Method and apparatus for mounting slice base on wafer of semiconductor

Abstract: It is known that it is advantageous in the semiconductor wafer production to re-slice a semiconductor wafer having impurity diffusion layers on the both sides processed in advance. In the re-slice process, it is required to mount a thin slice base on the periphery of semiconductor wafer prior to the re-slicing process for protecting the periphery of wafer from chipping off damage during the re-slicing process by ID saw and the like. The present invention provides several examples of method and apparatus for mounting a slice base prepared in advance on the periphery of semiconductor wafer by utilizing the method and apparatus of the present invention, in addition it further provides another method and apparatus for molding and mounting simultaneously a mold type slice base by using a thermosetting type resin on the periphery of semiconductor as the molding material, whereby the re-slice process of semiconductor wafer is extremely improved in the production cost including labor saving.

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a method and apparatus for mounting a piece of thin slice-base on a semiconductor wafer, which was processed in advance to slice from a crude material such as silicon ingot and the like and further processed to form an impurity diffusion layers on the both sides in advance, more particularly for mounting the slice-base chip on the peripheral edge of semiconductor wafer additionally for protecting the lower end of semiconductor wafer from any chipping off during the re-slicing process from a sheet of the semiconductor wafer into two sheets for the purpose of manufacturing a substrate for discrete component which is used for a transistor, diode, discrete component and the like. 2. Description of the Prior Art Conventionally, the applicant of the present invention previously suggests that, in his Japanese patent provisional application No.Hei 1-293613, and also it is further known from the other prior art such as the Japanese patent provisional application No.Sho 64-19729 or U.S. patent No.4,261,781, that is, the idea of manufacturing substrates for discrete components by re-slicing a sheet of semiconductor wafer, which is formed with an impurity diffusion layers on the both sides in advance, into two sheets from at almost center portion of core thickness of the sheet in order to obtain two sheets of wafer having a impurity diffusion layer on one side and a plane surface on the other side, however, there are no suggestions to mount any thin slice bases on the periphery of their semiconductor wafer upon the completion of re-slicing process in the above prior art. In addition, the applicant of the present invention also suggests, in his Japanese patent application No.Hei 1-137037, a technology for re-slicing a semiconductor wafer having impurity diffusion layers on the both sides of the wafer processed in advance before the re-slicing process in order to improve the productivity of producing the semiconductor wafer. In the aforementioned suggestions by the applicant, as a suggested means of mounting the slice base on the peripheral edge of the wafer, for example it is conducted to mount the slice base with one by one by using an adhesive on the peripheral edge of the wafer aligned in advance on an wafer magazine. This conventional means, however, has the following disadvantages of that, as shown in Fig. 1, a slice base(P) tends to incline in advance from an wafer(W) until an adhesive(C) has been solidified wherein it causes a shortage of adhesive strength and errors in the accuracy of measurements between them, or as shown in Fig. 2, an adhesive falls in drops downward along an wafer surface wherein it causes an irregularity on the surface of wafer to spoil the workabilities of sequent processes. SUMMARY OF THE INVENTION In accordance with the present invention, it provides a method and apparatus for mounting a slice base capable of solving the aforementioned disadvantages of conventional way with a good workability when the slice base is mounted on the wafer of semiconductor. OBJECTS AND ADVANTAGES OF THE INVENTION Accordingly, it is a general object of the present invention to provide a process for forming a reinforcing material to a semiconductor wafer by using the reinforcing material as a substitute of aforementioned slice base to improve the workability of slicing process of an wafer with a good finish as well as to save the material cost. It is a more specific object of the present invention to provide a process and apparatus for forming the reinforcing material capable of performing a means of forming the reinforcing material in further high accuracy and high workability. It is another object of the present invention to provide a structure for mounting a slice base to a semiconductor wafer by enlarging the contact area of interface between the slice base and the semiconductor wafer for enhancing the contact strength between them. BRIEF DESCRIPTION OF THE DRAWINGS Fig.1 and Fig.2 are side views for showing the disadvantageous structure of conventional art relating to fix a slice base on a wafer of semiconductor; Fig.3 is a side view for showing a method for fixing the slice base of the first example of the present invention; Fig.4 is a front view of Fig.3; Fig.5 is an enlarged detail of Fig.3; Fig.6 and