Detecting completion of electroless via fill

A method for visually indicating the completion of electrolessly plating metal into a via in a dielectric, comprising:

• providing a dielectric;
• depositing a non-autocatalytic detection mask with an opening on a surface of the dielectric;
• the dielectric;
• providing an autocatalytic material in the via;
• electrolessly plating an electrically conductive metal through the detection mask opening into the via, wherein the metal begins to fill the via but fails to plate on the detection mask until metal filled in the via is connected to the detection mask;
• and
• continuing to electrolessly plate the metal after the metal filled in the via is connected to the detection mask so that the metal plates to and covers the entire top surface of the detection mask, thereby providing a visual indication that the via is filled with metal and the electroless plating can be discontinued.

A method for providing visual detection of the completion of electrolessly plating a metal pillar into a via in a dielectric, comprising the following steps in the sequence set forth:

• providing a dielectric with a top surface;
• depositing a non-autocatalytic detection mask layer on the dielectric top surface;
• forming a plurality of openings in the detection mask, wherein each opening exposes a separate portion of the dielectric top surface;
• etching the exposed portions of the dielectric to form a plurality of vertical vias in the dielectric;
• providing an autocatalytic material in each of the vias;
• electrolessly plating an electrically conductive metal through the detection mask openings into the vias, wherein the metal partially fills the vias but fails to plate to or cover the detection mask;
• continuing to electrolessly plate the metal through the detection mask openings into the vias until the metal fills a via to form a metal pillar which contacts the detection mask, thereby allowing the metal to begin to plate to the detection mask;
• continuing to electrolessly plate the metal until the metal fills all the vias and all the detection mask openings and covers the entire top surface of the detection mask with a uniform layer, thereby allowing visual detection that uniform metal pillars have been formed;
• and
• discontinuing the electroless plating as a result of the visual detection.

A method for indicating the completion of electrolessly depositing metal into a via, comprising:

• providing a via in a dielectric;
• providing an autocatalytic material in the via;
• providing over the dielectric an electrically conductive non-autocatayltic detection mask with an opening above the via;
• electrolessly depositing an electrically conductive metal into the via wherein the metal begins to deposit on the autocatalytic material and fill the via but fails to deposit on the detection mask;
• and
• continuing the electroless deposition until the metal filled in the via electrically connects the autocatalytic material to the detection mask, at which time the metal begins to deposit a uniform layer over the entire detection mask, thereby providing a visual indication that the via is filled with metal and the electroless deposition can be discontinued.

A method for electronically detecting the completion of electrolessly depositing metal into a via, comprising:

• providing a via in a dielectric;
• providing an autocatalytic material in the via;
• providing over the dielectric an electrically conductive non-autocatayltic detection mask with an opening above the via;
• providing an electronic device which is responsive to a change in the electrochemical potential of the detection mask;
• electrolessly depositing an electrically conductive metal into the via wherein the metal begins to deposit on the autocatalytic material and fill the via but fails to deposit on the detection mask;
• continuing the electroless deposition until the metal filled in the via electrically connects the autocatalytic material to the detection mask thereby changing the electrochemical potential of the detection mask;
• and
• detecting the change in electrochemical potential by the electronic device, whereby the device sends an electrical signal to indicate via fill is completed.