JP2000315649A - Method for transfer-exposing of charged particle beam and charged particle beam transfer-exposure system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for realizing accurate transfer regardless of the presence of slight beam drift. SOLUTION: In this transfer exposure method, mark patterns 87 and 88 for forming a mark detection beam are made on a mask in a deflection band 82 of an end part in the lengthwise direction of respective stripes, and marks 98 and 97 to be irradiated which are irradiated through scanning by a detection beam are made on a wafer. Then, prior to transfer, the marks to be irradiated are scanned several times by the detection beam so as to detect the position of the marks several times, and the quantity of drift of the beam is thereby obtained, and the position of beam at the time of transfer is corrected by just the quantity of drift.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of transferring a pattern on a mask to a sensitive substrate (a wafer or the like) using a charged particle beam such as an electron beam or an ion beam. More specifically, the present invention relates to a charged particle beam transfer method capable of transferring a large pattern exceeding the visual field of an optical system by using both mechanical scanning of a mask stage and a wafer stage and electric deflection of a charged particle beam. In particular, fine lines with a minimum line width of less than 0.1 μm
The present invention relates to a charged particle beam transfer exposure method and a charged particle beam transfer exposure apparatus, which are intended to form a high-density and high-precision pattern at a high throughput, and have been improved so that beam drift can be accurately corrected.

[0002]

2. Description of the Related Art In an apparatus such as an electron beam lithography apparatus, which needs to precisely control an image forming position of an electron beam, when a beam drift of a certain degree or more occurs,
Usually, reassembly is performed after disassembling the electron beam optical column and cleaning the inside of the column. Most of the cause of the beam drift is due to the fact that the dirt on the inside of the lens barrel is charged and the trajectory of the electron beam is disrupted. Note that beam drift is a phenomenon in which the imaging position of an electron beam shifts from time to time in spite of the same conditions under which the optical system can be controlled (lens excitation current, deflection current / voltage, etc.). is there. In recent years, insi
Attempts to perform tu cleaning have also been reported. Note that beam drift may occur due to temperature fluctuations of the optical components inside the lens barrel.

[0003]

In the conventional variable-shaping type electron beam lithography apparatus, the beam current was as small as 1 μA or less. The apparatus irradiates the resist with a beam current of 20 times or more, that is, 20 to 25 μA. For this reason, a lot of decomposition products of the resist are generated,
The inside of the lens barrel gets dirty quickly. Further, in order to achieve higher-precision transfer, requirements for beam stability are becoming stricter. Therefore, in the conventional method of "cleaning when the lens barrel becomes dirty and beam drift occurs", the cleaning interval becomes too short. Even if the lens barrel is not stained, the beam may drift due to the temperature fluctuation of the optical components inside the lens barrel.

[0004] The present invention has been made in view of the above problems, and has as its object to provide a method and the like for realizing high-accuracy transfer even if there is some beam drift.

[0005]

Means for Solving the Problems and Embodiments of the Invention In order to solve the above-mentioned problems, a charged particle beam transfer exposure method of the present invention uses an entire transfer area to reduce a dimension within a deflectable visual field of a charged particle beam optical system. It is divided into a plurality of stripes having short sides, and each of the stripes is further divided into a plurality of band-shaped regions (deflection bands) extending in the short side direction of the stripe, and a charged particle beam is deflected and scanned in the short side direction of the stripe. A charged particle beam transfer exposure method for mechanically scanning the mask and the sensitive substrate in the long side direction of the stripe to transfer the entire transfer area, wherein the deflection band at the longitudinal end of each stripe is masked. A mark pattern for forming a mark detection beam is provided on the upper side, and an illuminated mark which is scanned and irradiated by the detection beam is provided on the sensitive substrate. Detecting the mark position a plurality of times, detecting the beam drift amount by detecting the marks a plurality of times, calculating the correction amount of the beam position at the time of transfer based on the drift amount, and correcting the beam position. It is characterized by.

