CN210835580U - Photomask plate - Google Patents

Abstract

The utility model relates to a photomask plate can improve when using photomask plate to carry out the photoetching, and the figure boundary of rendition is fuzzy, the not accurate condition, improves photoetching technology's production processing yield. The photomask plate has a pattern region, including: a substrate; a phase shift layer formed on the upper surface of the substrate; the first light shielding layer is formed on the upper surface of the phase shift layer, arranged along the edge of the pattern area and has light transmittance smaller than or equal to a preset value; and the second light shielding layer is formed on the upper surface of the first light shielding layer.

Description

Photomask plate

Technical Field

The utility model relates to a photomask board field, concretely relates to photomask board.

Background

In the fabrication of semiconductor devices, photolithography is used to transfer a pattern to a wafer, which is then masked. The photomask plate is made of quartz or glass, and one or more metal materials are deposited on one side surface to prevent light transmission. As the critical dimensions of wafers decrease, and the density of circuits in integrated circuit chips increases, resolution enhancement techniques such as OPC (optical proximity correction), OAI (off-axis illumination), DDL (double dipole lithography), and PSM (Phase Shift Mask) have been developed to improve the depth of focus and thus better transfer the pattern to the wafer.

The PSM uses both the intensity and phase of the light to image, resulting in higher resolution.

In the prior art, when the PSM method is used for photolithography, the structure of the photomask is shown in fig. 1. The basic principle of PSM is to introduce a phase difference of 180 ° (or an odd multiple thereof) in adjacent transmissive areas of the mask pattern, or to supplement a transmittance change (attenuation PSM), to change the interference state between diffracted beams of adjacent patterns. Through destructive interference of light fields of adjacent light transmission areas, the light intensity of a dark area in the light field distribution is reduced, and the light field of a bright area is increased so as to improve the contrast and the resolution, or the phase gradient of adjacent patterns is used for generating a light field direction reversal area and a zero field area so as to improve the pattern gradient, the contrast and the resolution. The light field distribution of the bright area becomes steep, so that the exposure tolerance is also improved.

However, in the prior art, when the PSM is used to transfer the pattern of the photomask, the transferred pattern boundary is always blurred and inaccurate, which greatly affects the production yield in the photolithography process.

SUMMERY OF THE UTILITY MODEL

An object of the utility model is to provide a photomask plate can improve when using photomask plate to carry out the photoetching, and the figure boundary of rendition is fuzzy, the not accurate condition, improves the production processing yield of photoetching technology.

In order to solve the above technical problem, there is provided a photomask having a pattern region, comprising: a substrate; a phase shift layer formed on the upper surface of the substrate; the first light shielding layer is formed on the upper surface of the phase shift layer, arranged along the edge of the pattern area and has light transmittance smaller than or equal to a preset value; and the second light shielding layer is formed on the upper surface of the first light shielding layer.

Optionally, the phase shift layer comprises at least one of a MoSiON layer or a MoSi layer.

Optionally, the first light shielding layer includes at least one of a MoSiON layer having a light transmittance of 0 or a MoSi layer having a light transmittance of 0.

Optionally, the second light shielding layer comprises at least one of a chromium layer or a chromium oxide layer.

Optionally, the projection of the second light shielding layer on the substrate surface is covered by the projection of the first light shielding layer on the substrate surface.

Optionally, an opening is formed in the second light shielding layer, the opening completely exposes the pattern region, and an edge of the opening and an edge of the pattern region have a preset distance, where the preset distance is greater than 0 μm and less than or equal to 600 μm.

Optionally, the substrate comprises a quartz substrate.

Optionally, the light transmittance of the phase shift layer is 6% to 18%, and the thickness of the phase shift layer is in a range of 50 nm to 100 nm.

Optionally, the first light shielding layer has a thickness in a range of 50 to 100 nm.

Optionally, the second light shielding layer has a thickness in the range of 30 to 60 nm.

The utility model discloses a photomask plate has set up the first light shielding layer of one deck between second light shielding layer and phase shift layer, sets up two-layer light shielding layer, can prevent effectively that light from never inciding to phase shift layer in the region that expects, and use the photomask plate among this detailed implementation, even the change of shape takes place at reaction process in the second light shielding layer becomes printing opacity, also can by first light shielding layer carries out sheltering from of light, and like this, when using this photomask plate to carry out the photoetching, the border of rendition figure of rendition to target area is more accurate to can improve the production yield of wafer.

