Method of making alternating phase shift masks
View Patent ↗One inventive aspect relates to a phase shift mask suitable for lithographic processing of a device, to a method of making such a mask and to lithographic processing using such a mask. The phase shift mask is made taking into account the threshold or dose that will be used for lithographic processing using the mask. In this way, image imbalance will be reduced in a significant focus-exposure processing window. In one embodiment, evaluation of the image imbalance is performed taking into account the processing windows for the different edges of the features of the pattern.
1. A method of designing a phase shift mask, wherein the mask comprises at least a trench and light blocking parts, the mask being suitable for lithographic processing of a device using a predetermined illumination dose, the method comprising: selecting, by one or more computing devices, at least one set of mask parameters, the mask parameters comprising at least a trench bias, a light blocking part bias and an etching depth of the trench, taking into account the illumination dose, wherein the selecting at least one set of mask parameters comprises:
selecting a plurality of sets of mask parameters suitable for using the phase shift mask substantially in focus, wherein the selecting a plurality of sets of mask parameters suitable for using the phase shift mask substantially in focus comprises adjusting the light blocking part bias to correct a feature size and adjusting the trench bias to correct a feature position; and
selecting from the plurality of sets of mask parameters at least one set of mask parameters suitable for using the phase shift mask with the illumination dose in a predetermined out of focus range.
2. A method according to claim 1 , wherein the selecting at least one set of mask parameters suitable for using the phase shift mask with the illumination dose in a predetermined out of focus range comprises selecting a set of mask parameters corresponding with a predetermined etching depth.
3. A method according to claim 1 , wherein the selecting at least one set of mask parameters suitable for using the phase shift mask with the illumination dose in a predetermined out of focus range comprises:
determining any of a focus-exposure matrix or an amount of feature displacement for a feature printable using the mask for the plurality of sets of mask parameters; and
evaluating the focus exposure matrix or amount of feature displacement for a feature printable using the mask.
4. A method according to claim 3 , the method further comprising: evaluating a focus-exposure window for a feature printable using the mask, wherein the focus-exposure window is determined by a common part of focus-exposure windows for at least two edges of the feature printable using the mask.
5. A method of designing a phase shift mask, the mask comprising at least a trench and light blocking parts, the mask being suitable for lithographic processing of a device using a predetermined illumination dose, the method comprises selecting, by one or more computing devices, a set of mask parameters comprising at least a trench bias, a light blocking part bias and an etching depth of the trench, taking into account the illumination dose, wherein the selecting a set of mask parameters comprises:
selecting a plurality of sets of mask parameters suitable for using the phase shift mask substantially in focus, wherein the selecting a plurality of sets of mask parameters suitable for using the phase shift mask substantially in focus comprises adjusting the light blocking part bias to correct a feature size and adjusting the trench bias to correct a feature position; and
selecting from the plurality of sets of mask parameters at least one set of mask parameters suitable for using the phase shift mask with the illumination dose in a predetermined out of focus range.
6. A method according to claim 5 , wherein
the selecting at least one set of mask parameters suitable for using the phase shift mask with the illumination dose in a predetermined out of focus range comprises selecting a set of mask parameters corresponding with a predetermined etching depth.
7. A method according to claim 5 , wherein the selecting at least one set of mask parameters suitable for using the phase shift mask with the illumination dose in a predetermined out of focus range comprises:
determining any of a focus-exposure matrix or an amount of feature displacement for a feature printable using the mask for the plurality of sets of mask parameters; and
evaluating the focus exposure matrix or amount of feature displacement for a feature printable using the mask.
8. A method according to claim 7 , wherein the method further comprises evaluating a focus-exposure window for a feature printable using the mask, wherein the focus-exposure window is determined by a common part of focus-exposure windows for at least two edges of the feature printable using the mask.
9. A computer-readable medium having stored thereon instructions which, when executed on a computing device, causes the computing device to perform the method of claim 5 .