Thermoplastic polyimide and its use in temporary bonding technology

Abstract

The application discloses a thermoplastic polyimide and application thereof in temporary bonding technology. A preparation method of the thermoplastic polyimide comprises the following steps: obtaining polyamide acid which is a polyimide precursor by copolymerization of a diamine and a dianhydride; and obtaining the thermoplastic polyimide by thermal imidization of the polyamide acid; wherein the temperature of the thermal imidization is 200 DEG C-350 DEG C, and the curing time of the thermal imidization is 0.5h-10h; the diamine is a diamine with flexible bonds and rigid groups; and the dianhydride is a dianhydride with flexible bonds and rigid groups. The thermoplastic polyimide provided by the application meets the process requirements of easy bonding and debonding in the process of ultra-thin wafer processing in the ultraviolet laser temporary bonding technology, improves the efficiency and safety of the temporary bonding process, and has potential application value in electronic packaging.

Description

Technical Field

[0001] This invention relates to the field of polyimide technology, and more particularly to a thermoplastic polyimide and its application in temporary bonding technology. Background Technology

[0002] With the continuous upgrading of consumer electronics products, high-end chips such as 5G communication CPUs / GPUs are also developing towards higher frequency, higher speed, more multifunctionality, higher performance, smaller size, and higher reliability. To meet the requirements of miniaturization, multifunctionality, and intelligence of integrated circuit chips, and to help address the physical limits currently facing the development of Moore's Law, the development of advanced packaging technologies mainly focuses on three-dimensional packaging, such as PIP (Package in Package), POP (Package on Package), MCP (Multi-Chip Package), SIP (System in Package), WLP (Wafer Level Package), and TSV (Through Silicon Via) technology. These technologies reduce package size while improving circuit performance and reducing parasitic effects and time delays. However, regardless of the packaging technology involved, chip thickness reduction is imperative given the trend of maintaining or even reducing the overall package thickness. Especially for the high heat dissipation requirements of 5G communication CPUs / GPUs and power chips, chip thickness will need to be reduced to below 50µm. However, traditional processing techniques are prone to wafer breakage. Therefore, ultrathin wafers must utilize temporary bonding technology to improve chip manufacturing precision and product yield. Among these, the ultraviolet laser temporary bonding solution for photosensitive materials has become the mainstream solution for 8 / 12-inch large-size ultrathin wafer processing due to its lower cost and simpler process. Temporary bonding materials must meet the following requirements: ① Sufficient adhesion to support RDL processes in WLP and high-density fan-out packaging; ② Good thermal stability to meet the requirements of processes such as reflow soldering; ③ Sufficient ultraviolet absorption performance to achieve efficient debonding; ④ Excellent solubility to meet the requirements of wafer surface cleaning after debonding.

[0003] Chinese patent CN104804682A discloses a temporary bonding adhesive for wafer thinning, its preparation method, and bonding and debonding methods. The adhesive uses a base resin with adhesive properties that can depolymerize into low-molecular-weight compounds and / or linear oligomers under strong acid, thereby causing the adhesive layer formed by the bonding adhesive to undergo a significant depolymerization reaction under sufficient acid immersion, thus improving debonding efficiency. Simultaneously, the decomposition temperature of the polymer is above 270℃, improving the thermal stability of the adhesive layer. However, the acidic chemicals in this method have certain environmental destructive potential. Chinese patent CN104204126A discloses an adhesive composition for wafer processing thin films, in which the adhesive layer, composed of acrylic polymers and a photosensitive gas generator, can debond under ultraviolet light. However, the release of photosensitive gas in this method poses a risk of wafer breakage to ultrathin wafers. Summary of the Invention

[0004] In existing technologies, large-size ultrathin wafers are prone to breakage during processing, necessitating temporary bonding techniques to improve chip manufacturing precision and product yield. However, existing temporary bonding materials fall short in meeting the requirements for high heat resistance and excellent ultraviolet absorption. This invention addresses this issue by applying thermoplastic polyimide to ultraviolet laser temporary bonding photosensitive materials based on temporary bonding technology for ultrathin wafer processing. This results in a thermoplastic polyimide with high heat resistance and high ultraviolet laser absorption, achieving the process requirements of easy bonding and debonding during ultrathin wafer processing.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] On one hand, the present invention provides a method for preparing thermoplastic polyimide, comprising the following steps:

[0007] (1) Polyamic acid, a polyimide precursor, is obtained by copolymerizing diamine and dianhydride;

[0008] (2) The polyamic acid obtained in step (1) is subjected to thermal imidization to obtain thermoplastic polyimide;

[0009] The temperature of the thermal imidization is 200℃~350℃, and the curing time of the thermal imidization is 0.5h~10h.

