Integrated method for etching of BLM titanium-tungsten alloys for CMOS devices with copper metallization

A method for fabricating a solder connector on a semiconductor device comprising the following steps:

• forming at least one dielectric layer over a doped semiconductor substrate,
• forming a hole through the dielectric layer down to the semiconductor substrate,
• forming a metal conductor structure in the hole,
• forming intermediate layers over the metal conductor structure and the dielectric layer,
• forming a hole through the intermediate layer down to the metal conductor structure,
• forming Ball Limiting Metallurgy (BLM) layers, having a top surface,
• the BLM layers including a titanium-tungsten (TiW) layer formed over the metal conductor structure and the dielectric layer with the remainder of the BLM layers being formed over the TiW layer,
• forming a mask over the top surface of the BLM layers with a patterning through hole located above the metal conductor structure exposing a portion of the surface of the BLM layers,
• plating a solder bump in the patterning hole over the BLM layers, removing the mask,
• wet etching away the BLM layers aside from the solder bump leaving a residual TiW layer over the dielectric layer until an initial end point has been reached,
• performing a dry etching process to remove the residual TiW layer aside from the solder bump,
• then ending the dry etching when an end point has been reached, and heating the solder bump in a reflow process to form a solder ball.

A method for fabricating a solder connector on a semiconductor device comprising the following steps:

• forming at least one dielectric layer over a doped semiconductor substrate,
• forming a hole through the dielectric layer down to the semiconductor substrate,
• forming a metal conductor structure in the hole,
• forming intermediate layers over the metal conductor structure and the dielectric layer,
• forming a hole through the intermediate layer down to the metal conductor structure,
• forming Ball Limiting Metallurgy (BLM) layers, having a top surface,
• the BLM layers including a titanium-tungsten (TiW) layer formed over the metal conductor structure and the dielectric layer with the remainder of the BLM layers being formed over the TiW layer comprising an intermediate BLM layer comprising a chromium/copper (Cr/Cu) layer and an upper BLM layer comprising a Cu layer, the ball limiting metallurgy (BLM) layers, having a top surface,
• forming a mask over the top surface of the BLM layers with a patterning through hole located above the metal conductor structure exposing a portion of the surface of the BLM layers,
• plating a solder bump in the patterning hole over the BLM layers, removing the mask,
• wet etching away the BLM layers aside from the solder bump leaving a residual TiW layer over the dielectric layer,
• performing the step of wet etching away the chromium/copper (Cr/Cu) layer and the Cu layer layers aside from the solder in a potassium sulfate solution leaving a residual TiW layer over the dielectric layer,
• then performing the step of wet etching TiW in a wet etching solution of hydrogen peroxide (H2O2), water (H2O), potassium sulfate (K2SO4), sulfuric acid (H2SO4), and EDTA (a salt of EthyleneDiamineTetraAcetic acid) continuing until only a predetermined thickness of TiW remains, at which time the wet etching of TiW is terminated by employing initial end point detection of the residual thickness of the TiW layer,
• followed by performing a dry etching process to remove the residual TiW layer aside from the solder bump, and
• then ending the dry etching when an end point has been reached, and
• heating the solder bump in a reflow process to form a solder ball.

A method for fabricating a solder connector on a semiconductor device comprising the following steps:

• forming at least one dielectric layer over a doped semiconductor substrate,
• forming a hole through the dielectric layer down to the semiconductor substrate,
• forming a metal conductor structure in the hole,
• forming intermediate layers over the metal conductor structure and the dielectric layer,
• forming a hole through the intermediate layer down to the metal conductor structure,
• forming Ball Limiting Metallurgy (BLM) layers, having a top surface,
• the BLM layers including a titanium-tungsten (TiW) layer formed over the metal conductor structure and the dielectric layer with the remainder of the BLM layers being formed over the TiW layer comprising an intermediate BLM layer comprising a chromium/copper (Cr/Cu) layer and an upper BLM layer comprising a Cu layer, the ball limiting metallurgy (BLM) layers, having a top surface,
• forming a mask over the top surface of the BLM layers with a patterning through hole located above the metal conductor structure exposing a portion of the surface of the BLM layers,
• plating a solder bump in the patterning hole over the BLM layers,
• removing the mask,
• wet etching away the BLM layers aside from the solder bump leaving a residual TiW layer over the dielectric layer,
• performing the step of wet etching away the chromium/copper (Cr/Cu) layer and the Cu layer layers aside from the solder in a potassium sulfate solution leaving a residual TiW layer over the dielectric layer,
• then performing the step of wet etching TiW in a wet etching solution of hydrogen peroxide (H2O2), water (H2O), potassium sulfate (K2SO4), sulfuric acid (H2SO4), and EDTA (a salt of EthyleneDiamineTetraAcetic acid) continuing until only a predetermined thickness of TiW remains, at which time the wet etching of TiW is terminated by employing end point detection of the thickness of the TiW layer,
• followed by performing a dry etching process to remove the residual TiW layer aside from the solder bump,
• then ending the dry etching when an end point has been reached,
• heating the solder bump in a reflow process to form a solder ball,
• determining when the end point of wet etching of the TiW layer is reached by monitoring the electrical impedance of the TiW layer until a predetermined minimum impedance is reached, and
• employing optical detection to determine when all of the TiW layer has been etched away and then terminating the etching operation by controlling a valve between the source of the etchant gases and the workpiece.