JPH02253549A - Synchrotron radiation beam exposure method and its device - Google Patents

Abstract

PURPOSE:To eliminate time-wise changes of a synchrotron radiation beam in a specified wavelength band by detecting a stored current or a synchrotron radiation beam output, and hereby controlling the intensity of a deflecting magnetic field along with stored beam energy. CONSTITUTION:A current stored in a storage ring 1 is detected by a current monitor 4 whose output controls both the output of an electron beam acceleration high-frequency cavity 3 and the intensity of a deflecting magnetic field given by each of deflecting electromagnets 2 via an arithmetic and control circuit 5. Or the output of a synchrotron radiation beam is detected by a radiation beam monitor 6 whose output, in the same manner as aforementioned, controls the acceleration high-frequency cavity 3 and each of the deflecting electromagnets 2, and therefore stored beam energy is time-wise controlled such that a synchrotron radiation beam output may become constant in a wavelength band near 10 angstroms in accordance with a value of (n) corresponding to a level given if a wavelength band is set in the vicinity of 10 angstroms in common.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a synchrotron radiation exposure method and an apparatus for using synchrotron radiation in semiconductor lithography.

[Conventional technology]

In recent years, design rules for semiconductor devices have begun to enter the submicron range, and synchrotron radiation photolithography is expected to be a transfer technology that can replace photolithography. This is because synchrotron radiation has a continuous spectrum and contains powerful and highly directional soft X-rays, and these soft X-rays are the This is because it is ideal as a radiation source.

Figure 9 shows an ultra-high vacuum electron storage ring (1) in which electrons orbiting at a speed close to the speed of light are transferred to a deflecting electromagnet (2).
This shows an apparatus configuration in which synchrotron radiation light emitted when deflected by is used for lithography. This synchrotron radiation light is transmitted from the beam line (10
), it is oscillated in the vertical direction by an oblique-incidence reflecting mirror (11), passes through a Ba window (12), and then enters an aligner (13). Then, in the aligner (13), the mask (14) pattern is transferred onto a plate-like object (15) to be exposed (such as a silicon wafer) to which a resist is attached. Note that (3) in Figure 1 is an electron beam acceleration high frequency cavity that accelerates the electron beam and increases the accumulated beam energy.

[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. become. Therefore, as the accumulated current decreases, the synchrotron radiation output rapidly decreases over the entire wavelength range, as shown in FIG. 10.

On the other hand, lithography requires a certain amount of light on the resist surface. In ordinary photolithography, the irradiation intensity of the light source (for example, ultraviolet light) is constant, so the required amount of light can always be obtained with exposure for a certain period of time. On the other hand, a decrease in the synchrotron radiation output of the storage ring (1) inevitably creates a need to increase the exposure time by the amount of the decrease in the storage current to obtain a light amount corresponding to the resist sensitivity. Become.

In other words, the life time for which the accumulated current becomes 1/e is at most 10
Since the time required to obtain the maximum output is as short as 2 to 3 hours, the degree of attenuation is -0.74%/min in this state. 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 one wafer. Also, 1
If it is used for 0 hours, the exposure time will be 2.7 times longer.

The present invention was devised in view of the above-mentioned problems, and aims to eliminate temporal fluctuations in synchrotron radiation output and to enable exposure with a constant amount of irradiation light in a constant time.

[Means for solving problems]

The basic structure of the present invention is to compensate for the decrease in synchrotron radiation output due to a decrease in the accumulated current in the ring by increasing the accumulated beam energy, thereby stabilizing the synchrotron radiation output over time and keeping it constant. This makes it possible to perform exposure that provides a constant amount of irradiation light in a certain amount of time. Therefore, the first invention of the present application detects the accumulated current in a storage ring or detects the output of synchrotron radiation light, and detects a temporal decrease in the detected accumulated current or a temporal change in the output of synchrotron radiation light. Based on this, the accumulated beam energy of the storage ring is temporally controlled so that the synchrotron radiation output in the wavelength range limited by the synchrotron radiation optical system for exposure is constant, and the electron orbit radius is constant. The basic feature is that the strength of the deflecting magnetic field of the deflecting electromagnet is also controlled so that

In particular, if the wavelength range limited by the synchrotron radiation optical system is around 10 people, the synchrotron synchrotron radiation output will be around 10 people based on the n value determined corresponding to the accumulated beam energy in this wavelength range. so that it remains constant in the wavelength range.

