Method for forming conductive bumps by performing a reflow process

A method, comprising:

• forming alloy patterns comprising Sn and X on a first structure, wherein X represents bismuth or indium;
• forming alloy patterns comprising Sn and Ag on a second structure;
• performing a first thermal process to bond the alloy patterns comprising Sn and X and the alloy patterns comprising Sn and Ag, wherein the alloy patterns comprising Sn and X and the alloy patterns comprising Sn and Ag remain solid state during the first thermal process;
• and
• after performing the first thermal process, performing a second thermal process to convert the alloy patterns comprising Sn and X and the alloy patterns comprising Sn and Ag into conductive bumps, wherein a first process temperature of the first thermal process is lower than a second process temperature of the second thermal process.

A method, comprising:

• forming Sn-Cu alloy patterns on a first structure;
• forming Sn-Ag alloy patterns on a second structure;
• forming Sn-X alloy patterns between the Sn-Cu alloy patterns and the Sn-Ag alloy patterns, wherein X represents bismuth or indium;
• pre-heating the Sn-Ag alloy patterns, the Sn-X alloy patterns and the Sn-Cu alloy patterns, wherein the Sn-X alloy patterns remain solid state during pre-heating the Sn-Ag alloy patterns, the Sn-X alloy patterns and the Sn-Cu alloy patterns;
• and
• after pre-heating the Sn-Ag alloy patterns, the Sn-X alloy patterns and the Sn-Cu alloy patterns, reflowing the Sn-Ag alloy patterns, the Sn-X alloy patterns and the Sn-Cu alloy patterns to form solder joints between the first structure and the second structure.