Method and apparatus for measurement and control of photomask to substrate alignment
View Patent ↗A method, structure, system of aligning a substrate to a photomask. The method includes: directing incident light through a pattern of clear regions transparent to the incident light in an opaque-to-the-incident-light region of a photomask, through a lens and onto a photodiode formed in a substrate, the photodiodes electrically connected to a light emitting diode formed in the substrate, the light emitting diode emitting light of different wavelength than a wavelength of the incident lights; measuring an intensity of emitted light from light emitting diode; and adjusting alignment of the photomask to the substrate based on the measured intensity of emitted light.
1. A method; comprising:
directing incident light through a pattern of clear regions transparent to said incident light in an opaque-to-said-incident-light region of a photomask, through a lens and onto a photodiode formed in a substrate, said photodiode electrically connected to a light emitting diode formed in said substrate, said light emitting diode emitting light of different wavelength than a wavelength of said incident light;
measuring an intensity of emitted light from said light emitting diode; and
adjusting alignment of said photomask to said substrate based on said measured intensity of emitted light.
2. The method of claim 1 , wherein said adjusting alignment includes:
(i) adjusting a temperature of said photomask based on said measured intensity of light, (ii) adjusting a temperature of said lens based on said measured intensity of light, or (iii) adjusting both said temperature of said photomask and said temperature of said lens based on said measured intensity of light.
3. The method of claim 1 , further including,
maintaining said photomask and said lens at a same temperature.
4. The method of claim 1 , wherein said photodiode comprises first regions of said substrate that emit electrons when struck by said incident light interdigitated with second regions of said substrate that do not emit electrons when struck by said incident light.
5. The method of claim 4 , wherein:
said pattern of clear regions of said photomask and a pattern of said first and second regions are configured relative to each other to expose varying areas of said first and second regions to said incident light dependent upon a degree of alignment of said pattern of clear regions of said photomask to said pattern of first and second regions.
6. The method of claim 1 , wherein a photoresist layer formed on said substrate and exposed to said incident light undergoes a photochemical reaction when exposed to said incident light.
7. The method of claim 1 , further including:
passing said emitted light through a bandpass filter before said measuring of said intensity of said emitted light.
8. The method of claim 1 , wherein said incident light has a wavelength of about 193 nm or less and a substrate of said photomask is transparent to said incident light.
9. The method of claim 1 , wherein:
said substrate is a semiconductor substrate; and
said photomask includes a pattern of first regions transparent to and second regions opaque to said light, said pattern of first and second regions defining a fabrication level of an integrated circuit chip.