JP2007194548A - Method and system for verifying end point - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and a system for verifying an end point in which "erroneous detection of end point" can be discovered from a dispersion in required end point detection times. <P>SOLUTION: A method for processing a plurality of wafers belonging to a predetermined lot one by one uses an ashing device 1 comprising an end point detection function, and then verifies a required detection time of an end point detected for each wafer with the processing for the unit of a lot. This method includes a step of determining a difference between a maximum value and a minimum value of the required detection time within the lot, and determining presence/absence of abnormality in the detection of the end point within the lot based on the difference (S4, S5). If a wafer which is processed incompletely because of erroneous detection of end point is present within a lot, its presence becomes clear, thereby preventing the wafer from flowing to the next step. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an endpoint verification method and an endpoint verification system, and more particularly to a technique for detecting “endpoint false detection” based on variations in endpoint detection time.

In the wafer process step, a resist pattern is formed by a photolithography technique. The resist pattern is used as a mask for etching the base layer and a mask for ion implantation. Further, the resist pattern after being used as a mask is removed from the wafer by, for example, an ashing process using oxygen plasma or the like.
In many cases, the ashing process is performed in a single wafer mode, and the process is terminated by detecting an end point for each wafer. There are various methods for detecting the end point, for example, by monitoring the wavelength change of the reflected light from the wafer, and these are well known (see, for example, Patent Documents 1 and 2).

In addition, the process time from the start of the ashing process to the end of the process (that is, detecting the end point) varies depending on the state in the chamber of the apparatus to be used, the state of the resist pattern covering the wafer surface, and the like. . For example, when the resist pattern is ashed, products are generated, and these adhere to the plasma generating electrode in the chamber. For this reason, as the number of treatments accumulates, the electrodes and the like gradually deteriorate, and the process time tends to become longer.
Japanese Patent Laid-Open No. 10-163176 Japanese Patent Laid-Open No. 5-291188

  By the way, the resist pattern consists of a resist coating process for applying a photoresist on the underlayer on the wafer surface, an exposure process for transferring a photomask pattern to the applied photoresist, and a developer applied dropwise to the exposed photoresist. Then, it is formed through a development process that reveals the latent pattern. In the resist coating process, a spin coater is used for the photoresist coating process, and the film thickness of the photoresist is basically uniform due to the characteristics of the coating method. However, the film thickness of the photoresist may become non-uniform due to reflection of irregularities in the underlayer or sudden occurrence of abnormality in the resist coating process.

  If the film thickness of the photoresist is non-uniform, there is a high possibility that the film thickness of the resist pattern formed through the development process and the exposure process will also be non-uniform. In the ashing process, when the wavelength change of the reflected light is monitored at a location where the film thickness of the resist pattern is locally small by accident, the endpoint is detected abnormally early (that is, erroneously detected). As a result, the ashing process may end even though the resist pattern remains at other locations on the wafer.

  Here, “endpoint misdetection” does not occur so much, and the frequency of occurrence is at most about one lot per several tens of lots, which is also about several wafers within one lot. . It can be said that the frequency of occurrence is low. However, if the ashing process is terminated incomplete due to “endpoint detection error”, the cleaning machine may be contaminated with photoresist in the subsequent wafer cleaning process.

  In order to solve such a problem of resist contamination, the present inventor provides an upper limit management value (UCL) and a lower limit management value (LCL) for the endpoint detection required time, and the detection required time is less than the LCL. Alternatively, a method for determining when the value exceeds UCL as “false detection of endpoint” was examined. However, the ashing device has a tendency that the process time gradually increases as the number of processes is accumulated. Therefore, the ashing device has an endpoint detection function. That is, in a single wafer processing apparatus provided with an end point detection function, the fluctuation range of the process time is usually large. Therefore, in this method, the width between UCL and LCL must be set wide, and even if "endpoint misdetection" occurs, the abnormal value is almost between UCL and LCL. , "Endpoint misdetection" could hardly be found.

  Therefore, the present invention has been made paying attention to such an unresolved problem in the conventional technology, and “endpoint detection error” is discovered by variation in the time required for detection of the endpoint. An object is to provide an endpoint verification method and an endpoint verification system.

