Temporary bonding substrate and method for manufacturing temporary bonding substrate

Abstract

Provided is a temporary bonding substrate that suitably suppresses the formation of cracks when a semiconductor chip is temporarily bonded. The temporary bonding substrate is composed of a ceramic sintered body and has a predetermined bonded object that is temporarily bonded on one main surface thereof. The temporary bonding substrate comprises, in at least a part of an outer peripheral portion that is an annular portion ranging up to a predetermined width from a side end portion, with a small particle diameter region in which the crystal particle diameter of the main component ceramic particles is smaller than the crystal particle diameter of the main component ceramic particles in a main portion other than the outer peripheral portion.

Description

Temporary fixing substrate and method for manufacturing a temporary fixing substrate

[0001] This invention relates to a temporary fixing substrate used in the manufacturing process of semiconductor packages.

[0002] One example of semiconductor package manufacturing technology is FOWLP (Fan-out Wafer Level Package) technology. FOWLP technology generally involves the steps of: performing resin molding on a temporary substrate to which a semiconductor chip is temporarily fixed with adhesive; grinding the resin mold to expose the electrode ends of the semiconductor chip; forming a thin film redistribution layer (multilayer wiring) and solder balls on the surface where the electrode ends are exposed; and separating individual packages and peeling them from the temporary substrate, thereby obtaining a semiconductor package that is lower in height than conventional packages.

[0003] In the FOWLP technology, an embodiment using a translucent ceramic substrate as a temporary fixing substrate for the chip is already known (see, for example, Patent Document 1). The translucent ceramic substrate possesses all the requirements for a temporary fixing substrate, including high flatness necessary for electrode end exposure, high rigidity and reverse curvature necessary for suppressing warping during multilayer wiring formation, translucency that allows laser light for curing the adhesive to pass through, and chemical resistance for cleaning and reuse after use.

[0004] However, conventional temporary fixing substrates had a problem in that cracks would develop and propagate from the outer edge toward the side edge when semiconductor chips were mounted (temporarily fixed) onto them. When semiconductor chips are mounted onto a temporary fixing substrate, both the temporary fixing substrate, which is adsorbed and fixed to a predetermined support base, and the semiconductor chip to be mounted are heated. It is believed that the cracks are caused by thermal shock due to the temperature difference between the temporary fixing substrate and the semiconductor chip. Furthermore, it has been confirmed that such cracks are more likely to occur the closer the chip is mounted to the outer edge of the temporary fixing substrate, and are particularly likely to occur around the notch (notch area) when a notch is provided on the outer edge.

[0005] Patent No. 6430081

[0006] The present invention has been made in view of the above problems, and aims to realize a temporary fixing substrate that effectively suppresses the occurrence of cracks when a predetermined object to be fixed, such as a semiconductor chip, is temporarily fixed.

[0007] To solve the above problems, a first aspect of the present invention is a temporary fixing substrate made of a sintered ceramic body, on which a predetermined object to be fixed is temporarily fixed on one main surface, comprising an outer peripheral portion which is an annular portion within a predetermined width range from the side edge, and a main portion which is the portion other than the outer peripheral portion, characterized in that at least a part of the outer peripheral portion is provided with a small particle size region in which the crystal grain size of the main component ceramic particles is smaller than the crystal grain size of the main component ceramic particles in the main portion.

[0008] A second aspect of the present invention is a temporary fixing substrate according to the first aspect, characterized in that a notch is provided at the side end, and the small particle size region includes the portion where the notch is formed.

[0009] A third aspect of the present invention is a temporary fixing substrate according to the first or second aspect, characterized in that the crystal grain size of the main component ceramic particles in the small particle size region is 4.5 μm or less.

[0010] A fourth aspect of the present invention is a temporary fixing substrate according to the third aspect, characterized in that the entire outer periphery is the small particle size region.

[0011] A fifth aspect of the present invention is a temporary fixing substrate according to the fourth aspect, characterized in that the crystal grain size of the main component ceramic particles in the main portion is 4.5 μm or larger.

[0012] A sixth aspect of the present invention is a temporary fixing substrate according to the second aspect, characterized in that only a portion of the outer periphery including the notch formation portion is the small particle size region.

[0013] A seventh aspect of the present invention is a temporary fixing substrate according to the sixth aspect, characterized in that the crystal grain size of the main component ceramic particles in the small particle size region is 4.5 μm or less.

[0014] An eighth aspect of the present invention is a temporary fixing substrate according to the sixth or seventh aspect, characterized in that the crystal grain size of the main component ceramic particles in the outer peripheral portion other than the main portion and the small particle size region is larger than the crystal grain size of the main component ceramic particles in the small particle size region and is 5 μm or less.