Drawings

Fig. 1 is a schematic structural diagram of a photomask in the prior art.

Fig. 2 is a diagram of a preset effect when photolithography is performed using a photomask plate in the prior art.

Fig. 3 is a diagram showing an actual effect of photolithography using a photomask in the related art.

Fig. 4 a-4 j are schematic diagrams of the photomask plate corresponding to each step of forming the photomask plate according to an embodiment of the present invention.

Fig. 5 a-5 j are schematic diagrams of the photomask plate corresponding to each step of forming the photomask plate according to an embodiment of the present invention.

Fig. 6 is a schematic flow chart illustrating steps of a method for forming a photomask according to an embodiment of the present invention.

Fig. 7 is a top view of a photomask formed in an embodiment of the present invention.

Detailed Description

Research finds that in the photoetching process, when the pattern of the photomask plate is transferred to a target area, the pattern boundary after transfer is always fuzzy and inaccurate because the mask layer used for blocking light of the photomask used in the photoetching process in the prior art is easy to react in the photoetching process and generate ion migration, so that the mask layer is changed from opaque to transparent.

As shown in fig. 1, fig. 1 is a schematic structural diagram of a photomask in the prior art. In the embodiment shown in fig. 1, chromium metal is used as the mask layer 203 of the mask. In the case of photolithography using the photomask shown in fig. 1, an exposure process using 193nm rf immersion lithography is required. Fig. 2 is a partial top view of the photomask shown in fig. 1, in which the boundary of the transfer pattern 201 to be transferred to the target region is expected to be the boundary of the mask layer 203 and to be clearly precise, and the size of the transfer pattern 201 is d1 in the partial top view, however, the effect of the actually obtained transfer pattern 201 is often that the boundary of the transfer pattern 201 is within a fuzzy region 301 and is not precise enough as shown in fig. 3. This is because the chromium ions in the chromium layer as the masking layer 203 migrate during the exposure process, and the chromium layer gradually changes from opaque to transparent as the chromium ions migrate, and it can be seen in fig. 3 that the size of the masking layer with sufficient masking effect changes from d2 to d 3. The light incident from the top of the chrome layer may pass through the fuzzy area 301, so that the boundary of the transfer pattern 201 finally transferred to the target area is fuzzy and inaccurate, and the size of the transfer pattern 201 is changed from d1 to d4, which is greatly different from the preset size, thereby affecting the production yield in the photolithography process.

The following describes a photomask plate according to the present invention in further detail with reference to the accompanying drawings and embodiments.

Please refer to fig. 4 a-4 j and fig. 7, wherein fig. 4 a-4 j are schematic diagrams of the photomask plate corresponding to each step of forming the photomask plate according to an embodiment of the present invention, and fig. 7 is a partial top view of the photomask plate formed according to an embodiment of the present invention.

As shown in fig. 4j, in this embodiment, there is provided a photomask having a pattern region, including: a substrate 101; a phase shift layer 102 formed on the upper surface of the substrate 101, wherein the phase shift layer 102 is used for changing the phase of light incident into the substrate 101; a first light shielding layer 401 formed on the upper surface of the phase shift layer 102, wherein the first light shielding layer 401 is disposed along the edge of the pattern region, and the light transmittance of the first light shielding layer 401 is less than or equal to a preset value; and a second light shielding layer 103 formed on the upper surface of the first light shielding layer 401.

In this embodiment, the photomask plate has one first light shielding layer 401 between the second light shielding layer 103 and the phase shift layer 102, and two light shielding layers, which can effectively prevent light from entering the phase shift layer from unexpected regions, and the first light shielding layer 401 can block light even if the second light shielding layer 103 changes in shape during the reaction process and becomes transparent, so that the boundary of the transfer pattern obtained by transferring the target pattern in the phase shift layer to the target region is more accurate when photolithography is performed using the photomask plate, and the production yield of wafers can be improved.

In practice, three or more light shielding layers may be provided as necessary to prevent external light from entering the phase shift layer from unexpected regions.

