Patent EP-3772088-A2 (EP)
Inventor: LOWER NATHAN
IPC: H01L21/67
Filed: 2020-08-03
Abstract: A method for fabricating semiconductor die (120) with die-attach preforms (104, 104a-f) includes: applying an uncured die-attach paste material to a surface of a forming substrate (102) (e.g., made of a hard material, such as a ceramic material or alumina) to form (202) one or more die-attach preforms (104, 104a-f), the surface of the forming substrate (102) being formed from a hydrophobic material (e.g., Teflon or other fluoropolymer coating); curing (e.g., drying) (204) the one or more die-attach preforms (104, 104a-f); performing (206) one or more planarization processes on the one or more die-attach preforms (104, 104a-f), e.g. by a precision lathe, a precision mill, or a diamond turning machining tool; coupling (208) a first surface of a semiconductor die (120) to a handling tool (106); and bonding (218) a second surface of the semiconductor die (120) to at least one die-attach preform (104, 104a-f) of the one or more die-attach preforms (104, 104a-f) to transfer it to the semiconductor die (120), e.g. upon applying heat to with one or more heating elements (108) disposed within the handling tool (106). The method may further include coupling the semiconductor die (120) to a product substrate by bonding (220) the die-attach preform (104, 104a-f) to the product substrate, e.g. by applying heat with one or more heating elements (108) disposed within the handling tool (106). The one or more die-attach preforms (104, 104a-f) may comprise one or more sintered silver or gold-tin eutectic preforms. The at least one die-attach preform (104, 104a-f) may substantially conform to a shape and size of the second surface of the semiconductor die (120). The uncured die-attach paste material may be applied to the forming substrate (102) using a stencil. The first surface of the semiconductor die (120) may be coupled to the handling tool (106) with a suction force applied through a vacuum port (128) disposed in a surface (124) of the handling tool (106) with one or more vacuum sources (110). A graphite pad (126) may be formed (210) on a surface (124) of the handling tool (106), for coupling (212) to a first surface of the semiconductor die (120), to provide a soft but compliant surface which may prevent damage (e.g., scratching, cracking, passivation) to the semiconductor die (120) and may help to evenly distribute pressure and bonding forces across the first surface of the semiconductor die (120). The graphite pad (126) may include one or more carve-outs for receiving one or more structures disposed on the first surface of the semiconductor die (120) when coupling the semiconductor die (120) to the graphite pad (126). The handling tool (106) may be actuated to apply a first pressure between the graphite pad (126) and the first surface of the semiconductor die (120), and to apply a second pressure between the second surface of the semiconductor die (120) and the at least one die-attach preform (104, 104a-f). The surface (124) of the handling tool (106) configured to be coupled to the graphite pad (126)/semiconductor die (120) may be coated with a non-stick, hydrophobic coating (e.g., fluoropolymer coating, Teflon). The graphite pad (126) on a surface (124) of the actuatable handling tool (106) may be formed by applying a metal material to a graphite sheet to form a graphite pad (126) and diffusion bonding the graphite pad (126) to the surface (124) of the actuatable handling tool (106). Coupling (212) the graphite pad (126) to the first surface of the semiconductor die (120) may comprise forming (210) the graphite pad (126) on the surface (124) of the actuatable handling tool (106), wherein the graphite pad (126) covers at least one portion of a vacuum port (128) disposed in a surface (124) of the actuatable handling tool (106); removing a portion of the graphite pad (126) which covers the at least one portion of the vacuum port (128) to create one or more apertures within the graphite pad (126); applying (214) a suction force through the vacuum port (128) and through the one or more apertures of the graphite pad (126) with one or more vacuum sources (110); and coupling (216) the first surface of the semiconductor die (120) to the handling tool (106) via the suction force. The graphite pad (126) may be sized such that it substantially conforms to a shape and/or size of a selected semiconductor die (120).