Method of sintering die to substrate and tack-bonding die to substrate and power module

Abstract

The invention relates to a method of sintering a die to a substrate and tack-bonding the die to the substrate and a power module. A die attachment process is disclosed that yields a bond strength sufficient to hold a die on a substrate when the die is processed prior to permanent attachment. The die attach process includes forming a locking feature in a metal layer of a substrate, thereby enhancing bonding at a die-substrate interface. The locking feature may include a plurality of cavities or slots formed in the metal layer of the substrate. The cavity and slot may increase the surface area and provide an anchor point for a die attach film placed between the die and the substrate.

Description

Technical Field

[0001] The present invention relates to methods of sintering a die to a substrate and contact bonding a die to a substrate and an electronic module, and more particularly to a method for attaching a die to a substrate. Background Art

[0002] Packages for power electronics (e.g., power modules, solar inverters, motor controllers, etc.) may include a die to be attached to a substrate. The substrate may be implemented using direct bond copper (DBC) or active metal brazing (AMB) substrates because they have excellent thermal conductivity and electrical insulation. The die may be attached to these substrates using a sintering process, which may aid in heat conduction. Careful alignment of the die on the substrate may be required before and after the sintering process. Summary of the invention

[0003] Attaching the die to the substrate may include assembling a stack of the die and substrate. The stack may then be transported to a machine where heat and pressure may be used to complete the attachment of the die to the substrate. The stack may be temporarily attached (i.e., tacked) in place prior to transport in order to prevent the stack from being damaged or destroyed by any shock and / or vibration while in transit. The present disclosure describes a device for strengthening a tacked attachment so that it can better withstand the shock / vibration associated with transport.

[0004] In some aspects, the technology described herein relates to a method for sintering a die to a substrate, the method comprising: forming a plurality of locking features in a metal layer of the substrate; laminating a die transfer film to the die; placing the die and the die transfer film on the substrate to form a stack structure, the stack structure including the die transfer film directly between the metal layer and the die; adhering the stack structure to form a touch-bonded stack structure; and sintering the touch-bonded stack structure so that the die is bonded to the substrate.

[0005] In one possible implementation, the plurality of locking features are cavities, wherein each cavity has a depth in the range of 10 microns to 20 microns, and each cavity has an edge that rises less than 10 microns above the surface of the metal layer.

[0006] In another possible implementation, the plurality of locking features are slots in a crosshatch pattern. The crosshatch pattern may have a first period of about 1000 microns in a first direction and a second period of about 1000 microns in a second direction. Each slot may have a width in a first range of 10 microns to 20 microns and a depth in a second range of 10 microns to 20 microns. Each slot may also have an edge that is elevated above the surface of the metal layer. The height of the edge may be maintained less than 10 microns so that the edge does not crack and / or damage the die (e.g., during sintering).

[0007] In some aspects, the technology described herein relates to a power module comprising: a substrate comprising a plurality of locking features in a metal layer of the substrate; and a die comprising a circuit for the power module, the die being attached to the substrate using a die attach process, the die attach process comprising: laminating a die transfer film to the die; placing the die and the die transfer film on the substrate to form a stacked structure comprising the die transfer film directly between the metal layer and the die; adhering the stacked structure to form a touch-bonded stacked structure; and sintering the touch-bonded stacked structure so that the die is bonded to the substrate.

[0008] In one possible implementation, the thickness of the die transfer film is greater than the depth of the plurality of locking features, so that in the stacked structure, the die transfer film is consistent with the plurality of locking features on a first side facing the metal layer, but not consistent with the plurality of locking features on a second side facing the die.

[0009] In some aspects, the technology described herein relates to a method for touch bonding a die to a substrate, the method comprising: forming a plurality of locking features in a metal layer of the substrate; laminating a die transfer film to the die; placing the die and the die transfer film on the substrate to form a stack structure, the stack structure including the die transfer film directly between the metal layer and the die; applying a force to the die so that the stack structure is pressed together for a thermal touch bonding period; and heating the substrate so that the temperature of the stack structure increases during the thermal touch bonding period, and the die is touch bonded to the substrate to form a touch-bonded stack structure at the end of the thermal touch bonding period.

