Multichip-module having an HDI and a temporary supporting substrate

A multichip module, comprising:

• at least one semiconductor chip;
• a chip-mounting substrate supporting the semiconductor chip, said chip-mounting substrate being constructed with at least one interlayer-insulating layer and at least one interconnection layer, at least one throughhole directing a treatment medium into a bonding layer connecting a supporting base and said chip-mounting substrate in order to melt the bonding layer, and a flat and smooth under-surface formed on said chip-mounting substrate due to melting of the bonding layer;
• and
• bumps interposed between said semiconductor chip and said chip-mounting substrate for fixing said semiconductor chip to said chip-mounting substrate and forming at least an electrical connection between said semiconductor chip and said interconnection layer of said chip-mounting substrate;
• wherein the supporting base supports said chip-mounting substrate during information of said chip mounting substrate, and after said chip-mounting substrate is formed, the supporting base is removed from said chip-mounting substrate by leading the treatment medium into said throughhole and melting the bonding layer, and subsequent to removal of the supporting base, said semiconductor chip is mounted on said chip-mounting substrate through said bumps to form the multichip module.