Laser device and method for manufacturing electronic device

Abstract

A laser device according to one aspect of the present disclosure includes: a master oscillator that outputs laser light; an amplifier that includes an optical resonator that amplifies the laser light output by the master oscillator in the optical resonator; and a phase shift structure that is disposed on an optical path closer to the amplifier than a midpoint of the optical path between the master oscillator and the amplifier. The phase shift structure includes a plurality of units having different amounts of phase shift of the laser light, and the arrangement interval of the units is greater than or equal to 80 μm and less than or equal to 275 μm.

Description

Technical Field

[0001] The present disclosure relates to a method for manufacturing a laser device and an electronic device. Background Art

[0002] In recent years, in semiconductor exposure devices, as semiconductor integrated circuits become smaller and more highly integrated, there is a demand for improved resolution. Therefore, the wavelength of light emitted from an exposure light source has been shortened. For example, as a gas laser device for exposure, a KrF excimer laser device that outputs a laser with a wavelength of about 248nm and an ArF excimer laser device that outputs a laser with a wavelength of about 193nm are used.

[0003] The spectral line width of the natural oscillation light of the KrF excimer laser device and the ArF excimer laser device is relatively wide, about 350 to 400 pm. Therefore, when the projection lens is constructed using a material that allows ultraviolet light such as KrF and ArF lasers to pass through, chromatic aberration sometimes occurs. As a result, the resolution may be reduced. Therefore, it is necessary to narrow the spectral line width of the laser output from the gas laser device to a level where chromatic aberration can be ignored. Therefore, in order to narrow the spectral line width, a narrowing module (Line Narrow Module: LNM) containing narrowing elements (etalon, grating, etc.) is sometimes provided in the laser resonator of the gas laser device. Hereinafter, a gas laser device with a narrowed spectral line width is referred to as a narrowed gas laser device.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: U.S. Patent No. 8,675,700

[0007] Patent Document 2: U.S. Patent No. 9904068 Summary of the invention

[0008] A laser device according to one aspect of the present disclosure comprises: a master oscillator that outputs laser light; an amplifier that has an optical resonator that amplifies the laser light output by the master oscillator in the optical resonator; and a phase shift structure that is arranged on an optical path that is closer to the amplifier than a midpoint of the optical path between the master oscillator and the amplifier, the phase shift structure having a plurality of units having different amounts of phase shift of the laser light, the units being arranged at intervals of not less than 80 μm and not more than 275 μm.

[0009] A laser device according to another aspect of the present disclosure comprises: a master oscillator that outputs laser light; an amplifier that has an optical resonator that amplifies the laser light output by the master oscillator in the optical resonator; and a phase shift structure that is disposed on an optical path closer to the amplifier than a midpoint of the optical path between the master oscillator and the amplifier, the phase shift structure having a plurality of units having different amounts of phase shift of the laser light, and assuming that the wavelength of the laser light is λ and the upper limit of the beam spread angle of the laser light output from the amplifier is θ max , the lower limit is θ min In the case of max ) and λ / θ min the following.

[0010] A method for manufacturing an electronic device according to another aspect of the present disclosure includes the following steps: using a laser device to generate laser light amplified by an amplifier, outputting the amplified laser light to an exposure device, and exposing the laser light on a photosensitive substrate in the exposure device to manufacture the electronic device, wherein the laser device comprises: a master oscillator that outputs laser light; an amplifier that has an optical resonator that amplifies the laser light output by the master oscillator in the optical resonator; and a phase-shifted structure that is arranged on an optical path that is closer to the amplifier than the midpoint of the optical path between the master oscillator and the amplifier, the phase-shifted structure having a plurality of units having different amounts of phase shift of the laser light, and the arrangement interval of the units is greater than 80 μm and less than 275 μm. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Hereinafter, several embodiments of the present disclosure will be described as simple examples with reference to the accompanying drawings.

[0012] Figure 1 The structure of an exemplary random phase plate is schematically shown.

[0013] Figure 2 An example of arrangement of cells when the cell shape is a hexagon is shown.

[0014] Figure 3 An example of a hexagonal unit cell is shown.

[0015] Figure 4 It is a side view schematically showing a configuration example of a laser device according to a comparative example.

[0016] Figure 5 yes Figure 4 A cross-sectional view of the cavity taken along line 5-5 is shown.

[0017] Figure 6 A configuration example of the laser device according to the first embodiment is schematically shown.

[0018] Figure 7 It is an explanatory diagram schematically showing an example of the arrangement position of the random phase plate.

[0019] Figure 8 A configuration example of a laser device according to the second embodiment is schematically shown.

[0020] Fig. 9 This is an enlarged cross-sectional view schematically showing a structural example of an optical element having a partial reflection film and a film having a random phase structure.

[0021] Fig.10 This is a plan view schematically showing a configuration example of a laser device according to a third embodiment.

[0022] Fig.11 This is a plan view schematically showing a configuration example of a laser device according to a fourth embodiment.

[0023] Fig.12 A configuration example of an exposure device is schematically shown. DETAILED DESCRIPTION

[0024] -Table of contents-

[0025] 1. Explanation of terms

[0026] 1.1 Random Phase Plate

[0027] 1.2 Cell size and aspect ratio

[0028] 2. Overview of Laser Device of Comparative Example

[0029] 2.1 Structure

[0030] 2.2 Action

[0031] 2.3 Topics

[0032] 3. Implementation Method 1

[0033] 3.1 Structure

[0034] 3.2 Spacing of random phase plates

[0035] 3.3 Specific numerical example 1

[0036] 3.4 Specific numerical example 2

[0037] 3.5 Generalization of spacing conditions

[0038] 3.6 Action

[0039] 3.7 Effects

[0040] 4. Implementation Method 2

[0041] 4.1 Structure

[0042] 4.2 Action

[0043] 4.3 Effects

[0044] 5. Implementation Method 3

[0045] 5.1 Structure

[0046] 5.2 Action

[0047] 5.3 Effects

[0048] 6. Implementation Method 4

[0049] 6.1 Structure

[0050] 6.2 Action

[0051] 6.3 Effects

[0052] 6.4 Variations

[0053] 7. About the manufacturing method of electronic devices

[0054] 8. Others

[0055] Below, the embodiments of the present disclosure are described in detail with reference to the accompanying drawings. The embodiments described below show several examples of the present disclosure and do not limit the content of the present disclosure. In addition, the structures and actions described in each embodiment are not necessarily all necessary for the structures and actions of the present disclosure. In addition, the same reference numerals are marked on the same structural elements and repeated descriptions are omitted.