In one embodiment, the phase shift layer 102 comprises at least one of a MoSiON layer or a MoSi layer. In practice, the phase shift layer 102 may be formed as desired, for example, the phase shift layer 102 may be formed of silicon nitride, tantalum silicide, tantalum nitride, or other suitable materials. In some embodiments, the phase shift layer 102 is a single layer, and in other embodiments, the phase shift layer 102 comprises multiple layers, such as a combination of molybdenum silicide and silicon oxide, or the like.

In one embodiment, the phase shift layer 102 has a thickness in the range of 50 to 100nm, for example, the phase shift layer 102 may have a thickness of 60 nm.

In one embodiment, the phase shift layer 102 has a light transmittance of 6% to 18%. This is the required transmittance of the PSM. In practice, corresponding adjustments may be made as desired. In one embodiment, the phase shift layer 102 has a light transmittance of 6%.

In a specific embodiment, the light transmittance of the first light shielding layer 401 is lower than a preset value. In some embodiments, the preset value may be set as desired. The light transmittance of the first light shielding layer 401 is limited to prevent the light transmittance of the first light shielding layer 401 from being too high to prevent light from passing through, so that a transfer pattern with unclear boundaries is finally formed after the second light shielding layer 103 transmits light.

In a specific embodiment, the preset value ranges from 0% to 2%, that is, the light transmittance of the first light shielding layer is less than or equal to 2%. In a specific embodiment, the first light shielding layer 401 includes at least one of a MoSiON layer having a light transmittance of 0 or a MoSi layer having a light transmittance of 0. Here, when the MoSiON layer constituting the first light shielding layer 401 is formed, the interatomic density at which MoSiON is formed may be adjusted by a sputtering technique, so that a MoSiON layer having a specific light transmittance may be obtained.

In one embodiment, the light transmittance of the first light shielding layer 401 may be adjusted not only by adjusting the density of the MoSiON layer constituting the first light shielding layer 401, but also by adjusting the thickness of the MoSiON layer constituting the first light shielding layer 401.

In a specific embodiment, the thickness of the first light shielding layer 401 ranges from 50 to 100 nm. In practice, the thickness of the first light shielding layer 401 may be set as needed. For example, the thickness of the first light shielding layer 401 may be 60 nm.

In a specific embodiment, the second light shielding layer 103 comprises at least one of a chromium layer or a chromium oxide layer. In one embodiment, the second light shielding layer 103 is used to prevent light leakage from undesired areas during photolithography using the photomask. In this embodiment, therefore, the second light shielding layer 103 extends along the periphery of the pattern region to prevent light leakage from other patterns at the periphery. In this particular embodiment, the second light shielding layer 103 is opaque to light transmitted through the substrate 101 and the phase shift layer 102.

In other embodiments, the second light shielding layer 103 may be provided with a specific configuration as needed, for example, the second light shielding layer 103 may be provided with at least one of a chromium layer, a nickel layer, an aluminum layer, a ruthenium layer, a tantalum boron nitride layer, and the like.

When the second light shielding layer 103 is formed of a chromium layer, since the chromium layer gradually undergoes an ion reaction and becomes transparent as exposure proceeds in a photolithography process, the second light shielding layer 103 of the photomask plate gradually loses efficacy as the photomask plate is used, and at this time, the first light shielding layer 401 can be used to achieve a light shielding function for an unexpected region. In the specific implementation mode, the service life of the photomask plate is greatly prolonged, the transfer printing pattern transferred to the target area always has a clear and definite boundary, and the transfer printing quality in the photoetching process is improved.

Here, referring to fig. 7, in fig. 7, d3 is the original size of the second light shielding layer 103. As the reaction proceeds, a part of the second light shielding layer 103 becomes transparent, and the light shielding size changes from d3 to d5, but the light shielding region of the first light shielding layer 401 does not change, and the boundary of the transfer pattern 201 is still based on the boundary of the first light shielding layer 401, and in fig. 7, the size of the transfer pattern 201 is still d 1.

In a specific embodiment, the projection of the second light shielding layer 103 on the surface of the substrate 101 is covered by the projection of the first light shielding layer 401 on the surface of the substrate 101. Thus, after the property of the second light shielding layer 103 changes from opaque to transparent, all light rays transmitted through the second light shielding layer 103 can be blocked by the first light shielding layer 401, and the blocking effect of the first light shielding layer 401 is ensured.

