JP2005191328A - Mask, mask contamination monitor method, program and exposure method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mask where collected mask contamination can be easily monitored, and to provide a mask contamination monitor method, an exposure method, and an associated program. <P>SOLUTION: A mask is provided with a copy pattern formation region to be duplicated to a film for exposure and is available to monitor the amount of contamination collected when the copy pattern formation region is duplicated to the film for exposure. It is also provided with a monitor pattern formation area formed by placing multiple openings in the surrounding of the copy pattern formation region. A monitor pattern is formed in such a way that multiple openings are placed in a region whose diameter is greater than a beam diameter in each exposure beam. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a mask, a mask contamination monitoring method, a program, and an exposure method, and more particularly, to a mask in which a pattern is formed by an opening, and a mask contamination monitoring method, a program, and an exposure method using the mask.

  As a next-generation semiconductor lithography technology, development of an exposure apparatus using a charged particle beam such as an electron beam and an ion beam, which is excellent in fine processability as compared with a photolithography technology, is in progress.

  In an exposure apparatus using an electron beam, an electron beam direct writing apparatus has been developed from an early stage, and has been widely put into practical use for producing a photomask or a reticle. In an electron beam direct writing apparatus, techniques such as a variable shaped beam and a partial batch exposure method for improving the throughput from a so-called one-stroke writing method using a point beam are generally used. The electron beam direct writing apparatus performs exposure using a mask in which a stencil pattern is formed on a membrane of about 10 to 30 μm.

Other examples of the exposure technique using an electron beam include PREVAIL (Projection Exposure with Variable Axis Impression Lenses) or LEEPL (Low) that transfers a pattern formed on a mask onto a wafer.
Energy Electron-beam Proximity Projection Lithography) (for example, see Non-Patent Documents 1 and 2). The exposure technique uses a mask in which a stencil pattern is formed on a membrane having a thickness of about 0.1 to 10 μm. Similar masks have also been proposed for ion beam exposure.

  In common with the above-described exposure technique, there is a problem that hydrocarbon-based contaminants (hereinafter also referred to as contamination) are deposited or deposited when the mask is irradiated with a beam. If contamination adheres to the stencil mask or grows, the opening size of the transfer pattern formed on the mask narrows and the shape of the opening deteriorates. May cause. Therefore, in order to maintain resolution and dimensional accuracy, it is necessary to monitor the mask management, that is, monitor the amount of accumulated contamination of the mask, and appropriately estimate the timing of cleaning and replacement of the mask.

The amount of contamination deposition is considered to be determined by various factors such as the degree of vacuum in the region where transfer is performed, the amount of outgas from the sample, and exposure conditions, and it is difficult to predict the amount of adhesion in advance quantitatively.
For this reason, in order to estimate the contamination accumulation amount of the mask and the replacement time, a method of evaluating the actually exposed transfer pattern is generally performed. However, this method requires time for inspection, and it is difficult to quantify the amount of contamination.

Therefore, a method of monitoring the amount of contamination by applying a constant voltage to the mask and measuring the amount of charge accumulated in the contamination portion (see, for example, Patent Document 1), a light beam irradiation means and reflected light in the exposure apparatus. A method for evaluating a contamination film by incorporating a measuring device or an element analyzer (for example, see Patent Document 2), or a method for quantifying contamination by spectroscopic analysis by irradiating mask excitation light in an exposure device (for example, a patent Reference 3) has been proposed.
However, it is necessary to provide a mechanism specialized for the measurement of the amount of contamination, and there is a disadvantage that the mechanism of the apparatus becomes complicated and a lot of cost is required.
H. C. P. Pfeiffer, “Journal of Vacuum Science and Technology (J. Vac. Sci. Technol.)” B17, p. 2840 (1999) T.A. T. Utsumi, “Journal of Vacuum Science and Technology (J. Vac. Sci. Technol.)” B17, p. 2897 (1999) JP-A-6-275502 Japanese Patent Laid-Open No. 9-134861 JP 2001-358046 A

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a mask that can easily monitor the amount of contamination accumulated in the mask, a mask contamination monitoring method, a program, and an exposure method using the mask. There is to do.

  In order to achieve the above object, the mask of the present invention described above is a mask in which a transfer pattern to be transferred to a film to be exposed is formed by an opening, and a plurality of openings are arranged in the periphery of the transfer pattern. The monitor pattern is formed as described above.