Fig.7 are expanded sectional side views for showing the process for re-slicing the wafer of semiconductor into two sheets; Fig.8 is a sectional side view for showing the process and apparatus for fixing the slice base on the wafer of semiconductor in the second example of the present invention; Fig.9 is a partly broken side view for showing the state of fixing a slice base on a wafer of semiconductor shown in Fig.8; Fig.10 is a sectional view for showing X-X line of Fig.9; Fig.11 is an enlarged detail of Fig.9; Fig.12 is a front view for showing the structure of slice base fixed on a wafer of semiconductor of the third example; Fig.13 is a sectional view for showing Y-Y line of Fig.12; Fig.14 is a front view for showing a modified example of fixing position of slice base; Fig.15 is a side view in enlarged detail for showing another modified example in the structure of fixing a slice base; Fig.16 is an enlarged sectional side view for showing the re-slicing process of semiconductor wafer in Fig.13; Fig.17 is a side view for showing a process for forming a slice base for semiconductor wafer in the fourth example of the present invention; Fig.18 is a sectional view for showing Z-Z line of Fig.17; Fig.19 and Fig.20 are sectional views enlarged in detail for showing a modified example of slice base respectively; Fig.21 is a front view for showing a state of inserting an wafer into an apparatus for forming a slice base of semiconductor wafer relating the fifth example; Fig.22 is a plan view for showing a molding groove of the apparatus in Fig.21; Fig.23 is a front view for showing a molding groove formed deeply in the center portion of groove; Fig.24 is a side view for showing a V-shaped guide slit of the apparatus; Fig.25 is a front view for showing the V-shaped guide slit of Fig.24; Fig.26 is a sectional view of a molding groove; Fig.27 is a side view for showing the V-shaped guide slit in the apparatus of Fig.21; Fig.28 is a front view for showing the V-shaped guide slit; Fig.29 is a vertical section for showing a state of forming a slice base in a molding groove; and Fig.30 is a vertical section for showing a state of forming a slice base fixed on two sheets of semiconductor wafer. DETAILED DESCRIPTION OF THE INVENTION EXAMPLE I. Fig.3 to Fig.5 show the first example of the present invention as a method for mounting a slice base to a semiconductor wafer. It is referred now in detail to the first example based on Fig.3 and Fig.4. In the first example, it comprises two kind of wafers such as a plurality of semiconductor wafer(W) and a plurality of spacing wafer(1) having a larger diameter than the semiconductor wafer, the spacing wafer(1) is only purposed to space between semiconductor wafers to separate each other. Providing these two kind wafers and aligning them one by one vertically in a concave groove(2') of an wafer bed(2) so as to place two sheets of spacing wafers(1)(1) to both sides of the alignment of these wafers(W)(1) as shown in Fig.3. Regarding the materials of these wafers(W)(1), the wafer(W) consists of a single crystal silicon ingot and formed as a disk shape sheet, and further processed in advance to have impurity diffusion layers on the both sides of the wafer respectively. The material of spacing wafer(1) is made from a material such as not receive any influence from the adhesive(C), for example, it is selected from a group consisting of a tetrafluoride ethylene resin, and the spacing wafer(1) is formed so as to contact closely with the semiconductor wafer(W). The material of the wafer bed(2) may be made of an adequate material, and preferably made of the same material with the spacing wafer(1 such as not receive any influence from the adhesive(C). In addition, pressing plates(3)(3) are provided to press the alignments of these wafers(W)(1) on the wafer bed(2) toward inside from both sides so as to hold the wafers' alignments between the both pressing plates(3)(3). The material of the pressing plates(3) (3) may be made by a suitable material, and preferably made by the same mater with the spacing wafer(1). To press the alignments of these wafers()(1) is necessary to prevent these wafers(W)(1) from the movement, inclining and divergence of each wafer by pressing and holding these wafers in the alignment as well as to reduce any gap occurred between them by contacting them closely as much as possible. After that, as shown in Figs.3, 4 and 5, an adhesive(C) is applied thickly on the peripheral edge surfaces of the semiconductor wafers(W) held between both spacing wafers(1)(1) wherein a slice base(P) is inserted between the both spacing wafers(1)(1) to mount the slice base(p) on the edge surface of the semiconductor wafer(W). It is preferable to apply the adhesive(C) on the upper edge portion of the semiconductor wafer(W) and it is also possible to use the orientation flat of the semiconductor wafer(W). It is also possible to apply the adhesive(C) in advance to the slice base but not to the semiconductor wafer(W). Regarding the material of the slice base(P), it is made of a carbon, a silicon, a quick hardening type cement and the like. As to the material of the adhesive(C), it is possible to use a thermosetting resin type adhesive such as epoxy type resin, polyester type resin such as having a good exfoliation property without losing scission property, polyamid type resin and the like, and also it is possible to