JP2001108936A - Machine and method for optical processing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a machine and method for optical processing capable of precisely and satisfactorily execute optical processing of a matter to be processed optically. SOLUTION: In an optical processing machine for optically processing a matter to be processed optically by illuminating a pattern on a mask with a luminous flux from a light source means and projecting the pattern on the mask onto the matter to be processed with a projection lens, the mask utilizes phase shift.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical processing machine and an optical processing method, for example, using an intense coherent light such as an ultraviolet laser to directly cause an ablation phenomenon on a workpiece to obtain a desired shape (for example, a plurality of lasers). This method is suitable for manufacturing an orifice plate or the like used in an ink jet printer using an ablation processing method for processing into a pattern in which openings are arranged.

[0002]

2. Description of the Related Art Conventionally, laser processing for making a hole in a workpiece by using a laser beam has been frequently used as a method capable of non-contact and precise processing. Ablation is a method of irradiating a substance with large light absorption with an ultraviolet laser or the like to extremely increase the internal energy per unit volume, exploding and evaporating the area very near the light irradiation part, and removing it. In recent years, its use has been active.

[0003] The features of this ablation processing are as follows: (a-1) Compared with a direct thermal process using a CO ₂ laser or the like, the thermalization rate is small, so the processing accuracy is high, and
There is little deterioration. (A-2) Since the object removed on the workpiece is finely scattered, the quality may be improved depending on the purpose. (A-3) Since only a very small surface can be processed, surface treatment such as roughness, defects, functional surface treatment, and glossiness may be possible. (A-4) Since the energy dependence is relatively clear, it is possible to perform machining design reflecting the performance of the laser and the optical system. and so on.

FIG. 8 is a schematic view of an optical system for processing a discharge hole (orifice plate) of a conventional ink jet printer. In the figure, holes arranged in a line at equal intervals
Fig. 2 shows an optical system of a processing apparatus for performing a batch ablation processing.

[0005] 70 is a laser light source as a light source, 71 is
A prism unit that divides the light source, 72 is a light-shielding mask that regulates the light source width, 73 is a controller that controls the vertical and horizontal divergence angles,
A cylindrical lens 74 is a convex lens for a field lens for illumination, 75 is a photomask on which a processed shape is drawn, 76 is a stop surface of a projection lens (also referred to as an objective lens or a projection lens), and 77 is a projection surface. The lens 78 is a processing target (workpiece).

In FIG. 8, a laser beam emitted from a laser 60 is split into a plurality of parallel beams by a prism 71, a size and a divergence angle are specified by a mask 72 and a cylindrical lens 73, and a light source split by a field lens 74. The image is projected on the mask 75 as Keller illumination, and a mask image having a uniform and predetermined spread is generated. The Fourier transform pattern of the mask 75 is formed on the stop 76. The mask image is formed on a processing target 78 by a projection lens 77, and is subjected to ablation processing to form a row of holes in the workpiece.

[0007]

When quasi-parallel light such as a laser or quasi-monochromatic light is used as light for optical processing, for example,
Even if a light source is divided into a light source group having a finite light source side NA and a Keller illumination system is constructed, a wave optic phenomenon that reflects the original good coherence may become apparent.

This phenomenon cannot be understood by geometrical optics such as pupil and ray tracing. Rather, the phenomenon is similar to the wave optical imaging theory of a re-imaging optical system such as a transmission type optical microscope. There is a need.

Referring to FIG. 8, a phenomenon occurring in the projection lens 76 will be considered. When a hole mask periodically arranged in this system is illuminated with quasi-parallel light, high-order diffracted light depending on the pitch is generated.

The telescope type lens groups 41 and 42 shown in FIG.
This will be described with reference to a schematic diagram of the projection lens PL including the two groups.

Now, assuming that the hole pitch of the mask 43 is p, the wavelength of the laser beam 44 is λ, and the focal length of the front group 41 of the projection lens PL is f, paraxially on the stop 45 which is a Fourier transform plane. , G = Lλ / p.

The diffracted light trains are coherent to each other.
Acts as a next light source, and is collimated by the rear group 42 of the projection lens PL.

