3D high-heat-dissipation packaging method and packaging structure

Abstract

The invention discloses a 3D high-heat-dissipation packaging method and packaging structure, and the method comprises the steps: providing a 3D packaging structure which is formed by oppositely stacking and plastic packaging a plurality of chips, and forming a heat-conducting metal layer on the back surface of the top layer of the 3D packaging structure; forming a carbon nanotube layer on the surface of the metal layer; and applying pressure within a preset pressure range between the front surface of the bottom layer of the 3D packaging structure and the carbon nanotube layer, and comprehensively scanning the carbon nanotube layer by using high-power pulse laser, so that the carbon nanotube layer and the heat-conducting metal layer are diffused at an interface under laser shock to form a metal-carbon nanotube composite layer. Compared with the prior art, the compactness and the heat conductivity of the heat conduction metal layer can be improved, the heat dissipation effect of the device is improved, and the stress warping of the device can be effectively reduced.

Description

Technical Field

[0001] The present invention relates to the field of semiconductors, and in particular to a 3D high heat dissipation packaging method and packaging structure. Background Art

[0002] Existing 3D packaging mainly involves flip-chip soldering the chip onto an adapter board, and the chip and adapter board, as well as the stacking between chips, are electrically interconnected through the TSV process. As the process nodes of chips continue to shrink, the number of layers in the 3D stack is also increasing, and the requirements for heat dissipation are becoming increasingly higher. At present, in order to improve the heat dissipation effect of 3D multi-layer stacked devices, some heat-conducting media are added to enhance the heat dissipation, such as the heat sink structure mentioned in patent CN 115621225A: the entire chip is provided with two inner and outer heat dissipation layers, and the outer heat dissipation layer is connected to the packaging substrate to enhance the overall thermal conductivity. However, this process of adding an external heat dissipation medium is relatively complicated, which increases the difficulty of packaging the entire device, increases the size of the entire device, and has a higher overall cost. Therefore, it is necessary to design a new heat dissipation structure to meet the performance requirements of 3D packaging. Summary of the Invention

[0003] The purpose of the present invention is to provide a 3D high heat dissipation packaging method and packaging structure, which can not only improve the density and thermal conductivity of the thermally conductive metal layer and the heat dissipation effect of the device, but also effectively reduce the stress warping of the device.

[0004] In order to achieve the above-mentioned objectives, the present invention provides a 3D high-heat dissipation packaging method, comprising: providing a 3D packaging structure formed by relatively stacking and plastic-sealing a plurality of chips, forming a thermally conductive metal layer on the back side of the top layer of the 3D packaging structure; forming a carbon nanotube layer on the surface of the metal layer; applying a pressure within a preset pressure range between the front side of the bottom layer of the 3D packaging structure and the carbon nanotube layer, and using a high-power pulsed laser to fully scan the carbon nanotube layer, so that under the impact of the laser, the carbon nanotube layer and the thermally conductive metal layer diffuse at the interface to form a metal-carbon nanotube composite layer.

[0005] Preferably, forming a thermally conductive metal layer on the backside of the top layer of the 3D package structure specifically includes: performing a laser microporation treatment on the backside of the top layer to form a plurality of microporous structures; electroplating the backside of the top layer with the microporous structures to form an electroplated metal layer; and polishing the electroplated metal layer to obtain a thermally conductive metal layer with a smooth surface. The present invention performs a laser microporation treatment on the backside of the top layer of the 3D package structure before forming the thermally conductive metal layer, effectively increasing the contact area between the thermally conductive metal layer and the top chip of the 3D package structure, thereby enhancing the heat dissipation effect.

[0006] Specifically, a plated metal layer with a thickness of 10-15 μm is electroplated on the back side of the top layer forming the microporous structure, and then CMP is used to smooth the surface protrusions of the plated metal layer to obtain a thermal conductive metal layer with a thickness of 5-10 μm.

[0007] Specifically, when the back side of the top layer is subjected to laser microporation treatment to form a plurality of microporous structures: the spot diameter of the laser beam used is 20 to 30 μm, the laser power used is 3 to 5 W, the laser pulse width is 5 to 20 μs, the scanning speed is 3000 to 5000 mm / s, and in the microporous structure, the micropore spacing is 30 to 40 μm, and the micropore depth is 5 to 10 μm.

