Mask and laser processing method

Abstract

The present invention provides a mask which is used for laser processing, the mask comprising: a synthetic quartz substrate which has a first surface and a second surface that is on the reverse side from the first surface; and a patterned light-shielding film. The light-shielding film has: a metal element-containing film that is formed on the first surface of the synthetic quartz substrate; and a metal film that is formed on the metal element-containing film. The metal element-containing film and the metal film have mutually different compositions. When the synthetic quartz substrate is irradiated with a laser from the second surface side, the reflectance at the metal element-containing film is 40% to 80%. This configuration makes it possible to provide a mask which is capable of exhibiting excellent durability in laser processing.

Description

Mask and laser processing method

[0001] The present invention relates to a mask and a laser processing method.

[0002] In laser processing, it is common practice to use a laser processing mask to irradiate only the desired area of ​​the workpiece with a laser (for example, Patent Documents 1-3).

[0003] While masks are also used in the photolithography process, the required performance differs between masks used for laser processing and those used in photolithography. Durability is a prime example of such a difference.

[0004] JP-A-9-225669 JP-A-62-257166 JP-A-62-052551

[0005] Mitani Micronics website, "A condensation of half a century of fine-line technology," [online], Mitani Micronics, [Accessed February 28, 2025], Internet <https: / / www.mitani-micro.co.jp / mask / photo.html#05>

[0006] The peak power intensity of lasers used in photolithography processes is generally 1 kW / cm². ２ It is approximately that much. On the other hand, the peak power intensity of one pulse of a laser used in laser processing is 100 MW / cm². ２ This can also occur. In other words, in laser processing, the peak power intensity of the laser is much higher compared to the lithography process.

[0007] Therefore, masks for laser processing need to be durable enough to withstand the peak power density of a single pulse. This is because the shielding film used in masks, such as Cr, absorbs the laser and then converts the light energy into thermal energy. This entire process is completed in a very short time. The overall energy relaxation time for metals is typically 1 × 10⁻⁶. －１３ It takes seconds. Furthermore, the transmission depth of light into the metal material is extremely shallow, on the order of 10 nm.

[0008] Generally, a Cr film thickness of around 100 nm is used, as in Non-Patent Document 1, but with a film thickness of this size, the load is 3.4 MW / cm². ２ (100 mJ / cm ２ Damage can occur if the mask is less than 200-300 nm thick. To improve durability, laser processing can be performed using a mask with a light-shielding chromium film of 200-300 nm thickness. For example, to make a chromium mask, first a thin chromium film is deposited onto a base material using a sputtering device. Next, a photosensitive resist is applied, exposed, and developed, and then the chromium film is etched with an etching solution. Finally, the resist film is removed, and the mask is cleaned, measured, inspected, and finished cleaned to obtain a chromium mask with the desired pattern. While such a mask can improve durability, the development of masks with even greater durability is desired.

[0009] This invention was made to solve the above problems and aims to provide a laser processing mask that can exhibit high durability in laser processing, and a laser processing method using this mask.

[0010] To solve the above problems, the present invention provides a mask for use in laser processing, comprising a synthetic quartz substrate having a first surface and a second surface opposite to the first surface, and a patterned light-shielding film, wherein the light-shielding film comprises a metal element-containing film formed on the first surface of the synthetic quartz substrate and a metal film formed on the metal element-containing film, the metal element-containing film and the metal film having different compositions, and the reflectivity of the metal element-containing film when a laser is irradiated from the second surface side of the synthetic quartz substrate is 40 to 80%.

[0011] In the mask of the present invention, the light-shielding film has a metal element-containing film and a metal film with different compositions, and when a laser is irradiated from the side opposite to the light-shielding film of the synthetic quartz substrate (second side), the reflectivity of the metal element-containing film is 40-80%. This allows the absorption rate of laser energy by the mask to be appropriately suppressed, thereby enabling excellent durability in laser processing. Furthermore, when the mask of the present invention is used in a laser processing apparatus, the reflectivity of the metal element-containing film is 40-80% when a laser is irradiated from the side opposite to the light-shielding film of the synthetic quartz substrate (second side), which suppresses the generation of stray light within the laser processing apparatus, thereby enabling high-precision laser processing.

[0012] For example, the metal film may contain chromium or aluminum.

[0013] The presence of a metal film can increase the heat capacity. While the material is not particularly limited, chromium or aluminum can be used.

[0014] For example, the thickness of the metal film may be 100 to 400 nm.

