DE102004025837A1 - Lithographic method for manufacture of resist pattern having line roughness involves unstructured exposure of resist to light e.g. floodlight of mercury vapor lamp and heating it so that its line roughness is reduced - Google Patents

Abstract

The method involves unstructured exposure of resist pattern (1), which has line roughness, to light whose wavelength lies between 150 and 300 nm. The resist is heated on a hot plate at a temperature between 90[deg]C and 130[deg]C for 30 to 150 seconds so that its line roughness (2) is reduced. In particular, floodlight of mercury vapor lamp is used for exposure. The temperature does not exceed the glass transition temperature of the resist. The resist pattern consists of resist materials having at least one polymer or copolymer with at least an acid-unstable group.

Description

The The invention relates to a lithographic process for the production of Resist structures according to the preamble of claim 1.

In Microelectronics become so-called chemically amplified resists (CAR) as photoresists in the production of semiconductor devices used, wherein in their production preferably optical lithography method Find application.

According to the International Technology Roadmap for Semiconductors 2002 (ITRS) is the miniaturization continue to progress rapidly in microelectronics. For the production DRAMs by 2010 are likely to be resist materials be required, the structures up to a size of 45 nm dissolve can. For the year 2016 will even be the resolution 22nm DRAM (1/2-pitch) needed be. For the geometric gate lengths For microprocessors (MPU), values of 25 nm and 13 nm are expected. With the currently used exposure wavelengths of 248 or 193 nm or also in the future used wavelength of 157 nm or 193 nm (inversion), these structures can be do not produce anymore.

For mass production of structures less than or equal to 45 nm becomes optical lithography in the soft X-ray range at 13.5 nm, the extreme ultraviolet (EUV) lithography, as the most promising Lithography technology evaluated. Prerequisite for use However, the EUV lithography is that in addition to the resolution as well the line width variations are met. These fluctuations should be less than or equal to 10% of the minimum line widths, i. By 2010, the deviations should be at 4 nm for DRAM (1/2 pitch) and 2 nm for MPU gate lengths and until 2016 at 2 nm or 1 nm. The line roughness (Line Edge Roughness LER) of the resist lines may therefore per side barely half this Exceed values, i.e. about 0.5 nm to 2 nm. Present but only line roughness of about 6 nm to 10 nm can be achieved. Therefore, it is necessary to reduce the line roughness by about one Magnitude until 2016.

to Minimizing the line roughness of resists are different activities known. So can the line roughness of the photomasks used e.g. through high-resolution Electron beam writing and anisotropic etching processes, the resist structures preferably maßgetreu transferred to the mask, be minimized. Further approaches offer the optimization of the imaging performance of the projection optics, e.g. through a high resolution, or the development of resists with the lowest possible contribution to Line roughness, e.g. Use of small linear or annular molecular members in the base polymers. About that In addition, special etching processes for hard masks and the underlying layers have been developed, the Line roughness of the resist lines reduced to the hard mask and transfer the underlying layer becomes.

The All of the methods described are related to minimizing the Line roughness through measures, the lithographic process, e.g. Improvement of the masks, or the material used, e.g. Photoresists, in themselves. A u.U. remaining line roughness can then no longer positively influenced.

Of the The present invention is therefore based on the object, a method to develop in which the line roughness of resist structures also reduced after the lithographic production of these structures becomes.

These The object is achieved by a Method solved with the features of claim 1.

The Inventive lithographic process for producing at least one resist pattern with a line roughness is characterized in that after lithographic production at least one resist structure, this resist structure of an unstructured Exposure and heating is exposed, whereby the line roughness is reduced.

With Advantage becomes the unstructured exposure of the resist structure, Light with a wavelength of 150 used to 300 nm.

there is advantageously flood exposure for unstructured exposing applied. For the flood exposure does not necessarily have to use the same wavelength which is used in lithographic structuring. Advantageous are such wavelengths, with which the resist material is not due to the absorption overexposed, as only molecules on the surface have to be modified

Advantageously, the exposure dose is 1 to 20 mJ / cm ² .

