Extreme ultraviolet multilayer film and preparation method and application thereof

Abstract

The invention provides an extreme ultraviolet multilayer film and a preparation method and application thereof, and belongs to the technical field of semiconductor material preparation. The extreme ultraviolet multilayer film comprises repeated film units, each film unit comprises a Mo layer, a BN layer, a C layer and a Si layer which are stacked in sequence, and the adjacent film units are connected through the Si layer and the Mo layer; the bottom layer of the extreme ultraviolet multilayer film is a Mo layer, and the uppermost layer is a Si layer. The BN layer and the C layer adopted by the invention belong to low-dissipation film layers, are good in high-temperature stability, do not react with the main materials Mo layer and Si layer, do not diffuse with the main materials, and form an alternating laminated structure with the Mo layer and the Si layer as spacing layers, so that the prepared extreme ultraviolet multi-layer film has the advantages that the extreme ultraviolet effect is good, and the service life of the extreme ultraviolet multi-layer film is prolonged. And the temperature stability can be improved while the reflection efficiency is ensured. Therefore, the extreme ultraviolet multilayer film provided by the invention has radiation resistance and high temperature resistance, and meanwhile, the reflectivity reduction can be controlled within 0.5%.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor material preparation, and in particular relates to an extreme ultraviolet multilayer film and a preparation method and application thereof. Background Art

[0002] EUV multilayers are widely used in today's semiconductor industry and are one of the most important optical components. In particular, Mo / Si multilayers with excellent reflective properties play an extremely important role in laser plasma diagnosis, EUV lithography, etc. This film has a high reflectivity. Mo / Si multilayers are ideal reflector films in the 13.5nm EUV band. Its combination with EUV light sources makes EUV lithography one of the most advanced manufacturing methods. The practical application of EUV light sources has put forward many requirements for Mo / Si multilayers, such as high reflectivity, high thermal stability, resistance to radiation damage, and large aperture. In particular, EUV multilayers used in lithography machines need to have good thermal stability under long-term high light flux irradiation due to their large area and high precision requirements, in order to ensure that the optical components can operate stably for a long time without a significant drop in reflectivity.

[0003] There are many ways to improve the high temperature resistance of thin films: select materials with high thermal stability as components of the film. For example, in the multilayer film structure, Si in the Mo / Si multilayer film is replaced by SiC with better thermal stability. By optimizing the process parameters and annealing parameters, the crystallinity and density of the film are improved, thereby enhancing its high temperature resistance; design a reasonable multilayer film structure, adjust the materials and thickness of each layer, and use the interface effect and interlayer interaction to improve the overall thermal stability of the film; anneal the film, and by controlling the annealing temperature and time, recrystallize or phase change occurs inside the film, thereby improving its high temperature resistance. For example, Mo / Si multilayer film samples are annealed at different temperatures to study their thermal stability.

[0004] Each of the above methods has its own advantages and disadvantages. For example, annealing can significantly reduce the stress of the EUV multilayer film, but it will also reduce its reflectivity. For semiconductor lithography, the reflectivity requirement is extremely high, and a 1% drop in performance will cause a significant reduction in the end light intensity. Therefore, a method that can minimize the impact on reflectivity is needed to improve the radiation resistance and high temperature resistance of the film. Summary of the invention

[0005] In view of this, the object of the present invention is to provide an extreme ultraviolet multilayer film and a preparation method and application thereof. The extreme ultraviolet multilayer film provided by the present invention has radiation resistance and high temperature resistance, and the reflectivity drop can be controlled within 0.5%.

[0006] In order to achieve the above object, the present invention provides the following scheme:

[0007] The present invention provides an extreme ultraviolet multilayer film, comprising repeated film units, each of which comprises a Mo layer, a BN layer, a C layer and a Si layer stacked in sequence, and adjacent film units are connected by a Si layer and a Mo layer; the bottom layer of the extreme ultraviolet multilayer film is a Mo layer, and the top layer is a Si layer.

[0008] Preferably, the repetition period of the membrane unit is 40 to 60.