Ideally, the accumulated beam energy should be temporally controlled.

Furthermore, a second invention relates to an exposure apparatus for carrying out the above invention, and as shown in FIG.
A current monitor (4) detects the accumulated current in the storage ring (1), and a current monitor (4) detects the accumulated current in the storage ring (1). It has an arithmetic control circuit (5) that controls the output of the electron beam acceleration high-frequency cavity (3) and the deflection magnetic field strength of the deflection electromagnet (2).

In addition, a third invention provides the current monitor (4) of the second invention.
As shown in Figure 2, instead of detecting the accumulated current by using It is designed to detect the output of synchrotron radiation, and the arithmetic control circuit (5) keeps this output constant based on temporal fluctuations in the output of synchrotron radiation detected by the monitor (6). , output control of the electron beam acceleration high-frequency cavity (3) and deflection electromagnet (2) similar to the second invention.
) controls the deflection magnetic field strength.

The present invention will be explained in detail below.

Synchrotron radiation is output light that has a maximum within its wavelength range, and when the orbital radius R is constant, as shown in Figure 3, when the accumulated beam energy (acceleration voltage) E is changed, the output light changes. Both the maximum wavelength and maximum value change.

Synchrotron radiation has a wavelength distribution as schematically shown in FIG. 4, and the basic relational expression regarding its output is as follows.

Wavelength maximum output Pp (V/nvmrad”): Pp=3
0.0E'(GeV)B"(T)IA(A) -・
...■Full wavelength integrated output Pt (niv): PT= 26.6E" (GaV) B(T) IA(A)
−−−−■ Maximum output wavelength λP (person): λP = 2.348R (m)/E” (GeV) = 7.84
/BB” ++■Orbital radius R (+*): R= 3.34E (GeV)/B (T) ・・・・・・
・・・・・・・・・・・・・・・・・・■ Therefore, the output P of the synchrotron radiation light decreases over time as the accumulated current decreases, and as shown in Fig. 10 above. It comes to show.

As mentioned above, the attenuation is typically -0.74%/min.

If the exposure time for an 8-inch wafer is 72 seconds (exposure field 25 m', number of shots 36.1, exposure time 0.5 seconds per field), the output will decrease by about 1%.

Therefore, it is best to detect the storage current modification in the storage ring and increase the stored beam energy E in proportion to the decrease in the storage current IA each time the number of wafer exposures increases to compensate for the decrease in synchrotron radiation output. (Such control may be performed by detecting the output P of the synchrotron radiation light instead of detecting the accumulated current).

At this time, when the accumulated beam energy E is increased, the electron orbit radius R also becomes larger according to equation 0. Therefore, in order to stabilize the operation of the storage ring (1), it is sufficient to make the increase in the storage beam energy E and the increase in the deflection magnetic field strength B of the deflection electromagnet equal to each other according to the equation 0, and to keep the electron orbit radius R constant.

That is, under the condition of 8EVE = ΔB/H, Pp = 33
4.67E"(GeV)・IA(A)/R"(m)
・---・■P = 296.74E'(GaV)・I
A(A)/R(m) --■. Also, what is the variation?

Here, the condition for constant output is ΔP/P = 0, and the condition for constant orbital radius is ΔR/R = 0, so Pp: --"= 8E..."L...・・・・・・・・・
・・・・・・・・・・・・■IA E PT; -dan=4E・・」L・・・・・・・・・・・・
・・・・・・・・・[Phase]■A E.

On the other hand, the wavelength range used for synchrotron radiation lithography is the wavelength range used for synchrotron radiation lithography.
11) on the short wavelength side, cutoff on the long wavelength side due to absorption in the Be window (12), and cutoff on the long wavelength side due to absorption in the Be window (12).
) Due to the cutoff on the longer wavelength side due to the absorption of the atmospheric gas and the mask (14), and the sensitivity wavelength dependence determined by the absorption characteristics of the resist, the oblique incidence of 0 for example SiC 1° is limited to around 10 lnm. Type reflective mirror (11)
In addition, a 25μ thick Be window (12) and an aligner (13) were installed.
In an example of an optical system using synchrotron radiation using He gas (at 350 Torr) and a SiN 1μ heavy membrane thickness mask (14), the wavelength range is as shown by the curve X in Figure 5, and the wavelength range of the half width is will be 7.4 to 10 people. Also, using the same oblique incidence type reflection mirror (11), Be
Window (12), 100 Torr He gas, SiN 1μ
In the example of the optical system of the m-membrane thickness mask (14), the optical system is shown by curve Y in the same figure, and its wavelength range is 7.4 to 1
There will be three people.

