The method that is used for field separated etching
Technical field
The present invention relates to a kind of manufacture method of semiconductor integrated circuit, relate in particular to a kind of method that is used for field separated etching.
Background technology
The method of carrying out field separated etching at present mainly comprises two steps: hf etching step and dry method etching polysilicon step.Because the hydrophobic nature on polycrystalline silicon material surface, make the silicide that in the process of carrying out the hf etching step, generates can be dissolved in the water and remain in polysilicon surface, treat the water drying after, silicide can remain in polysilicon surface and form the water mark.Residual have the water mark of silicide can become mask and then hinder follow-up dry method etching polysilicon step, forms residual polycrystalline silicon at polysilicon surface, has a strong impact on the quality of product.
Summary of the invention
The technical problem to be solved in the present invention provides a kind of residual field separated etching method of silicide behind the hf etching of eliminating.
For solving the problems of the technologies described above, the invention provides a kind of method that is used for field separated etching, be made up of a hf etching step and a dry method etching polysilicon step, it increases by an acid ﹠ alkali liquid and cleans step after the hf etching step, before the dry method etching polysilicon step.
The present invention is because after the hf etching step, increased by an acid ﹠ alkali liquid before the dry method etching polysilicon step and cleaned step, thereby removed after the hf etching step normal because the hydrophobicity of polycrystalline silicon material and residual silicide water mark, improved the quality of follow-up dry method etching polysilicon.
Embodiment
Below the present invention is further detailed explanation.
A kind of method that is used for field separated etching of the present invention, on the basis that only comprises a hf etching step and a dry method etching polysilicon step of prior art, after the hf etching step, before the dry method etching polysilicon step, increase by an acid ﹠ alkali liquid and clean step.Described acid ﹠ alkali liquid is cleaned step and is made up of following step: at first, will be soaked in through the polycrystalline silicon material of hf etching in the groove that is added with alkali lye, and soak and took out afterwards in 5 minutes; Again the polycrystalline silicon material that takes out is soaked in the groove that is added with acid solution, soaks equally and took out afterwards in 5 minutes; Polycrystalline silicon material after the taking-up washes one time with plasma water; Be positioned in the rotary drier and carried out drying in 5 minutes with the rotation of 800rpm rotating speed.
It is the mixed liquor of ammoniacal liquor and hydrogen peroxide that the present invention cleans the alkali lye that is adopted in the step at acid ﹠ alkali liquid, and wherein, the component volume ratio of mixed liquor is:
Ammoniacal liquor: hydrogen peroxide: water=1: 2~10: 15~30.
It is the mixed liquor of sulfuric acid and hydrogen peroxide that the present invention cleans the acid solution that is adopted in the step at acid ﹠ alkali liquid, and wherein, the component volume ratio of mixed liquor is:
Sulfuric acid: hydrogen peroxide=2~10: 1.