[0056] 1. Explanation of terms

[0057] 1.1 Random Phase Plate

[0058] Figure 1 The structure of the random phase plate 10 is schematically shown. The random phase plate 10 is composed of two types of phase shift units, namely, a unit 12 with a transmission phase shift of 0 and a unit 14 with a transmission phase shift of π. The area ratio of the unit 12 with a shift of 0 and the unit 14 with a shift of π is, for example, 1:1. This area ratio may not be 1:1. Sometimes the phase shift unit is simply recorded as a "unit". The unit 12 is an example of a "first unit" in the present disclosure, and the unit 14 is an example of a "second unit" in the present disclosure.

[0059] Each unit is equal in shape and phase, and is composed of polygons. The shape of the speckle pattern changes according to the shape of the unit. The size or arrangement interval of the unit is called "pitch". The "size" mentioned here can also be called "length" or "size".

[0060] Figure 1 An example is shown in which the cells are square and the arrangement interval is equal to the size of the cells. Figure 1 In the case of Vand the length d in the H direction H In this case, the pitch in each of the V direction and the H direction is 80 μm. Figure 1 The shape of the unit cell of the random phase plate 10 shown is a regular polygon, but the shape of the unit cell is not limited to a regular polygon.

[0061] Figure 2 An example of the arrangement of the unit when the unit shape is hexagonal is shown. Figure 2 In the diagram, the longitudinal direction is defined as the V direction, and the lateral direction perpendicular to the V direction is defined as the H direction. Figure 2 Change the V-direction length d of the unit in this way V Length d in the H direction H The ratio of the width to the width of the unit (the aspect ratio of the unit) can be used to adjust the beam expansion angle in each direction.

[0062] 1.2 Cell size and aspect ratio

[0063] The unit of the random phase plate 10 is the smallest unit area of ​​a predetermined shape that becomes a concave area or a convex area of ​​a concave-convex pattern that imparts a phase difference to light. A plurality of units of a predetermined shape are periodically arranged on the element surface of the random phase plate 10. Here, "periodically" means regularly juxtaposed in a specific repetitive pattern in space. That is, the element surface of the random phase plate 10 is divided into a plurality of units, and each unit constitutes an area of ​​a concave portion or a convex portion. On the element surface of the random phase plate 10, areas of concave portions or convex portions are randomly arranged in space in units. A phase shift structure formed by randomly arranging a plurality of units with different phase shift amounts in space is called a "random phase structure". The random phase plate 10 is an example of an optical element having a random phase structure.

[0064] Regarding the shape of the unit, the "aspect ratio" is defined as follows. That is, a first direction and a second direction orthogonal to the first direction are defined in the in-plane direction parallel to the element surface of the random phase plate 10, and when the length of the unit in the first direction is d1 and the length of the unit in the second direction is d2, d2 / d1 is defined as the aspect ratio.

[0065] Figure 3 An example of a hexagonal unit cell is shown. Figure 3 In the embodiment, the longitudinal direction is the first direction and the transverse direction is the second direction. The first direction length d1 of the unit is the line interval of the first circumscribed parallel line parallel to the second direction relative to the outer line of the unit. The second direction length d2 of the unit is the line interval of the second circumscribed parallel line parallel to the first direction relative to the outer line of the unit. The first direction length d1 can be the configuration interval of the unit in the first direction. The second direction length d2 can be the configuration interval of the unit in the second direction.

[0066] In the case of a laser device having an oscillation-level laser (master oscillator) and an excimer amplifier (power oscillator) having an optical resonator, the first direction is determined by the relationship with the discharge direction (V direction) of the excimer amplifier. The first direction is a direction corresponding to the V direction, and the second direction is a direction corresponding to the H direction. "Corresponding directions" refer to relatively the same directions in each beam cross section at different positions on the optical path. For example, when there is a mirror or the like that changes the traveling direction of the laser light on the optical path between the random phase plate 10 and the excimer amplifier, the first direction in the random phase plate 10 and the discharge direction of the excimer amplifier may sometimes refer to different directions. However, it is understood that the first direction in the beam cross section of the laser light emitted from the random phase plate 10 and the V direction in the beam cross section of the laser light incident on the excimer amplifier are relatively the same directions.

[0067] When there is no mirror or the like for changing the traveling direction of the laser light on the optical path between the random phase plate 10 and the excimer amplifier, and the laser light emitted from the random phase plate 10 enters the excimer amplifier while maintaining the first direction in the beam cross section, the first direction may be parallel to the V direction.

[0068] The term "parallel" in this specification may include the concept of "approximately parallel" in a range that can be regarded as substantially the same as parallel in a technical sense. In addition, the term "perpendicular" or "orthogonal" in this specification may include the concept of "approximately perpendicular" or "approximately orthogonal" in a range that can be regarded as substantially the same as perpendicular or substantially the same as orthogonal in a technical sense.

[0069] 2. Overview of Laser Device of Comparative Example

[0070] 2.1 Structure

[0071] Figure 4 1 is a side view schematically showing a configuration example of a laser device 20 of a comparative example. The comparative example disclosed in the present invention is a method that the applicant recognizes to be known only to the applicant, and is not a publicly known example acknowledged by the applicant himself.

[0072] The laser device 20 includes a master oscillator 22, high reflective mirrors 24 and 26, and a power oscillator 28. The master oscillator 22 is a discharge-excitation excimer laser device including a narrowband module (LNM) 30, a cavity 32, and an output coupling mirror 34.

[0073] LNM 30 includes a prism 36 and a grating 38 for narrowing the spectrum width. Grating 38 is arranged in a Littrow configuration so that the incident angle and the diffraction angle coincide with each other. Output coupling mirror 34 is a partial reflection mirror with a reflectivity of 20% to 30%. Output coupling mirror 34 is arranged so as to form an optical resonator together with LNM 30.

