JP6371925B1 - Light source device and exposure apparatus including the same - Google Patents

Abstract

Provided is a light source device capable of collecting light emitted from a light source in a predetermined irradiation range and improving light utilization efficiency.
A light source device includes a light source, a collimating element that makes light from the light source 12 closer to parallel light toward the irradiation surface, and the collimating element and the irradiation surface. A condensing element 16 that is disposed between them and collects light from the collimating element 14 on the irradiation surface S.
[Selection] Figure 1

Description

  The present invention relates to a light source device used in, for example, an exposure apparatus for manufacturing a semiconductor.

  In general, since light is emitted radially from a light source such as a lamp, the light traveling toward the irradiation surface becomes a part of the total light emission amount, and the light use efficiency is very poor. For this reason, the device which improves the utilization efficiency of light by controlling the direction of these light and increasing the ratio of the light which goes to irradiation object conventionally has been made | formed.

  For example, as shown in FIG. 7, it is common practice to use a reflector 1 having a reflecting surface 2 on the inner surface. The reflecting surface 2 of the reflector 1 is defined by a rotating paraboloid, and the light source 4 is arranged at the position of the focal point 3 of the rotating paraboloid, so that most of the light emitted from the light source 4 is directed to the irradiation surface 5 It is possible to make light close to (a quasi-parallel light).

JP-A-8-29873

  However, since the actual light source is not a theoretical point light emitter but a surface light emitter having a predetermined light emitting area, when the reflector 1 as described above is used, most of the light is slightly shifted from the focal point 3. The light is emitted from the selected position. For this reason, the light radiated from the opening of the reflector 1 after being reflected by the reflecting surface 2 is not completely parallel light but becomes light that spreads outward as the distance from the reflector 1 increases.

  For this reason, when the irradiation surface 5 is relatively far from the reflector (for example, 500 [mm] or more) and the area of the irradiation surface 5 is small, there is a problem that the light use efficiency cannot be increased. there were.

  For example, Patent Document 1 discloses a technique in which a reflecting mirror having an opening at the center is arranged at the opening of the reflector in order to improve the degree of parallelism of light emitted from the reflector.

  However, the technique disclosed in Patent Document 1 only describes light from the focal position of the rotating paraboloid that defines the reflecting surface formed inside the reflector, and has an actual light emitting area. The light radiated from the surface light emitter does not become completely parallel light, but spreads outward as the distance from the reflector increases. For this reason, when the irradiation surface is relatively far from the reflector and the area of the irradiation surface is small, the problem that the light use efficiency cannot be improved has not been solved.

  The present invention has been made in view of such problems, and an object thereof is to provide a light source device that can collect light emitted from a light source in a predetermined irradiation range and improve light utilization efficiency. And an exposure apparatus including the same.

According to one aspect of the present invention,
A light source;
A collimating element that makes light from the light source closer to parallel light toward the irradiation surface;
A light source device including a condensing element disposed between the collimating element and the irradiation surface and collecting light from the collimating element on the irradiation surface ;
The collimating element is a reflector having a reflecting surface defined by a paraboloid of revolution inside,
The condensing element is a lens having a focal point,
Each of the light source devices is composed of a plurality of the light sources, the parallelizing elements, and the light collecting elements,
A light source device characterized by satisfying the following two expressions is provided.
L1 ≧ a × L / (d + a)
L: Distance from the opening of the reflector to the irradiated surface [mm]
L1: Distance [mm] from the aperture of the reflector to the optical center of the light collecting element
a: Diameter of opening of the reflector [mm]
d: Diameter of the irradiated surface [mm]
L1 ≦ (L2 × tan α−a) / (2 × tan θ)
L2: Distance [mm] from the optical center of the condensing element to the irradiation surface
θ: outgoing divergence angle [°] of light emitted from the collimating element
α: Angle formed by the central axes of light emitted from the parallelizing elements adjacent to each other [°]

According to another aspect of the invention,
A light source;
A collimating element that makes light from the light source closer to parallel light toward the irradiation surface;
A light source device including a condensing element disposed between the collimating element and the irradiation surface and collecting light from the collimating element on the irradiation surface;
The light source is a planar light emitter;
The collimating element is a lens;
The condensing element is a lens having a focal point,
Each of the light source devices is composed of a plurality of the light sources, the parallelizing elements, and the light collecting elements,
A light source device characterized by satisfying the following two expressions is provided.
L1 ≧ a × L / (d + a)
L: Distance from the optical center of the collimating element to the irradiation surface [mm]
L1: Distance [mm] from the optical center of the collimating element to the optical center of the condensing element
a: Effective diameter [mm] of the parallelizing element
d: Diameter of the irradiated surface [mm]
L1 ≦ (L2 × tan α−a) / (2 × tan θ)
L2: Distance [mm] from the optical center of the condensing element to the irradiation surface
θ: outgoing divergence angle [°] of light emitted from the collimating element
α: Angle formed by the central axes of light emitted from the parallelizing elements adjacent to each other [°]

