JP3597440B2 - Electron beam drawing method and apparatus - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to an electron beam lithography method, and more particularly to an electron beam lithography method suitable for drawing a fine line over a large area and an apparatus for implementing the method.
[0002]
[Prior art]
Many electronic devices are formed by forming a fine pattern on the surface of a substrate made of a semiconductor or an acoustic functional material. Processing such as injection, diffusion, and coating of a metal, an insulator, or an impurity is performed at a desired position of the pattern. In recent years, such microfabrication techniques have made patterns that can be produced extremely fine, and the behavior of electrons has reached the point of handling a quantum well structure exhibiting a quantum effect. Fabrication of a fine pattern in such a region of several tens of nanometers can be achieved only by electron beam drawing.
[0003]
As is well known, in electron beam lithography, a very fine spot is formed with an electron beam, and a necessary mask pattern is formed by performing so-called electron beam exposure in which the spot is applied to a substrate or a predetermined resist film. However, in the case where the fine beam is swept over a wide range on the sample surface to form a positionally precise pattern, the maximum sweep range is limited. In particular, when the position of the electron beam deviates from the optical axis of the electron beam focusing lens system or the electron beam deflecting system, a so-called off-axis aberration occurs, and the aberration increases rapidly as the deviation from the optical axis increases. This aberration not only distorts the irradiation position on the sample surface, but also distorts the size of the electron beam focusing point.The electron beam deviates from the optical axis, and the focusing point is greatly blurred. Also give.
[0004]
Therefore, in the case of producing a relatively wide range of patterns in electron beam lithography, one irradiation range (hereinafter, referred to as a field) is set to, for example, a square of a specific size, whether raster scanning or vector scanning. These fields are connected in order to form a pattern of the required size (for example, see Wei Tokuyama, "Ultra-fine processing technology" (Applied Physics Series), Ohmsha, published February 25, 1997) . Here, pattern formation by a generally adopted joining method will be described with reference to FIG.
[0005]
As shown in FIG. 1a, n × m fields A _ij (i = 1, 2,..., N; j = 1, 2,..., M) are arranged on the sample 10 without gaps. To do this, the sample stage (not shown) on which the sample 10 is placed is sequentially moved so that the adjacent fields just touch each other. Pattern passes through the boundary α of such two fields, for example as shown in 1b, the field A22, A23 line trajectory _{L 20} and field A23 side on a line connecting the centers C22 and C23 of the field A22 side of the line since partial path L ₂₁ has little or extremely small shift caused in the vertical direction (direction of the border line BC), it can be drawn as a single line coalesce at point B _0. However, since the off-axis aberration is not completely symmetrical with respect to the center of the optical axis (C ₂₃ , C ₂₂ ) above the boundary line BC, the line segments L ₁₀ and L ₁₁ are formed at the positions indicated by the points B ₁ and B ₁ ′. And a shift B ₁ B ₁ ′ occurs in the vertical direction.
[0006]
The highest-performance electron beam lithography systems currently on the market are equipped with auxiliary devices that compensate for off-axis aberrations. Does not give any noticeable mismatch in the pattern. However, when the sample stage is moved, a considerable amount of time is required for preliminary adjustment of the irradiation system and the drive unit of the movable stage, for example, the preparation of the identification mark position measurement and position setting.
[0007]
On the other hand, when a line segment having a width of about 10 nm, such as a quantum wire, is drawn over a wide area on the sample surface, as described above, the influence of off-axis aberration in the submicron region is compensated for. Even so, a compensator has not been completed to such an extent that a displacement in the nanometer range can be removed. In order to make the influence of the shift negligible, it is necessary to reduce the shift to at least about 1 nm. In addition, the shape of the convergence point is not usually circular, but becomes a meteor or irregular shape. Such "blur" of the focal point of the electron beam cannot be sufficiently corrected near the boundary.
