在制造过程中去除氮化硅和其他材料的方法

Methods for removing silicon nitride and elemental silicon  during contact preclean process involve converting these  materials to materials that are more readily etched by fluo  ride-based etching methods, and Subsequently removing the  converted materials by a fluoride-based etch. Specifically,  silicon nitride and elemental silicon may be treated with an  oxidizing agent, e.g., with an oxygen-containing gas in a  plasma, or with O. or Os in the absence of plasma to produce  a material that is more rich in Si-O bonds and is more easily etched with a fluoride-based etch. Alternatively, silicon  nitride or elemental silicon may be doped with a number of  doping elements, e.g., hydrogen, to form materials which are  more easily etched by fluoride based etches. The methods are  particularly useful for pre-cleaning contact vias residing in a  layer of silicon oxide based material because they minimize  the unwanted increase of critical dimension of contact vias.

This application claims priority under 35 USC 119(e) from  U.S. Provisional Patent Application No. 60/905,782 naming  Liu et al. as inventors, titled “Methods of Removing Silicon  Nitride and Other Materials during Fabrication of Contacts  and Interconnects' filed Mar. 7, 2007, which is herein incor  porated by reference in its entirety and for all purposes. This  application is related to U.S. patent application Ser. No.  1 1/479,812 filed Jun. 30, 2006, naming Liu et al. as inventors,  titled Adsorption Based Material Removal Process', which  is incorporated herein by reference in its entirety and for all  purposes. This application is also related to U.S. patent appli  cation Ser. No. 12/002,085 filed Dec. 13, 2007, naming Liu et  al. as inventors, titled “Modulating Etch Selectivity and Etch  Rate of Silicon Nitride thin Films', which is incorporated herein by reference in its entirety and for all purposes.

The present invention pertains to methods of removing  layers of material on a partially fabricated integrated circuit.  Specifically, the invention pertains to methods for removing  silicon nitride and other materials during fabrication of con  tacts and interconnects.

In a typical integrated circuit manufacturing process flow,  metal is deposited onto a patterned dielectric (typically a 35  silicon dioxide based material) to fill the vias and trenches  formed in the dielectric layer. The resulting metallization  layer is typically formed either directly on a layer carrying  active devices (e.g., transistors), or on another metallization  layer. The resulting metal-filled vias and trenches form the 40  conductive pathways of an integrated circuit (IC) device.  Contacts and interconnects are formed between active  devices and metal-filled vias as well as between metal lines of  adjacent metallization layers.

Fig1

Removal of silicon nitride presents several challenges,  which become more pronounced as the dimensions of  recessed features in IC devices continue to shrink. Silicon  nitride is often more resistant to fluoride-based etching than  the surrounding silicon dioxide based ILD, and therefore  often requires more aggressive etching conditions. Removal  of even very small amounts of etch-resistant silicon nitride  from the contacts and interconnects, can inadvertently result  in etching of Substantial amounts of silicon dioxide based  ILD material, which defines the dimensions of recessed fea  tures on a partially fabricated IC device. While such inadvert  ent etching may be tolerated in Some device structures with  relatively large dimensions of recesses, in those structures  where dimensions are small, fluoride-based etching of etch  resistant silicon nitride may lead to Substantial increase in  critical dimensions of vias and trenches defining the contacts.  Such increase in critical dimensions is highly undesired, and  should be avoided when possible.