JP2000058445A - Electron beam transfer equipment and semiconductor device manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide equipment capable of magnification adjustment, rotation adjustment and focal point adjustment in a short time, in imaging to a mask of an illumination beam molding aperture in an electron beam transfer equipment. SOLUTION: In this electron beam transfer equipment, an illuminating lens 8 has a U-shaped magnetic pole 8a which is opened to the optical axis side. Three kinds of adjusting coils 22, 28, 26 are arranged in the vicinity of a molding aperture side magnetic pole, in the vicinity of a mask side magnetic pole and in a central part, respectively, in the magnetic pole. Focal point adjustment is performed by using the adjusting coil 28, and adjustment for rotation is performed by making a current flow, in such a manner that the magnetic fields in the same direction are generated in the adjusting coils 22 and 26. It is assumed temporarily that a current is so made to flow such that the magnetic fields in the reverse directions are generated in the adjusting coils 22 and 26. Currents to be made to flow in the three kinds of adjusting coils are calculated in accordance with the changes in three parameters of focal point, rotation and magnification with the use of simultaneous equations, and magnification adjustment is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to an electron beam transfer apparatus intended to form a fine and high-density pattern of m or less with high throughput. In particular, the present invention relates to an electron beam transfer apparatus improved so that the imaging parameters of a mask illumination beam can be accurately adjusted and transfer accuracy can be further improved. Furthermore, the present invention relates to a method for manufacturing a highly accurate semiconductor device using such an electron beam transfer device.

[0002]

2. Description of the Related Art In this type of apparatus, an electromagnetic lens is used for pattern reduction and image formation. Further, in order to correct the imaging parameters of the electromagnetic lens, a dynamic focus coil and a rotation adjustment coil for correcting focusing and rotation of an image at high speed are used. In addition, Japanese Patent Application Laid-Open
235469 discloses an apparatus in which a projection optical system for reducing and transferring a mask image onto a wafer is provided with a lens for mainly adjusting magnification and a lens for mainly adjusting rotation.

[0003]

In the above prior art, the adjustment of the imaging parameters in the projection optical system was considered, but the adjustment of the imaging parameters of the illumination beam shaping aperture on the mask was completely considered. I didn't. In addition, rotation and defocus caused by changing the magnification are not taken into consideration, and fluctuations in focus and magnification caused by adjusting the rotation are not taken into account.

An object of the present invention is to provide an apparatus capable of adjusting magnification, rotation, and focus in a short time when an image of an illumination beam shaping aperture is formed on a mask in an electron beam transfer apparatus. Still another object of the present invention is to provide a method for manufacturing a highly accurate semiconductor device using such an electron beam transfer device.

[0005]

In order to solve the above-mentioned problems, an electron beam transfer apparatus according to the present invention comprises a step-and-repeat type or a continuous scanning type in which a mask having a pattern to be transferred to a sensitive substrate is provided for each partial area. An illumination optical system that illuminates the substrate with an electron beam, and projection optics that project an image of the patterned electron beam through the mask at an appropriate position on the sensitive substrate and connect the image of the small pattern area on the sensitive substrate. A system for transferring the entire pattern while changing the condition of the optical system for each small area; the illumination optical system irradiating the mask with an electron beam (illumination beam).
A shaping aperture for shaping the outer shape of the lens, an illumination lens for forming an image of the shaping aperture on a small area of the mask, at least three types of adjustment coils arranged near the lens, and a control unit for controlling each unit. The control unit comprises:
By controlling the current flowing through each type of adjustment coil, it is possible to adjust at least one of the three parameters of the aperture image magnification, the rotation of the aperture image, and the focal point of the aperture image without affecting the other parameters. Features.

In the present invention, when an image of the illumination beam shaping aperture is formed on one pattern small area on the mask, magnification, rotation, and focus can all be adjusted only by electric signals without mechanically moving parts. Excellent in stability, high-speed response. A semiconductor device manufacturing method according to the present invention is characterized in that exposure in a lithography step is performed using the above-mentioned electron beam transfer apparatus.

[0007]

In the electron beam transfer apparatus according to the present invention, the illumination lens has a U-shaped magnetic pole opened on the optical axis side, and the three kinds of adjusting coils are provided with the (a) of the magnetic pole. )
In the vicinity of the magnetic pole on the forming opening side, (b) in the vicinity of the magnetic pole on the mask side,
(C) It is preferable to be arranged at any one of the central portions. When one of the imaging parameters is changed by operating each adjustment coil, the change of the other parameters is small, and it is easy to adjust each parameter separately from the other parameters.

