JP3016843B2 - Electron beam writing method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial applications]

The present invention relates to an electron beam drawing method and apparatus for drawing a pattern by irradiating an electron beam on a sample such as an X-ray mask or a semiconductor wafer.

[Prior art]

Since the electron beam lithography apparatus can draw a submicron fine pattern, it is necessary to position the sample (drawing target) with high accuracy. FIG. 5 shows a conventional electron beam writing apparatus. On the Χ-Y stage 10, a semiconductor wafer 14 is placed via a sample holder 12. Moving mirrors 16 # and 16Y are fixed to the side surface of the upper plate of the Χ-Y stage 10 with the longitudinal direction of the 鏡 -Y stage 10 perpendicular to the Χ direction and the Y direction. Χ
In order to precisely measure the position coordinates of the Y stage 10, a laser interferometer 18 is arranged on the fixed side. The laser interferometer 18 includes components 20 to 30. The laser beam emitted from the laser 20 is
And the beam splitter 24 splits the reflected light into transmitted light and reflected light.
And the transmitted light enters the Michelson interferometer 26Y. The Michelson interferometer 26Χ has a beam splitter and a fixed mirror (not shown). One light beam split by the beam splitter is reflected by the fixed mirror, and the other light beam is reflected by the moving mirror 16Χ. , Both light beams interfere with each other on the beam splitter, and are projected to the detector 28 'to detect the light intensity. The Michelson interferometer 26Y and the detector 28Y for detecting the Y-direction position of the Χ-Y stage 10 are the same as the Michelson interferometer 26 # and the detector 28 #. The signals detected by the detectors 28 # and 28Y are supplied to the signal processing device 30, and the signal processing device 30 moves the Χ-Y stage 10 from the reference position, that is, the position coordinates of the Χ-Y stage 10 (Χ , Y), and supplies this to the Χ-Y stage controller 32. On the other hand, from the electron beam exposure device 34 to the Χ-Y stage controller 32, the target position coordinates (Χ ₀ ,
Y ₀ ). The Χ-Y stage controller 32
Move the Y stage 10 to match the detected position coordinates (Χ, Y) with the target position coordinates (Χ ₀ , Y ₀ ), and supply a match signal to the electron beam exposure device 34. In response, the electron beam exposure apparatus 34 deflects the electron beam to
The local area on 14 is exposed based on the design data. The measurement accuracy of the laser interferometer 18 having the above configuration is, for example,
It is as high as 0.01 μm, which is suitable for drawing a submicron fine pattern by the electron beam exposure apparatus 34.

[Problems to be solved by the invention]

However, when the semiconductor wafer 14 is irradiated with the electron beam emitted from the electron beam exposure device 34, the semiconductor wafer 14 is heated, and the heat is transferred to the sample holder 12 and
Conduction to the Y stage 10 causes the temperature of the 伝 導 -Y stage 10 to rise. When a current is applied to a coil built in the electron beam exposure apparatus 34 to control the trajectory of the electron beam, the heat generated at this time causes the Χ-Y stage 10 and the sample holder
12 are heated and these temperatures rise. For this reason, Χ
The -Y stage 10 is deformed by thermal expansion, for example, as shown by a two-dot chain line. For example, the coefficient of thermal expansion of aluminum is 25
It is × 10 ^-6 , and a 30 cm aluminum plate extends 7.5 μm when the temperature rises by 1 degree. Therefore, even if the position of the semiconductor wafer 14 with respect to the fixed side is the same, the detection position coordinates (Χ, Y) output from the signal processing device 30 differ depending on the temperature of the Χ-Y stage 10, and the submicron fine In order to draw a pattern accurately, it is not sufficient to use the laser interferometer 18 with high accuracy. An object of the present invention is to provide an electron beam drawing method and apparatus capable of drawing a fine pattern with high accuracy even if a distortion occurs in a movable stage due to a temperature fluctuation in view of such a problem.

Means for Solving the Problems and Their Effects

In the present invention, a first reflector and a second reflector are fixed to the movable stage along one and the other sides of the movable stage adjacent to each other at right angles to each other, and laser light from a laser interferometer is transmitted to the movable stage. The position of the movable stage is detected by irradiating the first reflector and the second reflector, and the movable stage is moved to a target position based on the detected position, and the sample mounted on the movable stage is irradiated with an electron beam. An electron beam writing method for writing a pattern by fixing a plurality of position detection marks on the movable stage along each of the one and the other sides of the side; After a lapse of a set time during the beam exposure, each of the plurality of position detection marks is irradiated with the electron beam to detect secondary electrons emitted from an irradiation point, and process the secondary detection signal. Detecting the position of the mark for a plurality of positions detected by correcting substantially the target position based on the detected position, and correcting the amount of movement of the movable stage. Substantially means that the target position is substantially corrected by apparently correcting the position detected by the laser interferometer or by shifting the range in which the electron beam is swung. I do. According to the method of the present invention, even if the temperature of the movable stage fluctuates by irradiating the sample with an electron beam and the like and the movable stage is distorted due to thermal expansion, it is possible to draw a fine pattern with high precision. Become. The present invention corresponds to the above method invention. Due to a relatively large difference in thermal expansion between the reflector and the movable stage, thermal stress acts on the reflector due to temperature fluctuation of the movable stage, and the reflector is distorted with respect to the movable stage.
If this cannot be neglected, the position correction amount of the movable stage can be made more accurate by disposing the position detection mark at the upper end of the reflector.