[0015] Furthermore, the thickness of the light-shielding film may be, for example, 120 to 450 nm.

[0016] The thickness of the metal film and the overall thickness of the light-shielding film are not particularly limited.

[0017] The aforementioned metal element-containing film preferably contains at least molybdenum and silicon.

[0018] By including a light-shielding film containing metal elements such as molybdenum and silicon, durability can be reliably improved.

[0019] Another film may be further present between the metal element-containing film and the metal film.

[0020] Depending on the required performance, other films can be added as needed.

[0021] In this case, the other film may also have a multilayer structure.

[0022] The other layers mentioned above may be single layers or layers having a multilayer structure.

[0023] Preferably, the light-shielding film has a heat capacity such that the temperature rise of the entire light-shielding film due to absorption of the irradiated laser is below the melting point of the constituent material of the light-shielding film.

[0024] A mask containing a light-shielding film with such heat capacity can exhibit superior durability.

[0025] Furthermore, the present invention provides a laser processing method for a workpiece, wherein the mask of the present invention is positioned so that the metal film is in contact with the workpiece, and the workpiece is subjected to laser processing using the mask.

[0026] According to the laser processing method of the present invention, since the mask of the present invention is used, the generation of stray light within the laser processing apparatus can be suppressed, thereby enabling high-precision laser processing. Furthermore, since the mask of the present invention exhibits excellent durability, laser processing can be carried out economically and continuously.

[0027] For example, laser ablation can be performed as the laser processing.

[0028] While the type of laser processing is not particularly limited, the mask of the present invention can exhibit high durability even when laser ablation is performed using a laser irradiated at a high peak power density.

[0029] As described above, the mask of the present invention can demonstrate excellent durability in laser processing. Furthermore, by using the mask of the present invention in a laser processing apparatus, high-precision laser processing can be performed.

[0030] Furthermore, the laser processing method of the present invention makes it possible to perform high-precision laser processing economically and continuously.

[0031] This is a partial schematic cross-sectional view showing an example of the mask of the present invention. This is a partial schematic cross-sectional view showing another example of the mask of the present invention. This is a partial schematic cross-sectional view showing a light-shielding film of yet another example of the mask of the present invention. This is a schematic cross-sectional view showing an example of the laser processing method of the present invention.

[0032] As mentioned above, there was a need to develop a laser processing mask that could exhibit high durability in laser processing.

[0033] As a result of diligent research into the above-mentioned problems, the inventors of the present invention have found that a mask having a light-shielding film on a synthetic quartz substrate comprising a metal element-containing film and a metal film with different compositions, wherein the reflectivity of the metal element-containing film is 40-80% when a laser is irradiated from the side of the synthetic quartz substrate opposite to the light-shielding film (second side), can appropriately suppress the absorption rate of laser energy, thereby demonstrating excellent durability in laser processing, and thus completed the present invention.

[0034] In other words, the present invention relates to a mask used for laser processing, comprising a synthetic quartz substrate having a first surface and a second surface opposite to the first surface, and a patterned light-shielding film, wherein the light-shielding film comprises a metal element-containing film formed on the first surface of the synthetic quartz substrate and a metal film formed on the metal element-containing film, the metal element-containing film and the metal film having different compositions, and the reflectivity of the metal element-containing film when a laser is irradiated from the second surface side of the synthetic quartz substrate is 40 to 80%.

[0035] The present invention will be described in detail below with reference to the drawings, but the present invention is not limited to these descriptions.

[0036] [Mask] The mask of the present invention is a mask used for laser processing and comprises a synthetic quartz substrate having a first surface and a second surface opposite to the first surface, and a patterned light-shielding film, wherein the light-shielding film comprises a metal element-containing film formed on the first surface of the synthetic quartz substrate and a metal film formed on the metal element-containing film, the metal element-containing film and the metal film have different compositions, and the reflectance of the metal element-containing film is 40 to 80% when a laser is irradiated from the second surface side of the synthetic quartz substrate.

[0037] Figure 1 shows a schematic partial cross-sectional view of an example of the mask of the present invention. However, the thickness of each film shown in the figure may differ from the actual thickness.

[0038] The mask 10 shown in Fig. 1 is a mask used for laser processing. In the present invention, the type of laser processing is not particularly limited, and for example, laser ablation can be mentioned. Further, the type of laser can be appropriately selected according to the laser processing to be performed. Examples of lasers include excimer lasers (wavelengths 193 nm, 248 nm, 308 nm, 351 nm), Nd*YAG, Nd:YVO ４ , Nd:YLF, Yb:YAG laser 4th harmonic (wavelength 258 to 266 nm), Nd*YAG, Nd:YVO ４ , Nd:YLF, Yb:YAG laser 3rd harmonic (wavelength 343 to 355 nm), and the like.

