JPS63246818A - Charged particle beam lithography and device therefor - Google Patents

Abstract

PURPOSE:To perform lithography at high speed under critical conditions not to cause uneven ness in the lithography due to a temperature rise of a resist so as to grasp conditions of a wafer surface in real time at the time of lithography, by mounting an infrared temperature detector on the charged particle beam lithography device for detecting a temperature of the sample surface during the lithography. CONSTITUTION:A lithography control circuit 17 performs a movement of a sample table 10 and control of a beam by the lithography data sent from a computer to lithograph a pattern on a sample while an infrared temperature detector 9 constantly measures a resist temperature of the sample for sending a temperature signal to the lithography control circuit 17. An upper limit of a resist temperature which enables lithography is set at the prescribed value in the lithography control circuit 17 according to resist sensitivity characteristics and the value of temperature rise of an irradiation part. The lithography control circuit stops lithography when a temperature signal attains the prescribed value and reopens the lithography when the temperature signal becomes under the prescribed value. Otherwise, the lithography is changed over to the lithography method having low temperature rise even it takes time. In this way, a measurement according to temperature rise of the resist is taken by detecting temperature in real time thus enabling the lithography having a little loss time and a short lithography time while preventing uneven sensitiveness due to temperature rise.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention provides a charged beam lithography system that can prevent uneven development due to resist deformation caused by temperature rise during lithography. The present invention relates to a drawing method and an apparatus thereof.

(Prior Art) A charged beam drawing device is a device that draws a pattern of an integrated circuit by irradiating a charged beam onto a substrate coated with a resist (photosensitive agent). Recently, high-dose devices with increased beam current and accelerating voltage have been developed to shorten writing time and improve resolution.

However, due to the resist temperature rising due to the high dose, sensitivity unevenness occurred, resulting in a defect in which the drawn pattern became uneven after development. Until now, in order to suppress the temperature rise of the resist, irradiation with a reduced dose of beam was performed intermittently to allow time for heat dissipation. Conventionally, trial drawing was performed using these measures, and after confirming that there was no unevenness after development, actual drawing was performed.

Furthermore, even when drawing conditions are determined from previous data to prevent temperature rise, the settings are often made with a safety factor in mind, resulting in a lot of lost time. In addition, the drawing pattern is dense and sparse, and even if drawn at high speed in the sparse areas, the temperature of the resist does not rise to the point where sensitivity becomes uneven. Conventionally, countermeasures have been taken to uniformly reduce the dose and provide heat dissipation time. was. There are also other differences depending on the drawing position.

Since the drawing range is a 5-inch angular radius, the surface temperature of the board will be different even for the same pattern at the start of drawing, the center, and the area near the end of drawing, and the heat dissipation situation will also change, so take measures to prevent uneven sensitivity. The amount taken should be different, but in the past, there was no way to grasp the situation during drawing, so a uniform correction was sufficient. As a result, there was a loss of time and unevenness occurred in some parts. In other words, the temperature rise of the resist was
XB is the range in which the beam can be deflected, and CxD is the maximum beam dimension. A shaped beam and vector scan type drawing device can arbitrarily deflect the beam to a desired location within AxB to perform drawing. However, in reality, the pattern data is output sequentially from the end, so it is drawn as shown by the arrow in FIG. Therefore, if the temperature rise in the shaded area is high or the reaction rate is high, unevenness will occur even if the same dose is used. The shaded areas in FIG. 8 were highly sensitive to light, and the resist was dissolved and blown off after development (the resist was positive type PMMA).

(Problems to be Solved by the Invention) The present invention provides a method and apparatus that can perform high-speed writing and grasp the wafer surface during writing in real time under the limit conditions that do not cause uneven writing due to resist temperature rise. It is.