[0010] The diamine is a diamine having both flexible bonds and rigid groups; the dianhydride is a dianhydride having both flexible bonds and rigid groups.

[0011] In a preferred embodiment, the flexible bond is selected from one or more of ether bonds, thioether bonds, and carbonyl groups.

[0012] In a preferred embodiment, the rigid group is selected from one or more of the following: biphenyl group, fluorenyl group, phenyl group, and indane structure.

[0013] Specifically, the diamines having flexible bonds and rigid groups can be exemplified by 9,9-bis(4-aminophenyl)fluorene, 9,9-bis(3-aminophenyl)fluorene, 9,9-bis(3-fluoro-4-aminophenyl)fluorene, 1,1-bis(4-aminophenyl)cyclohexane, 9,9-bis(4-amino-3-chlorophenyl)fluorene, 9,9-bis(4-amino-3-tolyl)fluorene, and 5(6)-amino-1-(4-aminophenyl)fluorene. 5(6)-1-(4-aminophenyl)-1,3,3-trimethylindene, 3,3-bis(4-aminophenyl)phthalide, 1,3-bis(4-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(3-aminophenoxy)benzene, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4-diaminodiphenyl sulfide, 2 2'-Diaminodiphenyl sulfide, 2,2'-bis(4-aminophenoxyphenyl)propane, 4,4'-bis(4-aminophenoxy)biphenyl, 4,4'-bis(3-aminophenoxy)biphenyl, 2,2'-bis[4-(4-aminophenoxyphenyl)]propane, 1,4-phenylene di[[4-(4-aminophenoxy)phenyl] ketone], 4,4'-bis(4-aminophenoxy)benzophenone, 4,4'-bis(3-aminophenoxy)benzophenone, 1,3-bis[4-(3-aminophenoxy)benzoyl]benzene, bis[4-[4-[1-(4-aminophenyl)-1-methylethyl]phenoxy]phenyl] and [1,1':3',1”-terphenyl]-4,4”-diamine, etc.; the above diamines can be used alone or in any mixture.

[0014] Specifically, the dianhydrides having both flexible bonds and rigid groups can be listed as 2,3,3',4'-biphenyltetracarboxylic dianhydride, 2,2,3',3-biphenyltetracarboxylic dianhydride, 2,3,3',4'-diphenyl ether tetracarboxylic dianhydride, 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride, bisphenol A type diether dianhydride, 4,4'-(dimethylmethylene)bis(1,4-phenoxy)bis(isobenzofuran-1,3-dione), 4,5'-[isopropylidene bis[(4,1-phenylene)oxy]]bis(isobenzofuran-1,3-dione), and 5,5'-[9H-fluorene-9-ylidene bis(4,1-phenoxy)] The following dianhydrides can be used individually or in any combination: bis-1,3-isobenzofurandione, 5,5'-[cyclohexylbis(4,1-phenyleneoxy)]bis-1,3-isobenzofurandione, 5,5'-((1,1'-biphenyl)-4,4'-diylbis(oxy))bis-1,3-isobenzofurandione, 4,4'-terephthalic anhydride, 5-[3-(1,3-dioxoisobenzofuran-5-yl)oxyphenoxy]isobenzofuran-1,3-dione, and 1,3-isobenzofurandione.

[0015] In a preferred embodiment, in step (2), the thermal imidization is a multi-stage stepped heating process, with each temperature step spaced 50 to 100°C apart; the heating rate of each stage is 4 to 20°C / min; the holding time of each stage is 60 to 210 min; and the heating stage includes two or more temperature steps.

[0016] In some specific embodiments, the preparation method of the thermoplastic polyimide specifically includes the following steps:

[0017] In a protective atmosphere, diamine is dissolved or mixed in a polar organic solvent, dianhydride is added and stirred to allow it to condense and polymerize to form a polyamic acid solution; then it is heated to 200°C to 350°C in a stepwise heating rate of 4 to 20°C / min to obtain the thermoplastic polyimide.

[0018] In a preferred embodiment, the polar organic solvent is selected from any one or more of N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP), dimethyl sulfoxide (DMSO), tetrahydrofuran (THF), m-cresol, and γ-butyrolactone.

[0019] Preferably, the molar ratio of the diamine to the dianhydride is 0.95 to 1.05.

[0020] In another aspect, the present invention provides thermoplastic polyimide obtained by the above preparation method.

[0021] In the technical solution of this invention, the thermoplastic polyimide has high heat resistance and high ultraviolet laser absorption, and a decomposition temperature T. d >510℃; 355nm ultraviolet light absorption rate >96%.

[0022] In another aspect, the present invention provides the application of the above-mentioned thermoplastic polyimide in temporary bonding technology.

