SADP 25nm L&S Pattern Wafers | Service (Product)

Fine Pattern Formation Using SADP

Self-Aligned Double Patterning (SADP) is a fine-patterning technique in which a spacer film is formed on the sidewalls of a patterned core, or mandrel. After the mandrel is removed, the remaining spacers serve as lines. Because it uses sidewall spacers, this technique is also called spacer patterning.

Forming spacer lines on both sides of 1 mandrel provides 2 times the line density of the original mandrel pattern. The process consists of mandrel formation, conformal spacer-film deposition, anisotropic etch-back to remove the film from horizontal surfaces, and selective mandrel removal.

Philtech has used SADP to fabricate SiO line-and-space (L&S) patterns on 300 mm Si wafers, with a line width of 25 nm, a space width of 25 nm, and a pitch of 50 nm.

We can also assess the feasibility of custom SADP based on the assessment objectives, desired structures and dimensions, and specifications provided.

Assessment Applications for SADP Wafers

Patterned test wafers at intermediate stages of the SADP process can be used to assess semiconductor processes, including film deposition and dry etching.

Film Coverage AssessmentWafers with patterned SiN mandrels can be used to assess the deposited film. Coverage is assessed at the mandrel tops and sidewalls and at the bottoms of the openings.

Etch-Back Performance AssessmentWafers after SiO deposition and before etch-back can be used to assess film removal from horizontal surfaces and the SiO spacers remaining on the sidewalls after anisotropic etch-back.

Mandrel Removal AssessmentWafers after etch-back and before SiN mandrel removal can be used to assess selective SiN mandrel removal and the condition of the SiO spacers that remain.

Contact us to discuss specifications and processing conditions.

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25 nm L&S Fabrication Example

Item	Configuration
Substrate	300 mm Si wafer
Patterning method	SADP
Mandrel film	SiN (LP-SiN), film thickness 80 nm
Spacer film	SiO (LP-TEOS)
Fabricated structure	SiO, line width 25 nm / space width 25 nm / pitch 50 nm

Process Flow

SiN Mandrel Formation

Schematic cross-section of SiN mandrels formed on a Si substrate — SiN is patterned into periodic raised features to form the mandrels that define the spacer positions.

SiO Deposition

Schematic cross-section of SiO deposited on the SiN mandrel tops, sidewalls, and bottoms of the openings — A 20 nm SiO (LP-TEOS) film is deposited conformally over the mandrel tops, sidewalls, and bottoms of the openings.

SiO Etch-Back

Schematic cross-section after SiO removal from horizontal surfaces, leaving SiO on the SiN mandrel sidewalls — SiO is removed from horizontal surfaces, leaving SiO on the SiN mandrel sidewalls.

SiN Removal and SiO L&S Formation

Ideal schematic cross-section after SiN mandrel removal, showing vertical SiO spacers forming a 25 nm line-and-space pattern — The SiN mandrels are removed, leaving SiO spacers that form the 25 nm L&S pattern. The diagram shows an ideal cross-sectional profile.

Observation Results

A CD-SEM (scanning electron microscope used to measure pattern dimensions) shows a periodic L&S pattern with a line width of 25 nm, a space width of 25 nm, and a pitch of 50 nm.

CD-SEM image of vertically oriented, periodically arranged SADP 25 nm L&S patterns — Line width 25 nm / space width 25 nm / pitch 50 nm