In a specific embodiment, the second light shielding layer has an opening formed therein, the opening completely exposes the pattern region, and an edge of the opening has a predetermined distance from an edge of the pattern region, the predetermined distance is greater than 0 μm and less than or equal to 600 μm, that is, a difference between the dimension d2 of the first light shielding layer 401 and the dimension d3 of the second light shielding layer 103 may be 0 to 600 μm. The wider spacing is provided not only to ensure that all light transmitted through the second light shielding layer 103 is blocked by the first light shielding layer 401, but also because when a chromium layer is used as the second light shielding layer 103, the chromium layer may undergo oxidation expansion during the exposure process of photolithography, resulting in an increase in the coverage area of the chromium layer. The larger second light shielding layer is arranged, so that the volume of the chromium layer after oxidation can be effectively prevented from being increased to exceed the shielding range of the first light shielding layer 401.

For example, the distance between the edge of the opening and the edge of the target pattern in the phase shift layer may be 500 μm, i.e., the difference between the dimension d2 of the first light shielding layer 401 and the dimension d3 of the second light shielding layer 103 may be 500 μm, to prevent the chromium layer from increasing in volume after oxidation beyond the shielding range of the first light shielding layer 401.

In one embodiment, the thickness of the second light shielding layer 103 is in a range of 30 to 60nm for better light-proof effect.

In one embodiment, the substrate 101 comprises a quartz substrate 101. In fact, the substrate 101 may be at least one of glass, alumina, fused silica, calcium fluoride, silicon nitride, titanium oxide alloy, sapphire, etc. according to the requirement. In actual use, a suitable material can be used as the substrate as required. In some embodiments, the thickness of the substrate 101 ranges from 0.3 cm to 0.9cm, for example, the thickness of the substrate 101 may be 0.8 cm.

Please refer to fig. 4 a-4 j, fig. 5 a-5 j and fig. 6, wherein fig. 5 a-5 j are schematic diagrams of the photomask plate corresponding to each step of forming the photomask plate according to an embodiment of the present invention, and fig. 6 is a schematic flowchart of the steps of the method for forming the photomask plate according to an embodiment of the present invention.

In this embodiment, the following also provides a method of forming a photomask plate, including the steps of: s51 providing a substrate 101; s52 forming a phase shift layer 102 on the upper surface of the substrate 101; s53, forming a first light shielding layer 103 on the upper surface of the phase shift layer, where the transmittance of the first light shielding layer 103 is less than or equal to a preset value; s54 forming a second light shielding layer 401 on the upper surface of the first light shielding layer 103, until step S54, refer to fig. 4 a; s55 removes the first light shielding layer 103 and the second light shielding layer 401 located in a preset region, which is a pattern region of the photomask plate, where reference can be made to fig. 4 e.

With the method of forming a photomask plate in this embodiment, when light is incident on the photomask plate from above the second light shielding layer 103, the light cannot pass through the second light shielding layer 103 and the first light shielding layer 401. Even if the property of the second light shielding layer 103 is changed along with the photolithography, the first light shielding layer 401 is used as a light shielding guarantee layer, which ensures that the finally obtained transfer pattern has an accurate edge when the photomask plate is used for photolithography, and is not affected by the change of the shape of the second light shielding layer 103, thus the service life of the photomask plate can be prolonged, and the yield of wafer production can be improved.

In one embodiment, the phase shift layer 102 comprises at least one of a MoSiON layer or a MoSi layer. In practice, the phase shift layer 102 may be formed as desired, for example, the phase shift layer 102 may be formed of silicon nitride, tantalum silicide, tantalum nitride, or other suitable materials. In some embodiments, the phase shift layer 102 is a single layer, and in other embodiments, the phase shift layer 102 comprises multiple layers, such as a combination of molybdenum silicide and silicon oxide, or the like.

In one embodiment, the phase shift layer 102 has a thickness in the range of 50 to 100nm, for example, the phase shift layer 102 may have a thickness of 60 nm.