[0023] In another aspect, the present invention provides a method for temporary bonding of the above-mentioned thermoplastic polyimide to ultrathin wafers, comprising the following steps:

[0024] A laminate comprising a first substrate and a second substrate temporarily bonded together by the thermoplastic polyimide and an adhesive material; and a process of heating the adhesive material to cure it.

[0025] In the technical solution of the present invention, the ultrathin wafer refers to a wafer with a thickness of no more than 100 μm.

[0026] In a preferred embodiment, the method of providing the laminate comprising a first substrate and a second substrate temporarily bonded together by the thermoplastic polyimide and an adhesive material is as follows: the thermoplastic polyimide is applied to the first substrate at a rotation speed of 500-3000 rpm; the adhesive material is applied to the second substrate at a rotation speed of 500-3000 rpm; and the thermoplastic polyimide and adhesive material applied to the first and second substrates are bonded together to form a bond pair.

[0027] Preferably, the bonding process to form bonding pairs does not require heating and is carried out at room temperature.

[0028] Preferably, the bonding process for forming bonding pairs is performed under vacuum conditions;

[0029] In some specific embodiments, the bonding to form a bond pair is achieved by bonding the surfaces of the first substrate and the second substrate coated with thermoplastic polyimide or adhesive material together in a bonding machine for 1 to 3 minutes.

[0030] Preferably, the process of heating the adhesive material to cure it involves heating the adhesive material to achieve complete cross-linking and curing to achieve full adhesion, and the heating temperature is 150-200°C; the adhesive material includes, but is not limited to, acrylic resin, epoxy resin, silicone resin, polyurethane, and polyamide;

[0031] In some specific embodiments, the coating of the thermoplastic polyimide and the adhesive material is performed by coating the thermoplastic polyimide and / or the adhesive material dissolved in a polar organic solvent.

[0032] Preferably, the process further includes heating the thermoplastic polyimide coated on the first substrate to cure it; the heating temperature is 150-200°C; in the technical solution of the present invention, during the heating process, the polar organic solvent evaporates, and the thermoplastic polyimide is cured on the first substrate.

[0033] In another aspect, the present invention provides a debonding method employing the above method, comprising the step of degrading the cured thermoplastic polyimide under ultraviolet light irradiation;

[0034] Preferably, the wavelength of the ultraviolet light is 280–400 nm.

[0035] In the technical solution of the present invention, under ultraviolet light irradiation, the cured thermoplastic polyimide degrades and loses its adhesive effect with the first substrate, thereby achieving debonding. The adhesive material does not undergo significant changes during debonding and is generally used in subsequent processing.

[0036] The above technical solution has the following advantages or beneficial effects:

[0037] This invention is based on temporary bonding technology in ultrathin wafer fabrication. It uses diamines and dianhydrides with specific structures to copolymerize polyamic acid, and then controls the temperature and time of thermal imidization of the polyamic acid to prepare a thermoplastic polyimide with high solubility, high heat resistance, and high UV absorption. This polyimide is then applied to UV laser temporary bonding photosensitive materials. By selecting polyimide monomers and multi-component copolymers, the prepared thermoplastic polyimide meets the process requirements of easy bonding and debonding in ultrathin wafer fabrication using UV laser temporary bonding technology, improving the efficiency and safety of the temporary bonding process, and has potential application value in electronic packaging. Attached Figure Description

[0038] Figure 1 This is a temperature rise program diagram of the thermal imidization stepwise temperature rise in step (3) of Examples 1-1 to 8-5 and Comparative Examples 1-1 to 2-1.

[0039] Figure 2 The graph shows the solubility test results of thermoplastic polyimides prepared at different thermal imidization temperatures in Examples 1-1 to 1-5.

[0040] Figure 3 These are thermogravimetric analysis (TGA) curves of thermoplastic polyimides prepared at different thermal imidization temperatures in Examples 1-1 to 1-5.

[0041] Figure 4 These are UV-Vis curve test graphs of thermoplastic polyimides prepared at different thermal imidization temperatures in Examples 1-1 to 1-5.

[0042] Figure 5 The images shown are SAM images of the bonded wafer prepared using the thermoplastic polyimide in Example 1-1 before and after heat treatment in the effect embodiment; where Figure (a) is the image before heat treatment; and Figure (b) is the image after heat treatment.

[0043] Figure 6 The total thickness variation (TTV) graph is shown in the example for the thermoplastic polyimide spin-coated silicon wafer prepared in Example 1-1.

[0044] Figure 7 This is an EDS image of a pure silicon wafer surface.