Assuming that the angle between the 0th order light and the 1st order light on the processing object 46 is θ, the hole pitch h of the projected image is 2
H = λ / θ = λF / g = (F / f) p exp (-iπu (N-1) T) sin (πuNT) / sin (πuT) The second term of the sum is- 2isin (πuS) exp (-iπuS), so F = (sin (πuS) / uπ) exp (-iπu ((N-1) T + S)) × sin (uTNπ) /
sin (uTπ) Here, if the spatial frequency is changed in units of order m, m = uT F = Ssinc (mπS / T) exp (-imπ (N-1 + S / T)) sin (Nmπ) / sin (m
π) Therefore, the ratio of the electric field strengths of order 0 and m is = Mp. M = F / f is nothing but the imaging magnification of the projection lens PL.

Here, considering the range in which the zero-order light and the first-order light pass through the lens of the rear group 42, FIG.
This schematically illustrates a state in which the 0th-order light and the 1st-order light that have passed through the aperture 45 are parallel projected onto the object surface 46 by the rear group lens 42. Naturally, the rear group lens 42 , 1
It cannot be a single lens.

The range in which the zero-order light and the first-order light pass in the rear lens group 42 is naturally different, and as shown in FIG. Occurs.

Further, a portion (B portion) where the 0-order light and the first-order light pass through a portion where the light overlaps a lot and forms an image (a portion B), and a portion where the overlapped portion forms an image without using much (A portion). Occurs.

At this time, the problem is that the zero-order light is much stronger and the high-order diffracted light, which controls a high shape component, is weak.

When this diffraction intensity is calculated, assuming that the hole pitch of the mask 43 is T, the hole width (opening) is S, and the number of holes is N, the Fourier transform F of the mask 43 is represented by X in the hole arrangement direction position, u
Where F = Σ (n = 0 to N-1) ∫ (nT to nT + S) exp (-2πiux) dx = (1 / -i2πu) Σ exp (-i2πunT) (exp (-i2πuS) -1 Here, the first term of the sum is represented by R = sinc (mπS / T).

Since the aperture ratio S / T usually exceeds 1/2, the energy intensity (square of the electric field) often differs by a factor of two or more.

The above description has been discussed as a critical illumination using a parallel light beam as a light source, so it may seem that there is no generality in the case of a Keller illumination system. In many cases, the light source is divided into a finite number of infinity lights to form the illumination, so that the generality is not lost due to the problem of the degree of difference.

By the way, when glass for lasers, such as quartz, is exposed to strong energy, annealing proceeds, causing a change in refractive index and a change in shape. As a result, the lens system causes wavefront aberration, and the amount of change in the wavefront is said to be proportional to the square of the laser energy [Reference: PAUL
SCHERMERHORN, SPIE-The International Society for
Optical Engineering Vol. 1835 (1992)].

Since the deterioration of the glass is energy-dependent, the phase difference of the light of each order causes a difference depending on the used portion of the lens, and therefore, a phase difference of the order on the image plane.

As a result of this wave optical damage, only λ /
Despite the occurrence of the aberration of about 20 or less, the shape of the hole or groove is damaged so that it cannot be formed.

Heretofore, the inventor of the present invention has provided a highly durable CaF ₂ ,
Utilization of sufficiently annealed quartz or the like has been used to increase the durability and life of the lens, but has the following problems. (A-1) Ablation is essentially a destructive process, and no matter how small the fracture threshold of metals and plastics is compared to glass, it uses energy close to the fracture level of kana glass and ultimately damages the glass. Cannot be avoided. (A-2) Highly durable glass is expensive, poor in workability, and supplied in a small amount, so that it is difficult to perform inexpensive and stable production.

According to the present invention, even a glass having low durability can be used as a lens for laser ablation processing.
An object of the present invention is to provide an optical processing machine and an optical processing method capable of stably performing optical processing on a workpiece by controlling the position and the amount of diffracted light by a photomask.

[0026]

According to a first aspect of the present invention, there is provided an optical processing machine which illuminates a pattern on a mask with a light beam from a light source and projects the pattern on the mask onto a workpiece by a projection lens. In an optical processing machine that optically processes the workpiece, the mask uses a phase shift.

According to a second aspect of the present invention, in the first aspect of the present invention, the coherent light from the light source means is irradiated on the workpiece, and the workpiece is optically processed by ablation.

According to a third aspect of the present invention, in the first or second aspect of the present invention, the mask has an opening pattern in which a plurality of openings are arranged at a constant period, and the opening patterns are provided for every other light passing therethrough. And a phase difference of λ / 2 is provided.