[0008]
A typical example of a pattern created to know the one-dimensional behavior of electrons in a fine wire structure is shown in FIG. 2a. Electrodes E ₁ , E ₂ , E ₃ are provided on the sample surface, and linear thin lines L ₁ and L ₂ having a width of about 10 nm are formed between the electrodes E ₁ and E ₂ or E ₃ . Further, a similar fine wire structure has a curve L ₃ between the electrodes G ₁ , G ₂ , G ₃ as shown in FIG. 2B, and a connection point (node) between the fine wires L ₄ , L ₅ , L _6. Those containing K are also conceivable. The electrode itself has a size of about 500 μm × 500 μm, and the length of the fine wire is set to several mm to several tens of mm. Since the field to be used is 10 μm × 10 μm to 1000 μm × 1000 μm in the case of a normal electron beam lithography apparatus, if the above-described joining method is used to produce a thin line having the above length, it takes several tens of times or It is necessary to join the fields about 100 times. However, as described in detail above, a large shift (lateral shift) or blur (expansion of the focusing point of the electron beam) already occurs at the boundary of the field at the time of one connection. Doing so results in a pattern that cannot be used.
[0009]
It is necessary to keep the electron exposure reaction between the electron beam and the resist constant at all times. The speed of an electron beam moving on a fine line during drawing is relatively slow. For example, in the case of a substrate coated with Zeon 520 manufactured by Zeon as a resist material at a thickness of 0.15 μm, if the acceleration voltage of the electron beam is 20 kV and the beam current is 10 pA, the resist is electronically exposed. The speed of the electron beam suitable for this is 1.5 mm / s on the sample surface. It is necessary to be able to maintain such a constant speed regardless of the shape of the figure, that is, whether the figure pattern is a straight line or a curve.
[0010]
[Problems to be solved by the invention]
SUMMARY OF THE INVENTION An object of the present invention is to provide an electron beam drawing method capable of drawing an extremely thin line segment without causing a shift of a line segment or a shift of a focal point caused by a field joining method, and an apparatus capable of performing the method. .
[0011]
[Means for Solving the Problems]
According to the present invention, there is provided an electron beam drawing method for drawing a predetermined figure pattern by applying an electron beam to a surface of a sample using an electron beam focusing and sweeping apparatus including an electron beam focusing system and a deflection system, The following process,
-Control the focusing system so that the electron beam is always focused on a specific location on the sample surface on the sample stage while the sample is stationary,
Moving the sample stage so that the electron beam moves on the surface of the sample under the control state of the focusing system and draws the figure pattern,
・ Measure the actual position of the sample stage at that time,
Calculating a deviation between the target position of the sample table corresponding to the graphic pattern and the actual position,
Deflecting the electron beam on the sample surface using a deflecting system so that the above deviation is always zero,
Has been solved.
[0012]
Further, according to the present invention, there is provided an electron beam writing apparatus which draws a predetermined figure pattern by applying an electron beam to a surface of a sample using an electron beam focusing and sweeping apparatus including an electron beam focusing system and a deflection system. hand,
A sample stage 20 on which a sample is placed;
· Two directions X perpendicular to the sample stage 20, feeder M _X moved in Y, and M _Y,
A storage 32 for storing a control program for controlling the electron beam and the sample stage (20) for performing the method of claim 1 or 2;
The problem is solved by including the arithmetic processing unit 30 for performing the electron beam drawing processing according to the program.
[0013]
Other advantageous configurations according to the invention are set out in the dependent claims.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an electron beam drawing method and apparatus according to the present invention will be described in detail with reference to the drawings.
[0015]
FIG. 3 shows the arrangement of the main functional elements of the device according to the invention. For example, a sample 10 of a substrate coated with an electron beam resist is fixed on a sample moving table 20. Two directions X this is the sample moving stage 20 which are perpendicular to each other the sample moving stage 20 relative to the base (not shown), two feeder respectively are moved relative to the Y M _X, and M _Y, relative at that time two position detector S _X for measuring the amount of _movement, and the S _Y is equipped.