[0045] Figure 8 The EDS image of the bonded wafer prepared with thermoplastic polyimide in Example 1-1 and the silicon wafer surface after debonding and cleaning is shown in the example for the effect embodiment. Detailed Implementation

[0046] The following embodiments are merely some, not all, of the embodiments of the present invention. Therefore, the detailed descriptions of the embodiments provided below are not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0047] In this invention, unless otherwise specified, all equipment and raw materials are commercially available or commonly used in the industry. The methods described in the following embodiments are conventional methods in the art, unless otherwise specified.

[0048] In the following examples and comparative examples:

[0049] The specific process for preparing thermoplastic polyimide is as follows:

[0050] The dianhydride and diamine were pretreated to remove impurities. Dry nitrogen gas was passed through a flask at room temperature for 3–10 min to ensure the reaction system was under a nitrogen atmosphere. Diamine was added to the flask, followed by the addition of an organic polar solvent. The mixture was stirred until the diamine was completely dissolved, then dianhydride (molar ratio of diamine to dianhydride was 0.95–1.05) was added, and the mixture was continuously stirred for 7–24 h to obtain a polyamic acid (PAA) solution. The PAA solution was evenly spread onto a silicon wafer using spin coating (1500–2000 rpm, 20–40 s). The wafer was then gently baked on a heat exchanger at 40–100 °C for 10–20 min to remove some of the organic solvent. Thermal imidization was performed in a thermostatic drying oven using a stepped heating method. After cooling, thermoplastic polyimide was obtained.

[0051] The dianhydride was divided into two equal portions and added at an interval of 1 to 3 hours.

[0052] Example 1-1

[0053] (1) First, the dianhydride and diamine were pretreated to remove impurities. The diamine was treated in a vacuum oven at 60°C for 6 hours, and the dianhydride was treated in a vacuum oven at 160°C for 6 hours. Then, at room temperature, 1.7422 g of 9,9-bis(4-aminophenyl)fluorene (BAFL) and 1.4617 g of 1,3-bis(4'-aminophenoxy)benzene (TPE-R) were mixed and dissolved in 15 mL of N,N-dimethylacetamide (DMAc) solution in a flask. Then, under a nitrogen atmosphere, 1.5511 g of 2,3,3',4'-diphenyl ether tetracarboxylic dianhydride (a-ODPA) and 1.4711 g of 2,3,3',4'-biphenyl tetracarboxylic dianhydride (a-BPDA) were added sequentially and stirred for 24 hours to obtain a PAA solution.

[0054] (2) Spin-coating the polyamic acid solution evenly onto the silicon wafer at a speed of 1500 rpm for 30 s, and then baking it on a heat spreader at 80 ℃ for 15 min to remove some of the organic solvent DMAc.

[0055] (3) Finally, thermal imidization is carried out in a forced-air drying oven, using a stepped heating method. The heating procedure is as follows: Figure 1 The curve of TPI-200 (heating rate of 5℃ / min, taken out after cooling) Figure 1 In this process, the initial temperature of all heating programs is 0°C; the curve is named TPI-xxx, where TPI represents thermoplastic polyimide, and the number xxx represents the temperature of thermal imidization.

[0056] Examples 1-2

[0057] The difference between the preparation method in this embodiment and that in Example 1-1 is that the thermal imidization temperature in step (3) is 250℃. Figure 1 TPI-250).

[0058] Examples 1-3

[0059] The difference between the preparation method in this embodiment and that in Example 1-1 is that the thermal imidization temperature in step (3) is 280℃. Figure 1 TPI-280).

[0060] Examples 1-4

[0061] The difference between the preparation method in this embodiment and that in Example 1-1 is that the thermal imidization temperature in step (3) is 300℃. Figure 1 TPI-300).

[0062] Examples 1-5

[0063] The difference between the preparation method in this embodiment and that in Example 1-1 is that the thermal imidization temperature in step (3) is 350℃. Figure 1 TPI-350).

[0064] Figure 2 The figure shows the solubility of thermoplastic polyimides prepared at different thermal imidization temperatures in Examples 1-1 to 1-5. As can be seen from the figure, starting from a thermal imidization temperature of 350°C, the solubility significantly increases as the curing temperature decreases. TPI-200 shows a 216-fold increase in solubility compared to TPI-350, and in particular, TPI-200 shows a 482-fold increase in solubility compared to TPI-350 when heated to 80°C.

[0065] Example 2-1

[0066] The difference between the preparation method of this embodiment and that of Example 1-1 is that the diamine in step (1) is replaced with a mixed diamine of 9,9-bis(4-aminophenyl)fluorene and 1,3-bis(3-aminophenoxy)benzene, with a mixing molar ratio of 5:5 and masses of 1.7422 g and 1.4617 g, respectively.

