Co-sputtering alloy film, preparation method and application

Abstract

The invention discloses a co-sputtering alloy film, a preparation method and application, belongs to the technical field of extreme ultraviolet mask absorbing materials, and relates to a method for preparing a Pt-W alloy film through magnetron sputtering and co-sputtering and related application thereof.The preparation method comprises the following steps that a three-layer structure is designed according to the combining capacity and the etching capacity of the film, a three-layer film system including an upper layer of Pt, a middle layer of Pt-W alloy and a lower layer of W is adopted, and a Pt target material and a W target material are installed on a magnetron sputtering system; preparing a co-sputtering Pt-W alloy film on the substrate by adopting a double-target magnetron sputtering co-sputtering method; and the co-sputtering Pt-W alloy film is used for calculating and designing the element proportion. The invention provides a scheme for research and development of a novel extreme ultraviolet mask absorption layer.

Description

Technical Field

[0001] This invention belongs to the field of extreme ultraviolet mask absorption material technology, specifically a co-sputtered alloy thin film, its preparation method, and its application. Background Technology

[0002] Extreme ultraviolet (EUV) lithography plays a crucial role in the fabrication of advanced semiconductor devices. In EUV lithography, EUV masks are typically used, from which EUV light is reflected in a patterned manner. To achieve this, the EUV mask comprises a reflective surface covered by a patterned absorption layer. Currently, EUV lithography with a numerical aperture (NA) of 0.33 has successfully entered mass production, while achieving next-generation NAs of 0.55 NA and even higher remains challenging. EUV masks are one of the key technologies in EUV lithography. Current EUV masks primarily use tantalum-based materials as the absorber. To continue scaling to next-generation and more advanced technologies, the mask 3D effect caused by the absorber layer thickness presents a significant challenge. New EUV mask absorber materials are currently being developed as a possible solution to further improve EUV mask performance and effectively overcome the challenges posed by the mask 3D effect.

[0003] In recent years, various absorbing materials have been proposed for high-NA extreme ultraviolet lithography (EUVL), but there is still no clear consensus on the optimal approach. For example, Ru / Ta bilayer films exhibit moderate imaging and etching properties, but the complexity of their bilayer structure can pose challenges to mask fabrication and repair. Although Ta-Co alloys improve NILS and DoF compared to conventional Ta, they suffer from increased telecentric error and lack experimental validation for etching and material stability. Low-n absorbers can reduce spot size and improve image contrast through phase shift effects, but they often face challenges in etching resistance and patterning, highlighting the trade-off between optical performance and process compatibility. These limitations have prompted efforts to develop absorption systems that achieve both high imaging performance and process-friendly etching characteristics.

[0004] Therefore, there remains a need in the field for some or all of the EUV absorbers that address the aforementioned problems. Summary of the Invention

[0005] A co-sputtered alloy thin film has a multilayer structure, comprising: a bottom layer, an intermediate layer, and a top layer stacked sequentially; wherein the bottom layer contains element M1, the top layer contains element M2, and the intermediate layer is an alloy of M1 and M2; M1 is selected from one or more of tungsten, tantalum, and molybdenum; and element M2 is selected from one or more of platinum, palladium, iridium, and gold.

[0006] Furthermore, the atomic ratio of M2 to M1 in the intermediate layer is in the range of 1:4 to 4:1.

[0007] Furthermore, the total thickness of the film is less than 50nm, and the thickness of the bottom layer and the top layer are each 1nm-10nm.

[0008] Furthermore, the surface roughness RMS of the alloy film is below 0.3 nm, and the intermediate layer has an amorphous structure or a nanocrystalline structure with an average grain size ≤10 nm.

[0009] A method for preparing an alloy thin film includes providing an M1 target and an M2 target; in a vacuum chamber, a bottom layer, an intermediate layer, and a top layer are sequentially deposited on a substrate by magnetron sputtering; wherein, when depositing the intermediate layer, the M1 target and the M2 target are co-sputtered, and the elemental ratio of M1 to M2 in the intermediate layer is controlled by controlling the sputtering power of the M1 target and the M2 target.

[0010] Furthermore, DC magnetron sputtering was used to sputter the M2 target, and radio frequency magnetron sputtering was used to sputter the M1 target.

[0011] Application of an alloy thin film in extreme ultraviolet photomasks.

