JPS62266532A - Illuminating optical system - Google Patents

Abstract

PURPOSE:To effectively utilize a light flux from a light source, to improve light converging efficiency and to uniformly illuminate a surface to be illuminated, by arranging at a part of light converging system a lens which mainly generates an introvert comatic aberration. CONSTITUTION:A light converging optical system 4 converges a light source image formed in the vicinity of the 2nd focus into a position in the vicinity of a field lens 5 and makes the image incident upon the left end face of an optical integrator 6 for forming many light fluxes with uniform light distributing characteristics. A meniscus-shaped lens 4A for mainly generating an introvert comatic aberration is arranged on a part of the optical system 4 so that the center of curvature of the lens surface is positioned in the 2nd focus direction where the light source image based upon an elliptic reflector 2 is formed. Consequently, peripheral light fluxes among illuminating light fluxes can be prevented from vignetting and utilized as illuminating light and the light converging efficiency can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an illumination optical system suitable for a semiconductor printing apparatus for producing integrated circuits by projecting and printing fine patterns such as electronic circuits onto a surface. In particular, the present invention relates to an illumination optical system that aims to effectively utilize the luminous flux from a light source.

(Prior Art) Recent semiconductor manufacturing technology requires phosphorography technology that can form thin, high-density circuit patterns for IfJ integration of IT electronic circuits.

Generally, when a circuit pattern t on a mask or reticle surface is transferred onto a wafer surface, the resolution line width of the circuit pattern transferred onto the wafer 1M is proportional to the wavelength of the light source. For this reason, far ultraviolet light (with a wavelength of 200 to 300 n7y1) has traditionally been
Ultra-high pressure mercury lamps, xenon mercury lamps, etc. that oscillate at short wavelengths (in the deep UV region) are often used.

In addition, when it comes to baking and exposing wafers and surfaces in semiconductor manufacturing, the light collection efficiency is improved and the baking is uniform over the entire surface! S
In order to control the original and physical optical effects, it is required that the illumination light beam onto the mask surface has a constant divergence angle. For this reason, conventionally, using a light source of #i, V, +, brightness, a so-called optical inch grater and a condenser lens consisting of a lens array called a prior eye lens, an optical fiber end, etc. are used to connect the condensing optical system and the wave surface. Use average - total predetermined amount of illumination and luminous flux spread 1'j
The illumination optical system consists of an integrated illumination optical system.

Among these, the so-called contact/rel where the mask and wafer are printed with a distance of about 7# or several tens of microns apart.
+ In the shimity exposure method, the condenser lens is formed to have an Ij4t-infinity connection with an optical integrator. Also, is there a projection optical system on the pattern T-way surface of the mask existing in the stepper? In the glossejection exposure method, a condenser lens is used to form the entire image of the optical inch grater at the incidence 1 of the projection system.
V. I'm doing it.

However, these illumination optical systems are configured. X
1 of Genji Keiki's effective diameter and various elementary aberrations, etc.? Due to the tatami mats, the peripheral light flux of the illumination light flux is distorted, and much of it is not used as illumination light, which reduces the light collection efficiency (as a result, the throughput rate)1 decreases. Improving the light collection efficiency in the illumination optical system is achieved by using G-absorbing resist or CgL (
Contrast Enchancament Lag
The present invention aims to effectively utilize the luminous flux from the light source, which has recently become a particularly important issue due to the use of The purpose of printing is to provide an illumination optical system suitable for the device.

(Means for solving the problem) All light is placed near the first focal point of the transom reflector, and the light beam from the light source is guided to an optical inch grater by a total focusing optical system, and then exits from the optical inch grater. Is the irradiated surface using the entire luminous flux? In the illumination optical system that emits light, a lens that causes inward comatic aberration is disposed in a part of the condensing optical system.

Other features of the invention are described in the Examples.

(Embodiment) FIG. 1 is a schematic diagram of an optical system of an embodiment applied to a contact/pro-kikumitei exposure apparatus, which is one of the all-semiconductor manufacturing methods of the present invention.

