Phase shift photomask plate and manufacturing method thereof

Abstract

The invention relates to a phase shift photomask plate and a manufacturing method thereof. The mask plate comprises: a substrate; a phase shift layer, wherein the phase shift layer is formed on the substrate; the phase shift layer comprises a phase shift layer first part and a phase shift layer second part; the thickness of the first part of the phase shift layer is greater than that of the second part of the phase shift layer; the phase angle of the first part of the phase shift layer is 180 degrees under the condition of a KrF light source. According to the phase shift photomask plate provided by the invention, the KrF photomask achieves the same phase contrast effect of 180 degrees with an ArF photomask under the wavelength of 193m by accurately controlling the thickness of the phase shift layer, and the KrF photomask is used for replacing the ArF photomask, so that the production cost of photomask suppliers is reduced under the condition of not influencing the use performance.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor manufacturing, and in particular to a phase-shift photomask and a manufacturing method thereof. Background Art

[0002] In the wafer production process, the photomask acts as a graphic master, carrying the design graphics. After the mask goes through the process, the designed chip circuit diagram is engraved on the substrate, which is then used by the wafer factory photolithography machine to transfer it to the photoresist on the wafer surface in a 4:1 ratio through exposure and projection, and then transferred to the wafer of the downstream industry through development and etching processes. As the benchmark and blueprint for photolithography copying graphics, the mask is the key to connecting industrial design and process production.

[0003] Phase Shift Mask (Phase Shift Mask) selectively adds a transparent phase shift layer (Phase Shift Layer) in the transparent area on the pattern of the traditional mask, which can reverse the phase of the light beam by 180°. Using this mask for exposure process can greatly increase the exposure resolution capability. The basic principle of PSM is mainly to introduce a phase difference of 180° (or its odd multiple) in the adjacent transparent areas of the mask pattern, or to change the transmittance to change the interference state between the diffracted light beams of adjacent patterns. Through the destructive interference of the light field of adjacent transparent areas, the light intensity of the dark area in the light field distribution is reduced and the light field of the bright area is increased to improve the contrast and resolution, or the phase gradient of the adjacent pattern is used to produce a light field direction reversal and a zero field area to improve the steepness, contrast and resolution of the pattern. Since the light field distribution in the bright area becomes steeper, the exposure tolerance is also improved.

[0004] There are two types of photolithography machines commonly used in wafer factories: 248nm wavelength and 193nm wavelength. The corresponding phase-shift photomasks are KrF and ArF, respectively, so that the KrF photomask at 248nm wavelength and the ArF photomask at 193nm wavelength can achieve a 180° phase reversal effect. The raw material substrates used by the KrF photomask and the ArF photomask are KrF substrates and ArF substrates respectively. The materials of each layer of the two substrates are the same, but there are differences in thickness.

[0005] The cross-sectional diagram of the formation process of KrF photomask and ArF photomask is as follows: Figure 1As shown. The phase-shift photomask substrate includes quartz glass 101, phase-shift layer 102, chrome layer 103 and photoresist 104. Then, the phase-shift photomask substrate is exposed and developed, so that the photoresist in the exposed area is dissolved by the developer, so that the chrome layer below is exposed to obtain a patterned photoresist; the chrome layer 103 is etched for the first time to remove the photoresist, and a mask plate including quartz glass 101, phase-shift layer 102 and chrome pattern layer is obtained; the phase-shift layer in the area without chrome coverage is etched to form a phase-shift layer pattern layer; the chrome layer 103 is etched for the second time to obtain the final phase-shift photomask. The phase-shift layer is generally molybdenum silicide.

[0006] After the photomask is produced, the phase angle will be confirmed to meet the specifications through the phase measurement machines MPM248 and MPM193 (MPM: Mask Phase Measurement). The specifications are both 180±3°, and the wavelength of the measurement machine is the same as that of the wafer factory's photolithography machine. After the phase is measured to meet the specifications at the photomask factory, it will be shipped to the wafer factory for use in both photolithography machines.