[0012] This invention provides a co-sputtered alloy thin film, its preparation method, and its application, including the following:

[0013] (1) Based on the bonding and etching capabilities of the thin film, a three-layer structure is designed: upper layer Pt, middle layer Pt-W alloy, and lower layer W. The element ratio of the middle film layer is designed to be 1:2, 1:1, and 2:1 based on the required n and k values ​​of the absorption layer.

[0014] (2) Fix the Pt target and W target on the b target and c target positions of the sputtering instrument respectively, fix the substrate on the substrate holder, close the external vent valve and the cavity cover, and seal the cavity;

[0015] (3) Turn on the vacuum gauge and mechanical pump to evacuate the vacuum. When the vacuum in the cavity reaches 10 Pa or below, start the molecular pump to evacuate to 6 × 10 Pa. -4 Below pa;

[0016] (4) High-purity Ar gas was used as the sputtering gas, the Ar gas flow rate was set to 60 sccm, and the gas pressure in the deposition chamber was 2.0 Pa;

[0017] (5) Set the sputtering power of the W target to 200W and the sputtering time to 11s.

[0018] (6) When co-sputtering Pt:W = 1:2, the sputtering power of the Pt target is set to 70W and the sputtering power of the W target is set to 350W. When Pt:W = 1:1, the sputtering power of the Pt target is set to 100W and the sputtering power of the W target is set to 300W. When Pt:W = 2:1, the sputtering power of the Pt target is set to 100W and the sputtering power of the W target is set to 150W.

[0019] (7) Set the sputtering power of the Pt target to 100W and the sputtering time to 8s.

[0020] The substrate is a silicon wafer.

[0021] When sputtering, the Pt target uses DC magnetron sputtering, and the W target uses RF magnetron sputtering.

[0022] The sputtering targets used are Pt targets with a purity of 99.99% and W targets with a purity of 99.99%.

[0023] The substrate is cleaned before co-sputtering.

[0024] The cleaning process involves sequentially cleaning with acetone, anhydrous ethanol, and water under ultrasonic conditions.

[0025] Before sputtering, the target material is pre-sputtered.

[0026] During sputtering, the distance between the substrate and the target is 200 mm, and the substrate rotates at 15.0 rpm.

[0027] The beneficial effects of this invention are as follows:

[0028] 1) This invention prepares the required n and k values ​​for the extreme ultraviolet absorption layer through film layer design, enabling Pt-W alloy thin films to have good optical properties.

[0029] 2) The three-layer film structure designed in this invention gives the Pt-W alloy thin film better bonding and etching capabilities.

[0030] 3) By controlling the working power of the target material separately to change its sputtering rate, the present invention can easily change the proportion of different target material components in the deposited film, and can well control the uniformity and controllability of the distribution of different elemental components in the prepared film.

[0031] 4) The extreme ultraviolet absorption layer material Pt-W alloy thin film of the present invention can have low crystallinity (e.g., they can have an average grain size of 10 nm or less, or they can be amorphous).

[0032] 5) The surface roughness of the Pt-W alloy thin film, the extreme ultraviolet absorption layer material of the present invention, is relatively small (e.g., compared to the surface roughness in specific applications of the absorption layer).

[0033] 6) The Pt-W alloy thin film of the extreme ultraviolet absorption layer material of the present invention can have good thermal stability and chemical stability.

[0034] 7) When the extreme ultraviolet absorption layer material Pt-W alloy thin film of the present invention achieves the same or similar absorbance, the extreme ultraviolet absorption layer can be made thinner, which can reduce the mask 3D effect. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of an alloy thin film.

[0036] Figure 2 The image shows the XRD pattern of the alloy thin film in Example 1.

[0037] Figure 3 The image shown is the XRD pattern of the alloy thin film in Example 2.

[0038] Figure 4 The image shows the XRD pattern of the alloy thin film in Example 3.

[0039] Figure 5 This is an atomic force microscope image of the alloy thin film in Example 1.

[0040] Figure 6 This is an atomic force microscope image of the alloy thin film in Example 2.

[0041] Figure 7 This is an atomic force microscope image of the alloy thin film in Example 3.

[0042] Figure 8 The figure shows the X-ray reflectance measurement results of the alloy thin film before and after the cleaning test in Example 1.

[0043] Figure 9 The figure shows the X-ray reflectance measurement results of the alloy thin film before and after the cleaning test in Example 2.

