JP3039390B2 - Electron beam mask, exposure apparatus using electron beam mask and exposure method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron beam mask, an exposure apparatus using the electron beam mask, which exposes a circuit pattern of a semiconductor integrated circuit or the like formed on the mask using an electron beam onto a semiconductor substrate. It relates to the exposure method.

[0002]

2. Description of the Related Art In recent years, semiconductor devices represented by memory devices have been required to have higher densities, higher performance, and higher functions. Accordingly, the semiconductor device manufacturing process, especially lithography for forming fine patterns, has been required. Even advanced technology is required. As a technique satisfying these techniques, an electron beam exposure method having high resolution is used.
FIG. 3 is a schematic view of an electron beam exposure apparatus and a substrate to be exposed for explaining a conventional electron beam exposure method.

An electron beam 111 generated from an electron gun 101 is formed into a rectangular shape by an opening formed on an aperture 102, and is irradiated to a desired opening on an electron beam mask 106 by a cell selecting deflector 104 and a forming deflector 105. Is done.
On the electron beam mask 106, a variable-shaped opening 107 for forming a rectangle of an arbitrary size and various device pattern shape openings 108 are formed at a plurality of locations. Here, a pattern that is repeatedly used in the entire device pattern, such as a part of a memory cell pattern or a part of an array pattern of the memory device, is formed in the pattern opening 108. For exposure of a pattern having no or little repetition such as a peripheral circuit pattern, a rectangular electron beam of an arbitrary size is formed by changing the position of an electron beam applied to the variable shaping opening 107, as in a single stroke. Expose the patterns one by one.

An electron beam 111 formed into a desired pattern shape by an electron beam mask 106 is irradiated onto a substrate 110 to be exposed by a return deflector 109 to sequentially expose a device pattern. At this time, the amount of deflection of the electron beam 111 formed into a desired pattern shape by the reversing deflector 109 depends on the distance between each pattern shape opening 108 passing through the variable shaping opening 107 on the electron beam mask 106. This is obtained by multiplying the reduction ratio of the electron beam exposure apparatus. If the amount of deflection of the electron beam 111 by the return deflector 109 is not accurate, the variable shaping aperture 10 is formed on the substrate 110 to be exposed.
7 and the opening 108 of each pattern shape
Position deviation from the electron beam 111 that has passed through, causing problems such as deterioration of connection accuracy, deterioration of overlay accuracy between layers, or disconnection of a pattern.

[0005] One of the causes of the inaccurate deflection amount caused by the swing-back deflector 109 is the manufacturing accuracy of the electron beam mask 106. FIG. 4 shows a method of manufacturing the electron beam mask 106.
(A) to (e). In FIG. 4A, the substrate 40
A resist is coated on the substrate 1 and a desired pattern is exposed by light exposure or electron beam exposure using a reticle, thereby forming a desired pattern etching mask 402. Thereafter, as shown in FIG. 4 (b), the substrate 401 is etched to form a desired pattern opening, and as shown in FIG. 4 (c), a mask 403 for back surface etching is formed. (FIG. 4D). Finally, as shown in FIG. 4E, a conductive layer 4 of Au, W, Ti, etc.
04 is formed. In the above steps, the distance between the variable-shaped opening 107 on the electron beam mask 106 and each pattern-shaped opening 108 cannot be accurately formed due to lithography accuracy, warpage of the substrate 401 between the steps, and the like.

To solve this problem, an electron beam mask 1
06, a reference mark on the stage is scanned with an electron beam 111 formed by each pattern-shaped opening 108, and the reflected electron waveform is compared with an ideal waveform to correct the deflection amount by a return deflector 109. It has been proposed (Japanese Patent Application No. 3-188616). This method will be described in detail with reference to FIG.

FIGS. 5A and 5B are views for explaining a conventional alignment method, wherein FIG. 5A shows a state in which a reference mark is scanned with a formed electron beam, and FIG. 5B shows an ideal reflected electron waveform and a reflected electron waveform. This shows the situation for measuring the deviation.