[0039] The mask 10 includes a synthetic quartz substrate 1. The synthetic quartz substrate 1 has a first surface 11 and a second surface 12 opposite to the first surface 11.

[0040] The planar shape of the synthetic quartz substrate 1 can be appropriately selected according to the shape required for the mask 10. Further, the thickness of the synthetic quartz substrate 1, that is, the distance between the first surface 11 and the second surface 12, is not particularly limited, and can be, for example, 500 µm or more and 20000 µm or less.

[0041] The mask 10 has a patterned light-shielding film 2 on the first surface 11 of the synthetic quartz substrate 1. The light-shielding film 2 includes a metal element-containing film 21 formed on the first surface 11 of the synthetic quartz substrate 1, and a metal film 22 formed on the metal element-containing film 21.

[0042] The metal element-containing film 21 may be in contact with the first surface 11 of the synthetic quartz substrate 1 as shown in Fig. 1, or an additional film may be interposed between the synthetic quartz substrate 1 and the metal element-containing film 21.

[0043] Further, as shown in Fig. 2 for example, the light-shielding film 2 may further include another film 23 between the metal element-containing film 21 and the metal film 22.

[0044] In the light-shielding film 2, the metal element-containing film 21 and the metal film 22 have different compositions from each other. Further, when laser is irradiated from the second surface 12 side of the synthetic quartz substrate 1, the reflectance at the metal element-containing film 21 is 40 to 80%.

[0045] With the above configuration, the mask 10 according to the present invention can appropriately suppress the absorptivity of laser energy by the mask, thereby exhibiting excellent durability in laser processing. Furthermore, by using the mask 10 of the present invention in a laser processing apparatus, the generation of stray light inside the laser processing apparatus can be suppressed, which enables high-precision laser processing.

[0046] On the other hand, when the reflectance of the metal element-containing film 21 is less than 40% in the case where laser is irradiated from the second surface 12 side of the synthetic quartz substrate 1, the absorptivity of laser energy by the mask cannot be appropriately suppressed. Therefore, during laser processing, particularly during laser ablation with a laser having high peak power intensity per pulse, the temperatures of the metal element-containing film 21 and the metal film 22 increase, and there is a risk that the temperature of either the metal element-containing film 21 or the metal film 22 reaches its melting point. In general, the reflectance of the metal element-containing film 21 decreases as the temperature increases. For nanosecond pulsed lasers such as excimer lasers, for example, 50 pulses of irradiation at 300 Hz may be repeatedly applied at 1-second intervals. Since the next laser pulse is irradiated before the heat generated by the absorption of the laser by the metal element-containing film 21 sufficiently diffuses into the metal element-containing film 21, the metal film 22, and a part of the quartz substrate 1, the temperatures of the metal element-containing film 21 and the metal film 22 gradually increase, and the reflectance also decreases accordingly. If the reflectance of the mask when irradiated with one laser pulse at normal temperature is less than 40%, the practical reflectance will become even lower. In addition, masks are generally used in the atmosphere in ablation processing apparatuses. In order to prevent the metal element-containing film 21 and the metal film 22 from reacting with atmospheric components and changing at high temperatures, MgF including the opening portion ２ or SiO ２ it is effective to provide a protective film of

[0047] Furthermore, when the reflectance of the metal element-containing film 21 exceeds 80% in the case where laser is irradiated from the second surface 12 side of the synthetic quartz substrate 1, stray light is generated in the laser processing apparatus, which makes it difficult to perform high-precision laser processing.

[0048] Furthermore, with a single-composition light-shielding film, if the reflectivity is kept within the range of 40-80%, it cannot adequately function as a light-shielding film. On the other hand, with a single-composition light-shielding film, if the reflectivity is suppressed to fulfill its function as a light-shielding film, it becomes impossible to adequately suppress the absorption rate of laser energy by the mask. For example, if the metal element-containing film 21 is changed to an aluminum film (reflectivity 80%), the film thickness needs to be approximately 8.2 nm to 20.5 nm to obtain a reflectivity of 40-80% for a KrF excimer laser (wavelength 248 nm). At this film thickness, the temperature of the film exceeds its melting point due to laser irradiation. Also, the reflected laser is reflected at the interface between the quartz substrate and the air, and the energy density of the laser that passes through the aperture becomes strong enough to affect high-precision processing. On the other hand, if it is changed to a chromium film with a reflectivity of less than 40%, the film will be damaged.