[0067] Example 2-2

[0068] The difference between the preparation method in this embodiment and that in Example 2-1 is that the thermal imidization temperature in step (3) is 250℃. Figure 1 TPI-250).

[0069] Example 2-3

[0070] The difference between the preparation method in this embodiment and that in Example 2-1 is that the thermal imidization temperature in step (3) is 280℃. Figure 1 TPI-280).

[0071] Examples 2-4

[0072] The difference between the preparation method in this embodiment and that in Example 2-1 is that the thermal imidization temperature in step (3) is 300℃. Figure 1 TPI-300).

[0073] Examples 2-5

[0074] The difference between the preparation method in this embodiment and that in Example 2-1 is that the thermal imidization temperature in step (3) is 350℃. Figure 1 TPI-350).

[0075] Example 3-1

[0076] The difference between the preparation method of this embodiment and that of Example 1-1 is that the diamine in step (1) is replaced with a mixed diamine of 9,9-bis(4-aminophenyl)fluorene and 4,4-diaminodiphenyl ether, with a mixing molar ratio of 5:5 and masses of 1.7422 g and 1.0012 g, respectively.

[0077] Example 3-2

[0078] The difference between the preparation method in this embodiment and that in Example 3-1 is that the thermal imidization temperature in step (3) is 250℃. Figure 1 TPI-250).

[0079] Example 3-3

[0080] The difference between the preparation method in this embodiment and that in Example 3-1 is that the thermal imidization temperature in step (3) is 280℃. Figure 1 TPI-280).

[0081] Examples 3-4

[0082] The difference between the preparation method in this embodiment and that in Example 3-1 is that the thermal imidization temperature in step (3) is 300℃. Figure 1 TPI-300).

[0083] Examples 3-5

[0084] The difference between the preparation method in this embodiment and that in Example 3-1 is that the thermal imidization temperature in step (3) is 350℃. Figure 1 TPI-350).

[0085] Example 4-1

[0086] The difference between the preparation method of this embodiment and that of Example 1-1 is that the diamine in step (1) is replaced with a mixed diamine of 9,9-bis(3-aminophenyl)fluorene and 1,4-bis(4-aminophenoxy)benzene, with a mixing molar ratio of 5:5 and masses of 1.7422 g and 1.4617 g respectively, and the thermal imidization temperature is controlled at 200℃. Figure 1 TPI-200).

[0087] Example 4-2

[0088] The difference between the preparation method in this embodiment and that in Example 4-1 is that the thermal imidization temperature in step (3) is 250℃. Figure 1 TPI-250).

[0089] Example 4-3

[0090] The difference between the preparation method in this embodiment and that in Example 4-1 is that the thermal imidization temperature in step (3) is 280℃. Figure 1 TPI-280).

[0091] Example 4-4

[0092] The difference between the preparation method in this embodiment and that in Example 4-1 is that the thermal imidization temperature in step (3) is 300℃. Figure 1 TPI-300).

[0093] Examples 4-5

[0094] The difference between the preparation method in this embodiment and that in Example 4-1 is that the thermal imidization temperature in step (3) is 350℃. Figure 1 TPI-350).

[0095] Example 5-1

[0096] The difference between the preparation method of this embodiment and that of Example 1-1 is that the diamine in step (1) is replaced with a mixed diamine of 9,9-bis(3-aminophenyl)fluorene and 1,4-bis(4-aminophenoxy)benzene, with a mixing molar ratio of 5:5 and masses of 1.7422 g and 1.4617 g respectively, and the thermal imidization temperature is controlled at 200℃. Figure 1 TPI-200).

[0097] Example 5-2

[0098] The difference between the preparation method in this embodiment and that in Example 5-1 is that the thermal imidization temperature in step (3) is 250℃. Figure 1 TPI-250).

[0099] Example 5-3

[0100] The difference between the preparation method in this embodiment and that in Example 5-1 is that the thermal imidization temperature in step (3) is 280℃. Figure 1 TPI-280).

[0101] Example 5-4

[0102] The difference between the preparation method in this embodiment and that in Example 5-1 is that the thermal imidization temperature in step (3) is 300℃. Figure 1 TPI-300).

[0103] Example 5-5

[0104] The difference between the preparation method in this embodiment and that in Example 5-1 is that the thermal imidization temperature in step (3) is 350℃. Figure 1 TPI-350).

[0105] Example 6-1

[0106] The difference between the preparation method of this embodiment and that of Example 1-1 is that the diamine in step (1) is replaced with a mixed diamine of 9,9-bis(3-aminophenyl)fluorene and 1,4-bis(4-aminophenoxy)benzene, with a mixing molar ratio of 5:5 and masses of 1.7422 g and 1.4617 g respectively, and the thermal imidization temperature is controlled at 200℃. Figure 1 TPI-200).