In the figure, reference numeral 1 denotes a light source, for example, an ultra-high pressure mercury lamp. Reference numeral 2 is an in-column reflector with two sources 1 placed near the first focal point, and the light beam from the 1 light source 1 is condensed near the field lens 3 placed near the second focal point of the circular reflector 2. ing. 4 is a condensing optical system, and is an optical inching grater for condensing light near the i#9 T-field lens 5 formed near the second focal point and forming a large number of light beams with uniform one-element characteristics. The light is incident on the left end face of 6. Reference numeral 7 denotes a collimator lens for illuminating the target lflR4mB' using the multiple light beams formed by the optical inching grater 6.

In this embodiment, a meniscus-shaped lens 4A that causes inward comatic aberration is installed in a part of the d condensing optical system 4, especially in the direction of the second focal point where the light source image is formed by the column reflector 2. The center of the vehicle is positioned on the surface. This is K
It prevents vignetting of the peripheral luminous flux of the illumination luminous flux so that it can be used as illumination light.

fir, 2J! ;Q is a transverse aberration diagram of the condensing optical system 4 at this time.

FIG. 3 is a spot diagram at the optimum image plane of the condensing optical system 4, where the figure shows the light flux on the optical axis, and the figure 3 shows the light flux at the farthest off-axis.

FIG. 4 is an explanatory diagram of the strong vW distribution of the light source image at the second focal point of the column reflecting mirror. As shown in the figure, the intensity distribution of the light source image is approximately a Gaussian distribution.

Generally, it is preferable if all of the wide and t luminous flux at this time can be utilized.

However, in reality, the peripheral light beam is mainly limited by the effective diameter of each optical element, and is vignetted due to the influence of various aberrations of the optical system.

That is, in FIG. 4, the part used as the actual illumination light beam is the area P indicated by diagonal lines in the figure, and the part Q is shredded by the illumination optical system and does not enter the illuminated surface. Therefore, in this embodiment, the lens shape 1 of some lenses of the condensing optical system is added so that this range Q12) is included in the range P, and the inward coma aberration is completely generated as shown in FIG. 3 (5). This is achieved by making

As a result, the incident light tt on the irradiated surface is increased without increasing the light l1kt of the light source, thereby increasing the light collection efficiency.

In the face tree embodiment, in order to effectively utilize the peripheral light flux of the illumination light flux, the lens that generates inward coma aberration in the condensing optical system is not limited to a meniscus shape, but any lens shape can be used as long as the front and rear optical systems are controlled. It is possible even if the

(Effects of the Invention) According to the present invention, an illumination optical system suitable for a semiconductor exposure apparatus capable of effectively utilizing the luminous flux from the light source, improving the light collection efficiency, and uniformly illuminating the irradiated surface is achieved. be able to.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an optical system according to an embodiment of the present invention.
FIG. 3 is an explanatory diagram of a convergence diagram and a spot diagram of the condensing optical system according to the present invention. FIG. 4 is an explanatory diagram of the intensity distribution of the light source image at the second focal plane of the Kawauchi reflector according to the present invention. It is a diagram. In the figure, 1 is a light source, 2 is a Kawauchi reflector, 3.5 is a field lens, 4 is a condensing optical system, 6 is an optical inch grater, 7 is a collimator lens, and 8 is an irradiated surface.

Claims (2)

[Claims] (1) A light source is placed near the first focal point of the elliptical reflector, the light flux from the light source is guided to an optical integrator by a condensing optical system, and the light flux emitted from the optical integrator is used to illuminate the illuminated surface. 1. An illumination optical system for irradiating an object, characterized in that a lens that mainly generates inward comatic aberration is disposed in a part of the condensing optical system. (2) A patent claim characterized in that the lens has a meniscus shape and is arranged with the center of curvature of the lens surface facing the second focal direction of the elliptical reflector where a light source image is formed by the ellipse reflector. The illumination optical system according to item 1.