Stray light feedback for dose control in semiconductor lithography systems
AssigneeInfineon Technologies AG
InventorsSajan Marokkey, Wai-Kin Li, Todd C. Bailey
Life of this patent
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Abstract
A stray light feedback system and method for a lithography exposure tool. The stray light feedback helps control critical dimension (CD) within a stray light specification limit. A stray light dose control factor is calculated as a function of the stray light measured in the exposure tool and the sensitivity of the resist. The stray light dose control factor is used to adjust the exposure dose to achieve the desired CD. The stray light may be monitored, and if a threshold level of stray light is reached or exceeded, the use of the exposure tool may be discontinued for a particular type of semiconductor product, resist, or mask level, until the lens system is cleaned.
Claims28
A method of lithography, the method comprising:
- providing a workpiece, the workpiece having a layer of resist disposed thereon, the resist having a resist sensitivity factor;
- providing an exposure tool, the exposure tool comprising a lens system and being adapted to expose the layer of resist at an exposure dose;
- measuring an amount of stray light of the lens system of the exposure tool;
- setting a first threshold level for the stray light measured;
- determining a stray light dose control factor as a function of at least the amount of stray light;
- adjusting the exposure dose by the stray light dose control factor;
- discontinuing using a scanner for lithography for a first type of semiconductor product when the first threshold level is reached or exceeded;
- using the exposure tool to pattern a second type of semiconductor product after the first threshold level is reached or exceeded, the second type of semiconductor product being different from the first type of semiconductor product, wherein the first type of semiconductor product has a smaller minimum feature size than the second type of semiconductor product;
- and
- exposing the layer of resist on the workpiece with the adjusted exposure dose.
A method of adjusting an exposure dose of a lithography system, the method comprising:
- providing a first exposure tool, the first exposure tool comprising the exposure dose;
- measuring stray light in the first exposure tool;
- calculating a dose control factor by using Equation 2:
- Δ
-
-
- Dose
- =
- {
- SS
-
- (
- reference
-
-
- resist
- )
- *
- %
-
-
- stray
-
-
-
- light
-
-
- (
- reference
-
-
- resist
- )
- }
- *
- DS
-
- (
- reference
-
-
- resist
- )
- DS
-
- (
- resistX
- )
- ;
-
-
- where
-
-
- DS
- =
- Δ
-
-
- CD
- Δ
-
-
- Dose
- ;
-
-
- SS
- =
- Δ
-
-
- Dose
- Δ
-
-
- %
-
-
- StrayLight
- ;
- Eq
- .
-
- 2
- wherein DS is a dose slope calculated for a particular material layer and a particular resist at a reference critical dimension (CD), “SS (reference resist)” is a stray light sensitivity of a reference resist at the reference CD, “resist X” comprises a resist that will be used to pattern a material layer on the workpiece, and “% stray light (reference resist)” comprises the stray light measured for the reference resist;
- providing a resist sensitivity factor of a resist;
- and
- adjusting the exposure dose by the dose control factor.
A method of lithography, the method comprising:
- providing a workpiece, the workpiece having a layer of resist disposed thereon, the resist having a resist sensitivity factor;
- providing an exposure tool, the exposure tool comprising a lens system and being adapted to expose the layer of resist at an exposure dose;
- measuring an amount of stray light of the lens system of the exposure tool;
- determining the stray light dose control factor by using Equation 2:
- Δ
-
-
- Dose
- =
- {
- SS
-
- (
- reference
-
-
- resist
- )
- *
- %
-
-
- stray
-
-
-
- light
-
-
- (
- reference
-
-
- resist
- )
- }
- *
- DS
-
- (
- reference
-
-
- resist
- )
- DS
-
- (
- resistX
- )
- ;
-
-
- where
-
-
- DS
- =
- Δ
-
-
- CD
- Δ
-
-
- Dose
- ;
-
-
- SS
- =
- Δ
-
-
- Dose
- Δ
-
-
- %
-
-
- StrayLight
- ;
- Eq
- .
-
- 2
- wherein DS is a dose slope calculated for a particular material layer and a particular resist at a reference critical dimension (CD), “SS (reference resist)” is a stray light sensitivity of a reference resist at the reference CD, “resist X” comprises a resist that will be used to pattern a material layer on the workpiece, and “% stray light (reference resist)” comprises the stray light measured for the reference resist;
- adjusting the exposure dose by the stray light dose control factor;
- and
- exposing the layer of resist on the workpiece with the adjusted exposure dose.
Dependencies are inferred from the claim text.