JPH1154413A - Method and device for transfer and exposure and mask for pattern transfer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for transfer and exposure by which difficulties and degradation of the accuracy of transfer associated with the formation of a large mask can be resolved. SOLUTION: In a method for transfer and exposure, a mask 51 covering a pattern region corresponding to one exposure unit is formed by dividing it into multiple mask substrates 55-1 to 55-4. The mask substrates 55-1 to 55-4 are placed in a device in a device for transfer and exposure. Coordinates of each of the multiple mask substrates 55-1 to 55-4 are measured. Baged on the measured coordinates of individual mask substrate, position of exposure is corrected, the mask pattern is transferred, and exposed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a transfer exposure method, a transfer exposure apparatus, and a pattern transfer mask used for lithography in a process of manufacturing a semiconductor device or a liquid crystal device. In particular, the present invention relates to a transfer exposure method using a charged particle beam (such as an electron beam), which often involves difficulty in manufacturing a large mask.

[0002]

2. Description of the Related Art The prior art will be described by taking an electron beam transfer exposure method as an example. In recent years, with the development of the partial batch transfer method, there has been a movement to reduce and transfer a mask image even in electron beam lithography. In the partial batch transfer method, a repetitive pattern portion (about 10 μm square on a wafer) in a semiconductor memory such as a DRAM is masked, the repetitive pattern portion transfers a reduced mask image, and the non-repetitive pattern portion is a variable shaped beam method. In this method, direct writing is performed, and a dramatic improvement in throughput is achieved as compared with the variable shaped beam method.

On the other hand, there is known an electron beam reduction transfer apparatus which irradiates an electron beam onto a mask provided with a circuit pattern of an entire semiconductor chip and reduces and transfers an image of a pattern in the irradiation range by a two-stage projection lens. (For example, see JP-A-5-1
No. 60012). In this type of apparatus, when the entire area of the mask is irradiated with an electron beam at a time, the pattern cannot be transferred with high accuracy. Therefore, the field of view of the optical system is divided into a number of small areas (main field and subfield). The pattern image is transferred while changing the condition of the electron optical system for each sub-field of view (division transfer method, for example, see US Pat. No. 5,260,151).
In such a division transfer method, direct writing of a non-repeated pattern portion, which is a cause of a decrease in throughput, can be eliminated by masking the entire chip and performing reduced projection exposure. However, in this case, the reduction ratio (1/50 to 1/20) as in the partial batch transfer method results in a very large mask, so that the reduction ratio should be about 1/10 to 1/2. is necessary.

[0004]

The mask used for the electron beam reduction transfer exposure as described above has a diameter of 1 micron to 30 micrometers for reasons of electron beam scattering characteristics and mask fabrication.
In many cases, a free-standing thin film of silicon or the like having a thickness of about a micrometer is finely processed. In particular, when manufacturing a mask for the entire exposure region (a pattern of one chip or a plurality of chips), which is one exposure unit, there is a problem that the area of the mask becomes very large, making the manufacturing difficult. For example, when the reduction ratio is 1/8, the area of the mask is 64 times the area of the exposure region, and in the case of a 15 × 30 mm chip, the size of the mask is 120 × 240 mm. When manufacturing a mask of this size from a silicon wafer, it is necessary to use a 300 mm wafer process which is said to start mass production around 2000. With the current technology, it is difficult to form a fine self-supporting thin film pattern over the entire area of 120 × 240 mm.
Even if a mask can be manufactured, it is extremely difficult to guarantee pattern dimensional accuracy and positional accuracy over the entire mask region.

[0005] As means for solving such problems,
Instead of forming a large-area mask on a single substrate, a method of dividing and manufacturing the mask on a plurality of substrates is conceivable.
However, even in this case, there is a problem that even if a plurality of substrates are fixed to one frame and integrated, the installation position accuracy of each mask is deteriorated. Even if the position error of the substrate is measured when the substrate is fixed to the frame, and this position error is corrected in the subsequent exposure process, the position fluctuation factors during the use of the mask over time remain, so it is not sufficient in accuracy. I can not say.

Furthermore, when a self-supported thin film of silicon or the like is finely processed for use as a mask, a mask formed by patterning a thin film of chromium or the like on a substrate of quartz or the like used in optical lithography is used. The problem of positional distortion becomes serious. Further, in the case where the mask substrate is divided into a plurality of substrates due to the problem of the size of the mask substrate, an error caused by division of the mask becomes a problem.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a transfer exposure method and the like that can eliminate the difficulty and deterioration of transfer accuracy associated with the manufacture of a large mask.

