JP2901246B2 - Charged particle beam exposure system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] Regarding charged particle beam exposure equipment such as electron beam exposure equipment, uniform exposure can be performed stably, at high speed and with high accuracy for drawing ultra-fine patterns with a rule of about 0.2 to 0.3 μm or less. In a charged particle beam exposure apparatus for exposing a charged particle on an object on a stage, a charged particle beam generating means for generating a charged particle beam, and a blanking electrode are provided. A plurality of apertures respectively provided are arranged in a line,
A blanking aperture array that allows the charged particle beam to pass, and the blanking electrodes of each aperture are turned on and off independently, and are turned on so that the product of the intensity of the charged particle beam and the on time of the blanking electrode is constant. And a blanking electrode driving means for causing the image forming apparatus to have a blanking electrode driving means.

[Industrial applications]

The present invention relates to a charged particle beam exposure apparatus such as an electron beam exposure apparatus.

[Conventional technology]

In recent years, direct exposure of LSI by electron beam exposure, that is, exposure has been widely performed without using a mask, but there are many variable rectangular beams, and there are also point beams or fixed rectangular beams. The latter two are generally for research use.

As shown in FIG. 9, the variable rectangular beam exposure apparatus comprises an electron gun 1, two masks 2, 3 having a rectangular aperture,
Beam size deflection electrode 4 for changing the cross-sectional area of a rectangular beam by deflecting an electron beam, main deflection lens (coil)
5. A sub-deflection lens (electrode) 6 for irradiating a rectangular beam of an arbitrary size to a target such as a wafer placed on a sample stage 7. A control unit that controls these generates a CPU 10, a magnetic disk 11 for storing data, a magnetic tape 12, an interface 13, a data memory 14, and decomposes the pattern into rectangular patterns to generate size information and positional information of each rectangular pattern. It comprises a pattern generation circuit (shot decomposition) 15, a pattern correction circuit 16 for performing main correction, and a driver (DAC / AM) for driving the beam size deflection electrode 4, the main deflection coil 5, and the sub deflection electrode 6.
P) 17, 18, 19, and a stage control unit 21 for controlling a motor 20 for moving the sample stage 7.

That is, in the rectangular beam exposure, as shown in FIG. 10, the data transferred from the magnetic disk 11 or the magnetic tape 12 to the data memory 14 corresponds to the entire main field. This main field is divided into a plurality of subfields, and the pattern of each subfield is further divided into a plurality of shots (rectangular patterns). At this time, the electron beam movement between each subfield in the main field is performed by the main deflection coil 5, and the electron beam movement between each rectangular pattern in the subfield is performed by the sub deflection electrode 6, and the size of the rectangular pattern is changed. Is adjusted by the beam size deflection electrode 4.

[Problems to be solved by the invention]

However, as LSI miniaturization progresses, especially
For a 0.3 μm rule LSI, rectangular beam exposure has the following problems.

1) There is an upper limit on the current density of the rectangular beam that can be used.

2) Drivers (DA) for main deflection, sub deflection, and beam size deflection are used to write LSI patterns with a large number of shots.
The number of adjustments of C / AMP increases, and therefore the waiting time for the adjustment increases and takes too much time.

Therefore, the variable rectangular beam is no longer suitable for mass production of fine patterns of 0.2 to 0.3 μm.

Further, 3) The 0.2-0.3 μm rectangular beam has no difference from the point beam, and has no merit of the variable rectangular beam.

4) In the case of a 0.1 to 0.2 μm beam, the dose is relatively unstable with a small beam because the beam is formed by overlapping apertures of two masks 2 and 3.

Accordingly, an object of the present invention is to provide a charged particle beam exposure apparatus that enables uniform, stable, high-speed, and high-precision exposure for depiction of an ultrafine pattern having a rule of about 0.2 to 0.3 μm or less. .

[Means for solving the problem]

The means for solving the above-mentioned problem is shown in FIG. That is, in a charged particle beam exposure apparatus for exposing charged objects on an object on a stage, a charged particle beam generating means generates a charged particle beam, and the charged particle beam passes through a blanking aperture array. In the blanking aperture array, a plurality of apertures each provided with a blanking electrode are arranged in a line. The blanking electrodes of these apertures are independently turned on and off by blanking electrode driving means.

[Action]

The operation of the above means is shown in FIG. That is, the charged particle beam that has passed through the apertures arranged in a line in the blanking aperture array is divided into a number of small beams (line beams). For example, the line beam is deflected at right angles to the stage movement direction, and with this movement, the blanking electrodes of each aperture are turned on and off independently. At that time, the product of the intensity of the charged particle beam and the on time of the blanking electrodes is turned on. Is driven to be constant. In FIG. 2, for example, blanking electrodes a-a ', b-
A blanking signal is generated for b ', cc', dd 'as shown, and the beam is turned on and off.

