Abstract:
The present invention provides a method for signal vibration alert. The method of the present invention recognizes significant substantial swerves and corresponding substantial edge-to-edge differences by eliminating the adverse effect of noise among signals generated by an apparatus. When the frequency of the substantial edge-to-edge differences that exceed an acceptable range of the frequency limit is too large, the method of the present invention automatically generates an alert to indicate aberration in the apparatus such that the monitoring staff is informed and allowed to take necessary measures responding to the aberration.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a method for generating an alert, and more particularly relates to a method for automatically generating an alert when the level and frequency of signal vibration exceed a certain scale. 
     2. Description of the Related Art 
     To maintain a stable manufacturing process, signals generated in the manufacturing process are monitored. The signals may refer to the intensity of a light source used by a stepper required in the semiconductor manufacturing process, or the flow rate of etching solution used by a wet etching machine. Signal monitoring prevents products from being damaged by irregular operation. 
     Generally, signal monitoring is applied by predetermining upper and lower limits of so the signals. When the signals generated by process tools exceed the predetermined upper and lower limits, the monitor generates an alert to indicate the aberration in the apparatus such that the monitoring staff can take necessary action. FIG. 1 is a graph showing signals generated within a time interval by a process tool. In FIG. 1, all signals fall within a range between the upper and lower limits (i.e. 3.0 and 1.4 in FIG.  1 ). If the machine is using a general monitoring method, as a result, no alert is generated. 
     Although the signals fall within a range between the upper limit and lower limit, signal vibration may be an indicator of potential problems resulting in malfunction of process tools. When applying a general monitoring method that only employs upper and lower limits, not only signal vibration, but also potential problems are hidden. 
     SUMMARY OF THE INVENTION 
     The main object of the present invention is to provide a method for generating a signal vibration alert, wherein the vibration frequency is precisely calculated and a timely alert is provided to monitoring staff without interference from insignificant noise. 
     The method of the present invention collects a plurality of signals generated by a apparatus within a time interval. Based on the plurality of signals, a plurality of substantial swerves and of corresponding substantial edge-to-edge differences are recognized. Every three consecutive substantial swerves constitute a peak or a valley. Each substantial edge-to-edge difference is the edge-to-edge difference between every two consecutive swerves, and exceeds a predetermined noise range. Then, the frequency of the substantial edge-to-edge differences that exceed an acceptable range is calculated. If the frequency exceeds a predetermined frequency limit, an alert is automatically generated to indicate aberration in the apparatus. 
     In particular, the method of the present invention ignores signal variation resulting from noise, and focuses on recognizing the real vibration amplitude (i.e. substantial edge-to-edge difference) from signals generated. As soon as the substantial edge-to-edge differences exceed an acceptable range of the frequency limit, there may be potential problems concerning the operation of the apparatus. 
     The advantage of the present invention is that given signals do not exceed upper and lower limits; the method indicates the status of an apparatus by monitoring signal vibration and advances a timely alert to monitoring staff. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention can be more fully understood by reading the subsequent detailed description in conjunction with the examples and references made to the accompanying drawings, wherein: 
     FIG. 1 is a graph showing signals generated within a time interval by a process tool; 
     FIG. 2 is a graph showing the relationship between the signals and the method according to the present invention; 
     FIG. 3 is a graph showing substantial swerves among the signals recognized with the method according to the present invention; 
     FIG. 4 is a flowchart of the method according to the present invention; 
     FIG. 5 is an application flowchart recognizing the substantial swerves; 
     FIG. 6 is a perspective diagram showing the method for recognizing substantial swerves; and 
     FIG. 7 is a detailed flowchart of the step  44  and step  46  shown in FIG. 4 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The main focus of the present invention lies in ignoring the vibration of signals smaller than a certain scale, and calculating the frequency of the vibration exceeding a certain scale, thereby determining whether the corresponding process tool shows an aberration based on increased frequency of the vibration. 
     FIG. 2 is a graph showing the relationship between the signals and the method according to the present invention. When the signal trend turns from ascending to descending or from descending to ascending, a swerve  20  is formed. A swerve can be either a peak or a valley. The value difference between two swerves is defined as an edge-to-edge difference. The method according to the present invention predetermines a noise range. If an edge-to-edge difference falls within the noise range, the signal variation is regarded as noise. Noise goes through appropriate screening that recognizes significant substantial swerves and corresponding edge-to-edge differences. In this way, signal vibration resulting from potential malfunction problems can be identified. 