[0044] Figure 10 The figure shows the X-ray reflectance measurement results of the alloy thin film before and after the cleaning test in Example 3.

[0045] Figure 11 The images show the XRD patterns of the alloy thin film before and after the thermal stability test in Example 1.

[0046] Figure 12 The images show the XRD patterns of the alloy thin film before and after the thermal stability test in Example 1.

[0047] Figure 13 The images show the XRD patterns of the alloy thin film before and after the thermal stability test in Example 1. Detailed Implementation

[0048] This invention provides a method for designing and preparing Pt-W alloy thin films, comprising the following steps:

[0049] (1) Based on the bonding and etching capabilities of the thin film, a three-layer structure is designed: upper layer Pt, middle layer Pt-W alloy, and lower layer W. The n and k values ​​required by the absorbing material (n and k are the refractive index and extinction coefficient of the material under 13.5nm extreme ultraviolet light) are designed, and the element ratio of the middle layer is 1:2, 1:1, or 2:1.

[0050] (2) Fix the Pt target and W target on the b target and c target positions of the sputtering instrument respectively, fix the substrate on the substrate holder, close the external vent valve and the cavity cover, and seal the cavity;

[0051] (3) Turn on the vacuum gauge and mechanical pump to evacuate the vacuum. When the vacuum in the cavity reaches 10 Pa or below, start the molecular pump to evacuate to 6 × 10 Pa. -4 Below pa;

[0052] (4) High-purity Ar gas was used as the sputtering gas, the Ar gas flow rate was set to 60 sccm, and the gas pressure in the deposition chamber was 2.0 Pa;

[0053] (5) Set the sputtering power of the W target to 200W and plate for 11s.

[0054] (6) When Pt:W = 1:2, the sputtering power of the Pt target is set to 70W and the sputtering power of the W target is set to 350W.

[0055] When the Pt:W ratio is 1:1, the sputtering power of the Pt target is set to 100W and the sputtering power of the W target is set to 300W.

[0056] When the Pt:W ratio is 2:1, the sputtering power of the Pt target is set to 100W and the sputtering power of the W target is set to 150W.

[0057] (7) Set the sputtering power of the Pt target to 100W and plate for 8s.

[0058] In this invention, unless otherwise specified, all raw materials used in the preparation are commercially available products well known to those skilled in the art.

[0059] The substrate is made of Si wafer and has a thickness of 0.3 mm.

[0060] Before sputtering, the substrate is cleaned. Cleaning is performed under ultrasonic conditions, sequentially with acetone, anhydrous ethanol, and deionized water. The ultrasonication time is 15 minutes. There are no specific limitations on the ultrasonic frequency; any frequency well-known to those skilled in the art can be used.

[0061] The purpose of cleaning is to remove surface dirt and impurities, ensure the cleanliness and dryness of the substrate surface, and thus ensure the quality of the film and its adhesion to the substrate.

[0062] After cleaning, drying is performed; drying is carried out by blowing with a nitrogen gun or by using a dryer; there are no special limitations on the specific conditions and parameters for blowing and drying, and conditions and parameters well known to those skilled in the art can be used.

[0063] The vacuum level of the vacuum reaction chamber is 6×10⁻⁶. -4 Below Pa. The vacuum level in the vacuum reaction chamber is preferably achieved by evacuation using a mechanical pump or a molecular pump.

[0064] The sputtering targets used are Pt targets with a purity of 99.99% and W targets with a purity of 99.99%.

[0065] Before sputtering, the target material is pre-sputtered. The pre-sputtering conditions are: the flow rate of argon gas into the reaction chamber is 60 sccm; the gas pressure in the reaction chamber is 2.0 Pa; and the sputtering time is 5 to 10 min.

[0066] The pre-sputtering process involves evacuating the sputtering chamber to a pressure of 6 × 10⁻⁶ using a mechanical or molecular pump. -4 Below Pa, argon gas is introduced into the reaction chamber by controlling the gas flow meter, and the sputtering gas pressure is controlled to 2.0 Pa by the throttle valve. The target material is blocked by a baffle for pre-sputtering.

[0067] The purpose of pre-sputtering is to remove impurities from the surfaces of Pt and W targets.

[0068] During sputtering, the distance between the substrate and the target is 200 mm, and the substrate rotation speed is 15 rpm.