The synchrotron radiation light output P of wavelength components within this range shows a large dependence on the accumulated beam energy E, and is expressed by the following equation.

P=to-En・IA (K is a constant) ・・・・・・・・・
・・・・・・・・・・・・The value of n in formula 00 is a constant determined by the limited wavelength range and the accumulated beam energy. When the wavelength range is limited to 7 to 10 people and 7 to 13 people, The values of n will be shown in FIG.

Furthermore, based on the above equation 0, a constant condition for synchrotron radiation light output in a limited wavelength range can be obtained as follows.

Therefore, depending on the degree of decrease in the accumulated current ΔE
/E, the synchrotron radiation light output P becomes constant over time in this limited wavelength range.

In carrying out the method of the present invention described above, the accumulated current is detected by the current monitor (4) and the decrease in accumulated current ΔIA/unit is sensed, or the synchrotron radiation output P is detected by the synchrotron radiation monitor (6). detecting the attenuation of the emitted light output P;
From these detected values, the arithmetic control circuit (5) calculates the increase ΔE/E in the accumulated beam energy based on the above equations 0 and 0.

Also, from this calculated value, the increase in the deflection magnetic field strength of the deflection electromagnet (2) ΔB is calculated based on the formula 0 so that the orbit radius R is constant.
/B is calculated. Based on these calculated values, the calculation control circuit (5) controls the electron beam acceleration high frequency cavity (3).
and the deflection magnetic field strength of the deflection electromagnet (2) to prevent the synchrotron radiation output P in a predetermined wavelength range from changing over time. As a result, the amount of irradiated light becomes stable over time.

〔Example〕

FIG. 7 shows an embodiment of a synchrotron radiation exposure apparatus according to the second invention, in which (2) indicates a bending electromagnet, (
3) is an electron beam acceleration high frequency cavity, which constitutes the storage ring (1). A beam line (10) is provided in one of the bending electromagnets (2), and a 5iC1° oblique incidence type reflection mirror (11) is installed in the middle of the beam line to vertically expand the irradiation area of the synchrotron radiation. In addition, a Be window (12) with a thickness of 25 μm is provided at the end of the beam line (10), and the beam line (10) is in an extremely high vacuum.
The side and the aligner (13) side are separated. The inside of the aligner (13) is filled with a He gas atmosphere at a reduced pressure of 350 Torr, and a SiN 1 μm membrane thick mask (14) and a resist-coated wafer (15) are provided therein.

In this embodiment, a current monitor (4) is used to measure the intensity of the electron beam orbiting the electron orbit of the storage ring (1).
) is installed in the storage ring (1), and this monitor signal is input to the arithmetic control circuit (5) to detect a decrease in the storage current.

When the arithmetic control circuit (5) detects a decrease in the accumulated current, it performs a predetermined arithmetic operation and sends a control signal to the power supply section (3a) of the electron beam acceleration high frequency cavity (3) to increase the electron beam acceleration. The control signal sent to the power supply unit (3a) at this time, which controls the output of the beam acceleration high-frequency cavity (3), is also sent to the power supply unit (2a) of the deflection electromagnet (2), and controls the intensity of the deflection magnetic field. will be done at the same time.

Next, the operation of the present invention using such a device configuration will be explained.

At the beginning of synchrotron radiation irradiation, the accumulated beam energy E of the storage ring (1) was controlled to 0.9 GeV.

At this time, since the wavelength range limited by the synchrotron radiation optical system of the beam line aligner system is 7.4 to 10, the n value is 5.8 from FIG. 6. Decrease in accumulated current detected by (4) ΔIA/
When I becomes 1%, the arithmetic control circuit (5) calculates the increase in accumulated beam energy from the condition shown in the above formula 0.
E was set to 0.29%, and based on this calculation result, a control signal was sent to the power supply section (3a) of the electron beam acceleration high-frequency cavity (3), and the accumulated beam energy E was corrected to 0.9026 GeV. At the same time, the arithmetic control circuit (5)
) also sends a control signal to the power supply unit (2a), and 8E/E=
Control is also performed to satisfy the condition of ΔB/H.

