JP4505016B2 - Mask cleaning method and mask cleaning apparatus - Google Patents

Description

  The present invention relates to a mask cleaning method for cleaning contamination of a mask loaded in a container such as a magazine.

  In recent years, mask CD-SEM (a device that inspects the line width of a pattern on a mask using a scanning electron microscope) has many measurement items, and the measurement time of one mask exceeds 10 hours. There is a lot to do.

In the past, each mask was set in the apparatus, and when the measurement work was completed, the operator changed the mask and started the measurement work for the next mask.
Also, in the defect determination method, if the determination of the type of defect is impossible, the determination is suspended, the search is performed again after re-cleaning, and if the previous detection disappears, it is determined as a foreign object and exists at the same position. If so, there is a technique in which an inspector finally determines the type of defect using a scanning electron microscope (Patent Document 1).
JP 2003-185592 A

However, as described above, when the measurement time of one mask exceeds 10 hours, if the operator performs the mask replacement work, the work efficiency is extremely low, and automatic mask replacement is necessary. . For this reason, if a plurality of masks to be measured are set in the above apparatus and left for a long time, the mask surface is exposed to contaminants, and contamination corresponding to the long time adheres to the mask surface. As a result, problems such as an increase in measurement error occurred.
Further, the technique of Patent Document 1 described above involves re-cleaning when it is impossible to determine the type of defect, and there is a problem that contamination such as foreign matter cannot be prevented or removed in advance. It was.

  In order to solve these problems, the present invention measures a plurality of masks loaded in a magazine or other container after taking out and cleaning them in order of priority and measuring time in a short order, or when a predetermined time or more elapses. The mask in the container is taken out, cleaned, and returned to its original position.

  The present invention makes it possible to measure and hold a mask without contamination even when it is loaded in a container such as a magazine for a long time.

  In the present invention, a plurality of masks loaded in a magazine or other container are measured after they are removed and cleaned in the order of priority and measurement time, and the mask in the magazine or other container is removed when a predetermined time or more has elapsed. It was possible to measure and hold the mask without contamination even if it was loaded in a magazine or other container for a long time.

FIG. 1 shows a block diagram of the present invention.
In FIG. 1, a magazine 1 is a carrying box that is loaded with a plurality of masks 2 fixed to a mask holder 3 and is sealed so that dust and the like do not enter from inside the magazine 1.

  The mask holder 3 is a holder for fixing a mask (an original for exposing a pattern on a wafer), and here, an IC tag is attached thereto.

  The pre-exhaust chamber 4 is a room (sealed space) for taking out pre-exhaust by inserting the mask holder 2 to which the mask 2 is fixed, taken out from the magazine 1, and here, a cleaning lamp 41 and a gas introduction mechanism 42. It is a room with etc. When the mask 2 is taken in, preliminary evacuation is performed from atmospheric pressure to about 10 −3 mm Torr, and when discharging, air is introduced from vacuum to atmospheric pressure. During cleaning, a gas (oxidizing gas (for example, air) or inert gas (nitrogen or the like)) is introduced to a predetermined pressure.

  The lamp 41 is for removing contaminants by irradiating the surface of the mask 2 with ultraviolet rays, infrared rays or the like in a state where an oxidizing or inert gas is introduced.

  The gas introduction mechanism 42 introduces gas (oxidizing gas (for example, air, oxygen gas), inert gas (nitrogen, etc.)) into the preliminary exhaust chamber 4 at a predetermined pressure (for example, within 10-2 mmTorr).

  The main chamber 5 is a state in which the mask holder 3 to which the mask 2 is fixed is placed on the stage 51, and here, the electron beam probe narrowed down from the electron optical system 6 is scanned in plane, and the surface of the mask 2 at that time Secondary electrons, reflected electrons, light, etc. emitted from the light, or absorbed electrons are detected by a known detector (not shown), and an image (for example, a secondary electron image) modulated by the brightness is displayed on the display. This is a room (a vacuum room of 10 −6 mm Torr or less).

