AZ ECI 3000 Process steps

! Cleanroom humidity warning !

Control of the relative humidity (RH) in photolithography zones is extremely critical. Stable and reproducible photolithography is expected within 38% to 48% RH range.

  • In case of low RH (< 38%), the resist sensitivity and development rate decreases. It is then recommended to increase the exposure dose to compensate.
  • In case of high RH (> 48%), the resist adhesion decreases. It is then recommended to do an additional bake (>10 minutes @ 150°C) before loading the wafers in the HMDS or coating equipment.

Wafer surface preparation

Usually adhesion of photoresist on inorganic materials is poor resulting in losses of fine structures after development. To solve the issue, silicon wafers are generally treated using the HMDS vapor prime treatment before spincoating the photoresist. Details about the HMDS process and control can be found here: link

Assuming wafers with a clean surface free of organic contamination, the best adhesion will be obtained with the surface preparation recommended in the table:

Surface material (larger area) Vapor HMDS Plasma O2 Thermal dehydratation
Si √√ √ √
SiO2, fused silica, SiN, Si3N4 √√ √ √
Float glass, pyrex √ √√ √
Metals: Al, Au, Pt, Ti … √ √√
Metals: Ag, Cu, Cr, Fe … X √√
III/V semiconductors (GaN, GaAs) … X √√

Legend: √√ Strongly recommended / √ Alternative process / … Not effective / X May affect or destroy underlaying material

Spincoating

The AZ ECI 3007 and ECI 3027 spincurves are shown below, as well as process details for both automatic and manual coating.

Available thicknesses: 0.6 um / 1 um / 1.5 um / 2.6 um / 4.2 um

Coating:

PR thickness [μm] PR Dispense method Spin speed [RPM] Spin duration [sec] Notes
0.6 ECI 3007 dynamic, 500RPM 6000 40  
1 ECI 3007 dynamic, 1650RPM 2050 40  
1.5 ECI 3007 dynamic, 850RPM 850 40 postbake BSR/EBR
2.6 ECI 3027 dynamic, 1650RPM 6000 40  
4.2 ECI 3027 dynamic, 1650RPM 1650 40 postbake BSR/EBR

Softbake:

PR thickness [μm] Bake method Temperature [°C] Bake duration [sec]
0.6 minimum proximity 100 90
1 minimum proximity 100 90
1.5 minimum proximity 100 120
2.6 minimum proximity 100 120
4.2 minimum proximity 100 180

Available sequence options:

  • HMDS / EC (edge clean)
  • Dehydrate / EC
  • No treatment / EC
  • HMDS / EBR (edge bead removal)
  • Dehydrate / EBR
  • No treatment / EBR

Available thicknesses: 0.6 um / 1 um / 2.6 um / 4.2 um

Coating:

PR thickness [μm] PR Dispense method Spin speed [RPM] Spin duration [sec] Notes
0.65 ECI 3007 dynamic, 1500RPM 6000 30  
1 ECI 3007 dynamic, 1500RPM 2000 30  
2.6 ECI 3027 dynamic, 1800RPM 6550 30  
4.2 ECI 3027 dynamic, 1800RPM 1525 30  

 

Softbake:

PR thickness [μm] Bake method Temperature [°C] Bake duration [sec]
0.6 proximity – 150um 90 60
1 proximity – 150um 90 60
2.6 proximity – 150um 100 60
4.2 proximity – 150um 100 60

 

Available sequence options:

  • HMDS / EC (edge clean)
  • Dehydrate / EC
  • No treatment / EC
  • HMDS / EBR (edge bead removal)
  • Dehydrate / EBR
  • No treatment / EBR
  • Find the spin-coating speed “XXXX” [RPM] matching your target thickness from the AZ ECI 3007 spincurve.
  • When coating on wafers, use the STD_”XXXX” recipe, which includes a 500 RPM spreading step and 40 seconds of main coating step.
  • When coating on small chips, use the CHIP_”XXXX” recipe, which includes 40 seconds of main coating step and a short acceleration at the end to reduce edge bead effects.
  • Softbake temperature: 90°C
  • Softbake time: 30” + 30”/um

Exposure

The following table lists the recommend dose “to clear” for the AZ ECI photoresist series coated on silicon wafers. It is recommended to perform a contrast curve / exposure matrix calibration for wafers other than silicon.