【Example】

Hereinafter, an embodiment of an electron beam writing method and apparatus according to the present invention will be described with reference to the drawings. (1) First Embodiment FIG. 1 shows the configuration of an electron beam writing apparatus. The same components as those in FIG. 5 are denoted by the same reference numerals, and description thereof will be omitted. This electron beam writing apparatus forms five rectangular holes at equal intervals along the flow direction of the movable mirror 16 # on the upper surface of the Χ-Y stage 10, and position detecting marks 361 to 365 are formed in each hole.
Similarly, four rectangular holes are formed at regular intervals along the longitudinal direction of the movable mirror 16Y, and position detecting marks 366 to 369 are fitted and bonded to each hole. The position detection marks 361 to 369 have the same shape as each other, and as shown in FIG. 2, grooves are formed on a rectangular metal plate such as tantalum. That is, the position detection mark 36i (i = 1 to 9)
Is composed of a mark 36 for detecting the position in the Χ direction and a mark 36Y for detecting the position in the Y direction. The mark 36Y is formed with a groove parallel to the Y direction in the figure.
A groove is formed parallel to the direction. The widths of the plurality of bars 36a, 36b protruding from these grooves vary according to a certain standard. When the mark 36Y is irradiated with the electron beam 38 emitted from the electron beam exposure device 34, secondary electrons 40 are emitted from the irradiation point and guided to the detector 42 by a grit (not shown), and the amount thereof is measured by the detector 42. Is detected by After the detection signal of the detector 42 is amplified by the amplifier 44, it is binarized by the binarization circuit 46 and stored in the image memory 48. Image memory 48 is addressed based on the scanning signal of electron beam 38. The image processing circuit 50 processes the image stored in the image memory 48 and, for example, a bar located at the center of the mark 36Y with respect to the center line of the electron beam irradiation device 35 (center line of the electron beam path at the time of no deflection). The position dx _{i in} the Χ direction of 36a and the position dy _{i in} the Y direction of the bar 36b located at the center of the mark 36Y are detected and supplied to the potential beam exposure control device 52. The electron beam exposure control device 52 determines the position coordinates (d
x _i , dy _i ), the target position (Χ ₀ ,
Y ₀ ). FIG. 3 shows a procedure for calculating the correction amount. Note that the thermal expansion of the semiconductor wafer 14 is not taken into account in the present invention (solved by another means different from the present invention), so this is ignored. (60) It is determined whether a preset time has elapsed. The set time is a time point before the start of drawing and a time point of, for example, one hour interval from this time point. If the set time has not elapsed, (62) an electron beam exposure process is performed on the semiconductor wafer 14 based on the design data. (64) If the set time has elapsed, the set time is updated to the next set time, and i of the position detection mark 36i is initialized to 1. (66) The position coordinates (X _i0 , Y _i0 ) of the position detection mark 36i set in advance at the time of adjusting the drawing apparatus are supplied to the Χ-Y stage controller 32, and the position detection mark 36i is electronically It is positioned substantially on the center line of the beam irradiation device 35. Χ-
When a match signal is received from the Y stage controller 32,
As described above, the position detection mark 36i is scanned with the electron beam 38 to detect the position coordinates (dx _i , dy _i ) of the position detection mark 36i with respect to the center line of the electron beam irradiation device 35, and this is stored in the memory. Remember. (68) Increment the value of i. (70) If the value of i is equal to or less than the number n (n = 9 in the present embodiment) of the position detection marks 36i, the process returns to step 66 to repeat the process. When i> n, (72) If the process goes through step 72 for the first time, that is, before the start of drawing, the process returns to step 60. (74) If it is not the first time, the position detection mark 36i (i = 1
To n), the differences (Δdx _i , Δdy _i ) between the position coordinates detected for the first time and the position coordinates detected this time are obtained, and from these values, Χ
Calculate the correction amount (ΔΧ ₀ , ΔY ₀ ) of the target position (Χ ₀ , Y ₀ ) at which the Y stage 10 is step-driven and stopped. Since the amount of correction is not always uniform as shown by a dashed line in FIG. 2 due to non-uniformity of temperature distribution and thermal stress distribution,
It depends on the target position (Χ ₀ , Y ₀ ). The calculation of the correction amount is performed, for example, when the laser beam emitted from the Michelson interferometer 26 # is moved to the position detection marks 363 and 364 as shown in FIG.
移動₀ = (1−k) Δdx ₃ + kΔdx ₄ when the light falls on the movable mirror 16 に corresponding to a point internally divided into k: (1−k). The value of k is determined from the target position (Χ ₀ , Y ₀ ). ΔY
Is similar to the calculation of ΔΧ. Correction amount (Δ
(Χ ₀ , ΔY ₀ ) can be calculated more accurately by actually measuring the correction amount and using an empirical formula. This correction amount is supplied from the electron beam exposure apparatus 34 to the Χ-Y stage controller 32 in the processing in step 62.
Is added to the target position coordinates (Χ ₀ , Y ₀ ) supplied to. (2) Second Embodiment In FIG. 1, moving mirrors 16 # and 16Y and a Χ-Y stage 1
When the movable mirrors 16 and 16Y are deformed to the extent not negligible with respect to the Χ-Y stage 10 due to thermal stress acting between 0 and 0, the position detection marks 361 to 369 are arranged on the Χ-Y stage 10 However, the above correction cannot be performed accurately. Therefore, in this embodiment, as shown in FIG. 4, five rectangular holes are formed at equal intervals in the upper end surface of the movable mirror 16 #, and position detecting marks 361 to 365 are fitted and adhered to the respective holes. . Other points are the same as those of the first embodiment.