Further, in the electron beam transfer apparatus of the present invention, at least a part of a magnetic flux path formed by the three types of adjustment coils is formed of a ferromagnetic material such as ferrite, and is used to select a small pattern area of the mask. Synchronous and high speed 3
It is preferable that one of the imaging parameters is adjusted. Also, since the path of the magnetic flux of the magnetic field that changes these three parameters does not pass through a ferromagnetic material other than ferrite, the above-mentioned imaging parameters should be dynamically corrected even when exposing a small area on a mask far from the optical axis. Can be.

Hereinafter, description will be made with reference to the drawings. First, an example of a division mode of a semiconductor device pattern on a mask (reticle) used in an electronic transfer exposure and exposure method of a division transfer system will be described with reference to FIG. The vertical direction (the width direction of the scanning band 63) in FIG. 2 is the Y direction, and the horizontal direction (the longitudinal direction of the scanning band 63) is the X direction. For example, a mask in which an opening pattern is formed on a Si wafer by etching (stencil type) and a mask in which a high-scattering body pattern film is formed on a Si membrane (membrane type) are being studied. In this example, the entire pattern 61 of the chip on the mask has a rectangular shape. The chip pattern 61 is divided into a number of scanning bands 63 extending in a band shape in the X direction. A typical example of the size of one scanning band 63 on the mask is slightly more than 1 mm in width and 20 to 40 mm in length.

In the Y direction of the chip pattern 61, several tens
Several hundred scanning bands 63 are arranged, and a row of the scanning bands is called a stripe 62. The stripes 62 are provided in about 3 to 7 rows in the X direction. A non-pattern area 65 having a width of about 0.1 mm is provided around the scanning band 63 in a frame shape. The center portion of the non-pattern area 65 is slightly thicker (1 mm in thickness) on the actual mask to give the mask rigidity, and also serves as a reinforcing portion. The thickness of the area where the pattern is formed is 2.0 μm, for example.
It is. At the time of transfer exposure, the non-pattern area 65 is canceled on the wafer, and the patterns of all the scanning bands are joined together over the entire chip. Note that the transfer reduction rate is 1 /
4 are being considered. The size of one chip on the wafer is assumed to be 27 mm in the X direction and 44 mm in the Y direction in a 4GDRAM. In this case, the entire size including the non-pattern portion of the chip pattern on the mask is 120 to 120 in the X direction.
It is about 150 mm and about 150 to 250 mm in the Y direction.

When the chip pattern 61 shown in FIG. 2 is transferred, the mask is illuminated by moving the illumination beam (formed aperture image of the illumination optical system) in each scanning band 63 while deflecting it in the X direction. The shape of the illumination beam is a rectangle slightly wider than the width of the scanning band 63. The area of the scanning band illuminated by the illumination beam at a certain moment is the exposure unit area on the mask. The beam patterned after passing through the mask is reduced and deflected in the projection optical system, guided to a position on the wafer where the pattern is to be projected, and imaged. Note that a non-pattern area is also provided in the scanning band 63,
A method of moving the illumination beam in the scanning band 63 in a step-and-repeat manner is also possible. Note that correction such as dynamic focus adjustment is performed even during scanning of one scanning band, thereby realizing low aberration projection imaging.

On the other hand, in order to advance the exposure to the next scanning band 63, the mask (mask stage) and the wafer (wafer stage) are synchronously and continuously or intermittently moved in the Y direction. Normally, the moving direction of the stage is reversed because the image is reversed by the projection optical system. When the stage is continuously moved, the scanning band 63 on the mask moves in the Y direction even while one scanning band 63 is being exposed, and the scanning band 63 is projected on the wafer to be projected. Also moves in the Y direction. Even in such a movement in the Y direction, the illumination beam and the pattern beam are deflected to strike the beam at a correct position. When moving to the next stripe 62 'after the exposure of one stripe 62 is completed, the exposure is temporarily stopped and the mask stage and the wafer stage are moved in the X direction, and the next stripe 62' on the mask and its transfer area are transferred to the next stripe 62 '. The portion of the wafer to be hit is positioned near the optical axis of the exposure apparatus.

