Projection exposure method, projection exposure apparatus, laser radiation source and bandwidth narrowing module for a laser radiation source
In a projection exposure method for the exposure of a radiation-sensitive substrate arranged in the region of an image surface of a projection objective with at least one image of a pattern of a mask arranged in the region of an object surface of the projection objective, laser radiation having a spectral intensity distribution I(ω) dependent on the angular frequency ω is used. The laser radiation is characterized by an aberration parameter α in accordance with: α := ∫ I ( ω ) ω 2 ⅆ ω ∫ I ( ω ) ⅆ ω and a coherence time τ in accordance with: τ = ∫ I ( ω ) 2 ⅆ ω [ ∫ I ( ω ) ⅆ ω ] 2 The laser radiation is introduced into an illumination system for generating an illumination radiation directed onto the mask, and the pattern is imaged onto the substrate with the aid of a projection objective. The spectral intensity distribution is set so that ατ 2 ≦0.3. The influence of temporally varying speckles on image generation can be reduced by comparison with conventional methods, without simultaneously increasing the influence of chromatic aberrations on image generation.
1. A projection exposure method for the exposure of a radiation-sensitive substrate arranged in the region of an image surface of a projection objective with at least one image of a pattern of a mask arranged in the region of an object surface of the projection objective, comprising:
generating laser radiation having a spectral intensity distribution I(ω) dependent on an angular frequency ω, wherein the laser radiation is characterized by an aberration parameter α in accordance with:
a
:=
∫
I
(
ω
)
ω
2
ⅆ
ω
∫
I
(
ω
)
ⅆ
ω
and a coherence time τ in accordance with:
τ
=
∫
I
(
ω
)
2
ⅆ
ω
[
∫
I
(
ω
)
ⅆ
ω
]
2
introducing the laser radiation into an illumination system for generating an illumination radiation directed onto the mask;
imaging the pattern onto the substrate using a projection objective;
wherein the spectral intensity distribution is set so that ατ 2 ≦0.3.
2. The projection exposure method of claim 1 , wherein the spectral intensity distribution is set so that ατ 2 ≦0.1.
3. The projection exposure method of claim 1 , wherein the spectral intensity distribution I(ω) corresponds to a Gaussian curve of the full width at half maximum σ, wherein α=σ 2 /2 and τ=1/(√2πσ).
4. The projection exposure method of claim 1 wherein the spectral intensity distribution I(ω) has a parabolic shape.
5. The projection exposure method of claim 1 , wherein a maximum of the spectral intensity distribution lies in the ultraviolet range at a wavelength of less than 260 nm.
6. A projection exposure apparatus for the exposure of a radiation-sensitive substrate arranged in the region of an image surface of a projection objective with at least one image of a pattern of a mask arranged in the region of an object surface of the projection objective, comprising:
a primary laser radiation source for emitting laser radiation;
an illumination system for receiving the laser radiation and for generating an illumination radiation directed onto the mask;
a projection objective for generating an image of the pattern in the region of the image surface of the projection objective;
wherein the laser radiation source is designed for generating laser radiation having a spectral intensity distribution I(ω) dependent on an angular frequency ω, wherein the laser radiation is characterized by an aberration parameter α in accordance with:
a
:=
∫
I
(
ω
)
ω
2
ⅆ
ω
∫
I
(
ω
)
ⅆ
ω
and a coherence time τ in accordance with:
τ
=
∫
I
(
ω
)
2
ⅆ
ω
[
∫
I
(
ω
)
ⅆ
ω
]
2
,
wherein the spectral intensity distribution is set so that ατ 2 ≦0.3.
7. The projection exposure apparatus of claim 6 , wherein the spectral intensity distribution is set so that ατ 2 ≦0.1.
8. The projection exposure apparatus of claim 6 , wherein the spectral intensity distribution I(ω) corresponds to a Gaussian curve of the full width at half maximum σ, wherein α=σ 2 /2 and τ=1/(√2πσ).
9. The projection exposure apparatus of claim 6 , wherein the spectral intensity distribution I(ω) has a parabolic shape.
10. The projection exposure apparatus of claim 6 , wherein a maximum of the spectral intensity distribution lies in the deep ultraviolet range at a wavelength of less than 260 nm.
11. A laser radiation source for generating laser radiation having a spectral intensity distribution I(ω) dependent on an angular frequency ω for use in a projection exposure apparatus as claimed in claim 6 , wherein the laser radiation is characterized by an aberration parameter α in accordance with:
a
:=
∫
I
(
ω
)
ω
2
ⅆ
ω
∫
I
(
ω
)
ⅆ
ω
and a coherence time τ in accordance with:
τ
=
∫
I
(
ω
)
2
ⅆ
ω
[
∫
I
(
ω
)
ⅆ
ω
]
2
.
wherein the spectral intensity distribution is set so that ατ 2 ≦0.3.
12. The laser radiation source of claim 11 , wherein the spectral intensity distribution is set so that ατ 2 ≦0.1.
13. The laser radiation source of claim 11 , wherein the spectral intensity distribution I(ω) corresponds to a Gaussian curve of the full width at half maximum σ, wherein α=σ 2 /2 and τ=1/(√2πσ).
14. The laser radiation source of claim 11 , wherein the spectral intensity distribution I(ω) has a parabolic shape.
15. The laser radiation source of claim 11 , wherein a maximum of the spectral intensity distribution lies in the deep ultraviolet range at a wavelength of less than 260 nm.
16. The laser radiation source of claim 11 , further comprising a bandwidth narrowing module comprising a reflection grating for the wavelength-selective reflection of laser radiation of a resonator of the laser radiation source, wherein a spectral intensity distribution of the laser radiation is substantially determined by a spectral reflectivity of the reflection grating, and a height profile of the reflection grating is defined so that ατ 2 ≦0.3.
17. A bandwidth narrowing module for the laser radiation source of claim 11 , comprising a reflection grating for the wavelength-selective reflection of laser radiation of a resonator of the laser radiation source, wherein a spectral intensity distribution of the laser radiation is substantially determined by a spectral reflectivity of the reflection grating, and a height profile of the reflection grating is defined so that a spectral intensity distribution I(ω) dependent on the angular frequency ω results for the laser radiation, wherein the laser radiation is characterized by an aberration parameter α in accordance with:
a
:=
∫
I
(
ω
)
ω
2
ⅆ
ω
∫
I
(
ω
)
ⅆ
ω
and a coherence time τ in accordance with:
τ
=
∫
I
(
ω
)
2
ⅆ
ω
[
∫
I
(
ω
)
ⅆ
ω
]
2
.
wherein ατ 2 ≦0.3.
18. The bandwidth narrowing module of claim 17 , wherein the height profile of the reflection grating is designed so that the spectral intensity distribution I(ω) substantially corresponds to a Gaussian curve of the full width at half maximum σ, wherein α=σ 2 /2 and τ=1/(√2πσ).
19. The bandwidth narrowing module of claim 17 , wherein the height profile of the reflection grating is designed so that the spectral intensity distribution I(ω) substantially has a parabolic shape.