[0008] As shown in FIG.
The reference mark 502 made of Au, W, Ti, or the like on the stage is scanned by using the electron beam 501 formed by passing through each pattern-shaped opening 108 on 6. Next, fitting is performed between the obtained backscattered electron waveform 503 and the ideal backscattered electron waveform 504 calculated from the opening pattern shape, and a shift between the two is calculated. Thus, the variable shaping aperture 1
07, the electron beam 501 that has passed through
The amount of misalignment with the electron beam 501 that has passed through 08 is measured (FIG. 5B), and is fed back to the offset value of the return deflector.

[0009]

In the conventional example, the error in the amount of deflection of the electron beam 111 formed through each pattern-shaped opening 108 on the electron beam mask 106 by the return deflector is determined by the above-described method. The reference mark 502 on the stage is scanned with the reflected electron beam 501, and the reflected electron waveform 503 is obtained.
However, in the case of a pattern having a small current amount of the electron beam to be scanned, such as a compact pattern, the reflected electron intensity is weakened, so that the S / N is deteriorated and the accuracy is good. Cannot measure. Further, when the shape and dimensions of each pattern shape opening 108 are not accurate with respect to the design, there is a problem that an accurate offset value of the deflection amount cannot be calculated.

An object of the present invention is to solve the above-mentioned problems and to improve an electron beam mask capable of improving the pattern position accuracy in a memory cell area or an array area, an exposure apparatus using the electron beam mask, and an exposure apparatus using the same. It is to provide a method.

[0011]

According to the present invention, there is provided an electron beam mask having a variable shaping opening for shaping an electron beam into a desired shape and a plurality of transfer opening pattern groups. In the vicinity of each of the variable-shaped opening and the plurality of transfer openings, detection and position recognition of each of the variable-shaped opening and the plurality of transfer openings, and each of the variable-shaped opening and the plurality of transfer openings. A position detection mark for correcting the relative transfer position on the substrate to be exposed.

Further, the position detection mark is optically detectable.

Further, the position detection mark is formed of a material constituting the mask.

[0014] Further, the present invention is characterized in that the position detection mark is formed with an opening.

Also, in an electron beam exposure apparatus that mounts an electronic mask, selects a desired transfer opening on the electronic mask, forms an electron beam, and irradiates the sample onto a sample, a variable-shaped opening and a plurality of transfer opening groups. And an optical system for detecting a position detection mark formed in the vicinity of each of the above.

In the exposure method using the electron beam exposure apparatus, the position detection mark formed near each of the variable forming opening and the plurality of transfer opening groups is detected and recognized by an optical system, and the variable forming opening is detected. The relative transfer positions of the opening and the plurality of transfer opening groups on the substrate to be exposed are corrected.

[0017]

According to the present invention, a position detection mark for position recognition is provided near the variable-shaped opening on the electron beam mask and each transfer opening. Since the distance between the openings can be measured, and the error between the measured distance and the design value is used as the offset value of the deflection amount by the return deflector, the electrons passing through each transfer opening on the substrate to be exposed are The positioning of the electron beam and the electron beam that has passed through the variable shaping opening can be accurately performed.

Further, according to the present invention, since the position detection mark is formed by a Si step or an opening, it can be formed without changing the electron beam mask forming process.

According to the present invention, since an optical system for detecting a position detection mark is provided above an electron beam mask stage in an electron beam exposure apparatus, an error from a design value on an electron beam mask can be directly detected. it can.

By the above operation, the pattern position accuracy of the memory cell pattern area and the array pattern area is improved, and the quality and cost of the LSI can be reduced.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relates to an electron beam mask having a variable shaping opening and a plurality of transfer opening patterns for shaping an electron beam into a desired shape. A position detection mark for recognizing the position of each of the variable-shaped opening and the plurality of transfer opening groups, for example, a cross mark formed by a Si step, is formed near each of the electron beam mask stages. A light source such as a mercury lamp installed in the apparatus, detection and position recognition are performed by an optical mark detector, and a relative transfer position of each of the variable-shaped opening and the plurality of transfer openings on the substrate to be exposed is corrected. Has functions. The position detection mark can be formed simultaneously with the formation of the desired pattern etching mask, or the position detection mark can be formed again after the formation of the desired pattern.