[Structure of the invention]

(Means for Solving the Problems) One configuration of the present invention is that an infrared temperature detector for detecting the temperature of the surface of a sample during drawing is attached to a charged beam drawing apparatus. FIG. 1 shows an example of the configuration of the present invention. An infrared temperature detector (9) is attached near the sample surface α [being drawn. The infrared temperature detector (9) consists of an optical system (lens, etc.), an infrared detection element (for example, a photodiode), etc., and converts the infrared rays emitted from the surface of the resist a2, which is the sample being drawn, into an electrical signal. The electrical signal is led out of the sample chamber αυ by a signal line, and the necessary signal is amplified by an amplifier or bandpass filter (119), and the temperature of the detection section is output as an electrical signal. Figure 2 shows the configuration of the detection section. For example, the infrared rays generated from a part of the sample ao are collected by the lens αa and applied to the infrared detection element a9 to be converted into an electrical signal.The filter You can also add .

The output of the detection element αS is converted into a temperature signal by a circuit αe such as an amplifier and a filter outside the sample chamber, and is output.

Further, a means for detecting infrared rays caused by the overheating of the resist, converting the infrared rays into electric signals, and processing the signals will be described below. Figure 5 shows an example of this (this part of the circuit is quoted from Sangyo Tosho ■ P2S5, authored by Otori Gen), where the drawing data is once stored in the high-speed large-capacity puffer memory AL. High-speed data controller system 4 through high-speed data transfer controller (a)
The conventional configuration was to send the data as is. In the present invention, a data select buffer circuit 4 is provided between them.

The data select buffer circuit is a drawing method that has a selector that sorts data by drawing position and a data buffer (memory) for each classified drawing position.

(Function) In the apparatus of the present invention, temperature and resist sensitivity are shown in Figure 3.
Give an example. In this example, the sensitivity suddenly increases when the temperature exceeds 150°C. The sensitivity changes slowly from room temperature to about 13C, and there is no problem in practical use. Therefore, if the temperature of the resist is controlled so that it does not exceed 130° C. due to the heat generated by the previous irradiation, the heat generated by irradiation to that location, and the heat generated by subsequent irradiation, uneven sensitivity due to a rise in resist temperature can be prevented. (Conventional charged beam lithography equipment did not have a means to measure the temperature of the resist on the sample. Therefore, various trial lithography was performed, and after developing and confirming conditions that no unevenness would occur, the actual lithography was performed. ) That is, a temperature detector is attached to detect the temperature at the drawing position on the sample, and this allows real-time measurement of temperature changes before and after beam irradiation. For example, the previous irradiation was 100CI.
In the next irradiation, the resist that rose at 130°C
It is possible to measure things such as reaching . Also, during drawing, the sample surface
When the temperature reached 10℃, drawing was stopped until the temperature dropped.
By searching the portions where the temperature is 100° C. or lower and repeatedly performing the writing on the portions, it is possible to perform the writing efficiently while maintaining the temperature below the damage limit of the resist.

In the drawing method of the present invention, it can be said that the sensitivity unevenness due to the rise in temperature of the resist is caused by the accumulation of a small amount of heat generated from each shot, and the unevenness caused by the gradual rise in temperature as a whole. (In the second half, the heat of the first half is accumulated.) The present invention has a second drawing area in which the drawing area is divided into four rectangular drawing areas.
figure. The drawing order is to alternately draw within the strips b and d, and after completion, draw within the strips a and C alternately. This kind of drawing provides the following advantages.

1. Since it is strip-shaped and has a small area, there is little heat accumulation.

2. Drawing is done on every other strip, and by making the width of the strip narrower, heat is dissipated to both sides and temperature rise can be avoided.

3. Since the two strips are drawn alternately, there is a gap between the irradiation of the previous strip and the irradiation of the adjacent strip, which is the time during which another strip is irradiated, and this time can be used as heat dissipation time.

(Example) The present invention will be explained in detail below.