[0010] In one possible implementation of the method for touch bonding a die to a substrate, the touch bonded stack is shipped, and the plurality of locking features result in a bonding strength of the touch bonded stack sufficient to hold the touch bonded stack together during shipping.

[0011] The foregoing illustrative summary, as well as other exemplary objects and / or advantages of the present disclosure, and implementations are further explained in the following detailed description and its accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 is a perspective view of a stacked structure for an electronic package according to a possible implementation of the present disclosure.

[0013] Figure 2A A die having alignment according to possible implementations of the present disclosure Figure 1 Top view of the stacked structure shown.

[0014] Figure 2B is a possible embodiment of the present disclosure according to which the misaligned die Figure 1Top view of the stacked structure shown.

[0015] Figure 2C is a possible specific implementation according to the present disclosure that lacks a die Figure 1 Top view of the stacked structure shown.

[0016] Figure 3 is a side cross-sectional view of a stacked structure during a process for attaching a die to a substrate according to a possible implementation of the present disclosure.

[0017] Figure 4 is a side cross-sectional view of a die-substrate interface including locking features according to a possible implementation of the present disclosure.

[0018] Figure 5 is a perspective view of a substrate having a plurality of locking features in a metal layer according to a first possible implementation of the present disclosure.

[0019] Figure 6 The specific implementation according to the present disclosure is shown Figure 5 A top view of a portion of the bonding area is shown, including an inset showing a side view of a representative cavity.

[0020] Figure 7 is a perspective view of a substrate having a plurality of locking features in a metal layer according to a second possible implementation of the present disclosure.

[0021] Figure 8 The specific implementation according to the present disclosure is shown Figure 7 A top view of a portion of the bonding area is shown, including an inset showing a side view of a representative slot.

[0022] Fig. 9 is a flow chart of a method for sintering a die to a substrate according to a specific implementation of the present disclosure.

[0023] The components in the drawings are not necessarily drawn to scale relative to each other. Like reference numerals indicate corresponding parts throughout the several views of the drawings. DETAILED DESCRIPTION

[0024] An electronic component (e.g., a power module) may include a die connected to a substrate using a sintering process. Although there are many materials to choose from, the electronics industry tends to use materials with lower cost (e.g., lower cost than gold (Au)) and lower environmental impact (e.g., less impact than lead (Pb)). For example, silver (Ag) in the form of a paste or film may be applied between the electroplated surface of the die and the metal layer of the substrate to form a stacked structure. The stacked structure may be loosely adhered (i.e., touch-bonded) in place to prepare it for final attachment via sintering. After sintering, subsequent soldering processes may be performed to connect the sintered stacked structure in an electronic package. For these subsequent soldering processes, appropriate alignment of the die may be required.

[0025] One technical problem with the above touch bonding method is that the touch bonded stack may be held together too loosely to withstand handling. For example, transporting the touch bonded stack prior to sintering may generate shock / vibration that may cause the die to shift. The die may thus be lost or misaligned, which may lead to failure of the electronic component. When the electronic component has a high cost, such as is typically the case with power modules, it may be desirable to reduce the number of failures.

[0026] Power modules may use dies made from silicon carbide (SiC) materials / processes in order to handle the high temperatures and voltages associated with their operation. SiC may be more expensive than other technologies (e.g., Si). Therefore, in order to minimize the failure of these electronic components, the present disclosure describes systems and methods for strengthening the touch-bond stack structure to enable it to withstand the forces during transportation without shifting. The strengthened touch-bond may have the technical effect of improving the production yield of the power module.

[0027] Figure 1 is a perspective view of a stacked structure for a power module according to a possible implementation of the present disclosure. The stacked structure can be used for power modules configured for high voltage (e.g., >10V) and high temperature (e.g., >100°C), and therefore may require materials suitable for such operation (e.g., ceramic, SiC, etc.).