[0069] The Pt-W alloy thin film prepared by the above method has a thickness of 35 nm, with an upper Pt layer of 3 nm and a lower W layer of 3 nm. The film structure is as follows: Figure 1 As shown.

[0070] The following detailed description of the method for preparing Pt-W alloy thin films using magnetron sputtering co-sputtering provided by the present invention, with reference to the embodiments, should not be construed as limiting the scope of protection of the present invention.

[0071] Example 1

[0072] The Si substrate was ultrasonically cleaned for 15 minutes in sequence with acetone, anhydrous ethanol and high-purity deionized water, then dried with a nitrogen gun and placed in a sputtering chamber.

[0073] Place the Pt target and W target on the b target and c target positions of the sputtering instrument respectively and fix them. Fix the substrate on the substrate holder, close the external vent valve and the cavity cover, and seal the cavity.

[0074] Turn on the vacuum gauge and mechanical pump to evacuate the chamber. Once the vacuum inside the chamber reaches 10 Pa or below, start the molecular pump and evacuate to 6 × 10 Pa. -4 Below pa;

[0075] High-purity Ar gas was used as the sputtering gas, with an Ar gas flow rate of 60 sccm and a deposition chamber pressure of 2.0 Pa.

[0076] The sputtering power of the W target was set to 200W for 11 seconds.

[0077] When preparing Pt:W = 1:2, the sputtering power of the Pt target was set to 70W and the sputtering power of the W target was set to 350W.

[0078] The sputtering power of the Pt target was set to 100W for 8 seconds.

[0079] The PtW2 thin film was subjected to XRD testing, and the test results are as follows: Figure 2 As shown, by Figure 2 It can be seen that the PtW2 film has inconspicuous protrusions at around 40°, which indicates that the film structure is amorphous.

[0080] The PtW2 thin film was subjected to atomic force microscopy, and the test results are as follows: Figure 5 As shown, by Figure 5 It can be seen that the PtW2 film has good surface roughness, with a roughness RMS of 0.139 nm.

[0081] The PtW2 film was subjected to a cleaning test, and the test results are as follows: Figure 8 As shown, by Figure 8 It can be seen that the PtW2 film is relatively stable, and there is no significant loss of components or structural changes in common mask cleaning solutions such as DIW, NH4OH, and TMAH.

[0082] The thermal stability of the PtW2 film was tested, and the test results are as follows: Figure 11 As shown, by Figure 11 It can be seen that the PtW2 film has good thermal stability; after heating at 100℃ for 1 day, the film structure does not change significantly.

[0083] Example 2

[0084] The Si substrate was ultrasonically cleaned for 15 minutes in sequence with acetone, anhydrous ethanol and high-purity deionized water, then dried with a nitrogen gun and placed in a sputtering chamber.

[0085] Place the Pt target and W target on the b target and c target positions of the sputtering instrument respectively and fix them. Fix the substrate on the substrate holder, close the external vent valve and the cavity cover, and seal the cavity.

[0086] Turn on the vacuum gauge and mechanical pump to evacuate the chamber. Once the vacuum inside the chamber reaches 10 Pa or below, start the molecular pump and evacuate to 6 × 10 Pa. -4 Below pa;

[0087] High-purity Ar gas was used as the sputtering gas, with an Ar gas flow rate of 60 sccm and a deposition chamber pressure of 2.0 Pa.

[0088] The sputtering power of the W target was set to 200W for 11 seconds.

[0089] When preparing Pt:W = 1:1, the sputtering power of the Pt target was set to 100W and the sputtering power of the W target was set to 300W.

[0090] The sputtering power of the Pt target was set to 100W for 8 seconds.

[0091] The PtW thin film was subjected to XRD testing, and the test results are as follows: Figure 3 As shown, by Figure 3 It can be seen that the PtW film has a low intensity peak at around 40°, which indicates that the film structure has low crystallinity and forms nanocrystals.

[0092] The PtW thin film was subjected to atomic force microscopy, and the test results are as follows: Figure 6 As shown, by Figure 6 It can be seen that the PtW film has good surface roughness, with a roughness RMS of 0.182 nm.

[0093] The PtW film was subjected to a cleaning test, and the test results are as follows: Figure 9 As shown, by Figure 9 It can be seen that the PtW film is relatively stable, and there is no significant loss of components or structural changes in common mask cleaning solutions such as DIW, NH4OH, and TMAH.

