodiments, the vibration monitor  130  is implanted within, and in some cases, fully enclosed within the mechanical handling structure  125  or the tool  110 . Sometimes it is more preferable for the implanted vibration monitor  130  to include an accelerometer sensor instead of an acoustic sensor because the sensitivity of the latter type of sensor may be substantially decreased when it is implanted within a structure  125 . 
     Implanting the monitor  130  can be advantageous in situations where the vibration monitor  130  would otherwise be exposed to harsh environments (e.g., radio-frequency plasma fields or etching chemicals) that otherwise would damage the monitor  130 . For example, the monitor  130  can be implanted inside of one of the component parts of the mechanical handling structure  125  or the tool  110  such that it is not exposed to the harsh environment. 
     Implanting the monitor  130  can also be advantageous in situations where the vibration monitor  130  would otherwise obstruct the normal movement of the mechanical handling structure  125  or the tool  110  during its operation. For example, it can be desirable to implant the monitor  130  inside of the arm  142 , the wrist  144 , or the blade  146 , if a monitor  130  attached to the outside surface of these structures could physically obstruct the normal range of motion of these components during a wafer handling operation. 
     As further illustrated in  FIG. 1 , some embodiments of the system  100  can further include an analyzer  160  (shown as a block diagram) coupled to the vibration monitor  130 . The analyzer  160  is configured to receive the time-dependent electrical signals generated by the monitor  130  in response to vibrations. Coupling can be achieved by a wired or a wireless connection between the analyzer  160  and the monitor  130 . The analyzer  160  is also configured to process the time-dependent electrical signals and detect changes in the signal that indicate a handling error. 
     One skilled in the art would be familiar with parts that the analyzer  160  could have to facilitate the analyzer&#39;s function. For example, the analyzer  160  can include an input module  162  configured to receive the electrical signals and memory module  164  configured to store electrical signals, a central processing unit (CPU)  166  configured to perform operations on the stored or incoming signals and an output module  168 . 
     In some embodiments, the analyzer  160  is also configured to interdict in a stage in device fabrication if the change in the electrical signal corresponding to a handling error exceeds a threshold value. Interdiction can range, for example, from immediately stopping a fabrication step to sending a warning alert to a system operator. For instance, the output module  168  can be configured to send signals to other components of the system  100  (e.g., the tool  110  or mechanical handling structure  125 ) or to a system operator (e.g., a human or computer controlling the system&#39;s operation). 
     The analyzer  160  can be configured to process the time dependent electrical signal to facilitate the detection of substrate handling errors. In some preferred embodiments, as part of interpreting the electrical signal, the analyzer  160  is configured to transform the time-dependent electrical signal into a frequency-dependent signal (e.g., vibration spectra). For instance, the CPU  166  can be configured to perform Fourier transform operations on the incoming or stored electrical signal. Transforming the time-dependent electrical signal into a frequency-domain spectrum can make it easier to distinguish normal vibrations from vibrations due to handling errors. 
     In some embodiments, the analyzer  160  is configured to calculate a time-average of the amplitude of the electrical signal and compares the time average to a threshold value. E.g., if the magnitude of the vibrations over a period of substrate handling, as measured by the time-averaged amplitude of the electrical signal, exceeds the threshold value, then the analyzer may send an interdiction signal to shutdown the tool  110  or mechanical handling structure  125 , or, to alert the operator. The threshold value can be determined experimentally, e.g., by measuring the average and standard deviation (SD) of the vibration obtained under control conditions when handling errors are known not to occur. The threshold value can be set to a multiple of the standard deviation (e.g., 3×SD) measured under these control conditions. 
     Alternatively or additionally, in cases where, e.g., the average vibration does not substantially change when a handling error occurs, the analyzer can be configured to calculate the amplitude of the vibration (e.g., the minimum and maximum electrical signal over a predefine period of substrate handling). Or, the analyzer can be configured to calculate the rate of change of the vibration. One skilled in the art would be familiar with other ways to detect anomalous vibrations associated with handling errors. E.g., in some embodiments, the CPU  166  can be configured to operate a tool interdiction monitoring system software program, (e.g., TIMS, Texas, Instruments, Dallas, Tex.) which is configured to identify anomalous changes in the electrical signal. 
     Another aspect of the invention is a vibration monitoring module. In some cases, the vibration monitoring module is retrofit kit that can be added to, or replace, components of an existing substrate handling system.  FIG. 2  shows an example vibration monitoring module  200  of the disclosure attached to a substrate handling system  202  that is analogous to the system  100  described in the context of  FIG. 1 , except that the system  202 , until the addition of the module  200 , did not have the capability to monitor substrate handling errors in the manner disclosed herein. Similar reference numbers are used to designate component parts of the system  202  that are analogous to system  100  depicted in  FIG. 1 . 