[0009] Preferably, in each membrane unit, the thickness of the BN layer is 0.2-0.4 nm, the thickness of the C layer is 0.2-0.3 nm, the thickness of the Mo layer is 2.4-2.6 nm, and the thickness of the Si layer is 4.0-4.2 nm.

[0010] The present invention provides a method for preparing the extreme ultraviolet multilayer film described in the above scheme, comprising the following steps:

[0011] Using a Mo target, a B target, a C target and a Si target as sputtering targets, magnetron sputtering is repeatedly performed on a substrate in sequence to form repeated film units on the substrate, each film unit comprising a Mo layer, a BN layer, a C layer and a Si layer stacked in sequence, to obtain the extreme ultraviolet multilayer film;

[0012] The sputtering atmosphere for forming the BN layer includes nitrogen gas.

[0013] Preferably, the magnetron sputtering conditions for forming the BN layer include: using radio frequency magnetron sputtering; using a mixed gas of argon and nitrogen as the sputtering atmosphere, with a nitrogen volume content of 20-30%; and a magnetron sputtering temperature of 100-180°C.

[0014] Preferably, the magnetron sputtering conditions for forming the Mo layer, the C layer and the Si layer include: using DC pulse magnetron sputtering with a pulse frequency of 15000 Hz; and using argon as the sputtering atmosphere.

[0015] Preferably, the gas pressure of the magnetron sputtering is 0.26 Tor.

[0016] Preferably, the power of the magnetron sputtering is 120W to 350W.

[0017] Preferably, after the magnetron sputtering is completed, the obtained film material is annealed, the annealing temperature is 150-180° C., and the annealing holding time is 8-15 minutes.

[0018] The present invention provides the use of the extreme ultraviolet multilayer film described in the above scheme or the extreme ultraviolet multilayer film prepared by the preparation method described in the above scheme in a photolithography machine.

[0019] The present invention provides an extreme ultraviolet multilayer film, including repeated film units, each of which includes a Mo layer, a BN layer, a C layer and a Si layer stacked in sequence, and adjacent film units are connected by a Si layer and a Mo layer; the bottom layer of the extreme ultraviolet multilayer film is a Mo layer, and the top layer is a Si layer. The BN layer and the C layer used in the present invention are both low-dissipation film layers with good high-temperature stability, and will not react with the main materials Mo layer and Si layer, nor will they diffuse between the main materials. The BN layer and the C layer are used as spacer layers to form an alternating laminated structure with the Mo layer and the Si layer. The prepared extreme ultraviolet multilayer film can improve temperature stability while ensuring reflection efficiency. Therefore, the extreme ultraviolet multilayer film provided by the present invention is resistant to radiation and high temperature, and the reflectivity drop can be controlled within 0.5%.

[0020] In the present invention, when magnetron sputtering of BN is performed, the sputtering atmosphere is a mixed gas of nitrogen and argon, which can ensure stable forming of BN and the formation of hexagonal BN.

[0021] Furthermore, the present invention heats the substrate while coating the BN layer to ensure the formation of the desired crystalline boron nitride (hexagonal BN) and the content of the boron nitride phase; if the temperature is too low (below 100° C.), the formation rate of the hexagonal BN is low.

[0022] Furthermore, the present invention performs a short-term low-temperature (150-180°C) annealing treatment after preparation, which can eliminate stress and does not require long-term high-temperature annealing. High-temperature annealing is generally used to eliminate stress in thin films, but the consequence is that diffusion will occur between film materials under high temperature conditions, thereby changing the film structure and causing a decrease in reflectivity. After adding the intermediate layers of BN and C in the present invention, the temperature stability is good, the diffusion between the Mo layer and the Si layer is isolated, and the effect on the reflectivity is also small.

[0023] The original reflectivity of the Mo / Si multilayer film in the prior art is 68%. If it is annealed at 300°C, the reflectivity will decrease by 1% to 3%. However, the extreme ultraviolet multilayer film prepared by the present invention has a reflectivity only decreased by 0.48% (relative to the original reflectivity of 68%) after annealing at 300°C by adding intermediate layers of BN and C layers.