[0008]

In order to solve the above-mentioned problems, a transfer exposure method according to one aspect of the present invention is to apply an energy beam to a pattern formed on a mask, and to form a pattern through the mask. A transfer exposure method for image-forming and transferring the energy beam formed on the sensitive substrate; a mask covering a pattern area for one exposure unit is divided into a plurality of mask substrates, and the plurality of mask substrates are produced. Are arranged side by side in a transfer exposure apparatus, the coordinates of the substrate are individually measured for each of the plurality of mask substrates, and the exposure position is corrected based on the measured individual mask substrate coordinates. It is characterized in that transfer exposure of a pattern on a mask substrate is performed. Here, the energy rays include visible light, ultraviolet light, electron beam, ion beam, and X-ray.

According to another aspect of the present invention, there is provided a transfer exposure apparatus, wherein an energy beam is applied to a pattern formed on a mask, and the patterned energy beam passing through the mask is image-transferred onto a sensitive substrate. A transfer exposure apparatus,
A means for dividing the mask into a plurality of mask substrates and juxtaposing them in the transfer exposure apparatus, and for each of the plurality of mask substrates, individually measuring coordinates of each of the mask substrates; Means for performing exposure position correction and transfer exposure based on the measured individual mask substrate coordinates.

Further, the mask of the present invention is a mask on which a transfer pattern is formed; the mask comprises a plurality of divided mask substrates arranged side by side, and each mask substrate is positioned on a mask stage in an exposure apparatus. A plurality of alignment marks capable of measurement are provided.

That is, in the present invention, two or more position measurement marks are formed on each of a plurality of divided mask substrates, and the mask substrates are arranged side by side in an exposure apparatus, and then each of the marks is individually arranged. Then, the exposure position is corrected and the transfer exposure is performed based on the position measurement result.
As described above, since the position of the mask is measured for each substrate in the exposure apparatus, high-accuracy transfer exposure can be performed.

On the other hand, in a transfer exposure apparatus according to another aspect of the present invention, an energy beam is applied to a pattern formed on a mask, and the energy beam patterned by passing through the mask is image-transferred onto a sensitive substrate. A transfer exposure apparatus, wherein the mask is provided with a plurality of position measurement marks that are not on the same straight line, and means for measuring the position of each mark on a mask stage in the exposure apparatus; And a means for obtaining a correction function for correcting a position error of the pattern arrangement on the mask in response to a signal from the mask, and a means for correcting the exposure position based on the correction function.

That is, a plurality of position measurement marks are provided on a mask substrate, and functions representing the mask position, rotation, expansion and contraction, orthogonality, etc. are derived from the measurement results of these position measurement marks. Exposure is performed by correcting the transfer exposure position based on the correction function. When the substrate is divided into a plurality of substrates, a correction function is obtained for each substrate. Further, when the inside of the substrate is divided into a plurality of regions, a correction function may be obtained for each region. Since exposure is performed using a correction function for correcting an error in the pattern arrangement on the mask substrate, the arrangement accuracy of the pattern transferred on the wafer is improved.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. First, an outline of an electron beam exposure apparatus to which the present invention is applied will be described with reference to FIG. FIG. 2 is a diagram showing an image forming relationship in the entire optical system of the electron beam exposure apparatus of the division transfer system. The electron gun 1 emits an electron beam downward. Below the electron gun 1, two condenser lenses 3, 5
The electron beam passes through the condenser lenses 3 and 5 and forms an image of a crossover on the blanking aperture 7. These two condenser lenses 3 and 5 function as a zoom lens, and the current density for irradiating the reticle 10 can be varied.

Above and below the condenser lenses 3, 5, two-stage rectangular openings 2, 6 are provided. The rectangular apertures (sub-field limiting apertures) 2 and 6 pass only the electron beam illumination light for the area corresponding to one sub-field. Specifically, the first
The aperture 2 of this shape shapes the illumination light into a square having a dimension of slightly more than 1 mm square in mask size conversion. The image of the opening 2 is formed on the second opening 6 by the lenses 3 and 5.

Below the second opening 6, a sub-field selection deflector 8 is arranged at the position where the crossover is formed, in parallel with the blanking opening 7. The sub-field selection deflector sequentially scans the illumination light in the X direction in FIG.
Exposure of all sub-fields within one main field is performed. A condenser lens 9 is arranged below the sub-field selection deflector 8. The condenser lens 9 converts the electron beam into a parallel beam, impinges on the mask 10, and forms an image of the second opening 6 on the mask 10.