use a rubber type adhesive. According to such the first example, since the spacing wafers(1) having a larger diameter than the semiconductor wafer(W) can assist to align and restrict the semiconductor wafer(W) with the slice base(1) by pressing from both sides, the plurality of the semiconductor wafers(W) with the slice base(P) can be fixed at accurate position on the wafer bed(2) without any damage of the semiconductor wafers(W) with the slice base(P), the shortage of fixing strength and error in the accuracy of measurement causing by the movement, incline, divergence and the like. In addition, since the combination of spacing wafers(1) put a sheet of the semiconductor wafer(W) between the spacing wafers(1) in the both sides, it can prevent the adhesive(C) from falling in drops along the both sides of the semiconductor wafer(W) by the existence of the spacing wafers(1) contacted closely with the semiconductor wafer(W) even if the adhesive(C) is overflown due to an excessive application to the edge surface of the semiconductor wafer(W). (shown in Fig.5) In Fig.6 and Fig.7, it is referred now in detail to the re-slicing process of semiconductor wafers(W) with respective slice base(P) aligned on the wafer bed(2) in combination with the spacing wafers(1) in the first example. In Fig.6, it shows an enlarged semiconductor wafer(W), which consists of the impurity diffusion layers(Wb) processed in advance in the both sides of the wafer(W) and a plane core portion(Wa) having no impurity diffusion layer(Wb), and which is re-sliced by slicing machine such as ID saw slicing machine, the ID saw is shown by the referential number(4) in Fig.6. This semiconductor wafer(W) is further re-sliced by the ID saw(4) to divide into two sheets of semiconductor wafers(W') having respective impurity diffusion layer(Wb) on one side and a plane surface(Wa') on the other side, that is, two sheets of substrates(W')(W') of discrete component can be produced simultaneously from one sheet of semiconductor wafer(W) having impurity diffusion layers(Wb) in the both sides processed in advance. According to this re-slicing process, it necessitates the kerf loss of wafer material during the cutting process by the saw, however, this re-slicing process has still advantage in the loss of material in comparison with the conventional method which the inventor referred to in his previous patent application. In the practice of the above re-slicing process, it may move either one of semiconductor wafer(W) or ID saw(4), and it may slice off completely throughout the wafer portion and slice base portion together or selectively slice off the wafer portion and further cut off the slice base at half way so as to remain the other half base portion as shown in Fig.7. According to this half way slicing process of the slice base(P), it is effective to improve the workability of unloading the wafers(W) re-sliced from the slicing machine without separation work of two sheets wafers(W) because of the incorporation of them at the remained slice base(P). This re-slicing process shown in Fig.6 and Fig.7 should be commonly practiced even in the sequent example to be disclosed hereafter, however, the explanation of such the re-slicing process in Figs.6 and 7 will be omitted in the following another example due to avoid the duplicate explanations. EXAMPLE II. Fig.8 to Fig.11 show the second example of the present invention, which relates to a process and apparatus for mounting a slice base on a semiconductor wafer. In the second example, it is referred to this example in accordance with the same referential number with the first example such as the semiconductor wafer(W), slice base(P) and adhesive(C), since the second example comprises of materially same members with the first example. Firstly, it is referred to the process for mounting a slice base in the second example. In a word, the major difference between the first and second examples is to use or not use a spacing wafer(1) when the slicing base(P) is applied on the peripheral edge of semiconductor wafer(W) by using the adhesive(C). As shown in Fig.8, the second example does not use any spacing wafer(W) at all. It provides two type of rack magazines such as an wafer rack magazine(12) and a slice base rack magazine(11) for loading the semiconductor wafer(W) and the slice base(P) into each rack groove respectively wherein they are aligned correctly and then the adhesive(C) is applied on the upper end of slice base(P), wherein the wafer rack magazine(12) is engaged to the slice base rack magazine(11). This feature is the outline of the process for mounting a slice base on a semiconductor wafer in the second example. In Figs.9 and 10, regarding the adhesion between the bottom of semiconductor wafer(W) and the upper end of slice base(P) with the adhesive(C), it is achieved by the dead load of the wafer(W) itself naturally without any mechanical pressure in response to the engagement between both magazines. As an option, in Figs.9 and 10, it may be possible to load the semiconductor wafer(W) into the wafer rack magazine(12) by making the orientation flat(Wo) portion to face downward so as to contact with the space base(P) through the adhesive(C). According to the process in the second example, it has the following advantages of that the semiconductor wafer(W) is mounted securely on the slice base(P) through the adhesive(C) without any