JPH0443626A - X-ray exposure - Google Patents

Abstract

PURPOSE:To adjust the attenuation of synchrotron rediation in an optical path, make the intensity of X-ray constant, and realize the exposure of constant irradiation light amount, by suitably controlling the composition and the pressure of the atmosphere in a chamber and further the pass length of the synchrotron radiation in the atmosphere according to fluctuation of the output of synchrotron radiation. CONSTITUTION:In the title method, the atmosphere in a chamber 9 is controlled by a gas injection amount adjusting apparatus 10. A current monitor 11 is arranged in a storage ring 1. The monitor signal is inputted to a control computer 12, and the detected value of storage current IA is displayed. Further in a chamber 9, the following are installed; an O2 partial pressure monitor, and an X-ray intensity sensor constituted of a silicon diode on the side of a wafer 8 resist coating surface. Thereby the control is performed to increase the purity of atmosphere whose X-ray absorption is little, in accordance with the attenuation of radiation light output. As to the control of atmosphere in the chamber, the control is performed to decrease the injection amount of atmosphere in the chamber, in accordance with the attenuation of synchrotron radiation output. Further, the pass length of the synchrotron radiation in the atmosphere in the chamber is controlled by changing, e.g, the position of a radiation light transmitting window.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention uses synchrotron radiation as a light source for semiconductor phosphorography xIi! Regarding exposure method.

[Conventional technology]

In recent years, design rules for semiconductor devices have begun to enter the quarter-micron range, and synchrotron radiation phosphorography is expected to be a transfer technology that can replace photophosphorography. Second, synchrotron radiation has a continuous spectrum, which includes powerful and highly directional soft XI.

This is because such a soft XIA is ideal as an X-ray source for lithography technology in terms of throughput and resolution.

Figure 3 shows an ultra-high vacuum electron storage ring (1) orbiting at a speed close to the speed of light.The electron is a bending electromagnet (2).
The configuration of the apparatus is shown when synchro 1 to ron synchrotron radiation, which is emitted when deflected by , is used for phosphorography. This synchrotron radiation passes through the Be 13 line 3) and is oscillated in the direction of gravity by an oblique incidence reflecting mirror (4).
After passing through the light transmitting window (5), the aligner (
6) Enter. Then, in the aligner (6), the mask (7) pattern is transferred onto a plate-like object (8) to be exposed (such as a silicon wafer) to which a resist is attached.

[Problem that the invention seeks to solve]

However, the electrons orbiting within the storage ring (1) collide with trace gas ions generated within the storage ring (1) and are lost, and the current within the storage ring (1) gradually decreases. 9 Therefore, the synchrotron radiation output (intensity) rapidly decreases in all wavelength ranges due to the low r of this accumulated current. Although there are some in the atmosphere inside the chamber (9), these factors have little to do with the temporal attenuation of the emitted light).

On the other hand, lithography requires a certain amount of light on the resist surface. In ordinary photolithography, a light source (
Since the irradiation intensity of ultraviolet rays (for example, ultraviolet rays, etc.) is constant, the necessary amount of light can always be obtained with exposure for a certain period of time.3 On the other hand, the decrease in the synchrotron radiation output of the storage ring (1) is due to the accumulation of light. This creates a need to increase the exposure time by the amount of current reduction to obtain a light amount corresponding to the resist sensitivity8.In other words, the life time when the storage current is 1/eL2 is at most 1
If the maximum output is to be obtained for 0 hours, it will be as short as 2 to 3 hours, so in this state, the degree of attenuation will be -0.74%. Even with ideal aligner characteristics, the exposure time per 8-inch wafer is 88 seconds, so the exposure time increases by more than 1% while exposing 1 - wafer. or.

If you use it for 10 hours, the exposure time will be 237 times longer.

The present invention was created in view of the following problems.
Adjusting the attenuation of the synchrotron radiation in the middle of the synchrotron radiation optical path in response to temporal fluctuations in synchrotron radiation output so that the X-ray intensity remains constant, making it possible to expose with a constant amount of irradiation light in a constant time. This is what we are trying to do.

[Means for solving problems]

Therefore, the method of the present invention surrounds the optical path of synchrotron radiation light with a chamber, and adjusts the composition and pressure of the surrounding area in the chamber and the synchrotron radiation according to fluctuations in accumulated current or output fluctuations of synchrotron radiation light. The basic feature is that the attenuation of the x, 1 component of the emitted light is controlled by controlling one or more of the passage lengths in the atmosphere.

