1. A method of controlling one or more critical dimension (CD) features, dependent upon at least a first and a second processing parameter, with a single metrology step, while still enabling decoupled feedback to the first and the second processing parameter, said method comprising: an initial process characterization, the initial process characterization further comprising: determining a first CD feature; determining a second CD feature; defining a first target dimension value (Tgt 1 ) for the first CD feature; defining a second target dimension value (Tgt 2 ) for the second CD feature; characterizing a rate of change (Δ 11 ) for the first CD feature in response to the first processing parameter in a test piece; characterizing a rate of change (Δ 21 ) for the second CD feature in response to the first processing parameter in the test piece; characterizing a rate of change (Δ 12 ) for the first CD feature in response to the second processing parameter in the test piece; characterizing a rate of change (Δ 22 ) for the second CD feature in response to the second processing parameter in the test piece; and producing a production piece following the initial process characterization, further comprising: forming the first CD feature and second CD feature in the production piece; performing the single metrology step following the completion of producing the production piece, wherein the single metrology step further comprises: measuring the first CD feature (CD 1 ) and second CD feature (CD 2 ); defining a first variable (x) to represent a first unknown correction value for the first processing parameter; defining a second variable (y) to represent a second unknown correction value for the second processing parameter; defining a first equation as CD 1 =T gt1 +(Δ 11 )(x)+(Δ 12 )(y); defining a second equation as CD 2 =T gt2 +(Δ 21 )(x)+(Δ 22 )(y); and solving the first equation and the second equation simultaneously to determine the first variable and the second variable; implementing the decoupled feedback by: assigning the determined value for the first variable to the first unknown correction value and applying it as feedback to the first processing parameter; and assigning the determined value for the second variable to the second unknown correction value and applying it as feedback to the second processing parameter.