FIG. 3 is a diagram showing an image forming relationship in the entire optical system of the electron beam reduction transfer device used in the electron beam transfer device according to one embodiment of the present invention. The electron gun 1 emits an electron beam downward. Two stages of condenser lenses 2 and 3 are provided below the electron gun 1, and the electron beam passes through these condenser lenses 2 and 3 and forms an image of a crossover CO on a blanking aperture 7. Lens 3
A blanking deflector 4 is disposed directly above the mask 9. When electron beam illumination is not applied to the mask 9, the deflector 4 moves the crossover CO to a position blocked by the blanking opening 7. By using the two condenser lenses 2 and 3 as a zoom lens, the current density of the illumination beam illuminating the mask 9 can be varied.

Below the condenser lens 3, a molding opening 5 is provided.
Is provided. This shaping opening 5 is for shaping the outer shape of the mask illumination beam. The image of the opening 5 is formed on the mask 9 by the illumination lens 8.

A scanning deflector, which will be described later with reference to FIG. 1, is disposed at substantially the same height as the blanking opening 7. The scanning deflector sequentially scans the illumination beam in the X direction (left-right direction) in FIG. 3 to perform exposure of all regions in one scanning band (reference numeral 63 in FIG. 2) on the mask. An illumination lens 8 is arranged below the blanking opening 7. The illumination lens 8 converts the electron beam into a parallel beam, impinges on the mask 9, and forms an image of the shaped aperture 5 on the mask 9.
In the optical system of the electron beam transfer device, the image of the molding opening 5 is reduced and formed on the mask 9. The reduction system is used in order to reduce the thermal load of the electron beam applied to the forming opening 5.

Although only one small area on the optical axis of the mask 9 is shown in FIG.
Direction), and has many scanning bands and stripes as described with reference to FIG. When sequentially illuminating one scanning band, the electron beam is deflected by the scanning deflector as described above.

The mask 9 is placed on a mask stage 15 that can move in the X and Y directions. The wafer 13 as a sensitive substrate is also placed on the wafer stage 17 that can move in the X and Y directions. By scanning the mask stage 15 and the wafer stage 17 in opposite Y directions, each scanning band in the stripe 62 of the chip pattern in FIG. 2 is sequentially exposed. Furthermore, by scanning both stages 15 and 17 intermittently in the X direction,
Each stripe 62 is exposed. In addition, both stages 1
5 and 17 are equipped with an accurate position measuring system using a laser interferometer, and the respective scanning bands are accurately joined on the wafer 13 by adjusting a separate alignment means and a deflector.

Below the mask 9, a two-stage projection lens 10 is provided.
And 12 and a deflector (not shown).
The electron beam patterned by the mask 9 is 2
The image is reduced and deflected by the projection lenses 10 and 12 of the stage, and is imaged at a predetermined position on the wafer 13. An appropriate resist is applied on the wafer 13, and the resist is given a dose of an electron beam to transfer a reduced pattern of a mask image onto the wafer 13. Wafer 13
As described above, it is mounted on the wafer stage 17 movable in the direction perpendicular to the optical axis. A crossover CO is formed at a point where the space between the mask 19 and the wafer 13 is internally divided at a reduction ratio. At the crossover position, a contrast opening 11 is provided. The opening 11 blocks the non-pattern beam scattered by the mask from reaching the wafer 13.

Next, the main part of the illumination optical system of the electron beam transfer apparatus of the present embodiment will be described in more detail with reference to FIG. FIG. 1 is a cross-sectional view showing the main part of the illumination optical system of the electron beam transfer device of the present embodiment in more detail. The illumination lens 8 is arranged below the molding opening 5 and houses the blanking opening 7 therein. The illumination lens 8 has a cylindrical shape that is rotationally symmetric about the optical axis as a whole and has a U-shaped magnetic pole 8a that is open to the optical axis side.
The magnetic pole 8a is made of permalloy or the like. Inside the magnetic pole 8a, a generally cylindrical excitation coil 8b is housed. A ring-shaped upper pole 8c made of ferrite is incorporated in the inner periphery of the upper side of the magnetic pole 8a. A ring-shaped lower pole 8d made of ferrite is also provided on the inner periphery of the lower side of the magnetic pole 8a.
Is incorporated.

A ferrite stack 20 in which a large number of insulating rings 20a and ferrite rings 20b are stacked is fitted in the inner peripheral portion of the exciting coil 8b.
The ferrite stack 20 functions as a magnetic shield that prevents a magnetic field generated by various adjustment coils 22, 26, and 28 and a deflector group 24 from leaking into a magnetic circuit of the illumination lens. On the inner periphery of the ferrite stack 20,
A middle adjustment coil 26 is wound around the ferrite stack 20 and the exciting coil 8b in the direction of the optical axis, and is wound uniformly in the illumination lens 8 in the vertical direction.