[0028] The stacked structure 100 may include a substrate 110 having a metal layer (i.e., a top metal layer 111) mechanically coupled to a first surface (i.e., a top surface) of an insulating layer 112. The insulating layer 112 may be a ceramic (e.g., aluminum oxide, aluminum nitride, silicon nitride) according to its electrical insulation and thermal diffusion properties. In some implementations, the substrate 110 further includes a second metal layer (i.e., a bottom metal layer 113) mechanically coupled to a second surface (i.e., a bottom surface) of the insulating layer 112.

[0029] Bonding or brazing may be used to attach the metal layer to the insulating layer 112. Bonding processes for attaching metal layers produce direct bond metal (DBM) substrates (e.g., direct bond copper (DBC) substrates), while brazing processes for attaching metal layers produce active metal braze (AMB) substrates.

[0030] The top metal layer 111 and the bottom metal layer 113 may be copper (Cu), which may be electroplated to aid in die attach. For example, the copper metal layer may be plated with silver to match a silver-based die attach paste (DAP) or a silver-based die transfer film (DTF). The top metal layer 111 and / or the bottom metal layer 113 of the substrate 110 may be etched or otherwise segmented to form traces 115 to interconnect the circuit to other devices / components. For example, the metal layer may be etched to form pads that may be wire-bonded to a lead frame of a chip package (not shown).

[0031] As shown, the die 120 may be placed in a bonding area 130 on the top metal layer 111 of the substrate 110 to form a stacked structure 100. In one possible implementation, the die 120 may include an integrated circuit (IC) for a power module, such as an insulated gate bipolar transistor (IGBT) or a power metal oxide semiconductor field effect transistor (power MOSFET). Although the ceramic substrate material and the SiC die material are described in detail because they are suitable for power modules, it should be noted that the disclosed technology can be used with other materials and for other electronic components. For example, the die may be another material, such as silicon (Si), gallium arsenide (GaAs), or glass.

[0032] In order for the die 120 to properly contact the traces and / or wires, the die may need to be properly aligned within the bonding area 130. Automation may be used to accurately pick and place the die 120 in the bonding area 130. However, in some cases, the die may become misaligned within the bonding area 130 or may completely separate from the top metal layer 111.

[0033] Figure 2A Yes Figure 1 A top view of stacked structure 100 is shown with the die aligned with bonding region 130 (ie, aligned die). An aligned die can be characterized as having edges (ie, sides) aligned with (ie, parallel to, flush with) edges (ie, sides) of bonding region 130. Figure 2B yes Figure 1 A top view of the stacked structure is shown with the die misaligned with the bonding area 130 (i.e., a misaligned die). A misaligned die can be characterized as having edges (i.e., sides) that are not aligned with (i.e., not parallel to, not flush with) the edges (i.e., sides) of the bonding area 130. Figure 2C yes Figure 1A top view of the stacked structure is shown with a die missing (ie, a missing die) in the bonding area 130. The die may be lost by becoming separated from the substrate 110 and falling off.

[0034] Misaligned dies and / or missing dies may be caused by shock and / or vibration. Shock / vibration may be associated with movement of stacked structure 100. For example, the movement may be caused by transporting stacked structure 100 between machines in a production environment. For example, stacked structure 100 may be transferred from a pick and place machine configured to place die 120 on substrate 110 to a sintering machine configured to permanently attach die 120 to substrate 110.

[0035] Misaligned dies or missing dies may cause component failure in a production environment. For example, a misaligned die that is permanently attached by sintering may not properly connect with pads, traces, and / or wires of a substrate. Therefore, to avoid misaligned or missing die situations, the die may be temporarily attached (i.e., adhered, touch-bonded) in place (i.e., in bonding area 130) to allow for handling (e.g., moving, shipping) before it is permanently attached. Adhering die 120 for shipping may be performed using a thermal touch-bonding process.

[0036] Figure 3 3 is a side cross-sectional view of a stacked structure during a process for attaching a die to a substrate according to a possible implementation of the present disclosure. A process for attaching (i.e., touch bonding) a die to a substrate (i.e., a thermal touch bonding process) may include forming a stacked structure 300 as shown. The stacked structure 300 may include a die transfer film 310 (DTF) positioned between (e.g., directly between) the die 120 and a metal layer (e.g., top metal layer 111) of the substrate 110.

