JPH031436A - High efficiency excimer discharge lamp - Google Patents

Abstract

PURPOSE:To provide a high efficiency excimer discharge lamp by allowing a mixture gas producing excimer to undergo electric discharge, and taking out the natural emitting light from the produced excimer molecules without oscillation excimer laser. CONSTITUTION:A mixture gas of F, Kr, and He is encapsulated in an excimer discharge tube 10 made from a quartz tubing having a high penetrativity for ultraviolet rays at a pressure lower than the pressure for laser oscillation. The power supply for electric discharge is composed of a pulse shaper circuit consisting of capacitors C0-C6 and coils L1-L8, a high voltage switch 11, and a high voltage charger 1. When the pulse shaper circuit is charged by this charger 1 and the switch 11 is closed, a voltage with pulse width determined by the pulse shaper circuit is impressed on the discharge tube 10, and glow discharge is started. At this time, a light emission energy proportioned to the discharge input is obtained, and its light emission efficiency will attain 10%.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a highly efficient light source discharge lamp with selectivity in the emission spectrum, and in particular, uses a rare gas excimer, rare gas halide, etc. as a light emitting medium. This invention relates to an excimer discharge lamp for a light source that utilizes the spontaneous emission of excimer, mercury halide excimer, and halogen molecule excimer.

(Prior Art) In photochemical processes, printing, etc., there is a need for a light source that has wavelength selectivity ranging from the visible region to the ultraviolet region and high efficiency.

Xenon flash lamps, krypton flash lamps, and low-pressure mercury lamps, which emit light from the visible region to the ultraviolet region, are known as conventional general incoherent light sources.

Xenon flash lamps and kryptonian flash lamps utilize light emission from ablative arc discharge plasma. In the case of xenon flash lamps (xenon 390↑orr), as shown in Figure 7a In the case of a krypton flash lamp (krypton 700 Torr), as shown in FIG. 7, the emission spectrum width is extremely wide, and it is black body radiation and has no wavelength selectivity.

Low-pressure mercury lamps use elementary electrode or electrodeless glow discharge plasma to emit light from the electronic excitation level of mercury atoms or monovalent positive ions, and because it has a low-pressure atomic spectrum, As shown in Figure 9a for a wave discharge mercury lamp, and as shown in Figure 9b for an elemental electrode HID mercury lamp, the spectral width is narrow, but
From the visible region to the ultraviolet region, for example, 589,43
El, 435.408.365,312,297,25
4n+s and several tens of water spectra appear, but the intensity of each spectrum is extremely small.

In addition, halogen lamps have been known for some time, but halogen is not used for gas discharge, but is used to prevent lamp blackening, and does not contribute to wavelength selectivity at all. The emission spectrum is black body radiation, and is
The spectrum of the band structure of the gen excimer is not shown.

On the other hand, discharge-excited excimer lasers have been known as coherent light sources ranging from the visible region to the vacuum ultraviolet region.This discharge-excited excimer laser is highly monochromatic and has excellent light-gathering properties, but its output is low. The laser pulse width is extremely short at 30 to 50 ns, and the electrical efficiency is extremely low at 1%.Moreover, advanced and complex excitation techniques such as high current density discharge and pre-ionization technology are essential for excimer laser discharge excitation. Furthermore, an expensive optical system for the excimer laser resonator was required.

In addition, xenon (Xe) and krypton (K
r)・As a device for operating a flash lamp light source,
A device shown in FIG. 8 is known.

As shown in FIG. 8, a high voltage power source 1, a capacitor 2 charged by the high voltage power source 1 via an impedance,
The electric charge charged in this capacitor 2 is transferred to the inductance 3
and a circuit for applying the pulse output of the pulse generator 6 to the trigger terminal of the flash tube 8 via the pulse transformer 7. Note that 5 is a simmer circuit for facilitating the start of discharge.

The flash tube 8 is made of quartz tube and has a diameter of 300~7
00 Torr of xenon gas or krypton gas is sealed, and when a high voltage is applied through the gate 4, an arc discharge occurs.

The emission spectrum in this case is a black body radiation determined from the arc plasma temperature, as shown in FIGS. 7a and 7b, and there is no major difference due to the difference in filler gas between Cannon and Krypton.

Furthermore, as shown in Figure 9a and b, the emission spectrum of a conventional low-pressure mercury glow discharge lamp includes a large amount of mercury in both microwave discharge (electrodeless discharge) and direct current discharge (element electrode discharge). A line spectrum appears, and there is no major difference based on the difference in discharge method.

In the case of a discharge excited excimer laser, e.g. XeCI excimer, Xe/HCI/He=1-210.1/99
A high-pressure mixed gas of 2 to 4 atmospheres (X) is sealed in the chamber to cause a spatially -like avalanche discharge.

Laser oscillation requires advanced pre-ionization technology and lateral discharge technology. In order to exceed the threshold gain of laser oscillation, approximately 4 GW of power must be injected per discharge body AL, and the output pulse width is also 30 to 50 nsec.
This is extremely short, making it difficult to make long pulses due to the instability of the discharge.

