Electron-beam lithography method with correction of line ends by insertion of contrast patterns

#This application is a National Stage of International patent application PCT/EP2011/055843, filed on Apr. 13, 2011, which claims priority to foreign French patent application No. FR 1052863, filed on Apr. 15, 2010, the disclosures of which are incorporated by reference in their entirety.

#The present invention applies to the domain of electron-beam lithography. To allow the etching of patterns whose critical dimension is below 50 nm, it is necessary to integrate into the methods of optical photolithography schemes for correcting the optical distortions that are increasingly complex both at the mask design and production stage and at the exposure stage. The costs of the equipment and developments for a new generation of technology consequently increase in very high proportions. Today, the critical dimensions accessible in photolithography are greater than or equal to 65 nm. The 32-45 nm generation is undergoing development and there is no viable solution envisaged for technological nodes below 22 nm. For its part, electron-beam lithography already allows the etching of 22-nm patterns; it does not require any mask and offers a fairly short development time, thus allowing better reactivity and flexibility in the realization of improvements to the technologies and to the designs. On the other hand, the production times are structurally substantially higher than in photolithography since it is necessary to carry out step-wise exposure (with a “stepper”), whereas photolithography requires only layer-wise exposure.

#The electron beam or beams used to perform the etching of a pattern scatter notably over short distance (forward scattering or blur) in the resin and the substrate on the edges of the center of the beam, thus increasing the size of the beam and reducing its contrast. Moreover, the electrons are completely backscattered over a long distance (backward scattering). In particular, the line ends within dense networks will be shortened (“line end shortening” or LES), thus affecting the functionality of the component and therefore decreasing production efficiency.

#The invention will be better understood, its various characteristics and advantages will emerge from the description which follows of several exemplary embodiments and of its appended figures wherein:

#FIG. 1 represents a view of a pattern to be reproduced and of a reproduced pattern, without correction of the LESs and with correction of the LESs in a photolithography method of the prior art;

#FIG. 2 represents a view of a pattern to be reproduced and of a reproduced pattern, without correction of the LESs and with correction of the LESs in an electron-beam lithography method of the prior art;

#FIG. 1 represents a view of a pattern to be reproduced and of a reproduced pattern, without correction of the LESs and with correction of the LESs in a photolithography method of the prior art.

#The pattern 110 to be reproduced is transferred into the resin in the form of a deformed image 120. In particular, this image comprises a line end shortening (LES), 121 and corner roundings such as 122, on account of the contrast reduction effect at the extremities of the pattern.

#The pattern 130 to be reproduced is modified by adding sub-resolved patterns such as a “hammerhead”, 131, a “serif”, 133, or one or more scattering bars, 134. The pattern can also be a subtraction of material such as a “mousebite” 132. The impact of an electron beam modulated in a particular manner with these sub-resolved patterns creates an energy distribution over the sample which improves the contrast and transfers the pattern modified by these additions and subtractions into the resin with an image, 140, identical to the initial pattern before additions/subtractions.