Method for correcting electronic proximity effects using the deconvolution of the pattern to be exposed by means of a probabilistic method
View Patent ↗A method of lithography by radiation having critical dimensions of the order of some ten nanometers makes it possible to carry out the correction of the proximity effects by joint optimization of the dose modulation and geometric corrections. Accordingly, a deconvolution of the pattern to be etched is carried out by an iterative procedure modeling the interactions of the radiation with the resined support by a joint probability distribution. Advantageously, when the support exposure tool is of formed-beam type, the pattern to be etched is split into contrasted levels and then the deconvolved image is vectorized and fractured before carrying out the exposure step. In an advantageous embodiment, the method is applied to at least two character cells which are exposed in a multi-pass cells projection method.
1. A method of lithography by radiation of at least one pattern to be irradiated on a resined support comprising:
generating, using a computer processor, a chosen point spread function for said radiation, and
applying, using the computer processor, a chosen deconvolution procedure to said pattern to be irradiated by said point spread function,
wherein said point spread function is chosen so as to model only the effects of forward scattering of said radiation and said deconvolution procedure is chosen from among the procedures modeling the interactions of said radiation with the resined support by a joint probability distribution of said interactions, wherein the joint probability distribution of said interactions is associated with a maximum likelihood of each source point of said radiation for all the image points of the pattern to be irradiated as part of the interactions.
2. The method of lithography of claim 1 , wherein said deconvolution procedure comprises computing the maximum likelihood of each source point of said radiation for all the image points of the pattern to be irradiated, each image point being multiplied by the value of the point spread function between the source point and the image point.
3. The method of lithography of claim 2 , wherein said deconvolution procedure is a Lucy-Richardson procedure.
4. The method of lithography of claim 1 , further comprising dithering the deconvolved image of the pattern to be irradiated.
5. The method of lithography of claim 1 , further comprising splitting the deconvolved image into at least two distinct exposure levels.
6. The method of lithography of claim 5 , wherein the at least two distinct exposure levels are chosen so as to maximize the population in terms of pixels of each of the levels.
7. The method of lithography of claim 5 , further comprising vectorizing the deconvolved image of the pattern to be irradiated.
8. The method of lithography of claim 1 , wherein the point spread function is a Gaussian.
9. The method of lithography of claim 8 , wherein the mid-height width of the Gaussian is between 3 nm and 15 nm.
10. A computer program comprising program code instructions allowing, when the program is executed on a computer, the execution of the method of lithography by radiation of claim 1 , said program comprising a function for generating a chosen point spread function for said radiation and a module for applying a chosen deconvolution procedure to the optionally filtered outputs of said radiation points spreading function applied to said pattern to be irradiated, wherein said point spread function is chosen so as to model only the effects of forward scattering of said radiation and said deconvolution procedure is chosen from among the procedures modeling the interactions of the points of said radiation by a joint probability distribution of said interactions.
11. The computer program of claim 10 , further comprising an interface window in which an operator can program the application to at least one second pattern belonging to a determined class of correction rules determined by deconvolution of a first pattern belonging to said class.