According to a fourth aspect of the present invention, there is provided an optical processing method for projecting a pattern of a photomask onto a workpiece by using coherent light and performing ablation processing into a predetermined shape. It is characterized by using.

According to a fifth aspect of the present invention, in the fourth aspect of the present invention, the shape to be processed into the workpiece is a hole or a groove arranged at substantially equal intervals, and the plurality of opening patterns on the mask are It is characterized in that every other light has a phase difference of a half wavelength.

According to a sixth aspect of the present invention, in the invention of the fourth or fifth aspect, a thin film having a phase difference of a half wavelength is formed on the entire surface of the mask, and then ablation processing is performed on the opening pattern of the mask. The method is characterized in that a mask having a desired phase difference distribution manufactured by removing the thin film is used.

[0032]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic view of a main part of a first embodiment of an optical working machine according to the present invention. In the present embodiment, the pattern of the photomask 8 is projected on a workpiece using laser light,
When a parallel groove is ablated (perforated) on the surface, a mask provided with a phase shift film is used as the photomask 8.

In FIG. 1, reference numeral 1 denotes a KrF excimer laser as a light source means, which emits a coherent laser beam 1a with a strong pulse. Reference numeral 2 denotes a mirror for adjusting an optical path, and a laser beam 1 from the excimer laser 1.
a is reflected and deflected. Reference numeral 3 denotes a diffraction grating for adjusting the light amount profile, which makes the profile of the laser beam 1a from the mirror 2 uniform. Reference numeral 4 denotes a front lens for a beam expander, which emits laser light from a diffraction grating 3 and divergent laser light from an aperture 5 to enter a rear lens 6 for a beam expander.
The rear lens 6 emits a laser beam having an increased light beam diameter. Numeral 7 is a prism for upside-down superposition. 8 is a mask (photomask) using a phase shift
A plurality of drilling patterns for the workpiece 12 are formed, and odd-numbered patterns among the drilling patterns are shifted by λ / 2 (λ = 248.3 nm with a KrF laser). A membrane has been applied. The mask 8 has a structure in which a plurality of pinholes are arranged on an opaque substrate at equal intervals in a one-dimensional direction. A plurality of openings of the mask pattern on the photomask 8 have a phase difference of 1/2 wavelength every other. Reference numeral 9 denotes a front lens group of the projection lens PL, and reference numeral 10 denotes a stop for cutting high-order diffracted light. The aperture width of the stop 10 is variable both vertically and horizontally. The stop 10 may be composed of a plurality of stops having different aperture diameters, and one of the stops may be mounted in the optical path. Reference numeral 11 denotes a rear lens group of the projection lens PL. Reference numeral 12 denotes a workpiece, on which a projection lens PL
With this, the pattern of the mask 8 is projected and imaged.

Next, the optical function will be described.

Laser light 1 emitted from excimer laser 1
In a, the optical path is adjusted by the mirror 2 so as to coincide with the optical axis.

In general, since a laser beam has a non-uniform profile, the laser beam is transmitted through a diffraction grating 3 manufactured in a pattern for eliminating the profile, and unnecessary components are removed by an aperture 5 provided at a focal position 5 of a lens 4. This gives a uniform profile. The rear lens 6 for the beam expander is collimated so that the cross section becomes a light beam of a predetermined size.

Thereafter, the laser beam 1a was cut out vertically by the prism 7 and superimposed, passed through the prism 7 as more uniform parallel light, and provided with a phase shift film as a light beam with reduced vertical and undulating swell components. The mask 8 is illuminated by parallel light.

According to the optical principle of the phase shift mask, 0
The light cut out into the diffracted light group having no next light is Fourier-transformed by the front lens group 9 of the projection lens PL, and forms a far-field pattern on the stop 10 to remove higher-order unnecessary components. .

The light beam collimated by the rear lens group 11 forms a reduced image of the mask pattern 8 on the workpiece 12, thereby performing ablation processing.

The effects of the present embodiment are as follows. (C-1) Since the laser light for illumination illuminates the mask by making the laser light uniform and parallel light, a phase difference according to the phase difference built on the mask can be given to the laser light, which is complicated. No mask configuration is required. (C-2) Since the aperture diameter of the stop 10 can be changed, diffracted light of a desired order can be positioned in the aperture depending on the period of the mask.