[0037] The die transfer film 310 may have a size and shape that substantially matches (e.g., <1% difference) the size and shape of the die 120. In one possible implementation, the die transfer film is laminated to a surface (e.g., bottom surface) of the die 120 before forming (i.e., assembling) the stacked structure. The lamination process may include cutting the die transfer film 310 to fit the die 120. The die transfer film 310 may include metal nanoparticles in a matrix. For example, the die transfer film 310 may include silver (Ag) nanoparticles in an adhesive matrix. In this case, the top metal layer 111 may be silver plated to aid in the sintering process.

[0038] The process for touch bonding the die 120 to the top metal layer 111 may also include applying heat 330 to the stacked structure 300. In one possible implementation, applying heat 330 may include positioning a first heat source at the bottom metal layer 113. For example, the stacked structure 300 may be placed on a substrate 340, which may be heated to a first temperature so as to indirectly heat the die transfer film 310 from a first direction. In one possible implementation, applying heat 330 to the stacked structure 300 may also include positioning a second heat source at the top surface of the die 120. For example, a head 350 for picking up and placing the die 120 may be heated to a second temperature so as to heat the die transfer film 310 from a second direction. The first temperature and the second temperature may be controlled so as to raise the temperature of the die transfer film 310 to a hot touch bonding temperature and maintain the temperature at the hot touch bonding temperature for a hot touch bonding period before allowing the die transfer film 310 to cool.

[0039] In one possible implementation, the process for touch bonding the die 120 to the top metal layer 111 may also include applying pressure to the stacked structure 300. In one possible implementation, applying pressure may include pressing (e.g., moving) the head 350 downward on the die 120 so that the first force 321 is applied downward on the top surface of the die 120. The substrate 340 may be fixed (or pressed) so that the second force 322 is applied upward on the bottom metal layer 113. The net result of the first force and the second force is to squeeze the die transfer film 310 between the die 120 and the top metal layer 111. For example, the stacked structure may be squeezed together by lowering the head 350 onto the die 120 while the stacked structure rests on the base plate 340. The first force 321 and the second force 322 may be applied during a hot touch bonding period.

[0040] The temperature and pressure may be increased during the hot touch bonding period and decreased after the hot touch bonding period. For example, at the end of the hot touch bonding period, the pressure on the stack is released and the stack is cooled. After cooling, the die 120 may be adhered (i.e., bonded) to the top metal layer 111 via the die transfer film 310. The strength of the bond (i.e., the bond strength) of the adhesive connection corresponds to the magnitude of the force required to break the adhesive connection. In other words, when the force applied to the stack is less than the bond strength, the bond strength may keep the stack intact. Because the heat / pressure applied during the hot touch bonding process may be less than the heat / pressure applied during the sintering process, the bond strength produced by the hot touch bonding process is not as high as the bond strength produced by the sintering process. The bond strength may be made stronger (i.e., increased) by using locking features formed in the metal layer of the substrate.

[0041] Figure 44 is a side cross-sectional view of a die-substrate interface including a locking feature according to a possible specific implementation of the present disclosure. As shown, the locking feature 410 is included in the metal layer 411 of the substrate and interrupts the plane 401 defined by the surface of the metal layer 411. Therefore, the locking feature 410 can make the surface of the metal layer 411 non-planar and can increase the surface area of ​​the metal layer 411. The locking feature 410 can actually have any size and shape, as long as it interrupts the plane 401 (i.e., the surface) of the metal layer. For example, the locking feature 410 can define a bulge on the surface of the metal layer 411 that rises above the plane 401, or can define a depression on the surface of the metal layer 411 that descends below the plane 401. Therefore, the die-substrate interface including the locking feature can better resist the force 444 in the direction parallel to the plane 401 than the die-substrate interface without the locking feature.

[0042] Figure 4 The locking feature 410 shown in FIG. 4 is a cross-section of a slot (i.e., groove, notch, etc.) or cavity (i.e., pit, concave surface, cavity, pit) formed in the top surface of the metal layer 411. The locking feature 410 has a volume corresponding to the amount of metal layer 411 removed to form the locking feature. The volume is defined by the depth 420 of the locking feature 410 from the surface of the metal layer 411 (i.e., plane 401). In one possible implementation, the depth 420 of the locking feature is in the range of 10 microns to 20 microns. The volume is also defined by a width 430, which can be in the range of 10 microns to 20 microns.