[0008] Preferably, the thickness of the heat-conducting metal layer is 5-10 μm, and the thickness of the carbon nanotube layer is 0.5-1 μm.

[0009] Preferably, forming a carbon nanotube layer on the surface of the metal layer specifically includes: irradiating the surface of the thermally conductive metal layer with UV light for a first predetermined time, and then coating the thermally conductive metal layer with a CVD process to form the carbon nanotube layer. Irradiating the thermally conductive metal layer with UV light for the first predetermined time effectively activates the surface of the thermally conductive metal layer, increasing the surface energy of the thermally conductive metal layer, facilitating the formation of the carbon nanotube layer, and achieving a tighter connection between the carbon nanotube layer and the thermally conductive metal layer.

[0010] Preferably, the preset pressure range is 5-10 N. Of course, the preset pressure range can also be other values.

[0011] Preferably, when a high-power pulse laser is used to fully scan the carbon nanotube layer, the laser power used is 5-10W, the laser pulse width used is 5-20μs, the laser spot diameter used is 20-30μm, and the laser scanning speed used is 3000-5000mm / s.

[0012] Preferably, when a high-power pulsed solid-state laser is used to fully scan the carbon nanotube layer, the scanning path of the laser used is to follow a circular path from the edge of the wafer to the center until the scanning area of the laser covers the entire back side of the top layer. This not only improves the surface treatment efficiency, but also effectively prevents the 3D packaging structure from warping under stress changes.

[0013] Preferably, applying pressure within a preset pressure range between the bottom front surface of the 3D packaging structure and the carbon nanotube layer specifically includes: placing the top back surface of the 3D packaging structure facing upward on a vacuum suction cup, fully covering the back surface of the top surface with a transparent chip, using a pressure ring on the transparent chip to press the transparent chip and the position of the back surface of the top surface near the edge, and controlling the pressure within a preset pressure range. Pressing the 3D packaging structure from the periphery can reduce warping.

[0014] Preferably, providing a 3D packaging structure formed by relatively stacking and plastic-sealing a plurality of chips specifically includes: providing a plurality of active chips, processing silicon vias on the active chips and electroplating the silicon vias to form a conductive metal layer, and thinning the back side of the active chip to expose the conductive metal layer; stacking the plurality of active chips relatively insulated together to form a 3D stacking structure, and electrically connecting the plurality of active chips through the conductive metal layer; stacking the 3D stacking structure and a top chip relatively together and plastic-sealing to form a 3D packaging structure, wherein the top back side of the 3D packaging structure is the side of the top chip away from the 3D stacking structure.

[0015] The present invention also provides a 3D high heat dissipation packaging structure, which is manufactured by the above-mentioned 3D high heat dissipation packaging method.

[0016] Compared with existing technologies, the present invention, on the one hand, coats a thin, highly thermally conductive carbon nanotube layer (CNT material, Carbon Nanotubes) on the heat-dissipating metal layer. Applying a certain pressure and then heating the surface with laser light not only improves the compactness and thermal conductivity of the heat-dissipating structure (composed of the thermally conductive metal layer and the CNT layer), but also forms a metal-based / CNT composite material under the action of thermal diffusion, significantly increasing the thermal conductivity of the heat-dissipating structure and improving the heat dissipation effect of the entire device. Furthermore, the present invention uses laser heat treatment on the surface of the heat-dissipating structure, rather than heating the entire device, to reduce thermal stress warping of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figures 1 to 7 It is a flow chart of the 3D high heat dissipation packaging method of the present invention.

[0018] Figure 8 This is another flow chart of the 3D high heat dissipation packaging method of the present invention. DETAILED DESCRIPTION

[0019] In order to explain the technical content, structural features, achieved objectives and effects of the present invention in detail, the following is a detailed description in conjunction with the embodiments and the accompanying drawings.

[0020] refer to Figure 8 The present invention provides a 3D high heat dissipation packaging method, including steps S1 to S4.

[0021] S1, reference Figure 1 , providing a 3D packaging structure 100 formed by stacking and plastic-sealing a plurality of chips.

