S1813 Spin Coating

This resist allows thicknesses from 1.2 to 2.0 µm. With Shipley 1813, 2 standard thicknesses have been chosen to be used in the MicroFab: 1.4 and 2.0 µm. Other thicknesses within the above mentioned range are available but proper recipe development has to be made. The spin speed is adjusted for each recipe so that the wanted thickness is obtained.

Introduction

The S1813 series resist is a standard novolak based positive photoresist that can be used in a wide variety of process flow to perform wet etch, dry etch and even lift-off processes. Its resistance depends on the etch process and can vary a lot.

This resist can be used in 3 tools: the Laurell Manual Spin Coater, the Site Service Coater/Dev and the EVG101 Spray coater.

 

Associated documents and references

- S1800 Shipley datasheet.

- Tool's manuals: Laurell Manual Spin Coater, the Site Service Coater/Dev and the EVG101 Spray coater.

Safety considerations

The S1813 resist is a solvent based resist so all precaution relative to solvent manipulation are needed.

Processing spin coaters

Spin curve for Site coater

1813 Shipley resist has been coated on wafers using different speeds and baked at 115°C for 60s. Results are reported in the following chart. In the top right corner of this chart, there is the formula of the curve that best fits the data points.

1813 spin curve

 

Depending on the desired thickness, choose the appropriate speed. the following parameters are starting point for general use of S1813 resist. For high resolution lithography, dose optimization might be needed.

Thickness Speed SoftBake UV dosage in EVG620 Development in MF319 Hardbake
1.4µm 3915rpm 60s @ 115°C 60mJ/cm2 45s 90s @ 90°C
2.0µm 1950rpm 60s @ 115°C 90mJ/cm2 60s 90s @ 90°C

Statistics on the Site Coater

Here follows the uniformity and thickness characterization for 1.4µm coating for both 4 and 6 inch wafers.
Mean thickness: the average of the obtained thickness at each coating. 14048 A Angstrom
Wafer-to-wafer thickness uniformity: standard thickness deviation observed wafer-to-wafer: 1.3%
Mean thickness uniformity: average of thickness uniformity obtained on each wafer: 0.43%

Process for Laurell coater

Coating conditions are:

- spread at 500 rpm for 5 s with acceleration of 1305 rpm/s

- spin between 1500 and 5000 rpm for 30 s with acceleration of 1305 rpm/s

- bake at 115 °C for 1 min

The following table gives thicknesses vs. speed measured at the center of silicon samples of 1x1 cm².

Spin speed (rpm) Thickness measured with mechanical profiler (µm) Thickness measured with ellipsometer (µm) Thickness measured with reflectometer (µm)
1500 2.38 2.37 2.35
2000 2.01 2.00 2.00
3000 1.62 1.62 1.63
4000 1.43 1.43 1.44
5000 1.30 1.31

1.31