[0074] The cavity 32 is arranged on the optical path of the optical resonator. The cavity 32 includes a pair of discharge electrodes 40a, 40b and two windows 42, 44 for laser light to pass through. Laser gas is introduced into the cavity 32. The laser gas is an excimer laser gas including a rare gas, a halogen gas and a buffer gas. The rare gas can be, for example, argon (Ar) or krypton (Kr) gas. The halogen gas can be, for example, fluorine (F2) gas. The buffer gas can be, for example, neon (Ne) gas. A voltage is applied between the discharge electrodes 40a, 40b by a power supply not shown in the figure. The power supply can be a pulse power module (PPM) including a switch and a charging capacitor.

[0075] The high reflection mirror 24 and the high reflection mirror 26 are arranged on an optical path between the master oscillator 22 and the power oscillator 28 so that the laser light output from the master oscillator 22 is incident on the power oscillator 28 .

[0076] The power oscillator 28 is an excimer amplifier including a rear mirror 50, a cavity 52 and an output coupling mirror 54. The rear mirror 50 and the output coupling mirror 54 constitute an optical resonator, and the cavity 52 is arranged on the optical path of the optical resonator. The structure of the cavity 52 can be the same as the structure of the cavity 32 of the master oscillator 22. The cavity 52 includes a pair of discharge electrodes 60a, 60b and two windows 62, 64. Laser gas is introduced into the cavity 52. ​​The rear mirror 50 is a partial reflection mirror with a reflectivity of 80% to 90%. The output coupling mirror 54 is a partial reflection mirror with a reflectivity of 20% to 30%.

[0077] exist Figure 4 In the embodiment, the optical path axis direction of the laser light output from the power oscillator 28 is the Z direction. Two directions substantially orthogonal to the Z direction may be the H direction and the V direction. The H direction is perpendicular to the Figure 1 The direction is roughly perpendicular to the paper plane.

[0078] Figure 5 yes Figure 4 The cross-sectional view of the cavity 52 at line 5-5 is shown. Figure 5 As shown, the discharge electrodes 60a and 60b are arranged opposite to each other in the V direction with the discharge space 66 therebetween. The space between the discharge electrodes 60a and 60b is the discharge space 66. The "discharge space" is also called the "discharge region". The V direction corresponds to the discharge direction. Figure 4 The same is true for the cavity 32 of the master oscillator 22 shown, and the space between the discharge electrodes 40 a and 40 b serves as a discharge space 46 .

[0079] 2.2 Action

[0080] When a voltage is applied between discharge electrodes 40 a and 40 b in cavity 32 of master oscillator 22 to generate discharge, laser gas is excited, and pulsed laser light narrowed in bandwidth by an optical resonator composed of output coupling mirror 34 and LNM 30 is output from output coupling mirror 34 .

[0081] The pulsed laser light is transmitted via the high reflective mirrors 24 and 26, and is incident on the rear mirror 50 of the power oscillator 28 as seed light. The seed light after passing through the rear mirror 50 is incident on the cavity 52. ​​When the seed light is incident on the cavity 52, discharge is generated between the discharge electrodes 60a and 60b. As a result, the laser gas in the cavity 52 is excited, and the seed light is amplified by the optical resonator composed of the output coupling mirror 54 and the rear mirror 50, and the amplified laser light is output from the output coupling mirror 54 as output laser light LP.

[0082] 2.3 Topics

[0083] The rear mirror 50 of the power oscillator 28 is a partial reflector with a reflectivity of 80% to 90%. Therefore, part of the laser light output by the master oscillator 22 is reflected by the rear mirror 50 and returns to the master oscillator 22. The laser light returned to the master oscillator 22 is called "return light". The return light RL may have an adverse effect on the stability of the output energy and wavelength.

[0084] That is, the return light RL returns to the master oscillator 22 again, and the light enters the optical resonator again. As a result, the return light RL increases the thermal load of the master oscillator 22 , thereby causing the performance of the master oscillator 22 to become unstable.

[0085] 3. Implementation Method 1

[0086] 3.1 Structure

[0087] Figure 6 An example configuration of the laser device 100 according to the first embodiment is schematically shown. Figure 6 The structure shown is Figure 4 The differences are explained.

[0088] The laser device 100 has a random phase plate 10 on the optical path between the rear mirror 50 and the high reflector 26. The random phase plate 10 may also be arranged in the housing of the power oscillator 28. It is preferable that the distance between the random phase plate 10 and the rear mirror 50 is as close as possible. By making the distance between the random phase plate 10 and the rear mirror 50 close, the reduction in the injection efficiency of the seed light into the optical resonator of the power oscillator 28 can be suppressed, and the distance between the random phase plate 10 and the output coupling mirror 34 of the master oscillator 22 becomes relatively far, so that the beam of the return light RL is expanded by the random phase plate 10, and accordingly, the amount of light re-incident to the master oscillator 22 can be reduced. The random phase plate 10 is an example of a "phase shift structure" in the present disclosure. The power oscillator 28 is an example of an "amplifier" in the present disclosure. The high reflectors 24 and 26 are examples of "multiple mirrors" in the present disclosure. The high reflector 26 is an example of "the mirror closest to the optical resonator among the multiple mirrors" in the present disclosure.

[0089] The laser device 100 may also be provided with a hole (not shown) near the output coupling mirror 34 of the master oscillator 22 to shield the return light RL amplified by the random phase plate 10. The hole may be of substantially the same size as the beam shape of the laser light output from the master oscillator 22.

[0090] Figure 7 : is an explanatory diagram schematically showing an example of the arrangement position of the random phase plate 10. The random phase plate 10 is arranged on the optical path closer to the rear mirror 50 (closer to the rear mirror 50) than the midpoint of the optical path between the output coupling mirror 34 and the rear mirror 50. Figure 7 In FIG. 1 , the Z axis is used to represent the optical path axis between the output coupling mirror 34 and the rear mirror 50, and the distance between the output coupling mirror 34 and the rear mirror 50 is set to L. The position on the optical path "closer to the rear mirror 50 side than the midpoint" is an example of the position on the optical path "closer to the amplifier side than the midpoint" in the present disclosure. It is preferred that the distance Lrp between the random phase plate 10 and the rear mirror 50 is within 20 cm. The closer the random phase plate 10 is to the output coupling mirror 34 of the master oscillator 22, the weaker the effect of return light suppression. Therefore, it is preferred that the random phase plate 10 is arranged as close to the rear mirror 50 as possible. Alternatively, a structure in which the rear mirror 50 and the random phase plate 10 are integrated may be adopted. As in Embodiment 2 described later, a film with a random phase structure may be coated on the back side of the partial reflection film side of the rear mirror 50, and a partial reflection film and a film with a random phase structure may be coated on the same optical element.

