Method to improve mechanical strength of low-k dielectric film using modulated UV exposure

#This application is related to U.S. patent application Ser. No. 10/800,377, filed on Mar. 11, 2004, titled “Method and Apparatus for UV Exposure of Porous Low-k Films for Porogen Removal and Film Hardening,” by Cho et al; U.S. patent application Ser. No. 10/807,680, filed on Mar. 23, 2004, titled “Methods of Porogen Removal for Porous Low Dielectric Constant Films Using Plasma Treatments,” by Wu et al.; U.S. patent application Ser. No. 10/672,311, filed on Sep. 26, 2003, titled “Method of Porogen Removal from Porous Low-k Films Using UV Radiation,” by Tipton et al.; and U.S. patent application Ser. No. 10/404,693, filed on Mar. 31, 2003, titled “Method for Forming Porous Films by Porogen Removal Combined with In Situ Surface Modification,” by Humayun et al., each of which is incorporated herein by reference in its entirety for all purposes.

#This invention relates to methods and apparatus for preparing dielectric films for integrated circuits, particularly carbon-doped oxide (CDO) dielectric films. More specifically, the invention employs modulated ultraviolet radiation to increase the hardness and modulus of the film. In preferred embodiments, the film shrinkage and dielectric constant are minimally affected.

#Modern integrated circuit manufacturing requires advanced techniques for creating materials having low dielectric constants (low-k materials). Using low-k materials as the inter-metal and/or inter-layer dielectric in integrated circuits reduces the delay in signal propagation due to capacitive effects. The lower the dielectric constant of the dielectric film, the lower the capacitance of the dielectric and the lower the RC delay of the integrated circuit (IC).

#The following detailed description can be more fully understood when considered in conjunction with the drawings in which:

#FIG. 1 is a flowchart summarizing stages of example implementations of the invention.

#FIG. 2 is a chart representing an example of modulated UV exposure as a function of time in accordance with the invention.

#The Dielectric Film

#In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, which pertains to improving the mechanical strength of a low-k dielectric film by way of modulated UV exposure. The present invention may be practiced without some or all of these specific details. In other instances, well known process operations have not been described in detail to not unnecessarily obscure the present invention. While the invention will be described in conjunction with the specific embodiments, it will be understood that it is not intended to limit the invention to the embodiments.

#The present invention improves the dielectric film's mechanical properties with relatively minimal increase of k value and minimal film shrinkage. As used herein “semiconductor substrates” include any semiconductor substrate at any of the various states of manufacture/fabrication in the production of integrated circuits. Thus, the concept of a semiconductor substrate includes whole wafers and dies, partially fabricated integrated circuits and completely fabricated integrated circuits, whether or not packaged, and the like.