movement, incline or divergence in the alignment, consequently it can prevent the semiconductor wafer(W) with the slice base(P) from any shortage of fixing strength or error in the accuracy of measurement. In addition, since the semiconductor wafer(W) is mounted on the slice base(P), it can prevent the semiconductor wafer(W) from the dirt of adhesive(C) causing by falling in drops if an excessive adhesive(C) is applied on the upper end of the slice base(P). In Fig.11, it shows a thicker slice base(P) having a larger core thickness than the core thickness of semiconductor wafer(W). According to this thicker slice base(P), it can prevent an adhesive(C) from over-flow to outside if the adhesive(C) is excessively applied on the slice base(P) and in contrast it rather improve the fixing strength between the semiconductor wafer(W) and the slice base(P) by the excessive application of the adhesive(C). It is referred to an apparatus for mounting the semiconductor wafer(W) on the upper end of slice base(P) in accordance with the above process of the second example based on Figs.8 to 10. The apparatus of the second example comprises an wafer rack magazine(12) shaped as a box and a slice base rack magazine(11) shaped as a rack gear as shown in Figs.8 to 10. The wafer magazine body(15) of the wafer rack magazine(12) has a plurality of rack grooves(16) in both interior walls opposed each other in the magazine body(15). The rack grooves(16) are formed with a predetermined numbers and interval so as to receive a predetermined numbers of semiconductor wafers(W) capable of taking out and putting into the rack grooves(16) which are also formed to meet with the other rack grooves(l4) of the slice base rack magazine(11). The bottom portion(17) of the wafer magazine body(15) is formed to be fully opened so as to accept the other slice base rack magazine(11). The slice base rack magazine(11) has also a predetermined numbers of rack grooves(14) formed upward from the bottom portion(13) so as to meet with the above rack grooves(16) of the wafer rack magazine(12) to receive a predetermined numbers of slice base(P) capable of taking out and putting into the rack grooves(14). To secure the accuracy of engagement between the both magazines(12)(11), the wafer rack magazine(12) has a plurality of guide pins(18b) projected at adequate positions on the bottom surface of the wafer magazine body(15) to engage with a plurality of guide holes(18a) bored at suitable positions(18) on the upper surface of the slice base rack magazine(11) other than the rack grooves(14). In the practice of the engagement of both magazines(12)(11), the predetermined numbers of semiconductor wafers(W) and the same numbers of slice base(P) are loaded respectively into each magazine(12)(11) and these magazines(12)(11) are engaged together by engaging the guide pins(18b) with the guide holes(18a) after the application of the adhesive(C) on each upper end of slice base(P). According to the engagement of the both magazines(12)(11), the slice base(P) is fixed with the bottom edge of semiconductor wafer(W) so as to push up the semiconductor wafer(W) by the slice base(P) as shown in Fig.10, and then the adhesion of both materials are achieved by the dead load of semiconductor wafer(W) itself. Depending on the properties of adhesive(C), it can accelerate the hardening of adhesive(C) by heating the whole magazines(12)(11) containing the materials(W)(P) into a heating oven and the like. Upon the completion of fixing the both materials(W)(P), it can be taken out from the upper side. Regarding the material of making the both magazines(12)(11), they may be made of an adequate material, which does not receive any adhesive influence from the adhesive(C), preferably such as the tetrafluoride ethylene resin. In addition, it may employ an ordinal wafer magazine as a substitute for the wafer rack magazine(12). EXAMPLE III . Figs.12 to 16 show the third example of the present invention which relates to an improved structure of the slice base(P) commonly used in the first and second examples as aforementioned. In the third example, which is shown in Fig.13, it provides a slice base(P') having an U-shaped slit(21) in section view which is prepared to insert a peripheral edge(20) of semiconductor wafer(W) along the upper portion(22) of the slice base(P') having the U-shaped slit(21). Fig.12 shows a slice base(P') to be mounted on the circular arc(20') shaped peripheral edge(20) of the semiconductor wafer(W), therefore, the upper portion(22) with the U-shaped slit(21) is formed as a circular arc to meet with the circular arc shaped peripheral edge of the semiconductor wafer(W). Fig.14 shows another slice base(P') to meet with the orientation flat(Wo) edge of the semiconductor wafer(W). Regarding the adhesion of both materials such as the semiconductor wafer(W) and the slice base(P'), it is achieved in accordance with the processes for mounting the slice base(P) on the semiconductor wafer(W) disclosed in the first and second examples, that is, a comparatively thicker adhesion(C) is applied at the bottom of U-shaped sLit(21) and then a semiconductor wafer(W) is inserted into the bottom of U-shaped slit(21) wherein they are fixed. Fig.15 shows a modified slice base(P") having L-shaped step portion. In this case, it is advantageous that the workability of making such L-shaped step type slice base(P") is