Method for improving deep trench isolation depth of focus process window

Abstract

The invention relates to a method for improving a deep trench isolation depth of focus process window. The method comprises the following steps of providing a semiconductor substrate, wherein an oxidelayer, a first anti-reflection layer and a first photoresist layer sequentially cover an upper surface of the semiconductor substrate; exposing the first photoresist layer; etching; removing the first photoresist layer, the first anti-reflection layer and the oxide layer to form a second anti-reflection layer; forming a second photoresist layer; exposing the second photoresist layer to form an initial process window; forming a water-soluble organic compound layer; performing high-temperature baking on the second photoresist layer to form a final process window; etching; and removing the second anti-reflection layer, the second photoresist layer and the water-soluble organic compound layer, wherein the size of the initial process window is larger than the size of the final process window.The method has the advantages that the size of the initial process window is larger than the size of the final process window, the depth-to-width ratio is reduced, and the reliable process productionrequirement is met.

Description

technical field [0001] The invention relates to the field of microelectronics, in particular to a method for improving the deep trench isolation focal depth process window. Background technique [0002] CIS image sensors are widely used due to their inherent low power consumption, low cost, small size, random readability, and high integration. [0003] With the development of the technology, the existing CIS image sensor obtains higher quantum efficiency by introducing the CDTI+DTI (deep trench isolation) structure, and reduces the loss of light reflection through multi-level and high-depth optical barriers. But this structure requires a relatively strict depth of focus process window (DOF window). [0004] Such as Figure 1a-1d As shown, the process flow in the prior art is to firstly carry out CDTI exposure ( Figure 1a ), filling the anti-reflection layer on the basis of the CDTI structure ( Figure 1b ), followed by DTI exposure ( Figure 1c ), and finally form a CDT...

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