[0022] In this embodiment, providing a 3D package structure formed by stacking a plurality of chips relative to each other specifically includes: providing a plurality of active chips 103, processing through-silicon vias 101 on the active chips 103, electroplating the through-silicon vias 101 to form a conductive metal layer 102, and thinning the back surfaces of the active chips 103 to expose the conductive metal layer 102; stacking the plurality of active chips 103 relative to each other in an insulated manner to form a 3D stacked structure, and electrically connecting the plurality of active chips 103 through the conductive metal layer 102; stacking the 3D stacked structure relative to a top chip 104 and performing plastic encapsulation to form a 3D package structure 100, and sealing the 3D package structure 100 with a plastic encapsulant 105. After sealing, thinning is further performed to expose the surface of the top chip 104 to form the back surface of the top layer, and the formed 3D package structure 100 is cleaned.

[0023] The backside of the top layer of the 3D package structure 100 is the side of the top chip 104 facing away from the 3D stacked structure. The bottommost active chip 103 is flip-chip connected to a circuit substrate or redistribution layer. The bottommost active chip 103 also has solder balls 11 formed on the bottom that are electrically connected to the circuit substrate.

[0024] S2, Ref. Figures 2 to 4 , a thermally conductive metal layer 20 is formed on the back side of the top layer of the 3D packaging structure 100 .

[0025] Step S2 includes steps S21 to S23.

[0026] refer to Figure 2 , S21, performing laser microporation treatment on the back side of the top layer to form a plurality of microporous structures 201. Figure 3 , forming an electroplated metal layer 20a by electroplating on the back side of the top layer forming the microporous structure 201. Figure 4 The electroplated metal layer 20a is ground flat to obtain a thermally conductive metal layer 20 with a smooth surface. CMP (Chemical Mechanical Polishing) is used to smooth out any surface protrusions on the electroplated metal layer 20a to achieve a certain degree of flatness, thereby forming the thermally conductive metal layer 20. Specifically, a 10-15 μm thick electroplated metal layer 20a is applied to the back surface of the top layer forming the microporous structure 201. CMP is then used to smooth out any surface protrusions on the electroplated metal layer 20a, resulting in a 5-10 μm thick thermally conductive metal layer 20.

[0027] Specifically, a thermally conductive metal layer 20 is deposited on the back side of the top layer forming the microporous structure 201 using an electron beam evaporation coating or magnetron sputtering coating process. The thermal conductivity of the thermally conductive metal layer must be greater than 300 W / mK. For example, the thermal conductivity of a metal such as Cu can reach 400 W / mK. The lower surface of the thermally conductive metal layer 20 is filled in the microporous structure 201, but the thickness of the thermally conductive metal layer 20 does not include the depth of the thermally conductive metal layer 20 within the microporous structure 201. In this embodiment, the thermally conductive metal layer 20 is a copper-plated layer. Of course, the material of the thermally conductive metal layer 20 is not limited to copper and can also be other materials with a thermal conductivity greater than 300 W / mK, such as silver, gold, etc.

[0028] The back of the top layer is laser-micropored using an ultraviolet laser to form a plurality of microporous structures 201. When the back of the top layer is laser-micropored using an ultraviolet laser to form a plurality of microporous structures 201, the laser beam spot diameter used is 20-30 μm, the laser power used is 3-5 W, the laser pulse width is 5-20 μs, the scanning speed is 3000-5000 mm / s, and the microporous structure 201 has a micropore spacing of 30-40 μm and a micropore depth of 5-10 μm. After the microporation treatment, the back of the top layer is also rinsed with DI water (deionized water) to remove residual foreign matter left after the laser drilling.

[0029] S3, reference Figure 5 A carbon nanotube layer 30 is formed on the surface of the thermally conductive metal layer 20 .

[0030] In step S3 , after UV light is irradiated on the surface of the heat-conducting metal layer 20 for a first preset time, a carbon nanotube layer 30 is formed on the heat-conducting metal layer 20 using a CVD process.

[0031] The thickness of the thermally conductive metal layer 20 is 5-10 μm, and the thickness of the carbon nanotube layer 30 is 0.5-1 μm. The first preset time is 5 minutes. Of course, the first preset time is not limited to 5 minutes and can be selected according to the thickness of the carbon nanotube layer 30 and the power of the UV light.

[0032] S4, reference Figure 6 and Figure 7 , the carbon nanotube layer 30 and the thermal conductive metal layer 20 are modified to improve the density and thermal conductivity of the heat dissipation structure.