[0043] The above-described hot touch bonding process may soften and compress the die transfer film 310 during the hot touch bonding period. Thus, after cooling, 310 may partially fill or completely fill the volume of the locking feature 410. Increased bonding area and grip (i.e., anchoring) provided by the locking feature 410. The depth 420 of the locking feature 410 and the thickness 435 of the die transfer film 310 may be selected so that during and after the hot touch bonding process, the die transfer film 310 fills the locking feature 410 while providing a flat surface 402 for the die 120. In other words, the die transfer film may have a thickness 435 greater than the depth 420 so that (in the stacked structure) the die transfer film 310 is consistent with the locking feature on a first side (facing the metal layer 411) but not on a second side (facing the die 120). The flat surface 402 of the die transfer film 310 on the side facing the die 120 may help prevent cracks from occurring in the die 120 . Figure 4 The locking feature shown may be one of a plurality of similar (ie, identical) locking features on the surface of the substrate.

[0044] Figure 5is a perspective view of a substrate 500 having a plurality of locking features in a metal layer 511 according to a first possible implementation of the present disclosure. The locking features are a plurality of cavities. In one possible implementation, the plurality of cavities are designed to have the same size and shape. The plurality of cavities are arranged in a certain pattern on the metal layer 511. In one possible implementation, the pattern of the cavities is random. In one possible implementation, the pattern of the cavities is asymmetric in two dimensions. In one possible implementation, the pattern of the cavities is repeated in two dimensions with the same spatial frequency in each dimension. In one possible implementation, the pattern of the cavities is repeated in two dimensions with a different spatial frequency in each dimension. In one possible implementation, the pattern of the cavities is repeated in one dimension. In one possible implementation, the pattern of the cavities covers an entire portion of the metal layer 511. In one possible implementation, the pattern of the cavities covers a portion of the metal layer 511. For example, as Figure 5 As shown, the pattern of cavities repeats in two dimensions (with the same spatial frequency) and covers a bonding region 530 of a metal layer 511 of a substrate 500 where the metal layer 511 is coupled to an insulating layer 512. In other words, the cavities may be located in the bonding region 530 of the metal layer 511 but not in other regions of the metal layer 511.

[0045] Figure 6 The specific implementation according to the present disclosure is shown Figure 5 A top view 600 of a portion of the bonding area 530 is shown, and includes an inset 601 showing a side view of a representative cavity. As shown in the top view 600, the cavities are formed to have a repeating pattern having a first spatial period 610 in a first direction and a second spatial period 620 in a second direction, the first spatial period and the second spatial period being the same. In one possible implementation, forming the plurality of locking features includes stamping a metal layer to form the cavities. In another possible implementation, forming the plurality of locking features includes laser etching a metal layer to form the cavities.

[0046] As shown in inset 601, each cavity in the plurality of cavities may have a depth 630 in the range of 10 microns to 20 microns. The process of forming the cavity may produce an edge 640 that is raised above the surface of the metal layer by a height 650. This height 650 may be made less than 10 microns to prevent cracking of the die when the die is pressed against the surface 660 of the metal layer during a thermal bonding process or a sintering process.

[0047] Figure 77 is a perspective view of a substrate 700 having a plurality of locking features in a metal layer 711 on the substrate, wherein the metal layer 711 is coupled to an insulating layer 712. The locking features are a plurality of slots. The slots include a plurality of slots in a first direction and a plurality of slots in a second direction. In one possible implementation, the angle between the first direction and the second direction is in a range from 45 degrees to 90 degrees. For example, the angle between the first direction and the second direction may be 90 degrees. In one possible implementation, the slots in the first direction have a first size and the slots in the second direction have a second size. These sizes may be the same. For example, each slot may have a width in a first range of 10 microns to 20 microns and a depth in a range of 10 microns to 20 microns.