  The stage 51 is a mechanism for placing the mask holder 3 to which the mask 2 is fixed and moving the mask holder 3 to a predetermined position in any direction (for example, the X direction and the Y direction) with high accuracy.

  The electron optical system 6 generates an electron beam, scans the surface of the mask 2 with a focused and narrowly focused electron beam, and scans the surface of the mask 2 to detect secondary electrons generated at that time. A high-magnification image (for example, a secondary electron image) is displayed on a display (not shown), a fine pattern on the mask 2 is enlarged and displayed, and the widths of patterns at a number of designated positions are automatically measured. Is for.

  The PC 11 is a personal computer that performs various controls according to a program. Here, the PC 11 mainly performs various controls for cleaning the contamination of the mask 2, and includes a priority order determination unit 12, a cleaning control unit 13, and a length measurement. It comprises means 14 and the like.

  The priority order determining means 12 determines the order in which the plurality of masks 2 loaded in the magazine 1 are operated (described later with reference to FIGS. 2, 5, 6, etc.).

  The cleaning control means 13 controls the cleaning of the mask 2 (which will be described later with reference to FIGS. 2, 3, 4, etc.).

  The length measuring means 14 is a known one that automatically measures the line width and the like of the pattern formed on the mask 2.

  Next, the overall operation of the configuration of FIG. 1 will be described in detail according to the order of the flowchart of FIG.

FIG. 2 shows a flowchart for explaining the operation of the present invention.
In FIG. 2, priority is set in S1. This is because the priority of the order of work is set for the mask 2 loaded in the magazine 1, for example, the priority (corresponding to the priority number in the priority table of FIG. (High priority).

  In S2, a magazine is set. This is because, after a mask holder in which a plurality of masks 2 are fixed in a clean room (pre-processing step) (not shown) is loaded in the magazine 1, the magazine 1 is transported to a room of an apparatus (for example, a length measuring apparatus) in FIG. Automatically or by an operator) and set to the position shown in the figure.

  In S3, it starts to be taken out from the magazine. This starts taking out the mask 2 (the mask 2 fixed to the mask holder 3, the same applies hereinafter) from the magazine 1 set at the position shown in S2.

  S4 sorts in order of priority. This sorts the masks 2 loaded in the magazine 1 in the priority order set in S1.

  In S5, re-sorting is performed in consideration of the measurement work time. In this case, after sorting in the priority order in S4, re-sorting is performed in consideration of the measurement work time of the mask 2, for example, re-sorting so as to give priority to a work time that is significantly shorter. Specifically, as shown in FIG. 6C, which will be described later, in the priority order, the mask name B → A⇒C is given priority, A having a significantly shorter work time is given priority, and A⇒B ⇒Resort to C.

  S6 carries. In this process, the first mask 2 in the order determined in S5 is taken out from the magazine 1 and transferred to the preliminary exhaust chamber 4 for preliminary exhaust.

  In S7, cleaning 1 is performed. According to the flowchart of FIG. 3 described later, after introducing gas into the preliminary exhaust chamber 4 at a predetermined pressure, the lamp 41 is turned on to irradiate the surface of the mask 2 with ultraviolet rays to remove contaminants on the surface. Remove and clean.

  S8 carries. This is because after the cleaning 1 is completed in S7, preliminary exhaust of the preliminary exhaust chamber 4 is performed again to make the vacuum as high as possible, and then the gate valve between the preliminary exhaust chamber 4 and the main chamber 5 is opened. Then, the mask 2 is transferred to the position of the main chamber 5 where the measurement work is illustrated.

  In S9, measurement is started. This is designated on the mask 2 placed on the stage 51 in FIG. 1 (more precisely, the mask 2 placed on the stage 51 and fixed to the mask holder 3, and so on). Start length measurement such as the width of the specified location of the pattern.

  S10 ends the measurement. This starts the measurement in S9 and ends the length measurement of all the places of all the designated patterns. Usually it takes 10 minutes at the fastest and 10 hours or longer at the longest.