[Invention 1-3] In order to achieve the above object, the endpoint verification method of Invention 1 uses a single wafer processing apparatus having an endpoint detection function for a plurality of wafers belonging to a predetermined lot. In this method, the required time for detection of the endpoint detected for each wafer in accordance with the processing is verified for each lot, and the maximum and minimum values of the required time for detection in the lot And a step of determining whether or not there is an abnormality in detection of the end point in the lot based on the difference.

  Here, examples of the “single wafer processing apparatus having an endpoint detection function” include a dry etching apparatus and an ashing apparatus. The “end point detection time” is the time from the start of single wafer processing to one wafer until the end point (end point) is detected on the wafer. The present inventor noted that “endpoint false detection” occurs less frequently, and the occurrence frequency is at most about a few wafers in a lot, and “endpoint false detection” is performed. I came up with the idea of finding the end point detection time variation.

  In the endpoint verification method of the invention 2, in the endpoint verification method of the invention 1, in the step of determining whether or not there is an abnormality in the detection of the endpoint, when the difference is larger than the predetermined value, It is determined that there is an abnormality in the detection of the end point in the lot, and otherwise, it is determined that there is no abnormality in the detection of the end point in the lot.

The endpoint verification method of the invention 3 is characterized in that, in the endpoint verification method of the invention 1 or 2, the step of notifying the abnormality when it is determined that the detection of the endpoint is abnormal is included. It is.
According to the end point verification methods of the inventions 1 to 3, when there is a wafer in the lot in which the end point is erroneously detected and the single wafer processing is completed in an incomplete state, its existence becomes clear. Outflow of the wafer to the next process can be prevented. For example, wafers that may not have been completely stripped of photoresist can be stopped in the ashing process so as not to flow into the cleaning process, so that resist contamination of the cleaning machine can be prevented.

[Invention 4] The endpoint verification system according to the invention 4 includes processing a plurality of wafers belonging to a predetermined lot one by one using a single-wafer processing apparatus having an endpoint detection function. A system for verifying the required detection time of an endpoint detected for each wafer in units of lots, a means for obtaining a difference between a maximum value and a minimum value of the required detection time in the lot, and the difference And a means for judging whether or not there is an abnormality in the detection of the end point in the lot.

  With such a configuration, when there is a wafer in the lot in which the end point is erroneously detected and the single wafer processing is completed in an incomplete state, the existence is clarified, so that the next process of the wafer is performed. Can be prevented from flowing out.

Embodiments of the present invention will be described below with reference to the drawings.
(1) First Embodiment FIG. 1 is a flowchart showing an endpoint verification method according to an embodiment of the present invention. In the first embodiment, a case where the flowchart shown in FIG. 1 is executed using the ashing device 1 shown in FIG. 2, the controller 3, and the computer 10 will be described.

  First, in step S1 of FIG. 1, in the single-wafer ashing apparatus 1 having an end point detection function, for example, 25 wafers per lot are subjected to ashing processing one by one. All processes in the ashing apparatus 1 are controlled by the controller 3, and the ashing process for one wafer is ended when the end point detection function of the ashing apparatus 1 detects the end point under the control of the controller 3. ing. Here, first, for example, an ashing process is performed on a wafer whose ID number (#) in the lot is 1 (hereinafter referred to as “wafer # 1”).

  Next, in step S2 of FIG. 1, the controller 3 records the time required for detecting the endpoint of wafer # 1. For example, when the ashing process for wafer # 1 is started in the ashing apparatus 1 shown in FIG. 2, the controller 3 starts measuring time, and ends the time measurement when an end point is detected. Then, the controller 3 creates data related to the endpoint detection required time based on the measured time, and stores the data in a storage device (for example, RAM) inside the controller 3.

  Next, in step S3 in FIG. 1, the controller 3 determines whether or not the ashing process for all the lots has been completed. When the ashing process for all the lots (that is, wafers # 1 to 25) and the recording of the data are completed, the process proceeds to step S4. Otherwise, the process returns to step S1, and steps S1 to S3 are repeated. In this way, the ashing process for all the lots (that is, wafers # 1 to 25) is performed, and the data is recorded as shown in FIG.