[0015] A ninth aspect of the present invention is a temporary fixing substrate according to the first or second aspect, characterized in that the predetermined width range is 1% or more and 10% or less of the radius of the temporary fixing substrate.

[0016] A tenth aspect of the present invention is a temporary fixing substrate according to the first or second aspect, characterized in that the main component of the ceramic is alumina.

[0017] An eleventh aspect of the present invention is a method for manufacturing a temporary fixing substrate on which a predetermined object to be fixed is temporarily fixed on one main surface, comprising: a molding step of producing a plate-shaped molded body containing ceramic powder; a pre-calcination step of pre-calcining the molded body in the atmosphere; an outer periphery processing step of applying an Mg-containing substance to at least a portion of the outer periphery of the calcined body obtained in the pre-calcination step; a secondary calcination step of calcining the calcined body that has undergone the outer periphery processing step in the atmosphere; and a final calcination step of firing the calcined body that has undergone the secondary calcination step in a hydrogen atmosphere to obtain a temporary fixing substrate which is a sintered ceramic body, wherein in the final calcination step, a small particle size region is formed in at least a portion of the outer periphery, which is an annular portion within a predetermined width range from the side edge of the temporary fixing substrate, corresponding to at least a portion of the outer periphery of the calcined body to which the Mg-containing substance was applied in the outer periphery processing step, in which the crystal grain size of the main component ceramic particles is smaller than the crystal grain size of the main component ceramic particles in the main portion which is a portion other than the outer periphery.

[0018] A twelfth aspect of the present invention is a method for manufacturing a temporary fixed substrate according to the eleventh aspect, wherein the Mg-containing substance is an aqueous solution containing Mg, and in the peripheral treatment step, the aqueous solution containing Mg is permeated into at least a portion of the area by immersion in the aqueous solution containing Mg, dropping the aqueous solution containing Mg, or spray coating the aqueous solution containing Mg.

[0019] A thirteenth aspect of the present invention is a method for manufacturing a temporary fixed substrate according to the eleventh or twelfth aspect, characterized in that the main component of the ceramics is alumina.

[0020] According to the first to thirteenth aspects of the present invention, the occurrence of cracks in a temporary fixing substrate when a predetermined object to be fixed, such as a semiconductor chip, is temporarily fixed is suitably suppressed.

[0021] Figure 1 is a plan view of the surface 1a of the temporary fixed substrate 1. Figure 2 is a schematic flow diagram showing the manufacturing process of the temporary fixed substrate 1. Figure 3 shows the results of a confirmation experiment for the formation of a small particle size region. Figure 4 is a schematic diagram showing the spray coating of an Mg-containing aqueous solution. Figure 5 is a schematic diagram showing the crack test.

[0022] <Temporary Fixing Substrate> Figure 1 is a plan view of one main surface (surface) 1a of a temporary fixing substrate 1, which is one embodiment of the support substrate according to the present invention. The temporary fixing substrate 1 is a substrate on which a semiconductor chip is temporarily fixed when manufacturing a semiconductor package using FOWLP (Fan-out Wafer Level Package) technology, for example.

[0023] The temporary fixed substrate 1 is a disc-shaped translucent ceramic substrate with a diameter of several hundred mm (e.g., 300 mm), a thickness of several hundred μm to several mm (e.g., 1 mm), an in-plane thickness difference of several μm or less (e.g., within 3 μm), and a warp of several hundred μm or less (e.g., 200 μm).

[0024] In this embodiment, a translucent ceramic is defined as a ceramic having a forward total light transmittance (hereinafter also simply referred to as transmittance) of 20% or more across the entire wavelength range from 200 nm to 1500 nm. Examples of such translucent ceramics include alumina, silicon nitride, aluminum nitride, and silicon oxide.

[0025] For example, a sintered substrate mainly composed of alumina with a transmittance of 70% or more at a wavelength of 1000 nm is a suitable example of the temporary fixing substrate 1. When alumina is the main component, it is preferable to use high-purity alumina powder of 99.9% or more (preferably 99.95% or more) as the raw material, and to such alumina powder, magnesia (magnesium oxide, MgO) and zirconia (ZrO) as a sintering aid are added. ２ ) and Yttria (Y ２ O ３ It is preferable that ) be added.