[0091] By placing the random phase plate 10 at a relatively short distance of 20 cm or less from the rear mirror 50 , the distance between the random phase plate 10 and the output coupling mirror 34 of the master oscillator 22 becomes relatively long, thereby sufficiently ensuring the effect of suppressing the return light from the master oscillator 22 .

[0092] 3.2 Spacing of random phase plates

[0093] The pitch of the random phase plate 10 is determined from the following viewpoint based on the beam spread angle of the laser light emitted from the power oscillator 28. The beam spread angle of the output laser light LP from the power oscillator 28 in a state where the random phase plate 10 does not exist on the optical path between the master oscillator 22 and the power oscillator 28 is defined as θ AH ,θ AV θ AH is the beam spread angle in the H direction, θ AV The beam expansion angles in the H and V directions after passing through the random phase plate 10 are defined as θ RPP_H ,θ RPP_V θ RPP_H ,θ RPP_V The following formulas are used to approximate them respectively.

[0094] [Mathematical formula 1]

[0095]

[0096] [Mathematical formula 2]

[0097]

[0098] Where λ is the wavelength. H is the length of the unit in the H direction, d V is the length of the element in the V direction.

[0099] The beam expansion angle is respectively AH ,θ AV The pitch of the random phase plate 10 is selected in a substantially equal manner, that is, in a manner satisfying the following equations (3) and (4).

[0100] [Mathematical formula 3]

[0101] θ AH ≈θ RPP_H (3)

[0102] [Formula 4]

[0103] θ AV ≈θ RPP_V (4)

[0104] The expression "substantially equal" means that the difference within a predetermined tolerance range is allowed to be approximated. RPP_H Relative to θ AH The difference within the specified tolerance range is approximately equal to θ AH The length d of the unit in the H direction is selected by H, with θ RPP_V Relative to θ AV The difference within the specified tolerance range is approximately equal to θ AV The length d of the unit in the V direction is selected by V .

[0105] The prescribed allowable range can be appropriately set within the range of obtaining the technical effect. It can be the same allowable range in the V direction and the H direction, or it can be a different allowable range for each direction. For example, the allowable range can be set to θ RPP_H With θ AH The difference is in θ AH can also be set to θ RPP_H With θ AH The difference is within 0.1 millirad [mrad], etc., and can also be set to θ RPP_H In θ AH The description of “selecting” the pitch means that the random phase plate 10 with such a pitch is used in the laser device 100, and includes the concepts of “determining”, “fixing”, and “designing” the pitch of the random phase plate 10 used in the laser device 100.

[0106] By satisfying the conditions of equations (3) and (4), the beam spread angle after passing through the random phase plate 10 substantially matches the spread angle of the laser light output from the master oscillator 22 , thereby suppressing a decrease in light injection efficiency into the power oscillator 28 .

[0107] 3.3 Specific numerical example 1

[0108] As the laser device 100 , an ArF excimer laser device with a wavelength λ=193 nm is assumed, and the beam profile in the H direction is a Gaussian distribution, and the beam profile in the V direction is a flat top.

[0109] The beam spread angle θ in each of the H direction and the V direction of the laser light output from the ArF excimer laser device is AH ,θ AV Typical values ​​of roughly satisfy the following ranges.

[0110] H direction: 0.8mrad≤θ AH ≤2.4mrad (5)

[0111] V direction: 0.7mrad≤θ AV ≤1.6mrad (6)

[0112] On the other hand, the beam spread angle θ of the laser beam emitted from the random phase plate 10 is RPP There is the following relationship between the spacing d of the units.

[0113] θRPP =λ / d (7)

[0114] When using the relationship in equation (7) to calculate the spacing d that satisfies equations (3) and (5), H When the condition is met, it becomes the range shown in the following formula (8).

[0115] 80μm≤d H ≤241μm (8)

[0116] Similarly, when using the relationship of formula (7) to calculate the spacing d that satisfies formula (4) and formula (6) V When the condition is met, it becomes the range shown in the following formula (9).

[0117] 120μm≤d V ≤275μm (9)

[0118] When the H direction and the V direction are collectively processed according to the equations (8) and (9), the preferred range of the pitch d of the random phase plate 10 becomes the range shown in the following equation (10).

[0119] 80μm≤d≤275μm (10)

[0120] θ in formula (5) AH and θ in formula (6) AV are respectively “θ A ” is an example of “the beam spread angle of the laser beam emitted from the amplifier”. “2.4 mrad” in equation (5) and “1.6 mrad” in equation (6) are respectively “θ max ” is an example of “the upper limit of the beam spread angle of the laser output from the amplifier”. “0.8 mrad” in equation (5) and “0.7 mrad” in equation (6) are respectively “θ min ” is an example of “the lower limit of the beam spread angle of the laser output from the amplifier”. In addition, “2.4 mrad” in equation (5) is “θ AH1 ” is an example of “the upper limit of the beam spread angle in the H direction of the laser light output from the amplifier”. The “1.6 mrad” in equation (6) is the “θ AV1 ” is an example of “the upper limit of the beam spread angle in the V direction of the laser light output from the amplifier”. The “0.8 mrad” in equation (5) is the “θ AH2 ” is an example of “the lower limit of the beam spread angle in the H direction of the laser light output from the amplifier”. The “0.7 mrad” in equation (6) is the “θ AV2 ” is an example of “the lower limit of the beam spread angle in the V direction of the laser light output from the amplifier”.

[0121] 3.4 Specific numerical example 2

[0122] Regarding the beam spread angle conditions respectively shown in equations (5) and (6), when it is assumed that the upper limit of each numerical range is allowed to be extended to a range of 1.5 times, the conditions become the following equations (11) and (12).