The inner peripheral portion of the middle adjustment coil 26 has an upper pole 8c
The upper adjustment coil 22 having a relatively small width (height) is disposed directly below the lower electrode 8, and a similar lower adjustment coil 28 is disposed immediately below the lower pole 8 d. In this example, four deflector groups 24 in this example are arranged on the inner peripheral portion of the middle adjusting coil 26 between the upper adjusting coil 22 and the lower adjusting coil 28 so as to be vertically stacked.

Next, the operation of the adjusting coil and the deflector in the illumination lens 8 will be described. Selection (scanning) of one pattern small area (sub-field) in the scanning band is performed by the deflector group 24. Aberration due to deflection is T.Hosoka
Wa, Optik, 56, No. 1 (1980) 21-30, the correction is made by increasing the number of deflectors.
On the other hand, the field curvature is determined by adjusting the middle adjustment coil 26 wound around the entire lens inside the ferrite stack 20, the upper adjustment coil 22 wound near the upper (formed aperture) side magnetic pole 8c of the lens, and the The correction is made by the lower adjustment coil 28 wound near the mask side (lower) magnetic pole 8d. The details are mainly focused by the middle adjustment coil 26,
The resulting rotation or change in magnification is corrected by the upper and lower adjustment coils 22 and 28.

The magnification adjustment is performed, for example, as follows. That is, a current is applied to the upper adjustment coil 22 in a direction to increase the lens magnetic field, and a reverse current is applied to the lower adjustment coil 28 to move the main surface of the lens 8 upward equivalently, thereby increasing the magnification. Conversely, the magnification decreases. At this time, the middle adjustment coil 26 and the lower adjustment coil 28
If the absolute values of the currents flowing through are made equal, rotation and focus change hardly occur.

The rotation adjustment is performed, for example, as follows. That is, a current is caused to flow through the upper adjustment coil 22 and the lower adjustment coil 28 in a direction that generates a magnetic field in the same direction, and the rotation amount can be increased or decreased in either the same direction or the opposite direction to the original direction of the magnetic field. Although there is almost no change in magnification due to this rotation, a change occurs in the focal point, and the amount may be adjusted by the middle adjustment coil 26.

In practice, given the amount of rotation, the amount of change in magnification, and the amount of change in focus, simultaneous equations are set so that the currents flowing through the three coils (the middle adjustment coil 26, the upper adjustment coil 22, and the lower adjustment coil 28) are determined. May be calculated by a computer, and the current value may be given to the adjustment coil.

Next, an example of the mode of use of the exposure apparatus of the present invention will be described. FIG. 4 is a flowchart showing an example of the semiconductor device manufacturing method of the present invention. The manufacturing process of this example includes the following main processes. Wafer manufacturing process for manufacturing a wafer (or wafer preparing process for preparing a wafer) Mask manufacturing process for manufacturing a mask to be used for exposure (or mask preparing process for preparing a mask) Wafer processing process for performing necessary processing on a wafer Wafer Chip assembling step of cutting out the chips formed on the chip one by one to make it operable Chip inspecting step of inspecting the resulting chips Each of the steps further includes several sub-steps.

Among these main processes, the main process that has a decisive effect on the performance of a semiconductor device is a wafer processing process. In this step, designed circuit patterns are sequentially stacked on a wafer, and a number of chips that operate as memories and MPUs are formed. This wafer processing step includes the following steps. A thin film forming step (using CVD, sputtering, etc.) for forming a dielectric thin film serving as an insulating layer, a wiring portion, or a metal thin film forming an electrode portion (using CVD or sputtering, etc.) A lithography process of forming a resist pattern using a mask (reticle) in order to selectively process etc. An etching process of processing a thin film layer or a substrate according to a resist pattern (for example, using a dry etching technique) An ion / impurity implantation diffusion process Resist stripping step Inspection step for inspecting the processed wafer Further, the wafer processing step is repeated by a necessary number of layers to manufacture a semiconductor device that operates as designed.