[0026] The surface 1a, which is the placement surface of the semiconductor chip, and the other main surface (back surface) 1b are both pre-polished to become flat polished surfaces with low surface roughness. More specifically, the surface 1a and back surface 1b achieve an in-plane thickness difference of a few micrometers or less and an arithmetic mean roughness Ra of 100 nm or less (preferably 20 nm or less). More specifically, both the surface 1a and back surface 1b are surfaces that have been lapped. There is no particular limit to the lower limit of the arithmetic mean roughness Ra of the surface 1a and back surface 1b, but 1 nm is sufficient for practical purposes.

[0027] Furthermore, the temporary fixing substrate 1 may have a notch (cutout) 1n at a predetermined position on the side edge 1e for use in positioning and other purposes in subsequent processes. Figure 1 shows the shape of the side edge 1e when such a notch 1n is provided with a solid line, and the shape of the side edge 1e before such a notch 1n is provided (or when the notch 1n is not provided) with a dashed line. In this embodiment, unless otherwise specified, the temporary fixing substrate 1 with the notch 1n is also simply referred to as the temporary fixing substrate 1.

[0028] In addition, in the temporary fixing substrate 1 according to this embodiment, the outer peripheral portion 2, which is an annular portion within a predetermined width a range from the side edge 1e, is a small particle size region RE in which the crystal grain size (average particle size) of the ceramic particles is smaller than that of the portion other than the outer peripheral portion 2 (hereinafter also referred to as the main portion 1m). Hereafter, unless otherwise specified, ceramic particles and their crystal grain size refer to the particles and crystal grain size of the main component ceramics.

[0029] The small particle size region RE is intentionally provided to prevent cracks from occurring in the temporary fixing substrate 1 during the semiconductor chip mounting (temporary fixing) process, which is one of the steps in the semiconductor package manufacturing process when the temporary fixing substrate 1 is used in that process.

[0030] Generally, in sintered ceramic substrates, the smaller the grain size, the higher the material strength. For example, Table 1 shows the transmittance and flexural strength of four types of translucent ceramic substrates with different grain sizes, each with a thickness of 1 mm, along with the grain size. The raw material composition of the translucent ceramic substrates was alumina: 99.9 wt%, magnesium oxide: 0.03 wt%, zirconia: 0.05 wt%, and yttria: 0.005 wt%. The grain size was varied by changing the firing temperature and firing time. The flexural strength was determined by performing a four-point bending test.

[0031]

[0032] Table 1 shows that the flexural strength tends to increase with decreasing grain size. However, it also shows that the transmittance tends to decrease with decreasing grain size.

[0033] In this embodiment, taking into consideration this tendency and the fact that cracks tend to occur from the outer peripheral portion 2 to the side edge 1e of the temporary fixing substrate 1 when mounting semiconductor chips, the outer peripheral portion 2 of the temporary fixing substrate 1 is made into a small-grain region RE, which has a smaller crystal grain size than the main portion 1m and therefore has higher material strength compared to the main portion 1m. As a result, the temporary fixing substrate 1 according to this embodiment has suitably suppressed the occurrence of cracks from the outer peripheral portion 2 to the side edge 1e caused by thermal shock that occurs when semiconductor chips are mounted.

[0034] However, the crystal grain size d0 of the main part 1m shall be 4.5 μm or more and 50 μm or less. The reason for setting the crystal grain size d0 to 4.5 μm or more is to ensure light transmittance, and the reason for setting it to 50 μm or less is to ensure the strength of the main part 1m itself.

[0035] Preferably, the main part 1m and the small particle size region RE are provided such that the crystal grain size d1 in the small particle size region RE is 0.5 μm or more and 4.5 μm or less. If the crystal grain size d1 is 0.5 μm or more, sufficient sintering is achieved, and it is possible to suppress a decrease in the strength of the small particle size region RE due to insufficient sintering. Further, if the crystal grain size d1 is 4.5 μm or less, higher strength is ensured in the small particle size region RE. More preferably, the main part 1m and the small particle size region RE are provided such that the ratio d1 / d0 is 75% or more and 90% or less. In such a case, the occurrence of cracks when mounting the semiconductor chip is more reliably suppressed.

[0036] The width a of the outer peripheral part 2 that is the small particle size region RE may be 1% or more and 10% or less of the radius r of the temporary fixing substrate 1, and it is preferable that the width a is larger than the width of the notch 1n in the radial direction of the temporary fixing substrate 1.

[0037] The formation of the small particle size region RE is performed during the manufacturing process of the temporary fixing substrate 1 described later. Various methods can be applied to the formation of the small particle size region RE.