According to the present invention, there is provided an electron beam exposure apparatus in which an electron beam mask is mounted, a desired transfer opening on the electron beam mask is formed, and an electron beam is formed and irradiated onto a sample. An electron beam exposure apparatus provided with an optical system for detecting position detection marks formed in the vicinity of each of the transfer aperture groups.

Further, according to the present invention, in the electron beam exposure method using the electron beam exposure apparatus, a position detection mark formed near each of the variable-shaped opening and the plurality of transfer openings is detected and positioned by an optical system. This is an electron beam exposure method capable of recognizing and correcting the relative transfer positions of the variable forming openings and the plurality of transfer opening groups on the substrate to be exposed.

[0024]

Next, an embodiment will be described with reference to the drawings. (Embodiment 1) FIG. 1 is a schematic view showing an electron beam exposure method according to a first embodiment of the present invention.

The electron beam 111 emitted from the electron gun 101 is deflected by the cell selection deflector 104 to each pattern opening 108 on the electron beam mask 106. The electron beam 111 formed by passing through each pattern-shaped opening 108 is deflected by the return deflector 109 to the same optical axis as the electron beam 111 passed through the variable-shaped opening 107, Exposure to position.

The electron beam 111 passing through each pattern-shaped opening 108 is changed to the electron beam 111 passing through the variable shaping opening 107.
In order to deflect to the same optical axis as described above, it is necessary to deflect by a value obtained by multiplying the distance between the variable shaping opening 107 and each pattern-shaped opening 108 on the electron beam mask 106 by the reduction ratio of the electron beam exposure apparatus. Variable shaped aperture 1 on electron beam mask 106
If the distance between the pattern 07 and each pattern shape opening 108 is incorrect due to an electron beam mask forming process or other reasons, the deflection amount becomes inaccurate and the substrate 1
Electron beam 111 that has passed through variable shaping opening 107 on
And the electron beam 111 passing through each pattern-shaped opening 108
In this case, a positional shift occurs, and problems such as deterioration of connection accuracy and overlay accuracy or disconnection of a pattern occur.

Accordingly, in this embodiment, as shown in FIG. 2, a Si step is formed at the lower left end of the variable shaping opening 107 and each pattern shape opening 108 on the electron beam mask 106 as a position detection mark for recognizing each position. To form a cross mark 201. The cross mark 201 is detected by an optical mark detector 103 installed above an electron beam mask stage (not shown) of the electron beam exposure apparatus, and the distance between the variable shaping opening 107 and each pattern shape opening 108 is measured. Done. The optical mark detector 103 desirably uses a mercury lamp as a light source and utilizes the profile of reflected light scanned on the mark. The error between the measured distance and the design value is set as an offset value of the deflection amount of the electron beam 111 that has passed through each pattern shape opening 108 by the return deflector 109. According to this method, it is possible to measure an error in the amount of deflection of the electron beam 111 due to the accuracy of the creation of the electron beam mask 106,
Can be prevented from being displaced.

In the case of a position measuring instrument using a mercury lamp as an optical system and a profile of reflected light, the accuracy of position measurement when a cross mark 201 due to a step is used as a position detecting mark is 0.03 μm (3σ). ). When the reduction ratio of the electron beam exposure apparatus is 1/25, if the position detection accuracy of 0.1 μm is obtained by the mark detection system, the displacement of the electron beam on the substrate 110 to be exposed is 0.004 μm.
Can be suppressed. (Embodiment 2) Next, a second embodiment of the present invention will be described.

FIG. 2 is a schematic view of the electron beam mask used in the first and second embodiments.