comparatively easier than the case of making the U-shaped slit type slice base(P'). Depending on the slicing method, it is sometime required to fix two sheets of semiconductor wafer(W) along with on the step portion of one piece of slice base(P"), however, it can solve the requirement easily by enlarging the width of the terrace portion of L-shaped step type slice base(P"). According to the third examples such as the U-shaped slit type slice base(P') and the L-shaped step type slice base(P"), since the semiconductor wafer(W) is engaged closely with the interior wall surfaces(21) of the slit type slice base(P') or the one side wall surface(24) of the step type slice base(P") through the adhesive(C), the semiconductor wafer(W) can be fixed with not only the bottom(20) of the slit but also both sides(21)(21) of the interior wall surfaces(21) in Fig.16, or not only the step(20) of the step type slice base(P") but also the one side surface(24) through the adhesive(C), wherein the fixing areas of both type slice bases(P') (P") are enlarged so as to increase their fixing strength. Further, depending on the material properties or viscosities of the adhesive(C), the adhesive(C) forms boss portions(23) pushed out by the pressure of insertion between the upper ends of slice bases(P') (P") and the both sides of the semiconductor wafer(W), wherein the boss portions(23) are effective to further increase the fixing strength between both materials. (Figs.13, 15 and 16) Thus, the semiconductor wafer(W) with the U-shaped slit type slice base(P') and/or the L-shaped step type slice base(P") is further processed to re-slice into two sheets of semiconductor wafer(W') having one side of plane surface without any impurity diffusion layer and the other side of impurity diffusion layer processed in advance by using the re-slicing machine referred to in the first and second examples as shown in Figs.6, 7 and 16. Fig.16 corresponds to Fig.7 in which shows a feature of slicing the slice bases(P')(P") until the half way of slice bases upon the completion of slicing the whole semiconductor wafer(W). Particularly, in one of the semiconductor wafer(W') with the U-shaped slit type slice base(P') after re-sliced until the half way of slice base(P') in Fig.16, the adhesion between the wafer(W') and the half way slit base(P') is still maintained securely along L-shaped interface between the wafer(W') and the slit base(P'). In Fig.16, during the re-slicing process by ID saw(4) of slicing machine, the wafer(W) is going to separate each other by the slicing down movement of the ID saw so as to divide the wafer(W) into two sheets of the wafers(W'). In addition, the core thickness of the slice base(P') is thicker than the core thickness of the wafer(W), therefore, the core portion of the U-shaped slit type slice base(P') can hold securely without any breakdown even if it is slit until the half way of the slice base(P'). In the re-slicing process of the L-shaped step type slice base(P") in Fig.15, comparing the step type slice base(P") with the above slit type slice base(P'), just looking the step type(P") would be disadvantageous in the difference of the shape between U-shape and L-shape when they are re-sliced from their center, however, it can still overcome the disadvantage if a special type chucking instrument is provided for chucking one side of the slice base(P"). (not shown in the drawing) EXAMPLES IV AND V The highlight of examples IV and V is to mold an adhesive(C'), which is a quick-drying type viscous liquid material, into a slice base on the upper end of the wafer(W) held between both spacing wafers(1) by pouring the liquid material into the space provided between the both spacing wafer(1) as a substitute for those solid type slice bases(P)(P')(P") as shown in the example IV of Figs.17 to 20 and the example V of Figs.21 to 30. (EXAMPLE IV) Referring now in detail to the example IV according to Figs.17 to 20. In the practice of example IV, it is followed in accordance with the example I in Figs.3 to 4, that is, it comprises two kind of wafers such as a plurality of semiconductor wafer(W) and a plurality of spacing wafer(1) having a larger diameter than the semiconductor wafer, the spacing wafer(1) is only purposed to space between semiconductor wafers to separate each other. Providing these two kind wafers and aligning them one by one vertically in a concave groove(2') of an wafer bed(2) so as to place two sheets of spacing wafers(1)(1) to both sides of the alignment of these wafers(W)(1) as shown in Fig.3. In addition, pressing plates(3)(3) are provided to press the alignments of those wafers(W)(1) on the wafer bed(2) toward inside from both sides so as to hold the wafers' alignments between the both pressing plates(3)(3). Regarding the composition of the adhesive(C'), it is made of adding a filler such as talc powder, aluminum oxide powder or graphite powder with epoxy resin type adhesive wherein they are regulated to have an adequate viscosity and adhesive property. Thus, this adhesive(C') is poured into a bottom of space provided between both spacing wafers(1)(1), the bottom of space is also the peripheral edge of the semiconductor wafer(W), and the adhesive(C') is formed into a crescent shaped slice base(30) fixed on the peripheral edge of the semiconductor wafer(W) as shown in Figs.17 and 18 to solidify the adhesive(C'), and preferably put them