Preferably,
L1 (A) = a × L / (d + a)
When L1 (B) = (L2 × tan α−a) / (2 × tan θ),
The dimension value of L1 is as follows.
-When L1 (A) ≦ L1 (B), the value of L1 (B).
When L1 (A)> L1 (B), a value between L1 (A) and L1 (B).

According to another aspect of the invention,
An exposure apparatus including the light source device described above is provided.

  ADVANTAGE OF THE INVENTION According to this invention, the light source device which can collect the light radiated | emitted from the light source in the predetermined irradiation range and can improve the utilization efficiency of light, and the exposure apparatus provided with the same could be provided.

It is a figure which shows an example of the light source device 10 with which this invention was applied. It is a figure for demonstrating mainly the parallelizing element. It is a figure for demonstrating the dimension of each element and the irradiation surface S, etc. FIG. It is a figure which shows an example of the light source device 10 which concerns on the modification 1. It is a figure which shows an example of the light source device 10 which concerns on the modification 2. It is a figure which shows an example of the light source device 10 and the exposure apparatus 100 which concern on the modification 3. It is a figure which shows the conventional light source device.

(Configuration of light source device 10)
FIG. 1 shows a light source device 10 according to an embodiment to which the present invention is applied. The light source device 10 is generally a device that includes a light source 12, a collimating element 14, and a condensing element 16, and irradiates light toward an irradiation surface S having a predetermined diameter (diameter).

  The light source 12 is an element that receives power supplied from the outside and emits light including a wavelength suitable for the use of the light source device 10. For example, a flat light emitter such as a light emitting diode and an organic EL, a discharge lamp, or the like Although considered, it is not limited to these. As will be described later, when a reflector is used as the collimating element 14, a light source 12 having a low directivity of light, such as a discharge lamp, can be used.

  The collimating element 14 is an element that brings light from the light source 12 closer to parallel light toward the irradiation surface S, and a reflector is used in this embodiment. Hereinafter, the same reference numeral “14” is used for the reflector. In the present embodiment, as described above, a reflector is used for the collimating element 14. However, an element other than the reflector may be used as long as the element plays the above-described role. As an example of the collimating element 14 other than the reflector, a case where a lens is used will be described in “Modification 2” described later.

  As shown in FIG. 2, the reflector 14 is formed in a substantially bowl shape, and has an opening 20 and a reflection surface 22 formed on the inner surface thereof. The reflecting surface 22 is defined by a paraboloid of revolution, and the axis of rotation of the paraboloid of revolution and the center axis CL of the reflector 14 coincide with each other.

  Further, the rotary paraboloid has a focal point PF, and in this embodiment, the positional relationship between the light source 12 and the reflector 14 is defined so that the position of the center of the light source 12 coincides with the position of the focal point PF. ing. Thus, the light emitted from the position of the focal point PF, reflected by the reflecting surface 22 defined by the rotating paraboloid and exiting from the opening 20 becomes parallel light parallel to the central axis CL of the reflector 14.

  However, the light source 12 is not a theoretical point light emitter, and even when a discharge lamp is used as the light source 12, light is emitted from a light emitting surface having a predetermined area. Most of the emitted light is emitted from a position deviated from the focal point PF. For this reason, the light emitted from the light source 12, reflected by the reflecting surface 22, and emitted from the opening 20 is not completely parallel light, but becomes light that spreads outward as the distance from the reflector 14 increases.

  Returning to FIG. 1, the condensing element 16 is disposed between the reflector (parallelizing element) 14 and the irradiation surface S, and collects light from the reflector (parallelizing element) 14 on the irradiation surface S. It is an element having. In the present embodiment, a lens is used as the condensing element 16, but an element other than the lens may be used as long as it is an element that plays the above-described role.

