Method for reducing wafer edge defects
A method for reducing wafer edge defects is provided. The method includes providing a wafer with a central region and an edge region, forming a hard mask layer on the wafer, forming a spacer pattern on the hard mask layer, forming a photoresist layer covering the spacer pattern, performing a wafer edge treatment process on the photoresist layer to form an annular photoresist pattern, using the annular photoresist pattern as an etching mask, and sequentially transferring the exposed spacer pattern to the hard mask layer and the wafer to form a plurality of trenches in the wafer.
1 . A method for reducing wafer edge defects, comprising:
providing a wafer with a central region and an edge region, wherein the edge region comprises a first edge region surrounding the central region, a second edge region surrounding the first edge region, and a third edge region surrounding the second edge region;
forming a hard mask layer on the wafer;
forming a spacer pattern on the hard mask layer;
forming a photoresist layer covering the spacer pattern;
performing a wafer edge treatment process on the photoresist layer to form an annular photoresist pattern, wherein the annular photoresist pattern selectively covers the spacer pattern located in at least one of the first edge region, the second edge region, and the third edge region and exposes the spacer pattern in the central region; and
using the annular photoresist pattern as an etching mask, sequentially transferring the exposed spacer pattern to the hard mask layer and the wafer to form a plurality of trenches in the wafer.
2 . The method as claimed in claim 1 , wherein after forming the hard mask layer, performing a self-alignment double patterning process to form the spacer pattern on the hard mask layer, wherein the self-alignment double patterning process comprises:
forming a patterned mandrel on the hard mask layer;
conformally forming a spacer material layer on the hard mask layer and the patterned mandrel;
etching the spacer material layer to expose a top surface of the patterned mandrel; and
removing the patterned mandrel to form the spacer pattern.
3 . The method as claimed in claim 2 , wherein forming the patterned mandrel comprises:
forming a mandrel layer on the hard mask layer;
forming another photoresist layer on the mandrel layer;
performing a wafer edge exposure process or an edge bead removal process on the other photoresist layer to remove the other photoresist layer in the edge region;
patterning the other remaining photoresist layer to form a mandrel photoresist pattern; and
transferring the mandrel photoresist pattern to the mandrel layer to form the patterned mandrel.
4 . The method as claimed in claim 2 , wherein a material of the patterned mandrel comprises carbon, silicon nitride, bottom anti-reflective coating, or a combination thereof.
5 . The method as claimed in claim 1 , wherein the wafer edge treatment process further comprises a wafer edge exposure process or an edge bead removal process.
6 . The method as claimed in claim 1 , wherein a width of each of the first edge region, the second edge region, and the third edge region is from about 0.5 mm to 1.5 mm.
7 . The method as claimed in claim 6 , wherein the width of each of the first edge region, the second edge region, and the third edge region is a total of about 3 mm to 3.5 mm.
8 . The method as claimed in claim 1 , wherein the edge region is an invalid chip region.
9 . The method as claimed in claim 1 , wherein the photoresist layer comprises a positive photoresist.
10 . The method as claimed in claim 1 , wherein the photoresist layer comprises a negative photoresist.
11 . The method as claimed in claim 1 , wherein the annular photoresist pattern is formed on two adjacent ones of the first edge region, the second edge region, and the third edge region.
12 . The method as claimed in claim 1 , wherein the annular photoresist pattern is formed on two non-adjacent ones of the first edge region, the second edge region, and the third edge region.
13 . The method as claimed in claim 1 , wherein the annular photoresist pattern is formed on only one of the first edge region, the second edge region, or the third edge region.
14 . The method as claimed in claim 1 , wherein the spacer pattern has an uneven height in the edge region, and wherein the annular photoresist pattern covers the spacer pattern at a relatively low height in the edge region.
15 . The method as claimed in claim 1 , wherein the edge region further comprises a fourth edge region surrounding the third edge region, and the annular photoresist pattern covers at least one of the first edge region, the second edge region, the third edge region, and the fourth edge region.
16 . The method as claimed in claim 1 , wherein after forming the trenches, the method further comprises:
forming a dielectric material layer on the wafer and filling the trenches with the dielectric material layer; and
performing a planarization process on the dielectric material layer to expose a top surface of the wafer and to form a trench isolation structure.
17 . The method as claimed in claim 1 , wherein the sequential transfer of the exposed spacer pattern to the hard mask layer and the wafer further comprises:
performing a first etching process to transfer the spacer pattern to the hard mask layer;
removing the annular photoresist pattern and the spacer pattern; and
using the patterned hard mask layer as an etching mask, and performing a second etching process to transfer the spacer pattern to the wafer.
18 . The method as claimed in claim 1 , wherein a material of the hard mask layer comprises silicon oxide formed from tetraethylorthosilicate (TEOS), silicon nitride, or silicon oxynitride.