into an oven so as to shorten the solidification time. Figs.19 and 20 show a modified crescent shaped slice base(30) for further improving the fixing strength between the slice base(30) and the wafer(W) by processing additional modification upon the peripheral edge of the semiconductor wafer(W) or the opposed surfaces of spacing wafers(1)(1). In the additional modification upon the semiconductor wafer(W) in Fig.19, it provides a slit(32) on the peripheral edge of the semiconductor wafer(W) so as to increase the interface area of mold type slice base(30) with the semiconductor wafer(W). In the other additional modification upon the opposed surfaces of spacing wafers(1)(1) in Fig.20, the thicknesses of the upper portions of spacing wafers(1)(1) are reduced to provide additional spaces between the reduced surfaces of spacing wafers(1')(1') to receive the mold type slice base(30) so as to cover the upper end of the semiconductor wafer(W) as shown in Fig.20, wherein the fixing strength between the mold type slice base(30) and the semiconductor wafer(W), and even after the semiconductor wafer(W) being re-sliced into two sheets, the fixing strength between the re-sliced mold type slice base(P) and the re-sliced semiconductor wafer(W') can be maintained well due to the sufficient thickness of the re-sliced mold type slice base(30). As an additional advantage, this process can easily widen the range of covering the lower periphery of semiconductor wafer as the last portion of re-slicing process by enlarging the size of molding type slice base, wherein this process is extremely effective for the re-slicing process of thin type semiconductor wafer which is easily chipped off around the lower periphery portion. As to the feature of Figs.19 and 20, as an option, it can load two sheets of semiconductor wafers(W)(W) into the molding type slice base, and can re-slice them in order, depending on the preparation of modified slicing machine having two loaders with vacuum cups opposed each other between the two sheets of semiconductor wafers(W)(W) wherein are capable of chucking one side of them to re-slice firstly and then chucking the other side of them to re-slice later. (not shown in the drawings) According to this example IV of using the mold type slice base(30) , since the spacing wafers(1) having a larger diameter than the semiconductor wafer(W) can assist to align and restrict the semiconductor wafer(W) with the mold type slice base(30) formed by pouring the adhesive(C') into the space formed between the both spacing wafers(1)(1), the plurality of the semiconductor wafers(W) with the slice base(30) can be fixed at accurate position on the wafer bed(2) without any damage of the semiconductor wafers(W) with the slice base(30), the shortage of fixing strength and error in the accuracy of measurement causing by the movement, incline, divergence and the like. In addition, there is no fear that a semiconductor wafer having a large size diameter and a thin thickness is not broken during the pressing process from the both sides because the full surfaces of semiconductor wafers are held by spacing wafers, and also no fear that the adhesive(C') is fallen out in drops along the surfaces of semiconductor wafers(W) because they are contacted closely by the spacing wafer in both sides by the pressure. In addition, since the adhesive(C') can be filled easily to cover the peripheral edge of semiconductor wafer(W) over the wide area of interface by utilizing the flowability of the adhesive(C'), no loss of the crude material of slice base(P)(P')(P") is produced during the cutting process of the crude material into each piece of the slice base, whereby it can save the material cost in the example IV. (EXAMPLE V) Figs.21 to 30 show the example V of a process and apparatus for forming another mold type slice base(40). It is referred now to the apparatus for forming the mold type slice base(40). This apparatus comprises an wafer magazine(A 1 ) to hold in upright a plurality of semiconductor wafer(W) aligned and a mold bed(A 2 ) having a plurality of molding grooves(45) to form slice bases(40) from the adhesive(C'). This mold bed(A 2 ) is purposed to receive the bottom of wafer magazine(A 1 ). The wafer magazine(A 1 ) is made of a resin, which has a specified property of not receiving adhesive influence from the adhesive(C'), such as a resin selected from the group consisting of the tetrafluoride ethylene resin, the wafer magazine(A 1 ) is formed as a box body(41) having a plurality of guide slits(42) provided opposed in the both side interior walls of the body wall(41a) to receive the plurality of semiconductor wafers (W) by inserting the wafers(W) vertically along the guide slits(42). The body walls(41a) of the box body(41) are made to dogleg inwardly each other with the same guide slits(42), the body walls(41a) extends the legs portions(41C)(41C) which form a bottom opening((41b) along the longitudinal direction of the box body(41) to engage with the mold bed(A 2 ) so as to cover the box body(41) of the wafer magazine(A 1 ) on the mold bed(A 2 ). The mold bed(A 2 ) provides a mold portion(44) with molding grooves(45) on the base plate(43) of the mold bed(A 2 ) for receiving the bottom edge of the semiconductor wafer(W) on the upper surface of the mold bed(A 2 ), therefore, the molding grooves(45) of the mold bed(A 2 ) are made in the same shape and pitch