(Operation of the light source device 10)
The operation of the light source device 10 will be described with reference to FIG. A part of the light emitted from the light source 12 goes directly out of the opening 20 of the reflector 14, and the remaining light is reflected by the reflecting surface 22 inside the reflector 14 and then goes out of the opening 20. The light reflected by the reflecting surface 22 travels at an angle close to parallel light with respect to the central axis CL of the reflector 14, but spreads outward as it moves away from the reflector 14 instead of being completely parallel light.

  The light emitted from the reflector 14 is refracted toward the irradiation surface S when passing through the light collecting element 16. Thereby, the light emitted from the condensing element 16 is collected toward the irradiation surface S and irradiates the irradiation surface S.

(Positional relationship and dimensions of each element etc.)
Next, the positional relationship between each element and the irradiation surface S and the dimensions of each element and the irradiation surface S will be described with reference to FIG. An irradiation surface S is disposed at a distance L [mm] from the opening 20 of the reflector (parallelizing element) 14. When the diameter (diameter) of the irradiation surface S is c [mm], in order to minimize the diameter c, the distance L2 [mm] from the light condensing element 16 (lens) to the irradiation surface S is set to the light condensing element 16. It is sufficient to match the focal length f [mm]. That is, if the light collection efficiency is increased by increasing the degree of light collection on the irradiation surface S, the position of the light condensing element 16 approaches the irradiation surface S (distance L2 is shortened). In other words, the condensing element 16 moves away from the reflector 14 (the distance L1 [mm] from the opening 20 of the reflector 14 to the condensing element 16 increases).

  Here, as described above, the light emitted from the reflector 14 is not completely parallel light but is light that spreads outward as the distance from the reflector 14 increases. The spread (diameter) also increases. For this reason, as the distance L1 increases, some outside light becomes invalid light (light that cannot be collected on the irradiation surface S) deviated from the light collecting element 16.

  That is, when the light condensing element 16 is brought close to the irradiation surface S, the degree of light condensing increases and the light use efficiency tends to increase. The light from the activating element 14 is detached from the light condensing element 16, and the ineffective light is increased to reduce the light use efficiency.

Therefore, first, the distance L1 from the opening 20 of the collimating element 14 to the condensing element 16 will be examined. When the diameter (diameter) of the opening 20 of the reflector 14 is a [mm], and the emission divergence angle (angle formed with the central axis CL) of the light emitted from the collimating element 14 is θ [°], The diameter E [mm] of the light irradiation range at the position can be expressed by the following equation.
E = a + L1 × 2 tan θ

In addition, the utilization factor of the light in the position of the condensing element 16, that is, the ratio S1 of the light exiting from the collimating element 14 and entering the condensing element 16 can be expressed by the following equation. In addition, let the diameter (diameter) of the condensing element 16 be b [mm].
S1 = b ² / E ² = b ² / (a + L1 × ² tan θ) ²

Next, the distance from the condensing element 16 to the irradiation surface S will be examined. If the diameter (diameter) of the irradiated surface S is c [mm], the following relationship can be generally said.
c / a = L2 / L1

Here, as described above, the maximum utilization efficiency is when the range (diameter) d [mm] irradiated with the light from the condensing element 16 matches the required diameter c [mm] of the irradiation surface S. Therefore, the following relationship can be said.
c = d
L2 = L−L1.

Therefore,
d = a × (L−L1) / L1
L1 = a * L / (d + a) and L2 = L * (1-a) / (d + a).

On the other hand, when the focal length of the light collecting element 16 is f [mm], the following relationship can be said.
1 / L1 + 1 / L2 = 1 / f
Accordingly, the focal length f [mm] of the light collecting element 16 can be expressed by the following equation.
f = L1 × L2 / (L1 + L2)
= A x L / (d + a)

From the above, the maximum utilization efficiency is obtained when the following two expressions are satisfied.
L1 = a × L / (d + a) and f = a × L / (d + a)

Further, by satisfying the following conditions, the range (diameter) d [mm] irradiated with the light from the light collecting element 16 is within the range of the diameter c [mm] of the required irradiation surface S, and is outside the irradiation surface S. It is effective in that useless light that illuminates the light is eliminated.
L1> a × L / (d + a)

The light quantity Z on the irradiation surface S can be expressed by the following equation, where W is the light quantity of light emitted from the collimating element 14.
Z = W × b ² / (a + (a × L / (d + a)) × ² tan θ) ²

(Modification 1)
In the embodiment described above, each light source device 10 is configured by one light source 12, a reflector 14, and a condensing element 16, but instead, as shown in FIG. 4, a plurality of light sources 12, reflectors are respectively provided. 14 and the light condensing element 16 may constitute the light source device 10 so that one irradiation surface S is illuminated with light from each light source 12. For the following description, see FIG. 3 for L, L1, and L2.