[0016]
Distance signal generating circuit 50 is a position detector S _X, calculates the amount of relative movement at that time from the detection signal of S _Y, delivered to the central processing unit 30 with a math function. The central processing unit 30 has a built-in storage unit 32 for pre-programming and storing pattern figures. Further, the central processing unit 30 is connected to an input / output / display unit capable of inputting a numerical value of a pattern trajectory, a control signal, and the like, and printing or displaying the result on a display. The central processing unit 30 in accordance with the desired trajectory that is stored in the storage unit 32 sends apparatus _M X, the drive circuit _DR X for _{M Y,} sends a drive signal to the DR _Y, according to the operation of the feed device _M X, _{M Y} The mobile platform 20 is moved to a designated position. In that case, the position detector S _X, a feedback circuit such as to match the actual trajectory and the target trajectory Motoma' by S _Y and the distance signal generator circuit 50 is formed by the central processing unit 30.
[0017]
Further, the central processing unit 30 is provided with an electron beam sweeping device 80 having a function of a scanning electron microscope for generating and sweeping an electron beam. Although the description of the device itself is omitted, only the deflection coil SC and the blanking unit BLK, which are important in the present invention, are schematically shown. The central processing unit 30 sends a drive signal for deflecting the electron beam to the deflection coil SC via the deflection drive circuit 60 in accordance with the graphic program of the target trajectory to be drawn stored in the storage unit 32 in the central processing unit 30, A blanking drive signal is sent to the blanking unit BLK via the blanking drive circuit 70 to determine whether the sample is irradiated with an electron beam.
[0018]
According to the present invention, when the graphic pattern is relatively simple and the scanning area is relatively large, the electron beam is narrowed by the objective lens LN as shown in FIG. while keeping standing at the position P _B of the surface of the sample 10, to move the sample stage 20 resting the sample 10, for example, in the required direction of arrow AA. The situation at this time will be described with reference to FIG. Feeder M _X, moving the sample 10 along the target locus TR ₀ specified by the central processing unit 30 in the direction of arrow AA by using the M _Y, and hatching the surface of the sample 10 by electron beam irradiation pattern _{L a} occurs. When the time of irradiating now to _{t 0,} the pattern _{L a} on the right are those irradiated to the point _{t 0} previous example time _{t 1 (t 1> t 0} ).
[0019]
In practice, device M _X central processing unit 30 _sends, be driven M _Y to the target locus as programmed, deviation δ is generated between the actual moving position and the position specified by various circumstances. The actual position TR ₁ is position detector S _X, is detected by the S _Y, is calculated as an absolute position relative to a reference position of the system at a distance signal generation circuit 50 based on the detection signal (e.g., the optical axis of the focusing lens system). The central processing unit 30 calculates a deviation δ between the target position TR ₀ and the actual position TR ₁ , and sends a deflection drive signal to the deflection coil SC so that the deviation δ is always zero during the sweeping, and sends an electron beam irradiation position. Is corrected. Since the response speed of the position detection system and an electron beam deflection system is faster than the response speed of the feed device M _X, M _Y, it is possible to draw a trajectory and practically always deviation [delta] = 0 by the feedback control described above. Although convenience deviation δ description has been given only by component perpendicular to the tangential direction of the target locus TR _0, in practice also includes tangential component.
[0020]
Feeder M _X, M _Y a mechanical motor capable of electrically tweak the motion, for example, a stepping motor has been widely or resonant to use mechanical resonance ultrasonic motor (for example, Japanese Unexamined Patent Publication No. 11-15530, Publication) or a non-resonant ultrasonic motor (for example, Japanese Patent Publication No. 3-81119) that generates an electric stress by a piezoelectric element and converts it into a movement amount.
[0021]
The position detectors S _{X and} S _Y depend on the required fineness of the pattern. When writing a pattern in the range of 10 nm, a laser interferometer that guarantees a position resolution of at least 1 nm should be used. is there. For writing in the submicron range, a photoelectric incremental linear encoder or the like can be used.
[0022]
If the method of the present invention is introduced as a device to be added to an electron beam lithography device that performs a normal drawing process so as not to sacrifice the function of a scanning microscope, it can be implemented by a program process of an arithmetic process for causing an electron beam to follow a target trajectory. It can be realized without major modifications or changes. In any case, in addition to drawing in the nanometer region, a drawing process using a field joining method of a normal pattern can be executed when necessary.
