Femtosecond Laser Scribing for OLED Display Patterning

Overview of Technical Issues:

The critical challenge in femtosecond laser scribing for OLED displays is that the laser beam, while removing target film material, can transfer excessive heat to adjacent organic layers through thermal diffusion and plasma effects, causing harmful thermal degradation of temperature-sensitive materials (typically stable only below 100-150°C); this results in device performance loss, dark spot formation, or pixel failure in patterned regions, requiring optimization of pulse energy, duration, and overlap parameters to achieve selective ablation while maintaining thermal confinement within the target layer.

Solution directions generated for this problem

Problem Direction 1 :

ImproveLaser pulse energy density
VS
ConstraintMaterial removal rate

Inspiration 1 : Cross-domain reference

Application Principle: #19 Periodic action
Cross-domain applicability Assess applicability
Laser ablation system for package fabrication
Innovative Solution Refine solution

Burst-mode femtosecond laser with intra-burst energy modulation for high-throughput OLED scribing

Burst-mode with plasma-enhanced absorption
How to solve :
  • Deploy burst-mode femtosecond laser delivering 4–6 sub-pulses within 2 ps envelope, first sub-pulse at 0.8 J/cm² creates plasma shield enhancing absorption for subsequent sub-pulses at 0.5 J/cm² each
  • Optimize intra-burst delay to 300–500 fs allowing plasma-mediated energy coupling to increase effective ablation efficiency by 60–80%, achieving 95–110 nm removal per burst at 35% lower peak energy
  • Implement synchronized galvo scanning at 500 mm/s with burst repetition rate 200–400 kHz and 70% spot overlap, maintaining throughput while confining adjacent layer temperature below 95°C via reduced thermal accumulation
Expected Effect : Removal rate maintained at 100 nm/burst; peak energy reduced 35%; throughput equivalent to conventional single-pulse at higher energy; thermal damage eliminated
Risk Control :
  • plasma formation threshold variation across film batches
  • intra-burst timing jitter affecting absorption enhancement
  • burst energy stability requiring ±3% control

Problem Direction 2 :

ImproveLaser pulse energy density
VS
ConstraintProcessing throughput

Inspiration 1 : Cross-domain reference

Application Principle: #10 Preliminary action
Cross-domain applicability Assess applicability
Method and devices for controlling operations of a central processing unit
Innovative Solution Refine solution

Pre-heated substrate femtosecond laser scribing with adaptive energy control

Substrate pre-heated to 80-90°C before scribing
How to solve :
  • Install IR lamp array (wavelength 1.5-3 μm) in substrate holder, pre-heating OLED stack to 85±5°C uniformly across scribing zone, verified by thermal imaging camera (±2°C tolerance)
  • this reduces ablation threshold energy by 22-28%, enabling pulse energy reduction from baseline 150 nJ to 108-117 nJ while maintaining 100 nm removal depth per pulse
  • Implement real-time pyrometry feedback monitoring substrate temperature every 50 ms via fiber-optic sensor, automatically adjusting IR lamp power (acceptance range 80-90°C) to compensate for laser-induced heating accumulation during continuous scribing
  • Synchronize femtosecond laser (pulse duration 120 fs, repetition rate 500 kHz) with pre-heating zone, maintaining scanning speed 800 mm/s (vs. 300 mm/s without pre-heating), achieving throughput parity with conventional high-energy scribing while keeping adjacent organic layer peak temperature below 95°C (measured by embedded micro-thermocouples, ±3°C accuracy)
Expected Effect : Throughput maintained at baseline; pulse energy reduced 28%; thermal damage eliminated; scribing speed +167%
Risk Control :
  • Pre-heating uniformity deviation across large substrates
  • thermal expansion mismatch causing alignment drift
  • IR lamp aging affecting temperature stability

Problem Direction 3 :

ImproveThermal confinement duration
VS
ConstraintProcessing throughput

Inspiration 1 : Cross-domain reference

Application Principle: #19 Periodic action
Cross-domain applicability Assess applicability
Injection paradigm for administration of botulinum toxins
Innovative Solution Refine solution