[0048] A plurality of slots in the first direction and a plurality of slots in the second direction form a cross-line pattern covering a portion (e.g., the entire portion) of the metal layer 711. As shown, the cross-line pattern is formed in the bonding region 730 of the metal layer 711, but does not exist in an area outside the bonding region 730. The cross-line pattern may have a first period in the first direction and a second period in the second direction. In one possible implementation, the first period is equal to the second period. For example, the first period in the first direction may be approximately 1000 microns (±50 microns), and the second period in the second direction may be approximately 1000 microns (±50 microns).

[0049] Figure 8 The specific implementation according to the present disclosure is shown Figure 7 800 of a portion of the bonding area 730 is shown, and includes an inset 801 showing a side view of a representative slot. As shown in the top view 800, the cavities are formed to have a repeating pattern having a first period 810 in a first direction and a second period 820 in a second direction. As shown, the second period 820 can be greater than the first period 810. In one possible implementation, forming the plurality of locking features includes stamping a metal layer to form the slots. In another possible implementation, forming the plurality of locking features includes laser etching a metal layer to form the slots.

[0050] As shown in inset 801, each of the plurality of slots may have a depth 830 in the range of 10 microns to 20 microns and a width 870 in the range of 10 microns to 20 microns. The process of forming the slots may produce an edge 840 that is raised above the surface of the metal layer by a height 850. This height 850 may be made less than 10 microns to prevent cracking of the die when the die is pressed against the surface 860 of the metal layer during a thermal bonding or sintering process.

[0051] Fig. 99 is a flow chart of a method for attaching a die to a substrate (i.e., a die attach process 900) according to a possible implementation of the present disclosure. The die attach process 900 may include a method for contact bonding a die to a substrate (i.e., a thermal contact bonding process 901), which may be part of a method for sintering a die to a substrate.

[0052] The die attach process 900 includes forming 910 a plurality of locking features (e.g., cavities, slots) in a metal layer (e.g., a silver-plated copper layer) of a substrate (e.g., a DBC substrate). The forming 910 (i.e., manufacturing) of the plurality of locking features may be performed using a variety of techniques. Possible techniques for forming the locking features may include, but are not limited to, chemical etching, machining (e.g., stamping, embossing, milling), laser etching, coating, molding, and plasma etching. Any combination of these techniques may also be used to form the locking features in the metal layer.

[0053] The die attach process 900 may also include laminating 920 a die transfer film (e.g., an Ag nanoparticle film) to a die (e.g., a SiC die). The die attach process 900 may also include placing 930 the laminated die on a metal layer to form a stacked structure including the die transfer film directly between the metal layer and the die. The die attach process 900 may also include adhering 940 the stacked structure (e.g., applying heat and pressure to the stacked structure for a thermal touch bonding period) to form a touch bonded stacked structure. The die attach process 900 may also include moving (i.e., transporting 950) the touch bonded stacked structure (e.g., transporting between stations in a facility) and sintering 960 the touch bonded stacked structure so that the die is attached to the substrate.

[0054] Although certain features of the described implementations have been described as described herein, those skilled in the art will now appreciate that many modifications, alternatives, variations, and equivalents are contemplated. Therefore, it should be understood that the appended claims are intended to cover all such modifications and variations that fall within the scope of the implementations. It should be understood that these modifications and variations are presented only by way of example and not limitation, and that various changes in form and detail may be made. In addition to mutually exclusive combinations, any portion of the apparatus and / or method described herein may be combined in any combination. The implementations described herein may include various combinations and / or sub-combinations of the functions, components, and / or features of the different implementations described.

[0055] It will be understood that in the foregoing description, when an element is referred to as being on another element, connected to another element, electrically connected to another element, coupled to another element, or electrically coupled to another element, the element may be directly on another element, connected or coupled to another element, or one or more intermediate elements may be present. On the contrary, when an element is referred to as being directly on another element, directly connected to another element, or directly coupled to another element, there is no intermediate element. Although the term directly on, directly connected to, or directly coupled to may not be used throughout the specific embodiments, the element shown as being directly on an element, directly connected, or directly coupled can be mentioned in this manner. The claims of the present application, if present, may be revised to narrate the example relationships described in the specification or shown in the accompanying drawings.