[0049] The components of the light-shielding film 2 will be explained in more detail below.

[0050] [Metal element-containing film 21] The metal element-containing film 21 may be a single layer or a multilayer film.

[0051] The metal element-containing film 21 preferably contains at least molybdenum and silicon. By including molybdenum Mo and / or silicon Si, durability can be reliably improved. For example, the metal element-containing film 21 may contain a plurality of MoSi layers. Alternatively, the metal element-containing film 21 may have a Si matrix phase and a Mo phase dispersed in the matrix.

[0052] The thickness of the metal element-containing film 21 is not particularly limited, but can be, for example, 20 to 50 nm.

[0053] [Metal film] The material of the metal film 22 is not particularly limited, but it may include, for example, chromium or aluminum. That is, the metal film 22 may be, for example, a chromium film or an aluminum film. By using a chromium film or an aluminum film as the metal film 22, the heat capacity of the mask 10 can be increased.

[0054] Chromium is used as a light-shielding film for exposure, but it has the problem of degrading during laser ablation. Aluminum, on the other hand, is a metal with a low melting point and a relatively high specific heat. Therefore, when aluminum films are directly irradiated with the laser used in laser ablation, they are prone to degradation due to the high peak power intensity of the laser. However, in this invention, when the laser is irradiated from the side opposite to the light-shielding film of the synthetic quartz substrate, the reflectivity of the metal element-containing film is 40-80%, which suppresses damage during laser ablation even if the metal film 22 is a chromium film or an aluminum film.

[0055] The metal film 22 is not limited, but preferably serves the functions of light shielding and heat sink in the mask 10.

[0056] The thickness of the metal film 22 is not particularly limited, but is preferably, for example, 100 to 400 nm. If the metal film 22 has a thickness within this range, the metal film 22 can ensure sufficient heat capacity, which prevents the temperature of the mask 10 from becoming too high during laser processing.

[0057] [Other membranes] The other membranes 23 may be single-layered as shown in Figure 2, or they may have a multilayer structure as shown in Figure 3. In Figure 3, a two-layer structure of a first layer 24 and a second layer 25 is shown, but a multilayer structure consisting of more than two layers is also possible.

[0058] Other films 23 are optionally provided to impart further performance to the mask 10. For example, SiO2 can be added to improve light resistance. ２ Dielectric films such as layers can be included as other films 23. Alternatively, a hafnium oxide layer with a high refractive index can be included to adjust the refractive index.

[0059] In this invention, the other film 23 is any material. Conventionally, it has been proposed to form multiple dielectric layers on the mask to improve light resistance, but this had the disadvantage of high manufacturing costs. On the other hand, in this invention, the light-shielding film has a metal element-containing film and a metal film with different compositions, and the reflectivity of the metal element-containing film is 40-80% when a laser is irradiated from the side opposite to the light-shielding film of the synthetic silica substrate. As a result, the absorption rate of laser energy by the mask can be appropriately suppressed, and the dielectric layer is used only for the purpose of further improving light resistance. Therefore, manufacturing costs can be reduced compared to when many dielectric layers are formed.

[0060] The thickness of the other film 23 is not particularly limited, but can be, for example, 10 to 100 nm.

[0061] The overall thickness of the light-shielding film 2 having the configuration described above is not particularly limited, but can be, for example, 120 to 450 nm.

[0062] Furthermore, it is preferable that the light-shielding film 2 has a heat capacity such that the temperature rise of the entire light-shielding film 2 due to absorption of the irradiated laser is below the melting point of the constituent material of the light-shielding film 2.

[0063] A mask 10 having such a light-shielding film 2 can reliably demonstrate higher durability.

[0064] The total heat capacity of the light-shielding film 2 can be, for example, 0.57 to 0.72 J / K.

[0065] Furthermore, the present invention provides a laser processing method for a workpiece, wherein the mask of the present invention is positioned so that the metal film is in contact with the workpiece, and the workpiece is subjected to laser processing using the mask.

[0066] According to the laser processing method of the present invention, since the mask of the present invention is used, the generation of stray light within the laser processing apparatus can be suppressed, thereby enabling high-precision laser processing. Furthermore, since the mask of the present invention exhibits excellent durability, laser processing can be carried out economically and continuously.

[0067] For example, laser ablation can be performed as the laser processing.

