Method of reducing pattern collapse in high aspect ratio nanostructures
A method is provided for treating the surface of high aspect ratio nanostructures to help protect the delicate nanostructures during some of the rigorous processing involved in fabrication of semiconductor devices. A wafer containing high aspect ratio nanostructures is treated to make the surfaces of the nanostructures more hydrophobic. The treatment may include the application of a primer that chemically alters the surfaces of the nanostructures preventing them from getting damaged during subsequent wet clean processes. The wafer may then be further processed, for example a wet cleaning process followed by a drying process. The increased hydrophobicity of the nanostructures helps to reduce or prevent collapse of the nanostructures.
1. A method of processing a wafer used in fabricating semiconductor devices, said method comprising:
forming high aspect ratio features in a silicon based layer on the wafer, wherein the high aspect ratio features are formed utilizing a dry etching process;
making sidewalls of the high aspect ratio features more hydrophobic without needing to wet the high aspect ratio features before the making the sidewalls of the high aspect ratio features more hydrophobic, wherein the sidewalls of the high aspect ratio features are made more hydrophobic prior to performing wet processing of the high aspect ratio features of the wafer;
performing wet processing of the high aspect ratio features of the wafer; and
subsequently drying the wafer.
2. The method of claim 1 , wherein the making the sidewalls of the high aspect ratio features more hydrophobic is accomplished by depositing a primer on the wafer, wherein the primer makes the sidewalls more hydrophobic by chemically altering the surface of the high aspect ratio features.
3. The method of claim 2 , wherein the primer is deposited on the wafer by way of vapor deposition.
4. The method of claim 3 , wherein the depositing of the primer on the wafer prior to the wet processing comprises:
generating a primer solution by mixing a solution of 0.1-50% by weight of C 8 F 13 H 4 SiCl 3 (FOTS) in anhydrous n-hexane; and
co-heating a portion of the primer solution with the wafer such that the primer solution evaporates and the FOTS molecule reacts with the sidewalls of the-features.
5. The method of claim 2 , wherein the primer comprises a self-assembled monolayer.
6. The method of claim 2 , wherein the primer comprises a film, and wherein the film comprises at least one of: hexamethyldisiloxane, an alkoxysilane or an alkylsilane.
7. The method of claim 1 , wherein the making the sidewalls more hydrophobic is accomplished by roughening the sidewalls.
8. The method of claim 7 , wherein the roughening of the sidewalls is accomplished by way of exposing the wafer to at least of: polymerizing plasma, hydrogen fluoride vapor or fluoride based plasma etch.
9. The method of claim 7 , wherein the roughening of the sidewalls is accomplished by reactive-ion etching.
10. The method of claim 1 , wherein forming of the high aspect ratio features comprises:
forming a photoresist patterned mask over the silicon based layer; and
etching the high aspect ratio features into the silicon based layer.
11. The method of claim 10 , wherein the forming the high aspect ratio features further comprises stripping the photoresist patterned mask.