JPH04303918A - Charged particle beam lithography apparatus - Google Patents

Abstract

PURPOSE:To always obtain an accurate irradiation amount by a method wherein the irradiation time is corrected by the difference between the effective irradiation time of a beam current and the set irradiation time. CONSTITUTION:A waveform is generated by using a pulse generator 20; it is fed to a signal driver 16. A blanking amplifier 13 turns on and off a beam so as to make it correspond to the said signal. A beam current is detected by using a current measuring instrument 10 by moving an X-Y stage 7 to a prescribed position and by impinging the beam on a Faraday cup 8. An error in the irradiation time can be found from a value t0 for the set irradiation time Ton in which an average beam current I has been extrapolated to I=0. When an irradiation amount D is set by using D=J-T0n, an error is caused and an effective irradiation amount Deff is Deff=j.(Ton-t0). The value t0 can be measured by an experimental data. In order to obtain a desired irradiation amount with high accuracy by correcting the error t0, the relationship of the value t0 or a value I-Ton is measured in advance as a blanking characteristic, it is stored in a register 22 for irradiation-time correction use and the irradiation time is corrected at a lithographic operation.

Description

[Detailed description of the invention]

[Object of the invention]

0002

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charged beam drawing apparatus for drawing an LSI pattern on a sample, and more particularly to a method for measuring effective irradiation time and an irradiation time correction apparatus using the same.

0003

2. Description of the Related Art In recent years, there has been a trend toward miniaturization of LSI devices, and devices with dimensions of 0.5 μm and even 0.25 μm are expected to appear in the near future. For this reason, it is becoming difficult to manufacture such miniaturized devices by the conventional method using an optical stepper, and a new lithography is desperately needed. Electron beam lithography is widely expected to be the most promising type of lithography.

Conventionally, the beam irradiation time Ton in this type of charged beam writing apparatus has been set by dividing the desired irradiation amount D by the current density J. That is, Ton=D
/J.

[0005]

[Problems to be Solved by the Invention] However, in the above-mentioned conventional charged beam lithography apparatus, there is a limit to the frequency characteristics of the blanking amplifier itself when turning the beam on and off, and the beam diameter at the blanking aperture position is limited. There was a problem that an error occurred in the irradiation time due to a delay in blanking due to the finite size of the image, and the drawing was not performed with the set irradiation amount. In particular, when using a high-sensitivity resist with a device capable of writing at high current density to improve throughput, the irradiation time becomes extremely short because writing can be done with a low dose.
This error cannot be ignored compared to the set irradiation time. However, if the irradiation dose is not set as specified, it will significantly affect the reliability of the γ value used for comparing and evaluating resists with different sensitivities, and there is a problem in that it will make rigorous evaluation of contrast characteristics difficult. Ta. Furthermore, when a correction method that changes the exposure time for each shot is adopted as a proximity effect correction method, due to the above-mentioned error, drawing is not performed according to the preset correction exposure time, and accurate proximity effect correction cannot be achieved. was there.

[0006] In view of the above-mentioned problems, the object of the present invention is to
The object of the present invention is to provide a charged beam drawing device that can obtain a desired beam irradiation amount with high precision.

[Configuration of the invention]

[0008]

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present invention generates a blanking signal corresponding to the irradiation time and non-irradiation time of the beam current in a charged beam lithography apparatus that draws an LSI pattern on a sample. The apparatus is equipped with an oscillator for correcting the irradiation time and an irradiation time correction register for correcting the irradiation time by determining the difference between the effective irradiation time of the beam current and the set irradiation time.

[0009]

[Operation] The present invention has an irradiation time correction register that corrects the irradiation time based on the difference between the effective irradiation time of the beam current and the set irradiation time, so it does not depend on the difference in sensitivity of the resist used to draw the LSI pattern. Accurate irradiation amount is always obtained. In other words, the irradiation amount during normal writing is determined by the product of the set irradiation time and the beam current density, but in actual writing, the amount equivalent to the blanking delay time relative to the set irradiation time is used. The beam is irradiated onto the sample while the beam is still insufficient. Therefore, by measuring the effective irradiation time during drawing in advance, and then correcting the irradiation time by finding the difference between the effective irradiation time and the set irradiation time, a stable drawing pattern can always be obtained.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the charged beam drawing apparatus of the present invention will be described with reference to FIGS. 1 to 4. That is, in FIG. 1, 1 is an electron optical lens barrel. A blanking deflector 4 for turning on and off the beam and a shaping deflector 5 for controlling the shape and dimensions of the beam are installed in the upper part of the electron optical lens barrel 1. Shaping apertures 2 and 3 for shaping the electron beam are arranged between the shaping deflector 5 and below the shaping deflector 5. Further, a deflector 6 for positioning the beam on the sample is provided below the shaping aperture 3, and an XY stage 7 is provided below the deflector 6. And X
- A Faraday cup 8 for measuring beam current is arranged on the Y stage 7. The Faraday cup 8 includes a preamplifier 9, a current measuring device 10, and a control computer 1.
1 are connected sequentially. 12 is an arithmetic control circuit to which the control computer 11 is connected; signal drivers 16 to 18 are connected to this arithmetic control circuit 12, respectively; a blanking amplifier 13 is connected between the signal driver 16 and the blanking deflector 4; is connected. Furthermore, a shaping deflection amplifier 14 is connected between the signal driver 17 and the shaping deflector 5, and a positioning deflection amplifier 15 is connected between the signal driver 18 and the deflector 6. 19 is a stage control system, and this stage control system 19 is connected between the control computer 11 and the electron optical lens barrel 1. 20 is a pulse generator that generates a waveform as shown in FIG. 2 and is connected in a circle with the signal driver 16. This pulse generator 20 is connected to the irradiation time setting register 21 to which the control computer 11 is connected, and the irradiation time correction register 21. and the register 22 for use.