Also in this case, basically, as described in the above-described embodiment, it is preferable to satisfy the following expression.
L1 ≧ a × L / (d + a)
Note that L1 defined by the relational expression “a × L / (d + a)” will be denoted as “L1 (A)” below. That is, “L1 (A) = a × L / (d + a)”.

  However, when the light source device 10 is composed of a plurality of light sources 12 and the like, there is a dimensional restriction due to a practical request to make the light source device 10 as compact as possible. Specifically, the size of the effective diameter (diameter) of the light condensing element (lens) 16 is limited. This is because if the effective diameter (diameter) of the condensing element (lens) 16 is too large, it interferes with the condensing element (lens) 16 disposed next to it.

In the first modification shown in FIG. 4, the maximum effective diameter (diameter) B [mm] of the light condensing element (lens) 16 can be expressed by the following equation. Α is an angle [°] formed by the central axes CL of light emitted from the paralleling elements (reflectors) 14 adjacent to each other.
B = L2 × tanα

Further, the range (diameter) g [mm] in which the condensing element (lens) 16 is irradiated with the light emitted from the light source 12 and then emitted from the reflector 14 can be expressed by the following expression.
g = a + 2 × L1 × tan θ
a: Diameter of the opening of the collimating element (reflector) [mm]
θ: the outgoing divergence angle of light emitted from the collimating element (reflector) 14 (angle formed with the central axis CL)

If the range (diameter) g irradiated with the condensing element (lens) 16 by the light emitted from the reflector 14 becomes larger than the maximum effective diameter (diameter) B of the condensing element (lens) 16, the reflector 14 A part of the emitted light is detached from the condensing element (lens) 16 and becomes useless light. Therefore, it is preferable that the following relationship is satisfied.
B ≧ g, that is,
L2 × tan α ≧ a + 2 × L1 × tan θ,
L1 ≦ (L2 × tan α−a) / (2 × tan θ).
Note that L1 defined by the relational expression “(L2 × tan α−a) / (2 × tan θ)” will be denoted as “L1 (B)” below. That is, “L1 (B) = (L2 × tan α−a) / (2 × tan θ)”.

From the above, the dimension of L1 can be simply expressed as “L1 (A) is preferably larger” and conversely “L1 (B) is preferably smaller”. Therefore, after calculating L1 (A) and L1 (B), it is preferable to determine the dimension of L1 as follows.
・ When L1 (A) ≦ L1 (B), L1 (B) is adopted as the dimension of L1.
When L1 (A)> L1 (B), a value between L1 (A) and L1 (B) is adopted as the dimension of L1. That is, the relationship is L1 (A)>L1> L1 (B).

(Modification 2)
In the above-described embodiment, a reflector is used as the collimating element 14, but instead, a lens may be used as the collimating element 14 as shown in FIG. Although FIG. 5 illustrates the case where one (single) lens is used, the number of lenses as the parallelizing element 14 may be plural. In this case, the light emitted from the light source 12 is refracted when passing through the collimating element (lens) 14 and becomes closer to parallel light toward the irradiation surface S. Then, the light emitted from the collimating element (lens) 14 is collected on the irradiation surface S by the condensing element 16.

  In the case of the second modification (that is, when a lens is used as the collimating element 14), the mathematical formulas and operational effects described in the above-described embodiments are established. Therefore, for the explanation of the numerical formulas and operational effects according to the modified example 2, “reflector 14” is “lens 14” and “opening 20 of reflector 14” is “lens 14” or “lens” 14 ”, and“ the diameter (diameter) a [mm] of the opening 20 of the reflector 14 ”are replaced with“ the effective diameter (diameter) a [mm] of the lens 14 ”.

  In addition, when using a lens as the collimating element 14, it is preferable to use LED and organic EL with high directivity of the light to radiate | emit as the light source 12 compared with the case where a reflector is used.

(Modification 3)
Next, an example in which the light source device 10 is configured by using a plurality of light sources 12, collimating elements 14, and condensing elements 16 and the light source device 10 is applied to the exposure apparatus 100 will be described with reference to FIG. explain.

  The exposure apparatus 100 according to Modification 3 includes a light source device 10, a first reflecting mirror 102, a second reflecting mirror 104, a third reflecting mirror 106, an integrator 108, and a collimating lens 110.