When the beam is constantly flowing under the same conditions, the amount by which the beam drifts irregularly is generally not very large. However, when the beam conditions are changed, for example, immediately after starting to emit the beam after blanking for a long time, when the beam current is suddenly greatly reduced due to a large current, or immediately after the beam is largely deflected For example,
Large beam drift occurs. These drifts seem irregular at first glance, but in practice, the same changes in beam conditions can provide considerable reproducibility. By the way, in a charged particle beam transfer apparatus that performs exposure using a mask of the same specification,
Except for the point that the beam current constantly changes depending on the pattern, the operation is almost the same in terms of beam blanking and deflection timing. Therefore,
By correcting the reproducible component of the beam drift, high-accuracy transfer can be performed even with a slight beam drift.

In the present invention, a test mask having the mark pattern in a plurality of deflection bands and a test-sensitive substrate having the irradiation mark in a plurality of deflection bands are used to determine the beam drift amount in each deflection band in advance. The ratio or difference is measured and tabulated, and transfer can be performed while correcting drift based on the table.

It is also possible to provide a mark pattern or a mark to be irradiated on a part of a transfer mask or a wafer having a general device pattern, and measure a beam drift in an actual transfer process. However, as described above, it is better to measure the beam drift about once a week, for example, using a dedicated mask and wafer for a test, and tabulate the results to correct the pattern area on the mask for actual device manufacturing. This is preferable because more can be used.

In the present invention, it is preferable that the pattern density in the deflection band where the mark pattern or the mark to be irradiated is formed is substantially the same as the average pattern density of the device pattern to be transferred. When the beam current is large, the drift amount is large, and when the beam current is small, the drift amount is small. Therefore, high-precision correction can be performed by measuring the beam drift amount under substantially the same conditions as in the actual device pattern transfer and performing drift correction based on the data. The drift amount can be measured by changing the beam current in several stages, and the drift correction amount can be calculated according to the current. At this time, since the beam current and the drift amount are not always proportional, the drift amount of the intermediate portion of the beam current can be obtained by interpolation calculation.

A charged particle beam transfer exposure apparatus according to the present invention comprises: an illumination optical system for illuminating a mask on which a pattern to be transferred on a sensitive substrate is formed with a charged particle beam; a movable stage for mounting the mask; , A projection optical system for projecting and imaging the charged particle beam passing through the mask at an appropriate position on the sensitive substrate, and a movable stage for mounting the sensitive substrate, and the entire transfer area can be deflected by the optical system The field of view is divided into a plurality of stripes each having a short side, and each stripe is further divided into a plurality of band-shaped regions (deflection bands) extending in the short side direction of the same stripe. A charged particle beam transfer exposure apparatus that deflects and scans a line, and mechanically scans a mask and a sensitive substrate mainly in a long side direction of a stripe to transfer an entire transfer area. deflection A mark pattern for forming a mark detection beam is provided on a mask, an illuminated mark that is scanned and illuminated by the detection beam is provided on a sensitive substrate, and the illuminated mark is detected by the detection beam before transfer. Detects the position of the scanning focus mark multiple times, detects the beam drift amount by detecting these multiple marks, calculates the beam drift amount that corrects the beam position at the time of transfer based on the drift amount, and calculates only that amount It is characterized by having a correction section for correcting the beam position.

A description will be given below with reference to the drawings. FIG.
FIG. 1 is a diagram showing an outline of an imaging relationship and a control system in an entire optical system of an electron beam projection exposure apparatus according to one embodiment of the present invention. The electron gun 1 arranged at the uppermost stream of the optical system emits an electron beam downward. Below the electron gun 1, two stages of condenser lenses 2 and 3 are provided.
The crossover CO is imaged on the blanking aperture 7 through these condenser lenses 2 and 3.

A rectangular opening 4 is provided below the condenser lens 3.
Is provided. The rectangular aperture (illumination beam shaping aperture) 4 allows only an illumination beam that illuminates one subfield (unit exposure pattern area) of the mask (reticle) 10 to pass. Specifically, the opening 4 forms the illumination beam into a square having a dimension of slightly more than 1 mm square in mask size conversion. The image of the opening 4 is formed on the mask 10 by the lens 9.

