Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Making electrical device
Patent
1997-03-12
1998-12-22
Baxter, Janet C.
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Making electrical device
4302701, 430326, 430919, 430330, B03C 500
Patent
active
058517332
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a method for producing photolithographic patterns--using a dry developable single-layer resist system--in the submicron range.
"Chemically amplified resists" are widely used in microelectronics (see "Solid State Technology", vol. 34 (1991), no. 8, pp. 53 to 60). The chemical amplification is performed both when working with wet-developable single-layer resists, as well as with wholly or partially dry-developable resists. The resists are able to work in accordance with the principle of cleavage by acid catalysis, polar, but blocked chemical groups, such as carboxyl groups or phenolic hydroxyl groups being deblocked by a photolytically produced acid, and the resist undergoing a polarity change in the exposed regions. This polarity change can be used for a selective silylation when working with dry-developable resists, for example. Examples of blocking groups are tert. butylester and tert. butoxy-carbonyloxy groups.
Published European Patent application 0 492 256 discloses a photolithographic pattern generation, where a dry-developable resist is subjected to a temperature treatment following irradiation (post exposure bake=PEB) and is then silylated from the liquid phase and subsequently anisotropically etched in an oxygen plasma. Positive or negative patterns are produced depending on the type of silylation solution. The resist is generally comprised of at least two solid constituents, i.e., of a base polymer and a photoactive acid former. The base polymer contains carboxylic acid anhydride and tert. butylester partial structures, the acid former is preferably an onium compound, such as diphenyliodonium- and triphenylsulfonium-trifluoromethanesulfonate. A resist of this type is especially suited for photopatterning in the sub-micron and subhalf-micron range with very steep side walls. In a pattern generation carried out in the manner described above, the so-called "delay time" effect was ascertained--in the same way as in other known resist systems which work according to the principle of acid-catalyzed cleavage. Namely, if the delay time between exposure and temperature treatment (PEB) exceeds a certain value, considerable discrepancies occur between the nominal pattern dimension (pattern size on the mask) and the imaged pattern (pattern size in the resist following development). The longer this delay time is, the greater the discrepancy. Above a certain value for the time delay, for example about 30 minutes, in the case of anhydride group-containing resists of the type mentioned above, almost no patterns are recognizable after development. The tolerable delay time for these resists is approximately 5 to 10 minutes. From a standpoint of production engineering, however, a delay time of this kind is not acceptable.
The problem portrayed here is generally known and is attributed to alkaline contamination in the air, which deactivates the photochemically produced strong acid during the delay time. It has already been proposed, therefore, to solve this problem by filtering the air using activated carbon (see: "Proc. SPIE", vol. 1466 (1991), pp. 2-12). However, this requires considerable investment.
Other measures, such as admixing additives, also have not resulted in a decisive attenuation of the delay time effect (see: "Proc. SPIE", vol. 1466 (1991), pp. 13-25). The delay time can, in fact, be prolonged by applying an additional layer, but only to a minor extent. Moreover, such a measure constitutes an additional process step, which is not desirable in a production because it leads to loss of efficiency.
The object of the invention is to disclose a method that operates on the principle of acid-catalyzed cleavage--for photolithographic pattern generation, which--when working with resist systems of the type mentioned at the outset--will enable the delay time problem to be solved without entailing additional process steps or investments; i.e., the delay time between irradiation and temperature treatment (of a value of approx. 10 minutes) to be increased to a level that is acceptable in ter
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Leuschner Rainer
Schmidt Erwin
Sezi Recai
Ashton Rosemary
Baxter Janet C.
Siemens Aktiengesellschaft
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