[0024] In addition, the diameter of the extreme ultraviolet multilayer film prepared by the present invention is ≥300 mm, which is a large-size optical element. DETAILED DESCRIPTION

[0025] The present invention provides an extreme ultraviolet multilayer film, comprising repeated film units, each of which comprises a Mo layer, a BN layer, a C layer and a Si layer stacked in sequence, and adjacent film units are connected by a Si layer and a Mo layer; the bottom layer of the extreme ultraviolet multilayer film is a Mo layer, and the top layer is a Si layer.

[0026] In the present invention, the repetition period of the membrane unit is preferably 40 to 60, and in the embodiment of the present invention, it can be 40, 50 or 60. In the present invention, the thickness of the BN layer in each membrane unit is preferably 0.2 to 0.4 nm, and in the embodiment of the present invention, it can be 0.2 nm, 0.3 nm or 0.4 nm; the thickness of the C layer is preferably 0.2 to 0.3 nm, and in the embodiment of the present invention, it can be 0.2 nm, 0.25 nm or 0.3 nm; the thickness of the Mo layer is preferably 2.4 to 2.6 nm, and in the embodiment of the present invention, it can be 2.4 nm, 2.5 nm or 2.6 nm; the thickness of the Si layer is preferably 4.0 to 4.2 nm, and in the embodiment of the present invention, it can be 4.0 nm, 4.1 nm or 4.2 nm.

[0027] The BN layer and C layer used in the present invention are both low-dissipation film layers with good high-temperature stability. They will not react with the main material Mo layer and Si layer, nor will they diffuse between the main materials. They are used as spacer layers to form an alternating laminated structure with the Mo layer and the Si layer. The prepared extreme ultraviolet multilayer film can improve temperature stability while ensuring reflection efficiency. Therefore, the extreme ultraviolet multilayer film provided by the present invention has radiation resistance and high temperature resistance, and the reflectivity drop can be controlled within 0.5%.

[0028] The present invention provides a method for preparing the extreme ultraviolet multilayer film described in the above scheme, comprising the following steps:

[0029] Using Mo target, B target, C target and Si target as sputtering targets, magnetron sputtering is repeatedly performed on a substrate in sequence to form repeated film units on the substrate, each film unit includes a Mo layer, a BN layer, a C layer and a Si layer stacked in sequence, to obtain the extreme ultraviolet multilayer film; the sputtering atmosphere for forming the BN layer includes nitrogen.

[0030] Unless otherwise specified, the materials and equipment used in the present invention are commercially available products.

[0031] In the present invention, the magnetron sputtering conditions for forming the BN layer preferably include: using radio frequency magnetron sputtering; using a mixed gas of argon and nitrogen as the sputtering atmosphere, with a nitrogen volume content of 20 to 30%, and in an embodiment of the present invention, it can specifically be 20%, 25% or 30%; the magnetron sputtering temperature is 100 to 180°C, and in an embodiment of the present invention, it can specifically be 100°C, 120°C, 140°C, 160°C, 170°C or 180°C.

[0032] In the present invention, when magnetron sputtering of BN is performed, the sputtering atmosphere is a mixed gas of nitrogen and argon, which can ensure stable forming of BN and the formation of hexagonal BN.

[0033] The present invention heats the substrate while coating the BN layer to ensure the formation of the desired crystalline boron nitride (hexagonal BN) and the content of the boron nitride phase; if the temperature is too low (below 100° C.), the formation rate of the hexagonal BN is low.

[0034] In the present invention, the magnetron sputtering conditions for forming the Mo layer, the C layer and the Si layer preferably include: using DC pulse magnetron sputtering with a pulse frequency of 15000 Hz; and using argon as the sputtering atmosphere.

[0035] In the present invention, the gas pressure of the magnetron sputtering is preferably 0.26 Tor; the power of the magnetron sputtering is preferably 120-350 W. In an embodiment of the present invention, it can be 120 W, 130 W, 140 W, 150 W, 160 W, 180 W, 200 W, 215 W, 220 W, 240 W, 250 W, 260 W, 280 W, 300 W, 310 W, 320 W, 330 W, 340 W or 350 W.

[0036] The present invention can control the quality of extreme ultraviolet multilayer film materials by controlling the gas pressure and power of magnetron sputtering.

[0037] After completing the magnetron sputtering, the present invention preferably further comprises annealing the obtained film material.