Below the beam shaping aperture 4, a blanking deflector 5 is arranged. The deflector 5 deflects the illumination beam to hit the non-opening of the blanking opening 7,
The beam does not hit the mask 10. An illumination beam deflector 8 is arranged below the blanking opening 7. This deflector 8 mainly scans the illumination beam sequentially in the horizontal direction (X direction) in FIG. 4 to illuminate each subfield of the mask 10 within the field of view of the illumination optical system. A condenser lens 9 is disposed below the deflector 8.
The condenser lens 9 converts the electron beam into a parallel beam, impinges the beam on the mask 10, and forms an image of the beam forming aperture 4 on the mask 10.

Although only one subfield on the optical axis is shown in FIG. 4, the mask 10 actually extends in the plane perpendicular to the optical axis (XY plane) (described later with reference to FIG. 5). And has a number of subfields. On the mask 10, a pattern (chip pattern) forming one semiconductor device chip as a whole is formed.

To illuminate each subfield within the field of view of the illumination optical system, the electron beam can be deflected by the deflector 8 as described above. In order to illuminate each subfield beyond the field of view of the illumination optical system, the mask 10 is moved mechanically. That is, the mask 10 is placed on a mask stage 11 that can move in the XY directions.

Below the mask 10, projection lenses 12 and 14 and a deflector 13 are provided. Then, an illumination beam is applied to a certain subfield of the mask 10,
The electron beam that has passed through the pattern portion of the mask 10 is reduced by the projection lenses 12 and 14 and deflected by the lenses and the deflector 13 to form an image at a predetermined position on the wafer 15. An appropriate resist is applied on the wafer 15. The resist is given a dose of an electron beam, and the pattern on the mask is reduced and transferred onto the wafer 15.

A crossover CO is formed at a point which internally divides the space between the mask 10 and the wafer 15 at a reduction ratio, and a contrast opening 18 is provided at the crossover position. The opening 18 blocks the electron beam scattered by the non-pattern portion of the mask 10 from reaching the wafer 15. A backscattered electron detector 19 is arranged between the second projection lens 14 and the wafer 15. The backscattered electron detector 19 detects an electron beam that strikes and reflects on the wafer 15. The signal detected by the backscattered electron detector 19 is sent to the control unit 21 via a conversion circuit 19a including an A / D converter and the like. By processing this signal, the position of the mark on the wafer 15 can be known, and basic information on the alignment between the wafer and the optical system or the mask and beam drift can be obtained.

The wafer 15 is placed on a wafer stage 17 that can move in the X and Y directions via an electrostatic chuck 16. By synchronously scanning the mask stage 11 and the wafer stage 17 in directions opposite to each other,
A wide area in the device pattern can be sequentially exposed. Note that both stages 11 and 17 are equipped with an accurate position measurement system using a laser interferometer, and the position of the stage is accurately controlled.

Each of the lenses 2, 3, 9, 12, 14 and each of the deflectors 5, 8, 13 are provided with a respective coil power supply 2a, 3a.
a, 9a, 12a, 14a and 5a, 8a, 13a. The mask stage 11 and the wafer stage 17 are also controlled by the control unit 21 via the stage drive motor control units 11a and 17a. The electrostatic chuck 16 is connected to the main controller 21 via the electrostatic chuck controller 16a.
Is controlled by The beam drift correction unit 21a in the control unit 21 has a table of the amount of beam drift measured by a method described later, and supplies a corresponding beam position correction signal to the deflector power supply 13a to correct the drift of the beam position. By accurate control of the stage position and the optical system, the reduced images of the subfields on the mask 10 are accurately joined on the wafer 15, and the entire chip pattern on the mask is transferred onto the wafer.