[0123] H direction: 0.8mrad≤θ AH ≤3.6mrad (11)

[0124] V direction: 0.7mrad≤θ AV ≤2.4mrad (12)

[0125] When the conditions of equations (11) and (12) are applied instead of equations (5) and (6), the spacing d satisfying equations (3) and (11) is calculated using the relationship of equation (7): H When the condition is met, it becomes the range shown in the following formula (13).

[0126] 53μm≤d H ≤241μm (13)

[0127] Similarly, when using the relationship in equation (7) to calculate the spacing d that satisfies equations (4) and (12), V When the condition is met, it becomes the range shown in the following formula (14).

[0128] 80μm≤d V ≤275μm (14)

[0129] When the H direction and the V direction are collectively processed according to the equations (13) and (14), the preferred range of the spacing d becomes the range shown in the following equation (15).

[0130] 53μm≤d≤275μm (15)

[0131] 3.5 Generalization of spacing conditions

[0132] As can be understood from the consideration of the above-mentioned specific numerical example 1, the beam spread angle θ of the laser beam output from the power oscillator 28 of the laser device 100 is A The upper limit value is set to θ Amax , set the lower limit to θ Amin In the case of , the preferred range of the spacing d is expressed, for example, by the following formula (16).

[0133] λ / θ Amax ≤d≤λ / θ Amin (16)

[0134] As can be understood from the consideration of the above-mentioned specific numerical example 2, the beam spread angle θ of the laser light emitted from the random phase plate 10 is RPP , before allowing θ Amax When d is 1.5 times greater than d, the preferred range of the spacing d is expressed, for example, by the following formula (17).

[0135] λ / (1.5·θ Amax )≤d≤λ / θ Amin (17)

[0136] According to equations (16) and (17), the minimum value of the selectable range of the spacing d is determined by the beam spread angle θ of the laser light output from the power oscillator 28: A The upper limit value θ Amax The minimum value (lower limit) of the selectable range of the spacing d is determined by RPP With θ Amax The difference between θ and θ varies depending on the extent to which it is allowed. RPP , before allowing θ Amax When k times the value of , the preferred range of the spacing d becomes the following formula (18).

[0137] λ / (k·θ Amax )≤d≤λ / θ Amin (18)

[0138] Here, k is a value greater than or equal to 1, and may be a value satisfying, for example, 1≤k≤1.5.

[0139] According to the concept described using equations (16) to (18), the random phase plate 10 having a pitch d that meets the conditions is used in the laser device 100 .

[0140] 3.6 Action

[0141] The seed light output from the master oscillator 22 passes through the random phase plate 10 and enters the optical resonator of the power oscillator 28. The seed light reflected by the rear mirror 50 and a part of the laser light amplified by the optical resonator of the power oscillator 28 are emitted from the rear mirror 50 as return light RL. The random phase plate 10 plays a role in expanding the beam spread angle of the return light RL emitted from the rear mirror 50 toward the master oscillator 22. The power oscillator 28 is an example of an "amplifier" in the present disclosure.

[0142] 3.7 Effects

[0143] According to the laser device 100 of the first embodiment, the beam spread angle θ of the laser beam emitted from the random phase plate 10 is RPP As close to θ as possible AThe spacing of the random phase plate 10 is selected in a manner to suppress the reduction of the light injection efficiency into the optical resonator of the power oscillator 28. On the other hand, the return light RL is diffused by the random phase plate 10, so the amount of light returned to the master oscillator 22 is reduced. Thus, it is possible to suppress the deterioration of the stability of the energy and wavelength caused by the return light RL. In addition, Figure 2 As explained above, let the V-direction length d of the unit be V and the length d in the H direction H The cell shapes with different aspect ratios can effectively suppress a decrease in the light injection efficiency into the optical resonator of the power oscillator 28 .

[0144] 4. Implementation Method 2

[0145] 4.1 Structure

[0146] Figure 8 An example of the structure of the laser device 102 according to the second embodiment is schematically shown. Figure 8 The structure shown is Figure 6 The differences are explained. Figure 8 The laser device 102 shown in the figure is provided with a single optical element 70 having both functions, instead of the combination of the random phase plate 10 and the rear mirror 50 .

[0147] Fig. 9 1 is an enlarged cross-sectional view schematically showing a structural example of an optical element 70 having a partial reflection film and a film with a random phase structure. The optical element 70 is a rear mirror with a random phase structure, and a partial reflection film 72 is applied on the first surface of a substrate 71, and a film 80 with a random phase structure is applied on the second surface opposite to the first surface. The substrate 71 is made of a material that transmits light of ultraviolet wavelengths. The material of the substrate 71 can be, for example, synthetic quartz, CaF2, etc.

[0148] An optical resonator is formed by the partial reflection film 72 and the output coupling mirror 54. The film 80 having a random phase structure has the same structure as the unit cell in the random phase plate 10.

[0149] 4.2 Action

[0150] The seed light output from the master oscillator 22 passes through the optical element 70 and enters the optical resonator of the power oscillator 28. A portion of the laser light amplified in the optical resonator of the power oscillator 28 is emitted as return light RL from the optical element 70. The film 80 having the random phase structure plays a role in expanding the beam spread angle of the return light RL emitted from the optical element 70 toward the master oscillator 22.

[0151] 4.3 Effects

[0152] According to the laser device 102 of the second embodiment, the decrease in the light injection efficiency into the optical resonator of the power oscillator 28 is suppressed, similarly to the laser device 100 of the first embodiment. In addition, the return light RL is diffused by the film 80 having the random phase structure, so the amount of light returned to the master oscillator 22 is reduced. Thus, the deterioration of the stability of the energy and wavelength due to the return light RL can be suppressed.

[0153] According to Embodiment 2, the partial reflection film 72 and the random phase structure film 80 are provided on the same optical element 70, so that the reduction in light injection efficiency is further suppressed compared with Embodiment 1. In addition, according to Embodiment 2, the deterioration of the stability of energy and wavelength caused by the return light RL can be further suppressed compared with Embodiment 1.

