Semiconductor eutectic alloy metal (SEAM) technology for fabrication of compliant composite substrates and integration of materials

A method for forming a wafer of a compliant composite substrate, comprising the steps of:

• a) selecting as a first substrate material Ge having a melting point of TGe;
• b) selecting as a second substrate material Si having a melting point of TSi;
• c) selecting a joint metal with a melting point of Tm;
• wherein
• i) said joint metal and said first substrate material form a first eutectic alloy at a first eutectic temperature Teu1 while said joint metal and said second substrate material form a second eutectic alloy at a second eutectic temperature Teu2;
• and
• ii) TGe and TSi>Tm>Teu1 and Teu2;
• d) depositing said joint metal on a side of said first substrate material to form a first intermediate substrate;
• e) depositing said joint metal on a side of said second substrate material to form a second intermediate substrate;
• f) forming a substrate pair by combining said first and second intermediate substrates such that said sides of said first substrate material and said second substrate material having said joint metal on them are against each other;
• g) ramping a temperature of said substrate pair up to at least Tm, whereby said temperature passes through Teu1 and Teu2;
• and
• h) cooling, after step (g), said substrate pair to form said compliant composite substrate.

A method for forming a wafer of a compliant composite substrate, comprising the steps of:

• a) selecting a first substrate material having a melting point of Tm1;
• b) selecting a second substrate material having a melting point of Tm2;
• c) selecting a joint metal with a melting point of Tm;
• wherein
• i) said joint metal and said first substrate material form a first eutectic alloy at a first eutectic temperature Teu1 while said joint metal and said second substrate material form a second eutectic alloy at a second eutectic temperature Teu2;
• and
• ii) Tm1 and Tm2>Tm>Teu1 and Teu2;
• d) depositing said joint metal on a side of said first substrate material to form a first intermediate substrate;
• e) depositing said joint metal on a side of said second substrate material to form a second intermediate substrate;
• f) forming a substrate pair by combining said first and second intermediate substrates such that said sides of said first substrate material and said second substrate material having said joint metal on them are against each other;
• g) ramping a temperature of said substrate pair up to at least Tm, whereby said temperature passes through Teu1 and Teu2;
• and
• h) cooling, after step (g), said substrate pair to form said compliant composite substrate,
• wherein said first substrate material and said second substrate material are selected such that:
• αeff=(α1t1+α2t2)/(t1+t2)
• where αeff is a thermal expansion coefficient of at least one of said composite substrate and an epitaxial layer to be grown on said composite substrate, α1 is a thermal expansion coefficient of said first substrate material, α2 is a thermal expansion coefficient of said second substrate material, t1 is said first thickness of said first substrate material, and t2 is said second thickness of said second substrate material.