Next, the operation of the charged beam lithography apparatus having such a configuration will be described.

First, by using the pulse generator 20, as shown in FIG.
A waveform shown in is generated and supplied to the signal driver 16. Here, in the figure, Ton is the beam on, that is, the set irradiation time, Toff is the beam off, that is, the set non-irradiation time, and T is the period, and T=Ton+Toff. Then, the blanking amplifier 13 turns the beam on and off in response to the signal. The beam current is detected by the current measuring device 10 by moving the X-Y stage 7 to a predetermined position to make the beam incident on the Faraday cup 8 . The current density of the beam is within a certain range (5 to 130 A/c in this example) depending on the operating point of the electron gun and the condenser lens.
m2) can be adjusted arbitrarily. For example, a case where the current density J=60 A/cm2 will be explained. The beam area at this time is set to S=1 μm2. Period T=
By changing Ton under the condition of 2 μs, the average beam current I
When measured, the results shown in solid line B in FIG. 3 are obtained. Broken line A
is an ideal I-Ton relationship. The error in the irradiation time is determined from the value to of Ton obtained by extrapolating I to I=0. In this example, to =120 ns. Therefore, if the irradiation amount D is set as D=J・Ton as in the past, an error will occur, and the effective irradiation amount Deff will be Deff = J・(
Ton-to). Also, Deff is Deff
= It can also be found from T・I/S. The cause of this error to is that the blanking waveform applied to the blanking deflector 4 as shown in FIG. The resulting blanking delay time is Δt2'-Δt1
) and the fact that the beam diameter at the blanking aperture position where the beam is actually cut off is a finite size (the error time caused by this is Δt3
). Therefore, to depends on J, which is a function of the shot period T and the beam diameter at the blanking aperture position, and t
o=|Δt2'-Δt1'|+Δt3. However, since it is extremely difficult to actually measure |Δt2 ′−Δt1 ′| and Δt3 , the method of determining to using the experimental data shown in FIG. 3 is optimal for measuring to . In order to correct this error to and obtain the desired dose with high precision, to or I-To should be set as a blanking characteristic in advance.
It is sufficient to measure the relationship between n and store it in the irradiation time correction register 22, and then correct the irradiation time at the time of drawing.

[0013]

As described above, according to the present invention, an accurate beam irradiation amount can always be obtained without depending on the difference in resist sensitivity, and a stable drawing pattern can be formed.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a device according to the invention.

FIG. 2 is an explanatory diagram of a blanking signal having waveforms corresponding to irradiation time and non-irradiation time.

FIG. 3 is a relationship diagram of I-Ton.

FIG. 4 is a diagram showing frequency characteristics of a blanking amplifier.

[Explanation of symbols]

1 Electron optical lens barrel 2, 3 Molding aperture 4 Blanking deflector 5 Molded deflector 6 Deflector 7　X-Y stage 8 Faraday Cup 9 Preamplifier 10 Current measuring device 11 Control computer 12 Arithmetic control circuit 13 Blanking amplifier 14 Molded deflection amplifier 15 Positioning deflection amplifier 16-18 Signal driver 19 Stage control system 20 Pulse generator 21 Irradiation time setting register 22 Irradiation time correction register

Claims (1)

[Claims] 1. A charged beam lithography device that draws an LSI pattern on a sample, comprising: an oscillator that generates a blanking signal corresponding to a beam current irradiation time and a non-irradiation time; and an effective irradiation time and a set irradiation time of the beam current. A charged beam lithography apparatus comprising: an irradiation time correction register that corrects the irradiation time by determining the difference between the irradiation times and the irradiation time.