Also, since laser oscillation is determined by laser gain and absorption, oscillation cannot be achieved in a medium with a lot of absorption. For example, in AlCl, KrC1, NeF, etc., oscillation is extremely weak or does not oscillate, generally The efficiency of discharge-pumped excimer lasers is about 1% at most.

Figures 10 to 13 show XeF, XeC1, KrF, Ar
For each excimer of F, as shown by comparing the oscillation spectrum a for laser oscillation and the spectral distribution of spontaneous emission light, the spectrum is narrower for laser oscillation in both cases; Also improves light gathering ability.

Conventional incoherent lamps do not have high light source efficiency, wavelength selectivity, and pulse width selectivity.

On the other hand, the excimer laser, which is an ultraviolet coherent light source, has a short pulse width of 30 to 50 ns and an electrical efficiency of 1%.
Furthermore, to a lesser extent, laser oscillation has not been able to provide a highly efficient light source with long pulse widths or continuous operation.

(Means for Solving the Problems) This invention was devised to solve these problems, and it uses laser oscillation to control the pressure of a mixed gas sealed in a transparent discharge tube at the emission wavelength of the excimer. By selecting a pressure lower than that used for the laser and using electrical discharge, we reduce collisional deexcitation of the excimer and also reduce the absorption of the medium at the emission wavelength, resulting in an internal efficiency that far exceeds that of conventional excimer lasers. This enables high efficiency operation with an efficiency of 105 or more.

Wavelength selectivity is achieved by selecting a gas mixture that selectively generates various excimers, and selecting AC discharge, including DC discharge, pulsed t[, and high-frequency discharge by microwaves and radio waves, as the excitation discharge. A light source can be obtained.

(effect) The spontaneous emission lifetime of light is proportional to the cube of the wavelength.

Therefore, for an excimer with a wavelength of 308 to 193 nm,
The spontaneous emission lifetime is less than 1 onsec. Therefore, in the present invention, low pressure operation is selected to actively increase the spontaneous emission efficiency, thereby increasing the luminous efficiency.

Therefore, low-pressure discharge eliminates the need for advanced pre-ionization and high-power discharge technology used in excimer laser discharge, expanding the range of discharge methods and operating conditions, and allowing the use of conventional low-pressure discharge technology. .

By excitation of such a mixed gas, noble gas excimer,
Generate noble gas halide excimer, mercury halide excimer, and halogen molecule excimer, and efficiently emit spontaneous light from the transition from B level to X level (D+A transition for halogen molecule excimer). Occur.

According to a theoretical analysis using the excimer discharge lamp simulation 1 code, which consists of the excitation electric circuit equation, the Portzmann transport equation for electrons during discharge, and the chemical reaction equation,
It has been found that high efficiencies of over 10% can be obtained with KrF excimer lamps. Efficiency of about 10% can also be obtained with other excimers.

A desired emission pulse width can be obtained by selecting the excitation power source, and both high efficiency and spectral selectivity of the light source can be achieved.

(Example) The example shown in Fig. 1 is an excimer discharge excitation power source.
Pulse power is used.

The excimer discharge tube 10 is made of a quartz tube with high transmittance for ultraviolet light, and has a diameter of 50 cm and a length of 15 cm.
A mixed gas of 34 ($) was sealed at 75 Torr, and the discharge electrode was composed of a metal electrode with a diameter of 1.50 square meters, and the electrode spacing was 12 c+s. The discharge power source includes a pulse shaping circuit, a high voltage switch 11, and a high voltage charger 1. The output pulse width of the pulse shaping circuit is variable, but in this example, it is composed of a six-stage LC circuit consisting of capacitors CO to CB and inductances 1 to L8, and the capacitance per stage is 20.4 nF. , the inductance is 8.3JIH.

When the pulse shaping circuit is charged with the DC high voltage charger 1 and the high voltage switch 11 is closed, a voltage with a pulse width determined by the pulse shaping circuit is applied to the excimer discharge tube 10, and glow discharge is started.

FIG. 2 shows the discharge current, discharge voltage, and excimer emission waveform at a wavelength of 248n++ when the charging voltage is L8KV.

A light emission pulse width with a duration of 2.7 psec was obtained, the light emission efficiency was 10%, and the spectral width was 10n+s.In the embodiment described above, the excimer discharge tube is excited by a pulsed power source. However, the present invention is not limited thereto, and can be used in all other excimer discharge tubes, including DC discharge and high-frequency discharge.

Figure 3 shows a DC discharge excited excimer lamp, Figure 4 shows a commercial frequency AC discharge excited excimer lamp, Figure 5 shows a radio wave (RF wave) discharge excited excimer lamp, and Figure 6 shows a microwave discharge excited excimer lamp. A schematic diagram of the lamp is shown in each case.

In radio wave discharge and microwave discharge, the discharge tube can be electrodeless and there is no halogen corrosion, so the life of the excimer gas can be expected to be extended.

In addition to quartz, the lamp may be constructed of a chamber made of sapphire, calcium fluoride, magnesium fluoride, lithium fluoride, or the like, or a gas chamber with an optical window; however, the shape of the lamp chamber is not particularly relevant.