As mentioned above, the synchrotron radiation optical path from the synchrotron radiation transmission window to the aligner is usually surrounded by a chamber and filled with a helium atmosphere, air, etc., and the inside of the chamber is also subject to precise pressure control and gas purity control. The X-ray transmittance is maintained at a constant level. However, such a configuration does not take into account the above-mentioned attenuation of the accumulated current over time, and therefore, if the X-ray transmittance is held constant, the accumulation current or synchrotron radiation output will attenuate over time. It is not possible to suppress variations in the amount of irradiated light over time during exposure.

The configuration of the present invention is to control the X-ray transmittance in the optical path of the synchrotron radiation in the chamber by controlling the above-mentioned elements in connection with the attenuation of the synchrotron radiation output.

The composition of the atmosphere inside the chamber is controlled by changing the mixing ratio of, for example, helium atmosphere, which has low X-ray absorption, and nitrogen gas, which has a higher absorption rate. Control is performed to increase the purity of the atmosphere with less XR absorption as the output is attenuated.

In addition, the control of the atmospheric pressure inside the chamber is carried out, for example, by adjusting the amount of atmosphere injected into the chamber. Usually, as the amount increases, the amount of X-rays absorbed by the gas molecules increases relatively. Conversely, if the amount decreases, the amount of X-ray absorption will decrease. Therefore, in the present invention, control is performed to reduce (depressurize) the injection amount of the atmosphere in the chamber as the synchrotron radiation output attenuates.

Furthermore, the length of passage of the emitted light through the atmosphere within the chamber is controlled by, for example, changing the position of the emitted light transmission window.

〔Example〕

FIG. 1 shows an outline of a synchrotron radiation exposure apparatus used to carry out the method of the present invention.

In the figure, (1) is the electron storage ring, and (2) is the ring (1).
In this example, one of the bending electromagnets is a bending electromagnet that is one of the components, and in this example, there are 8 It is placed.

In this X-ray haze aS, an oblique-incidence reflecting mirror (4
) is installed at the end of the beam line (3), and a synchrotron radiation transmitting window (5) made of a beryllium film with a thickness of 25 μm is installed.
) is provided to separate the ultra-high vacuum beam line (3) side from the aligner (6) side. On the aligner (6) side, the entire synchrotron radiation optical path from the synchrotron radiation transmitting window (5) to the mask (7) and the resist-coated wafer (8) is surrounded by a chamber (9). is filled with an atmosphere consisting mainly of helium gas.

This embodiment is equipped with a helium gas tank and an atmospheric air blower (not shown), the atmosphere inside the chamber (9) can be controlled by a gas injection amount adjustment device (10), and a pressure adjustment valve (not shown) can control the atmosphere inside the chamber (9). maintains a constant internal pressure.

Also, a current monitor (11) for measuring the intensity of the electron beam orbiting in the electron orbit of the storage ring (1) is installed in the storage ring (1)! At the same time, this monitor signal is input to the control computer (12) to display the detected value of the accumulated current IA.

Furthermore, in this embodiment, a 07 partial pressure monitor (
An X-ray intensity sensor (not shown, however, located at a distance of 300+ m++ from the synchrotron radiation transmission window (5)) consisting of a silicon diode was installed on the resist-coated surface of the wafer (8) and the atmosphere composition during the experiment. was used for sensing and measuring X-ray intensity.

In the experiment, the atmosphere in the chamber (9) was first replaced with helium gas, and the zero concentration was measured using a zero partial pressure monitor, and it was confirmed to be 500 ppm.
The amount of contamination was found to be 2000 ppm.

Next, when one storage current of the electron storage ring (1) was measured by the current monitor (11), the initial value was 200 mA.
Met.

In this state, synchrotron radiation is taken out to the aligner (6) side and transmitted through the synchrotron radiation transmission window (5) 3001 [.

The output of the X-ray intensity sensor installed at the position was adjusted to be 10 mV in the initial state. Further, the helium atmosphere was adjusted to 23° C. and 1 atm.

Then, the first wafer (8
), the output of the X-ray intensity sensor is 10m
After confirming that the voltage was V, one shot of exposure was completed with an exposure time of 3.6 seconds. The subsequent development process was completed in 90 seconds and was appropriate.

Thereafter, a decrease in the accumulated current in the ring (1) was confirmed by the current monitor (11), and there was a tendency for the output of the X-ray intensity sensor to decrease in proportion to this.

Therefore, the present inventors injected high-purity helium into the chamber (9) using the gas injection amount adjusting device (10) to improve the helium purity, and the output of the X-ray intensity sensor was
The exposure operation was continued while maintaining the voltage at V.

After 45 minutes, the accumulated current had decreased to 175 mA, but 0. , the partial pressure monitor showed a concentration of 02], 80 ppm, and at this time, the output of the X-ray intensity sensor was also ]Omν.