FIG. 2 shows an opening of one layer on the electron beam mask 106. A cross mark 201 for position detection is provided at the lower left end of each of the variable-shaped opening 107 and each pattern-shaped opening 108, and the distance between each opening is measured by detecting the mark. This mark is formed by a Si step. In the electron beam mask making process shown in FIG. 4, the position detection mark can be formed simultaneously with the formation of the desired pattern etching mask 402 in FIG. 4A, or the position detection mark can be formed again after the formation of the desired pattern. It is also possible to carry out the formation. Shape is C
Any figure detectable on a CD or the like may be used. In addition, as long as the electron beam that has passed through the aperture 102 is not irradiated, a pattern that is open to the back surface in the same manner as the opening pattern portion is also possible. (Embodiment 3) Next, a third embodiment of the present invention will be described. The optical mark detector 103 is provided above the electron beam mask stage on which the electron beam mask 106 according to the second embodiment is mounted.
The distance between the variable-shaped opening 107 and each pattern-shaped opening 108 is measured by the optical mark detector 103. The optical mark detector 103 uses a profile of reflected light of scanning light using a light source such as a mercury lamp. When this optical system is used, the detection reproducibility of the Si step mark is about 0.03 μm.
Electron beam 1 that has passed through each pattern-shaped opening on the substrate to be exposed
When the alignment accuracy between the electron beam 11 and the electron beam passing through the variable shaping opening 107 is suppressed to 0.01 μm or less, when the reduction ratio of the electron beam exposure apparatus is 1/25, the accuracy of detecting the position on the electron beam mask 106 is reduced. May be 0.25 μm or less. Also,
A system that measures the position by image recognition using a CCD camera or the like as the optical system is also possible.

[0031]

As described above, according to the present invention, a position detecting mark is provided in the vicinity of the variable-shaped opening on the electron beam mask and in the vicinity of each pattern-shaped opening. By detecting and recognizing this mark by the system, the distance between the variable-shaped opening and each pattern-shaped opening is measured, and the electron beam passing through each pattern-shaped opening and the electron beam passing through the variable-shaped opening are measured. By performing alignment, memory cell pattern areas and array pattern areas with strict pattern position accuracy can be
Exposure can be performed with high positional accuracy.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an electron beam exposure apparatus according to a first embodiment of the present invention.

FIG. 2 is a schematic view of an electron beam mask used in first and second embodiments of the present invention.

FIG. 3 is a schematic view showing a conventional electron beam exposure apparatus.

FIG. 4 is a diagram illustrating a manufacturing process of an electron beam mask.

FIG. 5 is a diagram for explaining a conventional alignment method;
(A) shows a situation in which a reference mark is scanned with a formed electron beam, and (b) shows a situation in which a deviation between an ideal reflected electron waveform and a reflected electron waveform is measured.

[Explanation of symbols]

 REFERENCE SIGNS LIST 101 electron gun 102 aperture 103 optical mark detector 104 cell selection deflector 105 shaping deflector 106 electron beam mask 107 variable shaping opening 108 pattern shape opening 109 swingback deflector 110 exposed substrate 111 electron beam 201 position detection mark 401 substrate 402 Desired pattern etching mask 403 Backside etching mask 404 Conductive layer 501 Electron beam formed after passing through opening pattern 502 Reference mark 503 Detected reflected electron waveform 504 Ideal reflected electron waveform calculated from opening pattern

Claims (6)

(57) [Claims] 1. An electron beam mask having a variable shaping opening and a plurality of transfer opening pattern groups for shaping an electron beam into a desired shape. Recognizing the respective positions of the variable-shaped opening and the plurality of transfer opening groups, and
And relative positions of the plurality of transfer aperture groups on each substrate to be exposed
An electron beam mask, wherein a position detection mark for correcting a target transfer position is formed. 2. An electron beam mask, wherein the position detection mark according to claim 1 is optically detectable. 3. An electron beam mask, wherein the position detection mark according to claim 1 is formed of a material constituting the mask. 4. An electron beam mask, wherein the position detection mark according to claim 1 is formed with an opening. 5. The power supply according to claim 1, wherein
An electron beam exposure apparatus comprising an optical system for detecting a position detection mark formed on a child beam mask. 6. An optical system for detecting and recognizing a position detection mark formed near each of a variable forming opening and a plurality of transfer opening groups for forming an electron beam into a desired shape. An electron beam exposure method, wherein the relative transfer positions of the variable-shaped opening and the plurality of transfer opening groups on the substrate to be exposed are corrected.