[0107] Example 6-2

[0108] The difference between the preparation method in this embodiment and that in Example 6-1 is that the thermal imidization temperature in step (3) is 250℃. Figure 1 TPI-250).

[0109] Example 6-3

[0110] The difference between the preparation method in this embodiment and that in Example 6-1 is that the thermal imidization temperature in step (3) is 280℃. Figure 1 TPI-280).

[0111] Example 6-4

[0112] The difference between the preparation method in this embodiment and that in Example 6-1 is that the thermal imidization temperature in step (3) is 300℃. Figure 1 TPI-300).

[0113] Example 6-5

[0114] The difference between the preparation method in this embodiment and that in Example 6-1 is that the thermal imidization temperature in step (3) is 350℃. Figure 1 TPI-350).

[0115] Example 7-1

[0116] The difference between the preparation method of this embodiment and that of Example 1-1 is that the diamine in step (1) is replaced with a mixed diamine of 3,3-bis(4-aminophenyl)phthalide and 4,4-diaminodiphenyl sulfide, with a mixing molar ratio of 5:5 and masses of 1.5818 g and 1.0815 g respectively, and the thermal imidization temperature is controlled at 200℃ (TPI-200).

[0117] Example 7-2

[0118] The difference between the preparation method in this embodiment and that in Example 7-1 is that the thermal imidization temperature in step (3) is 250℃. Figure 1 TPI-250).

[0119] Example 7-3

[0120] The difference between the preparation method in this embodiment and that in Example 7-1 is that the thermal imidization temperature in step (3) is 280℃. Figure 1 TPI-280).

[0121] Example 7-4

[0122] The difference between the preparation method in this embodiment and that in Example 7-1 is that the thermal imidization temperature in step (3) is 300℃. Figure 1 TPI-300).

[0123] Example 7-5

[0124] The difference between the preparation method in this embodiment and that in Example 7-1 is that the thermal imidization temperature in step (3) is 350℃. Figure 1 TPI-350).

[0125] Example 8-1

[0126] The difference between the preparation method of this embodiment and that of Example 1-1 is that the dianhydride in step (1) is replaced with a mixed dianhydride of 2,2,3',3-biphenyltetracarboxylic dianhydride and bisphenol A type diether dianhydride, with a mixing molar ratio of 5:5 and masses of 1.4711 g and 2.6025 g respectively, and the thermal imidization temperature is controlled at 200℃. Figure 1 TPI-200).

[0127] Example 8-2

[0128] The difference between the preparation method in this embodiment and that in Example 8-1 is that the thermal imidization temperature in step (3) is 250℃. Figure 1 TPI-250).

[0129] Example 8-3

[0130] The difference between the preparation method in this embodiment and that in Example 8-1 is that the thermal imidization temperature in step (3) is 280℃. Figure 1 TPI-280).

[0131] Example 8-4

[0132] The difference between the preparation method in this embodiment and that in Example 8-1 is that the thermal imidization temperature in step (3) is 300℃. Figure 1 TPI-300).

[0133] Example 8-5

[0134] The difference between the preparation method in this embodiment and that in Example 8-1 is that the thermal imidization temperature in step (3) is 350℃. Figure 1 TPI-350).

[0135] Comparative Example 1-1

[0136] The difference between the preparation method of this embodiment and that of Example 1-1 is that the dianhydride in step (1) is replaced with pyromellitic dianhydride, and the diamine is replaced with 4,4'-diaminodiphenyl ether, with a molar ratio of 10:10 and masses of 2.1812 g and 2.0024 g respectively, and the thermal imidization temperature is controlled at 200℃. Figure 1 TPI-200).

[0137] Comparative Examples 1-2

[0138] The difference between the preparation method in this embodiment and that in Example 1-1 is that the thermal imidization is controlled at 250°C. Figure 1 TPI-250).

[0139] Comparative Examples 1-3

[0140] The difference between the preparation method in this embodiment and that in Example 1-1 is that the thermal imidization is controlled at 280℃. Figure 1 TPI-280).

[0141] Comparative Examples 1-4

[0142] The difference between the preparation method in this embodiment and that in Example 1-1 is that the thermal imidization is controlled at 300℃. Figure 1 TPI-300).

[0143] Comparative Examples 1-5

[0144] The difference between the preparation method in this embodiment and that in Example 1-1 is that the thermal imidization is controlled at 350℃. Figure 1 TPI-350).

[0145] Comparative Example 2-1

[0146] The difference between the preparation method in this embodiment and that in Example 1-1 is that the thermal imidization process is controlled to increase the temperature to 100°C at a rate of 5°C / min and hold it at that temperature for 1 hour; then the temperature is increased to 180°C at a rate of 5°C / min.