  According to the mask of the present invention, since the monitor pattern is composed of a plurality of openings, the variation of the openings due to the adhesion of contamination is large.

  In order to achieve the above object, the mask contamination monitoring method of the present invention described above is a mask contamination monitor for monitoring the contamination deposited on the mask by the exposure for transferring the transfer pattern formed on the mask onto the film to be exposed. A method of irradiating a mask with a charged particle beam and measuring a first current value of the charged particle beam that has passed through the monitor pattern; and after performing exposure, the mask is irradiated with the charged particle beam. The step of measuring the second current value of the charged particle beam that has passed through the monitor pattern, the line width of the pattern obtained in advance, the first current value, and the second current value are used. And a step of calculating a deposition amount of nation.

According to the mask contamination monitoring method of the present invention, a charged particle beam is irradiated onto the mask, and the first current value of the charged particle beam that has passed through the monitor pattern is measured.
Next, after exposure, the mask is irradiated with a charged particle beam, and the second current value of the charged particle beam that has passed through the monitor pattern is measured.
Next, the contamination deposition amount of the mask is calculated using the line width of the pattern obtained in advance, the first current value, and the second current value.

  In order to achieve the above object, the above-described program of the present invention is a program for estimating the cleaning time of a mask on which contamination accumulates when a pattern is transferred to an exposed film, and is measured through a predetermined pattern of the mask. Calculating a first aperture ratio and a second aperture ratio from the first current value and the second current value of the charged particle beam, a line width of the monitor pattern inputted in advance, Calculating the amount of contamination deposited on the monitor pattern based on the aperture ratio and the second aperture ratio; and determining whether to perform mask cleaning based on the calculated amount of contamination. Have.

According to the program of the present invention, first, the first aperture ratio and the second aperture ratio are calculated from the first current value and the second current value of the charged particle beam measured through the predetermined pattern of the mask. To do.
Next, the amount of contamination deposited on the monitor pattern is calculated from the line width of the monitor pattern obtained in advance, the first aperture ratio, and the second aperture ratio.
Next, based on the calculated amount of contamination, it is determined whether or not to clean the mask.

  In order to achieve the above object, an exposure method of the present invention is an exposure method for transferring a transfer pattern formed on a mask onto a film to be exposed, and irradiating the mask on which the monitor pattern is formed with a charged particle beam. Measuring the first current value of the charged particle beam that has passed through the monitor pattern, irradiating the charged particle beam through the mask, and transferring the transfer pattern onto the film to be exposed; Irradiating with a charged particle beam to measure the second current value of the charged particle beam that has passed through the monitor pattern, the line width of the monitor pattern, the first current value and the A step of calculating a deposition amount of the mask contamination using the current value of 2, a step of setting exposure conditions in accordance with the contamination deposition amount, and transfer to the film to be exposed based on the set exposure conditions pattern And a step of transferring.

According to the exposure method of the present invention, a charged particle beam is irradiated onto a mask on which a monitor pattern is formed, and the first current value of the charged particle beam that has passed through the monitor pattern is measured.
Next, the transfer pattern is transferred to the film to be exposed by irradiating the charged particle beam through a mask.
Next, the charged particle beam is irradiated to the mask, and the second current value of the charged particle beam that has passed through the monitor pattern is measured.
Next, the contamination accumulation amount of the mask is calculated using the line width of the monitor pattern obtained in advance, the first current value, and the second current value.
Next, exposure conditions are set according to the amount of contamination deposition.
Next, the transfer pattern is transferred to the film to be exposed based on the set exposure conditions.

According to the mask of the present invention, the amount of contamination deposited on the mask can be easily monitored.
According to the mask contamination monitoring method of the present invention, the amount of contamination deposited on the mask can be easily monitored.
According to the program of the present invention, it is possible to easily monitor the amount of contamination deposited on the mask.
According to the exposure method of the present invention, the amount of contamination deposited on the mask can be easily monitored.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  FIG. 1 is a schematic block diagram showing an example of an electron beam exposure apparatus according to this embodiment. In the present embodiment, an electron beam exposure apparatus used for LEEPL is shown as an example.