[0038] In the present invention, the annealing temperature is 150-180°C, and in an embodiment of the present invention, it can be specifically 150°C, 160°C, 170°C or 180°C; the annealing holding time is 8-15min, and in an embodiment of the present invention, it can be specifically 8min, 9min, 10min, 11min, 12min, 13min, 14min or 15min.

[0039] The present invention performs a short-term low-temperature (150-180°C) annealing treatment after preparation, which can eliminate stress and does not require long-term high-temperature annealing. High-temperature annealing is generally used to eliminate stress in thin films, but the consequence is that diffusion will occur between film materials under high temperature conditions, thereby changing the film structure and causing a decrease in reflectivity. After adding the intermediate layers of BN and C in the present invention, the temperature stability is good, the diffusion between the Mo layer and the Si layer is isolated, and the effect on the reflectivity is also small.

[0040] The original reflectivity of the Mo / Si multilayer film in the prior art is 68%. If it is annealed at 300°C, the reflectivity will decrease by 1% to 3%. However, the EUV multilayer film prepared by the present invention only decreases its reflectivity by 0.48% after annealing at 300°C by adding intermediate layers of BN and C.

[0041] In addition, the diameter of the extreme ultraviolet multilayer film prepared by the present invention is ≥300 mm, which is a large-size optical element.

[0042] The present invention provides the use of the extreme ultraviolet multilayer film described in the above scheme or the extreme ultraviolet multilayer film prepared by the preparation method described in the above scheme in a photolithography machine.

[0043] In order to further illustrate the present invention, an extreme ultraviolet multilayer film provided by the present invention and its preparation method and application are described in detail below in conjunction with embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0044] Example 1

[0045] Prepare the Si substrate for cleaning and drying (the sealed silicon wafer can be omitted);

[0046] Put it into the magnetron sputtering coating equipment and prepare four target materials, namely Mo, Si, B, and C;

[0047] The sputtering power of Mo is 215W, the sputtering power of Si is 260W, the sputtering power of B is 200W, and the sputtering power of C is 300W. B is sputtered by radio frequency sputtering, and other materials are sputtered by DC pulse magnetron sputtering with a pulse frequency of 15000Hz;

[0048] The magnetron coating machine is vacuumed to 1.0×10 -4 Pa high vacuum, filled with Ar gas, maintaining a sputtering pressure of 0.26 Torr;

[0049] Turn on the control switches of Ar and N gases through the program;

[0050] Run the program and enter the corresponding workflow table: switch to the working mode according to the material you are running to. Specifically, use the linear target coating method. When coating B, in addition to Ar gas, N2 gas must be flushed in to ensure that the N2 content is 20% to 30%;

[0051] When coating B, the heating system behind the substrate needs to be turned on to control the sputtering temperature to 180°C and improve the film quality of BN;

[0052] Four film materials, Mo, B, C and Si, are plated in sequence to form repeated film units on the Si substrate, each of which includes a Mo layer, a BN layer, a C layer and a Si layer stacked in sequence, and the repetition period of the film unit is 50. The uppermost material is a Si layer, so as to form a dense SiO2 layer after completion to protect the overall film performance; in each film unit, the thickness of the BN layer is 0.3nm, the thickness of the C layer is 0.2nm, the thickness of the Mo layer is 2.5nm, and the thickness of the Si layer is 4.1nm;

[0053] After the plating is completed, turn off the N gas and Ar gas, turn off the backplane heating system, and complete the film plating after natural cooling;

[0054] The obtained film is then subjected to low temperature annealing at a temperature of 180° C. for 10 min to obtain an extreme ultraviolet multilayer film.

[0055] The extreme ultraviolet multilayer film prepared in Example 1 has high reflection efficiency, and the highest peak reflectivity is ≥68%.

[0056] The extreme ultraviolet multilayer film prepared in Example 1 has good high temperature radiation resistance. After being treated at a high temperature of 300° C., the reflectivity of the film decreases by 0.48%.

[0057] The diameter of the extreme ultraviolet multilayer film prepared in Example 1 is 350 mm.