It is assumed that the sample stage (IG) in Figure 1 is loaded with a sample (mask, etc.) coated with a resist showing the temperature-sensitivity characteristics shown in Figure 3.The shape of the pattern to be drawn and the dose (beam The temperature rise in the irradiated part from irradiation i) is 30℃
Suppose that it is calculated that there is. Based on the drawing data sent from the computer, the drawing control circuit η moves the sample stage α and controls the beam to draw a pattern on the sample. An infrared temperature detector (9) constantly measures the resist temperature of the sample and sends a temperature signal to the drawing control circuit (1?). In the drawing control circuit, the resist sensitivity characteristic shown in FIG. 3 and the temperature rise of the irradiation part are set at 30° C., and the upper limit of the temperature of the resist that can be written is set at 100° C. The drawing control circuit stops drawing when the temperature signal reaches 100°C. Drawing is restarted after waiting for the temperature signal to become 100 degrees Celsius or less. Alternatively, the lithography may be performed by switching to a lithography method (for example, lowering the beam current and lengthening the irradiation time) that causes a lower temperature rise even though it takes more time. By detecting the temperature in real time in this way, countermeasures can be taken in accordance with the temperature rise of the resist, so writing can be performed with less loss time and short writing time, and unevenness in sensitivity due to temperature rise can be prevented.

In addition, this configuration is effective for obtaining temperature data on the resist surface when the drawing conditions are variously changed without controlling the drawing based on the temperature of the resist.

If the temperature detector shown in FIG. 1 is replaced with an infrared temperature image scanner, the pattern shape can be seen in the area immediately after drawing because the temperature is high.

As a modified example, as shown in Fig. 4, infrared rays may be guided outside the sample chamber αυ by a light guide αa, and detected by an infrared detector (15) outside the sample chamber.Instead of the light guide α barrel, a mirror may be used. Infrared rays may be guided outside the sample chamber by reflection.

Although the example of the infrared detector shown in FIG. 2 is a monochromatic type, it may also be a two-color type that measures the energy ratio of two different wavelength bands.

In an embodiment of the drawing method, a data select buffer circuit CD is provided between the high-speed data transfer controller (to) and the high-speed data controller 4 of the charged beam drawing device in FIG. 5, and the drawing area (AxB in FIG. 6) is shaped like a strip. a, b, c, d
The data select buffer circuit is divided into four parts: a, b,
The data is classified into areas c and d and stored in memory.

The high-speed data controller reads the necessary data from the memory of the data select buffer circuit in areas a, b, c, and d, and reads the necessary data from one strip-shaped area and another area (for example, b and d in Figure 2). Draw alternately.

With such a drawing method, in a strip-shaped section, a different section is drawn every two lines, so there are alternating breaks, which is useful for heat dissipation of the resist.

In order to realize the above-described drawing method, the present invention provides a data select buffer circuit Qυ in front of a high-speed data controller having a conventional configuration, as shown in FIG.

The configuration of this circuit is shown in FIG. The selector selects data a, b, c, depending on the drawing position relative to the reference position in Figure 6.
It is classified into areas d and sent to memory.

EMP occurs when data enters memory @, (c), @, (b)
When the signal is @0, a drawing start signal is output. FIFO or the like is used as the memory. When any of the memories becomes full, an FLL signal is output and the selector [with] stops.

The drawing start signal is sent to the high speed data controller@. The high-speed data controller alternately reads drawing data 1 and drawing data 2 and performs drawing. When the b memory and the d memory become empty and the j5EMP signal is output, the switching circuit is activated and the C memory and the C memory are connected to the high speed data controller. a, b.

When c and d memories become empty, E is also sent from C memory and C memory.
MP signal is output. This signal starts the selector and writes the drawing data to the a, b, c, and d memories. Furthermore, the seventh
In the figure, memory write and read signals are omitted.

The drawing order will be explained. When drawing at reference position 1 in Fig. 6, start drawing from area 2, move to d, return to b, repeat, and when you reach the bottom, move from b to above a, then a, Repeat c. First, write b and d first, then a and C.

Write a and C first, then! :If you write the d in the order, it is not desirable to write the d in the reference position 1 and then write the a in the reference position 2, which is not preferable because it will be written next to the letter d.

