Method for adjusting local thickness of photoresist

A method for adjusting a local thickness of a photoresist in semiconductor manufacturing, wherein the method at least comprises:

• step 1:
• providing a semiconductor front layer structure, wherein the semiconductor front layer structure comprises:
• a silicon substrate;
• a shallow-trench-isolation (STI) area for isolating active regions in the silicon substrate, wherein the active regions in the silicon substrate are configured to include strip structures, wherein the strip structures are configured to have different heights;
• and
• a stack structure disposed on the strip structures, wherein the stack structure forms regions of different surface heights from uneven strip structures underneath, wherein the stack structure comprises second nitrogen doped silicon carbide (NDC2), silicon dioxide (SiO2), nitrogen doped silicon carbide (NDC), nitrogen trifluoride (NF), and titanium nitride (TiN) sequentially stacked from bottom to top on the silicon substrate;
• step 2:
• spin-coating a photoresist layer on a top surface of the stack structure, wherein the photoresist layer disposed on a portion of the stack structure having a higher surface comprises a first thickness H1, and the photoresist layer disposed on a portion of the stack structure having a lower surface comprises a second thickness H2, wherein H1>H2;
• step 3:
• providing a photomask, wherein the photomask comprises an auxiliary pattern for exposing a first region and another pattern for exposing a second region, wherein the auxiliary pattern comprises a plurality of unit patterns distributed in an array, wherein a number of rows and a number of columns in the array are integers larger than 1;
• and
• step 4:
• exposing the first region and the second region of the photoresist layer simultaneously by the photomask, and adjusting an exposure intensity to achieve under-exposure in the first region, wherein, after photoresist development only part of the first region is dissolved, the auxiliary pattern is not transferred to the photoresist layer into the first region, and a thickness of the photoresist layer in the first region becomes H2, and wherein the other pattern on the photomask is transferred to the photoresist layer in the second region.