  The exposure apparatus 1 according to the present embodiment includes an electron gun 2, a limiting aperture 3, a converging lens 4, a pair of main deflectors 6 and 7, a pair of fine adjustment deflectors 8 and 9, and a stencil mask 10. A holder 12 that holds the wafer 11 to be exposed, a stage 13 on which the holder 12 is mounted, a Faraday cup 14 mounted on the stage 13, a control unit 16, and a storage unit 17.

The electron gun 2 emits an electron beam EB. The energy of the electron beam EB used for LEEPL is, for example, 1 to 4 keV, and preferably 2 keV.
The limiting aperture 3 has an opening for making the electron beam EB a desired shape, and shapes the cross-sectional shape of the electron beam EB emitted from the electron gun 2.

  The converging lens 4 collimates the electron beam EB formed by the limiting aperture 3. The cross-sectional shape of the electron beam EB condensed by the converging lens 4 is usually circular, but may be other cross-sectional shapes. In addition, the beam diameter of the electron beam EB according to the present embodiment is, for example, about 600 μm to 1 mm.

The main deflectors 6 and 7 deflect the electron beam EB so that the electron beam EB is perpendicularly incident on the stencil mask 10 while being parallel. The main deflectors 6 and 7 deflect the electron beam EB in either the raster or vector scan mode.
The fine adjustment deflectors 8 and 9 further deflect and finely adjust the electron beam EB changed by the main deflectors 6 and 7.
The main deflectors 6 and 7 and fine adjustment deflectors 8 and 9 are constituted by, for example, deflection coils.

  The stencil mask 10 is disposed close to a wafer 11 that is an object to be exposed. The distance between the stencil mask 10 and the wafer 11 is, for example, 50 μm. The transfer pattern formed on the stencil mask 10 is transferred to the resist formed on the wafer 11 at the same magnification.

The holder 12 holds the wafer 11 and is mounted on the stage 13.
The stage 13 is movable in the parallel direction, and performs positioning control of the wafer 11 with respect to the stencil mask 10. The stage 13 is realized by a combination of a mechanical stage and a motor.

The Faraday cup 14 is mounted on the stage 13, and a current detector 15 is provided between the Faraday cup 14 and the ground line.
The current detector 15 detects a beam current caused by the electron beam EB flowing into the Faraday cup 14. The current detector 15 includes an amplifier circuit that converts a beam current into a voltage and amplifies it, and an analog / digital converter circuit that performs analog / digital conversion on the amplifier circuit. The current detector 15 is connected to the control unit 16. The current detector 15 outputs detected current data to the control unit 16.

  The storage unit 17 is connected to the control unit 16. The storage unit 17 stores a program and the like, and outputs the stored program to the control unit 16 according to an instruction from the control unit 16. In the present embodiment, the storage unit 17 has an exposure program 18, and one embodiment of the program of the present invention corresponds to the exposure program 18.

  The control unit 16 is connected to the electron gun 2, main deflectors 6 and 7, fine adjustment deflectors 8 and 9, stage 13, current detector 15 and storage unit 17. The control unit 16 controls the irradiation of the electron beam EB based on a program from the storage unit 17 or the like. Similarly, the control unit 16 controls the main deflectors 6 and 7 and the fine adjustment deflectors 8 and 9 to deflect the irradiated electron beam EB. The control unit 16 controls, for example, the position adjustment of the stage 13 and the loader and unloader of the wafer 11. The control unit 16 is realized by, for example, a CPU.

  FIG. 2 is a schematic plan view showing one embodiment of a mask according to the present invention.

  As shown in FIG. 2, the stencil mask 10 according to the present embodiment includes a transfer pattern forming region 40 where a transfer pattern is formed and a monitor pattern forming region 50 where a monitor pattern is formed.

  The transfer pattern formation region 40 is formed in a central portion of a membrane having a diameter of about 200 mm and a thickness of about 0.1 to 10 μm, for example, to 40 to 50 mm □.

  The monitor pattern formation region 50 is disposed on the outer periphery of the stencil mask 10 and is formed larger than the beam diameter of the electron beam EB of the electron beam exposure apparatus 1 described above. The monitor pattern formation region 50 is formed, for example, at 600 μm to 1 mm □. In the stencil mask 10, this is not the case when the monitor pattern formation region 50 cannot be made larger than the beam diameter of the electron beam 2 due to restrictions on the arrangement of patterns. The position where the monitor pattern formation region 50 is provided will be described later.