[0007] However, the price of ArF substrate is about 6 times that of KrF substrate. If the 193nm wavelength lithography machine can only use its existing ArF photomask, the photomask supplier can only use ArF substrate. For the photomask supplier, the substrate cost accounts for 20% of the total cost of photomask production. The high cost of ArF substrate directly affects the production cost of photomask, thereby reducing the profit of photomask suppliers. Summary of the invention

[0008] In view of some or all of the problems in the prior art, the present invention provides a phase-shift photomask, which comprises:

[0009] substrate;

[0010] A phase shift layer is formed on the substrate; the phase shift layer comprises a first phase shift layer portion and a second phase shift layer portion; the thickness of the first phase shift layer portion is greater than the thickness of the second phase shift layer portion; and the phase angle of the first phase shift layer portion is 180° under a KrF light source condition.

[0011] Furthermore, the material of the phase-shift layer includes at least one of molybdenum oxynitride and molybdenum silicide.

[0012] Furthermore, the thickness of the first part of the phase-shift layer satisfies the following formula:

[0013]

[0014] Wherein, P1 represents the phase angle of 180°, Tpsl1 represents the thickness of the first part of the phase shift layer, npsl1 represents the refractive index of the phase shift layer under the KrF light source condition, nair represents the refractive index of air, λ1 represents the wavelength of the KrF light source, and * represents multiplication;

[0015] The thickness Tpsl2 of the second part of the phase shift layer satisfies the following formula:

[0016] Tpsl2=Tpsl1-Tetch

[0017] Among them, Tetch satisfies the following formula:

[0018]

[0019] Wherein, Petch represents a phase angle of 180°, Tetch represents the thickness difference between the first part of the phase shift layer and the second part of the phase shift layer, npsl2 represents the refractive index of the phase shift layer under ArF light source conditions, nair represents the refractive index of air, λ2 represents the wavelength of the ArF light source, and * represents multiplication.

[0020] Further, the thickness of the first part of the phase-shift layer is in a range of 50 nm to 200 nm; and / or

[0021] The thickness of the second portion of the phase-shift layer is in a range of 10 nm to 50 nm.

[0022] Further, the thickness of the first part of the phase-shift layer is 95.38 nm; and / or

[0023] The thickness of the second portion of the phase-shift layer is in the range of 22.28 nm.

[0024] The present invention also provides a method for manufacturing a phase-shift photomask, the method comprising the following steps:

[0025] Providing a photomask base, the photomask base comprising a substrate, a phase shift layer, a chrome layer and a photoresist;

[0026] Photolithography and development of photomask substrate to form patterned photoresist;

[0027] etching the chromium layer to form a patterned chromium layer;

[0028] removing patterned photoresist;

[0029] etching the phase-shift layer;

[0030] The patterned chromium layer is etched to form a phase-shift photomask.

[0031] Furthermore, the substrate includes a quartz substrate.

[0032] Furthermore, the material of the phase-shift layer includes at least one of molybdenum oxynitride and molybdenum silicide.

[0033] Furthermore, the phase-shift photomask comprises a first phase-shift layer portion and a second phase-shift layer portion; the thickness of the first phase-shift layer portion is greater than the thickness of the second phase-shift layer portion.

[0034] Furthermore, the thickness of the first part of the phase-shift layer satisfies the following formula:

[0035]

[0036] Wherein, P1 represents the phase angle of 180°, Tpsl1 represents the thickness of the first part of the phase shift layer, npsl1 represents the refractive index of the phase shift layer under the KrF light source condition, nair represents the refractive index of air, λ1 represents the wavelength of the KrF light source, and * represents multiplication;

[0037] The thickness Tpsl2 of the second part of the phase shift layer satisfies the following formula:

[0038] Tpsl2=Tpsl1-Tetch

[0039] Among them, Tetch satisfies the following formula:

[0040]

[0041] Wherein, Petch represents a phase angle of 180°, Tetch represents the thickness difference between the first part of the phase shift layer and the second part of the phase shift layer, npsl2 represents the refractive index of the phase shift layer under ArF light source conditions, nair represents the refractive index of air, λ2 represents the wavelength of the ArF light source, and * represents multiplication.