[0038] In the case of the temporary fixing substrate 1 provided with the notch 1n, the small particle size region RE is provided so as to include the existence range of the notch 1n (so that the notch 1n fits within the width of the small particle size region RE). This is because it is considered that stress is concentrated particularly in the vicinity of the notch 1n among the outer peripheral part 2, and there is a high risk of cracks occurring.

[0039] Alternatively, when the notch 1n is provided, instead of making the entire outer peripheral part 2 the small particle size region RE, a mode may be adopted in which at least only a predetermined range of notch part 2n including the existence range of the notch 1n is the small particle size region RE. However, in this case, in order to suppress the risk of crack generation other than in the notch part 2n, it is preferable that the crystal grain size of the main part 1m and the outer peripheral part 2 other than the notch part 2n is larger than the crystal grain size in the small particle size region RE and 5 μm or less.

[0040] In the present embodiment, the notch portion 2n is a partial region of the temporary fixing substrate 1 including at least the notch 1n, and is a region with a predetermined width a from the side end portion 1e in a sector region having a central angle θ with the same center O and radius r as the temporary fixing substrate 1. The central angle θ may be appropriately determined according to the shape and size of the notch 1n.

[0041] <Manufacturing process of the temporary fixing substrate> Next, an example of the manufacturing process of the temporary fixing substrate 1 including the small particle size region RE will be described. FIG. 2 is a flowchart schematically showing the manufacturing process of such a temporary fixing substrate 1. The temporary fixing substrate 1 is generally manufactured through a molded body manufacturing step (step S1), a preliminary calcination step (step S2), an outer peripheral processing step (step S3), a secondary calcination step (step S4), a main firing step (step S5), an end processing step (step S6), and a polishing step (step S4).

[0042] In manufacturing the temporary fixing substrate 1, first, a molded body mainly composed of ceramic powder is produced (step S1). From the viewpoint of suitably ensuring the light transmittance in the temporary fixing substrate 1, it is preferable to use high-purity ceramic powder. Examples of the method for producing the molded body include known methods such as the mold casting method, the tape casting method, the doctor blade method, and the extrusion method.

[0043] Next, the produced molded body is preliminarily calcined (step S2). The preliminary calcination step is preferably performed at a temperature of 1000°C to 1300°C in the atmosphere. In the preliminary calcination step, organic components are desorbed, and a disk-shaped ceramic calcined body close to the temporary fixing substrate 1 is obtained.

[0044] Such a disk-shaped ceramic calcined body is subjected to outer peripheral processing (step S3). The outer peripheral processing is a process performed on the portion of the outer periphery of the ceramic calcined body obtained by preliminary calcination corresponding to the small particle size region RE in the temporary fixing substrate 1 in order to provide the small particle size region RE in the temporary fixing substrate 1 as a finished product.

[0045] In this embodiment, as an outer periphery treatment, a Mg-containing substance is intentionally applied from the outside to the outer periphery of the ceramic calcined body obtained by pre-calcination, thereby forming a desired small particle size region RE on the outer periphery 2 of the final temporary fixed substrate 1. The Mg-containing substance is, for example, a solution or paste containing an Mg compound.

[0046] The Mg-containing material should be applied to the portion of the outer periphery 2 that corresponds to the small particle size region RE, which is desired to be present in the final temporary fixed substrate 1. For example, if only the notch portion 2n is designated as the small particle size region RE, the Mg-containing material should be applied only to the portion of the ceramic calcined body that corresponds to the notch portion 2n.

[0047] One example of such an outer perimeter treatment is a penetration treatment in which a predetermined Mg-containing aqueous solution is permeated into the interior of a ceramic calcined body on its outer perimeter. The Mg-containing aqueous solution may be magnesium nitrate (Mg(NO)). ３ ) ２ Examples include aqueous solutions. When these aqueous solutions are used, the concentration of the aqueous solution should be between 0.1 wt% and 50 wt%. Furthermore, various methods are exemplified for the penetration treatment, such as immersion of the area to be treated in an aqueous solution containing Mg, or dropping or spraying the aqueous solution containing Mg onto the area using a dispenser. It has been experimentally confirmed in advance that this treatment suppresses the grain growth of the main component ceramic particles and allows for the suitable formation of a small particle size region RE.

[0048] Another example of the outer perimeter treatment is a coating process in which a paste containing a magnesium-containing substance (e.g., magnesia) is applied to the outer perimeter of the ceramic calcined body by a method such as printing.

[0049] These sintered bodies, after undergoing the outer perimeter treatment, are subjected to a secondary calcination process (step S4) under the same conditions as the pre-calcination process, followed by a final calcination process (step S5) in a hydrogen atmosphere at a calcination temperature of 1600°C to 1900°C. This yields a temporary fixed substrate 1 with a small particle size region RE.