  3A is a perspective view showing a main part of the transfer pattern formed on the stencil mask shown in FIG. 2, and FIG. 3B is a cross-sectional view of the transfer pattern forming region 40 of the stencil mask 10. It is.

  As shown in FIG. 3, a pattern forming film 21 is formed by being supported by the reinforcing beam portion 20, and holes 22 having a predetermined pattern are formed in the pattern forming film 21 excluding the region where the reinforcing beam portion 20 is formed. It is formed through. In the illustrated example, an etching stopper film 23 is formed between the reinforcing beam portion 20 and the pattern forming film 21. Here, the transfer pattern of the present invention corresponds to a predetermined pattern formed through.

  4A is a schematic plan view showing a monitor pattern forming region formed on the stencil mask 10 shown in FIG. 2, and FIG. 4B is an enlarged view showing an example of an opening of the monitor pattern. It is a top view.

As shown in FIG. 4, the monitor pattern includes a plurality of openings 52 arranged in the monitor pattern forming region 50. The side a of each opening 52 is preferably a shape whose opening size changes greatly due to the accumulation of contamination, that is, a square shape close to a square as shown in FIG. . In addition, the opening size of each opening 52 changes more sensitively as its side a is smaller. Furthermore, it is desirable that the interval (pitch) b in which the openings 52 are arranged be as narrow as possible within the range in which the openings 52 can be formed in the stencil mask 10.
Therefore, the side a of the opening is about 60 nm to 150 nm □, and the arrangement pitch b of the openings is about 1.5 to 2.5 times the opening size.
Further, it is desirable that the monitor pattern formed by the plurality of openings 52 is larger than the beam diameter of the exposure beam. For example, one side of the monitor pattern formation region 50 is about 600 μm to 1 mm.

  Here, the monitor pattern formation area 50 is 1) an area where the monitor pattern formation area may be transferred to the wafer during exposure, such as a scribe line, or 2) an area where the electron beam EB of the exposure apparatus can be deflected. In this case, the transfer pattern is formed in an area excluding the transfer area.

  In the case of the above 1), since there is a restriction on the area of the pattern that can be arranged, there is a possibility that inconvenience may arise in arranging the monitor pattern forming region 50 having the same beam diameter as described above. In this case, for example, the monitor pattern formation region 50 is formed in the maximum region that can be arranged on the scribe line.

  Further, in the case of 2), the area restriction as in 1) is eliminated. However, in the normal process of transferring the transfer pattern of the stencil mask 10 to the wafer 11 using the exposure apparatus, the monitor pattern is formed outside the transfer area, so that the electron beam is irradiated to the monitor pattern forming area 50. Not. As a result, the same level of contamination as the transfer pattern formation region 40 is not deposited in the monitor pattern formation region 50. Therefore, after the transfer is completed at the time of exposure and the wafer 11 is removed from the stage 13 of the exposure apparatus 1, the exposure amount required for the transfer of the transfer pattern is irradiated to the monitor pattern forming region 50.

FIG. 5 is a graph showing the presence / absence of a resist film and the amount of contamination deposited during exposure.
Here, the horizontal axis indicates the distance from the center of the mask, and the vertical axis indicates the amount of contamination deposited on the mask. A solid line indicates a case where a wafer on which a resist film is formed is exposed through a mask, and a broken line indicates a case where a wafer on which a resist film is not formed is exposed through a mask.

As shown in FIG. 5, even if a resist film is not formed on the wafer to be exposed, it is possible to deposit almost the same amount of contamination as the wafer 11 on which the resist film is formed. Even if the wafer 11 on which the resist film is formed is not on the stage 13, the same result can be predicted.
In the case of 2), since the monitor pattern forming region 50 can be formed isolated from the transfer pattern forming region 40, a width for scanning the electron beam EB can be secured.

  FIG. 6A is a schematic view showing an example of one opening 52 constituting the monitor pattern, and FIG. 6B shows that contamination is attached to the opening 52 shown in FIG. FIG.

FIG. 6A shows an opening 52 constituting a monitor pattern at a first time, and the opening 52 is a substantially square having the first line width A1 and the first opening ratio S1 as described above. The pattern is formed.
FIG. 6B shows the opening 52 at the second time, and contamination is deposited on the opening 52 by the deposition amount d. As a result, the second line width A2 of the substantial opening of the opening 52 is smaller than the first line width A1. For this reason, the second aperture ratio S2 after the contamination has adhered becomes smaller than the aperture ratio S1 shown in FIG.

  Here, since the line width A1 of the opening 52 in the initial monitor pattern is formed smaller than the line width of the transfer pattern, even if the contamination accumulation amount is substantially the same, The variation in line width is larger.

  FIG. 7A is a schematic view showing another example of one opening 52 constituting the monitor pattern, and FIG. 7B shows contamination in the opening 52 shown in FIG. It is the schematic which shows a mode that was attached.

The opening 52 constituting the monitor pattern shown in FIG. 7A is a hole-shaped pattern having the line width A′1 and the aperture ratio S′1 as described above.
As shown in FIG. 7B, when contamination adheres to the opening 52, the line width A′2 of the substantial opening of the opening 52 becomes small. As a result, the aperture ratio S′2 after the contamination is attached becomes smaller than the aperture ratio S′1 shown in FIG.

Since the hole shape as described above can be used as the opening 52, it can also be used when the pattern shape is deteriorated in the mask manufacturing process and the opening 52 constituting the monitor pattern becomes the hole shape. Further, as the opening 52, a pattern such as a rhombus can be used in addition to the substantially square shape and the hole shape shown in FIGS.
For example, since the rhombus opening has a sharp portion, it has an advantage that it is more sensitive to adhesion of contamination than a square, but the contamination accumulates on the sharp portion and rounds (corner rounding). Another disadvantage is that it is difficult to estimate the impact.

  Next, a mask contamination monitoring method for monitoring pattern deterioration due to contamination on the stencil mask 10 using the mask according to the present invention will be described with reference to the drawings.

  FIG. 8 is a flowchart showing the steps of the mask contamination monitoring method according to this embodiment. In the mask contamination monitoring method according to the present embodiment, the above exposure apparatus and mask are used.

  Further, the mask contamination monitoring method of the present embodiment is executed by the exposure program 18 incorporated in the storage unit 17 of the electron beam exposure apparatus 1. The exposure program 18 is read from the storage unit 17 of the electron beam exposure apparatus 1 to the control unit 16 and executed under the control of the control unit 16.

First, the line width A of the opening in the monitor pattern is measured with respect to the unused stencil mask 10 immediately after cleaning (ST21).
The line width A of the opening in the monitor pattern of the mask 10 can be measured by a length measuring machine such as a length measuring scanning electron microscope.

At this time, the number of processing sheets N _B and acceptable contamination deposition amount threshold d _B
Is preset. Processing number N _B, for example, 20 to 30 wafers as one lot, each lot is processed number N _B in one step is set. In this case, the threshold value d _B of contamination deposit amount is, for example, a 5 nm. The set value is output to the control unit 16 of the electron beam exposure apparatus 1.

Next, the first current value I ₁ of the electron beam 2 irradiated through the monitor pattern forming region 50 of the stencil mask 10 which has not been used or just cleaned is measured (ST22).
The control unit 16 gives a command to the electron gun 2 to irradiate the electron beam EB, and detects the beam current value irradiated to the Faraday cup 14 via the mask 10 via the current detector 15.
At this time, the beam intensity of the electron beam EB is not uniform with respect to the mask surface, and generally has the highest electron density at the center of the beam as approximated by a Gaussian distribution. Therefore, in order to improve reproducibility, it is necessary to substantially match the center of the electron beam EB with the center of the monitor pattern formation region 50.

Specifically, the control unit 16 performs control so that the center of the electron beam EB is gradually shifted via the main deflectors 6 and 7 and the fine adjustment deflectors 8 and 9. As a result, the electron beam EB scans over the monitor pattern forming region 50 of the stencil mask 10. The current detector 15 measures the current value and outputs the measured current value to the control unit 16. Here, the value at the time when the current value becomes the largest is defined as the first current value I ₁ .
Alternatively, an opening 52 having an opening shape different from that of the peripheral portion is arranged at the center of the monitor pattern formation region 50, and the beam is observed while observing an image taken by a scanning electron microscope when the electron beam EB is irradiated. The position of the electron beam EB is set so that the center and the pattern center substantially coincide with each other, and the current value at that time is defined as a first current value I ₁ .
When the monitor pattern forming area 50 is arranged as in 2) above, the control unit 16 scans the monitor pattern forming area 50 with the electron beam EB so that the beam irradiation amount is uniform. Is possible.

Next, the transfer pattern formed on the stencil mask 10 is transferred to the wafer 11 (ST23).
The control unit 16 irradiates the stencil mask 10 with the electron beam EB. As a result, the transfer pattern formed on the stencil mask 10 is transferred to the resist film formed on the upper surface of the wafer 11. At this time, contamination adheres to the stencil mask 10.

Next, the control unit 16, exposure of the wafer 11 made in step ST23 it is determined whether reaches a preset exposure number N _B (ST24).
When it does not reach the set exposure number N _B, step ST23 and step ST24 are repeated until the setting process number by the control unit 16, exposure is performed. At this time, every time exposure is performed, contamination adheres to the mask and the amount of contamination accumulation increases. As a result, the aperture ratio of the opening 52 constituting the monitor pattern decreases.
If reaching the set exposure processing sheets N _B, performing the following steps.

Next, the second current value I ₂ of the electron beam EB irradiated through the monitor pattern forming region 50 formed on the mask 10 is measured (ST25).

Similar to the first current value I ₁ of the control unit 16, by irradiating an electron beam to a wafer 11 of the number N _B, which is set in advance in the monitoring pattern formation region 50 of the mask 10 after the exposure, The second current value I ₂ is measured via the current detector 15.
At this time, the beam center of the electron beam EB and the center of the monitor pattern formation region 50 are substantially matched, as in the case where the first current value I ₁ is measured. For example, when the first current value I ₁ is measured, the storage unit 17 stores the positional relationship between the stencil mask 10 and the beam center of the electron beam EB. When measuring the second current value I ₂ , the control unit 16 sets the stencil mask 10 and the beam center of the electron beam EB based on the information stored in the storage unit 17. As a result, the first current value I ₁ and the second current value I ₂ are detected under the same conditions.

  Next, the contamination accumulation amount d is calculated using the measured first and second aperture ratios S1 and S2 (ST26). The following process of step ST26 is performed by the control unit 16.

  FIG. 9 is a graph showing the relationship between the current value I after transmission through the mask and the aperture ratio S of the aperture in the monitor pattern.

As shown in FIG. 9, the current amount I measured through the stencil mask 10 is substantially proportional to the opening ratio S of the opening in the monitor pattern. Therefore, the first aperture ratio S1 of the opening in the monitor pattern at the first time t1 and the first current amount I ₁ measured through the monitor pattern formation region 50 are used, and at the second time t2. Assuming that the second aperture ratio S2 of the opening in the monitor pattern and the second current amount I ₂ measured through the monitor pattern formation region 50 are expressed by the relationship of the following equation (1). Can do.

Here, the first time t1 indicates the state using the unused or immediately after washing the mask prior to the transfer of the pattern by exposure, the second time t2 to the wafer of the set exposure processing sheets N _B The state using the mask after exposure is shown.

  As described above, when the first aperture ratio S1 is changed to the second aperture ratio S2 due to the accumulation of contamination, the first and second aperture ratios S1 and S2 are related by the following equation (2). Can be represented.

  Here, since the line width A, the line width A-2d after deposition of contamination, and the first and second aperture ratios S1 and S2 are positive values as described above, if the equation (2) is transformed, the contamination The accumulation amount d of the nation can be expressed as the following formula (3).

  Therefore, by first measuring the line width A of the opening 52 of the monitor pattern at the first time t1, the first and second current values I1 and I2 at the first time t1 and the second time t2 are obtained. By measuring, the contamination accumulation amount d can be obtained.

  Here, the relationship between FIG. 9 and the above equation (1) holds only when the intensity of the electron beam EB of the exposure apparatus 1, that is, the beam current is stable and can be regarded as constant.

Next, the control unit 16, contamination deposited amount calculated is greater determines whether or not than a preset deposition amount d _B (ST27).

If preset deposited amount d contamination accumulated amount d calculated than _B is large, the stencil mask 10 by the control unit 16 is judged to need cleaning, the control unit 16 interrupts the exposure. On the other hand, if the contamination deposition amount d calculated is small, the exposure is continued than set deposit amount d _B (ST28).