Modified Example In the above embodiment, a method was explained in which the drawing area and the drawing order are controlled by hardware, but the drawing data may be changed so that it appears alternately in strip-shaped areas without changing the hardware.

Although the drawing area is divided into four in the embodiment, it is not limited to four. In the embodiment, one data select buffer circuit was used, but two are provided in parallel, so that when one is selecting data and writing to memory, the other is alternately sending previously written data to the high-speed data controller. If used, the waiting time for data selection is eliminated.

〔Effect of the invention〕

In the present invention, the following effects can be obtained by measuring the resist surface temperature during drawing.

a) The resist surface temperature during drawing can be known in real time.

b. Drawing can be controlled based on the resist surface temperature during writing before the sensitivity changes significantly, and the temperature can be kept below a certain level. Therefore, uneven development can be prevented.

The drawing status can be monitored by observing the temperature of the resist surface with a C infrared image sensor.

Moreover, the following effects can be obtained by the above-mentioned present invention.

d Compared to the method of drawing at time intervals for heat dissipation,
There is no time when you are not drawing, so the drawing time does not increase.

e If the drawing area and drawing order are controlled using hardware (circuits), conventional drawing data can be used as is.

f. It is easy to change the conventional device by just adding one part of the circuit. The method disclosed in Japanese Patent Application Laid-Open No. 14720/1983 requires a complicated calculation circuit for calculating the irradiation amount based on the interval between shots, and also seems to require a lot of calculation time.

g The data selection circuit can be configured with a comparator and the processing time is fast.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of an embodiment of the drawing apparatus of the present invention, FIG. 2 is an explanatory view showing a main part of FIG. A sectional view of the main parts of the embodiment,
Figures 5 to 7 are for explaining an embodiment of the drawing method of the present invention. Figure 5 is a circuit configuration diagram, Figure 6 is an explanatory diagram for explaining the writing procedure, and Figure 7 is the same as that shown in Figure 5. The main circuit diagram, FIG. 8, is an enlarged view for explaining the resist surface drawn by a conventional drawing means. 1: Electron gun, 2: Ion pump, 3: Centering coil, 4: GL lens, 5 Ni blanking plate, 6: Second lens, 7: Scanning deflection coil, 8: Projection lens, 9: Infrared temperature sensor, 10 : Sample stage, 11: Sample chamber, 12:
Ion pump, 13: Diffusion pump, 14: Lens, 15
: infrared sensor, 16: signal processing circuit, 17: drawing control circuit, 18 light guide, 19: buffer memory, 2
0: Transfer controller, 21: Data select packer circuit, 22: Speed measurement data controller, 23: Selector, 24, 25, 26, 27: Memory. Agent Patent Attorney Nori Chika Yushiro Patent Attorney Mitsuyuki Matsuyama Figure 1 Figure 2 Figure 3 Figure 4 Figure 6 Figure 7

Claims (6)

[Claims] (1) In a device that draws a pattern on a substrate such as a mask or wafer coated with resist using a charged beam, the drawing area is divided into three or more divided areas, and two or more areas are separated by one or more areas. A charged beam drawing method that draws images alternately. (2) A charged beam drawing method according to claim 1, characterized in that the divided areas are formed into strips. (3) A charged beam lithography method according to claim 1 or 2, characterized in that the lithography method is controlled by a data selector circuit and a memory circuit. (4) A charged beam lithography device that irradiates a resist coated on a substrate with a charged beam to draw a pattern, characterized in that it is equipped with an infrared temperature detector that detects the temperature of the resist at or near the drawing area. drawing device. (5) A charged beam lithography apparatus according to claim 4, characterized in that an infrared temperature image scanner is used as an infrared temperature detector. (6) The charged beam lithography apparatus according to claim 4 or 5, characterized in that the temperature of the resist is controlled by stopping or changing the lithography by detecting the temperature of the lithography area. Charged beam lithography equipment.