[0042] The technical solution provided by the present invention has the following beneficial effects:

[0043] The phase-shift photomask provided by the present invention can achieve the same phase contrast of 180 degrees as the ArF photomask at a wavelength of 193m by precisely controlling the thickness of the phase-shift layer. The KrF photomask can replace the ArF photomask without affecting the performance, thereby reducing the production cost of the photomask supplier. The price of the KrF substrate is about one-sixth of that of the ArF substrate. If the KrF photomask replaces the ArF photomask, the change of the substrate can reduce the material cost by 83% and increase the gross profit by 25-30%. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] To further illustrate the above and other advantages and features of various embodiments of the present invention, a more specific description of various embodiments of the present invention will be presented with reference to the accompanying drawings. It will be understood that these drawings only depict typical embodiments of the present invention and are therefore not to be considered as limiting the scope thereof. In the accompanying drawings, for clarity, identical or corresponding parts will be represented by identical or similar reference numerals.

[0045] Figure 1 A cross-sectional schematic diagram of a conventional process for forming a phase-shift photomask is shown;

[0046] Figure 2 A cross-sectional schematic diagram of a phase-shift photomask according to an embodiment of the present invention is shown;

[0047] Figure 3 A schematic diagram of the phase shift principle of a phase shift photomask is shown;

[0048] Figure 4 A schematic diagram showing a process of manufacturing a phase-shift photomask according to an embodiment of the present invention; and

[0049] Figure 5 A cross-sectional schematic diagram of a process for forming a phase-shift photomask according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0050] In the following description, the present invention is described with reference to various embodiments. However, those skilled in the art will recognize that various embodiments can be implemented without one or more specific details or with other replacement and / or additional methods, materials or components. In other cases, well-known structures, materials or operations are not shown or described in detail to avoid blurring the inventive point of the present invention. Similarly, for the purpose of explanation, specific quantities, materials and configurations are set forth to provide a comprehensive understanding of embodiments of the present invention. However, the present invention is not limited to these specific details. In addition, it should be understood that the various embodiments shown in the drawings are illustrative representations and are not necessarily drawn in correct proportions.

[0051] In this specification, reference to "one embodiment" or "the embodiment" means that a particular feature, structure, or characteristic described in conjunction with the embodiment is included in at least one embodiment of the present invention. The phrase "in one embodiment" appearing in various places in this specification does not necessarily all refer to the same embodiment.

[0052] In this specification, unless otherwise specified, "arranged on...", "arranged above..." and "arranged above..." do not exclude the existence of an intermediate between the two. In addition, "arranged on or above..." only indicates the relative positional relationship between two components, and in certain cases, such as after reversing the product direction, it can also be converted into "arranged below or below...", and vice versa.

[0053] In this specification, unless otherwise specified, the quantifiers "a", "an" do not exclude the presence of a plurality of elements, and the quantifiers "plurality" and "multiple" refer to one or more than one elements.

[0054] It should be noted that the embodiments of the present invention describe the method steps in a specific order, but this is only for the purpose of illustrating the specific embodiment, rather than limiting the order of the steps. On the contrary, in different embodiments of the present invention, the order of the steps can be adjusted according to actual needs.

[0055] The technical solutions in the embodiments of the present invention are described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0056] Figure 2 FIG. 1 is a cross-sectional schematic diagram of a phase-shift photomask according to an embodiment of the present invention. Figure 2 As shown, the phase-shift photomask includes a substrate 201 and a phase-shift layer 202. The phase-shift layer 202 is formed on the substrate 201 and is used to change the phase of light incident into the substrate 201. Figure 2 As shown, the phase-shift layer 202 includes a first phase-shift layer portion 2021 and a second phase-shift layer portion 2022, and the thickness of the first phase-shift layer portion 2021 is greater than the thickness of the second phase-shift layer portion 2022. In one embodiment, the thickness of the first phase-shift layer portion 2021 ranges from 50 nm to 200 nm; and / or the thickness of the second phase-shift layer portion 2022 ranges from 10 nm to 50 nm.

