JPS61193449A - Lighting optical device - Google Patents

Abstract

PURPOSE:To facilitate the optical axis-matching for the confirmation and modification of light emission to be performed at the time an excimer laser is used as the light source for illumination by a method wherein a fluorescent plate, by which the invisible light of the excimer laser is converted into a visible light, is provided on the optical path. CONSTITUTION:The beam for alignment to be emitted from a light source 8 is reflected by a beam splitter 9, passes through an objective 10 and illuminates the alignment marks of a mask 5 and a wafer 6. When the beam for alignment emitted from the light source 8 illuminates the visible alignment marks, the beam is reflected by the dark line part of each alignment mark and transmits the parts other than the dark line part. The images of the alignment marks, which are reflected from the mark 5 and the wafer 6, are enlargedly imaged on a fluorescent plate 11, which is optically provided at the conjugate position with the mark 5 and the wafer 6, by the objective 10. The image of the ultraviolet region of the light source 8 is converted into a visible light by the fluorescent plate 11 and the visible light is sent to a visible observation system 13 and a TV camera 14 through a beam splitter 12. The image to be observed by the visible observation system 13 is used for hand-operated positioning.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an illumination optical device, and more particularly to an illumination optical device that uses an excimer laser for exposure and alignment in a semiconductor exposure device that prints fine patterns.

[Prior art]

As integrated circuits become more highly integrated, there is a demand for miniaturization of the minimum dimensions of circuit patterns, which can be met by shortening the printing wavelength of semiconductor exposure equipment. For example, in the case of proximity exposure, the resolved line width becomes smaller in proportion to the square root of the wavelength, and in the case of projection exposure, the resolved line width becomes smaller in proportion to the wavelength. For this reason, it has been proposed to use an excimer laser as a high-intensity light source for printing.

However, since excimer laser light is invisible light, emission cannot be confirmed.

[Purpose of the invention]

The present invention provides an illumination optical device that eliminates the problems of the prior art, uses an excimer laser that emits light in the far ultraviolet region as a light source for illumination, and can easily confirm the emission of the excimer laser light. □The purpose is to provide an illumination optical device that can align the optical axis of an excimer laser.

[Real rattan example]

FIG. 1 shows one embodiment of the present invention, which is applied to a reduction imaging type semiconductor exposure apparatus called a so-called stenper.

In this embodiment, the light source 8 is not only used for alignment i.
This excimer laser is also used for printing (-J). During printing, the alignment microscope 7 for alignment is removed from the position shown in the figure and replaced by a printing illumination system (not shown).

15 is a lens that reduces and images the pattern of the mask 5 on the wafer 6F, and 16 is a wafer mounting table movable in a plane perpendicular to the optical axis.

In this embodiment, the light source 8 is used for both alignment and printing, which is advantageous in terms of cost and space compared to providing separate light sources, and also because the alignment light and printing light have the same wavelength. There is no need to consider the chromatic aberration of the lens 15.

Note that since the excimer laser is a pulsed laser that emits light for an extremely short period of time, the wafer mounting table 16 does not cause each chip 4η to stop during step-repeat baking.
Continuous feeding is possible.

Now, regarding the alignment before the inspection, see Figure 2 (A) (B).
) Mask 5 having alignment marks as shown in
Then, the wafer 6 is aligned using an alignment microscope 7.

In the alignment microscope 7, a beam splitter 9 is disposed along the optical path of the light source 8.
An objective lens 10 for ultraviolet rays is arranged along the optical path that can be reflected by the ultraviolet rays.

The above-mentioned objective lens 10. A beam splitter 9 is arranged,
Along the optical path transmitted through the beam splitter 9, a fluorescent plate 1
1. A beam splitter 12 is arranged. Fluorescent plate 1
1 is an alignment member 1: a microscope 41a is placed on the magnified image plane of the objective lens 10 of the stirrup 7. The light reflected by the beam splitter 12 is sent to a visual observation system 13, while the transmitted light is sent to a television camera 14.

The mask 5 and wafer 6 are shown in FIGS. 2(A) and (B).
As shown in FIG. 2, alignment marks are provided in pairs in order to detect positional deviations in the rotational direction. In order to detect this pair of marks, the beam splitter 9, objective lens 10, and fluorescent plate of the alignment microscope 7 are used. 11, beam splitter 12, visual observation system 13, television camera 14
are configured, for example, in pairs in a direction orthogonal to the drawing. In this case, the light from the light source 8 is split into two by a splitting prism, etc.
The beam enters the beam splitter 9.

In addition, instead of installing two television cameras 14, as in a series of two cameras, the observation fields of two alignment marks that form a pair are combined into one.
It is also possible to observe with a television camera.

In the above configuration, the alignment beam emitted from the light source 8 is reflected by the beam splitter 9 and passes through the objective lens 10.
, and illuminate the alignment marks on the mask 5 and wafer 6, respectively.

When the alignment beam emitted from the light source 8 is incident on the visible alignment marks as shown in FIGS. 2(A) and 2(B), it is reflected by the black edge of each alignment mark.
The alignment mark image reflected from the mask 5 and the wafer 6 is magnified by the objective lens IO, and is transmitted through areas other than the black line portion, and is reflected from the mask 5 and the wafer 6 onto the fluorescent plate 1142, which is provided at a position optically conjugate with the mask 5 and the wafer 6. image is formed.

