DE3036710A1 - Photolacquer structure with photoresist layer - is on deep UV or electron positive resist - Google Patents

Abstract

The photolacquer structure is produced by irradiating photoresist on a substrate using actinic radiation. A layer that may be degraded by energetic radiation or by a dry etching process is formed on the substrate and the photoresist layer is formed on top of it. The degradable layer contains compounds that absorb UV and/or visible light. The degradable layer may be an electron positive resist or a deep UV resist and is thicker than the photoresist layer. The advantage lies in avoiding interference whilst at the same time maintaining good resolution factors.

Description

Process for the production of photoresist structures

The invention relates to a method for producing photoresist structures by irradiating a photoresist located on a substrate with actinic Light.

The photoresist technology is one of the most precise methods for structuring the surfaces of metals, semiconductors and insulators. The ones used light-sensitive lacquers, the photoresists, are film-forming materials, their Solubility changes greatly after exposure to actinic light.

With the so-called positive resists, the lacquer film is after exposure soluble. When using such resists, therefore, the photoresist or Relief structures are created in such a way that those areas of the lacquer film are exposed to be removed. When developing the areas exposed The exposed areas are then peeled off. With negative working Photoresist systems, the so-called negative resists, are the lacquer film after exposure insoluble, i.e. (only) the unexposed parts of the film become during subsequent development detached.

In order to have narrow tolerances of the lateral dimensions when creating the relief structure to adhere to the paint structures, it is necessary that the light intensity in is as similar as possible to the exposed areas, i.e. one fluctuation the intensity within the exposed areas or from an exposed area on the other hand is undesirable. When using positive resists, for example namely, a larger intensity leads to smaller dimensions after development of the photoresist structures.

The light intensity "coupled" into the photoresist layer during exposure can now fluctuate locally, even if it affects the areas to be exposed incident light intensity is the same across all these areas. root cause for this different coupling are interference effects that occur during exposure are particularly pronounced with monochromatic light. It has shown, that even small fluctuations in the paint thickness (approx. 50 nm) lead to fluctuations in intensity up to a factor of 2. Incidentally, the interference effects are not only annoying because they lead to fluctuations in the paint line widths, but also because Newtonian interferes with adjustment in the visible wavelength range Interference fringes occur, which impair the detection of structure edges (See: "Siemens Research and Development Reports", Vol. 3 (1974), pages 390 to 393).

In the case of a lacquer layer arranged on a substrate, different intensities are coupled into the lacquer layer depending on the phase position between the incident and the reflected light waves. The maximum coupling occurs when the phases are identical. This is the case when the paint thickness dL meets the condition where m = 1, 2, 3, 4 ... and XL is the exposure wavelength in the photoresist; where: LLL = XV / nLS where lv is the light wavelength in a vacuum and nL is the refractive index of the photoresist.

The effect of different intensity coupling in the photoresist can by exposure to broadband light or by exposure to several Wavelengths are reduced. In addition, it is known that the less the effect the less reflective the substrate, the thicker the lacquer layer and the more the paint layer absorbs the light.

However, the measures mentioned have various disadvantages. The resolution depends on the thickness of the lacquer layer, i.e. the thicker it is the lacquer layer, the lower the resolution. On the other hand works the exposure is all the more different on the upper and lower areas of the Lacquer layer from, the stronger the absorption capacity is; but one is strived for uniform change in the properties of the irradiated layer section. The usage of broadband light or

of light with multiple wavelengths ultimately requires an increased technical effort.

The object of the invention is to provide a method that the generation of true-to-size photoresist structures allowed. In particular, undesired interference effects should can be avoided without other disadvantages, such as reduced resolution, must be accepted.

This is achieved according to the invention in that on the substrate a layer degradable by high-energy radiation or by dry etching processes and a layer of the photoresist is applied thereon.

With the term "high-energy radiation" in the context of the present Patent application designates the following types of radiation: short-wave W (Deep-W) and ion radiation. The "dry etching process" includes processes such as plasma etching, reactive ion etching and Understand sputtering. Finally, the term "degradable" means that the chain is shortened of the polymer molecules occurs as a result of bond breaks.

In the method according to the invention, the upper of the two places on the The layers applied to the substrate represent the actual photoresist layer. This layer is exposed in areas using known mask exposure techniques, and although with UV and / or visible light, and then it is developed, with the soluble parts of the layer are dissolved out. Those educated in this way Lacquer mask, ie. the photoresist layer, subregions of the lower ones that are no longer covered The layers are subsequently created using high-energy radiation or dry etching processes reduced. If necessary, this can be followed by a solvent developer process.

In the method according to the invention, the photoresist layer has due the existence of two layers - even at levels - i.e. differences in height Substrates have a uniform thickness. In this procedure, the lower causes Layer also has a much more homogeneous distribution of the substrate backscattered Light than is otherwise the case.