[0050] Furthermore, following the main firing process, the obtained temporary fixed substrate 1 may be further annealed in a hydrogen furnace for the purpose of adjusting (correcting) warping. The annealing treatment is preferably performed at a temperature within ±100°C of the maximum temperature during the main firing, and more preferably at 1900°C or lower, from the viewpoint of preventing deformation and abnormal grain growth while promoting the discharge of sintering aids. The annealing time is preferably 1 to 6 hours.

[0051] The obtained temporary fixed substrate 1 is subjected to an edge processing process (step S6) and a polishing process (step S4). The edge processing process includes chamfering (beveling) of the side edge 1e and forming a notch 1n. In the polishing process, the surface 1a and back surface 1b are subjected to grinding with a grinder and lapping with diamond abrasive grains.

[0052] By going through the above process, a temporary fixing substrate 1 is obtained in which the outer peripheral portion 2 or the notched portion 2n is a high-strength, small-particle-grain region RE. In other words, a temporary fixing substrate 1 is obtained in which the occurrence of cracks when semiconductor chips are mounted is suitably suppressed.

[0053] <Modification> In the above-described embodiment, a small particle size region RE is formed on the outer periphery 2 of the temporary fixed substrate 1 by methods such as penetration of an Mg-containing aqueous solution into the ceramic calcined body or application of a paste containing an Mg-containing substance. It is also possible to form a small particle size region RE by employing methods other than those described above.

[0054] For example, in the process of manufacturing a molded body, the concentration of the sintering aid may be different in the portion that will ultimately become the main part 1m and the portion that will become the outer periphery 2, thereby forming a small particle size region RE.

[0055] Furthermore, when manufacturing the molded body, alumina powders with different sintering temperatures may be used for the portion that will ultimately become the main part 1m and the portion that will become the outer periphery 2, thereby forming a small particle size region RE.

[0056] Alternatively, a small grain size region RE may be formed by creating a temperature gradient during the firing process, thereby differentiating the grain size of the main portion 1m and the outer peripheral portion 2.

[0057] <Confirmation experiment for the formation of small particle size regions> An experiment was conducted to confirm the formation of small particle size regions when the outer perimeter was treated using a magnesium nitrate aqueous solution as the Mg-containing aqueous solution.

[0058] First, several rectangular plate-shaped ceramic calcined bodies were pre-fabricated by performing the same processes as described above for the molded body and preliminary processes, except for the rectangular shape.

[0059] The raw material composition of the slurry used to obtain the molded product was as follows:

[0060] (Ceramic powder) α-alumina (purity 99.99%): 100 parts by weight; Magnesia (MgO): 250 ppm; Zirconia (ZrO) ２ ): 500 ppm; Yttria (Y ２ O ３ ): 10ppm.

[0061] (Dispersion medium) 2-ethylhexanol: 45 parts by weight.

[0062] (Binder) PVB resin: 4 parts by weight.

[0063] (Dispersant) Polymeric surfactant: 3 parts by weight.

[0064] (Plasticizer) DOP: 0.1 parts by weight.

[0065] The slurry prepared by kneading these raw materials was molded into a rectangular plate shape using the doctor blade method to obtain a molded body. The molded body was shaped so that the final temporary fixed substrate equivalent to the obtained object had a thickness of 1.1 mm.

[0066] Then, the resulting molded body was pre-fired in air at 1300°C for 2 hours to obtain a rectangular plate-shaped ceramic calcined body equivalent.

[0067] Next, five types of magnesium nitrate aqueous solutions with concentrations of 0%, 0.4 wt%, 0.8 wt%, 4 wt%, and 40 wt% (the 0% concentration solution was actually water) were prepared. Each solution was used to treat the outer perimeter of a different ceramic calcined body equivalent by immersing a 5 mm wide area from one side for 90 seconds. It was confirmed that after immersion, the magnesium nitrate aqueous solution had penetrated a 10 mm wide area of ​​the ceramic calcined body equivalent, including the initial immersion area.

[0068] Then, by subjecting the immersed ceramic calcined body equivalent to a secondary calcination process at 1300°C in air for 2 hours and a final calcination process at 1800°C in a hydrogen atmosphere for 2.5 hours, five types of temporary fixed substrate equivalents were obtained. In the final calcination process, the calcined body equivalent after the secondary calcination was placed on a molybdenum plate.