  S11 returns to the magazine. This transports the mask 2 that has been completed in S10 to the preliminary exhaust chamber 4, and further transports it back to a predetermined position (usually the original position) of the magazine 1. Here, to return to the magazine 1, more precisely, the preliminary exhaust chamber 4 has a predetermined high vacuum for the mask 2 (the mask 2 fixed to the mask holder 3) placed on the stage 51 of FIG. 1. After confirming that, the gate valve between the preliminary exhaust chamber 4 and the main chamber 5 is opened, the mask 2 is transferred to the preliminary exhaust chamber 4, and then the gate valve is closed. And after putting dry air (or dry nitrogen gas) into the preliminary exhaust chamber 4 to atmospheric pressure, the gate valve between the preliminary exhaust chamber 4 and the magazine 1 is opened, and the mask 2 is conveyed to a predetermined position of the magazine 1. Put it back in.

  In S12, it is determined whether or not the end. This determines whether or not the length measurement operation has been completed for all the masks 2 in the magazine 1. If YES, the process ends. If NO, return to S4 and repeat for the next mask 2.

  As described above, the PC 11 in FIG. 1 performs the control from S4 to S12 only by automatically setting the magazine 1 loaded with a plurality of masks 2 at a predetermined position in the preliminary exhaust chamber 4 of the apparatus in FIG. 1 (or by an operator). After the mask 2 is taken out and cleaned in order of priority, the operation (here, the length measurement operation) is repeated, and the operation is automatically repeated until all operations are completed. Work). At this time, prior to the length measurement, gas can be automatically introduced into the surface of the mask 2 and the length can be measured after removing contaminants by irradiating the ultraviolet rays from the lamp 41. It is possible to automatically perform the length measurement.

  In addition, although gas was introduced into the preliminary exhaust chamber 4 and ultraviolet rays were irradiated from the lamp 41 to remove contaminants on the surface of the mask 2, the mask 2 was placed in another adjacent room different from the preliminary exhaust chamber 4. Contaminants on the surface of the mask 2 may be removed by transporting the gas and irradiating the lamp 41 with ultraviolet rays. In this case, the preliminary exhaust chamber 4 of the apparatus is made the same as the conventional one, and a new chamber is provided to introduce a mechanism for introducing gas and irradiating the surface of the mask 2 with ultraviolet rays from the lamp 41 and an automatic transport mechanism. This can be realized with a configuration only by adding.

  FIG. 3 is a flowchart for explaining the operation of the present invention (cleaning 1). This is a detailed flowchart of the cleaning 1 in S7 of FIG.

In FIG. 3, gas is introduced in S21. In this state, in a state where the mask 2 is transferred to the preliminary exhaust chamber 4 of FIG. 1, the preliminary exhaust chamber 4 is once exhausted with air, and then the gas is introduced. As described on the right side,
Oxidizing gas: for example, oxygen, air, etc. Inert gas: Argon, nitrogen, or the like is introduced to a predetermined pressure (for example, a predetermined pressure from atmospheric pressure to 10-6 Pascal level) or a continuous trace amount is introduced.

S22 irradiates ultraviolet rays and infrared rays. this is,
For example, the surface of the mask 2 is irradiated with a deuterium lamp that emits a wavelength of 400 nm or less to about 172 nm,
For example, the surface of the mask 2 is irradiated with a YAG laser that generates a wavelength of about 1064 nm. The irradiation time is set by experimentally determining the time during which contaminants on the surface of the mask 2 can be removed (usually within a range of several minutes to 60 minutes).

In S23, the cleaning is completed.
As described above, in a state where the mask 2 is conveyed to the preliminary exhaust chamber 4 of FIG. 1, the gas is introduced, the surface of the mask 2 is irradiated with ultraviolet rays and infrared rays from the lamp 41 and the like, and the mask is activated by the activated gas. It is possible to remove the contaminants on the surface of the gas 2 by gasification and to clean the surface of the mask 2.

  FIG. 4 is a flowchart for explaining the operation of the present invention (cleaning 2). This shows the details of the process for cleaning the surface of the mask 2 every time a predetermined time or a predetermined time elapses when the mask 2 loaded in the magazine 1 of FIG. 1 stays for a long time.

  In FIG. 4, S31 discriminates whether there is a mask 2 that has not been measured and that has passed a predetermined time or more. This is because the mask 2 loaded in the magazine 1 in FIG. 1 is not measured (unworked), and the mask 2 is loaded in the magazine 1 (or the magazine 1 is set in the preliminary exhaust chamber 4 or the mask 2 is mask holder) 1), the date and time of the starting point is recorded on the IC tag attached to the mask holder 3 or the mask 2 and read out, or the date and time of the starting point is recorded in the hard disk device of the PC 11 in FIG. It is determined whether there is a mask 2 that has passed a predetermined time. If YES, the process proceeds to S32. If NO, the process ends.

  S32 takes out. This takes out the mask 2 that has become YES in S31 and conveys it into the preliminary exhaust chamber 4 of FIG.

  In S33, cleaning 1 is executed. In this process, cleaning 1 (S21 to S23) is executed in accordance with the flowchart of FIG. 3 described above to remove contaminants on the surface of the mask 2.

  S34 returns. In S33, the contaminants on the surface of the mask 2 are removed by the cleaning 1 in S33, and then the mask 2 is returned to the magazine 1.

  In S35, it is determined whether the process is over. If YES, the process ends. In the case of NO, S31 and subsequent steps are repeated for the next mask 2 loaded in the magazine 1.

  As described above, after the magazine 1 of FIG. 1 is set in the preliminary exhaust chamber 4, the unworked mask 2 that has passed for a predetermined time is transported to the preliminary exhaust chamber 4 to remove contaminants on the surface of the mask 2. By returning later, it is possible to solve the problem that contaminants accumulate on the surface of the mask 2 staying in the magazine 1 as time passes, and always automatically keep the surface of the mask 2 in a clean state. It becomes possible.

  FIG. 5 is a flowchart for explaining the operation of the present invention. This shows an example of a detailed flowchart for determining the work order of the mask 2 based on the priority and the processing time.

  In FIG. 5, S41 determines whether there is a measurement within 30 minutes. This is, for example, a measurement (work) time set in association with the mask name of the mask 2 loaded in the magazine 1 in FIG. 1 set in the priority table in FIG. Determine if there is something within 30 minutes. Within 30 minutes corresponds to a very short working time in the measurement (work) targeted here. If YES in S41, the process proceeds to S42. In the case of NO, since it has been found that there is no mask 2 with a short measurement (work) time, it is left as it is (in order of priority) in S43, and the process ends.

  In S42, since the measurement (work) time of the mask 2 is found to be within 30 minutes in YES of S41, it is further determined whether the priority is the first. In the case of YES, since the priority is the highest and the priority is given, it is left as it is in S43 (in the order of priority), and the process ends. On the other hand, in the case of NO in S42, since it has been determined that the priority is not the first, it is replaced in S44, that is, the priority of the mask 2 that has been determined to be within 30 minutes, and here the mask of the first priority. Swap the priority of 2. Specifically, the work order of the mask 2 in FIG. 6 (c-1), B⇒A⇒C, is changed to A⇒B⇒C in FIG. 4 (c-2) (B and A). In reverse order).

  As described above, the mask 2 loaded in the magazine 1 is normally measured (worked) in order of priority, but the time required for measuring (working) the mask 2 is short (in this case, for example, 30 minutes or less). In this case, for the mask 2 of the short measurement (time), here, when the priority is not No. 1, the order is changed with the mask 2 of other priority No. 1, and the measurement (work) is performed first, It is possible to eliminate the situation where the mask 2 having a short measurement (working) time is kept waiting for a long time in the magazine 1 and the contaminants accumulate. For the mask 2 that has not been measured (unworked) and stayed in the magazine 1 for a long time, the surface of the mask 2 is cleaned at predetermined time intervals in accordance with the flowchart of FIG. It becomes possible not to deposit on the surface of 2.

