Patent EP-4109516-A2 (EP)
Inventor: EID FERAS
IPC: H01L21/60
Filed: 2022-05-03
Abstract: A multi-die module comprises: a first die (705) comprising a first pedestal (307, 407, 507, 707), a plateau (308, 408, 508) around the first pedestal (307, 407, 507, 707), and a stub (330, 430, 530, 630, 730) extending up from the plateau (308, 408, 508); and a second die (420, 520, 720) comprising a second pedestal (422, 522, 722), where the second pedestal (422, 522, 722) is attached to the first pedestal (307, 407, 507, 707). The stub (330) may be a continuous ring that extends around the first pedestal (307), wherein an inner diameter of the continuous ring may be larger than a width of the second pedestal. Alternatively, a plurality of stubs (330) may be provided on the plateau (308, 408, 508), wherein the stubs (330) may be post-like structures or may be elongated. The multi-die module may further comprise a second stub (530 1 ) on a surface of the first die between the first pedestal (507) and the plateau (508), wherein the second pedestal (522) has a chamfered corner (575) that is adjacent to the second stub (530 1 ), wherein a maximum width of the second pedestal (522) may be greater than a distance between the stub (530 2 ) and the second stub (530 1 ), wherein the die (520) that is placed onto the first pedestal (507) has a matching chamfer so that the die (520) can only fit through the stubs (530) when having a matching rotational orientation of its chamfered surface with the chamfered surface (575) of the first pedestal (507). Orientation differentiation is thus provided by the use of mechanical features (530). The stub (630) may have a top surface (631) that is domed, flat, v-grooved, u-grooved, or pointed. A hydrophilic layer (311, 411, 511, 426, 526) may be present on the first pedestal (307, 407, 507, 707) and on the second pedestal (422, 522, 722). A hydrophobic layer (309, 409, 509) may be present on sidewalls of the first pedestal (307, 407, 507, 707), on a surface of the first die (705) between the first pedestal (307, 407, 507, 707) and the plateau (308, 408, 708), and on the plateau (308, 408, 708). 
     A method of attaching dies (420 A , 420 B ) to a wafer (405) comprises: attaching a first die (420 A ) to a first pedestal (407 A ) on the wafer (405), wherein the first pedestal (407 A ) is surrounded by one or more first stubs (430 A ), and wherein the first pedestal (407 A ) has a first width; and attaching a second die (420 B ) to a second pedestal (407 B ) on the wafer (405), wherein the second pedestal (407 B ) is surrounded by one or more second stubs (430 B ), and wherein the second pedestal (407 B ) has a second width that is smaller than the first width of the first pedestal (407 A ). The second stubs (430 B ) prevent larger dies (420 A ) from bonding to smaller pedestal locations (407 B ) on the wafer (405). In order to prevent smaller dies (420 B ) from inadvertently attaching to larger pedestals (407 A ) on the wafer (405), the method may start with the attachment of the largest dies (420 A ) and then move to progressively smaller dies (420 B ), ensuring that the larger bonding locations are already occupied before smaller dies (420 B ) are introduced. Therefore, size differentiation is provided by the use of mechanical features (430) on the wafer (405). The first die (420 A ) may be attached to the first pedestal (407 A ) by hydrophilic bonding and the second die (420 B ) may be attached to the second pedestal (407 B ) by hydrophilic bonding in a self-assembly process, wherein a liquid (315, 415) (e.g., water) may be disposed on the hydrophilic layer (311, 411, 511) before the die (420 A , 420 B , 520) is brought into close proximity with the wafer (305, 405, 505), and the liquid (315, 415) exerts an adhesive force that brings the die (420 A , 420 B , 520) into proper alignment with the wafer (305, 405, 505). The liquid (315, 415) may then be removed (e.g., evaporated) and a bonding process such as a hybrid bonding process may permanently secure the die (420 A , 420 B , 520) to the wafer (305, 405, 505).