Dummy Pattern Prevents Photoresist Crust on Semiconductor Gates

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Solution Overview

Problem

Thick photoresist patterns in semiconductor manufacturing can develop a crust during ion implantation, leading to defects such as pattern collapse during subsequent removal, affecting production yield.

Innovation Solution

A method involving a dummy pattern around the semiconductor substrate to prevent crust attachment to gates during resist stripping, using a sulfuric acid-hydrogen peroxide mixture at elevated temperatures and a wet cleaning process with ammonium hydroxide and hydrogen peroxide.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a thick photoresist pattern is used to mask regions during ion implantation, then the masking effectiveness is improved, but a crust forms on the photoresist surface that is easy to crack and cause defects

Engineering Contradiction:

Improvemasking effectivenessVSAvoidcrust formation and cracking

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The dummy pattern is formed in advance around the first region before the ion implantation process. This preliminary structure provides a surface for the crust to attach to during subsequent processing steps, preventing the crust from forming on and damaging the actual device structures.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The dummy pattern acts as an intermediary structure that intercepts the crust formation. Instead of the crust forming directly on the gates and active areas, it forms on the dummy pattern which is specifically designed to accommodate this harmful byproduct of the thick photoresist process.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of manufacture

If the photoresist pattern is removed after ion implantation, then the masking layer is successfully removed, but the crust may cause pattern collapse and defects

Engineering Contradiction:

Improvephotoresist removalVSAvoidpattern integrity

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The harmful crust is effectively extracted or separated from the critical device structures by providing the dummy pattern as a dedicated attachment surface. During photoresist removal, the crust remains attached to the dummy pattern or is easily removed without affecting the gates and active areas.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The crust, which is normally a harmful byproduct causing defects, is converted into a beneficial element by providing it with a designated home on the dummy pattern. This transforms the crust from a defect source into a controlled feature that protects the actual device structures.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Quantity of substance

If high-dose LDD ion implantation is performed through thick photoresist, then the doping effectiveness is improved, but crust formation on the photoresist sidewall increases

Engineering Contradiction:

Improvedopant implantation doseVSAvoidcrust on photoresist sidewall

Core Design Contradiction:

Quantity of substanceVSObject-generated harmful factors

Solution Approach 1:

The dummy pattern is prepared in advance around the first region to provide a predetermined surface for crust attachment. This preliminary structure ensures that when high-dose ion implantation creates crust on the photoresist sidewall, the crust has a designated location to form without damaging critical structures.

Inventive Principle:

Principle #10Preliminary action

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

Prevents crust attachment to gates, reducing defects and improving production yield by effectively removing the photoresist pattern without dopant loss.

Implementation Method 1

A resist stripping process is performed to remove the resist pattern by using a sulfuric acid-hydrogen peroxide mixture (SPM) solution at a temperature that is higher than or equal to 120 ̃190 degrees Celsius

Methodology Applied

Scientific EffectChemical etching:

Implementation Method 2

An ion implantation process is performed to implant dopants through the opening into the first active area not covered by the first gate within the first region

Methodology Applied

Scientific EffectIon implantation: Ion Implantation

Data Source

PatentUS11515213B2Method of forming a semiconductor device

Publication Date: 2022.11.29 UNITED MICROELECTRONICS CORP

AI summary

A method for forming a semiconductor device. A substrate having a first region and a second region surrounding the first region is provided. The first region includes a first active area and a first gate. A dummy pattern is disposed on the substrate within the second region around a perimeter of the first region. A resist pattern masks the second region and includes an opening that exposes the first region. An ion implantation process is performed to implant dopants through the opening into the first active area not covered by the first gate within the first region, thereby forming doped regions in the first active area. A resist stripping process is performed to remove the resist pattern by using a sulfuric acid-hydrogen peroxide mixture (SPM) solution at a temperature that is higher than or equal to 120˜190 degrees Celsius. The substrate is subjected to a cleaning process.