Next, a case where a plurality of holes are formed at equal intervals in a row and a photomask having no phase shift effect is used,
An optical difference when light transmitted through even-numbered holes and odd-numbered holes in a hole array of a photomask is given a phase difference of λ / 2 will be described.

When the diffraction intensity is calculated, assuming that the hole pitch of the mask is T, the hole width (opening) is S, and the number of holes is N, the Fourier transform F ′ of the mask is as follows.
As spatial frequency If m = uT and the space is changed in order m, the even term,
The parts representing the phase changes of the odd terms are exp (-2πi (2nm)) and exp (-2πi ((2n + 1) m) -1/2), respectively.

These are clearly where m is an integer (including 0)
, Half-integer (± 1/2, ± 3/2 ...
・) In the case of, we strengthen each other.

Therefore, unlike the conventional imaging of three-beam interference by intense 0th-order light and weak ± 1st-order light, FIG.
As shown in the figure, 2 passes through the target optical path at the position of ± 0.5 order.
An image is formed by light beam interference.

Light of 1.5 order or higher is weak in intensity, and the governing shape component is a component finer than 0.5 order light. Further, depending on the illumination conditions, the illumination side NA may be set to such a degree as to be blurred by the aperture.

Such an image has the following advantages. (D-1) In the case of conventional interference of three light beams, as shown in FIG. 5, due to the deterioration of the lens 51, either the +1 order or the −1 order is a part of the lens and the phase difference between the other two light beams. , Which caused a very uneven shape deformation on the left and right. On the other hand, in the case of two-beam interference, as shown in FIG. 7, the two beams are symmetrical with respect to the center of the optical axis, have many common optical path portions, and have a structure resistant to phase fluctuation. (D-2) Since interference is caused by two light beams, the interference fringe changes in the direction of focus advance are small, so that the focus advance is increased, which is particularly effective for deep hole drilling. (D-3) Since the common optical path portion having a small phase difference forms an image at the corner of the angle of view, deformation of the peripheral portion, which is often important for processing, is reduced.

FIG. 2 is a schematic view of a main part of a second embodiment of the present invention. FIG. 2 is a view for explaining a method of manufacturing a mask (photomask) having a phase shift according to the present invention.

The plurality of holes of the mask 28 are arranged in a one-dimensional direction. When counted from one end, light (laser light) passing through the even-numbered holes and the odd-numbered holes has a phase difference of λ / 2. Like that.

In this embodiment, an SiO ₂ thin film 25 having a half-wave phase difference is manufactured on the entire surface of the mask pattern 27, and the thin film on the mask pattern is removed by ablation processing. We are producing a phase difference distribution.

In the figure, reference numeral 21 denotes ArF as light source means.
It is a laser and emits coherent laser light 21a. Reference numeral 22 denotes a concave lens that expands a laser beam to expand a uniform illuminance area, 23 denotes a mask having an opening that defines a processing range on a surface of a workpiece, and 24 denotes a reduction lens, and the opening of the mask 23 is processed. It is projected on the object 25. 25 is a phase shift Si film having a thickness of λ / 2.
O ₂ film. 26 is a CaF ₂ substrate. 27 is a CaF ₂ substrate 2
6 is a mask pattern made of a Cr vapor-deposited film on the surface of which a plurality of holes are formed to form a hole row. 2
FIG. 8 is a sectional view of a principal part of a completed mask (photomask) having undergone phase shift.

In this embodiment, a SiO ₂ mask is formed on the back surface of a mask pattern 27 previously formed on a substrate 26 such as a commercially available product.
The film 25 is formed to a thickness of λ / 2. With this as a processing target, a phase shift mask is manufactured.

The laser beam 21 a emitted from the ArF laser (wavelength = 193 nm) 21 has a light beam diameter expanded by the concave lens 22, and a relatively uniform laser beam illuminates the mask 23.

The laser light cut out by the opening of the mask 23 is imaged on the SiO ₂ film 25 by the reduction projection lens 24.

[0054] imaging light ablating SiO ₂ film, by removing the SiO ₂ film corresponding to the even-numbered holes pattern of the mask pattern 27, as the phase difference is not generated in the laser beam passing therethrough I have.