In one embodiment, in forming the phase shift layer 102, the phase shift layer 102 may be formed to the corresponding region by chemical vapor deposition, atomic layer deposition, or physical vapor deposition.

In a specific embodiment, the preset value can be set as required. The reason why the light transmittance of the first light shielding layer 401 is limited to be less than or equal to a preset value is to prevent the light transmittance of the first light shielding layer 401 from being too high to prevent light from passing through, which results in that a transfer pattern with unclear boundaries is finally formed after the second light shielding layer 103 passes through.

In a specific embodiment, the preset value ranges from 0% to 2%, that is, the light transmittance of the first light shielding layer 401 is less than or equal to 2%. In a specific embodiment, the first light shielding layer 401 includes at least one of a MoSiON layer having a light transmittance of 0 or a MoSi layer having a light transmittance of 0. Here, when the MoSiON layer constituting the first light shielding layer 401 is formed, the density of the formed MoSiON may be adjusted so that a MoSiON layer having a specific light transmittance is obtained.

In one embodiment, the light transmittance of the first light shielding layer 401 may be adjusted not only by adjusting the density of the MoSiON layer constituting the first light shielding layer 401, but also by adjusting the thickness of the MoSiON layer constituting the first light shielding layer 401.

In a specific embodiment, the thickness of the first light shielding layer 401 ranges from 50 to 100 nm. In practice, the thickness of the first light shielding layer 401 may be set as needed. For example, the thickness of the first light shielding layer 401 may be 60 nm.

In one embodiment, when the first light shielding layer 401 is formed, the first light shielding layer 401 may also be formed to the corresponding region by a chemical vapor deposition, atomic layer deposition, or physical vapor deposition.

In a specific embodiment, the second light shielding layer 103 comprises at least one of a chromium layer or a chromium oxide layer. In one embodiment, the second light shielding layer 103 may be used to prevent undesired area light leakage during photolithography using the photomask. In this particular embodiment, therefore, the second light shielding layer 103 extends along the periphery of the target pattern in the phase shift layer to prevent light leakage from other patterns at the periphery. In this particular embodiment, the second light shielding layer 103 is opaque to light transmitted through the substrate 101 and the phase shift layer 102.

In other embodiments, the second light shielding layer 103 may be provided with a specific configuration as needed, for example, the second light shielding layer 103 may be provided with at least one of a chromium layer, a nickel layer, an aluminum layer, a ruthenium layer, a tantalum boron nitride layer, and the like.

In one embodiment, the thickness of the second light shielding layer 103 is in a range of 30 to 60nm for better light-proof effect.

In one embodiment, when forming the second light shielding layer 103, the second light shielding layer 103 may also be formed to the corresponding region by chemical vapor deposition, atomic layer deposition, physical vapor deposition, or the like.

When the second light shielding layer 103 is formed of a chromium layer, since the chromium layer gradually undergoes an ion reaction and becomes transparent as exposure proceeds in a photolithography process, the second light shielding layer 103 of the photomask plate gradually loses efficacy as the photomask plate is used, and at this time, the first light shielding layer 401 can be used to achieve a light shielding function for an unexpected region. In the specific implementation mode, the service life of the photomask plate is greatly prolonged, the transfer printing pattern transferred to the target area always has a clear and definite boundary, and the transfer printing quality in the photoetching process is improved.

In one embodiment, when removing the first light shielding layer 401 and the second light shielding layer 103 located in the preset region, the following steps are included: forming a first photoresist layer 402 on the upper surface of the second light shielding layer 103, as shown in fig. 4 b; patterning the first photoresist layer 402 to expose the upper surface of the second light shielding layer 103 in the predetermined region, which can be referred to as fig. 4 c; etching the exposed region of the second light shielding layer 103 in a downward direction perpendicular to the surface of the substrate 101 until the upper surface of the first light shielding layer 401 is exposed; etching the region of the first light shielding layer 401 exposed from the second light shielding layer 103 in a downward direction perpendicular to the surface of the substrate 101 until the upper surface of the phase shift layer 102 is exposed, as shown in fig. 4 d; the remaining first photoresist layer 402 is removed.