[0094] The PtW thin film was subjected to thermal stability testing, and the test results are as follows: Figure 12 As shown, by Figure 12 It can be seen that the PtW film has good thermal stability; after heating at 100℃ for 1 day, the film structure does not change significantly.

[0095] Example 3

[0096] The Si substrate was ultrasonically cleaned for 15 minutes in sequence with acetone, anhydrous ethanol and high-purity deionized water, then dried with a nitrogen gun and placed in a sputtering chamber.

[0097] Place the Pt target and W target on the b target and c target positions of the sputtering instrument respectively and fix them. Fix the substrate on the substrate holder, close the external vent valve and the cavity cover, and seal the cavity.

[0098] Turn on the vacuum gauge and mechanical pump to evacuate the chamber. Once the vacuum inside the chamber reaches 10 Pa or below, start the molecular pump and evacuate to 6 × 10 Pa. -4 Below pa;

[0099] High-purity Ar gas was used as the sputtering gas, with an Ar gas flow rate of 60 sccm and a deposition chamber pressure of 2.0 Pa.

[0100] The sputtering power of the W target was set to 200W for 11 seconds.

[0101] When preparing Pt:W = 2:1, the sputtering power of the Pt target was set to 100W and the sputtering power of the W target was set to 150W.

[0102] The sputtering power of the Pt target was set to 100W for 8 seconds.

[0103] The Pt2W thin film was subjected to XRD testing, and the test results are as follows: Figure 4 As shown, by Figure 4 It can be seen that the Pt2W thin film has a low intensity peak at around 40°, which indicates that the thin film structure has low crystallinity and forms nanocrystals.

[0104] The Pt2W thin film was subjected to atomic force microscopy, and the test results are as follows: Figure 7 As shown, by Figure 7 It can be seen that the Pt2W thin film has good surface roughness, with a roughness RMS of 0.225 nm.

[0105] The Pt2W thin film was subjected to a cleaning test, and the test results are as follows: Figure 10 As shown, by Figure 10 It can be seen that the Pt2W film is relatively stable, and there is no significant loss of components or structural change in common mask cleaning solutions such as DIW, NH4OH, and TMAH.

[0106] The thermal stability of the Pt2W thin film was tested, and the test results are as follows: Figure 13 As shown, by Figure 13 It can be seen that the Pt2W thin film has good thermal stability, and the film structure does not change significantly after being heated at 100℃ for 1 day.

[0107] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions, and improvements made by those skilled in the art within the scope of the technology disclosed in the present invention, and within the spirit and principles of the present invention, should be included within the scope of protection of the present invention. Furthermore, all content not described in detail in this specification is prior art known to those skilled in the art.

Claims

1. A co-sputtered alloy thin film, characterized in that, The thin film is a multi-layer structure, comprising: a bottom layer, an intermediate layer and a top layer which are sequentially stacked; wherein the bottom layer contains element M1, the top layer contains element M2, and the intermediate layer is an alloy of M1 and M2; M1 is selected from one or more of tungsten, tantalum and molybdenum; and M2 is selected from one or more of platinum, palladium, iridium and gold.

2. The co-sputtered alloy thin film of claim 1, wherein, The atomic ratio of M2 to M1 in the intermediate layer is in the range of 1:4 to 4:

1.

3. The alloy film according to claim 1 or 2, characterized by The total thickness of the thin film is 50 nm or less, and the thickness of each of the bottom layer and the top layer is independently 1 nm to 10 nm.

4. The alloy film of claim 3, wherein The surface roughness RMS of the alloy thin film is 0.3 nm or less, and the intermediate layer is an amorphous structure or a nanocrystalline structure with an average grain size of ≤10 nm.

5. A method of making the alloy film of claim 4, wherein M1 and M2 target materials are provided; in a vacuum chamber, a bottom layer, an intermediate layer and a top layer are sequentially deposited on a substrate by magnetron sputtering; wherein, when depositing the intermediate layer, the M1 and M2 target materials are used for co-sputtering, and the element ratio of M1 to M2 in the intermediate layer is controlled by controlling the sputtering power of the M1 and M2 target materials.

6. The method of claim 5, wherein, The M2 target material is sputtered by a direct current magnetron sputtering method, and the M1 target material is sputtered by a radio frequency magnetron sputtering method.

7. Use of the alloy thin film of claim 4 in an extreme ultraviolet mask blank.

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