Using sacrificial material in additive manufacturing of polishing pads

A method of fabricating a polishing pad using an additive manufacturing system, the method comprising:

• depositing a first plurality of successive layers by droplet ejection onto a support, the first plurality of successive layers corresponding to a lower portion of the polishing pad;
• depositing onto the lower portion of the polishing pad a second plurality of successive layers by droplet ejection, wherein depositing the second plurality of successive layers includes
• dispensing by droplet ejection a polishing pad precursor to first regions corresponding to partitions of the polishing pad, and
• dispensing a sacrificial material to second regions that abut the first regions to form walls that line the vertical surfaces of the partitions, wherein gaps between adjacent partitions correspond to grooves in the polishing pad,
• wherein the first plurality of successive layers and the second plurality of successive layers providing a body and the first plurality of successive layers span the partitions and the grooves between the partitions;
• and
• removing the body from the support and removing the sacrificial material from the body to provide the polishing pad comprising the polishing surface having the partitions separated by the grooves.