In a specific embodiment, when removing the first light shielding layer 401 and the second light shielding layer 103 located in the preset region, the method further includes the following steps: and partially etching the exposed phase shift layer to partially expose the upper surface of the substrate. Reference is made here to fig. 4 j. In one embodiment, the method comprises the following steps when the upper surface of the exposed phase shift layer is partially etched: filling a third photoresist layer 404 between the first light shielding layer 401 and the second light shielding layer 103, wherein the third photoresist layer 404 is filled to the upper surface of the second light shielding layer, as shown in fig. 4 h; patterning the third photoresist layer 404, and the patterned third photoresist layer 404 exposes the upper surface of the portion of the phase shift layer 102 to be etched, which can be referred to as fig. 4 i; the exposed area of the phase shift layer 102 is etched in a downward direction perpendicular to the surface of the substrate 101 until the upper surface of the substrate 101 is exposed, as shown in fig. 4 j.

In one embodiment, the first photoresist layer 402 and the third photoresist layer 404 are patterned by directional dry etching. In etching the first light shielding layer 401, the second light shielding layer 103, and the phase shift layer 102, directional dry etching is also used. In fact, the desired etching mode can be selected as desired.

In a specific embodiment, when removing the first light shielding layer 401 and the second light shielding layer 103 located in the preset region, the method further includes the following steps: an opening is formed on the surface of the second light shielding layer 103, and a preset distance is formed between the edge of the opening and the edge of the preset area, wherein the preset distance is greater than 0 μm and less than or equal to 600 μm until the upper surface of the first light shielding layer 401 is exposed.

In this particular embodiment, the projection of the second light shielding layer 103 on the surface of the substrate 101 is covered by the projection of the first light shielding layer 401 on the surface of the substrate 101. Thus, after the property of the second light shielding layer 103 changes from opaque to transparent, all light rays transmitted through the second light shielding layer 103 can be blocked by the first light shielding layer 401, and the blocking effect of the first light shielding layer 401 is ensured.

In this embodiment, a wider distance is provided between the edge of the opening and the edge of the predetermined area, not only to ensure that all light transmitted through the second light shielding layer 103 can be blocked by the first light shielding layer 401, but also because when a chromium layer is used as the second light shielding layer 103, the chromium layer may be oxidized and expanded during the exposure process of photolithography, resulting in an increase in the coverage area of the chromium layer. The larger second light shielding layer is arranged, so that the volume of the chromium layer after oxidation can be effectively prevented from being increased to exceed the shielding range of the first light shielding layer 401.

In a specific embodiment, the distance between the edge of the opening and the edge of the predetermined area is 500 μm to prevent the volume of the chromium layer from increasing beyond the shielding range of the first light shielding layer 401 after oxidation.

In one embodiment, when forming an opening in the second light shielding layer 103, the method includes the steps of: filling a second photoresist layer 403 between the remaining first light shielding layers 401 and the remaining second light shielding layers 103 until the second photoresist layer 403 covers the upper surface of the second light shielding layers 103, which can be referred to as fig. 4 e; patterning the second photoresist layer 403 to expose a portion of the upper surface of the second light shielding layer 103, where the edge of the pattern formed by the second photoresist layer 403 has a predetermined distance from the edge of the predetermined region, as shown in fig. 4 f; the second light shielding layer 103 exposed out of the second photoresist layer 403 is etched in a downward direction perpendicular to the surface of the substrate 101 until the upper surface of the first light shielding layer 401 is exposed, as shown in fig. 4 g.

In another embodiment, when removing the first light shielding layer 401 and the second light shielding layer 103 located in the preset region, the method includes the steps of: forming a first photoresist layer 402 on the surface of the second light shielding layer 103, as shown in fig. 4 b; patterning the first photoresist layer 402, wherein the patterned first photoresist layer has a first region disposed along the edge of the predetermined region and a second region for protecting the phase shift layer 102, please refer to fig. 5 a; transferring the pattern of the first photoresist layer 402 to the second light shielding layer 103, the first light shielding layer 401 and the phase shift layer 102 in sequence, as shown in fig. 5 b; removing the first photoresist layer as shown in FIG. 5 c; a third photoresist layer 404 is filled between the second light shielding layer 103, the first light shielding layer 401 and the phase shift layer 102, please refer to fig. 5g, note that the second light shielding layer 103 has been partially removed in fig. 5 g; patterning the third photoresist layer 404, leaving only the portion of the third photoresist layer 404 disposed in the first region after patterning, exposing and displacing the upper surface of the first light shielding layer 401 in the second region, as shown in fig. 5 h; transferring the patterned pattern of the third photoresist layer 404 to the first light shielding layer 401, as shown in fig. 5 i; the remaining third photoresist layer 404 is removed, as shown in FIG. 5 j.