Next, a detailed example of a mask used for the electron beam projection exposure of the division transfer system will be described with reference to FIG. FIG. 5 is a diagram schematically illustrating a configuration example of a mask for electron beam exposure. (A) is an overall plan view, (B) is a partial perspective view, and (C) is a plan view of one small membrane region.

In FIG. 5, an area indicated by a large number of squares 41 is a small membrane area (thickness of 0.1 μm to several μm) including a pattern area corresponding to one subfield.
It is. As shown in FIG. 5C, a small membrane area 41 is a pattern area (subfield) 42 at the center.
And a skirt 43 which is a frame-shaped non-pattern area around the skirt 43. The subfield 42 is a portion where a pattern to be transferred is formed. The skirt 43 is a portion where no pattern is formed, and corresponds to an edge portion of the illumination beam.

One sub-field 42 has a size of about 0.5 to 5 mm square on a mask as it is currently being studied. The size of the area (image field) of the projected image in which this subfield is reduced and projected on the wafer is 0.1 to 1 mm square as the reduction rate is 1/5. A portion 45 called a grid-like grid in the vicinity of the small membrane region 41 is a beam having a thickness of about 0.5 to 1 mm to maintain the mechanical strength of the membrane. The width of the grenage 45 is about 0.1 mm.

A large number of small membrane regions 41 are arranged side by side in the X direction to form one group (deflection band 44), and a large number of such deflection bands 44 are arranged in the Y direction to form one stripe 49. ing. The width of the stripe 49 corresponds to the width of the deflectable visual field of the electron beam optical system. A plurality of stripes 49 exist in parallel in the X direction. Thick beams, shown as struts 47 between adjacent stripes 49, are to keep the overall mask deflection small. The strut 47 is integral with the grenage and has a thickness of about 0.5 to 1 mm and a width of several mm. In addition, a method in which a non-pattern area such as a skirt 43 or a grenage 45 is not provided between adjacent subfields 42 in one deflection band 44 is also being studied.

According to the system currently considered to be influential,
At the time of projection exposure, a row (deflection zone 44) of subfields in one stripe 49 in the X direction is sequentially exposed by electron beam deflection. On the other hand, the row in the Y direction in the stripe 49 is
Exposure is performed sequentially by continuous stage scanning. When proceeding to the next stripe 49, the stage is intermittently sent.

At the time of projection exposure, non-pattern areas such as skirts and grids are canceled on the wafer, and the patterns of the respective subfields are joined together over the entire chip. A transfer reduction ratio of 1/4 or 1/5 has been considered, and the size of one chip on a wafer is 4
Since the size of the GDRAM is assumed to be 27 mm × 44 mm, the entire size of the mask including the non-pattern portion of the chip pattern is about 120 to 230 mm × 150 to 350 mm.

FIG. 2 is a plan view schematically showing the arrangement of mark patterns on a test mask in the electron beam transfer exposure method according to one embodiment of the present invention. FIG. 3 is a plan view schematically showing the arrangement of irradiated marks on a test wafer used in combination with the test mask of FIG.

FIG. 2 shows three stripes 71, 72, 73 arranged in the X direction. Stripes 71, 7
A strut (thick reinforcing portion) 74 exists between 2 and 73. Each of the stripes 71, 72, and 73 is a deflection band 8 that is a row in the X direction of a number of subfields described with reference to FIG.
1, 82, 83, etc. The illustration of the non-pattern area between the deflection bands is omitted. In this example, mark patterns 87, 88 for measuring beam drift are provided at the ends of the stripes 71, 72, 73 in the Y direction.
(Linear patterns arranged in the X direction or the Y direction), deflection bands 81-1 to 85-1, 82-1 to 5 and 83-1 to 4-4 are arranged. It should be noted that deflection bands having such a mark pattern are provided in about 10 steps at the end of the stripe of the test mask.

