Patent Application
20080003521
For a more complete understanding of the present invention, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawing, in which:
The making and using of the presently preferred embodiments are discussed in detail below. It should be appreciated, however, that the present invention provides many applicable inventive concepts that can be embodied in a wide variety of specific contexts. The specific embodiments discussed are merely illustrative of specific ways to make and use the invention, and do not limit the scope of the invention.
When using immersion lithography a fluid 90 is brought in direct contact with the last lens 6 of the projection optics system 5B and the photoresist layer 50 to be patterned. This fluid 90 can, for example, comprise deionized water or other organic solvents having a high refractive index thereby reducing the fraction of radiation beams totally reflected at the interface of the last lens 6 to the fluid 90. The fluid 90 can constantly be provided and removed by a combination of a supplying system 15 applying the fluid 90 onto the photoresist layer 50 and a system 30 for removing the fluid 90.
The systems 15 and 30 can, for example, comprise showerheads or nozzles and suction pipes. The system 15 for applying the fluid 90 onto the photoresist layer 50 is further connected to a storage container 25 for storing the liquid 90. This container can be heated by a heater 20 to the desired temperature for thermally treating the exposed areas of the photoresist layer. The fluid 90 is furthermore confined by a ring 95 restricting the area of the fluid 90 to the area that is actually exposed by the device 1.
The radiation beams 40A are directed to an area 100 on the photoresist layer 50 that is exposed to the radiation and is simultaneously thermally treated using the heated fluid 90. Therefore, the process steps of exposing the photoresist layer to a radiation beam and thermally treating the exposed areas of the photoresist layer are carried out simultaneously. Afterwards the substrate 60 with the photoresist layer 50 can be moved relative to the optical lens system 5A, 5B and the mask 75 with the mask holder 70 so that different areas of the photoresist layer can be exposed to the radiation beams 40A.
An additional temperature control of the fluid 90 can be provided by enclosing the arrangement of the substrate 60 held by the substrate holder 10 and the photoresist layer 50 located on the substrate 60 in a casing 35, which is furthermore heated by a heater 45. In the case that the substrate 60 has to be kept at a temperature lower than the temperature within the heated casing 35 it might be furthermore advantageous to provide a cooling system for the substrate 60 (not shown in
The arrows in
The device 1 can furthermore comprise a computer system 80 for controlling the device. Such a computer system can for example include software for the temperature correction of the, e.g., optical lens system in order to reduce a potential negative impact of the high temperature of the fluid 90 on the exposing process.
In contrast to the device of
During such an immersion lithography process, immersion lithography can take place via exposure of the areas 100 of the photoresist layer to radiation beams 40A through the first liquid 90. This liquid 90 is preferably kept at the same temperature as the rest of the device especially the optical lens system 5. Such a configuration enables a good exposure process without major impacts of a heated fluid on the exposure process. Furthermore, this device configuration allows the process steps of exposing the photoresist layer to a radiation beam and thermally treating the exposed areas of the photoresist layer to be carried out in different steps using different fluids 90 and 91.
The second heated fluid 91 can be used to thermally treat the areas 120 of the photoresist layer 50, which were already exposed to the radiation beams 40A during an earlier exposure step. For example, a movement of the substrate 60 and the photoresist layer 50 located on the substrate 60 relative to the other components of the device 1 (indicated by the arrows) makes it possible to bring the first heated fluid 91 in contact with different areas 120, 100 of the photoresist layer.
A chemically amplified positive photoresist material is mixed containing:
93.6 g 1-methoxy-2-propylacetate as a solvent,
6.0 g of a terpolymer including 22.5 mol % tert.-butylmethacrylate, 50 mol % maleic acid anhydride, 22.5 mol % allylsilane and 5 mol % ethoxyethylmethacrylate,
0.35 g of triphenylsulfonium-hexafluoropropansulfonate as a photoacid generator, and
0.05 g trioctylamine as a basic additive.
The positive photoresist material was applied onto six silicone wafers using spin-coating (2000 rpm/20 s) and then dried on a hotplate for 90 seconds at a temperature of 140° C. The solvent evaporated resulting in a photoresist film of a thickness of 206 nm.
Subsequently the wafers with the photoresist films were exposed with a dose of, e.g., 25.3 mJ/cm2 with a deep UV mask aligner (MJB 3 of Karl Suess GmbH) using a 248 nm filter through a grey scale mask (exposure time 316 seconds).
The wafers were then developed with an aqueous alkaline developer TMA 238 WA (purchased from JSR), washed with water for 30 seconds, dried with compressed air and baked by 110° C. for 60 seconds or 5 seconds.
Afterwards the resulting photoresist patterns on each wafer were measured and “contrast curves” recorded. These curves clearly show that a post exposure bake (PEB) time of 5 seconds also should be sufficient to develop a chemically amplified resist layer. This finding clearly shows that short PEP times provided by a heated fluid are sufficient for a chemically amplified resist layer.
Variants of the method of the invention can be used to form patterns with resolutions of lower than 50 nm in the exposed photoresist layer.
The scope of the protection of the invention is not limited to the example given herein above. The invention is embodied in each novel characteristic and each combination of characteristics, which particularly includes every combination of any features that are stated in the claims, even if this feature or this combination of features is not explicitly stated in the claims or in the examples.