[Brief description of the drawings]

1 to 3 relate to a first embodiment of an electron beam writing method and apparatus according to the present invention. FIG. 1 is an overall configuration diagram of an electron beam writing apparatus, and FIG. FIG. 3 is a main part configuration diagram of the electron beam exposure apparatus, showing a state in which a beam is being irradiated. FIG. FIG. 4 is a perspective view showing the arrangement of position detecting marks used in the electron beam writing apparatus of the second embodiment according to the present invention. FIG. 5 is an overall configuration diagram of a conventional electron beam drawing apparatus. In the figure, 10 is a Χ-Y stage 12 is a sample holder 14 is a semiconductor wafer 16Χ, 16Y is a moving mirror 18 is a laser interferometer 24 is a beam splitter 26Χ, 26Y is a Michelson interferometer 35 is an electron beam irradiation device 361 ~ 369 is a position detection mark 38 is an electron beam 40 is a secondary electron 42 is a detector

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 21/027

Claims (4)

(57) [Claims] A first reflector and a second reflector are fixed to the movable stage along one and the other sides of the movable stage adjacent to each other at right angles to each other, and laser light from a laser interferometer is applied to the movable stage. The position of the movable stage is detected by irradiating the first reflection plate and the second reflection plate, the movable stage is moved to a target position based on the detected position, and an electron beam is applied to a sample mounted on the movable stage. An electron beam writing method for writing a pattern by irradiating, wherein a plurality of position detection marks are fixed on the movable stage along each of the one and the other sides of the side, before starting electron beam exposure on the sample and After a lapse of a set time during electron beam exposure, each of the plurality of position detection marks is irradiated with the electron beam to detect secondary electrons emitted from an irradiation point, and process the secondary electron detection signal. Detecting the positions of the plurality of position detection marks, and correcting the movement amount of the movable stage by substantially correcting the target position based on the detected positions. . 2. A movable stage on which a first reflector and a second reflector are fixed along one and the other sides of mutually adjacent right angles, respectively, and a laser beam from a laser interferometer for the first reflection. A length measuring device that irradiates the plate and the second reflection plate to detect the position of the movable stage, and a stage control device that moves the movable stage to a target position based on the detected position.
An electron beam exposure apparatus (6) for irradiating a sample mounted on the movable stage with an electron beam to write a pattern, the electron beam exposure apparatus (6) comprising: the movable stage; A plurality of position detection marks are fixed along each of the following. The electron beam exposure apparatus detects a secondary electron emitted from an irradiation point when the position detection mark is irradiated with the electron beam. An electronic detector; mark position detecting means for processing the secondary electron detection signal to detect the position of the position detecting mark; and the target position based on the detected position for each of the plurality of position detecting marks. And a correction amount calculating means for calculating a correction amount for correcting the target position, wherein the target position is substantially corrected by the correction amount. 3. The laser interferometer (4) uses a Michelson interferometer, and both the first reflector and the second reflector are movable mirrors constituting the Michelson interferometer. 3. The device according to claim 2, wherein: 4. The apparatus according to claim 2, wherein said plurality of position detection marks are fixed to upper ends of both said first reflector and said second reflector.