During this time, the reproducibility of Kirigou Telegraph was good, and the development process was 0.00 seconds after the development process.
A 25 μm pattern can be formed with high precision; however, the overlay accuracy is 0.08 μm in alignment 1).

Next, the previous exposure was interrupted [7, the beam was additionally incident on the electron storage ring (1), and the accumulated current was increased to 200%.
It was returned to mA. Further, the purity of the helium atmosphere in the chamber (9) was lowered until the 02fA degree became 500ρ[1111, and thereafter exposure was continued in the same manner.

Through the following experiments (7), we found that during X-ray haze, the accumulated current or synchrotron radiation output attenuates with red time (correspondingly, by controlling the attenuation of the X-ray component in the synchrotron radiation optical path, the It was confirmed that it was possible to realize exposure with a constant irradiation light in a certain amount of time.In addition, the reproducibility of the resulting resist 1 to pattern was improved.
It has become clear that deterioration in transfer position accuracy, which conventionally occurs due to a phenomenon mainly caused by heat generation due to absorption of X-rays by an X-ray mask, can also be prevented. Furthermore, the method of the present invention can also be applied to electron storage rings that perform additional injection, and because the storage efficiency is improved, the amount of radiation generated during synchro-1-ron operation is reduced, which has the ripple effect of improving safety. was gotten.

FIG. 2 shows another example of an apparatus for implementing the method of the present invention.

In this implementation device, the beam line (3) is separated into two parts near the synchrotron radiation transmission window (5), and a stretchable ultra-high vacuum bellows (13) is interposed between the two parts and connected to each other. Also, the tip side of this bee 11 line (3) can be moved along a guide (not shown) towards the electron storage ring (1) which is a light source and the aligner (6) by the action of a pulse motor (14) and a ball screw (15). ing. And a synchrotron radiation transmitting window (5) on the tip side of the beam line (3).
is fixed, and as the tip of the beam line (3) moves, the radiation transmitting window (5) also moves. Furthermore, this radiation transmitting window (5) has the other end of another stretchable bellows (16) hermetically secured around the opening of the chamber (9), so that an external atmosphere is not contained in the chamber (9). The radiation transmitting window (5) can be moved back and forth in the chamber (9) while preventing the radiation from entering the chamber (9).

With the above configuration, the synchrotron radiation transmission window (5) is connected to the storage ring (1) side and the aligner (6) by a pulse motor (14) or the like.
) side, but the beamline (3
) is kept at an ultra-high vacuum, and the inside of the chamber (9) is controlled to have a helium atmosphere at a constant concentration. Note that the pressure inside the chamber (9) is controlled so that the pressure inside the chamber (9) does not fluctuate due to the movement of the radiation transmitting window (5).

As a result of the above configuration, the movement of the synchrotron radiation transmission window (5) changes the passage distance of the synchrotron radiation in the surrounding atmosphere of the chamber (9), thereby reducing the attenuation of the X-ray component of the synchrotron radiation. It becomes possible to roll Con1.

〔Effect of the invention〕

According to the present invention described in detail above, by controlling the attenuation of the X-ray component in the synchrotron light optical path in accordance with the temporal attenuation of the accumulated current or synchrotron radiation output during X-ray cod radiation, a constant energy density is achieved. Exposure can be achieved, and throughput during exposure can be improved.

Furthermore, when a plurality of exposure devices are installed in one electron storage ring, it is also possible to control each exposure device with different exposure amounts.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram showing an overview of the equipment configuration of the X-ray exposure equipment in which experiments were carried out to implement the method of the present invention, Figure 2 is an explanatory diagram showing an example of the equipment for implementing the method of the present invention, and Figure 3 is an electronic storage FIG. 2 is an explanatory diagram showing an apparatus configuration when using synchrotron radiation light emitted from a ring for lithography. In the figure, (1) is an electron storage ring, (2) is a bending electromagnet,
(3) is the beam line, (4) is the oblique incidence reflection mirror,
(5) is a synchrotron radiation transmission window, (6) is an aligner, (7) is a mask, (8) is a wafer, (9) is a chamber, (10) is a gas injection amount adjustment device, (11) is a current monitor, (12)
indicates each control computer.

Claims (1)

[Claims] In an X-ray exposure method using synchrotron radiation as a light source, a chamber surrounds the optical path of the synchrotron radiation, and according to changes in the accumulated current or output of the synchrotron radiation,
An X-ray exposure method characterized in that the attenuation of the X-ray component of synchrotron radiation is controlled by controlling one or more of the composition and pressure of the atmosphere in the chamber, as well as the passage length of synchrotron radiation through the atmosphere. .