Method of controlling CD bias and CD microloading by changing the ceiling-to-wafer gap in a plasma reactor
OwnerRodolfo P. Belen, Edward P. Hammond, IV +4inventors
InventorsRodolfo P. Belen, Edward P. Hammond, IV, Dan Katz, Valentin N. Todorow, Brian K. Hatcher, Alexander M. Paterson
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Abstract
In a plasma etch process, critical dimension (CD), CD bias and CD bias microloading are controlled independently of plasma process conditions or parameters, such as RF power levels, pressure and gas flow rate, by depressing or elevating the workpiece support pedestal to vary the gap between the workpiece and the chamber ceiling facing the workpiece, using an axially adjustable workpiece support.
Claims20
A method for performing a plasma etch process on a production workpiece in a reactor chamber having a ceiling overlying a workpiece support surface, comprising:
- providing an adjustable workpiece-to-ceiling gap between said workpiece support surface and said ceiling;
- performing successive plasma etch processes on successive test workpieces under identical process conditions at different successive values of said gap;
- measuring a critical dimension (CD) bias as a pre-etch to post-etch change in a critical dimension (CD) for isolated features and for dense features on each of said test workpieces and correlating each CD bias with the corresponding workpiece-to-ceiling gap to produce correlated measurements;
- searching said correlated measurements for:
- (1) a first value of said gap at which CD bias of the isolated features exceeds that of the dense features, and (2) a second value of said gap at which CD bias of the dense features exceeds that of the isolated features;
- and
- placing the production workpiece in said reactor, setting said gap to an intermediate value lying between said first and second gap values and performing an etch process while maintaining said process parameters at said same set of corresponding parameter values.
A method for performing a plasma etch process on a production workpiece in a reactor chamber having a ceiling overlying a workpiece support surface, comprising:
- providing an adjustable workpiece-to-ceiling gap between said workpiece support surface and said ceiling;
- performing successive plasma etch processes on successive test workpieces under identical process conditions at different successive values of said gap;
- measuring a critical dimension (CD) bias as a pre-etch to post-etch change in a critical dimension (CD) and correlating each CD bias with the corresponding workpiece-to-ceiling gap to produce correlated measurements;
- searching said correlated measurements for an optimum value of said gap at which CD bias is less than a predetermined value of CD bias;
- and
- placing the production workpiece in said reactor, setting said gap to said optimum value and performing an etch process while maintaining said process parameters at said same set of corresponding parameter values.
A method for performing a plasma etch process on a production workpiece in a reactor chamber having a ceiling overlying a workpiece support surface, comprising:
- providing an adjustable workpiece-to-ceiling gap between said workpiece support surface and said ceiling;
- performing successive plasma etch processes on successive test workpieces under identical process conditions at different successive values of said gap;
- measuring a post-etch critical dimension (CD) on each test workpiece and correlating each CD with the corresponding workpiece-to-ceiling gap to produce correlated measurements;
- searching said correlated measurements for:
- (1) a first value of said gap at which measured CD features exceeds a desired CD value, and (2) a second value of said gap at which measured CD is less than said desired CD value;
- and
- placing the production workpiece in said reactor, setting said gap to an intermediate value between said first and second values and performing an etch process while maintaining said process parameters at said same set of corresponding parameter values.
Dependencies are inferred from the claim text.