〔Example〕

FIG. 3 is a view showing one embodiment of a charged particle beam exposure apparatus according to the present invention. In FIG. 3, 30 is the cathode 3
1, an electron gun consisting of a grid 32 and an anode 33,
The beam emitted from the cathode 31 forms a crossover image between the grid 32 and the anode 33. This crossover image is magnified by the crossover magnifying lens. In the crossover magnifying lens 34, a quadrupole beam collapsing lens 35, a limiting aperture 36, and an alignment coil 37 are provided. The quadrupole beam crushing lens 35
For example, a magnetic lens and an electrostatic lens shown in FIGS. As a result, the crushed crossover image 38
Are imaged on the blanking aperture array 39. When the electron gun 30 itself generates a crushed crossover beam, the quadrupole beam crushing lens 35 is unnecessary.

5μ □ × 256 for blanking aperture array 39
Number of apertures 39 _{0-39 255} are arranged in a so-called harmonica-shaped in a line. The blanking aperture array 39 is made of, for example, silicon single crystal, an aperture is formed in the single crystal by trench etching, and an electrode is formed on the inner wall. The blanking aperture array 39 is provided in the converging lens 40. Note that the apertures may be arranged in two rows.

41 is a large blanker which turns on and off the entire beam. When no electric field is applied to the large blanker 41, the on-beam 41a that has passed through a portion of the blanking aperture array where no voltage difference is applied between the electrodes passes through the blanking aperture 43 via the reduction lens. On the other hand, the off-beam 41 passing through a portion of the blanking aperture array where a voltage difference is applied between the electrodes
b is blocked by the blanking aperture 43 after passing through the reduction lens. Conversely, when an electric field is applied to the large blanker 41, the blanking aperture array 39
Regardless of the state of the individual electrodes of
Blocked by blanking aperture.

The reduction lens 42 transmits the beam that has passed through the blanking aperture 43 together with the reduction lens 44 and the immersion type lens 50 onto a continuously moving stage 51 on a wafer 53 that is attracted by an electrostatic chuck 52 to a 1/500 blanking aperture array 39. Is formed as a reduced image of the aperture.

In the reduction lens 44, a refocus coil 45 is provided. The refocus coil 45 corrects beam blur due to Coulomb interaction by flowing a refocus current determined by the total number of cells in which the aperture of the blanking aperture array 39 is on.

Reference numeral 46 denotes a horizontal scanning deflector, which is a continuously moving stage 51.
The beam is scanned in a direction perpendicular to the movement of the beam. In addition, dynamic focus coil 47, dynamic stig coil
Numeral 48 corrects beam deflection blur in the horizontal scanning.

Reference numeral 49 denotes an 8-pole deflector for stage feedback, which performs deflection distortion correction, continuous movement feedback of the stage 51, and speed correction.

The continuous movement stage 51 is provided in the immersion type lens 50 in order to increase the resolution.

FIG. 5 is a block circuit diagram of a control unit for controlling the main parts of FIG. 3, and the same reference numerals are given to the same components as those of FIG. That is, instead of the pattern generation circuit 15, the pattern correction circuit 16, and the drivers (DAC / AMP) 17, 18, and 19 shown in FIG. 9, a bit map generation circuit 61, a blanking generation circuit 62, a sequence controller 63, a blanking control A circuit 64, a deflection control circuit 65, drivers (DAC / AMP) 66, 67, and a laser interferometer 68 are provided.

The bit map generation circuit 61 reads information (256 bits) for each line beam from the data memory 14 and sends it to the blanking generation circuit 62. As a result, the electrodes of each of the apertures 39 _{0 to} 39 ₂₅₅ of the blanking aperture array 39 are turned on and off independently. The intensity I _i of the beam passing through each aperture to different by location, different on-time tau ₀ for each cell, tau _1, ..., tau ₂₅₅ circuit 62 _0, 62 _1,
…, 62 ₂₅₅ are set. This will be described later.

The blanking control circuit 64 is a sequence controller
The circuits 62 ₀ , 62 ₁ ,..., 62 ₂₅₅ of the blanking generation circuit 62 are started at timing based on the 63 command signals.

The deflection control circuit 65 is a driver based on the horizontal coordinates of the line beam information generated by the bitmap generation circuit 61.
The horizontal scanning deflector 46 is driven by 66. In this case, the sample stage (stage) 51 is continuously moved by the stage control unit 21. Therefore, it is necessary to feedback correct the position of the line beam accompanying the continuous movement of the stage 51. For this reason, the deflection control circuit 65 uses a laser interferometer.
The octupole deflector 49 is driven so that the difference between the position of the stage 51 detected by 68 and the target position becomes zero. That is, as shown in FIG. 6, the deflection control circuit 65 includes a register 651 for storing the target position (X, Y) from the sequence controller 63 and position information (X ′,
A difference calculator 652 for calculating the difference between Y ′) and the register 61 is provided, and the 8-pole deflector 49 is controlled by the difference. As a result, the stage error is fed back at high speed. Note that the eight-pole deflector 49 actually adjusts the two-dimensional position of the beam, but in FIGS. 5 and 6, for simplicity of description, the eight-pole deflector is shown as one-dimensional. is there.