At this time, the control unit 16 feeds back the calculated contamination deposition amount d to exposure conditions such as an electron beam amount (ST29).
Here, the relationship between the amount of contamination deposition and the exposure conditions, for example, the amount of change in the electron beam EB accompanying the increase in the amount of contamination deposition, is obtained in advance and stored in the storage unit 17. As a result, for example, since the contamination is accumulated, the opening ratio S of the opening 52 is reduced. Therefore, the control unit 16 sets the exposure amount to be large based on the information from the storage unit 17, and again Exposure is performed from step ST24.

  As described above, the relationship between the aperture ratio S and the current value I shown in Expression (1) is not limited to this. The intensity of the beam current can vary over time with use.

  FIG. 10 is a graph showing the relationship between the current value I and the aperture ratio S when the beam current varies with time.

When the value of the beam current varies with time, the slope changes as shown in FIG. 10, and the measured current value is different even when the aperture ratio S1 is the same.
Therefore, the control unit 16 determines the current value I ₁ measured through the monitor pattern formation region 50.
, I ₂ , and reference current values I ₀₁ and I ₀₂ are measured. The controller 16 uses the first and second correction values I ₁ / I ₀₁ and I ₂ / I ₀₂ as correction values in the equation (1) instead of the first and second current values I ₁ and I _2. Enter and calculate.

As the reference current values I ₀₁ and I ₀₂ , a beam current value measured without passing through the stencil mask 10, a current value measured through a stencil mask having an area similar to the monitor pattern forming area 50, etc. Is used. The first reference current value I ₀₁ is measured when the first current value I ₁ is measured, and the second reference current value I ₀₂ is measured when the _second current value I ₂ is measured. Is done.

According to the mask according to the present embodiment, the contamination deposited on the mask can be detected by providing the contamination monitor pattern in addition to the transfer pattern.
The monitor pattern is composed of a plurality of openings 52. As a result, the opening size of one opening 52 can be reduced, and the change in the aperture ratio can be detected sensitively.
Furthermore, since the monitor pattern is formed by the plurality of openings 52, the monitor pattern formation region 50 of the mask can be appropriately changed depending on the size and arrangement position of the transfer pattern formation region 40, and the region to be formed Accordingly, the size of the monitor pattern forming region 50 can be changed.

According to the mask contamination monitoring method in the present embodiment, a mask is obtained by measuring a current value using a current value measuring unit such as a current detector usually installed in an apparatus using a charged particle beam such as an electron beam. The amount of contamination accumulation can be monitored. As described above, since an existing apparatus is used, it is possible to easily monitor without adding new equipment. For example, a mask exposure apparatus, inspection apparatus, line width measuring apparatus, etc. can be used as a monitoring apparatus as it is.
If the current value is measured by the exposure apparatus as in the above embodiment, mask handling for measurement can be minimized. Furthermore, since the current value can be measured and contamination can be monitored without going through the steps of evacuation and release to the atmosphere, the possibility of foreign matter adhering can be reduced.

  According to the exposure program in the present embodiment, it is possible to monitor the contamination of the mask using an existing apparatus without easily reducing the throughput. As a result, the timing for cleaning the mask can be accurately determined.

The present invention is not limited to the above embodiment.
For example, in the mask of the present invention, the shape of the opening constituting the monitor pattern formation region is an example and can be changed. Further, the method of measuring the opening in the unused or cleaned mask is not limited to this embodiment, and can be changed as appropriate.
In addition, various modifications can be made without departing from the scope of the present invention.

FIG. 1 is a schematic block diagram showing an example of an electron beam exposure apparatus that realizes an exposure method using a mask and a mask contamination monitoring method according to an embodiment of the present invention. FIG. 2 is a schematic configuration diagram of a stencil mask according to an embodiment of the present invention. 3A is a schematic perspective view schematically showing a transfer pattern forming region formed on the stencil mask shown in FIG. 2, and FIG. 3B is a schematic cross-sectional view of the transfer pattern forming region. It is. FIG. 4 is an enlarged plan view schematically showing a monitor pattern forming region formed on the stencil mask shown in FIG. FIG. 5 is a graph showing the amount of contamination deposited due to the formation of the resist film. FIG. 6A is a plan view showing an example of an opening constituting the monitor pattern formation region, and FIG. 6B is a plan view showing a state in which contamination is attached to FIG. It is. FIG. 7A is a plan view showing another example of the opening that forms the monitor pattern formation region, and FIG. 7B shows a state in which the contamination is attached to FIG. 7A. It is a top view. FIG. 8 is a flowchart showing the steps of the mask contamination monitoring method according to the embodiment of the present invention. FIG. 9 is a graph showing the relationship between the current value and the aperture ratio. FIG. 10 is a graph showing the relationship between the current value and the aperture ratio.

