JPS5850511A - Illumination optical system of integrated circuit pattern transfer device - Google Patents

Abstract

PURPOSE:To make illumination light bright and also to avoid waste, by correlatively moving each lens consisting of the first collimation lens and its front and rear 2 groups, and varying the diameter of a parallel light beam flux emitted from said lens in accordance with size of a mask and a wafer being substances to be irradiated. CONSTITUTION:When light from a light source is led as parallel light beams to a compound eye lens 5 functioning as an optical integrator, a collimation lens 4 for obtaining a parallel light beam flux is constituted of at least 2 groups or 2 pieces, 2 lenses of front and rear groups are moved relatively in a state that its focal position is helt at the second focal position of an oval mirror in order to obtain the parallel light beam flux, and a composite focal distance is varied by varying its inter-main point distance (d). In this way, even if an incident angle (alpha) against the collimation lens group 4 is a constant value, by varying the luminous flux width of incident light to the compound eye lens group 5, it can be irradiated evenly in accordance with an area of a substance to be irradiated.

Description

DETAILED DESCRIPTION OF THE INVENTION - This invention provides a method for manufacturing integrated circuits, generally called IC circuits, by using a photoresist such as This relates to an illumination optical system for projecting light onto an object and exposing it to light.

This type of transfer method using projection exposure includes a contact method (hand-tact method) and a semi-contact method (proximity method).

According to the contact method, in principle, the pattern on the mask can be accurately transferred as is, but in reality, even if the light comes into close contact with the mask or wafer, the original diffraction phenomenon will occur, and that part will be The resolution is lowered due to the influence of the secondary maximum, making it impossible to transfer a sharp pattern image, which tends to cause image disturbances and blurred transfer results. Also, there is the problem that it is easy to damage the mask and wafer when working in close contact with the mask and wafer. Therefore, it is not necessarily an effective transfer means.

As a result, these days, rather than contacting the mask and wafer in an N-contact manner, they are separated by a minute gap of several microns to more than ten microns.
The aforementioned proximity method has been adopted with the idea of preventing damage to masks and wafers that can easily occur due to direct contact, and emitting parallel light beams with as high a degree of parallelism as possible to prevent the effects of light diffraction. ing.

When placing a mask on a wafer and floodlighting the mask and wafer, the following requirements are: 1. The illumination light must be bright and efficient; 2. The illumination must be even and uniform. 3. , to reduce the light diffraction phenomenon as much as possible. .

It is obvious that if the illumination light is dark or the light source light does not reach the heat-receiving surface sufficiently, the transfer work will take time and productivity will be affected, and if the illumination is not uniform, parts may The unevenness will deteriorate the transfer result of the line width of the fine pattern, causing irregularities in the area.To prevent image distortion and unclear projection transfer due to light diffraction phenomenon, masks and Improves the parallelism of the irradiation light that illuminates the wafer,
Minimize the incidence of light other than parallel beams as much as possible.
- jin is required. 7 Lie's eye lenses (fl7
eye 1ens (commonly known as the fly's eye lens)
A convergent compound eye/lens lens is placed, and a large number of secondary light sources are generated at the focal position thereof, and the focus of the second collimation lens is made to match the secondary light source, and the second collimation lens is The light emitted from the light source is converted into a large number of parallel light beams according to the number of secondary light sources using a mask and a wave...
It has already been done that the cost of 7 yuan per 1 yuan is installed on top of the market. Said 2. The new technical means and development for achieving the objectives of 3.0 and 3.0 were disclosed in the patent application (1) filed at the same time.In the present invention, the light from the light source is collimated by the first collimation lens. In order to form a beam of light, all of the elements within the incident angle of the first collimation lens are used effectively, and according to the size of the mask and wafer that are the objects to be irradiated. By changing the diameter of a bundle of parallel rays incident on a compound eye lens as an optical inching grater, as described in 1. The main purpose is to achieve the purpose of 2. above, and the incidental component money is used as a secondary purpose to achieve the purpose of 2. above. and 3.0 purposes. To be more specific, the first elliptical mirror
The light from the light source located at the focal point travels toward its second focal point through the elliptical reflective surface, but the maximum incident angle of the light passing through the second focal plane is determined by the size of the elliptical mirror and the shape of the elliptical reflective surface. It will be done. Also limited by.゛Therefore, it is important to note that for the light that is ultimately projected onto the mask and the wafer, it is important to use all the light within the incident angle that can be incident on the first collimation lens without wasting it, thereby increasing the illumination efficiency. I paid attention. Mask and one, z -・
・In terms of light projection, in the past, many of them were fixed and used ones with a telescopic illumination angle. Even if there is something that can change the irradiation angle, it is a stepwise change, and it is dangerous if the irradiation angle is not always effective for the size of the irradiated surface. For small demon masks and waves, it is useful to reduce the irradiation angle to prevent diffraction phenomena caused by stray light other than perfectly parallel rays. A method was also adopted in which a diaphragm was installed and the aperture diameter was narrowed down. However, in this case, although the irradiation angle can be made smaller by narrowing down the aperture, there is a drawback in that the amount of light is conversely reduced.