[0057] In one embodiment, the substrate 201 includes a quartz substrate. In fact, the substrate 201 can also be set to include at least one of glass, quartz, fused silica, calcium fluoride, silicon nitride, titanium oxide alloy, sapphire, etc. as needed. In actual use, a suitable material can be used as the substrate 201 as needed. In one embodiment, the thickness of the substrate 201 ranges from 0.3 to 0.9 cm, for example, the thickness of the substrate 201 can be 0.8 cm.

[0058] In one embodiment, the material of the phase shift layer 202 includes at least one of molybdenum oxynitride silicon (MoS iON) or molybdenum silicide (MoSi). In fact, the phase shift layer 202 can also be set to silicon nitride, tantalum silicide, tantalum nitride or other suitable materials as needed. In some embodiments, the phase shift layer 202 is a single layer, and in other embodiments, the phase shift layer 202 includes multiple layers, such as a combination of molybdenum silicide and silicon oxide.

[0059] Figure 3 The schematic diagram of the phase shift principle of the phase shift photomask is shown in FIG. Figure 3As shown in the figure, when light is incident into the substrate, the phase of the light incident into the phase shift layer is reversed by 180° due to the presence of the phase shift layer, thereby causing destructive interference of the light fields of adjacent light-transmitting areas, reducing the light intensity of the dark area in the light field distribution, and increasing the light field of the bright area, so as to improve the contrast and resolution. Since the light field distribution in the bright area becomes steeper, the exposure tolerance is also improved.

[0060] The phase angle reversal satisfies the following equation:

[0061]

[0062] Wherein, P represents the phase angle, Tpsl represents the thickness of the phase shift layer, npsl represents the refractive index of the phase shift layer under certain light source conditions, nair represents the refractive index of air, λ represents the wavelength of the light source, and * represents multiplication.

[0063] Taking a certain KrF photomask substrate as an example, the refractive index of the phase shift layer at a wavelength of 193nm is 2.32, the refractive index of the phase shift layer at a wavelength of 248nm is 2.3, and nair = 1. Under the KrF 248nm light source, the phase angle of the first part of the phase shift layer is 180°. At this time, according to the above formula, the thickness of the first part of the phase shift layer can be calculated.

[0064]

[0065] Wherein, P1 represents the phase angle of 180°, Tpsl1 represents the thickness of the first part of the phase shift layer, npsl1 represents the refractive index of the phase shift layer under the KrF light source condition of 2.3, nair=1, λ1 represents the wavelength of the KrF light source of 248nm, and * represents multiplication. It can be obtained that Tpsl1=95.38nm.

[0066] If the phase-shift photomask having a phase-shift layer with a thickness of Tpsl1 is directly applied under a 193nm light source, the phase angle is P=(95.38*2.32-95.38) / 193*360°=234.84°, which is not equal to 180°, and therefore cannot be directly applied.

[0067] If the phase angle remains at 180° under 193nm light source, the thickness of the phase shift layer needs to be changed. Calculate the thickness under 193nm light source, 180° = (2.32Tetch-Tetch) / 193*360°, and Tetch = 73.1nm.

[0068] The thickness Tpsl2 of the second part of the phase shift layer satisfies the following formula:

[0069] Tpsl2=Tpsl1-Tetch

[0070] Tpsl1=95.38nm, Tetch=73.1nm, substituting into the equation, we can get the thickness of the second part of the phase-shift layer, Tpsl2=22.28nm.

[0071] In one embodiment, the thickness of the first part 2021 of the phase-shift layer and the thickness of the second part 2022 of the phase-shift layer can be adjusted accordingly according to the change of the refractive index of the material, which will not be elaborated here.

[0072] Figure 4 The figure shows a flow chart of a method for manufacturing a phase-shift photomask according to an embodiment of the present invention. Figure 5 A schematic cross-sectional diagram of a process for forming a phase-shift photomask according to an embodiment of the present invention is shown. Figure 4 and Figure 5 A method for manufacturing a phase-shift photomask according to the present invention is described.