  In step S4, the maximum value and the minimum value of the time required for detecting the endpoint in the lot are specified, and the range (difference) is calculated. The maximum value and the minimum value are specified and the range is calculated, for example, by the endpoint verification computer 10. As shown in FIG. 2, the computer 10 is connected to the controller 3 via a wired or wireless connection. The computer 10 is composed of, for example, a CPU and a hard disk, and is arranged in a clean room. In step S4, data relating to the required detection time in the lot (see FIG. 3) is sent from the controller 3 to the computer 10 and stored in the hard disk of the computer 10. Then, the CPU of the computer 10 specifies the maximum value and the minimum value and calculates the range based on the data stored in the hard disk.

Next, in step S5 of FIG. 1, the computer 10 determines whether or not all of the required detection times in the lot are included in the management value and the range is equal to or less than a predetermined value (that is, whether the range is within the standard). . Here, the management value and the predetermined value are numerical values that can be arbitrarily set by the user based on experience and the like.
FIGS. 4A and 4B are diagrams illustrating an example when it is determined that the standard is satisfied in step S <b> 5 of FIG. 1. 4A and 4B, the horizontal axis represents the time required to detect an end point within a lot, and the vertical axis represents the number of processes (that is, the number of wafers). As shown in FIGS. 4A and 4B, in this example, the upper limit management value (UCL) and the lower limit management value (LCL) are set with sufficient margins for the time required for endpoint detection. ing. As shown in FIGS. 4 (A) and 4 (B), when the detection required time in the lot is all between LCL and UCL and the range is less than or equal to a predetermined value (range ≦ predetermined value) In step S5 of FIG. 1, it is determined that the required detection time is within the standard and there is no abnormality in the detection of the endpoint, and the process proceeds to step S6.

In step S6 of FIG. 1, the computer 10 displays on its monitor screen 11, for example, the lot ID, the required time for detecting each wafer # 1 to 25 belonging to the lot, the maximum value and the minimum value of the required time for detection, The range and a character “OK”, for example, are displayed as a verification result.
FIGS. 5A and 5B are diagrams illustrating an example when it is determined that the standard is out of step S5 in FIG. The horizontal and vertical axes in FIGS. 5A and 5B and UCL, CL, and LCL are the same as those in FIGS. 4A and 4B. As shown in FIGS. 5A and 5B, when the range is larger than the predetermined value (range> predetermined value), in step S5 of FIG. It is determined that there is an abnormality in detection, and the process proceeds to step S7. Also, if there is one or more data in the lot that is below the LCL or above the UCL, it is determined that there is an abnormality in endpoint detection outside the standard, and the process proceeds to step S7.

  In step S7, the computer 10 displays on the monitor screen 11, for example, the lot ID, the detection required times of the wafers # 1 to # 25 belonging to the lot, the maximum and minimum values of the detection required times, and the ranges thereof. For example, “NG” is displayed as the verification result. Further, an alarm sound is generated from the speaker 13 connected to the computer 10 in order to inform the surroundings of “NG” (ie, end point detection abnormality). After performing Step S6 or Step S7, the flowchart of FIG. 1 is terminated.

  As described above, according to the first embodiment of the present invention, when there is a wafer in the lot in which the end point is erroneously detected and the ashing process is completed in an incomplete state, the existence of the wafer in the lot is determined. It is discovered by the variation in the detection time. If the detection error of the endpoint becomes clear, the progress of the wafer can be stopped and the ashing process can be restarted, or the wafer can be discarded. For example, the resist of the cleaning machine used in the next cleaning process Contamination can be prevented.

  In the first embodiment, the ashing device 1 corresponds to the “single wafer processing device” of the present invention. In addition, the range calculation function (process) realized by the computer 10 in step S4 corresponds to the “means for obtaining the difference between the maximum value and the minimum value” of the present invention, and is within the standard realized by the computer 10 in step S5. The determination function (process) of whether or not corresponds to “means for determining whether or not there is an abnormality in the detection of the end point” of the present invention.