with the other guide slits(42) of the wafer magazine(A 1 ) so as to receive the semiconductor wafer(W) when the wafer magazine(A 1 ) and the mold bed(A 2 ) are engaged together. The base plate(43) of the mold bed(A 2 ) has grooves for engagement(50) in the both sides of the base plate(43) to engage with the lower ends of the legs portions(41C) of the wafer magazine(A 1 ). Regarding the formation of the mold portion(44) with the molding grooves(45), the mold portion(44) is formed as concave circular arc so as to almost meet with or in excess of the circle of the semiconductor wafer(W) and the molding grooves(45) are formed as a circular arc along the concave circular arc of the mold portion(44) to receive the adhesive for forming the mold type slice bases(40) to fix with the bottom edge of the semiconductor wafer(W). In Fig.26 and Fig.29, the shape of the molding grooves(45) may be formed as enlarged trapezoidal shape capable of covering the lower end of the semiconductor wafer(W) by the adhesive(C'). In addition, the both ends of the molding grooves(45) provide V-shaped guide slits(46) for supporting the peripheral edge of the semiconductor wafer(W) from the lower portion. As shown in Figs.27 and 28, the V-shaped guide slits(46) are formed so as to deepen the V-shape slit inwardly from the outside, and formed along the circular arc of the molding grooves(45) of the mold portion(44) on plate members(48) fixed by screws with the both sides of the mold portion(44), and the center line of the V-shaped guide slits(46) is made to meet with the center line of the molding grooves(45), therefore, each semiconductor wafer(W) is positioned at the center lines of them by engaging the wafer magazine(A 1 ) with the mold bed(A 2 ). The each molding grooves(45) form the mold type slice bases(40) along the peripheral edge of the semiconductor wafer(W) by pouring and to solidify the adhesive(C') into the molding grooves(45), therefore, the mold type slice bases(40) can be formed with high accuracy along the peripheral portion of the semiconductor wafer(W) by supporting the peripheral edge portion of the semiconductor wafer(W) at the center line of the V-shaped guide slits(46). In addition, the plate members(48) to be fixed with the both sides of the mold portion are adjustable up and downwards by loosening the screws(47) wherein it is possible to adjust the inserting depth of the lower peripheral edge of semiconductor wafer(W) into the molding grooves(45) by adjusting the plate members(48) up and downward, and then possible to vary the inserting depth of the semiconductor wafer(W) to the mold type slice base(40). Fig.23 shows another example of the mold portion of the mold bed(A 2 ). In Fig. 23, molding grooves(45') are formed deeper downwardly with a smaller size circular arc than the wafer' s circular arc, wherein the mold type slice base(40') is formed as a slice base having a deeper depth at the central portion. The both sides of the molding grooves(45') provide V-shaped guide slits(46') as shown in Figs. 24 and 25. By forming the slice base(40') with the wide depth at the central portion to fix with the semiconductor wafer(W), the slice base(40') can still hold two sheets of re-sliced semiconductor wafer(W')(W') on the slice base(40') upon the completion of re-slicing process of the wafer(W), therefore, it is advantageous that it can unload the re-sliced wafers(W')(W') at the same time upon the completion of the re-slicing process. This type mold bed(A' 2 ) is, therefore, suitable for such the unloading method without separation of two sheets. In the above type mold bed(A' 2 ) provides an insert core(49) separated from the base plate(43) so as to close the other opening portion located under the molding grooves(45'). This insert core(49) is purposed to take out from the base plate(43) upon the completion of molding process of the slice base(40'). After the taking out the insert core(49), the semiconductor wafer(W) with the mold type slice base(40') is unloaded by pushing up from the bottom portion through the opening of the base plate(43). By pushing up the slice base(40'), the semiconductor wafer(W) is unloaded from the wafer magazine(A 2 ) without giving any damage to the wafer's surfaces(W). In addition, the both sides of the molding grooves(45') provides V-shaped guide slits(46') formed as extending the circular arc of the molding grooves(45') as shown in Figs.24 and 25. It is now referred to the method for forming the mold type slice base(40') in the example V by using the aforementioned apparatus(A) for forming the slice base(40'). In the method, the plurality of the semiconductor wafers(W) are loaded into the wafer magazine(A 1 ) in the same pitch each other along the guide slits(42) as the orientation flat(Wo) of the semiconductor wafer(W) being positioned in the upper state. In this state, the lower peripheral edges of the semiconductor wafers(W) are inserted along the guide slits(42) in the both sides of the wafer magazine(A 1 ) and then the semiconductor wafers(W) are held vertically without any backlash in the wafer magazine(A 1 ) by holding the both side peripheral edges of the semiconductor wafer(W) in the both side interior walls(41a). A hardening type resin as a crude material to form the slice base(40) is filled into each molding grooves(45') of the mold bed(A 2 ) to be inserted into the bottom opening(41b) of the