An image in the ultraviolet region of the light source 8 is converted into visible light by a fluorescent plate 11, and sent via a beam splitter 12 to a visual observation system 13 and a television camera 14, respectively. 1] The image observed by the visual observation system 13 is used for manual alignment.

To explain the alignment here, in FIG. 2(A), the mask 5 has a mark 5a1 consisting of two black edges of two pieces parallel to each other and tilted at 45 degrees in the horizontal direction.

Page 5b also has marks 5a, 5b consisting of two parallel black lines in a direction perpendicular to marks 5a, 5bI.
Marks 5a and 5a2 constitute one alignment mark, and marks 5b and 5b2 constitute the other alignment mark.

Also, each mark 5al of the mask 5 is placed on the wafer 6.

5a2. Compatible with 5bl, 5b2 L Corelani 8
Alignment mark 6al consisting of a single parallel black line
, 6a2. 6bI and 6b2 are removed.

Then, during manual alignment using the visual observation system 13, the alignment marks 6a, 6a of the wafer 6 are
2, eb, , 6b2 respectively as alignment marks 5a1, 5a2 . 5bl.

The mask 5 and the wafer 6 are relatively displaced so that they are located parallel to each other approximately in the middle of the mask 5b2.

On the other hand, in automatic alignment using the television camera 14, the television scanning lines s and s' are electrically scanned as shown in manual alignment, and the scanning time between each black line is 1. ．． 12.

t3 ・t4 ・t'l ・t'2゛・t'3 ・
t'4 is detected, and if they are not all equal, a position correction signal is output according to the deviation, and finally the scanning time jl +L2 +t3 +'4 +t'I +
Make all j'2 +t'3 +t'4 equal.

In Figure 1, the light-shielding plate 17 is used to mask 5
．． An opening is provided at a position corresponding to the alignment mark portion so that only the alignment mark portion of the wafer 6 is irradiated.

Here, 18 is a fluorescent plate for checking the emission of the excimer laser and aligning the optical axis, and is provided at an arbitrary position in the optical path of the excimer laser light passing through the beam splitter 9. Although the excimer laser light is invisible light, when the fluorescent plate 18 is irradiated with the excimer laser light, it becomes visible and light emission can be confirmed. Also, the objective lens 10 of the light source 8. The optical axis of the lens 15 can be aligned with the optical axis by, for example, fixing a pinhole plate in front of the exit of the light source 8, and drawing the excimer laser light passing through the pinhole of the pinhole plate on the surface of the fluorescent plate 18. This is done so as to match the center point, which is the intersection of the crosshairs that serve as indicators.

For convenience'-1 Although FIG. 1 shows that the fluorescent plate 18 is used for visualization when the light source 8 is used for alignment, it is also shown that the fluorescent plate 18 is used for visualization when the light source 8 is used for printing. It goes without saying that the fluorescent plate 18 is used for visualization.

In that case, during printing, the alignment microscope 7 is removed from the position shown in FIG. 1 and replaced by a printing illumination system (not shown).
A beam splitter corresponding to the beam splitter 9 in FIG. 1 is provided to split the illumination optical path for printing, and a fluorescent plate 18 in FIG. 1 is provided in the optical path branched by the beam splitter.

In the figure, the beam splitter 9 used for bending the illumination optical path also serves as the beam splitter for optical path branching required to provide the fluorescent plate 18, but the invention is not limited to this. A beam splitter may be provided and a fluorescent plate 18 may be provided on the optical path reflected by the beam splitter.

Note that the present invention is applicable not only to the projection type semiconductor exposure apparatus shown in the figure but also to so-called contact and proximity type semiconductor exposure apparatuses.

〔effect〕

As described above, according to the present invention, when using an excimer laser as a light source for illumination, it is possible to easily confirm light emission and also to align the optical axis.

If an excimer laser is used for exposure in a semiconductor exposure device, the resolution line width of a circuit pattern will become smaller, and if it is used for alignment, the diffraction angle of each order of diffracted light will become smaller as the wavelength becomes shorter. Alignment with constant numerical aperture (NA)] - It is possible to increase the alignment signal output by increasing the amount of diffracted light taken into the optical system, that is, taking in higher-order diffracted light, thereby increasing the alignment accuracy by 1.

[Brief explanation of drawings]

Figure 2 (A), (B), and (C) □ Figure 2 is an explanatory diagram of the alignment of a mask and a wafer. In the figure, 5 is a mask, 6 is a wafer, 7 is an alignment microscope, 8 is a light source (excimer laser), 9 is a beam splitter, lO is an objective lens, and 11° and 18 are fluorescent plates.

Claims (1)

[Claims] 1. An excimer laser for illuminating an object; a beam splitter for forming an optical path branched from the illumination optical path;
provided in an optical path branched by the beam splitter,
An illumination optical device comprising a fluorescent plate that visualizes the invisible light of the excimer laser. 2. The illumination optical device according to claim 1, wherein the fluorescent plate is provided with an index for aligning the optical axis of the excimer laser.