Marks 87 and 88 for measuring beam drift
Is, as described above, several linear marks arranged. Mark 87 for measuring beam drift in the X direction
In the figure, linear marks extending in the Y direction are arranged in the X direction. In the beam drift measurement mark 88 in the Y direction, linear marks extending in the X direction are arranged in the Y direction. Note that these linear marks (line portions) 87 and 88 are portions (holes or low-scattering membrane portions) where the electron beam relatively easily passes on the mask. The irradiation mark on the wafer (the portion indicated by reference numerals 97 and 98 in FIG. 3) is a metal layer or the like that easily reflects an electron beam.

The central stripe 72 shown in FIG.
Has only the mark pattern 87 in the X direction. On the other hand, the deflection band 83 of the right stripe 73 is Y
It has only the direction mark pattern 88. The deflection band 81 of the left stripe 71 is a mark pattern 87 in the X direction.
Alternatively, subfields having mark patterns 88 in the Y direction are alternately arranged. This mark pattern 8
The combination of 7, 88 can be appropriately selected.

The test wafer shown in FIG. 3 has a large number of irradiation marks 97 to 97 similarly to the test mask of FIG.
A deflection band having 98 is formed. However, there is no portion corresponding to the strut between the stripes 91, 92 and 93, and the stripes 91, 92 and 93 are continuously connected. Although not shown in the drawing, non-pattern areas between the subfields and deflection bands existing on the mask are also packed on the wafer, and the patterns on the subfields are joined together to form one whole. A device pattern is formed.

In this example, the width and length of the mask hole are determined so that the beam current becomes 1 μA in the subfield in which only the linear mark is formed. When the beam current is increased, a large hole 96 is formed in a portion where the mark 97 does not exist, as shown in a sub-field 95 enlarged in FIG.
Open 98. For example, 5 μA, 10 μA, 15 μA,
The beam drift is measured with a beam current of 20 μA, 25 μA, or the like, and the relationship between the drift and the beam current can be grasped. In this case, the current of the illumination beam incident on one subfield on the mask is 100 μA.

FIG. 1 is a graph showing an example of a method of determining a measurement result of a beam drift and a correction amount. In this case, the beam current is 10 μA. The vertical axis indicates the beam position drift amount (unit: nm) in the X direction, and the horizontal axis indicates the deflection width (unit: mm) in the X direction. In the figure, the mark (open circle) indicates the mark position by scanning the deflection band (82-1 in FIG. 2 and 102-1 in FIG. 3) in the first column from the end in the Y direction of the stripe. Is the result of measuring the amount of beam drift by detecting. The black circles ● also indicate the drift amount of the deflection band in the second column, the triangle △ indicates the drift in the third column, the cross × indicates the fourth column, the square □ indicates the fifth column, and the double circle ◎ indicates the drift in the sixth column. Quantity. Note that timings such as a scanning speed and blanking are the same as those at the time of actual device pattern scanning.

In this example, since the measurement sequence is performed from the minus direction to the plus direction, the drift amount is large in the minus X direction deflection and small in the plus X direction deflection. Also, the drift amount is large in the deflection band of the first row, and becomes smaller as it goes to the second and third rows.
In the fifth and sixth columns, the values converge to almost constant relatively small values. Although illustration is omitted, the drift amounts in the sixth and subsequent columns are almost the same as those in the sixth column. The reason why the drift amount is large in the deflection band in the first column of the stripe is that the blanking of the beam has been canceled for a relatively long time while waiting for a stripe change or the like.

The example shown in FIG. 1 is a case where the reproducibility is relatively good. If there is a beam drift with poor reproducibility, 1
Points that do not ride on the curve of the book appear to be disjointed, and data that has poor convergence at any column. If such a tendency becomes remarkable, drift correction cannot be performed, so maintenance such as cleaning the inside of the optical barrel of the transfer device is performed.

A method for correcting the drift amount based on the measurement result shown in FIG. 1 will be described. At the time of transfer of a normal device pattern, a beam position detection mark is provided in the deflection band in the first column at the Y direction end of the stripe, and the stripe is exposed while performing correction based on the mark detection data. That is, if the beam drift amount correction is not performed, the correction of all the deflection bands of the stripe is determined based on the measurement data of the deflection bands in the first row.