Although only one sub-field of view on the optical axis of the mask 10 is shown in FIG.
(Y direction), and has many sub-fields and main fields. When illuminating and exposing each sub-field within one main field,
As described above, the electron beam is deflected by the sub-field selection deflector 8. The mask 10 is mounted on a mask stage 11 that can move in the XY directions. Then, a wafer stage 15 capable of moving the sample wafer 14 in the XY directions
Is placed on top. By scanning the mask stage 11 and the wafer stage 15 in directions opposite to each other in the Y direction, each main visual field in the stripe of the chip pattern is continuously exposed. Further, both stages 11 and 15 are X
Exposure of each stripe is performed by intermittent scanning in the direction. Each of the stages 11 and 15 is equipped with an accurate position measuring system using a laser interferometer, and each sub-field and main field of view on the wafer 14 is adjusted by a separate alignment means and adjustment of each deflector. Are joined together exactly.

Below the mask 10, a two-stage projection lens 1 is provided.
2 and 13 (objective lens) and a deflector (not shown) are provided. Then, one sub-field of the mask 10 is irradiated with an electron beam, and the electron beam patterned by the mask 10 is reduced and deflected by the two-stage projection lenses 12 and 13 and is connected to a predetermined position on the wafer 14. Imaged. An appropriate resist is applied to the wafer 14 (referred to as a sensitive substrate), and a dose of an electron beam is given to the resist to transfer a reduced pattern of a mask image onto the wafer 14. As described above, the wafer 14 is mounted on the wafer stage 15 that can move in the direction perpendicular to the optical axis.

FIG. 1 is a plan view showing a mask according to an embodiment of the first aspect of the present invention. This mask 51 has a DR
It covers all patterns for one AM chip,
The divided mask substrates 55-1 to 55-4 are placed in a frame 53.
It is configured side by side on top. Frame 53 is several mm thick and several hundred mm
A corner rigid member, each of the mask substrates 55-1 to 55-
Window holes 54-1 to 54-4 are opened in the portion where 4 is attached. Each of the mask substrates 55-1 to 55-4 has a thickness of 1 to 3.
It is made of a Si thin film of about 0 μm and has a width of several tens of mm square. Each of the mask substrates 55-1 to 55-4 has its peripheral part fixed around the frame holes 54-1 to 54-4.

Rough alignment marks 57-1 and 57-2 for rough alignment on the mask stage are formed on the left and right of the middle portion of the mask frame 53. Also,
Two fine alignment marks 59-11 to 59-42 for fine alignment of each mask substrate to the mask stage are provided on the left and right of the middle part of each mask substrate 55-1 to 55-4. Is formed. The number of each mark for each mask substrate may be three or more. By measuring the positions of the rough alignment marks 57-1 and 57-2, information such as the position coordinates and rotation of the frame 53 can be obtained.
By measuring the positions of 11 to 59-42, information such as position coordinates and rotation can be obtained for each of the mask substrates 55-1 to 55-4.

As these marks and their sensors, the following known types can be used. (1) LSA (Laser Step Alignment): LSA is a system that irradiates a laser beam onto an alignment mark on a mask and measures the mark position using diffracted / scattered light. (2) FIA (Field Image Alignment): FIA is a system that performs image processing and measures an alignment mark illuminated with light having a wide wavelength bandwidth using a halogen lamp as a light source. (3) LIA (Laser Interferometric Alignment): L
The IA irradiates a laser beam with a slightly changed frequency from two directions to a diffraction grating alignment mark on a mask, interferes the two generated diffracted lights, and detects the position information of the alignment mark from its phase. System. Further, a backscattered electron detector (reference numeral 1 in FIG. 2) is provided on the mask.
6), a method of scanning a mark on a mask with an electron beam and detecting reflected electrons and secondary electrons from the mark can also be adopted.

FIG. 3 is a flowchart showing an example of a sequence for transferring and exposing a semiconductor device chip pattern using the mask of FIG. First, a mask is set on a mask stage in an exposure apparatus (S101). Next, the position of the mask frame is measured using the rough alignment mark (S102). Next, the mask substrate 55-1
The precise position measurement of the mask substrate 55-1 is performed using the alignment marks provided in (1) (S103). This is sequentially repeated for the mask substrates 55-2 to 55-4 to obtain position information of each substrate (S 104, S 105, S 10
6). Transfer exposure is performed based on the obtained positional information of each substrate (S107).