[0147] Example 1

[0148] The present invention utilizes the thermoplastic polyimide in the above embodiments and comparative examples to achieve temporary bonding of ultrathin wafers, and the process is as follows:

[0149] (1) The thermoplastic polyimide prepared in the above examples and comparative examples was redissolved in DMAc solvent, and spin-coated onto a silicon wafer at 1000 rpm for 30 s. After curing at 180°C for 2 h, a first substrate was formed.

[0150] (2) Dissolve the adhesive silicone resin in DMAc solvent and spread it evenly on the glass substrate using the same spin coating method to obtain the second substrate;

[0151] (3) The first substrate and the second substrate are bonded at room temperature in a bonding machine (vacuum degree 1 atm, bonding time 3 min), and then placed in a drying oven at 180°C for 40 min for heat treatment to crosslink and solidify the bonding material to obtain a bonded wafer pair.

[0152] Effect test:

[0153] (1) As Figure 3 , Figure 4 As shown, the heat resistance and 355nm ultraviolet absorption performance of the thermoplastic polyimides prepared in Examples 1-1 to 1-5 were determined by TGA and UV-Vis, respectively. The sample amount for TGA testing should be controlled between 10 and 20 mg, and 3 to 6 sets of tests should be conducted in parallel. The ultraviolet absorption performance (film transmittance) for UV-Vis testing should also be tested in parallel between 3 and 6 sets.

[0154] (2) Figure 5 As shown, the bonding interface uniformity of the bonded wafer pairs prepared in Examples 1-1 to 1-5 was tested using ultrasonic scanning microscopy (SAM).

[0155] (3) The debonding of the bonding pairs prepared in Examples 1-1 to 1-5 was tested using a 355nm laser beam.

[0156] Results Explanation:

[0157] Figure 3 The figure shows the thermogravimetric analysis (TGA) curves of thermoplastic polyimides prepared at different thermal imidization temperatures in Examples 1-1 to 1-5. It can be seen from the figure that the 5% thermogravimetric loss temperatures at curing temperatures of 200, 250, 280, 300, and 350°C are respectively: T 5％ =423.2, 537.8, 544.4, 540.8, 540.4.

[0158] Figure 4 The figures show the UV-Vis curves of thermoplastic polyimides prepared at different thermal imidization temperatures in Examples 1-1 to 1-5. The figures show that the absorption rates of 355nm ultraviolet laser at curing temperatures of 200, 250, 280, 300, and 350℃ are 99.7%, 99.4%, 99.3%, 99.1%, and 98.7%, respectively.

[0159] Figure 5The images shown are SAM images of the bonded wafer pair prepared using the thermoplastic polyimide prepared in Example 1-1 before and after heat treatment in step (4); where Figure (a) is the image before heat treatment; and Figure (b) is the image after heat treatment. It can be seen from the figures that the uniformity of the bonding interface did not change significantly before and after heat treatment, that is, the bonded wafer pair can withstand high temperature processes.

[0160] Figure 6 The figure shown is the total thickness variation (TTV) graph after the thermoplastic polyimide spin-coated silicon wafer prepared in Example 1-1 in step (1). TTV = 0.6734 μm, indicating that the thickness distribution of the first substrate is uniform.

[0161] Figure 7 The image shown is an EDS image of a pure silicon wafer surface. Figure 8 The image shown is an EDS image of the bonded wafer prepared using the thermoplastic polyimide prepared in Example 1-1 in step (4) and the surface of the silicon wafer after debonding. It can be seen from the image that there is no residual adhesive on the surface of the wafer after debonding.

[0162] The heat resistance, solubility, 355nm UV absorptivity, and debonding energy of the bonded wafer pairs prepared by thermoplastic polyimide in the above embodiments and comparative examples are shown in Table 1. The debonding energy was obtained by the fully automated laser debonding equipment DSI-S-DB661.

[0163] Table 1

[0164]

[0165]

[0166] From Table 1 and Figure 2 As can be seen from the above, among the bonded wafer pairs prepared by thermoplastic polyimide provided by the present invention, Example 1 has the lowest debonding energy density under the condition of satisfying the process application.