Explanation of symbols

    DESCRIPTION OF SYMBOLS 1 ... Exposure apparatus, 2 ... Electron gun, 3 ... Restriction aperture, 4 ... Converging lens, 6, 7 ... Main deflector, 8, 9 ... Deflector for fine adjustment, 10 ... Stencil mask, 12 ... Wafer, 13 ... Stage , 14 ... Faraday cup, 15 ... Current detector, 16 ... Control part, 17 ... Memory part, 20 ... Reinforcing beam part, 21 ... Pattern forming film, 22 ... Hole, 23 ... Etching stopper film, 40 ... For transfer Pattern formation region, 50... Monitor pattern formation region, 52... Opening, S 1, S ′ 1... First opening, S 2, S ′ 2 ... second opening, A 1, A ′ 1, A 2, A '2 ... Line width, EB ... Electron beam

Claims (10)

A mask in which a transfer pattern transferred to an exposed film by an exposure beam is formed by an opening,
A mask having a monitor pattern formed by arranging a plurality of openings in the periphery of the transfer pattern. The mask according to claim 1, wherein the monitor pattern is formed by arranging a plurality of openings in a region larger than a beam diameter of an exposure beam. 2. The mask according to claim 1, wherein the center of the monitor pattern has a shape different from that of the opening at the periphery thereof, and the opening capable of aligning the exposure beam is formed. A mask contamination monitoring method for monitoring contamination deposited on the mask by exposure to transfer a transfer pattern formed on the mask to an exposed film,
Irradiating the mask on which the monitor pattern is formed with a charged particle beam, and measuring a first current value of the charged particle beam that has passed through the monitor pattern;
Irradiating the mask with a charged particle beam after performing the exposure, and measuring a second current value of the charged particle beam that has passed through the monitor pattern;
A mask contamination monitoring method comprising: calculating a deposition amount of the mask using the line width of the pattern obtained in advance and the first current value and the second current value. 5. The current value is measured by disposing a region having a high electron density of the charged particle beam at a predetermined position of the monitoring pattern of the mask in the first and second current value measuring steps. Mask contamination monitoring method. In the first and second current value measurement steps, the charged particle beam is irradiated to the mask while scanning the charged particle beam so that an irradiation amount of the charged particle beam is uniform to the monitor pattern. The mask contamination monitoring method according to claim 4, wherein the value is measured. In each of the first and second current value measuring steps, a reference current value is measured,
The mask contamination monitoring method according to claim 4, wherein in the contamination accumulation amount calculation step, a correction value is obtained from the first and second current values and the reference current value to obtain the contamination accumulation amount. In the first and second current value measuring steps, the reference current value is a current value measured without passing through the mask, and one opening formed in a size corresponding to the monitor pattern The mask contamination monitoring method according to claim 7, wherein the current value is one of current values measured through a mask having a portion. A program for estimating the cleaning time of a mask on which contamination accumulates when transferring a pattern to an exposed film,
Calculating a first aperture ratio and a second aperture ratio from a first current value and a second current value of the charged particle beam measured through a predetermined pattern of the mask;
Calculating the amount of contamination accumulated in the monitor pattern based on the line width of the monitor pattern inputted in advance and the first aperture ratio and the second aperture ratio;
Determining whether or not to perform cleaning of the mask based on the calculated amount of contamination. An exposure method for transferring a transfer pattern formed on a mask to an exposed film,
Irradiating the mask on which the monitor pattern is formed with a charged particle beam, and measuring a first current value of the charged particle beam that has passed through the monitor pattern;
Irradiating the charged particle beam through the mask and transferring the transfer pattern onto the exposed film;
Irradiating the mask with a charged particle beam and measuring a second current value of the charged particle beam that has passed through the monitoring pattern; and
Calculating a contamination deposition amount of the mask using a line width of the monitor pattern obtained in advance, the first current value, and the second current value;
A step of setting exposure conditions according to the amount of contamination deposition;
And a step of transferring the transfer pattern to the film to be exposed based on the set exposure conditions.

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