[0033] Specifically, a pressure within a preset pressure range is applied between the front surface of the bottom layer of the 3D packaging structure 100 and the carbon nanotube layer 30, and a high-power pulsed solid-state laser is used to fully scan the carbon nanotube layer 30. Under the laser shock, through the laser shock hardening and the heat treatment diffusion mechanism of the back heat dissipation layer (composed of the carbon nanotube layer 30 and the heat-conducting metal layer 20), the laser heat-treats the carbon nanotube layer 30 to heat it, thereby causing the carbon nanotube layer 30 and the heat-conducting metal layer 20 to diffuse at the interface, forming a metal-carbon nanotube composite layer 50. The preset pressure range is 5-10N. Of course, the preset pressure range can also be other values. In this embodiment, the metal-carbon nanotube composite layer 50 is a Cu / CNT composite material layer.

[0034] In step S4, refer to Figure 6 and Figure 7 The 3D packaging structure 100 is placed with the backside of the top layer facing upward on a vacuum chuck. A transparent wafer 40 is placed to completely cover the backside of the top layer. A pressure ring is then used to compress the transparent wafer 40 against the edge of the top layer's backside. The pressure is controlled within a preset range. Compressing the 3D packaging structure from the periphery can reduce warping. The transparent wafer 40 is a transparent glass sheet, although other transparent structures may also be used. The light transmittance of the transparent lens 40 is preferably above 95%. In this embodiment, the transparent wafer 40 is the same size as the backside of the top layer in the 3D packaging structure 100.

[0035] Specifically, a high-power pulsed solid-state laser is used to scan the entire carbon nanotube layer 30: the laser scan path follows a circular path from the edge of the wafer to the center, until the laser scan area covers the entire back side of the top layer. This not only improves surface treatment efficiency but also effectively prevents warping of the 3D packaging structure under stress. After the modification process is completed, the transparent wafer 40 is removed.

[0036] When a high-power pulsed solid-state laser is used to fully scan the carbon nanotube layer 30, the laser power used is 5-10W, the laser pulse width used is 5-20μs, the laser spot diameter used is 20-30μm, and the laser scanning speed used is 3000-5000mm / s. Of course, the laser light values emitted by the high-power pulsed solid-state laser can be other values and are not limited to the above values.

[0037] The present invention also discloses a 3D high-heat dissipation packaging structure, manufactured using the aforementioned 3D high-heat dissipation packaging method. The 3D high-heat dissipation packaging structure includes a circuit substrate 10, a plurality of active chips 103 electrically connected to the circuit substrate 10, a top chip 104 positioned above the active chips 103, a microporous structure 201 formed on the back side of the top layer of the top chip 104, away from the circuit substrate 10, a carbon nanotube layer 30 formed on the back side of the thermally conductive metal layer 20 on the back side of the top layer, and a metal-carbon nanotube composite layer 50 formed at the interface between the carbon nanotube layer 30 and the thermally conductive metal layer 20. In this embodiment, the thickness of the metal-carbon nanotube composite layer 50 is 10-50 nanometers, preferably approximately 20 nanometers.

[0038] Compared to existing technologies, the present invention, on the one hand, coats a thin, highly thermally conductive carbon nanotube layer 30 (CNT material) on the heat-dissipating metal layer. Applying a certain pressure and then heating the surface with laser light not only improves the compactness and thermal conductivity of the heat-dissipating structure, but also forms a metal-based / CNT composite material through thermal diffusion between the heat-conductive metal layer 20 and the carbon nanotube layer 30, significantly increasing the thermal conductivity of the heat-dissipating structure and improving the heat dissipation efficiency of the entire device. Furthermore, the present invention uses laser heat treatment on the surface of the heat-dissipating structure, rather than heating the entire device, to reduce thermal stress warping.

[0039] The above disclosure is only the preferred embodiment of the present invention, which certainly cannot be used to limit the scope of the present invention. Therefore, equivalent changes made according to the scope of the patent application of the present invention are still within the scope of the present invention.