FIG. 6 is an explanatory diagram of the present invention.
FIG. 6A shows an example of a priority table. The priority table 7 registers and manages the following information in association with the mask names of the masks 2 loaded in the magazine 1 of FIG. 1 described above.

・ Mask name:
·priority:
・ Measurement (working) time:
・ Other:
Here, the mask name is a unique name for identifying the mask 2 loaded in the magazine 1 of FIG. The priority is a priority of measurement (work) of the mask 2 identified by the mask name, and indicates that the priority is higher in the order of 1, 2, 3,. The measurement (work) time is a time (estimated approximate time) required for measurement (work) of the mask 2 identified by the mask name.

  As described above, by setting the priority and the measurement (working) time in advance for the mask 2 loaded in the magazine 1 in FIG. 1 (set in S1 in FIG. 2 described above), a plurality of masks in the magazine 1 are set. Measurement (work) is performed in order of priority with respect to No. 2, and measurement (work) is given priority when the measurement (work) time is short (here, within 30 minutes) as shown in the flowchart of FIG. ) And the measurement (operation) can be performed quickly without the accumulation of contaminants on the mask 2 which requires a short measurement (operation) time.

FIG. 6B shows an example of a condition table. The condition table 8 sets conditions for executing measurement (work) in preference to the other masks 2 when the measurement (work) time is short.
When setting whether there is a measurement within 30 minutes, the condition is set in S41 of FIG. 5 described above, and the measurement (work) of the mask 2 within 30 minutes can be preferentially executed. (See the flowchart in FIG. 5 and its description).

FIG. 6C shows an example of replacement. This is based on the flowchart of FIG. 5 described above in which the conditions of the condition table 8 of FIG. 6B are set based on the priority table 7 of FIG.
・ Simply in order of priority, as shown in (c-1) of FIG. 6 ・ B⇒A⇒C
Perform measurements (work) in the order of, but
When the measurement (work) time is within 30 minutes and the conditions for performing measurement (work) preferentially (conditions (b) in FIG. 6) are set, the flow chart in FIG. 6 (c-2) Show ・ A⇒B⇒C
It becomes.

  As described above, when there is a mask 2 with a short measurement (work) time (here, within 30 minutes set in the condition table 8 in FIG. 6B), the measurement (work) is preferentially executed. By doing so, it is possible to prevent the deposition of contaminants on the surface of the mask 2 which requires only a short measurement (work) time and to perform measurement (work) quickly.

FIG. 7 shows an example of an IC tag and IC tag information of the present invention.
FIG. 7A shows an example in which an IC tag is attached to the mask holder 3. The IC tag 9 can read and write data wirelessly, and is attached to the mask holder 3 here. The IC tag 9 may be directly attached to the back surface of the mask 2 or the like.

  FIG. 7B shows an example of information recorded on the IC tag 9. The following information shown in the figure is read from and written to the IC tag 9 wirelessly.

・ ID:
・ Mask name:
・ Date:
・ Date and time set in the mask holder 3:
・ Date and time when mask 2 was set in magazine 1:
・ Date and time set in the device ・ Date and time of cleaning ・ Others:
Here, the ID is an ID for uniquely identifying the IC tag 9. The mask name is the mask name of the mask 2 to which the IC tag 9 is attached. The date and time are the date and time when the mask 2 is set in the mask holder 3, the date and time when the mask 2 is set in the magazine 1, the date and time when the magazine 1 is set in the apparatus (apparatus in FIG. 1), and the date and time when the mask 2 is cleaned (washed). is there.

  As described above, by attaching the IC tag 9 to the mask 2 (or the mask holder 3 to which the mask 2 is fixed) to be loaded in the magazine 1 and writing the mask name and date, the magazine as shown in FIG. When 1 is set at the position shown in the figure, information (mask name and date / time) of the mask 2 loaded in the magazine 1 is read out, and in order of priority and further, the measurement (work) time is short. Measurement (work) can be prioritized. At this time, cleaning is performed immediately before the measurement (operation) and the surface of the mask 2 is cleaned for measurement, or when the mask 2 stays in the magazine 1 for a predetermined time or more (or every time the mask 2 stays for a predetermined time or more). The surface of the mask 2 can be automatically kept clean by taking it out and cleaning it (cleaning, see FIG. 4).

