AZ 10XT-60

! 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 recommended exposure doses.
  • 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-60 spincurve is shown below, as well as process details for both automatic and manual coating.

Available thicknesses: 5 um / 8 um / 10 um / 15 um / 20 um

Available databases (default: 4inch, check with the staff for 6inch):

  • AZ10XT_5to20um_Std_Dehydrate_x_y
  • AZ10XT_5to20um_Std_NoDehydrate_x_y (for HMDS-treated wafers)
  • AZ10XT_5to20um_HighTopo_Dehydrate_x_y (for wafers with topography, spiral dispense)
  • AZ10XT_5to20um_HighTopo_NoDehydrate_x_y
  • AZ10XT_5to20um_GlassOnly_Dehydrate_x_y (for transparent wafers)
  • AZ10XT_5to20um_GlassOnly_NoDehydrate_x_y
  • AZ10XT_5to20um_Quartz_Dehydrate_x_y (for quartz, stacked glass-silicon wafer or SOI wafers. Softbake temperature is 125°C.)
  • AZ10XT_5to20um_Quartz_NoDehydrate_x_y

Availables recipes:

Recipe name Spin speed [rpm] Softbake time [mm:ss] PR thickness [µm]
C4_D_10XT_5u_EC 6800 04:00 5
C4_D_10XT_8u_EC 2800 05:00 8
C4_D_10XT_10u_EC 1800 06:00 10
C4_D_10XT_15u_EC 920 07:00 15
C4_D_10XT_20u_EC 720 08:00 20

Spin time is 100s, followed by 60 seconds stress relaxation at 0 RPM. Softbake is performed at 300µm proximity. Softbake temperature is 112°C for all options except for “Quartz” (125°C).

  • 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:

Good result 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 AZ 10XT-60 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]+++
5 360 330 240
8 460 420 340
 10 555 470 390
 15 660 580 490
 20 800 690 580

* 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 organic solution based upon KOH. Development with AZ 400K will result in a sharper edge profile.

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):

Development recipes for AZ 10XT-60 (identical for all are AZ10XT_5to20um_*  databases) are listed below:

Recipe name PR thickness [µm] Total contact time [s]
D4_N_10XT_5u_PUD
4…6
140
D4_N_10XT_8u_PUD
7…9
210
D4_N_10XT_10u_PUD
9…12
250
D4_N_10XT_15u_PUD
12…17
370
D4_N_10XT_20u_PUD
17…22
490

The development consists in short spray dispense strokes followed by puddle (no rotation) / rinse development cycles. No softbake is applied in order to preserve vertical PR side walls.

Development sequences for AZ 10XT-60  are listed below:

Sequence Number Recipe name PR thickness [µm] Total contact time [s]
0949
D4_N_10XT_5u_PUD
5
240
0950
D4_N_10XT_8u_PUD
8
342
0951
D4_N_10XT_10u_PUD
10
426
0952
D4_N_10XT_15u_PUD
15
564
0953
D4_N_10XT_20u_PUD
20
672

The development combines spray and puddle methods with intermediates spin-clean steps. No Softbake is applied in order to preserve vertical PR side walls.

  • Recommended developer: AZ 400K diluted 1 to 3.5 DI
  • Development time: 45″/um
  • Rinse: H2O 1min

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