JPH10289688A - Mercury lamp for light source - Google Patents

Abstract

PROBLEM TO BE SOLVED: To uniformize and stabilize the illuminance distribution of a mercury lamp by forming a circular recess sin a central part of a flat end surface for generating arc discharge, of a truncated cone of the mercury lamp having a conical negative electrode and generating the discharge arc in the adjacent to the circular recess. SOLUTION: A discharge point of an arc discharge mercury lamp is set to a limited position of a truncated-cone negative electrode 2, namely, a circular recess is provided in the center of the opposite plane of a positive electrode 1 so that an area thereabout is confined as the arc discharge part. This constitution can remove the instability caused by change in the generation parts of the arc and uniformalize the illuminance distribution so that the device is effectively used for, for example, a manufacturing process of silicon wafers such as a projection exposure device which requires a uniform exposure on a surface coated with sensitive agent through a pattern shape negative.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a mercury lamp for a light source.

[0002]

2. Description of the Related Art In a mercury lamp for a light source based on the principle of generating arc discharge by enclosing mercury vapor, light of a specific wavelength is taken out of the light source through a filter, and this light is converged and passed through a negative having a pattern shape to form a photosensitive material. There is an apparatus that requires uniform exposure on a surface on which a coating is applied. For example, in a manufacturing stage of a semiconductor element of an integrated circuit, a pattern is exposed on a silicon wafer surface coated with a photosensitive material by a reduction projection exposure apparatus or the like.

At this time, if the exposure amount on the exposed surface is not uniform, the result of the next development step is that the photosensitive material remains, or conversely, the unexposed portion is exposed, and the like.
There is an adverse effect that precise micro devices cannot be formed.
This non-uniformity is not caused only by the lamp light source, but since the lamp is replaced frequently, it is necessary to confirm the uniformity of the illuminance each time, and wasteful time is required.

The light source of the mercury lamp utilizes the light of an internal arc discharge. Since the amount of light at this time changes with time, it is devised to change the exposure time to make the exposure constant. . However, there is no means for correcting the non-uniformity of the exposure distribution in the exposure plane. The main cause of the non-uniformity is attributed to changes in the lamp light source. FIG. 2 shows an electrode shape of a conventional lamp. In the discharge of a conventional lamp, an arc discharge occurs between the cathode 2 having a flat surface and the anode 1 having a spherical surface, and this light is used as a light source. Therefore, when the place where the arc is generated changes, the total amount of light hardly changes. Light for exposure using a part of the total light amount had an unstable effect.

[0005]

In the conventional method, the location of the arc discharge is random without the flat surface facing the cathode. Therefore, when a part of the emitted light is condensed and used for exposure, the arc discharge occurs. When the location changes, the amount of light condensed changes, giving rise to the disadvantage that the illuminance distribution on the exposure surface becomes non-uniform.

An object of the present invention is to provide a lamp capable of reducing unevenness and instability of illumination caused by the lamp.

[0007]

The illuminance and the illuminance distribution at the time of exposure are made uniform even if a part of the emitted light is taken out by limiting the place where the arc discharge is generated.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an electrode shape of a lamp according to the present invention. The discharge place of the arc discharge mercury lamp is restricted to a limited position of the cathode 2, that is, in the vicinity of a hollow at the center of the opposite plane of the cathode, and a part of light emitted from the arc is taken out and irradiated on a predetermined surface. Illuminance can be made uniform.

[0009]

According to the present invention, when a part of the light from the light source due to the arc discharge is converged to irradiate a specific surface, the illuminance distribution in the irradiating surface can be made uniform.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a lamp electrode shape according to the present invention.

FIG. 2 is an explanatory view of a conventional lamp electrode.

[Explanation of symbols]

 1 ... Anode electrode, 2 ... Cathode electrode.

Claims (1)

[Claims] 1. A mercury lamp having a truncated-cone shape of a cathode, wherein a circular depression is formed at the center of a flat end surface where a truncated-cone arc discharge occurs, and a discharge arc is formed in the vicinity of the circular depression. A mercury lamp characterized in that the illuminance distribution is stabilized by stabilizing the illuminance distribution.