In this embodiment, the third photoresist layer 404 is disposed to remove the unwanted first light-shielding layer on the upper surface of the phase shift layer 102.

In this embodiment, after removing the first photoresist layer and before forming the third photoresist layer 404, an opening is formed on the surface of the second light shielding layer by: filling a second photoresist layer 403 between the second light shielding layer 103, the first light shielding layer 401 and the phase shift layer 102, wherein the second photoresist layer 403 is filled to the upper surface of the second light shielding layer 103, as shown in fig. 5 d; patterning the second photoresist layer 403 to expose a portion of the upper surface of the second light shielding layer 103, where an edge of a pattern formed by the second photoresist layer 403 has a predetermined distance from an edge of a predetermined region, as shown in fig. 5 e; the pattern on the second photoresist layer 403 is transferred to the second light shielding layer 103, as shown in fig. 5 f.

In this embodiment, the remaining second photoresist layer 403 is removed before the third photoresist layer 404 is formed, but in other embodiments, the remaining second photoresist layer 403 may not be removed before the third photoresist layer 404 is formed.

In this embodiment, before forming the first photoresist layer 402, the second photoresist layer 403 and the third photoresist layer 404, an Anti-reflective coating (BARC) such as a standing-wave Anti-reflective coating (standing-recess) coating is formed on the surface of the target region to prevent the first photoresist layer 402, the second photoresist layer 403 and the third photoresist layer 404 from standing-wave effect and recess (notching) effect, thereby affecting the reliability of pattern transfer in the photolithography process.

In forming the first photoresist layer 402, since the first photoresist layer 402 is formed on the upper surface of the second light shielding layer 103, the first photoresist layer 402 may be formed on the upper surface of the second light shielding layer 103 by spin-coating a photoresist coating. In forming the second photoresist layer 403 and the third photoresist layer 404, since the second photoresist layer 403 and the third photoresist layer 404 have a groove structure to be filled, chemical vapor deposition, atomic layer deposition, physical vapor deposition, or the like is required to form the second photoresist layer 403 or the third photoresist layer 404 in corresponding regions.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, a plurality of modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.

Claims (10)

1. A photomask having a pattern region, comprising:

a substrate;

a phase shift layer formed on the upper surface of the substrate;

the first light shielding layer is formed on the upper surface of the phase shift layer, arranged along the edge of the pattern area and has light transmittance smaller than or equal to a preset value;

and the second light shielding layer is formed on the upper surface of the first light shielding layer.

2. A photomask of claim 1 wherein the phase shift layer comprises at least one of a MoSiON layer or a MoSi layer.

3. A photomask according to claim 1, wherein the first light shielding layer comprises at least one of a MoSiON layer having a light transmittance of 0 or a MoSi layer having a light transmittance of 0.

4. A photomask according to claim 1, wherein the second light shielding layer comprises at least one of a chromium layer or a chromium oxide layer.

5. A photomask according to claim 1, wherein the projection of the second light shielding layer on the substrate surface is covered by the projection of the first light shielding layer on the substrate surface.

6. A photomask according to claim 1, wherein the second light shielding layer has an opening formed therein, the opening completely exposes the pattern region, and an edge of the opening is a predetermined distance from an edge of the pattern region, the predetermined distance being greater than 0 μm and 600 μm or less.

7. A photomask according to claim 1, wherein the substrate comprises a quartz substrate.

8. A photomask according to claim 1, wherein the phase shift layer has a light transmittance of 6% to 18%, and the phase shift layer has a thickness in the range of 50 to 100 nm.

9. A photomask according to claim 1, wherein the thickness of the first light shielding layer is in the range of 50 to 100 nm.

10. A photomask according to claim 1, wherein the thickness of the second light shielding layer is in the range of 30 to 60 nm.

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