[0069] For each of the obtained temporary fixed substrate equivalents, an external photograph was taken, and further, magnified images (500x field of view) of the immersed area and the normal area (area other than the immersed area) were taken using an optical microscope. The crystal grain size (average grain size) was then determined from the magnified images using the intercept method.

[0070] The intercept method is a method for determining the average grain size by drawing a line of arbitrary length in an image where crystal grains can be identified, and dividing the length of the line by the number of crystal grains crossed by the line. However, in this method, the drawn line does not necessarily cross the center of the crystal grain, so it is common to multiply the above division value by a certain coefficient. In this verification experiment, 4 / π was used as the coefficient. That is, in this verification experiment, the average grain size was D, the length of the line was L, and the number of crystal grains crossed by the line was x, and the average grain size was calculated using the following formula. However, the length of the line L was set to 250 μm. D = (4 / π) × (L / x).

[0071] Figure 3 shows the results of the confirmation experiment for the formation of small particle size regions. In Figure 3, the concentration of the magnesium nitrate aqueous solution used for immersion, the appearance of the temporary fixed substrate equivalent obtained from the ceramic calcined body equivalent immersed in each magnesium nitrate aqueous solution, magnified partial images of the immersed and normal parts of each temporary fixed substrate equivalent, and the crystal grain size (average grain size) value obtained from each magnified partial image are shown in a list. However, for the temporary fixed substrate equivalent immersed in a 0% magnesium nitrate aqueous solution (i.e., water), only the results for the normal part are shown.

[0072] Figure 3 shows that while there are no significant differences in the appearance and grain size of the crystal grains in the normal section between the respective temporary fixed substrates, the images confirm that in the immersed section, the crystal grains tend to become smaller as the concentration of the magnesium nitrate aqueous solution used for immersion increases, and it is also evident that the actual grain size decreases.

[0073] This suggests that by performing a process to unevenly distribute Mg-containing material on the outer periphery of the ceramic calcined body as an outer periphery treatment, a small particle size region RE can be provided on the outer periphery 2 of the temporary fixed substrate 1.

[0074] <Crack Test> A test was conducted to confirm the crack suppression effect of providing a small particle size region RE. Specifically, six types of temporary fixing substrates 1 (Examples 1 to 6) were prepared according to the flow in Figure 2, in which the entire outer peripheral portion 2 was a small particle size region RE and the combination of the crystal grain size of the main portion 1m and the crystal grain size of the outer peripheral portion 2 was different, as was one type of temporary fixing substrate (Example 7) in which only the notch portion 2n was a small particle size region RE, and one type of temporary fixing substrate 1 without a small particle size region RE (Comparative Example 1). The presence or absence of cracks was evaluated by conducting a test that simulated the mounting of a semiconductor chip.

[0075] In the case of Example 7, notch 1n is not actually provided, and notch portion 2n is merely the area where notch 1n is planned to be formed, but for the sake of simplicity of explanation, it is simply referred to as notch portion 2n.

[0076] The raw material composition conditions for obtaining the molded body were the same as those used in the confirmation experiment for the formation of small particle size regions.

[0077] In all cases, the molded body was fabricated in a disc shape using the doctor blade method. Specifically, the slurry was molded into a rectangular shape and then cut out in a circular shape so that the final temporary fixed substrate would have a thickness of 1.1 mm and a diameter of 300 mm.

[0078] The conditions for pre-calcination and secondary calcination in air were the same as those used in the confirmation experiment for small particle size region formation described above. However, the conditions for the final calcination under a hydrogen atmosphere differed between the examples and comparative examples, as described below.

[0079] Example 1: 1650°C, 2.5 hours; Example 2, Example 7: 1650°C, 2.0 hours; Example 3, Example 5, Example 6: 1650°C, 3.0 hours; Example 4: 1650°C, 1.8 hours; Comparative Example 1: 1670°C, 3.0 hours.

[0080] Furthermore, in forming the small particle size region RE on the temporary fixed substrate 1 of Examples 1 to 6, a magnesium nitrate aqueous solution with a concentration of 40 wt% was used as the Mg-containing aqueous solution, and this magnesium nitrate aqueous solution was spray-coated onto the outer circumference of the disc-shaped ceramic calcined body after pre-calcination.

[0081] Figure 4 schematically shows the spray coating process of an Mg-containing aqueous solution. Spray coating of the Mg-containing aqueous solution can be performed, for example, by placing a ceramic calcined body 1α, with both main surfaces covered by a mask 102 except for the outer peripheral portion 2α of width a, on a horizontally rotatable turntable 101, and spraying the Mg-containing aqueous solution L from a spray gun 103 toward the outer peripheral portion 2α while rotating the turntable 101. In all of the examples, the value of width a was set to 5 mm, and the specific spraying times were varied as follows.

