Formation method of semiconductor structure

Disclosed herein are improved methods of etching recesses. In some embodiments, fluorine is oxidized after dry etching of the oxide layer over the source/drain contact, prior to cleaning. Thus, less hydrofluoric acid is formed during cleaning, which reduces unexpected wet etching of the source/drain contacts. This allows a recess to be formed in the source/drain contact with a depth to width ratio ranging from about 1.0 to about 1.4, and prevents damage to the silicide layer under the source/drain that may be caused by excess hydrofluoric acid. Additionally or alternatively, the recesses are formed using multiple wet etch processes, and any fluorine residue is oxidized between the wet etch processes. Thus, the time of each wet etch can be shorter and less corrosive, which allows better control of the size of the recess. 本文公开了蚀刻凹槽的改进方法。在一些实施方式中，在干蚀刻源极/漏极接触件上方的氧化物层之后、在清洁之前，氧化氟。因此，在清洁期间形成较少的氢氟酸，这减少了源极/漏极接触件不预期的湿蚀刻。这允许在源极/漏极接触件中形成深度与宽度比在约1.0至约1.4范围的凹槽，并且防止可能由过量氢氟酸引起对源极/漏极下方的硅化物层的损坏。额外或替代地，使用多个湿蚀刻工艺形成凹槽，并且在湿蚀刻工艺之间