JP3486206B2 - Excimer laser window - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a window for taking out laser light mounted in a laser chamber of an excimer laser.

[0002]

2. Description of the Related Art FIG. 6 shows a general excimer laser device, in which a window 2 for extracting laser light is provided on both sides of a laser chamber 1 in which a laser medium gas is sealed.
a and 2b are mounted. Inside the laser chamber 1, excitation electrodes 3a and 3b are provided, and a rear mirror 4
The laser light L oscillated using the resonator composed of the front mirror travels as shown by the dotted line in the figure.

The excimer laser is a laser that mainly emits ultraviolet rays, and the window is usually made of a material that transmits ultraviolet rays, such as calcium fluoride (CaF2) or magnesium fluoride (MgF2). However, since these are extremely brittle crystal materials, a metal seal cannot be used as a seal for sealing the laser medium gas in the laser chamber 1, and a rubber O-ring is usually used.

FIG. 7 shows the details of a conventional window portion. The window 2 is a window holder 7a,
It is attached to the laser chamber 1 by 7b.
A rubber O between the window holder 7a and the window 2
A ring 6 is interposed and the O-ring 6 seals the laser medium gas. In addition, the opening portion of the portion through which the laser light L is transmitted is circular.

[0005]

Here, since the laser medium gas sealed by the O-ring contains a halogen gas (hydrogen chloride or fluorine) having a very high reactivity, the O-ring is usually made of a material. Fluorine rubber that is resistant to halogen gas is used. However, even when such a material is used, the halogen gas reacts with the O-ring to generate an impurity, which causes a reduction in the laser output, although it is slight.
Further, as described above, since the window material has low mechanical strength, it is impossible to use a material such as a metal seal that is completely resistant to halogen gas.

Further, since the window has a low mechanical strength, it is difficult to use a window that is too large. Normally, a window that is slightly larger than the circular opening through which the laser beam passes is used. Therefore, as shown in FIG. 8, the O-ring closely contacted with the outer peripheral portion of the window is irradiated with the ultraviolet light multiply reflected on the front surface and the back surface of the window without being much attenuated, and the reaction is accelerated, More impurities are generated.

The present invention has been made in view of the above circumstances. For the excimer laser, the O-ring is structured so that it is hard to be irradiated with ultraviolet light, thereby suppressing the generation of impurities and extending the life of the laser medium gas. Intended to provide a window.

[0008]

Therefore, according to the present invention, in an excimer laser device in which a window for taking out laser light is attached to a window holder attached to a laser chamber through an O-ring, the window and the window are provided. A ring-shaped light-shielding member is provided on the inside of the O-ring in the gap between the holders.

That is, in the present invention, by providing a light-shielding member inside the O-ring in the gap between the window and the window holder, the ultraviolet light generated by the laser and the discharge is reflected directly on the window or the window holder and reflected on the O-ring. It is designed to prevent irradiation.

Further, according to the present invention, in an excimer laser device in which a window for taking out a laser beam is attached to a window holder attached to a laser chamber via an O ring, the window is attached via a circular O ring. It is characterized in that it is attached to the holder and the shape of the opening in the window holder is a rectangle corresponding to the excimer laser beam shape.

In the present invention, the window is attached to the window holder via the circular O-ring, and the shape of the opening in the window holder is a rectangle corresponding to the excimer laser beam shape. As a result, a circular O-ring is arranged around the rectangular opening, and the distance between the long side of the opening and the O-ring becomes longer than in the conventional case. Therefore, between the long side portion of the hole and the O-ring, the number of times of multiple reflection in the window increases, so that the laser light is further attenuated and then radiated to the O-ring.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the embodiments shown in the accompanying drawings.

FIG. 1 shows an embodiment of the present invention.
1 is a laser chamber, 2 is a circular metal window, 6
Is a rubber O-ring, and 7a and 7b are window holders. The window holders 7a and 7b are made of a light-shielding material.

In the case of FIG. 1, a gap 10 is provided between the window 2 and the window holders 7a and 7b to prevent the window 2 from being damaged. In the case of such a configuration, if nothing is interposed in the gap 10, the ultraviolet light will be irradiated to the O-ring 6 from the gap 10. Therefore, in this case, in order to prevent this, the ring-shaped light shielding member 9 is arranged inside the O-ring 6. The light-shielding member 9 is made of a material having flexibility in the same direction as the O-ring 6 is crushed. It has the role of preventing the irradiation of light.

Next, FIG. 2 shows another embodiment of the present invention. In addition, in FIG. 2, (a) is a cross-sectional view of the window portion, (b) is a cross-sectional view taken along the line AA ′ of (a), and (c) is a cross-sectional view taken along the line BB ′ of (a). .

