Thin Film Resistor Trench Patterning via CMP

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Solution Overview

Problem

Existing methods for patterning thin film resistors in semiconductor manufacturing are affected by topography, leading to critical dimension issues and the creation of metal 'stringers' that can electrically short the resistors.

Innovation Solution

A system and method involving etching a trench in a dielectric material, depositing a thin film resistor layer that lines the trench, followed by a chemical mechanical polishing process to remove excess materials, and patterning an interconnect metal layer to eliminate stringers, thereby avoiding topographical effects on critical dimensions and electrical shorts.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If traditional masking and etching methods are used to pattern thin film resistors, then the manufacturing process is simple, but topography effects cause critical dimension variations and metal stringers create electrical shorts

Engineering Contradiction:

Improvecritical dimension controlVSAvoidprocess complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent divides the patterning process into multiple stages: first forming a mandrel structure, then depositing and etching the thin film resistor material, and finally removing the mandrel. This segmentation allows precise control of critical dimensions while avoiding the stringer formation problem that occurs in single-step etching processes

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent performs preliminary actions by first depositing the thin film resistor material and forming protection layers before etching. The mandrel structure is prepared in advance with precise dimensions, ensuring that the final resistor critical dimensions are controlled by the mandrel geometry rather than being affected by topography during etching

Inventive Principle:

Principle #10Preliminary action

2Ease of manufacture

If tungsten etch back process is used to remove excess tungsten, then the process is straightforward, but tungsten stringers remain adjacent to liner edges and cause electrical shorts

Engineering Contradiction:

Improveetch process simplicityVSAvoidelectrical isolation

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent extracts and removes the mandrel structure after the thin film resistor material has been deposited and patterned. By removing the mandrel in a controlled manner, the process eliminates the stringer formation problem that would otherwise occur with traditional etch back methods, ensuring electrical isolation between adjacent structures

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The mandrel acts as an intermediary structure that enables precise patterning of the thin film resistor. The mandrel geometry serves as a template that defines the critical dimensions, and its controlled removal leaves clean edges without stringer formation, maintaining electrical isolation

Inventive Principle:

Principle #24Intermediary (Mediator)

3Productivity

If multiple etching steps are used to remove protection material and liners, then complete removal is achieved, but the process time increases and stringers remain

Engineering Contradiction:

Improvemanufacturing throughputVSAvoidstringer elimination

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The patent maintains continuous useful action by designing the mandrel structure and etching process to work together throughout the fabrication sequence. The mandrel remains in place during material deposition, providing continuous dimensional control, and is removed in a single controlled step that simultaneously achieves complete material removal and stringer elimination, improving throughput while maintaining precision

Inventive Principle:

Principle #20Continuity of useful 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

The solution effectively eliminates the impact of topography on critical dimensions and prevents metal stringers from shorting the thin film resistors, improving the manufacturing process efficiency and reliability.

Implementation Method 1

a chemical mechanical polishing process is applied to remove the excess portions of the thin film resistor layer and to remove the excess portions the thin film resistor protection layer

Methodology Applied

Scientific EffectChemical mechanical polishing:

Data Source

PatentUS8679932B1System and method for manufacturing thin film resistors using a trench and chemical mechanical polishing

Publication Date: 2014.03.25 NAT SEMICON CORP

AI summary

A system and method is disclosed for manufacturing thin film resistors using a trench and chemical mechanical polishing. A trench is etched in a layer of dielectric material and a thin film resistor layer is deposited so that the thin film resistor layer lines the trench. A thin film resistor protection layer is then deposited to fill the trench. Then a chemical mechanical polishing process removes excess portions of the thin film resistor layer and the thin film resistor protection layer. An interconnect metal is then deposited and patterned to create an opening over the trench. A central portion of the thin film resistor protection material is removed down to the thin film resistor layer at the bottom of the trench. The resulting structure is immune to the effects of topography on the critical dimensions (CDs) of the thin film resistor.