[0167] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing thermoplastic polyimide, characterized in that, Includes the following steps: (1) Polyamic acid, a polyimide precursor, is obtained by copolymerizing diamine and dianhydride; (2) The polyamic acid obtained in step (1) is subjected to thermal imidization to obtain thermoplastic polyimide; The temperature of the thermal imidization is 200℃~350℃, and the curing time of the thermal imidization is 0.5 h~10 h. The types of diamine and dianhydride are selected from any of the following combinations: ① A mixture of 2,3,3',4'-diphenyl ether tetracarboxylic dianhydride and 2,3,3',4'-biphenyl tetracarboxylic dianhydride; a mixture of 9,9-bis(4-aminophenyl)fluorene and 1,3-bis(4'-aminophenoxy)benzene; ②A mixed dianhydride of 2,3,3',4'-diphenyl ether tetracarboxylic dianhydride and 2,3,3',4'-biphenyl tetracarboxylic dianhydride; a mixed diamine of 9,9-bis(4-aminophenyl)fluorene and 1,3-bis(3-aminophenoxy)benzene; ③ A mixture of 2,3,3',4'-diphenyl ether tetracarboxylic dianhydride and 2,3,3',4'-biphenyl tetracarboxylic dianhydride; a mixture of 9,9-bis(4-aminophenyl)fluorene and 4,4-diaminodiphenyl ether; ④ A mixture of 2,3,3',4'-diphenyl ether tetracarboxylic dianhydride and 2,3,3',4'-biphenyl tetracarboxylic dianhydride; a mixture of 9,9-bis(3-aminophenyl)fluorene and 1,4-bis(4-aminophenoxy)benzene; ⑤ A mixture of 2,3,3',4'-diphenyl ether tetracarboxylic dianhydride and 2,3,3',4'-biphenyl tetracarboxylic dianhydride; a mixture of 3,3-bis(4-aminophenyl)phthalide and 4,4-diaminodiphenyl sulfide diamine; ⑥ A mixture of 2,2,3',3-biphenyltetracarboxylic dianhydride and bisphenol A type diether dianhydride; a mixture of 9,9-bis(4-aminophenyl)fluorene and 1,3-bis(4'-aminophenoxy)benzene; In step (2), the thermal imidization is a multi-stage stepped heating process, with each temperature step spaced 50~100℃ apart; the heating rate of each stage is 4~20℃ / min; the holding time of each stage is 60~210 min; the heating stage includes two or more temperature steps.

2. The preparation method according to claim 1, characterized in that, The preparation method of the thermoplastic polyimide specifically includes the following steps: In a protective atmosphere, diamine is dissolved or mixed in a polar organic solvent, dianhydride is added and stirred to allow it to condense and polymerize to form a polyamic acid solution; then it is heated to 200°C to 350°C in a stepwise heating rate of 4~20°C / min to obtain the thermoplastic polyimide.

3. The preparation method according to claim 2, characterized in that, The polar organic solvent is selected from any one or more of N,N-dimethylacetamide, N,N-dimethylformamide, N-methyl-2-pyrrolidone, dimethyl sulfoxide, tetrahydrofuran, m-cresol, and γ-butyrolactone.

4. The preparation method according to claim 1, characterized in that, The molar ratio of the diamine to the dianhydride is 0.95 to 1.

05.

5. The thermoplastic polyimide obtained by the preparation method according to any one of claims 1-4, characterized in that, The decomposition temperature of the thermoplastic polyimide T d >510℃; 355 nm ultraviolet light absorption rate >96%.

6. The application of the thermoplastic polyimide according to claim 5 in temporary bonding technology.

7. The method for temporary bonding of ultrathin wafers using thermoplastic polyimide as described in claim 5, characterized in that, Includes the following steps: A laminate comprising a first substrate and a second substrate temporarily bonded together by the thermoplastic polyimide and an adhesive material; and a process of heating the adhesive material to cure it.

8. The method according to claim 7, characterized in that, The method of providing the laminate comprising a first substrate and a second substrate temporarily bonded together by the thermoplastic polyimide and an adhesive material is to apply the thermoplastic polyimide onto the first substrate at a rotation speed of 500-3000 rpm. The adhesive material is applied to the second substrate at a rotation speed of 500~3000 rpm; the thermoplastic polyimide and adhesive material coated on the first and second substrates are bonded together to form a bonding pair.

9. The method according to claim 8, characterized in that, The bonding process for forming bond pairs is carried out at room temperature.

10. The method according to claim 8, characterized in that, The bonding process to form bond pairs is carried out under vacuum conditions.

11. The method according to claim 7, characterized in that, During the process of heating the adhesive material to cure it, the heating temperature is 150~200℃.

12. The method according to claim 8, characterized in that, It also includes a process of heating the thermoplastic polyimide coated on the first substrate to cure it; the heating temperature is 150~200℃.

13. The debonding method of the temporary bonding method for ultrathin wafers according to claim 7, characterized in that, The step includes the step of degrading the cured thermoplastic polyimide under ultraviolet light irradiation.

14. The debonding method according to claim 13, characterized in that, The wavelength of the ultraviolet light is 280~400nm.

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