[0154] 5. Implementation Method 3

[0155] 5.1 Structure

[0156] Fig.10 1 is a plan view schematically showing a configuration example of the laser device 103 according to the third embodiment. Fig.10 The structure shown is Figure 6 The differences are explained. Fig.10 The laser device 103 shown will Figure 6 The power oscillator 28 is partially replaced by a ring resonator type amplifier 128.

[0157] Right now, Fig.10 The laser device 103 shown has a ring resonator amplifier 128. The amplifier 128 includes a cavity 152, high reflection mirrors 121, 122, 123, and an output coupling mirror 154. The cavity 152 includes a pair of discharge electrodes 160a, 160b and two windows 162, 164. The discharge electrodes 160a, 160b are connected to the Fig.10 The cavity 152 is arranged to be spaced apart from each other in a direction perpendicular to the paper surface. Laser gas is introduced into the cavity 152. The output coupling mirror 154 is a partial reflection mirror. The output coupling mirror 154 and the high reflection mirrors 121, 122, and 123 form a ring-shaped optical resonator (ring resonator). The cavity 152 is arranged on the optical path of the ring resonator.

[0158] A random phase plate 10 is arranged on the optical path between the master oscillator 22 and the output coupling mirror 154. It is preferred that the random phase plate 10 be arranged as close to the output coupling mirror 154 as possible. Figure 7 As described above, the random phase plate 10 is preferably disposed within 20 cm from the output coupling mirror 154 .

[0159] 5.2 Action

[0160] The seed light output from the master oscillator 22 is incident on the output coupling mirror 154 of the amplifier 128 via the random phase plate 10. The surface of the output coupling mirror 154 on the side into which the seed light is incident becomes the output coupling mirror (not shown) of the master oscillator 22 (see FIG. Figure 6 A portion of the seed light incident on the output coupling mirror 154 is reflected by the high reflection mirror 121 through the output coupling mirror 154. The seed light reflected by the high reflection mirror 121 passes through the window 162 and travels toward the discharge space between the discharge electrodes 160a and 160b.

[0161] When the seed light is present in the discharge space, control is performed to generate discharge between the electrodes, thereby amplifying the seed light. The amplified laser light is emitted from the cavity 152 via the window 164. The laser light emitted from the window 164 is highly reflected by the high-reflection mirrors 122 and 123, and travels to the discharge space in the cavity 152 via the window 164 again to be amplified.

[0162] The amplified laser light is emitted from the cavity 152 through the window 162. The amplified laser light emitted from the window 162 is incident on the output coupling mirror 154. A part of the amplified laser light incident on the output coupling mirror 154 is transmitted through the output coupling mirror 154 and emitted from the amplifier 128 toward an exposure device (not shown) as output laser light LP.

[0163] Another part of the amplified laser light incident on the output coupling mirror 154 is reflected by the output coupling mirror 154 and returns to the ring resonator as feedback light. In addition, a part of the laser light amplified by the ring resonator is emitted from the output coupling mirror 154 toward the master oscillator 22 as return light RL.

[0164] The random phase plate 10 plays a role in expanding the beam spread angle of the return light RL, similarly to the first embodiment.

[0165] 5.3 Effects

[0166] The laser device 103 according to the third embodiment can achieve the same effects as the laser device 100 according to the first embodiment.

[0167] 6. Implementation Method 4

[0168] 6.1 Structure

[0169] Fig.11 1 is a plan view schematically showing a configuration example of a laser device 104 according to a fourth embodiment. Fig.11 The structure shown is Figure 6 The differences are explained. Fig.11 The laser device 104 shown becomes Figure 6The master oscillator 22 in the embodiment is partially replaced by the ultraviolet solid laser device 112. The ultraviolet solid laser device 112 is an example of the "master oscillator" in the present disclosure. Other structures may be the same as Figure 6 same.

[0170] The detailed structure of the ultraviolet solid laser device 112 is not shown in the figure, but the ultraviolet solid laser device 112 can be, for example, a laser device obtained by combining a narrow-band titanium sapphire laser and a nonlinear crystal. In addition, the ultraviolet solid laser device 112 can be, for example, a laser device obtained by combining a semiconductor laser and a nonlinear crystal. The nonlinear crystal is used for the wavelength conversion unit.

[0171] By Figure 7 The output coupling mirror 34 described in the above is replaced by a nonlinear crystal for generating an output wavelength in the ultraviolet solid laser device 112, and the output coupling mirror 34 is replaced by a nonlinear crystal for generating an output wavelength in the ultraviolet solid laser device 112. Figure 7 The contents of the description are also applied to the structure of the laser device 104 in the fourth embodiment.

[0172] 6.2 Action

[0173] The seed light output from the ultraviolet solid-state laser device 112 passes through the random phase plate 10 and enters the optical resonator of the power oscillator 28. A part of the laser light amplified in the optical resonator of the power oscillator 28 is emitted as the return light RL from the rear mirror 50. The random phase plate 10 plays a role in expanding the beam spread angle of the return light RL emitted from the rear mirror 50 toward the ultraviolet solid-state laser device 112.

[0174] When the return light RL returns to the nonlinear crystal of the wavelength converter, the light becomes a heat load and the oscillation performance may become unstable. However, the random phase plate 10 diffuses the return light RL, thereby suppressing the amount of light returning to the nonlinear crystal of the wavelength converter.

[0175] 6.3 Effects

[0176] According to the laser device 104 of the fourth embodiment, the reduction in the light injection efficiency of the optical resonator of the power oscillator 28 is suppressed, and the return light RL is diffused by the random phase plate 10, so the amount of light returned to the ultraviolet solid-state laser device 112 is reduced. As a result, the deterioration of the stability of energy and wavelength caused by the return light RL can be suppressed. In addition, according to the fourth embodiment, the degradation of optical elements such as nonlinear crystals can be suppressed.

[0177] 6.4 Variations

[0178] Can also replace Fig.11 The random phase plate 10 and the rear mirror 50 in the laser device 104 shown in the figure are replaced by the rear mirror with a random phase structure, that is, the optical element 70 described in the second embodiment.