FIG. 4 is a flowchart showing an example of a sequence for transferring and exposing a semiconductor device chip pattern using the mask shown in FIG. 1, which is different from the sequence shown in FIG. First, the mask is set on the mask stage (S20
1) Next, the position of the mask frame is measured using the rough alignment mark (S202), and then the precise alignment of the mask substrate 55-1 is performed using the alignment mark provided on the mask substrate 55-1. Perform position measurement (S2
03). Up to this point, the sequence is the same as that in FIG. However, following the measurement, the mask substrate 55-1 is measured based on the measurement data of the mask substrate 55-1 obtained in S203.
Is immediately performed (S204). Then, with respect to each of the mask substrates 55-2 to 5-4, transfer exposure of each mask substrate pattern is performed immediately after the measurement of the mask substrate. That is, exposure is performed immediately after the position of each substrate is precisely measured. In this sequence, as compared with the sequence of FIG. 3, the number of times of switching between the alignment and the exposure is increased, so that the throughput is reduced. However, it is possible to perform the exposure with higher precision.

That is, in the first aspect of the present invention, the alignment of the mask is performed for each substrate, so that even if the mask is divided into a plurality of substrates and manufactured, the positional accuracy of exposure does not decrease. In addition, since the region where the mask is aligned is smaller than the case where the entire surface of the mask is aligned, the required specifications for the absolute positional accuracy of the pattern on the mask are relaxed.

Next, a second embodiment of the present invention will be described. FIG. 5 is a schematic plan view of a mask used in transfer exposure according to one example of the second aspect of the present invention. This mask 6
Reference numeral 1 denotes that a pattern area is divided into a plurality of sub-areas (sub-fields) 63, and this sub-area 63 is used for one-shot exposure.
Is exposed on the wafer in a reduced size. In this example, eight mask alignment marks 65 provided on the mask are provided.
The position coordinates of the mask are measured on the mask stage of the exposure apparatus, and the results of the measurement are statistically processed to determine the position, rotation,
Deriving a function representing expansion / contraction, orthogonality, etc. How to derive the correction function will be described later. At the time of exposure, exposure is performed while correcting the arrangement of the sub-regions, the rotation error, and the like based on the derived correction function. Thereby, the influence of the error of the mask on the wafer pattern is reduced.

Here, an example of a method of obtaining the correction function will be described. First, it is premised that a plurality of sub-fields arranged substantially regularly in accordance with the arrangement coordinates on the mask and alignment marks associated with each of the sub-fields are formed on the mask. The mask is moved two-dimensionally, and each of the plurality of sub-fields is sequentially aligned with a predetermined reference position based on the following procedure. (A) The coordinate positions of some of the sub-fields on the mask are measured, and the actual coordinate system of the sub-fields on the mask is designed based on the measured coordinates and the design position coordinates. Create an error parameter for the array coordinate system. (B) a first statistic related to a random position error that the array coordinates of the sub-field of view on the mask has with respect to the array coordinates of the design, and are included in the measurement result when measuring the position of the mark of the sub-field of view. And a second statistic associated with the random measurement result to be obtained. (C) Using the error parameter, the first statistic, and the second statistic, create a position estimation filter for outputting the estimated coordinate value of the sub-field of view based on the least squares estimation rule. I do. (D) After the position estimation filter is determined, an actually measured coordinate value obtained by detecting the mark of the sub-field of view is input to the position estimation filter, and the estimated coordinates of the sub-field of view output from the filter are output. The mask is positioned based on the value. This correction function (position estimation filter) and the enhanced global alignment (E
For GA), see JP-A-3-153015, JP-A-62-291133, and JP-A-61-44429.

FIG. 6 is a schematic plan view of a mask used in transfer exposure according to an embodiment of the second aspect of the present invention when the mask is divided into a plurality of mask substrates. The mask 71 includes all patterns of one DRAM chip, and is divided into two mask substrates 75-
1, 75-2 are juxtaposed on the frame 73.
The material and manufacturing method of the frame 73 and each of the mask substrates 75-1 and 75-2 are the same as those of the mask of FIG.

In this embodiment, eight alignment marks 77 are formed on each of the mask substrates 75-1 and 75-2. With the same method as that described with reference to FIG. 5, alignment mark positions are measured for each of the mask substrates 75-1 and 75-2 to derive a correction function.
At the time of exposure, transfer exposure is performed while correcting the position of each sub-region in each mask substrate. Thereby, even when the mask is divided, deviation of the exposure pattern due to various factors is reduced.

FIG. 7 shows an example in which the pattern area of the mask is divided into three block areas.
In this case, the pattern areas 85-1, 85-2, 85-
3 is divided into sub-regions as shown in FIG. At this time, the correction function as described above is derived for each pattern area, and the exposure is performed by performing correction at the time of exposure, so that an error of the mask substrate can be corrected, and more accurate exposure can be performed. Further, since the correctable range is widened, there is an effect that the required accuracy for the mask is eased. The path of the arrow shown in FIG. 7 is an example of movement of the mask stage when measuring the mark position. In the case of operating the mask stage as indicated by the arrow at the time of actual exposure, the mark position measurement is also performed while operating the mask stage along the same path. As a result, a measurement result reflecting the stage and the deflection characteristics of the exposure apparatus can be obtained, and more accurate exposure can be performed.