Interlaced burst-scan femtosecond scribing for OLED thermal isolation

Time-spaced burst scanning
How to solve :
  • Use interlaced burst groups, 2-3 pulses at 20-80 ns, then revisit same line after 15-40 μs
  • Set fluence 0.12-0.22 J/cm2 per pulse, 343 or 515 nm, spot 8-15 μm, scan 1.2-2.0 m/s
  • Apply thermal QC with IR/pyrometry underlayer peak below 95°C, kerf 10±1 μm, residue under 3% by inline AOI
Expected Effect : Adjacent layer peak <95°C;throughput 85-95% of baseline;single-pass equivalent removal 90-120 nm;dark-spot defects -40 to -60%;edge HAZ <2 μm
Risk Control :
  • burst timing drift
  • plasma shielding excess
  • stage revisit misregistration

Problem Direction 4 :

ImproveAblation selectivity precision
VS
ConstraintProcessing throughput

Inspiration 1 : Cross-domain reference

Application Principle: #28 Mechanics substitution
Cross-domain applicability Assess applicability
Acousto-optic deflector applications in laser processing of dielectric or other materials
Innovative Solution Refine solution

Acousto-optic modulated real-time pulse energy control for selective OLED layer ablation

Replace mechanical energy control with acousto-optic modulator for real-time pulse adjustment
How to solve :
  • Integrate acousto-optic modulator (AOM) in beam path to adjust pulse energy within 10–50 ns response time, enabling dynamic energy control without mechanical delay
  • Deploy in-situ plasma emission spectroscopy monitoring at 100 kHz sampling rate to detect target layer removal completion via characteristic emission line disappearance (e.g., organic C-H bond at 431 nm), triggering AOM to reduce pulse energy by 70–85% for subsequent pulses
  • Implement closed-loop feedback algorithm that correlates plasma intensity with ablation depth (calibrated to ±5 nm precision), automatically modulating pulse energy from 150% threshold (initial breakthrough) to 40% threshold (final passes) while maintaining 500 mm/s scanning speed
Expected Effect : Depth control ±5nm; throughput maintained at 85–95% of non-feedback mode; adjacent layer temperature <95°C
Risk Control :
  • AOM response calibration drift over time
  • plasma signal interference from debris accumulation
  • spectroscopy alignment sensitivity to vibration

Problem Direction 5 :

ImproveLaser pulse energy density
VS
ConstraintMust not deteriorate

Inspiration 1 : Cross-domain reference

Application Principle: #10 Preliminary action
Cross-domain applicability Assess applicability
Methods and apparatus for optimizing selective photothermolysis
Innovative Solution Refine solution

Pre-ablation photochemical bond weakening for thermal-safe OLED scribing

Dual-pulse temporal separation approach
How to solve :
  • Deploy UV pre-conditioning pulse (343nm, 5ps duration, 0.08 J/cm²) to photochemically cleave C-C and C-N bonds in target organic film without thermal heating, reducing ablation threshold by 55%
  • Deliver femtosecond IR ablation pulse (1030nm, 150fs, 0.12 J/cm²) 50ns after pre-conditioning to remove weakened material at 50% lower energy than conventional single-pulse approach, achieving 95-110nm removal depth per burst
  • Implement in-situ plasma emission spectroscopy monitoring at 2MHz sampling rate to detect target layer characteristic emission lines (C₂ Swan bands 516nm)
  • auto-terminate pulse sequence within 100ns when emission drops below 15% baseline, ensuring ±8nm depth control and preventing over-ablation into adjacent layers
Expected Effect : Adjacent layer peak temp <95°C; ablation energy reduced 48-52%; throughput maintained at 85-92% of conventional rate; depth precision ±8nm; dark spot formation reduced >90%
Risk Control :
  • UV-IR pulse synchronization jitter exceeding ±20ns window
  • photochemical pre-weakening incomplete for high-Tg polymers
  • spectroscopic feedback latency causing over-ablation
Patsnap Eureka Solution