[0179] 7. About the manufacturing method of electronic devices

[0180] Fig.12 The structure example of the exposure device 300 is schematically shown. The exposure device 300 includes an illumination optical system 304 and a projection optical system 306. The illumination optical system 304 illuminates the mask pattern of the mask (not shown) arranged on the mask stage RT by the laser light incident from the laser device 100. The projection optical system 306 performs reduced projection of the laser light transmitted through the mask so as to form an image on the workpiece (not shown) arranged on the workpiece stage WT. The workpiece is a photosensitive substrate such as a semiconductor wafer coated with a photoresist.

[0181] The exposure device 300 moves the mask stage RT and the work stage WT synchronously and in parallel, thereby exposing the workpiece to a laser reflecting the mask pattern. After the mask pattern is transferred to the semiconductor wafer through the above exposure process, a semiconductor device can be manufactured through multiple processes. The semiconductor device is an example of an "electronic device" in the present disclosure. The laser device 102, 103 or 104 described in embodiments 2 to 4 may be used instead of the laser device 100.

[0182] 8. Others

[0183] The above description is not limiting but simply illustrative. Therefore, those skilled in the art will appreciate that changes can be made to the embodiments of the present disclosure without departing from the claims. In addition, those skilled in the art will appreciate that the embodiments of the present disclosure can be used in combination.

[0184] Unless explicitly stated otherwise, the terms used in this specification and claims as a whole should be interpreted as "non-limiting" terms. For example, terms such as "including", "having", "having", and "having" should be interpreted as "excluding the existence of structural elements other than the structural elements to be recorded". In addition, the modifier "one" should be interpreted as meaning "at least one" or "one or more". In addition, terms such as "at least one of A, B, and C" should be interpreted as "A", "B", "C", "A+B", "A+C", "B+C", or "A+B+C". Furthermore, it should be interpreted as also including combinations of them and parts other than "A", "B", and "C".

Claims

1. A laser device, comprising: a master oscillator, whose output is laser; an amplifier having an optical resonator in which the laser light output by the master oscillator is amplified; as well as a phase shift structure arranged on the optical path closer to the amplifier than a midpoint of the optical path between the master oscillator and the amplifier, The phase shift structure includes a plurality of units having different phase shift amounts of the laser light. The arrangement interval of the units is 80 μm or more and 275 μm or less. The laser device has: A rear mirror having a partially reflecting film coated on a first surface and a film having the phase shift structure coated on a second surface opposite to the first surface; as well as Output coupling mirror, The optical resonator is formed by the partially reflective film and the output coupling mirror.

2. A laser device, comprising: a master oscillator, whose output is laser; an amplifier having an optical resonator in which the laser light output by the master oscillator is amplified; as well as a phase shift structure arranged on the optical path closer to the amplifier than a midpoint of the optical path between the master oscillator and the amplifier, The phase shift structure includes a plurality of units having different phase shift amounts of the laser light. The arrangement interval of the units is 80 μm or more and 275 μm or less. The amplifier includes a pair of discharge electrodes disposed opposite to each other across a discharge space through which the laser beam passes. Assuming that the traveling direction of the laser light emitted from the amplifier is the Z direction, the discharge direction of the pair of discharge electrodes is the V direction, the direction orthogonal to the V direction and the Z direction is the H direction, the in-plane direction of the phase-shifted structure corresponding to the V direction of the beam cross section of the laser light emitted from the amplifier is the first direction, and the in-plane direction of the phase-shifted structure corresponding to the H direction of the beam cross section is the second direction, When the beam spread angle of the laser light output from the amplifier in the V direction is θ AV The beam expansion angle of the laser in the H direction is θ AH The beam spread angle of the laser beam in the first direction after passing through the phase shift structure is θ RPP_V The beam spread angle of the laser beam in the second direction after passing through the phase shift structure is θ RPP_H In the case of The phase shift configuration is θ RPP_V With θ AV The difference and θ RPP_H With θ AH The arrangement interval of the units in each of the first direction and the second direction is selected so that the difference is within a predetermined allowable range. Assuming that the wavelength of the laser light is λ, and the upper limit of the beam spread angle of the laser light output from the amplifier in the V direction is θ AV1 The upper limit of the beam spread angle of the laser light output from the amplifier in the H direction is θ AH1 In the case of The arrangement interval of the units in the first direction is λ / (1.5·θ AV1 )above, The arrangement interval of the units in the second direction is λ / (1.5·θ AH1 )above.

3. A laser device, comprising: a master oscillator, whose output is laser; an amplifier having an optical resonator in which the laser light output by the master oscillator is amplified; as well as a phase shift structure arranged on the optical path closer to the amplifier than a midpoint of the optical path between the master oscillator and the amplifier, The phase shift structure includes a plurality of units having different phase shift amounts of the laser light. The arrangement interval of the units is 80 μm or more and 275 μm or less. The amplifier includes a pair of discharge electrodes disposed opposite to each other across a discharge space through which the laser beam passes. Assuming that the traveling direction of the laser light emitted from the amplifier is the Z direction, the discharge direction of the pair of discharge electrodes is the V direction, the direction orthogonal to the V direction and the Z direction is the H direction, the in-plane direction of the phase-shifted structure corresponding to the V direction of the beam cross section of the laser light emitted from the amplifier is the first direction, and the in-plane direction of the phase-shifted structure corresponding to the H direction of the beam cross section is the second direction, When the beam spread angle of the laser light output from the amplifier in the V direction is θ AV The beam expansion angle of the laser in the H direction is θ AH The beam spread angle of the laser beam in the first direction after passing through the phase shift structure is θ RPP_V The beam spread angle of the laser beam in the second direction after passing through the phase shift structure is θ RPP_H In the case of The phase shift configuration is θ RPP_V With θ AV The difference and θ RPP_H With θ AH The arrangement interval of the units in each of the first direction and the second direction is selected so that the difference is within a predetermined allowable range. Assuming that the wavelength of the laser light is λ, and the lower limit of the beam spread angle of the laser light output from the amplifier in the V direction is θ AV2 The lower limit of the beam spread angle of the laser light output from the amplifier in the H direction is θ AH2 In the case of The arrangement interval of the units in the first direction is λ / θ AV2 the following, The arrangement interval of the units in the second direction is λ / θ AH2 the following.