That is, in the embodiment shown in FIG. 2, the opening portions 8 of the window holders 7a and 7b are formed into a rectangular shape instead of the conventional circular shape. That is, the beam profile of the excimer laser has a substantially rectangular shape, and the openings of the window holders 7a and 7b are rectangular according to this shape. Further, the dimensions of the rectangular opening 8 are also
It is slightly larger than the size of the excimer laser beam profile.

In addition, the window holders 7a, 7b
2 has a circular window 2 attached thereto through an O-ring 6. The O-ring 6 has a circular (annular shape) surrounding the opening 8 of the window holders 7a and 7b as shown in FIG. 2 (c). ) Is present. The above window holder 7
The a and 7b themselves are made of a light-shielding material.

According to this structure, as shown in FIG. 2 (c), the distance between the long side end of the opening 8 and the O-ring 6 can be changed without changing the size of the window 2 itself. Since d is mostly longer than in the conventional case, and window holders 7a and 7b made of a light-shielding material are interposed in this portion, as shown in FIG. The number of times of multiple reflections within the window 2 before the O-ring 6 is irradiated by the multiple reflections is increased, and the intensity of the light applied to the O-ring 6 is reduced. Therefore, according to this device, the laser medium gas and the O
The reaction with the ring 6 is suppressed. Incidentally, FIG. 3B shows the irradiation of the laser light to the O-ring 6 by the conventional device, and the number of multiple reflections within the window 2 is obviously smaller than that of the present device.

FIG. 4 is a graph showing the generation of CF4, which is an example of impurities, in which the horizontal axis represents the laser oscillation time and the vertical axis represents the CF4 concentration. As is clear from this figure, the CF4 concentration of this device can be made lower than that of the conventional device.

FIG. 5 is a graph showing the change in the laser average output with respect to the laser oscillation time. As is clear from this figure, the present device has less decrease in the laser average output than the conventional device. can do.

In the embodiment, the window holder 7
Although a and 7b themselves are made of a light-shielding material, a light-shielding material may be applied to the surfaces of the window holders 7a and 7b, and further, the window surface other than the opening 8 is shielded from light. May be applied.

Furthermore, the O-ring 6 of the window 2
It is also conceivable to vapor-deposit an aluminum film for preventing the transmission of ultraviolet light on the contact surface with and to further vapor-deposit an antioxidant film thereon.

Of course, in the above-mentioned embodiment, if the window material has mechanical strength, the window diameter should be increased as much as possible so that the distance between the O-ring and the laser beam becomes longer, and the ultraviolet light irradiated to the O-ring will be more diffused. Can be attenuated.

[0024]

As described above, according to the present invention,
In order to reduce the laser light and ultraviolet light radiated to the O-ring,
Generation of impurities is suppressed, and the life of the laser gas can be extended.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a sectional view showing another embodiment of the present invention.

FIG. 3 is a diagram comparing an embodiment of the present invention with a conventional technique.

FIG. 4 is a diagram showing a change in CF4 concentration corresponding to a laser oscillation time.

FIG. 5 is a diagram showing a change in laser average output corresponding to laser oscillation time.

FIG. 6 is a diagram showing a schematic configuration of an excimer laser.

FIG. 7 is a diagram showing a conventional technique.

FIG. 8 is a view showing a mode in which an O-ring is irradiated with ultraviolet light by multiple reflection in a window.

[Explanation of symbols]

1 ... Laser chamber 2 ... window 3 ... Excitation electrode 4 ... Rear mirror 5 ... Front mirror 6 ... O-ring 7 ... Window holder 9 ... Ring-shaped light-shielding member 10 ... Gap

Continuation of front page (56) Reference JP-A-3-273691 (JP, A) JP-A-3-72687 (JP, A) JP-A-63-229880 (JP, A) JP-A-61-203689 (JP , A) JP-A-1-231017 (JP, A) JP-A-3-293787 (JP, A) Actually opened 62-158851 (JP, U) Actually opened 59-6261 (JP, U) Actually opened 61-151359 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01S 3/00-3/30

Claims (2)

(57) [Claims] 1. An excimer laser device in which a window for taking out laser light is attached to a window holder attached to a laser chamber via an O-ring, wherein the O in a gap between the window and the window holder.
An excimer laser window, characterized in that a ring-shaped light-shielding member is provided inside the ring. 2. A window for taking out laser light is attached to a window holder attached to the laser chamber.
In an excimer laser device mounted via a ring, the window is mounted on the window holder via a circular O-ring, and the shape of the opening in the window holder corresponds to the excimer laser beam shape. Excimer laser window characterized by a rectangular shape.