The subsequent heating to the unstructured exposure (baking) of the resist structures is advantageously carried out at temperatures which are not higher than the glass transition temperature T _{G of} the polymer. The preferred temperature range is between 90 ° C and 130 ° C.

advantageously, the baking step is carried out on a hotplate.

The Resist materials used are chemically amplified resists (CAR). The resist material advantageously consists of at least one Polymer or copolymer with at least one acid-labile group.

By the advantageous addition of at least one photoacid generator as a chemical reinforcing agent, let yourself improve the sensitivity of the resist system.

The Invention will be described below with reference to the figures of Drawings on an exemplary embodiments explained in more detail. It demonstrate:

1A a resist structure ( 1 ) on a substrate ( 10 ), and after the patterned exposure and development, a line roughness ( 2 ) having;

1B 3 is a schematic representation of the unstructured exposure hν of the resist structure (FIG. 1 ) from the photoacid generators (PAGs) released strong acids ( 3 )

1C a schematic representation of the smoothing of the edges after a thermal treatment step Δ.

During the first lithographic process, the process of the invention preceded by the resist material added PAGs form after structured exposure using a mask strong acids that in the subsequent baking step, the acid-labile groups in the polymers columns. Due to the formed carboxylic acids is the targeted exposed Resist more polar and is soluble in an alkaline developer. The remaining, unexposed resist structures are still hydrophobic.

In the subsequent process according to the invention, the unexposed resist structures ( 1 ), which are preferably located on a substrate ( 10 ) and a line roughness ( 2 ) exhibit ( 1A ), exposed. Through the unstructured exposure of these hydrophobic resist structures ( 1 ) are also in this area strong acids ( 3 ) are formed from the PAGs, which in turn generate polar acid groups in the polymers ( 1B ). In conjunction with a subsequent baking step, the surface energy W _{OB increases} and the system tends to reduce surface roughness. The maps become smoother ( 1C ).

materials with high surface tensions especially strive for as possible small surfaces, to minimize the energy. Typical surface tensions are in the range from 100 mN / m to 2000 mN / m for Metals and ionic crystals and reach up to 17 mN / m for fluorocarbons. Resists, which preferably consist of polymers, typically have a surface tension of about 22 mN / m. In contrast, the surface tension of polymers with a big one Number of polar groups in the range of about 35 mN / m, which is a increase the surface energy means about 50%.

The present invention relating to lithographic patterning connects, added thus other measures for reducing the line roughness.

The Restricted invention in their execution not to the preferred embodiments given above. Rather, a number of variants are conceivable that of the lithographic process according to the invention also in principle different types Make use.

1

resist structure

2

Linienrauhigkeit

3

education a strong acid after exposure

10

substratum

Claims (9)

Lithographic process for the production of at least one resist structure, wherein this has a line roughness, characterized in that after the lithographic production of at least one resist structure ( 1 ) by a) unstructured exposure of the resist structure ( 1 ) and b) heating the resist structure ( 1 ) the line roughness ( 2 ) is reduced. Lithographic process according to claim 1, characterized in that for the unstructured exposure of the resist structure ( 1 ) Light with a wavelength in the range between 150 and 300 nm is used. Lithographic process according to claims 1 and 2, characterized in that for the unstructured exposure of the resist structure ( 1 ) preferably flood light, in particular flood light of a mercury vapor lamp is used. Lithographic process after at least one of the preceding claims, characterized in that the resist structure ( 1 ) is exposed unstructured at a dose of 1 to 20 mJ / cm ² . Lithographic process according to at least one of the preceding claims, characterized in that the heating of at least one resist structure ( 1 ) is carried out at temperatures not higher than the glass transition temperature T _{G of} the resist structure ( 1 ), preferably at temperatures between 90 ° C and 130 ° C. Lithographic process according to at least one of the preceding claims, characterized in that the heating of the resist structure ( 1 ) on a hotplate. Lithographic process according to at least one of the preceding claims, characterized in that the resist structure ( 1 ) is baked for 30 to 150 seconds. Lithographic process according to at least one of the preceding claims, characterized in that the resist structure ( 1 ) consists of resist materials comprising at least one polymer or copolymer having at least one acid labile group. Lithographic process according to at least one of previous claims, characterized in that as a chemical reinforcing agent in the resist materials at least one photoacid generator is used.