CS214435B1 - Method of production of a series of diffraction gratings with sinusoidal relief in positive SCR 11 photoresist with reproducible parameters - Google Patents

Abstract

The invention relates to a method for producing a series of diffraction gratings with a sinusoidal relief in positive photoresist SCR 11 with reproducible parameters. The gratings produced according to this method have parameters within the desired tolerances for use in spectroscopic applications. The geometric dimension of the grating can be up to several tens of cm^. The maximum value of diffraction efficiency is 30 to 33%.

Description

The invention relates to a method for producing a series of sinusoidal relief relief grids in a positive photoresist SCR 11 with reproducible parameters.

High quality diffraction gratings are not only desirable in spectroscopic applications, but also in voptoelectronics, in control, measurement and automation technology.

The high accuracy of diffraction gratings is based on the production of replicas from the first fabricated grid pattern, whether mechanically engraved on the engraving machine or realized by recording interference strips in the photosensitive layer. The replicas are made in a gelatinous layer. The disadvantage of the replicas formed in the gelatin layer is the relatively low time stability of these lattices, the dehydration causes the layer to shrink and thereby to change important lattice parameters.

Because in diffraction gratings, especially for spectroscopic applications and in optoelectronics, the micrometer order period or even several times lower, the technological process of replicas is very demanding if the parameters within the required tolerances (spatial frequency, diffraction efficiency, low scattering) are to be observed.

It takes up to a week to produce an engraved diffraction grating with a surface area of several tens of centimeters with a period of about 1 / am and therefore new materials and technological methods for producing replicas from the first engraved sample are sought and investigated.

New possibilities arise when realizing diffraction gratings by recording interference strips in photoresists. The time required to produce grids is of the order of only a few tens of minutes and, most importantly, this time is not dependent on the size and period of the grid.

Each grid is original. This means, however, that the essential parameters of the produced grids (geometric dimension, spatial frequencies, scattering, diffraction efficiency) must be reproducible within the required tolerances. The greatest difficulty is with respect to the maximum diffraction efficiency, for which a maximum change of up to 10% is permissible. This demanding parameter is practically impossible to observe in all manufactured grids, as there are many phenomena in the complex technological process that affect the amplitude of the sinusoidal relief and hence the diffraction efficiency. It is mainly the history of the photoresist layer, the variation in laser power during exposure, the change in developer temperature, and the inaccuracy in keeping the sample development time in the developer.

The above-mentioned disadvantages do not have the method of producing a series of diffraction gratings with sinusoidal relief in the positive photoresist SCR 11 with reproducible parameters according to the invention, which consists in that the amplitude of sinusoidal relief is maximally 50% greater than optimal. and a heat treatment mode in the range of 20 to 130 ° C and a shortening time of up to 60 minutes, preferably 30 minutes, to reduce the amplitude of the relief to an optimum value are determined for the grid.

The advantage of this method is that each manufactured grid has reproducible parameters, geometric dimension, spatial frequency, low scattering, but also diffraction efficiency, with a maximum value of 30% to 33%.

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Fig. 1 shows the dependence of the relative reduction in the amplitude of the sine relief of the grids on the heat treatment temperature, the heat treatment time being 30 minutes.

The object of the invention was verified on two series of diffraction gratings in a positive photoresist SCR 11 and a spatial frequency of 600 Sar / mm.

FIG. 2 is a graphical representation of diffraction efficiencies for a wavelength of 254 nm at heat treatment temperature for various initial, initial sinusoidal relief amplitudes. It can be seen from FIG. 2 that the relief amplitude can be reduced by up to 650%, in a particular case, from 54 nm to 36 nm, for which the diffraction efficiency has a maximum value of 33%.

Claims (1)

A method for producing a series of diffraction gratings with sinusoidal relief in a positive photoresist SCR 11 with reproducible parameters, characterized in that a sinusoidal relief amplitude of not more than 50% greater than optimal is generated, determining the actual amplitude from the diffraction efficiency measurement as a function of wavelength; provides for a heat treatment mode in the range of 20 to 130 ° C and a treatment time of up to 60 minutes, preferably 30 minutes, to reduce the relief amplitude to an optimum value.