     The vibration monitoring module  200  comprises a vibration monitor  210  and an analyzer module  220 . The vibration monitor  210  and analyzer module  220  can comprise any of the embodiments discussed above in the context of  FIG. 1 . 
     The vibration monitor  210  is coupleable to at least one of a mechanical handling structure  125  or an electronic device fabrication tool  110 . The vibration monitor  210  is configured to measure vibrations from the handling structure  125  or the tool  110  while the handling structure  125  is actuating a substrate  115  to or from the tool  110 . The vibration monitor  210  is configured to convert these measured vibrations into a time-dependent electrical signal. The analyzer module  220  coupleable (e.g., through wired or wireless communication means) to the vibration monitor  210 , and the analyzer module  220  is configured to receive the electrical signal and detect a change in the electrical signal. 
     In some embodiments, the analyzer module  220  includes a replacement module  230  of one of the components of the handling structure  125  or tool  110 . The vibration monitor  210  can be included in the replacement module  230 . For example, the vibration monitor  210  can be included within one or more replacement modules  230  configured to be a component part of the handling structure  125  or the tool  110 . Including the vibration monitor  210  as part of a replacement module  230  has the advantage of minimizing or eliminating effects that the presence of the monitor  210  might have on the operation of the handling structure  125  or the tool  110 . For instance, the replacement module  230  can have substantially the same weight, shape and composition as the original component part (e.g., a blade  146  or a mounting body  120 ,  FIG. 1 ) except that the vibration monitor  210  is within the part  230 . In other cases, however, the vibration monitor  210  can be a separate structure attached to the original component part of the system, similar to that shown for the monitors  130  depicted in  FIG. 1 . 
     Another aspect of the invention is a method of manufacturing an electronic device that includes monitoring substrate handling errors. Any of the embodiments of electronic devices, substrates, substrate handling, fabrication tools and vibration monitoring, such as described above and in the context of  FIGS. 1-2 , can be used in the manufacture of the device and the monitoring of handling errors.  FIG. 3  presents a flow diagram of an example method  300  of an embodiment of manufacturing an electronic device in accordance with the disclosure. 
     The method  300  includes performing a stage (step  305 ) in a fabrication process flow (step  310 ). The fabrication process flow can be any conventional process used in the fabrication of an electronic device that includes a substrate, and the stage (step  305 ) can be at any stage in the flow  310  where a substrate handling error can occur. 
     The stage (step  305 ) in the fabrication process further includes a step  315  of placing a substrate into a substrate handling system, and a step  320  of actuating the substrate to or from a mounting body of an electronic device fabrication tool used in the step  310 . The actuating step  320  is performed using a mechanical handling structure of the substrate handling system. 
     The method  300  further includes a step  330  of monitoring for a substrate-handling error while performing the actuating step  320 . Monitoring (step  330 ) includes a step  335  of measuring vibrations from the substrate handling system using one or more vibration monitors coupled to the mechanical handling structure, or, the tool. Monitoring (step  330 ) also includes a step  340  of converting the vibrations into time-dependent electrical signals. 
     Monitoring (step  330 ) further includes a step  345  of determining whether or not a substrate-handling error has occurred by comparing, in step  350 , the time-dependent electrical signals to a threshold value. In some cases, the step  345  of determining the presence or absence of a handling error, can includes transmitting, in step  355  the time-dependent electrical signal to an analyzer that is configured to compare the electrical signal to the threshold value. 
     Embodiments of the method  300  can further include interdicting (step  360 ) in the fabrication process flow  310  if the electrical signal exceeds the threshold value. As illustrated in  FIG. 3 , interdiction can occur at several different levels in the flow  310 . For example, interdiction (step  360 ) can include a step  362  of stopping the stage (step  305 ) in the fabrication process (e.g., immediately or after finishing the stage  305 ), and, a step  364  of inspecting the substrate for damage. If the substrate is not damaged, it can be returned to the flow  310 . If the substrate is damaged, it can be designated as a scrap substrate, and not further processes by the flow  310 , or, returned to the beginning of the flow  310  for reprocessing. 
     In some cases, interdiction (step  360 ) includes stopping (step  366 ) the fabrication process flow  310  after performing the flow  310  on an entire lot of the substrates. 
     In other cases, interdiction (step  360 ) can include a step  368  performing a preventive maintenance procedure on the substrate handling system, or, on the tool. In still other instances, interdicting (step  360 ) can include a step  370  of sending an alert to an operator of the fabrication process flow  310 . 
     One skilled in the art would understand that monitoring  330  and interdicting  360  and their sub-steps can be done at any number or all of the stages  305  in the flow  310  where a substrate handling error could occur. One skilled in the art would also be familiar with the details of the processing stages  305  that are performed in the flow  310  to produce the end-product device (e.g., an IC or LCD). 
     Those skilled in the art to which the invention relates will appreciate that other and further additions, deletions, substitutions and modifications may be made to the described example embodiments, without departing from the invention.