  As described above, the light source device 10 used in the third modification includes two light sources 12, two collimating elements (reflectors) 14, and two condensing elements 16. The light emitted from the light source device 10 is reflected by the first reflecting mirror 102 and the second reflecting mirror 104 in a predetermined direction, and then illuminates the incident surface 112 of the integrator 108. That is, for the light source device 10, the incident surface 112 of the integrator 108 is the irradiation surface S in this case.

  The light emitted from the exit surface 114 of the integrator 108 is reflected by the third reflecting mirror 106 in a predetermined direction, and then becomes parallel light through the collimating lens 110 to illuminate the exposure surface 116.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

DESCRIPTION OF SYMBOLS 10 ... Light source device, 12 ... Light source, 14 ... Parallelizing element (reflector or lens), 16 ... Condensing element 20 ... Aperture, 22 ... Reflecting surface S ... Irradiation surface, CL ... Central axis, PF ... (Rotating paraboloid) L): distance from the collimating element 14 to the irradiation surface S, L1: distance from the collimating element 14 to the condensing element 16, L2: distance from the condensing element 16 to the irradiation surface S, a: opening 20 (diameter) or effective diameter (diameter) of the lens 14, b ... diameter (diameter) of the condensing element 16, c ... diameter (diameter) of the irradiation surface S, d ... irradiation with light from the condensing element 16 Range (diameter), f: focal length of the condensing element 16, g: range (diameter) in which the condensing element (lens) 16 is irradiated by light emitted from the collimating element 14, θ: collimating element 14 The outgoing divergence angle (angle formed with the central axis CL) of the light emitted from the light beam, α ... parallelization adjacent to each other Angle formed by the central axes CL of the light emitted from the child 14 100... Exposure apparatus, 102... First reflecting mirror, 104... Second reflecting mirror, 106 ... third reflecting mirror, 108 ... integrator, 110. ... incident surface (of integrator 108) 114 ... exiting surface (of integrator 108) 116 ... exposure surface

Claims (4)

A light source;
A collimating element that makes light from the light source closer to parallel light toward the irradiation surface;
A light source device including a condensing element disposed between the collimating element and the irradiation surface and collecting light from the collimating element on the irradiation surface ;
The collimating element is a reflector having a reflecting surface defined by a paraboloid of revolution inside,
The condensing element is a lens having a focal point,
Each of the light source devices is composed of a plurality of the light sources, the parallelizing elements, and the light collecting elements,
A light source device satisfying the following two expressions:
L1 ≧ a × L / (d + a)
L: Distance from the opening of the reflector to the irradiated surface [mm]
L1: Distance [mm] from the aperture of the reflector to the optical center of the light collecting element
a: Diameter of opening of the reflector [mm]
d: Diameter of the irradiated surface [mm]
L1 ≦ (L2 × tan α−a) / (2 × tan θ)
L2: Distance [mm] from the optical center of the condensing element to the irradiation surface
θ: outgoing divergence angle [°] of light emitted from the collimating element
α: Angle formed by the central axes of light emitted from the parallelizing elements adjacent to each other [°] A light source;
A collimating element that makes light from the light source closer to parallel light toward the irradiation surface;
A light source device including a condensing element disposed between the collimating element and the irradiation surface and collecting light from the collimating element on the irradiation surface ;
The light source is a planar light emitter;
The collimating element is a lens;
The condensing element is a lens having a focal point,
Each of the light source devices is composed of a plurality of the light sources, the parallelizing elements, and the light collecting elements,
A light source device satisfying the following two expressions:
L1 ≧ a × L / (d + a)
L: Distance from the optical center of the collimating element to the irradiation surface [mm]
L1: Distance [mm] from the optical center of the collimating element to the optical center of the condensing element
a: Effective diameter [mm] of the parallelizing element
d: Diameter of the irradiated surface [mm]
L1 ≦ (L2 × tan α−a) / (2 × tan θ)
L2: Distance [mm] from the optical center of the condensing element to the irradiation surface
θ: outgoing divergence angle [°] of light emitted from the collimating element
α: Angle formed by the central axes of light emitted from the parallelizing elements adjacent to each other [°] L1 (A) = a × L / (d + a)
3. The light source device according to claim 1, wherein when L1 (B) = (L2 × tan α−a) / (2 × tan θ), the dimension value of L1 is as follows.
-When L1 (A) ≦ L1 (B), the value of L1 (B).
When L1 (A)> L1 (B), a value between L1 (A) and L1 (B). An exposure device including the light source device according to any one of claims 1 to 3.

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