Therefore, in the present invention, when guiding the particles from the light source as parallel rays to the compound lens, which is an optical inching grater, a collimation lens for obtaining a bundle of parallel rays is configured with at least two groups or two lenses, and parallel- f
In order to obtain the fi ray flux, the focal position is kept at the second focal position of the elliptical mirror, and these lens groups or lenses are moved relatively. In this case, the diameter of the emitted parallel light beam is reduced to increase the light density and the illuminance per unit area of the irradiated surface is increased to project light of 1 tatami. As a result, the amount of incident light from the elliptical mirror remains constant regardless of the magnitude of the composite focal length of the first collimation lens, and the first collimation lens changes only the diameter of its emitted ray bundle. The amount of light that illuminates the surface can be maintained at the maximum constant amount, and the desired illumination angle can be adjusted by continuously moving the first collimation lens, which is composed of two groups or two lenses, relative to each other as described above. Continuously change the
The lighting effect is optimal depending on the size of the object to be illuminated.

゛Hereinafter, the details of the present invention will be explained with reference to the embodiment shown in the drawings. In FIG. A cold mirror 3 is provided at an angle of 45° with the axis.
As is well known, a cold mirror transmits and emits heat radiation and reflects only effective light. 4 is a first collimation lens group, which has a diverging property in the example shown in the first figure, but may also have a IIcIc property as shown in FIGS. 5A and 5B. In the case shown in FIG. 1, FIG. 4A, and FIG. 4B, the rear focus (1ill of emitted light) is set to coincide with the second focus of the elliptical mirror 2 (light source 1 is the first focus). It is. As a result, it is reflected by the ellipse @ 12, reflected by the cold mirror 3, and exits as the first (D co! Although two single compound lenses are used as the front group lens and the rear group lens, it is of course possible to use a combination of multiple compound lenses as the front group lens and the rear group lens, respectively. Details of the compound eye lens group 5 are shown in FIGS. 2A, 2B, and 3.
Illustrated with a diagram. In the case shown, 1 each! ! The eye lens is the second
As can be understood from Figure A, it is composed of a fly's eye lens consisting of a large number of single small lenses formed by connecting rows of squares when viewed from the front. The lenslets are composed of a regular hexagonal arrangement...They are formed by a combination of bicam-shaped (honeycomb) lenslets, and from the book, both fly-eye lenses and honeycomb lenses are collectively called. \So? It is called the J-eye lens, and these two groups are called the optical inch grater.Then, each single lens element of the front group or the first compound eye lens on the side closer to the first collimation lens group 4 is As shown in FIG. 3, it must be located on the common optical axis In each single lens element of the I lens and each single lens element of the rear group or second compound lens, the convex surface with a small radius of curvature is on the incident light side, that is, the light source 1.
It is located facing the direction of The focal length f1 of each single lens element of the front group or the first compound eye lens and the focal length f2 of each single lens element of the rear group or the second compound eye lens do not need to have strictly equal values; They may be approximately equal values. It is desirable that the distance between the principal points of these six pairs of lenses satisfy the following relationship.

The reason for setting f1=f2 t or approximation fl-f2 is that the six lens elements are formed of convergent lenses,
Coupled with the condition that each convex curved surface with a small radius of curvature faces the incident light side, whether it is formed by a plano-convex lens, a biconvex lens, a cylindrical lens, or a meniscus lens, spherical aberration is reduced and the light intensity distribution is improved. This is because it is possible to achieve uniformity of the illumination, and it is useful for providing more uniform illumination than when using a single compound eye lens. In addition, by positioning each lens within the range 4 shown in the above formula regarding the distance between the principal points of the two lenses, the effect as a field lens is exhibited, and the amount of light is increased by directing the amount of light at the periphery toward the center. This is because it is useful for providing a lighting effect with less unevenness. 6 is a plane mirror for changing the direction of light from a large number of secondary light sources formed by the compound lens group 5 as an optical inteder, and 7 is a convergent second collimation lens. be.