[0082] Example 1: 120 seconds; Example 2: 120 seconds; Example 3: 180 seconds; Example 4: 120 seconds; Example 5: 120 seconds; Example 6: 210 seconds.

[0083] Furthermore, the surface 1a and back surface 1b of the temporary fixed substrate 1 after the final firing were further ground with a grinder and lapped with diamond abrasive grains to adjust the thickness to 1.0 mm.

[0084] The temporary fixed substrate 1 of Example 7 was manufactured under the same conditions as in Example 2, except that, when spray coating with magnesium nitrate aqueous solution, the turntable 101 was not rotated, and the magnesium nitrate aqueous solution was irradiated only to the area corresponding to the notch portion 2n of the outer circumference 2α of the ceramic calcined body 1α.

[0085] The temporary fixed substrate 1 of Comparative Example 1 was prepared under the same conditions as in Example 1, except for the spray coating of the Mg-containing aqueous solution.

[0086] In the manner described above, multiple temporary fixing substrates 1 were fabricated for each of Examples 1 to 7 and Comparative Example 1.

[0087] For each of the temporary fixed substrates 1 obtained in Examples 1 to 7 and Comparative Example 1, the main portion 1m and the outer peripheral portion 2 (notch portion 2n in the case of Example 7) were captured as partial magnified images (500x field of view) using an optical microscope. Then, the crystal grain size (average grain size) was determined for each captured image using the intercept method.

[0088] A crack test was performed on the obtained temporary fixed substrate 1. Figure 5 is a schematic diagram showing the crack test.

[0089] In the crack test, the temporary fixed substrate 1 was first placed horizontally on the chuck table 201. Then, with the chuck table 201 heated to 80°C, a rectangular load piece 202, which mimics the bonding head of a semiconductor chip, was lowered from above as indicated by arrow AR while being heated to 260°C, thereby pressing down on the temporary fixed substrate 1. The presence or absence of cracks caused by thermal shock resulting from this pressing was checked. These tests were performed on 10 temporary fixed substrates 1 for each of Examples 1 to 8 and Comparative Example 1, and the frequency of crack occurrence was evaluated.

[0090] The planar size of the load piece 202 was set to 3 cm × 3 cm, and the distance d from the center O of the temporary fixing substrate 1 to the center position C of the pressing was set to 12.5 cm. More specifically, the distance dx in the x-axis direction was 12.5 cm, and the distance dy in the y-axis direction was 0 cm. Also, the pressing force was set to 5.4 N, and thereby, the pressure during pressing was 0.6 N / cm ２ This pressure value is larger than the pressure acting on the temporary fixing substrate 1 during the actual mounting of the semiconductor chip. Regarding Example 7, the center position C of the pressing was made to be closest to the notch portion 2n.

[0091] Table 2 lists the crystal grain sizes (average grain sizes) of the main part 1m and the outer peripheral part 2 of the temporary fixing substrate 1 in Examples 1 to 7 and Comparative Example 1 (for Example 7, the notch part 2n), the ratio of the crystal grain size of the outer peripheral part 2 to the crystal grain size of the main part 1m (average grain size ratio), and the results of the crack test.

[0092]

[0093] When no cracks occurred in all of the 10 temporary fixing substrates 1, it was determined that the resistance to cracks was sufficient, and an "〇" (circle) was marked in the "Crack test result" column of Table 2.

[0094] Also, when one or two of the temporary fixing substrates 1 in which cracks occurred, it was determined that the occurrence of cracks was suppressed to such an extent that there were no production problems, and a "△" (triangle) was marked in the "Crack test result" column of Table 2.

[0095] On the other hand, when three or more of the temporary fixing substrates in which cracks occurred, it was determined that the resistance to cracks was not sufficient, and an "×" (cross) was marked in the "Crack test result" column of Table 2.

[0096] As shown in Table 2, in all of the temporary fixing substrates 1 in Examples 1 to 6, the crystal grain size in the main part 1m was 4.5 μm or more, and the crystal grain size in the outer peripheral part 2 was smaller than the crystal grain size in the main part 1m. That is, in any of Examples 1 to 6, a temporary fixing substrate 1 in which the entire outer peripheral part 2 became a small grain size region RE was obtained.

[0097] In these embodiments, cracks did not occur in the temporary fixed substrate 1, or were suppressed to a degree that did not cause production problems.