In the case of pulse discharge, the optical output can be increased by high repetition pulse discharge.

Excimer gas can be used for a long time by being shut off or cooled and repurified using a gas circulator.

For cooling the lamp, pure water can be used in the case of pulse discharge or direct current discharge with a wavelength longer than the KrF excimer wavelength.

Next, gases used in the high-efficiency excimer discharge lamp of the present invention will be illustrated.

(1) Arz (center spectrum 128 nm), Kr
Noble gas of z (148n■), Xez (172n+s)
The mixed gases of excimer lamps that utilize light emitted from excimers are rare gases (Ar, K, etc.) used to generate excimers.
r, Xe).

(2) NeF (108 nm), ArF (193 nm)
), KrF (248nm), and XeF (351nm), the mixture gas of an excimer lamp that utilizes light emission from a halide excimer is a rare gas (
Me, Ar, Kr, Xe), fluorine (F2) or fluorine compounds (NF3, 5F6) and buffer gas (He
, Ne, Ar, Kr).

(3) ArC1 (175nm), KrGI (222n
m), XeC1 (308 nm) C7) The mixed gas of an excimer lamp that utilizes light emission from a rare gas/halide excimer includes rare gases (Ar, Kr,
Xe), chlorine (C1z) gas or chlorine compound (HCl
, 8C1a, CC14) and buffer gases (He, Me,
Ar) is used.

(4) KrBr (208nm), XeBr (282n
The mixed gas of an excimer lamp that utilizes light emission from a rare gas halide excimer (m) includes a rare gas (Kr, Xe), bromine (Brz) or hydrogen bromide (HBr2) and a buffer gas ( He, Me, Ar) are used.

(5) The mixed gas of the excimer lamp that utilizes light emission from the rare gas-halide excimer of Xe1 (253n layer) is a rare gas (Xe) for excimer generation, and iodine (I
) or hydrogen iodide (Hl) and buffer gas (He, Ne
, Ar).

(8) Hgl (444 nm), HgBr (502 nm)
), HgC1 (558 nm), and HgF (612 nm). , Ne, Ar, Hz).

(7) Fz (157nm), C1z (258nm)
, Brz (292nm), Iz (342n■) The mixed gas of the excimer lamp that utilizes light emission from the halogen molecule excimer is the halogen gas (F2.C1) produced by the excimer.
z, Br2. I2. HI) and buffer gases (He, Ne
, Ar).

(Effects) As explained above, according to the present invention, the same lamp type can have wavelength selectivity in various spectra by simply changing the light emitting medium, and unlike conventional high-pressure excimer lasers, it has low Because of the pressure, it is possible to obtain highly efficient light emission, and compared to lasers, it can be constructed at an extremely low cost, making it extremely useful in practice.

Excimer laser discharge requires a discharge input that exceeds the oscillation threshold, but in the excimer discharge lamp of the present invention, it is possible to obtain luminous energy proportional to the discharge input. Furthermore, unlike excimer laser devices, the discharge lamp of the present invention can easily be made larger in size and output.

Unable or difficult to obtain with laser oscillation, for example,
Highly efficient light emission can be achieved from excimers such as He-F.

Since there is no need for a laser oscillator, there is no need for an expensive laser optical system, and since it is possible to generate long pulses of microseconds or more (or DC), excimer φ of 30 to 50 nsec can be generated.
Compared to lasers, photon utilization efficiency for photochemical reactions is significantly higher. Furthermore, high repetition rates and continuous operation are possible, and the average output (light) can also be increased. The spectral width of this light source is
Since it falls within the range of 1 to 20 nm, the wavelength selectivity of the photochemical process is almost the same as that of a laser.

Therefore, the cost of ultraviolet light photons can be significantly reduced while maintaining wavelength selectivity, and the range of applications of photochemical processes can be greatly expanded.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of a device for exciting a high-efficiency excimer discharge lamp of the present invention, Fig. 2 is a waveform chart showing the operating characteristics of the device of Fig. 1, and Figs. Another circuit diagram of the excitation device. ! Figure s7 is an emission spectrum diagram of a conventional flash lamp, Figure 8 is a circuit diagram of a device that drives a conventional flash lamp, Figure 9 is an emission spectrum diagram of a conventional mercury lamp, and Figures 1θ to 13 are , is an emission spectrum diagram of laser light and spontaneous emission light for various excimers. l...High voltage charger lO...Excimer discharge tube 11...High voltage switch Figure 3 High voltage transformer Figure 4 Figure 5 Figure 6 Factor C0=C1=C2=C3=C4=C5=C6= 20.4
nFLl: L2=L3=L4=L5=L6=L7=L8
=6.3uH Figure 1 ← soon s Figure 2 Figure 1 b Figure 8 (8m) Figure 10 Figure 11 Figure 9 a Figure 9 - Section 13

Claims (1)

[Claims] (1) A high-performance technology characterized in that a mixed gas that generates an excimer is sealed in a discharge tube, the mixed gas is discharged, and spontaneously emitted light from the excimer molecules generated is extracted without causing excimer laser oscillation. Efficiency excimer discharge lamp.