As the accumulated current decreases, as a result of continuing the same control as described above, the accumulated current ΔIA decreases by 1/1, as shown in FIG.
Until the life time reached e, the synchrotron radiation light output P became approximately constant in the limited wavelength range of 7.4 to 10 people.

〔Effect of the invention〕

According to the present invention described in detail above, it becomes possible to compensate for the decrease in the synchrotron radiation output due to the decrease in the accumulated current in the storage ring by increasing the accumulated beam energy. By obtaining a synchrotron radiation output, it is possible to perform exposure with a constant amount of irradiation light in a constant time.

Furthermore, in addition to the specific wavelength range of synchrotron radiation phosphorography, the method of the invention can obtain a constant output by performing similar control in other wavelength ranges used in CVD and other fields. Therefore, it is possible to control irradiation for a certain period of time.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the device configuration of the second invention of the present application, FIG. 2 is an explanatory diagram also showing the device configuration of the third invention, and FIG. 3 is the wavelength distribution of synchrotron radiation light corresponding to each accumulated beam energy. Fig. 4 is a graph schematically showing the wavelength distribution of synchrotron radiation, Fig. 5 is a graph showing the wavelength range that can be used in synchrotron radiation lithography, and Fig. 6 is a graph showing limited wavelengths. FIG. 7 is an explanatory diagram showing the configuration of the apparatus according to the second embodiment of the invention, and FIG. 8 is a graph showing the n value of synchrotron radiation output dependence E' on the area. FIG. 9 is an explanatory diagram showing the configuration of a synchrotron radiation exposure device installed in the storage ring, and FIG. 10 is a graph showing synchrotron radiation light output from the above device. FIG. 3 is a graph diagram showing the attenuation state of the output of the radiation destination at time. In the figure, (1) is a storage ring, (2) is a bending electromagnet, and (3) is a storage ring.
) is an electron beam acceleration high-frequency cavity, (4) is a current monitor,
(5) is an arithmetic control circuit, (6) is a synchrotron radiation monitor, (10
) is the beam line, (11) is the oblique incidence reflection mirror, (
12) is a Be window, (13) is an aligner, (14) is a mask, and (15) is a wafer. Fig. Wavelength (nm) Fig. 2゜-ray Wavelength (in) Fig. 0.8 1.0 1.2 Accumulated beam energy (GeV) Fig. Fig. Time -

Claims (4)

[Claims] (1) In a synchrotron radiation exposure method in which a mask pattern is exposed on a plate-like object to be exposed using synchrotron radiation emitted from a storage ring, the accumulated current in the storage ring is detected, or the synchrotron radiation synchrotron radiation in the wavelength range limited by the exposure optical system using synchrotron radiation. In addition to temporally controlling the accumulated beam energy of the storage ring so that the optical output is constant,
A synchrotron radiation exposure method characterized by controlling the deflection magnetic field strength of a deflection electromagnet so that the electron orbit radius is constant. (2) When the wavelength range limited by the synchrotron radiation optical system in the synchrotron radiation exposure method described in the previous section is around 10 Å, the synchrotron radiation is 2. The synchrotron radiation exposure method according to claim 1, wherein the accumulated beam energy is temporally controlled so that the synchrotron radiation output is constant in a wavelength range around 10 Å. (3) In a synchrotron radiation exposure apparatus having a storage ring, a synchrotron radiation beam line, and an aligner, a current monitor detects the accumulated current in the storage ring, and the time of the accumulated current value detected by the monitor. and an arithmetic control circuit that controls the output of the electron beam acceleration high-frequency cavity in the storage ring and the deflection magnetic field strength of the deflection electromagnet so that the output of synchrotron radiation light is constant based on fluctuations in the synchrotron radiation. Synchrotron radiation exposure equipment. (4) In a synchrotron radiation exposure apparatus having a storage ring, a synchrotron radiation beam line, and an aligner, detect the output of synchrotron radiation light provided on the aligner side outside the synchrotron radiation transmission window of the beam line. A synchrotron radiation monitor is used to control the output of the electron beam accelerating high-frequency cavity in the storage ring and the deflection electromagnet is controlled so that the output of the synchrotron radiation detected by the monitor remains constant based on temporal fluctuations in the output of the synchrotron radiation. 1. A synchrotron radiation exposure apparatus comprising: an arithmetic control circuit that controls the intensity of a deflection magnetic field.