[0068] While the type of laser processing is not particularly limited, the mask of the present invention can exhibit high durability even when laser ablation is performed using a laser irradiated at a high peak power density.

[0069] The pattern provided on the light-shielding film 2 corresponds to the pattern to be formed on the workpiece and is not particularly limited.

[0070] [Laser Processing Method] The laser processing method of the present invention is a laser processing method for a workpiece, wherein the mask of the present invention is placed so that the metal film is in contact with the workpiece, and the workpiece is subjected to laser processing using the mask.

[0071] For example, as shown in Figure 4, the mask 10 of the present invention is positioned so that the metal film of the light-shielding film 2 (not shown in Figure 4) is in contact with the workpiece 20, and the workpiece 20 is laser-processed using this mask 10.

[0072] According to the laser processing method of the present invention, since the mask of the present invention is used, the generation of stray light within the laser processing apparatus can be suppressed, thereby enabling high-precision laser processing. Furthermore, since the mask of the present invention exhibits excellent durability, laser processing can be carried out economically and continuously.

[0073] In the laser processing method of the present invention, the type of laser processing is not particularly limited, but even when laser ablation is performed using a laser irradiated at a high peak power density, the mask of the present invention can exhibit high durability.

[0074] This specification includes the following embodiments: [1] A mask for use in laser processing, comprising: a synthetic quartz substrate having a first surface and a second surface opposite to the first surface; and a patterned light-shielding film, wherein the light-shielding film comprises a metal element-containing film formed on the first surface of the synthetic quartz substrate and a metal film formed on the metal element-containing film, the metal element-containing film and the metal film having different compositions, and the reflectivity of the metal element-containing film when a laser is irradiated from the second surface side of the synthetic quartz substrate is 40 to 80%. [2] The mask according to [1], wherein the metal film comprises chromium or aluminum. [3] The mask according to [1] or [2], wherein the thickness of the metal film is 100 to 400 nm. [4] The mask according to any one of [1] to [3], wherein the thickness of the light-shielding film is 120 to 450 nm. [5] The mask according to any one of [1] to [4], wherein the metal element-containing film comprises at least molybdenum and silicon. [6] The mask according to any one of [1] to [5], further comprising another film between the metal element-containing film and the metal film. [7] The mask according to [6], wherein the other film has a multilayer structure. [8] The mask according to any one of [1] to [7], wherein the light-shielding film has a heat capacity such that the temperature rise of the entire light-shielding film due to absorption of the irradiated laser is less than the melting point of the constituent material of the light-shielding film. [9] A laser processing method for a workpiece, comprising: arranging the mask according to any one of [1] to [8] such that the metal film is in contact with the workpiece; and performing laser processing on the workpiece using the mask.

[10] The laser processing method according to [9], wherein laser ablation is performed as the laser processing.

[0075] It should be noted that the present invention is not limited to the embodiments described above. The embodiments described above are illustrative, and any configuration that is substantially identical to the technical idea described in the claims of the present invention and achieves similar effects is included within the technical scope of the present invention.

Claims

1. A mask for use in laser processing, comprising a synthetic quartz substrate having a first surface and a second surface opposite to the first surface, and a patterned light-shielding film, wherein the light-shielding film comprises a metal element-containing film formed on the first surface of the synthetic quartz substrate and a metal film formed on the metal element-containing film, the metal element-containing film and the metal film having different compositions, and the reflectivity of the metal element-containing film when a laser is irradiated from the second surface side of the synthetic quartz substrate is 40 to 80%.

2. The mask according to claim 1, wherein the metal film comprises chromium or aluminum.

3. The mask according to claim 1, wherein the thickness of the metal film is 100 to 400 nm.

4. The mask according to claim 1, wherein the thickness of the light-shielding film is 120 to 450 nm.

5. The mask according to claim 1, wherein the metal element-containing film comprises at least molybdenum and silicon.

6. The mask according to claim 1, further comprising another film between the metal element-containing film and the metal film.

7. The mask according to claim 6, wherein the other film has a multilayer structure.

8. The mask according to claim 1, wherein the light-shielding film has a heat capacity such that the temperature rise of the entire light-shielding film due to the absorption of the irradiated laser is less than the melting point of the constituent material of the light-shielding film.

9. A laser processing method for a workpiece, comprising: arranging a mask according to any one of claims 1 to 8 such that the metal film is in contact with the workpiece; and performing laser processing on the workpiece using the mask.

10. The laser processing method according to claim 9, wherein the laser processing is performed by laser ablation.

Images