     Five swerves  20  are shown during the time interval  22  in FIG. 2, where the edge-to-edge differences of any two swerves  20  fall within the noise range. In terms of the signal waveform, the signals within the time interval  22  represent a valley of a substantial waveform. It is noted that a substantial swerve of the substantial waveform should be the maximal swerve among the five swerves  20  and is marked as  20   a.    
     Three swerves  20  are shown during the time interval  26  in FIG. 2, where the edge-to-edge differences of any two swerves  20  fall within the noise range. In terms of the signal waveform, the signals within the time interval  26  represent a peak of a substantial waveform. It is noted that a substantial swerve of the substantial waveform should be the maximal swerve among the three swerves  20  and is specially marked as  20   b.    
     Two swerves  20  are shown during the time interval  24  in FIG. 2, where the edge-to-edge differences of any two swerves  20  fall within the noise range. In terms of the signal waveform, the signals within the time interval  26  represent an ascending portion of a wave. Accordingly, the swerves  20  during the time interval  24  are recognized as insignificant noise, not substantial swerves. 
     Four swerves  20  are shown during the time interval  28  in FIG.  2 . Although not all the edge-to-edge differences of any two swerves  20  fall within the noise range, the edge-to-edge differences for ascending sections all fall within the noise range. In terms of the signal waveform, signals within the time interval  28  represent a descending portion of a wave. Accordingly, the swerve  20  during the time interval  28  are recognized as insignificant noises, not substantial swerves. 
     FIG. 3 is a graph showing substantial swerves among the signals shown in FIG.  1 . The substantial swerves are recognized with the method according to the present invention. According to the method of the present invention, some swerves in FIG. 1 are ignored as insignificant noise. Some swerves shown in FIG. 3 are selected as substantial swerves. Each substantial edge-to-edge difference of every two consecutive substantial swerves  30  has to exceed a predetermined noise range. In addition, every three consecutive substantial swerves constitute a peak or a valley. In other words, either the substantial swerves on the side exceed the middle substantial swerve, or the middle substantial swerve exceeds the substantial swerves on the side. 
     FIG. 4 is a flowchart of the method according to the present invention. Via a designated application, a server performs the method according to the present invention. Firstly, at step  40 , the server collects a plurality of signals within a time interval. At step  42 , the server recognizes substantial swerves. When the substantial swerves are recognized, it follows that corresponding substantial edge-to-edge differences are also attained. The substantial edge-to-edge differences can be regarded as real signal amplitude of the waveform without interference from insignificant noise. At step  44 , the server calculates the frequency of substantial edge-to-edge difference (i.e. vibration amplitude) that exceeds an acceptable range. When the frequency exceeds a predetermined frequency limit (i.e. the flow following yes in response to step  46 ), the server generates an alert automatically to indicate aberration of the corresponding process tool (as shown at step  48 ). When the frequency does not exceed the predetermined frequency limit (i.e. the flow following no in response to step  46 ), the server indicates that the corresponding process tool does not have a signal vibration problem. 
     FIG. 5 is an application flowchart of recognized substantial swerves. In FIG. 5, the S(a) represents the value of swerve a, d(X) represents the value of data x, Dflag represents a trend flag around the signal being processed (ascending trend refers to 1 and descending trend refers to −1), LocalMin represents the local minimum in the instant signal trend, and LocalMax represents the local maximum in the instant signal trend. 
     At step  60 , the server determines a noise range. At step  62 , the swerve determines an initial condition of local variables. Wherein x=2 represents that d( 1 ) and d( 2 ) are going to be selected, a=1 represents that the first substantial swerve is requested to be attained, the Dflag is set as 0 representing that the waveform portion is level, and the LocalMin and LocalMax are both set as the first signal value d( 1 ). 