In this case, in order to uniformly project light from the m2 flimation lens 7t4 into parallel rays onto the mask 8 and way/~9 located below, the rear @ focal point and the second lens IJ are formed by the compound lens group 5. It is desirable to match the front focal point of the lens 7.

According to the above configuration, the parallel rays emitted by the first frimation lens group 4 enter the compound eye lens group 5,
The second collimation lens 7 is divided into a number of secondary light sources corresponding to the number of single lens elements formed by the same lens group, and even if the amount of light incident on the compound eye lens group 5 is partially uneven, the second collimation lens 7 The light that is projected onto the irradiated surface through the irradiation surface is superimposed and irradiated over the same entire surface of the irradiated surface, and the divided secondary light sources are transmitted from multiple directions to the second collimation/lens 7. This illuminates the irradiated surface as a bundle of parallel rays, and prevents the influence of secondary maxima due to diffraction from reducing resolution. At this time, the appropriate angle of the irradiation direction (irradiation angle) is determined by the distance between the mask and the wafer below and the fineness of the pattern formed on the mask.The irradiation angle with the optical axis is determined by the distance between the mask and the wafer below it. 5
When the entire effective radius is t-φ5 and the focal length of the second collimation lens 7 is f7, it is given by:

In the case of the embodiment according to the invention, as shown in FIGS. 4A and 4B, the first collimation lens group 4 includes two
It consists of a pair of concave lenses, and by moving them on the optical axis and changing the distance between the concave lenses belonging to the front group and the concave lenses extending to the rear group relative to each other in relation to the overall movement, they can be moved. The combined focal length of the pair changes. That is, let the focal length of the concave lens belonging to the front group be f4,
If the focal length of the concave lens belonging to the rear group is t2, and the distance between these principal points is do, then the combined focal length of these lenses is f.

is determined by the following formula.

Therefore, even when the distance d0 between principal points is widened from d toward d', the relative movement of each lens is performed so that the rear focal point F4 (exit @) is always on the second focal point of the ellipse fa2. As far as possible, the light rays emitted from the first collimation lens group 4 toward the compound eye lens group 5 as an optical integrator are emitted as parallel light beams. In this case, the focal point I which also coincides with the second focal point of the elliptical mirror 2
Since the angle formed by the condensed beam toward F, that is, the angle of incidence α with respect to the first collimation lens group 4, is a constant value,
The result of the relative movement performed on the first collimation lens group 4 is that the diameter of the parallel beam of the exiting ray varies between φ1 and φ8, and due to the relative movement of the front group lens and the predominant lens, A line in which the width of the luminous flux of light incident on the compound eye lens group 5 changes. As shown in Figure @4B, moving both lenses closer to the second focal point of the elliptical mirror 2 and increasing the distance between the principal points between both lenses increases the light density of the total amount of light at the incident angle α, which is the source of the intensity. is given to the compound eye lens group 5. As a result, a large number of secondary light sources generated by being divided by the compound lens group 5 are generated near the optical axis, and the parallel f flux emitted by the second collimation lens 7IIc is directed toward a portion close to the optical axis. They will be intensively superimposed. Therefore, it is possible to uniformly and intensively illuminate a small-area irradiated object with the entire amount of light without loss of light amount. On the other hand, in order to provide even and uniform illumination over a large area, the first
While keeping the position of the focal point F4 of the collimation lens group 4 at the position of the second focal point of the elliptical mirror 2°, both lenses are connected to the light source 1.
111Vc, and as the distance between the mutual lens principal points decreases in connection with this movement, the diameter of the parallel light beam emerging from the first collimation lens group 4 increases, and the diameter of the parallel light flux as an optical inch grater increases. As the two-dimensional light source divided and formed by the compound lens group 5 increases, the diameter of the parallel light beam by the second collimation lens 7 increases, and uniform illumination over a wide area is achieved. In FIGS. 4A and 4B, fL and '= should be interpreted as fM as a larger value and a smaller value of the combined focal length of both lenses.

The example shown in FIGS. 4A and 4B shows an example in which the first collimation lens group 4 is configured with a red-divergent lens chamber, thereby always keeping the rear focus at the @22 focus of the elliptical mirror 2. However, when using a convergent collimation lens, the front focus of the collimation lens group should be made to match the second focus of the elliptical mirror 2. While maintaining this, the lens group will be moved. Figures 5A and 5
Figure B shows an example of the situation, but as is clear from the figure, in the examples of Figures 4A and 4B, the reflected condensed beam is directed to the first collimation lens group 4. However, in the examples shown in FIGS. 5A and 5B, the original diverging light that was once focused on the second focal point F' of the elliptical mirror 2 is
The light beam exiting the collimation lens group 4' is guided to the compound eye lens group 5 as a parallel light beam. In this case, the change in φ and the lens group 6
The movement of the convex L 8 lens is considered to be self-evident from the explanations shown in FIGS. 4A and 4B, so its details will be omitted.