[0073] First, a photomask base is provided, the photomask base comprising a substrate 201, a phase shift layer 202, a chrome layer 203, and a photoresist 204. In one embodiment, the substrate 201 may comprise at least one of glass, quartz, fused silica, calcium fluoride, silicon nitride, titanium oxide alloy, sapphire, etc. In one embodiment, the material of the phase shift layer 202 comprises at least one of molybdenum oxynitride silicide or molybdenum silicide.

[0074] Next, the photomask substrate is photolithographically processed and developed to form a patterned photoresist, exposing a portion of the chromium layer below the photoresist.

[0075] Next, the chromium layer is etched to form a patterned chromium layer. In one embodiment, the etching is performed using a dry etching machine to etch away the exposed chromium layer.

[0076] Next, the patterned photoresist is removed. In one embodiment, the photoresist that has not been developed due to lack of exposure is removed by acid washing or the like.

[0077] Next, the phase-shift layer is etched. In one embodiment, the exposed phase-shift layer is etched away by special gas in a dry etching machine to form the second part of the phase-shift layer, and the unetched phase-shift layer is the second part of the phase-shift layer. In one embodiment, when etching the phase-shift layer using a dry etching machine, the etching thickness is determined by observing the signal reflected by the optical emission spectroscopy (OES) during the process, and the etching seconds are captured. There is a corresponding relationship between the etching thickness and the etching seconds.

[0078] Finally, the patterned chromium layer is etched to form a phase-shift photomask. Because the final wafer factory requires that the mask pattern area only have a layer of molybdenum silicide on the quartz glass to achieve a 180° phase reversal effect, the chromium layer on the molybdenum silicide should be etched off at the end to complete the production and enter the subsequent measurement and inspection. The phase-shift photomask includes a substrate 201 and a phase-shift layer 202. The phase-shift layer 202 includes a first phase-shift layer portion 2021 and a second phase-shift layer portion 2022. The thickness of the first phase-shift layer portion 2021 is greater than the thickness of the second phase-shift layer portion 2022.

[0079] The thickness of the first part of the phase-shift layer satisfies the following formula:

[0080]

[0081] Wherein, P1 represents the phase angle of 180°, Tpsl1 represents the thickness of the first part of the phase shift layer, npsl1 represents the refractive index of the phase shift layer under the KrF light source condition, nair represents the refractive index of air, λ1 represents the wavelength of the KrF light source, and * represents multiplication;

[0082] The thickness Tpsl2 of the second part of the phase shift layer satisfies the following formula:

[0083] Tpsl2=Tpsl1-Tetch

[0084] Among them, Tetch satisfies the following formula:

[0085]

[0086] Wherein, Petch represents a phase angle of 180°, Tetch represents the thickness difference between the first part of the phase shift layer and the second part of the phase shift layer, npsl2 represents the refractive index of the phase shift layer under ArF light source conditions, nair represents the refractive index of air, λ2 represents the wavelength of the ArF light source, and * represents multiplication.

[0087] In one embodiment, the thickness of the first phase-shift layer portion 2021 is in the range of 50 nm to 200 nm; and / or the thickness of the second phase-shift layer portion 2022 is in the range of 10 nm to 50 nm. In one embodiment, the thickness of the first phase-shift layer portion 2021 is 95.38 nm; and / or the thickness of the second phase-shift layer portion 2022 is in the range of 22.28 nm.

[0088] The phase-shift photomask provided by the present invention can achieve the same phase contrast of 180 degrees as the ArF photomask at a wavelength of 193m by precisely controlling the thickness of the phase-shift layer. The KrF photomask can replace the ArF photomask without affecting the performance, thereby reducing the production cost of the photomask supplier. The price of the KrF substrate is about one-sixth of that of the ArF substrate. If the KrF photomask replaces the ArF photomask, the change of the substrate can reduce the material cost by 83% and increase the gross profit by 25-30%.