     When d(x) is greater than d(x− 1 ) (the flow following &gt;0 in response to step  64 ), it indicates that the instant signal d(x) represents an ascending trend. Nonetheless, if the ascending trend results from noise (the flow following yes in response to step  66 ), d(x) is omitted and the flow moves to process the next signal. If the ascending trend is obvious, it means that the instant trend is recognized as being ascending (the flow following no in response to step  66 ), accordingly, the trend flag is set as 1. Two conditions must be detected. One is that the instant trend and the previous trend are both ascending (the flow following yes in response to step  68 ). When the trend remains ascending, merely LocalMax is required to be updated (step  69 ). The other is that the instant trend (ascending) is different from the previous trend, level or descending (the flow following no in response to step  68 ). Under the circumstances, another new valley is recognized and as a result another substantial swerve is determined. This instant substantial swerve S(a) is set as a LocalMin. At the same time as setting S(a), d(x) is used to update LocalMax. In addition, trend flag is set as 1. This means that the instant trend is ascending (step  70 ). The method then moves to recognize a following substantial swerve (step  72 ). When signals have not been completely processed (the flow following no in response to step  74 ), the method flow moves to process a following signal (step  76 ). 
     In the right half of FIG. 5, when d(x) is smaller than d(x−1) (the flow following &lt;0 in response to step  64 ), the process steps are similar with the process steps used in the left half of FIG.  5 . 
     When all signals are processed (the flow following yes in response to step  74 ), the frequency of substantial edge-to-edge difference (i.e. vibration amplitude) that exceeds an acceptable range is calculated (step  44  in FIG.  4 ). 
     FIG. 6 is a perspective diagram showing the method for recognizing substantial swerves. Substantial swerves are also recognized with an alternative method. For example, all swerves among the signals, such as S T1 , S V1 , S T2 , S V2  and others are recognized. T in S T1  refers to a peak and V in S V1  refers to a valley. As long as a signal is lower than two adjacent signals, the signal is a valley swerve and as long as a signal is higher than two adjacent signals, the signal is a peak swerve. It follows that the method recognizes whether the edge-to-edge difference of two consecutive peaks falls within the noise range. For example, if the edge-to-edge difference between S V1 and S   T2  in swerve series  80  falls within the noise range, it means that S V1  and S T2  are swerves resulting from the noise and are required to be processed. In addition, S t1 , and Sv 2  adjacent to S V1  and S T2  are processed along with S V1  and S T2 . The process step is to select a maximum between S T1  and S T2  to attain a new peak swerve S TF1 (=Max(S T1 , S T2 )), and a minimum between S V1  and S V2  to attain a new valley swerve S VF1 (=Min(S V1 , S V2 )): Then, replacing four consecutive swerves that are processed (ST 1 , SV 1 , ST 2  and SV 2 ) with STF 1  and SVF 1 , a new swerve series  82  is generated and the alternating configuration of peaks and valleys stays as shown in FIG.  6 . 
     If the edge-to-edge difference of S T3  and S V3  falls within the noise range, it means that S T3  and S V3  are two swerves resulting from noise. With the process steps similar to the method mentioned in the previous paragraph, and SVF 2  and STF 2  are attained to replace S VF1 , S T3 , S V3  and S T4 , a new swerve series  84  is generated as shown in FIG.  6 . Through the repetition of the method mentioned in the current and previous paragraphs, a final swerve series is generated; wherein the edge-to-edge difference every two adjacent peaks exceeds the noise range. Substantial swerves are the elements of the final swerve series. 
     FIG. 7 is a detailed flowchart of steps  44  and  46  shown in FIG.  4 . After the substantial swerve is recognized, substantial edge-to-edge differences are attained via measuring the edge-to-edge difference of every two adjacent substantial swerves. Substantial edge-to-edge differences are categorized as a descending edge-to-edge difference, the distance from a peak substantial swerve to a valley substantial swerve, and an ascending edge-to-edge difference, a distance from a valley substantial swerve to a peak substantial swerve. The acceptable range of substantial edge-to-edge difference comprises an acceptable ascending range and acceptable descending range. When the frequency (N u ) by which an ascending edge-to-edge difference exceeds the acceptable ascending range is greater than an acceptable frequency value (N au ), an alert reminds monitoring staff that the corresponding process tool is operating in an aberrant fashion. Similarly, if the frequency (N d ) by which an instant descending edge-to-edge difference exceeds the acceptable descending range is greater than a predetermined value (N ad ), an alert is also sent. 
     The method of the present invention monitors signals generated by a process tool in manufacturing, thereby determining whether there are potential problems hidden among significant signal vibrations during operation. Thus monitoring staff can be informed in advance by an alert in response to significant signal vibration and take appropriate action. Accordingly, a stable production line is maintained. 
     Finally, while the invention has been described by way of examples and in terms of the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. On the contrary, it is intended to cover various modifications and similar arrangements as would be apparent to those skilled in the art. Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.