[0030]

As is apparent from the above description, according to the first aspect of the present invention, the alignment of the mask is performed for each substrate, so that even if the mask is divided into a plurality of pieces, the position of the exposure is changed. Accuracy does not decrease. In addition, since the region where the mask is aligned is smaller than the case where the entire surface of the mask is aligned, the required specifications for the absolute positional accuracy of the pattern on the mask are relaxed. Further, according to the second aspect of the present invention, by performing exposure using the correction function of the pattern position of the mask, a more accurate exposure pattern on the wafer can be obtained.

[Brief description of the drawings]

FIG. 1 is a plan view showing a mask according to an example of the first aspect of the present invention.

FIG. 2 is a view showing an outline of a division transfer type electron beam exposure apparatus to which the present invention is applied.

FIG. 3 is a flowchart showing an example of a sequence for transferring and exposing a semiconductor device pattern using the mask of FIG. 1;

FIG. 4 is a flowchart illustrating an example of a transfer exposure sequence according to an embodiment different from the sequence of FIG.

FIG. 5 is a schematic plan view of a mask used in transfer exposure according to an example of the second aspect of the present invention.

FIG. 6 is a schematic plan view of a mask divided into a plurality of mask substrates used in transfer exposure according to another example of the second aspect of the present invention.

FIG. 7 is a schematic plan view of a mask used in transfer exposure according to another embodiment of the second aspect of the present invention, in which a pattern area is divided into a plurality of block areas.

[Explanation of symbols]

Reference Signs List 1 electron gun 6, 7 opening 8 deflector 12, 13 projection lens 11 mask stage 14 wafer 15 wafer stage 16 electron beam detector 51 mask 53 frame 54 window hole 55 divided mask substrate 57 rough alignment mark 59 fine alignment mark 61 mask 63 Pattern sub-area 63 Alignment mark

Claims (7)

[Claims] 1. A transfer exposure method for applying an energy beam to a pattern formed on a mask and forming and transferring an energy beam patterned through the mask onto a sensitive substrate; A mask covering the pattern area is divided into a plurality of mask substrates to produce a plurality of mask substrates, the plurality of mask substrates are juxtaposed in a transfer exposure apparatus, and for each of the plurality of mask substrates, A transfer exposure method comprising measuring coordinates, performing exposure position correction based on the measured individual mask substrate coordinates, and performing transfer exposure of a pattern on the mask substrate. 2. A transfer exposure apparatus for irradiating a pattern formed on a mask with an energy beam and image-transferring the patterned energy beam through the mask onto a sensitive substrate; Divided into mask substrates,
Means for judging coordinates of each of the plurality of mask substrates individually for each of the plurality of mask substrates, and exposing based on each of the measured individual mask substrate coordinates; And a means for performing position correction and transfer exposure. 3. A mask on which a transfer pattern is formed, comprising: a plurality of divided mask substrates arranged side by side; each of the plurality of mask substrates being capable of measuring a position on a mask stage in an exposure apparatus. A pattern transfer mask provided with an alignment mark. 4. A transfer exposure apparatus for irradiating a pattern formed on a mask with an energy beam and passing the mask through the mask to image-transfer the patterned energy beam onto a sensitive substrate; A plurality of position measurement marks that are not on the same straight line are provided; a means for measuring the position of each mark on a mask stage in the exposure apparatus; A transfer exposure apparatus comprising: means for obtaining a correction function for correcting a position error; and means for correcting an exposure position based on the correction function. 5. The apparatus according to claim 1, wherein the mask is divided into a plurality of mask substrates and is arranged side by side in an exposure apparatus. The position measurement mark is provided for each mask substrate. 5. The transfer exposure apparatus according to claim 4, wherein a correction function for correcting a positional error of the pattern arrangement of the mask for each substrate is obtained. 6. The pattern on the mask or the mask substrate is divided into a plurality of block areas, the position measurement mark is provided for each block area, and the means for obtaining the correction function comprises: 6. The transfer exposure apparatus according to claim 4, wherein a correction function for correcting a position error of the pattern arrangement of the mask is obtained every time. 7. The moving direction or moving path of the mask stage when performing the mark position measurement is the same as the moving direction or moving path of the mask stage when exposing an actual transfer pattern. 4, 5 or 6
The transfer exposure apparatus as described in the above.