FIG. 5 is a flowchart showing a lithography step which is the core of the wafer processing step shown in FIG. This lithography step includes the following steps. A resist coating step of coating a resist on a wafer on which a circuit pattern has been formed in the preceding step An exposing step of exposing the resist A developing step of developing the exposed resist to obtain a resist pattern Stabilizing the developed resist pattern Annealing Step for Using the exposure apparatus of the present invention in the above-mentioned exposure step, the accuracy of pattern formation in the lithography step is greatly improved.
In particular, the process related to realizing the required minimum line width and the overlay accuracy corresponding thereto is a lithography process, in particular, an exposure process including alignment control, and it has been difficult until now by applying the present invention. Semiconductor devices can be manufactured.

[0029]

As is apparent from the above description, according to the present invention, in an electron beam transfer apparatus intended to form a high-throughput fine and high-density pattern having a minimum line width of 0.1 μm or less, It is possible to provide an electron beam transfer apparatus improved so that the imaging parameters of the mask illumination beam can be accurately adjusted and the transfer accuracy can be further improved.
Further, a method for manufacturing a semiconductor device with high accuracy using such an electron beam transfer apparatus can be provided.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a main part of an illumination optical system of an electron beam transfer apparatus according to the present embodiment in more detail.

FIG. 2 is a diagram illustrating an example of a division form of a semiconductor device pattern on a mask used for electron beam transfer exposure in a division transfer system.

FIG. 3 is a diagram showing an image forming relationship in the entire optical system of the electron beam transfer device according to one embodiment of the present invention.

FIG. 4 is a flowchart illustrating an example of a semiconductor device manufacturing method according to the present invention.

FIG. 5 is a flowchart showing a lithography step which is the core of the wafer processing step shown in FIG. 4;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Electron gun 2, 3 Condenser lens 5 Molding opening 7 Blanking opening 8 Illumination lens 8a Magnetic pole 8b Exciting coil 8c Ferrite upper pole 8d Ferrite lower pole 9 Mask 10 Projection lens 11 Contrast aperture 12 Projection lens 13 Wafer 17 Wafer stage 20 Ferrite stack Reference Signs List 20a Insulator ring 20b Ferrite ring 22 Upper adjustment coil 24 Deflector group 26 Medium adjustment coil 28 Lower adjustment coil 61 Chip pattern 62 Stripe 63 Scan band 65 Non-pattern area

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 21/30 541F

Claims (5)

[Claims] An illumination optical system for irradiating a mask having a pattern to be transferred to a sensitive substrate with an electron beam in a step-and-repeat manner or a continuous scanning manner for each small area, and patterned through the mask A projection optical system for projecting and forming an electron beam at an appropriate position on the sensitive substrate, and connecting an image of each pattern small area on the sensitive substrate,
An apparatus for transferring an entire pattern while changing the condition of an optical system for each small area; said illumination optical system comprising: a forming opening for forming an outer shape of an electron beam (illumination beam) for illuminating a mask; An illumination lens that forms an image of the image on a small area of the mask, at least three types of adjustment coils disposed near the lens, and a control unit that controls each unit; 3
By controlling the current flowing through each type of adjustment coil, it is possible to adjust at least one of the three parameters of the aperture image magnification, the rotation of the aperture image, and the focal point of the aperture image without affecting the other parameters. Characteristic electron beam transfer device. 2. The illumination lens has a U-shaped magnetic pole opened to the optical axis side, and the three kinds of adjusting coils are (a) near the formed opening-side magnetic pole of the magnetic pole, and (b) a mask. 2. The electron beam transfer device according to claim 1, wherein the electron beam transfer device is disposed at any one of a position near the side magnetic pole and at a central portion of the electron beam. 3. The focus is adjusted by the adjustment coil arranged in (b), and a current is supplied so that a magnetic field in the same direction is generated in the adjustment coil arranged in (a) and the adjustment coil arranged in (c). The rotation is adjusted by flowing the current, and it is temporarily determined that a current is caused to flow in the adjustment coil arranged in (a) and the adjustment coil arranged in (c) so that a magnetic field in the opposite direction is generated. 3. The electron beam transfer apparatus according to claim 2, wherein a magnification adjustment is performed by calculating and determining currents flowing through the three types of adjustment coils by simultaneous equations according to a change in a parameter. 4. A method according to claim 1, wherein at least a part of a magnetic flux path formed by said three types of adjusting coils is formed of ferrite, and said three imaging parameters are adjusted at high speed in synchronization with selection of a small pattern area of said mask. 4. The electron beam transfer apparatus according to claim 1, wherein: 5. A method for manufacturing a semiconductor device, comprising performing exposure in a lithography step using the electron beam transfer apparatus according to claim 1.