(2) Second Embodiment FIG. 6 is a conceptual diagram showing a configuration example of the ashing device 1, the controller 3, and the process management system 50 that execute the flowchart of FIG. 6, parts having the same functions as those in FIG. 2 are denoted by the same reference numerals, and detailed description thereof is omitted.
In the second embodiment, the process management system 50 performs each process of steps S4 to S7 instead of the computer 10 shown in FIG.
The process management system 50 includes, for example, a plurality of computers 20 arranged outside the clean room, and each computer 20 is wired or connected to each manufacturing apparatus (including the ashing apparatus 1), a transfer apparatus, and the like in the clean room. Connected wirelessly. As with the computer 10 shown in FIG. 2, each computer 20 is composed of, for example, a CPU and a hard disk, etc., and has a function of managing the operating status of each manufacturing apparatus and transfer device in the clean room and the progress status of the lot. Have.

In the second embodiment, in step S6 of FIG. 1, the process management system 50 detects, for example, the lot ID and the wafers # 1 to # 25 belonging to the lot on the monitor screen 21 of at least one computer 20. The required time, the maximum and minimum values of the required detection time, the range thereof, and the characters “OK”, for example, are displayed as the verification result.
On the other hand, in step S7 of FIG. 1, the process management system 50 displays on the monitor screen 21 of at least one computer 20, for example, the lot ID and the required time for detection of each wafer # 1-25 belonging to the lot, The maximum value and the minimum value of the detection required time, the range thereof, and the character “NG”, for example, are displayed as the verification result. Further, in step S7, the process management system 50 stops the progress of the lot determined to be NG (that is, the flow to the next process), and disables the ashing apparatus 1 that has generated NG. Then, the process management system 50 generates an alarm sound from a speaker or the like connected to the computer 20, or distributes an e-mail notifying the occurrence of NG to a related person (operator, engineer, etc.) Informs of abnormal detection.

With such a configuration, it is possible to stop wafers that may not have been completely stripped of photoresist in the ashing process so that they do not flow to the next cleaning process, thus preventing resist contamination of the cleaning machine. be able to.
In the second embodiment, the range calculation function (process) realized by the process management system 50 in step S4 corresponds to the “means for obtaining the difference between the maximum value and the minimum value” of the present invention, and the process management in step S5. The function (process) for determining whether or not the standard is realized by the system 50 corresponds to “means for determining whether or not there is an abnormality in the detection of the end point” of the present invention. Other correspondence is the same as that of the first embodiment.

The flowchart which shows the endpoint verification method which concerns on embodiment of this invention. The figure which shows the structural example (1st Embodiment) of the apparatus which implement | achieves the flowchart of FIG. The figure which shows an example of the data regarding the detection required time of an endpoint. The figure which shows an example in the case of determining within the specification by step S5 of FIG. The figure which shows an example in the case of judging non-standard in step S5 of FIG. The figure which shows the structural example (2nd Embodiment) of the apparatus which implement | achieves the flowchart of FIG.

Explanation of symbols

  1 ashing device, 3 controller, 10, 20 computer, 11, 21 monitor screen, 13 speaker, 50 process management system

Claims (4)

After processing a plurality of wafers belonging to a predetermined lot one by one using a single wafer processing apparatus having an end point detection function, the time required for detecting the end points detected for each wafer in accordance with the processing Is a method for verifying in units of lots,
Obtaining a difference between a maximum value and a minimum value of the time required for detection in the lot;
Determining whether or not there is an abnormality in the detection of the end point in the lot based on the difference. In the step of determining whether there is an abnormality in the detection of the endpoint,
If the difference is greater than the predetermined value, it is determined that there is an abnormality in the detection of the end point in the lot. Otherwise, it is determined that there is no abnormality in the detection of the end point in the lot. The endpoint verification method according to claim 1, wherein:   The endpoint verification method according to claim 1, further comprising a step of notifying an abnormality when it is determined that an abnormality is detected in the detection of the endpoint. After processing a plurality of wafers belonging to a predetermined lot one by one using a single wafer processing apparatus having an end point detection function, the time required for detecting the end points detected for each wafer in accordance with the processing Is a system for verifying in units of lots,
Means for obtaining a difference between a maximum value and a minimum value of the required detection time in the lot;
Means for determining whether there is an abnormality in the detection of the end point in the lot based on the difference.

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