In this embodiment, since the amount of drift between the deflection band in the first column and the deflection band in the other column is known by a prior test, the drift amount in each column is set to the X-direction deflection width. Make the table corresponded. For example, the deflection width of the second row−
In the case of 2.25 mm, the value (4 nm) indicated by C1 in the figure is the drift amount. When the deflection width of the third row is −0.5 mm, the value (3 nm) indicated by C2 in the drawing is the drift amount. These values are recorded as a table in the beam drift correction unit (reference numeral 21a in FIG. 4) of the control unit (computer) of the transfer apparatus.

At the time of actual device pattern transfer exposure, the drift amount corresponding to each deflection width of each stripe is corrected to the data at the mark position measured in the deflection band of the first column of the stripe, and the deviation amount of each deflection band is corrected. Correct the subfield transfer position. In the above example, the table is created with the difference value, but may be created with the ratio. In the case of a ratio, for example, 2
When the deflection width of the column is -2.25 mm, the value of the ratio of the beam position drift is 10/14 = 0.71.

For example, six types of such tables are prepared for each beam current. Then, the correction drift amount is calculated in accordance with the average beam current in that layer of the actual device pattern. At this time, the correction amount for the intermediate beam current is determined by interpolation calculation. That is, based on the measured drift amount, the beam position correction amount is calculated in consideration of the beam current and the like, and the beam position is corrected by the calculated amount.

For the correction in the Y direction, the same measurement is performed to make a table, and the correction is performed together with the X. The drift in the Y direction is usually smaller than that in X.

When the measurement shown in FIG. 1 is performed periodically, the drift amount does not converge to a constant value in 5 to 6 times, or the drift amount does not approach a constant value even at the end of the deflection region, and data varies by 2 nm or more. Is reached, it is determined that a component having no reproducibility has come out, and cleaning is performed.

[0041]

As is apparent from the above description, according to the present invention, it is possible to provide a method and the like for realizing high-accuracy transfer even with a slight beam drift.

[Brief description of the drawings]

FIG. 1 is a graph showing an example of a method for determining a beam drift measurement result and a correction amount according to the present invention. The vertical axis shows the beam position drift amount (unit: nm) in the X direction, and the horizontal axis shows X
The deflection width in the direction (unit: mm) is shown.

FIG. 2 is a plan view schematically showing the arrangement of mark patterns on a test mask in the electron beam transfer exposure method according to one embodiment of the present invention.

FIG. 3 is a plan view schematically showing the arrangement of irradiation target marks on a test wafer used in combination with the test mask of FIG. 2;

FIG. 4 is a diagram showing an outline of an image forming relationship and a control system in the entire optical system of the split-transfer type electron beam projection exposure apparatus of the present invention.

FIG. 5 is a view schematically showing a configuration example of a mask for electron beam exposure. (A) is an overall plan view, (B) is a partial perspective view, and (C) is a plan view of one small membrane region.

[Explanation of symbols]

Reference Signs List 1 electron gun 2, 3 condenser lens 4 illumination beam shaping aperture 5 blanking deflector 7 blanking aperture 8 deflector 9 illumination lens 10 mask 11 mask stage 12 projection lens 13 deflector 14 projection lens 15 wafer 16 electrostatic chuck 17 wafer Stage 19 reflected electron beam detector 1
8 Contrast Aperture 41 Membrane Area 42 Subfield 43 Skirt 44 Deflection Band 45 Grid Stripe 47 Strut 49 Mask Stripe 71, 72, 73 Stripe on Mask 81, 82, 83 Deflection Band on Mask 87 X-direction Position Detection Mark Pattern 88 Y Direction position detection mark pattern 91, 92, 93 Stripe on wafer 97 X-direction irradiated mark 98 Y-direction irradiated mark 102 Deflection band on wafer

Claims (8)