[0058] Comparative Example 1

[0059] The thickness of the BN and C layers was changed, and the other conditions were the same as those in Example 1. Specifically, in each membrane unit, the thickness of the BN layer was 0.5 nm, the thickness of the C layer was 0.5 nm, the thickness of the Mo layer was 2.5 nm, and the thickness of the Si layer was 4.1 nm;

[0060] The prepared extreme ultraviolet multilayer film has a maximum peak reflectivity of 66.2%. After high-temperature treatment at 300°C, the reflectivity of the film decreases by 1.3%.

[0061] Comparative Example 2

[0062] The sputtering pressure was changed, and the other conditions were the same as those in Example 1. Specifically, the magnetron coating machine was evacuated to 1.0×10 - 4 Pa high vacuum, filled with Ar gas, maintaining a sputtering pressure of 0.35 Torr;

[0063] The prepared extreme ultraviolet multilayer film has a maximum peak reflectivity of 67.4%. After high-temperature treatment at 300°C, the reflectivity of the film decreases by 2.41%.

[0064] Comparative Example 3

[0065] The thickness of the Mo layer and the Si layer were changed, and the other conditions were the same as those in Example 1. Specifically, in each membrane unit, the thickness of the BN layer was 0.3 nm, the thickness of the C layer was 0.2 nm, the thickness of the Mo layer was 2.3 nm, and the thickness of the Si layer was 4.3 nm;

[0066] The prepared extreme ultraviolet multilayer film has a maximum peak reflectivity of 65.2%. After high-temperature treatment at 300°C, the reflectivity of the film decreases by 1.06%.

[0067] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. People can also obtain other embodiments based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. An extreme ultraviolet multilayer film, characterized in that: It comprises repeated membrane units, each membrane unit comprises a Mo layer, a BN layer, a C layer and a Si layer stacked in sequence, and adjacent membrane units are connected by a Si layer and a Mo layer; the bottom layer of the extreme ultraviolet multilayer film is a Mo layer, and the top layer is a Si layer.

2. The extreme ultraviolet multilayer film according to claim 1, characterized in that The repetition period of the membrane unit is 40 to 60.

3. The extreme ultraviolet multilayer film according to claim 1 or 2, characterized in that: In each membrane unit, the thickness of the BN layer is 0.2-0.4 nm, the thickness of the C layer is 0.2-0.3 nm, the thickness of the Mo layer is 2.4-2.6 nm, and the thickness of the Si layer is 4.0-4.2 nm.

4. The method for preparing the extreme ultraviolet multilayer film according to any one of claims 1 to 3, characterized in that: The following steps are involved: Using a Mo target, a B target, a C target and a Si target as sputtering targets, magnetron sputtering is repeatedly performed on a substrate in sequence to form repeated film units on the substrate, each film unit comprising a Mo layer, a BN layer, a C layer and a Si layer stacked in sequence, to obtain the extreme ultraviolet multilayer film; The sputtering atmosphere for forming the BN layer includes nitrogen gas.

5. The preparation method according to claim 4, characterized in that: The magnetron sputtering conditions for forming the BN layer include: using radio frequency magnetron sputtering; using a mixed gas of argon and nitrogen as the sputtering atmosphere, with a nitrogen volume content of 20-30%; and a magnetron sputtering temperature of 100-180°C.

6. The preparation method according to claim 4, characterized in that: The magnetron sputtering conditions for forming the Mo layer, the C layer and the Si layer include: using direct current pulse magnetron sputtering with a pulse frequency of 15000 Hz; and using argon as the sputtering atmosphere.

7. The preparation method according to claim 4, 5 or 6, characterized in that: The gas pressure of the magnetron sputtering is 0.26 Tor.

8. The preparation method according to claim 4, 5 or 6, characterized in that: The power of the magnetron sputtering is 120W-350W.

9. The preparation method according to claim 4, 5 or 6, characterized in that: After the magnetron sputtering is completed, the obtained film material is annealed, the annealing temperature is 150-180° C., and the annealing holding time is 8-15 minutes.

10. Use of the EUV multilayer film according to any one of claims 1 to 3 or the EUV multilayer film prepared by the preparation method according to any one of claims 4 to 9 in a photolithography machine.