'Advantageously, in the method according to the invention, the lower, i. the degradable layer contain compounds that absorb UV and / or visible light; the absorption should be particularly in the wavelength range between approximately 300 and 600 nm, preferably between about 350 and 450 nm. With such a Measure prevents the lower layer from backscattering during irradiation of the upper (photoresist) layer impinging on the lower layer.

As UV and / or visible light absorbing additives to the lower Layer, for example, the following connections or connection classes are suitable: Benzophenone derivatives, azobenzenes, quinones, fluors # none, fulvenes, dienones, cinnamic acid derivatives, Salicylates, polyenes, such as cyanines, polymethines, polyenaldehydes, polyenoic acids, polyenketones and carotenes, polyannelated aromatics, non-alternating hydrocarbons, heteroaromatics, such as benzotriazoles, methyl orange, anthraquinone dyes, such as alizarine, as well as azo, Azine, acridine, oxazine, thiazine and triarylmethane dyes. To be favoured such additives are used that resist irradiation with UV and / or visible Are light stable, such as salicylates, polyannelated aromatics, heteroaromatics, anthraquinones and Alizarine.

In the method according to the invention, both positive as well as negative photoresists can be used. Are particularly suitable the positive resists based on novolaks and diazoquinones as well as based on polyvinyl cinnamate or on the basis of cyclized Negative resists based on polyisoprenes and diazide compounds.

Deep-W or electron positive resists are preferably found in the degradable layer Use. Resists of this type have the advantage that they can be produced by dry etching processes are particularly easily degradable or easily volatilized. Suitable electron positive resists are for example: polyolefin sulfones, such as polybutene-1 sulfone and cyclic polyolefin sulfones, Polystyrene sulfones, polyalkyl methacrylates, especially polymethyl methacrylate (PMMA) and copolymers of methyl methacrylate with ck -chloro- or cL-cyano-acrylates resp.

with methacrylonitrile, pre-crosslinked PMMA types made from methyl methacrylate copolymers with methacrylic acid and methacrylic acid chloride or methacrylic acid, pre-crosslinked polymethacrylamide, Polymethacrylate with fluorinated ester component, polybenzyl methacrylate, polymethyl isopropenyl ketone, Polyisobttylene and its copolymers and # -Cyanoäthylacrylat- i -amidoethyl acrylate copolymers.

It is also advantageous in the method according to the invention if the degradable layer has a greater thickness than the (actual) photoresist layer. The leveling effect of the degradable layer which applies to the resist layer is namely the thicker the degradable layer, the more effective it is.

The invention is to be explained in greater detail on the basis of exemplary embodiments word # n.

Example 1 On a 3 "wafer with different structure heights has, is used for planarization from a victorious PMNA solution, which ß-carotene contains dissolved, a 1.5 / µm thick film is produced by means of "spin-coating". On this The first layer is dried for 45 minutes at approx. 1000C using the same centrifugal technique, starting from a commercially available positive photoresist solution based on novolaks and diazoquinones CAZ 1350 J) an OJ5 / µm thick photoresist layer is produced and at dried at approx. 90 ° C. Thereafter, the photoresist layer is made using known photolithography methods structured, i.e. using a photomask in the range from 350 to 450 nm irradiated and subsequently developed in an aqueous-alkaline manner. The exposed areas the lower layer of lacquer are then applied using a Plasjna plate reactor with an oxygen partial pressure of 0.7 mbar with an energy of 1000 W true to size, i.e. removed without undercutting the resist mask structures.

Example 2 Following the manner described in Example 1, a different Wafers with structural heights are provided with a double layer of lacquer the photoresist layer is structured in the manner described, one being the substrate adapted deep UV lacquer mask is obtained. This lacquer mask is the one underneath located PMMA layer, which is sensitive in the range around 220 nm, with a low-pressure mercury lamp irradiated. The irradiated areas are then treated with a methyl isobutyl ketone / ethanol developer mixture detached.

4 claims

Claims (4)

Claims method for producing photoresist structures by Irradiating a photoresist located on a substrate with actinic light, d a -d u r c h e k e n n n z e i c h n e t that on the substrate a through high-energy Radiation or a layer degradable by dry etching processes and a layer on top des Photores: sts is applied. 2. The method of claim 1, d a d u r c h g e -k e n n z e i c That is, the degradable layer is W and / or visible light absorbing compounds contains. 3. The method according to claim 1 or 2, d a d u r c h g e k e n n z It is true that a deep-W or electron positive resist is used as the degradable layer is used. 4. The method according to any one of claims 1 to 3, d a -d u r c h g e it is not noted that the degradable layer has a greater thickness than the photoresist layer.