[0098] On the other hand, in Comparative Example 1, where the grain size of the main portion 1m and the outer peripheral portion 2 were the same, cracks occurred in many of the temporary fixed substrates 1.

[0099] The above results demonstrate that by providing a small particle size region RE on the outer peripheral portion 2 of the temporary fixing substrate 1, cracks during semiconductor chip mounting can be effectively suppressed.

[0100] In particular, no cracks occurred in the temporary fixing substrate 1 in Examples 1, 2, and 4. This indicates that, in order to make the outer peripheral portion 2 of the temporary fixing substrate 1 a small particle size region RE for the purpose of suppressing cracks, it is more preferable to set the crystal grain size to 4.5 μm or less and the crystal grain size ratio to 75% or more and 90% or less. It should be noted that the transmittance of the temporary fixing substrate 1 in Example 4 was slightly insufficient compared to the other temporary fixing substrates 1.

[0101] Furthermore, the results from Example 7 confirm that even in a temporary fixing substrate 1 in which only the notch portion 2n has a reduced particle size, the occurrence of cracks when semiconductor chips are mounted can be suitably suppressed.

Claims

1. A temporary fixing substrate made of a sintered ceramic body, on which a predetermined object to be fixed is temporarily fixed on one main surface, comprising: an outer peripheral portion which is an annular portion within a predetermined width range from the side edge; and a main portion which is the portion other than the outer peripheral portion, wherein at least a part of the outer peripheral portion is provided with a small particle size region in which the crystal grain size of the main component ceramic particles is smaller than the crystal grain size of the main component ceramic particles in the main portion.

2. A temporary fixing substrate according to claim 1, characterized in that a notch is provided at the side end, and the small particle size region includes the portion where the notch is formed.

3. A temporary fixing substrate according to claim 1 or claim 2, characterized in that the crystal grain size of the main component ceramic particles in the small particle size region is 4.5 μm or less.

4. A temporary fixing substrate according to claim 3, characterized in that the entire outer periphery is the small particle size region.

5. A temporary fixing substrate according to claim 4, characterized in that the crystal grain size of the main component ceramic particles in the main portion is 4.5 μm or larger.

6. A temporary fixing substrate according to claim 2, characterized in that only a portion of the outer periphery including the notch formation portion is the small particle size region.

7. A temporary fixing substrate according to claim 6, characterized in that the crystal grain size of the main component ceramic particles in the small particle size region is 4.5 μm or less.

8. A temporary fixing substrate according to claim 6 or claim 7, characterized in that the crystal grain size of the main component ceramic particles in the outer peripheral portion other than the main portion and the small particle size region is larger than the crystal grain size of the main component ceramic particles in the small particle size region and is 5 μm or less.

9. A temporary fixing substrate according to claim 1 or claim 2, characterized in that the predetermined width range is 1% or more and 10% or less of the radius of the temporary fixing substrate.

10. A temporary fixing substrate according to claim 1 or claim 2, characterized in that the main component of the ceramic is alumina.

11. A method for manufacturing a temporary fixing substrate on which a predetermined object to be fixed is temporarily fixed on one main surface, comprising: a molding step of producing a plate-shaped molded body containing ceramic powder; a pre-calcination step of pre-calcining the molded body in the atmosphere; an outer perimeter processing step of applying a Mg-containing substance to at least a portion of the outer perimeter of the calcined body obtained in the pre-calcination step; a secondary calcination step of calcining the calcined body that has undergone the outer perimeter processing step in the atmosphere; and a final calcination step of firing the calcined body that has undergone the secondary calcination step in a hydrogen atmosphere to obtain a temporary fixing substrate which is a sintered ceramic body, wherein in the final calcination step, a small particle size region is formed in at least a portion of the outer perimeter, which is an annular portion within a predetermined width range from the side edge of the temporary fixing substrate, corresponding to at least a portion of the outer perimeter of the calcined body to which the Mg-containing substance was applied in the outer perimeter processing step, in which the crystal grain size of the main component ceramic particles is smaller than the crystal grain size of the main component ceramic particles in the main portion which is a portion other than the outer perimeter.

12. A method for manufacturing a temporary fixed substrate according to claim 11, wherein the Mg-containing substance is an aqueous solution containing Mg, and in the peripheral treatment step, the aqueous solution containing Mg is permeated into at least a portion of the area by immersion in the aqueous solution containing Mg, dropping the aqueous solution containing Mg, or spray coating the aqueous solution containing Mg.

13. A method for manufacturing a temporary fixed substrate according to claim 11 or claim 12, characterized in that the main component of the ceramics is alumina.

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