Metrology mark structure and method of determining metrology mark structure
A structure of a semiconductor device with a sub-segmented grating structure as a metrology mark and a method for configuring the metrology mark. The method for configuring a metrology mark may be used in a lithography process. The method may include determining an initial characteristic function of an initial metrology mark disposed within a layer stack. The method also includes perturbing one or more variables of the plurality of subsegments of the metrology mark (e.g., pitch, duty cycle, and/or line width of the plurality of subsegments) and further perturbing a thickness of one or more layers within the layer stack. The method further includes iteratively performing the perturbations until a minimized characteristic function of an initial metrology mark is determined to set a configuration for the plurality of subsegments.
1 . A method comprising:
a) obtaining an initial version of a characteristic function of an initial version of a metrology mark disposed within a layer stack for use in a lithography process, the initial version of the metrology mark comprising a plurality of mark segments, at least one of the mark segments comprising a plurality of subsegments, wherein the characteristic function comprises:
a change in a wavelength of a reflected beam with respect to the wavelength of an incident radiation as a function of a change in thickness of the layer stack, the reflected beam being a beam reflected from the metrology mark and passing through the layer stack, or
a change in angular reflectance of the reflected beam as a function of a change in thickness of the stack;
b) perturbing one or more variables of the plurality of subsegments, wherein the one or more variables comprise pitch, duty cycle, and/or line width of the plurality of subsegments;
c) perturbing a thickness of one or more layers within the layer stack;
d) updating, by a hardware computer, the characteristic function based upon the perturbations of b) and c);
e) iteratively performing steps b), c) and d) until a further version of the characteristic function is determined to set a configuration for the plurality of subsegments; and
f) physically creating a metrology mark instance having the configuration for the plurality of subsegments, physically creating a patterning device to create at least part of the metrology mark instance, or providing a signal representing, or based on, the configuration for the plurality of subsegments to a tool or system for use by the tool or system to enable creation of the metrology mark instance or of the patterning device.
2 . The method of claim 1 , wherein the characteristic function comprises the change in a wavelength of a reflected beam with respect to the wavelength of an incident radiation as a function of a change in thickness of the layer stack.
3 . The method of claim 1 , wherein the characteristic function comprises the change in angular reflectance of the reflected beam as a function of a change in thickness of the stack.
4 . The method of claim 1 , wherein the pitch and duty cycle remain constant and wherein the line width of the plurality of subsegments is varied.
5 . The method of claim 1 , wherein the pitch and line width remain constant and wherein the duty cycle of the plurality of subsegments is varied.
6 . The method of claim 1 , wherein the line width and duty cycle remain constant and wherein the pitch of the plurality of subsegments is varied.
7 . The method of claim 1 , wherein e) is performed a predetermined number of times before the further version of the characteristic function is determined.
8 . A computer program product comprising a non-transitory computer readable medium having instructions therein, the instructions, when executed by a computer system, configured to cause the computer system to at least:
a) obtain an initial version of a characteristic function of an initial version of a metrology mark disposed within a layer stack for use in a lithography process, the initial version of the metrology mark comprising a plurality of mark segments, at least one of the mark segments comprising a plurality of subsegments, wherein the characteristic function comprises:
a change in a wavelength of a reflected beam with respect to the wavelength of an incident radiation as a function of a change in thickness of the layer stack, the reflected beam being a beam reflected from the metrology mark and passing through the layer stack, or
a change in angular reflectance of the reflected beam as a function of a change in thickness of the stack;
b) perturb one or more variables of the plurality of subsegments, wherein the one or more variables comprise pitch, duty cycle, and/or line width of the plurality of subsegments;
c) perturb a thickness of one or more layers within the layer stack;
d) update the characteristic function based upon the perturbations of b) and c);
e) iteratively perform b), c) and d) until a further version of the characteristic function is determined to set a configuration for the plurality of subsegments; and
f) cause physical creation of a metrology mark instance having the configuration for the plurality of subsegments, cause physical creation of a patterning device to create at least part of the metrology mark instance, or provide a signal representing, or based on, the configuration for the plurality of subsegments to a tool or system for use by the tool or system to enable creation of the metrology mark instance or of the patterning device.
9 . The computer program product of claim 8 , wherein the characteristic function comprises the change in a wavelength of a reflected beam with respect to the wavelength of an incident radiation as a function of a change in thickness of the layer stack.
10 . The computer program product of claim 8 , wherein the characteristic function comprises the change in angular reflectance of the reflected beam as a function of a change in thickness of the stack.
11 . The computer program product of claim 8 , wherein the pitch and duty cycle remain constant and wherein the line width of the plurality of subsegments is varied.
12 . The computer program product of claim 8 , wherein the pitch and line width remain constant and wherein the duty cycle of the plurality of subsegments is varied.
13 . The computer program product of claim 8 , wherein the line width and duty cycle remain constant and wherein the pitch of the plurality of subsegments is varied.
14 . A computer program product comprising a non-transitory computer readable medium having instructions therein, the instructions, when executed by a computer system, configured to cause the computer system to at least:
obtain an initial version of a characteristic function of a metrology mark disposed within a layer stack for use in a lithography process, wherein the characteristic function comprises:
a change in a wavelength of a reflected beam with respect to the wavelength of an incident radiation as a function of a change in thickness of the layer stack, the reflected beam being a beam reflected from the metrology mark and passing through the layer stack, or
a change in angular reflectance of the reflected beam as a function of a change in thickness of the stack;
iteratively perturb one or more variables of the metrology mark and/or of the layer stack and update the characteristic function based upon the perturbation, until a further version of the characteristic function is determined to set a configuration for the metrology mark; and
cause physical creation of a metrology mark instance having the configuration for the metrology mark, cause physical creation of a patterning device to create at least part of the metrology mark instance, or provide a signal representing, or based on, the configuration for the metrology mark to a tool or system for use by the tool or system to enable creation of the metrology mark instance or of the patterning device.
15 . The computer program product of claim 14 , wherein the perturbation of one or more variables of the metrology mark and/or of the layer stack comprises perturbation of a thickness of one or more layers within the layer stack.
16 . The computer program product of claim 14 , wherein the characteristic function comprises the change in a wavelength of a reflected beam with respect to the wavelength of an incident radiation as a function of a change in thickness of the layer stack.
17 . The computer program product of claim 14 , wherein the characteristic function comprises the change in angular reflectance of the reflected beam as a function of a change in thickness of the stack.
18 . The computer program product of claim 14 , wherein the initial version of the metrology mark comprises a plurality of mark segments, at least one of the mark segments comprising a plurality of subsegments, and wherein the perturbation of one or more variables of the metrology mark and/or of the layer stack comprises perturbation of one or more variables of the plurality of subsegments, wherein the one or more variables comprise pitch, duty cycle, and/or line width of the plurality of subsegments.
19 . The computer program product of claim 18 , wherein the pitch and duty cycle remain constant, wherein the line width of the plurality of subsegments is varied and wherein the perturbation of one or more variables of the metrology mark and/or of the layer stack comprises perturbation of a variable of one or more layers within the layer stack.
20 . The computer program product of claim 18 , wherein the pitch and line width remain constant, wherein the duty cycle of the plurality of subsegments is varied and wherein the perturbation of one or more variables of the metrology mark and/or of the layer stack comprises perturbation of a variable of one or more layers within the layer stack.