[0089] Although various embodiments of the present invention are described above, it should be understood that they are presented as examples only and not as limitations. It is obvious to those skilled in the relevant art that various combinations, modifications and changes can be made thereto without departing from the spirit and scope of the present invention. Therefore, the breadth and scope of the present invention disclosed herein should not be limited by the exemplary embodiments disclosed above, but should only be defined according to the attached claims and their equivalents.

Claims

1. A phase-shift photomask, characterized in that: include: substrate; a phase shift layer formed on the substrate; The phase-shift layer comprises a first phase-shift layer portion and a second phase-shift layer portion; The thickness of the first part of the phase-shift layer is greater than the thickness of the second part of the phase-shift layer; and under the condition of KrF light source, the phase angle of the first part of the phase-shift layer is 180°.

2. The phase-shift photomask according to claim 1, characterized in that: The material of the phase shift layer includes at least one of molybdenum oxynitride and molybdenum silicide.

3. The phase-shift photomask according to claim 1, characterized in that: The thickness of the first part of the phase-shift layer satisfies the following formula: Where P1 represents the phase angle of 180°, T psl1 represents the thickness of the first part of the phase shift layer, n psl1 represents the refractive index of the phase shift layer under KrF light source conditions, n air Air represents the refractive index of air, λ1 represents the wavelength of the KrF light source, and * represents multiplication; The thickness T of the second portion of the phase shift layer psl2 Satisfies the following formula, T psl2 =T psl1 -T etch Among them, T etch Satisfies the following formula, Among them, P etch Indicates a phase angle of 180°, T etch represents the thickness difference between the first part of the phase-shift layer and the second part of the phase-shift layer, n psl2 represents the refractive index of the phase shift layer under ArF light source conditions, n air Air represents the refractive index of air, λ2 represents the wavelength of the ArF light source, and * represents multiplication.

4. The phase-shift photomask according to claim 1, characterized in that: The thickness of the first portion of the phase-shift layer is in the range of 50 nm to 200 nm; and / or The thickness of the second portion of the phase-shift layer is in a range of 10 nm to 50 nm.

5. The phase-shift photomask according to claim 1, characterized in that: The thickness of the first part of the phase-shift layer is 95.38 nm; and / or The thickness of the second portion of the phase-shift layer is in the range of 22.28 nm.

6. A method for manufacturing a phase-shift photomask, characterized in that: The steps include: Providing a photomask base, the photomask base comprising a substrate, a phase shift layer, a chrome layer and a photoresist; Photolithography and development of photomask substrate to form patterned photoresist; etching the chromium layer to form a patterned chromium layer; removing patterned photoresist; etching the phase shift layer; The patterned chromium layer is etched to form a phase-shift photomask.

7. The method for manufacturing a phase-shift photomask according to claim 6, characterized in that: The substrate includes a quartz substrate.

8. The method for manufacturing a phase-shift photomask according to claim 6, characterized in that: The material of the phase shift layer includes at least one of molybdenum oxynitride and molybdenum silicide.

9. The method for manufacturing a phase-shift photomask according to claim 6, characterized in that: The phase-shift photomask comprises a first phase-shift layer portion and a second phase-shift layer portion; the thickness of the first phase-shift layer portion is greater than the thickness of the second phase-shift layer portion.

10. The method for manufacturing a phase-shift photomask according to claim 9, characterized in that: The thickness of the first part of the phase-shift layer satisfies the following formula: Where P1 represents the phase angle of 180°, T psl1 represents the thickness of the first part of the phase shift layer, n psl1 represents the refractive index of the phase shift layer under KrF light source conditions, n air Air represents the refractive index of air, λ1 represents the wavelength of the KrF light source, and * represents multiplication; The thickness T of the second portion of the phase shift layer psl2 Satisfies the following formula, T psl2 =T psl1 -T etch Among them, T etch Satisfies the following formula, Among them, P etch Indicates a phase angle of 180°, T etch represents the thickness difference between the first part of the phase-shift layer and the second part of the phase-shift layer, n psl2 represents the refractive index of the phase shift layer under ArF light source conditions, n air Air represents the refractive index of air, λ2 represents the wavelength of the ArF light source, and * represents multiplication.

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