Graphite heat spreader structure and method of making same

Abstract

To provide a heat spreader structure having high heat dissipation performance capable of solving heat generation of an electronic component such as a semiconductor chip.SOLUTION: The heat spreader structure according to the present invention is a lateral heat spreader structure 1, characterized in that a sacrificial layer made of SOG (spin-on-glass, SiO2) is laminated on the surface of a heat spreader sheet body made of a high thermal conductivity graphite sheet, and the surface of the sacrificial layer is flattened.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a heat spreader structure that solves urgent thermal problems in semiconductor packaging such as three-dimensional semiconductor chips. [Background technology]

[0002] In recent years, with the miniaturization and high performance of electronic devices, heat generation from electronic components such as semiconductor chips has become an urgent issue, and there is a demand for heat dissipation materials and structures that can efficiently dissipate heat. For example, graphite sheets, which have a high heat dissipation capacity of over 1000 W / mK in the planar direction, are widely used as heat diffusion sheets.

[0003] Patent Document 1 describes an invention that uses a graphite sheet for heat dissipation in electronic devices. The graphite sheet is formed by covalent bonding of carbon atoms, and has a specific gravity of 1.57 g / cm. 3 or more, and the thermal diffusivity is 8cm 2 It has been described that the use of a heat dissipation graphite sheet with a thermal conductivity of 1 / s or more improves the heat dissipation properties of electronic devices and the like (see Patent Document 1: International Publication No. 2020 / 138202).

[0004] Patent Document 2 describes an invention relating to a graphite thin film / silicon substrate laminate, its manufacturing method, and a substrate for a high heat dissipation type electronic device, and describes a laminated heat dissipation structure in which a Si chip and a graphite layer are directly bonded (see Patent Document 2: International Publication No. 2006 / 134858). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2020 / 138202 [Patent Document 2] International Publication No. 2006 / 134858 Summary of the Invention [Problem to be solved by the invention]

[0006] As in Patent Document 2, in order to bond a conventional graphite sheet to a Si chip, the surface of the graphite sheet must be flat. For example, the graphite surface is flattened using CMP (chemical mechanical polishing), but it is very difficult to achieve an average roughness Ra of 1 nm or less, which is necessary for bonding to a Si chip. [Means for solving the problem]

[0007] The present invention has been made in view of the above circumstances, and has an object to provide a heat spreader structure having high heat dissipation performance that can solve the problem of heat generation from electronic components such as semiconductor chips.

[0008] The present invention solves the above problems by the means described below.

[0009] The heat spreader structure according to the present invention is a lateral heat spreader structure, The heat spreader sheet is made of a highly thermally conductive graphite sheet, and a sacrificial layer made of SOG (spin-on-glass, SiO2) is laminated on the surface of the sheet, with the surface of the sacrificial layer being flattened.

[0010] The heat spreader structure is preferably a three-dimensional combination of the lateral heat spreader structure and a vertical heat spreader structure formed on the side surface of the chip or the side surface of the package.

[0011] In the heat spreader structure, the sacrificial layer is preferably made of PI (polyimide) or PI (polyimide) containing a heat dissipating filler.

[0012] In the heat spreader structure, the heat dissipating filler powder is preferably alumina, aluminum nitride, zinc oxide, boron nitride or diamond.

[0013] In the heat spreader structure, the sacrificial layer is preferably made of Cu (copper).

[0014] In the heat spreader structure, the heat spreader sheet body is preferably made of multi-layer graphene or DLC (diamond-like carbon) formed on a Si substrate.

[0015] The method for producing the heat spreader structure is characterized in that the sacrificial layer of the heat spreader structure is planarized to an average roughness Ra of 1 nm or less using CMP (chemical mechanical polishing).

[0016] Furthermore, the method for manufacturing the heat spreader structure is characterized in that the sacrificial layer of the heat spreader structure is planarized to an average roughness Ra of 1 nm or less using CMP (chemical mechanical polishing), and the Si substrate is also planarized from the back side using CMP (chemical mechanical polishing) to an average roughness Ra of 1 nm or less. [Effects of the Invention]