  In the case where the mask 2 stays in the magazine 1, the cleaning is performed (FIG. 5). However, the mask 2 in the magazine 1 is moved to another room (container) and held (stayed). Similarly, the present invention can be applied to the cleaning of contaminants deposited on the surface of the mask 2 in the separate room even when the mask 2 is sequentially taken out from and the measurement (operation) is executed.

  The present invention relates to a mask cleaning method for measuring and holding a mask without contamination even when the mask is loaded into a container such as a magazine for a long time.

It is a block block diagram of this invention. It is an operation | movement explanatory flowchart of this invention. It is operation | movement description flowchart (cleaning 1) of this invention. It is operation | movement description flowchart (cleaning 2) of this invention. It is an operation | movement explanatory flowchart of this invention. It is explanatory drawing of this invention. It is an IC tag and IC tag information example of this invention.

Explanation of symbols

1: magazine 2: mask 3: mask holder 4: preliminary exhaust chamber 41: lamp 42: gas introduction mechanism 5: main chamber 51: stage 6: electron optical system 7: priority table 8: condition table 9: IC tag 11: PC (PC)
12: Priority order determining means 13: Cleaning control means 14: Length measuring means

Claims (5)

In a mask cleaning method for cleaning contamination of a mask loaded in a container such as a magazine,
Sorting a plurality of masks loaded in a container such as a magazine based on one or both of priority order and work time, and determining the work order;
Among masks loaded in containers such as the magazine, the mask working time is allowed to accumulate contaminants on the mask surface, and the mask is loaded into the mask holder or the mask holder is loaded into the magazine or washed. If a mask shorter than the first predetermined time is found, the working order of the mask is preferentially determined, or a mask loaded in a container such as the magazine or an unworked mask is cleaned. A step of performing either one or both of when the second predetermined time has passed or when the second predetermined time has passed and taken out and washed and then returned to a container such as a magazine;
Taking out the mask in the order of the determined work, transporting it to the apparatus main body or transporting it to the apparatus main body, and performing the work;
And a step of transporting the mask back to a container such as the magazine when the operation is completed. 2. The mask cleaning method according to claim 1, wherein the second predetermined time is the same as the first predetermined time .   The cleaning of the mask is characterized by irradiating the surface of the mask with ultraviolet rays or infrared rays with an oxidizing gas or an inert gas introduced in the vicinity of the mask to remove contaminants attached to the surface of the mask. The mask cleaning method according to claim 1 or 2. Old claim 4
An IC tag that reads and writes wirelessly is attached to a mask holder that holds the mask or the mask itself, and stores one or more of the priority, the work time required for the work, and the cleaning time for washing. The mask cleaning method according to any one of claims 1 to 3. In a mask cleaning device for cleaning contamination of a mask loaded in a magazine or other container,
  A means for determining a work order by sorting based on one or both of a priority order and a work time for a plurality of masks loaded in a container such as a magazine;
  Among masks loaded in containers such as the magazine, the mask working time is allowed to accumulate contaminants on the mask surface, and the mask is loaded into the mask holder or the mask holder is loaded into the magazine or washed. If a mask shorter than the first predetermined time is found, the working order of the mask is preferentially determined, or a mask loaded in a container such as the magazine or an unworked mask is cleaned. Means for performing either one or both of when the second predetermined time elapses or after every second predetermined time elapses to be taken out and washed and then returned to a magazine or the like;
  Means for taking out the mask in the determined work order, transporting it to the apparatus main body or transporting it to the apparatus main body, and performing the work;
  Means for transporting the mask back to a container such as the magazine when the operation is completed after completion;
A mask cleaning apparatus comprising:

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