[Claims] 1. An entire transfer region is divided into a plurality of stripes each having a shorter side in a deflectable field of view of a charged particle beam optical system, and a plurality of band-like regions extending in each stripe in a short side direction of the same stripe. (Deflection band), the charged particle beam is deflected and scanned in the short side direction of the stripe, and the mask and the sensitive substrate are mechanically scanned in the long side direction of the stripe to transfer the entire transfer area. In a particle beam transfer exposure method, a mark pattern for forming a mark detection beam is provided on a mask for a deflection band at a longitudinal end of each stripe, and a sensitive substrate is scanned and irradiated with the detection beam by the detection beam. Before the transfer, the irradiation mark is scanned with the detection beam to detect the mark position a plurality of times, and the amount of beam drift is detected by detecting the mark a plurality of times before transfer. A charged particle beam transfer exposure method, wherein a correction amount of a beam position at the time of transfer is calculated based on the drift amount of the beam and the beam position is corrected. 2. The mark pattern and the mark to be irradiated are provided on a plurality of deflection bands at the longitudinal end of the stripe, and the plurality of deflection bands are scanned at the same timing as the scanning at the time of transfer to detect a mark. The beam drift amount for each deflection band is detected by detecting the marks in the plurality of deflection bands, and the beam position correction amount for each deflection band during transfer is calculated based on the drift amount to correct the beam position. The charged particle beam transfer exposure method according to claim 1, wherein 3. Using a test mask having the mark pattern in a plurality of deflection bands and a test-sensitive substrate having the irradiation mark in a plurality of deflection bands, a ratio or a difference of a beam drift amount in each deflection band in advance. 3. The charged particle beam transfer exposure method according to claim 1, wherein the transfer is performed while measuring the drift and correcting the drift based on the measured values. 4. The device according to claim 1, wherein a pattern density in the deflection band where the mark pattern or the mark to be irradiated is formed is substantially the same as an average pattern density of a device pattern to be transferred. 4. The charged particle beam transfer exposure method according to 3. 5. The charged particle beam transfer exposure method according to claim 1, wherein when the drift amount exceeds a predetermined value, maintenance such as cleaning of an optical system component is performed. 6. A beam drift generated after changing a beam condition is separated into a reproducible portion and a non-reproducible portion, and the reproducible portion is corrected based on a previously measured drift amount. 2. The charged particle beam transfer exposure method according to claim 1, wherein maintenance is performed when a portion having no reproducibility exceeds a certain value. 7. An illumination optical system for illuminating a mask having a pattern to be transferred on a sensitive substrate with a charged particle beam, a movable stage for mounting the mask, and a charged particle beam passing through the mask. A projection optical system that projects and forms an image on an appropriate position on the sensitive substrate, and a movable stage on which the sensitive substrate is mounted. The dimension of the entire transfer area within the deflectable visual field of the optical system is set to a short side. The stripe is divided into a plurality of stripes, and each stripe is further divided into a plurality of band-shaped regions (deflection bands) extending in the short side direction of the stripe. This is a charged particle beam transfer exposure apparatus that mainly mechanically scans the mask and the sensitive substrate in the side direction to transfer the entire transfer area. The deflection band at the longitudinal end of each stripe is marked on the mask. A mark pattern for forming an outgoing beam is provided, and a mark to be irradiated is provided on the sensitive substrate by scanning with the detection beam. Prior to the transfer, the mark to be irradiated is scanned with the detection beam to determine the position of the mark. It has a beam drift correction unit that detects a plurality of times, detects a beam drift amount by detecting the marks a plurality of times, calculates a correction amount of a beam position at the time of transfer based on the drift amount, and corrects a beam position. A charged particle beam transfer exposure apparatus characterized by the above-mentioned. 8. The apparatus according to claim 1, wherein the beam drift correction unit has a table of the ratio or difference of the beam drift amount in each deflection band in advance, and performs the transfer while correcting the drift based on the table. Item 7. A charged particle beam transfer exposure apparatus according to Item 7.