Illumination:  Broadband* i-line (355-365 nm) h-line (405 nm)
Equipment:  MA6 Gen3 (no filter) VPG 200, MA6 Gen3 (filter), MJB4  MLA 150
PR thickness [µm]  Dose [mJ/cm2]+  Dose [mJ/cm2]++  Dose [mJ/cm2]+++
0.6 96 100 Refer to Resist Tables
1 115 120
1.5 145 150
2.6 200 210
4.2 330 350

* Mercury Lamp, Mask Aligner with UV400 configuration & no filter / + Based on intensity readings from Süss optometer broadband CCD / ++ Based on intensity readings from Süss optometer i-line CCD / +++ Based on MLA150 internal dose measurements

Development

The recommended developer for AZ ECI photoresist series is AZ 726 MIF (or MF CD 26), an organic solution based upon TMAH.

IMPORTANT: AZ ECI are chemically amplified resists and requires a post-exposure bake (PEB) before development. On automated development equipment, the PEB is included in the development sequences. For manual development, make sure to perform the PEB as indicated in the section below!

Development sequences for the AZ ECI resist family on the ACS 200 are detailed below:

Post-exposure bake (PEB):

The PEB step is part of the standard development recipes on the ACS 200 system.

PR thickness [μm] Bake method Temperature [°C] Bake duration [sec]
0.6 minimum proximity 110 60
1 minimum proximity 110 60
1.5 minimum proximity 110 60
2.6 minimum proximity 110 90
4.2 minimum proximity 110 90


Development:

PR thickness [μm] Developer Dev. method Cycle time [sec] N° of cycles
0.6 AZ 726 MIF puddle 30 2
1 AZ 726 MIF puddle 30 2
1.5 AZ 726 MIF puddle 30 2
2.6 AZ 726 MIF puddle 30 2
4.2 AZ 726 MIF puddle 30 3


In case of non-complete PR dissolution with the standard development duration, please use any of the D4+(X)-726MIF sequences to add some development time.

Development sequences for the AZ ECI resist family on the EVG 150 are detailed below:

Post-exposure bake (PEB):

The PEB step is part of the standard development recipes on the EVG 150 system.

PR thickness [μm] Bake method Temperature [°C] Bake duration [sec]
0.6 proximity – 300um 110 90
1 proximity – 300um 110 90
2.6 proximity – 300um 110 90
4.2 proximity – 300um 110 90


Development:

PR thickness [μm] Developer Dev. method Cycle time [sec] N° of cycles
0.6 AZ 726 MIF puddle 50 1
1 AZ 726 MIF puddle 50 1
2.6 AZ 726 MIF puddle 50 1
4.2 AZ 726 MIF puddle 50 1


In case of non-complete PR dissolution with the standard development duration, please use any of the D4+(X)-726MIF sequences to add some development time.

  • PEB temperature: 100°C
  • PEB time: 60” (ECI 3007) or 90” (ECI 3027)
  • Recommended developer: AZ 726 MIF (no dilution needed)
  • Development time: 20″-30″/um
  • Rinse: H2O 1min

IMPORTANT:
After development, it is mandatory for wafers to go through an additional rinsing step with DI water to avoid backside contamination and damage on equipments (chuck in etcher) in further processing steps. The water baths of the following wet benches can be used free of charge (5 min. billing delay after login):

AZ ECI 3007 thermal reflow

Thermal reflow of photoresist is used to smooth and reshape photoresist patterns by heating them above their glass transition temperature. This technique allows the photoresist to flow, reducing surface roughness and achieving more rounded features (important for IBE). It is commonly applied to enhance the profile of microstructures, particularly in applications requiring curved or sloped sidewalls. The reflow process must be carefully controlled to avoid excessive deformation or pattern collapse.

The ratio between height and width of the feature to reflow has a great impact on the result. A threshold is found to be at 1:3 to round the structure / lower the sidewalls slope as presented in the image below.

In practice for AZ ECI 3007:

  • Reflow on a hot plate : 120s @ 125°C
  • Reflow in ACS200 : 180s or 300s @ 145°C

Time can be adjusted based on the slope desired. Pictures of the results can be seen in the gallery below.

Pictures Gallery