[0017] According to the present invention, it is possible to realize a heat spreader structure having high heat dissipation performance that can solve the problem of heat generation from electronic components such as semiconductor chips. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a cross-sectional view illustrating an example of a lateral heat spreader structure according to an embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view showing an example in which the lateral heat spreader structure according to the present invention is applied to a three-dimensional semiconductor chip. [Figure 3] FIG. 3 is a cross-sectional view showing an example in which the lateral heat spreader structure according to the present invention is applied to a package-on-package (PoP) mounting structure. [Figure 4] FIG. 4 is a cross-sectional view showing an example of a three-dimensional heat spreader structure according to the present invention. [Figure 5]FIG. 5 is a cross-sectional view illustrating an example of a lateral heat spreader structure fabricated using film deposition on a Si substrate according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. As shown in FIG. 1, the lateral heat spreader structure 1 in this embodiment has a structure in which a sacrificial layer made of SOG (spin-on-glass, SiO2) is laminated on the surface of a heat spreader sheet body made of a highly thermally conductive graphite sheet as shown in (a), as shown in (b), and the surface of the sacrificial layer is planarized as shown in (c). If it is necessary to maintain insulation between the sacrificial layer and the Si substrate, as shown in (d), the sacrificial layer surface is planarized by CMP so that the graphite, graphene, or DLC film is not exposed on the sacrificial layer surface. If it is not necessary to maintain insulation between the sacrificial layer and the Si substrate, as shown in (e), the graphite, graphene, or DLC film is exposed on the sacrificial layer surface and made flush with the sacrificial layer surface. This process is performed on both sides of the graphite sheet.

[0020] This flattens the surface, making it easier to bond the highly thermally conductive graphite sheet to the Si chip 3 as a lateral heat spreader.

[0021] Figure 2 shows an example in which the lateral heat spreader structure 1 is applied to a three-dimensional semiconductor chip. In this application example, it is possible to improve the heat dissipation performance of electronic devices equipped with a highly heat-generating Si chip 3. Figure 3 shows an example in which the lateral heat spreader structure 1 is applied to a PoP (package-on-package) mounting structure. In this application example, it is possible to improve the heat dissipation performance of electronic devices equipped with a stacked package structure that mounts a highly heat-generating Si chip 3. Note that TIM in the figure stands for Thermal Interface Material.

[0022] Also, a configuration in which the lateral heat spreader structure 1 and the vertical heat spreader structure 4 formed on the side surface of the chip 3 or the package are combined three-dimensionally is preferred. As shown in Figure 4, the lateral heat spreader structure 1 in this embodiment is joined to the vertical heat spreader structure 4 formed on the side surface of the chip 3 or the package.

[0023] This allows the heat diffused laterally through the horizontal heat spreader to be efficiently transferred to the heat sink 2 through the vertical heat spreader.

[0024] Therefore, in this application example, it is possible to further improve the heat dissipation performance of an electronic device or the like that incorporates a stacked package structure in which a highly heat-generating Si chip 3 is mounted.

[0025] In addition, in the heat spreader structure, the sacrificial layer is preferably made of PI (polyimide) or PI (polyimide) containing a heat dissipating filler.

[0026] As a result, by using PI (polyimide) or PI (polyimide) containing heat-dissipating filler, the temperature conditions during the film formation process can be lowered compared to using SOG (spin-on-glass, SiO2), which means that damage caused by oxidation of the graphite sheet surface can be prevented.In addition, the inclusion of heat-dissipating filler improves the thermal conductivity of the sacrificial layer.

[0027] Therefore, the heat generated by the Si chip 3 can be efficiently transferred to the graphite sheet of the lateral heat spreader, improving the heat dissipation performance.

[0028] The heat-dissipating filler is preferably a powder of alumina, aluminum nitride, zinc oxide, boron nitride or diamond.

[0029] As a result, by using the insulating heat-dissipating filler powder, the thermal conductivity of the sacrificial layer is improved while the insulating properties of the sacrificial layer are maintained.

[0030] Therefore, while maintaining the insulation between the Si chip 3 and the heat spreader, the heat generated by the Si chip 3 can be more efficiently transferred to the graphite sheet of the lateral heat spreader, further improving the heat dissipation performance.

[0031] In addition, the heat spreader structure preferably has a sacrificial layer made of Cu (copper).

[0032] This provides electrical conductivity to the sacrificial layer, but also has the effect of further improving thermal conductivity.

[0033] Therefore, in applications where insulation between the Si chip 3 and the heat spreader is not required, the heat generated by the Si chip 3 can be more efficiently transferred to the graphite sheet of the lateral heat spreader, further improving heat dissipation.

