Forming multiple tsvs with different formation schemes

A method comprising:

• forming a first device die comprising:
• a semiconductor substrate;
• integrated circuit devices on the semiconductor substrate;
• an interconnect structure on the integrated circuit devices, wherein the interconnect structure comprises a plurality of metal layers;
• and
• a first through-silicon via (TSV) extending from a front surface of the semiconductor substrate into the semiconductor substrate;
• encapsulating the first device die in a gap-fill layer;
• performing a first planarization process on the first device die and the gap-fill layer until the first TSV is exposed;
• etching the first device die to form a TSV opening penetrating through the semiconductor substrate;
• filling the TSV opening with a conductive material;
• and
• performing a second planarization process on the conductive material until the first TSV is exposed, wherein a remaining portion of the conductive material is left to form a second TSV.

A method comprising:

• forming a device die comprising:
• forming integrated circuit devices on a semiconductor substrate;
• forming a first through-silicon via (TSV), with a portion of the first TSV in the semiconductor substrate, wherein the first TSV has a first wider end and a first narrower end narrower than the first wider end;
• forming an interconnect structure on the integrated circuit devices, wherein the interconnect structure comprises a first metal pad and a second metal pad, and wherein the first wider end contacts the first metal pad;
• and
• forming a second TSV having a second wider end and a second narrower end narrower than the second wider end, wherein the second narrower end contacts the second metal pad.