[0056] As used in this specification, singular forms may include plural forms unless the context clearly indicates a particular case. Spatially relative terms (e.g., above, above, above, below, below, below, below, etc.) are intended to encompass different orientations of the device in use or operation, in addition to the orientations shown in the drawings. In some implementations, the relative terms above and below may include vertically above and vertically below, respectively. In some implementations, the term adjacent can include lateral adjacent or horizontal adjacent.

[0057] Some implementations may be implemented using various semiconductor processing and / or packaging technologies. Some implementations may be implemented using various types of semiconductor processing technologies associated with semiconductor substrates, including but not limited to, for example, silicon (Si), gallium arsenide (GaAs), gallium nitride (GaN), silicon carbide (SiC), etc.

Claims

1. A method for sintering a die to a substrate, the method comprising: forming a plurality of locking features in a metal layer of the substrate; laminating a die transfer film to the die; placing the die and the die transfer film on the substrate to form a stacked structure, the stacked structure including the die transfer film directly between the metal layer and the die; adhering the laminate structure to form a touch-bonded laminate structure; as well as The touch-bonded stack is sintered such that the die is bonded to the substrate.

2. The method according to claim 1, further comprising: The touch-bonded stack is transported prior to sintering, wherein the plurality of locking features provide a bond strength of the touch-bonded stack that is stronger than the plurality of locking features, and the bond strength is stronger than a force caused by the transport.

3. The method according to claim 1, wherein: The substrate is a direct bond copper substrate or an active matrix brazed substrate, the substrate comprising a ceramic layer between a first copper layer and a second copper layer; and The metal layer is the first copper layer.

4. The method of claim 1 , wherein forming the plurality of locking features in the metal layer comprises: The metal layer is embossed or laser etched to form the plurality of locking features. 5 . The method of claim 1 , wherein the plurality of locking features comprises a plurality of cavities arranged in a repeating pattern on the metal layer of the substrate.

6. The method of claim 1, wherein the plurality of locking features comprises a plurality of slots in a first direction and a second direction, the first direction being angled to the second direction such that the plurality of slots form a crosshatch pattern on the metal layer of the substrate.

7. A power module, comprising: a substrate comprising a plurality of locking features in a metal layer of the substrate; and A die including circuitry for the power module, the die being attached to the substrate using a die attach process, the die attach process comprising: laminating a die transfer film to the die; placing the die and the die transfer film on the substrate to form a stacked structure, the stacked structure including the die transfer film directly between the metal layer and the die; adhering the laminate to form a touch-bonded laminate; and The touch-bonded stack is sintered such that the die is bonded to the substrate.

8. The power module of claim 7, wherein the die is silicon carbide, the substrate is a direct bond copper substrate, the metal layer is silver plated copper, and the die transfer film comprises silver nanoparticles in an adhesive matrix.

9. The power module according to claim 7, wherein the plurality of locking features are a plurality of cavities in the metal layer, the plurality of cavities are arranged in a repeating pattern on the metal layer of the substrate, or the plurality of locking features are narrow grooves in the metal layer, the narrow grooves are arranged in a first direction and a second direction, the first direction is angled with the second direction so that the narrow grooves form a cross-line pattern on the metal layer of the substrate.

10. A method for contact bonding a die to a substrate, the method comprising: forming a plurality of locking features in a metal layer of the substrate; laminating a die transfer film to the die; placing the die and the die transfer film on the substrate to form a stacked structure, the stacked structure including the die transfer film directly between the metal layer and the die; applying a force to the die so that the stack is pressed together for a thermal bonding period; as well as The substrate is heated so that the temperature of the stack structure increases during the thermal bonding period, and the die is bonded to the substrate to form a bonded stack structure at the end of the thermal bonding period.

11. The method for contact bonding the die to a substrate according to claim 10, further comprising: The touch-bonded stack is transported, wherein the plurality of locking features result in a bonding strength of the touch-bonded stack sufficient to keep the stack intact while the die touch-bonded to the substrate is transported.

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