After the processing of one hole is completed, the SiO ₂ film on the next even-numbered hole of the mask pattern 27 is removed by a mask driving device (not shown).

In this embodiment, the mask 28 having a phase shift is manufactured by projecting the opening of the mask 23 while sequentially scanning the SiO ₂ film 25 as described above.

The effects of the present embodiment are as follows. (E-1) ArF Kisima laser 21 is SiO 2 different from other lasers.
_Since the absorption of ₂ is large, it is possible to perform processing with good processing accuracy and processing speed. (E-2) By using CaF ₂ for the mask substrate 26, Ar
Since the substrate damage due to the F laser is reduced, the laser energy used for the SiO ₂ processing can be increased. As a result, both the processing speed and the processing accuracy are improved. (E-3) Mask pattern 27 with holes drilled on the back side in advance
Is formed, the laser beam passing through the hole hardly damages the Cr film. It can also be used for measuring the amount of light for monitoring the progress of SiO ₂ processing.

The phase shift mask is often used for a stepper projection optical system for manufacturing an LSI.
Manufacturing masks need to have a small (ka-1) pattern and high accuracy. (F-2) Patterns are not simple repetitions. (F-3) NA is very large.

However, during the ablation process, several μm
When a relatively large periodic structure exceeding m is manufactured, the structure on the mask exceeds 10 to 50 μm. Also, the NA may be low in many cases because the resolution is not so required.

Therefore, it is relatively easy to create a phase difference in a simple periodic structure.

However, for example, when the holes of an ink jet printer are to be collectively processed, since about 100 to 1000 holes are drilled, it has been very time-consuming to make the mask itself.

Therefore, in the present embodiment, first, a thin film having a phase difference is formed on the entire mask, and laser ablation is performed only on a portion in which a phase difference is required, thereby effectively manufacturing a phase difference mask. I have.

FIG. 3 is a schematic view of a main part of a third embodiment of the present invention. FIG. 3 is a view illustrating a method of manufacturing a phase shift mask according to the present invention.

In FIG. 3A, reference numeral 31 denotes a third harmonic generator (wavelength: 355 nm) of a pulse-oscillating YAG laser, which is the first light source means. Reference numeral 32 denotes an ArF laser, which is a second light source unit, and emits coherent laser light. Reference numeral 33 denotes a dichroic mirror that transmits the third harmonic laser light from the YAG laser 31 and reflects the laser light from the ArF laser 32. Reference numeral 34 denotes a concave lens that enlarges the light beam diameter of the laser beam to enlarge a uniform portion. Reference numeral 35 denotes a mask having an opening that defines a processing range. Reference numeral 36 denotes a reduction lens whose chromatic aberration has been corrected by the third harmonic laser light from the YAG laser 31 and laser light from the ArF laser 32, and 37 denotes a mask pattern made of a Cr vapor-deposited film provided on the SiO ₂ 38. , A plurality of rows of holes have been produced. Reference numeral 38 denotes a phase shift SiO ₂ film formed to a thickness of λ / 2. 39 is a CaF ₂ substrate. 40 is
It is principal part sectional drawing of the completed phase shift mask.

In this embodiment, the CaF ₂ substrate 3
9, a λ / 2-thick SiO ₂ film 38 is formed, and a Cr vapor-deposited film 37 is formed thereon. First, Y
The third harmonic wave from the AG laser 31 is sequentially irradiated, and the Cr film 37 is irradiated.
Create a hole pattern on top.

The light emitted from the YAG laser 31 passes through a dichroic mirror 33 and is spread by a concave lens 34, so that a uniform laser light irradiates the mask 35. The light cut out by the opening of the mask 35 passes through the reduction lens 3
6, the projection on the Cr vapor deposition film 37 is reduced, and the surface of the Cr film 37 is processed to form a hole pattern. The substrate 39 is sequentially scanned to form a required number of hole patterns on the Cr film 37.

After processing the Cr film 37 by the required number of holes, the SiO ₂ film 38 is processed by using the laser light from the ArF laser 32 as shown in FIG. 3B.

The laser light emitted from the ArF laser 32 is reflected by the dichroic mirror 33 and spread by the concave lens 34, and uniform light irradiates the mask 35. The light cut out by the opening of the mask 35 passes through the reduction lens 3
The odd-numbered Cr film 3 of the mask pattern which is reduced and projected by 6
The hole pattern is processed on the SiO ₂ film 38 below the hole pattern of No. 7,
Construct a phase difference of λ / 2 thickness. The substrate 39 is sequentially scanned to form holes having a required number of phase differences in the SiO ₂ film 38.