[0034] Furthermore, the heat spreader structure preferably has a heat spreader sheet body made of multilayer graphene or DLC (diamond-like carbon) deposited on a Si substrate. As shown in FIG. 5, the lateral heat spreader fabricated using deposition on a Si substrate in this embodiment involves depositing a DLC (diamond-like carbon) film on the Si substrate, followed by deposition of a sacrificial layer of SOG (spin-on-glass, SiO), PI (polyimide), or Cu (copper). Next, planarization is performed using CMP. If insulation with the Si substrate is required, planarization CMP is used to create a sacrificial layer surface where the graphite, graphene, or DLC film is not exposed, as shown in (d). If insulation with the Si substrate is not required, planarization CMP is used to create a sacrificial layer surface where the graphite, graphene, or DLC film is exposed and flush with the sacrificial layer, as shown in (e). The Si substrate is then removed from the backside, resulting in a structure with both surfaces planarized.

[0035] This structure allows the Si substrate to be removed from the rear surface by chemical etching or by a general CMP process.

[0036] Therefore, in this case, a structure in which both surfaces are flattened can be obtained more easily.

[0037] The method for producing the heat spreader structure is characterized in that the sacrificial layer of the heat spreader structure is planarized to an average roughness Ra of 1 nm or less using CMP (chemical mechanical polishing).

[0038] By setting the average roughness Ra to 1 nm or less, the contact area between the heat spreader surface and the Si chip 3 surface increases, resulting in a bond with high-efficiency heat transfer at the bonded interface. Also, this allows the use of a bonding method that utilizes precision bonding technology such as molecular bonding technology.

[0039] Therefore, the lateral heat spreader and the Si chip 3 are joined with high precision, and heat dissipation can be improved.

[0040] In addition, the method for manufacturing the heat spreader structure is characterized in that the sacrificial layer of the heat spreader structure is planarized to an average roughness Ra of 1 nm or less using CMP (chemical mechanical polishing), and further the Si substrate is planarized from the back side using CMP (chemical mechanical polishing) to an average roughness Ra of 1 nm or less.

[0041] This also applies to the CMP of the Si substrate from the backside, where the average roughness Ra is set to 1 nm or less, increasing the contact area between the heat spreader surface and the Si chip 3 surface, resulting in a bond with highly efficient heat transfer at the bonded interface. It also enables the use of a bonding method that utilizes precision bonding technology such as molecular bonding technology.

[0042] Therefore, in the CMP of the Si substrate from the rear surface, the lateral heat spreader and the Si chip 3 are joined with high precision, and heat dissipation can be improved.

[0043] As a result, it is possible to realize a heat spreader structure with high heat dissipation performance that can solve the problem of heat generation from electronic components such as semiconductor chips. [Explanation of symbols]

[0044] 1 Lateral heat spreader structure 2 heat sinks 3 Si chip 4 Vertical heat spreader structure

Claims

1. It has a lateral heat spreader structure, The surface of the heat spreader sheet body, which is made of a highly thermally conductive graphite sheet, is coated with SOG (spin-on glass, SiO ２ ) is laminated on a sacrificial layer, and the surface of the sacrificial layer has a flattened structure. A heat spreader structure characterized by:

2. the lateral heat spreader structure; A vertical heat spreader structure formed on the side of the chip or package is combined three-dimensionally. The heat spreader structure according to claim 1 ,

3. The sacrificial layer is made of PI (polyimide) or PI (polyimide) containing a heat-dissipating filler.

3. The heat spreader structure according to claim 1 or 2, wherein:

4. The heat-dissipating filler is a powder of alumina, aluminum nitride, zinc oxide, boron nitride or diamond.

3. The heat spreader structure according to claim 1 or 2, wherein:

5. The sacrificial layer is made of Cu (copper).

3. The heat spreader structure according to claim 1 or 2, wherein:

6. The heat spreader sheet body is made of multilayer graphene or DLC (diamond-like carbon) formed on a Si substrate.

3. The heat spreader structure according to claim 1 or 2, wherein:

7. The sacrificial layer of the heat spreader structure is planarized to an average roughness Ra of 1 nm or less using CMP (chemical mechanical polishing). A method for manufacturing a heat spreader structure, comprising:

8. The sacrificial layer of the heat spreader structure is planarized to an average roughness Ra of 1 nm or less using CMP (chemical mechanical polishing), and the Si substrate is planarized from the back side to an average roughness Ra of 1 nm or less using CMP (chemical mechanical polishing). A method for manufacturing a heat spreader structure, comprising:

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