In any of the above examples, according to the present invention, the compound lens group 5 as an optical inch grater is provided with a parallel light beam whose diameter can be continuously changed.
In the case of a beam of light with a large diameter, the light enters many convex lens elements of the compound lens group 5, expanding the diameter of the effective beam of light, and uniformly illuminating a wide area to the target. In order to obtain a small beam of light, it is possible to make strong light incident on a small number of peripheral elements near the original axis of the compound lens group 5 to provide uniform and strong illumination to a narrow area. In particular, since it does not rely on a light amount limiting mechanism such as an iris diaphragm, there is no loss of light amount in illumination, which is an excellent feature and has many practical benefits. In addition, as described above, the irradiation angle for removing the influence of the original diffraction is the radius of the compound lens group 50, which is the radius of the second collimation lens 7.
Since it is related to the value of the focal length, set the appropriate irradiation angle to W.
Il collimation lens group 4 and n 4 'O combined illumination can be selectively obtained, which is extremely effective.

[Brief explanation of the drawing]

Figure 1 is a side view showing the outline of the illumination optical system of the present invention, Figure 2 is a side view showing an outline of the illumination optical system of the present invention;
Figure A is a front view of a fly's eye lens used in the illumination optical system of the present invention, and Figure 2B is a side view showing a fly's eye lens group used in combination in the illumination optical system of the present invention.
Figure 3 is a side view showing the relationship between the optical path passing through each flare eye lens and the lens spacing. *Figure 4A and Figure 4B are the first collimation dampers with divergence, which are composed of two groups in the front and rear. FIG. 5A and FIG. 5B are explanatory diagrams showing a mode in which the diameter of the light beam is changed by changing the positional movement and mutual spacing of the lenses, and FIGS. 5A and 5B are
FIG. 6 is an explanatory diagram showing a mode in which the diameter of a parallel light beam is changed by changing the position hsm and mutual spacing of convergent FGL collimation lenses each consisting of two groups, front and rear. l...Light source, 2...Ellipse-13...Cold mirror 4.4'...101J/-John lens group 5.
... Fly eye lens group, 7... Second Collier 1-John lens, 8. Fist mask, 9... Wafer fx + f2... Focal length of fly eye lens D... Lens spacing, fI ,,fs
...Synthetic focal length, f, # fν...; Condition of the first collimation lens group (1,, d'... Lens interval, φ1.φ8... Longitude of the ray bundle, y' - ellipse Mirror focus patent applicant Mikasa Co., Ltd.

Claims (1)

[Scope of Claims] (1) An elliptical mirror, a light source located at its first focus, and a movable first light source consisting of at least two groups arranged so that the focus coincides with the second focus of the elliptical mirror. 1) A first collimation lens, an optical inch grater that occupies the light beam from the light source that is emitted as parallel light parallel to the optical axis by the first collimation lens, and a large number of optical inch graters formed by the optical inch grater. The optical inch grater is composed of a plurality of convex lens elements t [combined primary eye lens Front and back 2 without compound eyes like
A bright optical system in which the diameter of the parallel ray bundle emitted from the lenses is changed by moving each lens in a group in a mutually reciprocal manner. (2) The movable first collimation lens consisting of the two groups described in the preceding paragraph has a diverging property, and its rear focal point coincides with the sg2 focal point of the elliptical mirror.
An illumination optical system in the IC pattern transfer device according to I. (31) The IC according to claim (1), wherein the movable first collimation lens consisting of the two groups described in the preceding paragraph has a convergent property, and its front focus coincides with the second focus of the elliptical mirror. Illumination optical system in a pattern transfer device. (4) An optical inching grater placed in a parallel beam of light emitted from a first collimation lens illuminates a plurality of compound lenses such as a ply eye lens in which a number of convex lens elements are combined. An illumination optical system in an IC pattern transfer device according to the configuration. The lens has two groups, the front group and the rear group, which are separated by a distance between the principal points, and power is distributed, and the convex surfaces of the multiple convex lens elements with a small radius of curvature are positioned facing the incident ft411K −, and each of the front groups An optical system consisting of a convex lens element and each convex lens element of the rear group is placed on a common optical axis, and when the focal length m of each convex lens element is fl and f2, f1=f2 or f2 in f□ And, 2
・Claim No. 0 that satisfies the following relationship: 1.8
) or #'i No. 121 JA or the illumination optical system in the Xa pattern transfer device described in item (3).