4. A laser device, comprising: a master oscillator, whose output is laser; an amplifier having an optical resonator in which the laser light output by the master oscillator is amplified; as well as a phase shift structure arranged on the optical path closer to the amplifier than a midpoint of the optical path between the master oscillator and the amplifier, The phase shift structure includes a plurality of units having different phase shift amounts of the laser light. The arrangement interval of the units is 80 μm or more and 275 μm or less. Assuming that the beam expansion angle of the laser emitted from the amplifier is θ A The beam expansion angle of the laser after passing through the phase shift structure is θ RPP In the case of The phase shift configuration is θ RPP With θ A The difference is in θ A Within 10% or within 0.1 mrad, or θ RPP In θ A The configuration interval of the unit is selected in a manner within 1.5 times of .

5. The laser device according to claim 1 or 4, wherein: The amplifier includes a pair of discharge electrodes disposed opposite to each other across a discharge space through which the laser beam passes. When the traveling direction of the laser light emitted from the amplifier is the Z direction, the discharge direction of the pair of discharge electrodes is the V direction, the direction orthogonal to the V direction and the Z direction is the H direction, the in-plane direction of the phase shift structure corresponding to the V direction of the beam cross section of the laser light emitted from the amplifier is the first direction, and the in-plane direction of the phase shift structure corresponding to the H direction of the beam cross section is the second direction, The length of the unit in the first direction is different from the length in the second direction.

6. A laser device, comprising: a master oscillator, whose output is laser; an amplifier having an optical resonator in which the laser light output by the master oscillator is amplified; as well as a phase shift structure arranged on the optical path closer to the amplifier than a midpoint of the optical path between the master oscillator and the amplifier, The phase shift structure includes a plurality of units having different phase shift amounts of the laser light. The arrangement interval of the units is 80 μm or more and 275 μm or less. The amplifier includes a pair of discharge electrodes disposed opposite to each other across a discharge space through which the laser beam passes. Assuming that the traveling direction of the laser light emitted from the amplifier is the Z direction, the discharge direction of the pair of discharge electrodes is the V direction, the direction orthogonal to the V direction and the Z direction is the H direction, the in-plane direction of the phase-shifted structure corresponding to the V direction of the beam cross section of the laser light emitted from the amplifier is the first direction, and the in-plane direction of the phase-shifted structure corresponding to the H direction of the beam cross section is the second direction, When the beam spread angle of the laser light output from the amplifier in the V direction is θ AV The beam expansion angle of the laser in the H direction is θ AH The beam spread angle of the laser beam in the first direction after passing through the phase shift structure is θ RPP_V The beam spread angle of the laser beam in the second direction after passing through the phase shift structure is θ RPP_H In the case of The phase shift configuration is θ RPP_V With θ AV The difference is in θ AV Within 10% of θ RPP_H With θ AH The difference is in θ AH Within 10% of θ RPP_V With θ AV The difference and θ RPP_H With θ AH The difference is within 0.1 milliradian, or θ RPP_V In θ AV Within 1.5 times of θ RPP_H In θ AH The arrangement interval of the units in each of the first direction and the second direction is selected in a manner within 1.5 times of.

7. The laser device according to any one of claims 1 to 4 and 6, wherein: The laser device further includes a plurality of mirrors, the plurality of mirrors being arranged on the optical path between the master oscillator and the optical resonator. The phase shift structure is arranged between a mirror closest to the optical resonator among the plurality of mirrors and the optical resonator.

8. The laser device according to any one of claims 2 to 4 and 6, wherein: The optical resonator has a partially reflecting mirror that emits return light toward the master oscillator, The distance between the partial reflector and the phase shifting structure is within 20 cm.

9. The laser device according to claim 8, wherein: The optical resonator has an output coupling mirror and a rear mirror as the partial reflection mirror.

10. The laser device according to any one of claims 1 to 4 and 6, wherein: The plurality of units include a first unit whose phase offset is 0 and a second unit whose phase offset is π, The phase-shift structure has the first unit and the second unit arranged spatially randomly.

11. The laser device according to any one of claims 2 to 4 and 6, wherein: The laser device has a random phase plate as the phase shift structure.

12. The laser device according to any one of claims 1 to 4 and 6, wherein: The optical resonator is a ring resonator.

13. The laser device according to any one of claims 1 to 4 and 6, wherein: The master oscillator is a discharge-excitation excimer laser device having a narrowband module.

14. The laser device according to any one of claims 1 to 4 and 6, wherein: The master oscillator is an ultraviolet solid-state laser device.

15. The laser device according to any one of claims 1 to 4 and 6, wherein: The unit is in the shape of a polygon.

16. The laser device according to claim 2, 3 or 6, wherein: The length of the unit in the first direction is different from the length in the second direction.

17. A laser device, comprising: a master oscillator, whose output is laser; an amplifier having an optical resonator in which the laser light output by the master oscillator is amplified; as well as a phase shift structure arranged on the optical path closer to the amplifier than a midpoint of the optical path between the master oscillator and the amplifier, The phase shift structure includes a plurality of units having different phase shift amounts of the laser light. Assuming that the wavelength of the laser light is λ and the upper limit of the beam spread angle of the laser light output from the amplifier is θ Amax , the lower limit is θ Amin In the case of The arrangement interval of the units is λ / (1.5·θ Amax ) and λ / θ Amin the following.

18. The laser device according to claim 17, wherein: The arrangement interval of the units is λ / θ Amax Above and λ / θ Amin the following.

19. A method for manufacturing an electronic device, comprising the following steps: Use a laser device to generate laser light which is amplified by an amplifier. The amplified laser light is output to an exposure device, exposing the amplified laser light on a photosensitive substrate in the exposure device to manufacture electronic devices, The laser device has: a master oscillator, whose output is laser; The amplifier has an optical resonator in which the laser light output by the master oscillator is amplified; as well as a phase shift structure arranged on the optical path closer to the amplifier than a midpoint of the optical path between the master oscillator and the amplifier, The phase shift structure includes a plurality of units having different phase shift amounts of the laser light. The arrangement interval of the units is 80 μm or more and 275 μm or less. The laser device has: A rear mirror having a partially reflecting film coated on a first surface and a film having the phase shift structure coated on a second surface opposite to the first surface; as well as Output coupling mirror, The optical resonator is formed by the partially reflective film and the output coupling mirror.

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