[0023]
Aiming to draw an electron beam in the 10 nm area, the selection of the material and thickness of the resist of the sample, the material of the base (substrate) on which the resist is applied, the acceleration voltage of electrons, the irradiation current density, the brightness of the electron gun, etc. Careful consideration is needed. According to the present invention, it is necessary to irradiate the sample surface with the electron beam focused to 10 nm or less. For this purpose, the irradiation position is selected so that the focused position of the electron beam on the sample surface is on the optical axis of the objective lens LN, and the working beam is irradiated with the working distance as short as possible. Under such focusing and deflection conditions, the allowable range of the field A is necessarily narrowed. Therefore, if the conventional field joining method is followed, the number of joining times increases significantly and the processing time increases. However, since the present invention does not employ the joining of fields, the working distance, in other words, the distance between the objective lens LN and the sample surface can be sufficiently reduced. Such a treatment reduces the influence of the external electromagnetic field of the electron beam between the objective lens LN and the sample surface, and at the same time, the deflection of the electron beam (substantially the focusing point of the electron beam due to the shielding action of the objective lens LN due to the leakage magnetic field). This also has the advantage of significantly reducing blurring).
[0024]
【The invention's effect】
As described above, the electron beam drawing method and apparatus according to the present invention can draw extremely thin line segments that do not cause line segment shift or focus point shift caused by the field joining method. In particular, in an electron beam lithography apparatus already equipped with a feeder and a position detector, the present invention can be easily realized in accordance with the program of the central processing unit.
[Brief description of the drawings]
FIG. 1 is a schematic diagram illustrating electron beam drawing by a field joining method, (a) a diagram showing an overall arrangement, (b) a diagram enlarging a boundary,
FIG. 2 is a drawing showing two typical figures in electron beam drawing;
FIG. 3 is a block diagram showing a main functional configuration of the electron beam drawing apparatus;
FIGS. 4A and 4B are a schematic diagram illustrating an arrangement for irradiating an electron beam and a schematic diagram illustrating correction of a sweep locus.
[Explanation of symbols]
Reference Signs List 10 Sample 20 Sample stage 30 Central processing unit 32 Storage unit 80 Electron beam sweeper A Field B Connection point C Center of field L Drawing trajectory E, G Electrode S _X, S _Y position detector M _X, M _Y feeder

Claims (7)

In an electron beam drawing method of drawing a predetermined figure pattern by applying an electron beam to the surface of a sample using an electron beam focusing and sweeping apparatus including an electron beam focusing system and a deflection system, the following steps
-Control the focusing system so that the electron beam is always focused on a specific location on the sample surface on the sample stage while the sample is stationary,
Moving the sample stage so that the electron beam moves on the surface of the sample under the control state of the focusing system and draws the figure pattern,
・ Measure the actual position of the sample stage at that time,
Calculating a deviation between the target position of the sample table corresponding to the graphic pattern and the actual position,
Deflecting the electron beam on the sample surface using a deflecting system so that the above deviation is always zero,
Electron beam drawing method characterized by performing. 2. The electron beam drawing method according to claim 1, wherein the focusing position of the electron beam is selected on the optical axis of the objective lens, and the electron beam is drawn at a position where the working distance of the sample stage is as short as possible. In an electron beam drawing apparatus that draws a predetermined figure pattern by applying an electron beam to the surface of a sample using an electron beam focusing and sweeping apparatus including an electron beam focusing system and a deflection system,
A sample stage (20) on which the sample (10) is placed;
A feed device (M _X , M _Y ) for moving the sample stage (20) in two orthogonal directions X and Y;
A storage (32) for storing a control program for controlling the electron beam and the sample stage (20) for performing the method of claim 1 or 2;
An electron beam lithography apparatus comprising: an arithmetic processing unit (30) for performing an electron beam lithography process according to the program. The electron beam lithography apparatus according to claim 3, wherein the feeding device (M _X , M _Y ) is a stepping motor. The electron beam lithography apparatus according to claim 3, wherein the feed device (MX _{, MY} ) is a resonance type ultrasonic motor or a non-resonance type ultrasonic motor. The electron beam lithography apparatus according to claim 3, wherein the feeding device (MX _{, MY} ) is a non-resonant ultrasonic motor. The electron beam lithography apparatus according to any one of claims 3 to 6, wherein the position detector (SX _{, SY} ) is a laser interferometer.

Images