Further, the blanking generation circuit 62 shown in FIG. 5 will be described with reference to FIGS. 7 and 8.

In other words, the beam crushes the crossover in a line in the critical irradiation of the crossover image,
The beam intensities I ₀ , I ₁ ,..., I at the respective apertures (cells) 39 _{0 to} 39 ₂₅₅ of the blanking aperture array 39
_{In the case of 255} , as shown in FIG. 7 (A), only 80-90% uniformity can be obtained. Therefore, as shown in FIG. 7B, the beam-on pulse lengths τ ₀ , τ _{1 ,.}
Are determined in inverse proportion to the beam intensities I ₀ , I ₁ ,..., I _{255 in} FIG. 7 (A). That is, τ _i × I _i = constant. As a result, the dose N of each line beam becomes constant as shown in FIG. 7 (C).
For this reason, each circuit 62 _i of the blanking generation circuit 62
It is configured as shown in the figure.

In FIG. 8, 621 is a register for storing the beam-on pulse length τ _i , 622 is a down counter, 623 is an AND circuit,
624 is a flip-flop and 625 is a driver. That is, when the data from the bitmap generation circuit 61 is “1” and a start pulse is input from the blanking control circuit 64, the flip-flop 624 is set via the AND circuit 623 and the output thereof is pulse drives rise, the corresponding blanking electrode 39 _i. At the same time,
The starting pulse from the blanking control circuit 54 is stored in the register 62
The value τ _i of 1 is set in the down counter 622. The down counter 622 counts down the high-speed clock signal CLK and decreases its value.

When the value of the down counter 622 becomes 0, in other words, when the time corresponding to τ _i elapses, the down counter 6
22 generates a carry signal, which is
Act as a reset signal for As a result, flip-flop 624 is reset driving of the blanking electrode 39 _i is turned off. Of course, when the data of the bit map generation circuit 61 is “0”, the flip-flop 624 is not set, and no drive pulse τ _i is generated.

Thus, each circuit 62 _i according to the data of the bit map generator 61 generates a drive pulse of time corresponding to the predetermined tau _i. Note that the value τ _{i of the} register 621 can be set in advance, or can be changed by the CPU 10 as needed.

Than arrangement described above, for example, 0.1 [mu] m □ beam 256 side by side, the current density of 200A / cm ^2, was irradiated with shot time of 25ns in the resist to each point of the sensitivity of ^{5μC / cm 2, (40MHz)} 2
The scanning area of mm width was continuously moved at 50 mm / s, and an exposure speed of 1 cm ² / s was obtained.

〔The invention's effect〕

As described above, according to the present invention, stable, high-speed, and high-precision uniform exposure can be performed even in the depiction of an LSI that is ultrafine and has a rule of about 0.2 μm, for example.

[Brief description of the drawings]

FIG. 1 is a view showing the principle configuration of the present invention, FIG. 2 is a view for explaining the operation of the present invention, FIG. 3 is a view showing one embodiment of a charged particle beam exposure apparatus according to the present invention, FIG. Is a diagram showing an example of the quadrupole beam crushing lens of FIG. 3, FIG. 5 is a block circuit diagram showing a control unit of the apparatus of FIG. 3, FIG. 6 is a circuit diagram of a deflection control circuit of FIG. FIG. 7 shows the beam intensity, beam on pulse length, and beam intensity of each aperture (cell) of the blanking aperture array of FIG.
FIG. 8 is a circuit diagram of the blanking generation circuit of FIG. 5, FIG. 9 is a diagram showing a conventional variable rectangular electron beam exposure apparatus, and FIG. 10 is a diagram for explaining rectangular beam exposure. is there. 35: 4-pole beam crushing lens, 39: blanking aperture array, 46: horizontal scanning deflector, 49: 8-pole deflector, 62: blanking generation circuit, 68: laser interferometer.

Continuation of the front page (56) References JP-A-53-117387 (JP, A) JP-A-62-118526 (JP, A) JP-A-61-42128 (JP, A) JP-A-59-22325 (JP) , A)

Claims (2)

(57) [Claims] 1. A charged particle beam generating means for generating a charged particle beam, a blanking aperture array provided with blanking electrodes, and a plurality of apertures for passing the charged particle beam are arranged; The electrodes are independently turned on and off, and the product of the intensity of the charged particle beam passing through the aperture and the ON time of the blanking electrode of the aperture is constant for all apertures that have turned on the blanking electrode. And a blanking electrode driving means for controlling the ON time of each of the blanking electrodes. 2. A beam collapsing lens for collapsing a crossover image of said charged particle beam generated by said charged particle beam generator in a line shape and irradiating all apertures of said blanking aperture array. The charged particle beam exposure apparatus according to claim 1, wherein: