AZ 10XT 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 10XT-20 and 10XT-60 spincurves are shown below, as well as process details for both automatic and manual coating.

Available thicknesses: 2 um / 3 um / 4 um / 5.5 um / 8 um / 15 um

Coating:

PR thickness [μm] PR Dispense method Spin speed [RPM] Spin duration [sec] Notes
2 10XT-20 dynamic, 1650RPM 6000 40  
3 10XT-20 dynamic, 1650RPM 1650 40  
4 10XT-20 dynamic, 1050RPM 1050 40 postbake BSR/EBR
5.5 10XT-60 spiral 6000 40  
8 10XT-60 spiral 2600 40  
15 10XT-60 spiral 920 40 postbake BSR/EBR

Softbake:

PR thickness [μm] Bake method Temperature [°C] Bake duration [sec]
2 minimum proximity 110 120
3 minimum proximity 110 180
4 minimum proximity 110 210
5.5 minimum proximity 115 240
8 minimum proximity 115 240
15 minimum proximity 115 360

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 10XT-60 spincurve.
  • When coating on wafers, use the HV_”XXXX” recipe, which includes a 500 RPM spreading step and 100 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: 105°C
  • Softbake time: 90” + 20”/um

Exposure

Important note on rehdratation of AZ 10XT-60:

Optimal and stable lithography results cannot be obtained without a minimum rehydratation delay which allows water molecules to diffuse homogenoueously in the freshly coated layer. Without sufficient water content, chemical reactions induced by photons cannot be completed. Please respect the minimum rehydratation time given in the following table (for normal cleanroom relative humidity conditions (≥40 RH)).

PR thickness [µm]  Minimum rehydratation time [hour:min] Remark
 5 00:07  
 8 00:12  
 10 00:25  
 15 00:40  
 20 00:50  

Note: Diffusion time is largely dependant of relative humidity. Dry air with relative humidity smaller by -2.0 RH double the rehydratation time.

The following table lists the recommend dose “to clear” for the AZ 10XT family 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:  MABA6, MA6 Gen3 (no filter) VPG 200, MA6 Gen3 (filter), MJB4  MLA 150
PR thickness [µm]  Dose [mJ/cm2]+  Dose [mJ/cm2]++  Dose [mJ/cm2]+++
2 190 175 Refer to Resist Tables
3 240 220
4 300 270
5.5 360 330
8 460 420
15 660 580

* 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 10XT is AZ 400K (diluted in water 1:3.5), an inorganic solution based upon KOH. Development with AZ 400K will result in a sharper edge profile.

Development sequences for the AZ 10XT resist family on the ACS200 are detailed below:

Development:

PR thickness [μm] Developer Dev. method Cycle time [sec] N° of cycles
2 AZ 400K:H2O 1:3.5 puddle 60 3
3 AZ 400K:H2O 1:3.5 initial spray (12sec) + puddle cycles 50 3
4 AZ 400K:H2O 1:3.5 initial spray (12sec) + puddle cycles 60 3
5.5 AZ 400K:H2O 1:3.5 combined spray + puddle cycles 66 4
8 AZ 400K:H2O 1:3.5 combined spray + puddle cycles 66 5
15 AZ 400K:H2O 1:3.5 combined spray + puddle cycles 66 8


In case of non-complete PR dissolution with the standard development duration, please use any of the D4+(X)-400K sequences to add some development time.

  • Recommended developer: AZ 400K diluted 1 to 3.5 DI
  • Development time: 45″/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):

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