Claims

1. A 3D high heat dissipation packaging method, characterized by: include: Providing a 3D packaging structure formed by stacking and plastic-sealing a plurality of chips relative to each other, and forming a thermally conductive metal layer on the back of the top layer of the 3D packaging structure; forming a carbon nanotube layer on the surface of the metal layer; A pressure within a preset pressure range is applied between the bottom front surface of the 3D packaging structure and the carbon nanotube layer, and a high-power pulsed laser is used to fully scan the carbon nanotube layer, so that under the impact of the laser, the carbon nanotube layer and the thermally conductive metal layer diffuse at the interface to form a metal-carbon nanotube composite layer.

2. The 3D high heat dissipation packaging method according to claim 1, wherein: Forming a thermally conductive metal layer on the back side of the top layer of the 3D package structure specifically includes: performing a laser microporation process on the back side of the top layer to form a plurality of microporous structures; Electroplating a metal layer on the back side of the top layer forming the microporous structure; The electroplated metal layer is ground flat to obtain a heat-conducting metal layer with a smooth surface.

3. The 3D high heat dissipation packaging method according to claim 2, wherein: A plated metal layer with a thickness of 10-15 μm is electroplated on the back side of the top layer forming the microporous structure, and then CMP is used to smooth the surface protrusions of the plated metal layer to obtain a thermal conductive metal layer with a thickness of 5-10 μm.

4. The 3D high heat dissipation packaging method according to claim 2, wherein: When the back side of the top layer is subjected to laser microporation treatment to form a plurality of microporous structures: the spot diameter of the laser beam used is 20 to 30 μm, the laser power used is 3 to 5 W, the laser pulse width is 5 to 20 μs, the scanning speed is 3000 to 5000 mm / s, and in the microporous structure, the micropore spacing is 30 to 40 μm and the micropore depth is 5 to 10 μm.

5. The 3D high heat dissipation packaging method according to claim 1, wherein: The thickness of the heat-conducting metal layer is 5-10 μm, and the thickness of the carbon nanotube layer is 0.5-1 μm.

6. The 3D high heat dissipation packaging method according to claim 1, wherein: Forming a carbon nanotube layer on the surface of the metal layer specifically includes: After UV light is irradiated on the surface of the heat-conducting metal layer for a first preset time, a carbon nanotube layer is formed on the heat-conducting metal layer by coating with a CVD process.

7. The 3D high heat dissipation packaging method according to claim 1, wherein: The preset pressure range is 5-10N.

8. The 3D high heat dissipation packaging method according to claim 1, wherein: When a high-power pulse laser is used to fully scan the carbon nanotube layer, the laser power used is 5-10W, the laser pulse width used is 5-20μs, the laser spot diameter used is 20-30μm, and the laser scanning speed used is 3000-5000mm / s.

9. The 3D high heat dissipation packaging method according to claim 1, wherein: When a high-power pulsed laser is used to fully scan the carbon nanotube layer, the scanning path of the laser is a circular path from the edge of the wafer to the center until the scanning area of the laser covers the entire back side of the top layer.

10. The 3D high heat dissipation packaging method according to claim 1, wherein: Applying pressure within a preset pressure range between the bottom front side of the 3D packaging structure and the carbon nanotube layer specifically includes: placing the top back side of the 3D packaging structure facing upward on a vacuum suction cup, fully covering the back side of the top side with a transparent chip, using a pressure ring on the transparent chip to press the position of the transparent chip and the back side of the top side near the edge, and controlling the pressure within a preset pressure range.

11. The 3D high heat dissipation packaging method according to claim 1, wherein: The 3D packaging structure provided by stacking and encapsulating several chips includes: Providing a plurality of active chips, processing through-silicon vias on the active chips and electroplating the through-silicon vias to form a conductive metal layer, and thinning the backside of the active chips to expose the conductive metal layer; stacking a plurality of the active chips in an insulated manner relative to each other to form a 3D stacked structure, and electrically connecting the plurality of the active chips through the conductive metal layer; The 3D stacking structure and a top chip are stacked together opposite to each other and plastic-encapsulated to form a 3D package structure. The top back side of the 3D package structure is the side of the top chip away from the 3D stacking structure.

12. The 3D high heat dissipation packaging method according to claim 1, wherein: The heat-conducting metal layer is a copper-plated layer.

13. A 3D high-heat dissipation packaging structure, characterized by: Made by the 3D high heat dissipation packaging method according to any one of claims 1-12.

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