The effects of this embodiment are as follows. (G-1) Since the phase difference film 38 and the Cr film 37 are close to each other, a phase error due to a difference in position is very small. (G -2) Cr film 37 is to protect the non-working portion of the SiO ₂ film 38, it is less quality SiO ₂ film 38 is impaired. (G-3) Since a substantially coaxial processing system is used for the processing of the Cr film 37 and the processing of the retardation film 38, the positional deviation is very small.

[0070]

According to the present invention, even if the glass has low durability, the processed object can be stably illuminated by controlling the position and the amount of diffracted light by the photomask so as to be used as a lens for laser ablation processing. An optical processing machine and an optical processing method capable of processing can be achieved.

In addition, according to the present invention, by controlling the position and the amount of the diffracted light by the photomask, even glass having low durability can be used as a lens for laser ablation processing. At the same time, the depth of focus is deep,
Laser processing of uniform quality can be performed.

Further, a phase shift mask for laser processing can be obtained inexpensively and easily.

[Brief description of the drawings]

FIG. 1 is a schematic view of a main part of a first embodiment of the present invention.

FIG. 2 is a schematic diagram of a main part of a second embodiment of the present invention.

FIG. 3 is a schematic diagram of a main part of a third embodiment of the present invention.

FIG. 4 is a diagram showing an image forming principle of an optical system using a conventional mask.

FIG. 5 is an optical path diagram of diffracted light of an optical system using a conventional mask.

FIG. 6 is a diagram illustrating an image forming principle of an optical system using the mask of the present invention.

FIG. 7 is an optical path diagram of diffracted light of an optical system using the mask of the present invention.

FIG. 8 is a schematic view of an optical system of a conventional optical processing machine.

[Explanation of symbols]

1, KrF excimer laser 2, mirror for optical path adjustment 3, diffraction grating for light intensity profile adjustment 4, front lens for beam expander 5, aperture 6, rear lens for beam expander 7, prism for vertical reversal superposition 8, phase shift mask 9, front lens group of projection lens 10, aperture 11, rear lens group of projection lens 12, workpiece 21, ArF laser 22, concave lens 23, mask 24, reduction lens 25, SiO ₂ film 26, CaF ₂ substrate 27, Cr vapor deposition film mask pattern 28, phase shift mask 31, pulse YAG laser third harmonic wave generator 32, ArF laser 33, dichroic mirror 34, concave lens 35, mask 36, reduction projection lens 37, Cr vapor deposition film 38, SiO ₂ film 39, CaF ₂ substrate 40, the finished phase shift mask 70, the laser Source 71, prism unit 72, suitable photomask 73, the cylindrical lens 74, a convex lens 75, a photomask 76, the stop surface 77 of the projection lens, the projection lens 78, the processing object

Claims (6)

[Claims] An optical processing machine that illuminates a pattern on a mask with a light beam from a light source means, projects the pattern on the mask onto a workpiece by a projection lens, and optically processes the workpiece. An optical processing machine characterized by using a shift. 2. The optical processing machine according to claim 1, wherein the workpiece is irradiated with coherent light from the light source means, and the workpiece is optically processed by ablation. 3. The mask has an aperture pattern in which a plurality of apertures are arranged at a constant period, and the aperture patterns give a phase difference of λ / 2 to light passing every other aperture. The optical processing machine according to claim 1 or 2, wherein: 4. An optical processing method for projecting a pattern of a photomask onto a workpiece using coherent light and performing ablation processing into a predetermined shape, wherein a phase mask is used as the photomask. Processing method. 5. The shape to be processed into the workpiece is a hole or a groove arranged at substantially equal intervals, and a plurality of opening patterns on the mask are formed such that every other one of the aperture patterns is a half of the transmitted light. 5. The method according to claim 4, wherein a phase difference of one wavelength is provided.
Light processing method. 6. After manufacturing a thin film having a phase difference of a half wavelength on the entire surface of the mask, the thin film on the opening pattern of the mask is removed by ablation processing.
The optical processing method according to claim 4, wherein a mask having a desired phase difference distribution is used.