wafer magazine(A 1 ). The hardening type resin is selected from the group consisting of epoxy resin mixture as a thermosetting resin mixed with talc powder, aluminum oxide powder or graphite powder as a filler for providing a certain viscosity of not flow out when filled in the molding grooves(45'), wherein the hardening type resin is filled to the upper limit of each molding grooves(45') while drawing attention to do not roll in any air bubble into the molding resin by using an instrument of filling the resin. (Fig.26) The wafer magazine(A 1 ) and the molding bed(A 2 ) are engaged so as to cover the opening portion(41b) of the wafer magazine(A 1 ) on the molding portion(44) of the molding bed(A 2 ) to insert the lower ends of the legs portions(41C) of the wafer magazine(A 1 ) into the receiving grooves(50), wherein the lower peripheral edges of the semiconductor wafer(W) are inserted into the molding grooves(45') of the molding bed(A 2 ) by the dead load of the wafer itself or suitable pressurization from the upper side. (Fig.21) In the above case, the lower peripheral edge of the semiconductor wafer(W) is inserted into the V-shaped guide slits(46) of the both side of the molding grooves(45'), and supported from the lower portion, wherein the lower peripheral edge of the semiconductor wafer(W) is accurately positioned at the central line of the molding grooves(45') and then covered by the adhesive(C') filled into the molding grooves(45') with a predetermined depth(b). When the lower peripheral edge of the semiconductor wafer(W) is inserted into the adhesive resin filled in the molding grooves(45'), the resin is risen at the both sides of the wafer(W) and the risen portions are formed with the acute angle() degree causing by the sufficient viscosity and the surface tension as shown in Fig.29, and then the risen portions are kept as they are. The inserting depth of the lower peripheral edge of the semiconductor wafer(W) into the molding grooves(45') can be adjustable by moving the plate member(48) up and down. The molding adhesive filled into the molding grooves(45') together with the lower peripheral edge of the semiconductor wafer(W) is thermally solidified in an environment having a predetermined temperature. After the solidification, the wafer(W) with the solidified slice base(40) is unloaded from the wafer magazine(A 1 ). In addition, the exfoliation of the slice base(40) from the molding grooves(45') can be achieved easily by using a high exfoliation type resin, however, it may be further useful to employ an exfoliating agent to coat over the interior surfaces of the molding grooves(45') in advance. The slice base(40) made of ther resin and formed around the peripheral edges of the semiconductor wafer(W) is formed so as to cover the both surfaces of the peripheral edges of the semiconductor wafer(W) as shown in Fig.29. The semiconductor wafer(W) unloaded from the molding bed(A 2 ) is further transferred to the cutting process for dividing the unloaded wafer(W) into two sheets, and the wafer magazine(A 1 ) and the molding bed(A 2 ) are repeatedly used. According to the aforementioned process for forming the slice base, it can mold the slice base(40) to incorporate with the lower peripheral edge of the semiconductor wafer(W) without making by hand in remaining as the wafers(W) are loaded within the magazine(A 1 ). Therefore, it can form the slice base(40) with high accuracy by saving the labor by hand as well as can reduce the flow out of the adhesive which has been occurred conventionally and further reduce the damage during the handling of the wafer(W), in addition it can save the material cost since such a ready made type slice base is comparatively expensive but this invention does not employ such the expensive type slice base. In the re-slicing process, the above semiconductor wafer(W) with the slice base(40) is re-sliced into two sheets from the center portion of the core thickness of the wafer(W) by using ID saw and the like, however, it can prevent the wafer(W) effectively from the damage for the end portion of the wafer(W) causing by the cutting pressure by the squeeze of the saw into the core since the lower peripheral edge of the semiconductor wafer(W) is reinforced so as to cover the lower end by the slice base(40) as shown in Fig.29. Upon the completion of the re-slicing process, a mold-releasing agent is impregnated into the joint portion between the lower end of the wafer(W) and the mold type slice base(40) for removing the slice base(40) which is already unnecessary from the lower end of the wafers(W) which has been re-sliced into two sheets. In the impregnation of the mold-releasing agent into the joint portion, the mold-releasing agent is easily impregnated into the joint portion since the joint portions are formed with the acute angle(  ) degree causing by the sufficient viscosity and the surface tension as shown in Fig.29, in addition it is advantageous that it can remove the slice base(40) easily from the lower end of the wafer(W) since the mold type slice base(40) is pressed by external force under favorable conditions as a force to make the wafer to be released from the slice base(40). In the re-slicing process of the wafer(W), the wafer(W) is re-sliced by the ID saw while the wafer(W) is held by a vacuum chuck equipped with the slicing machine after loaded on the vacuum chuck by a loader(i.e. an wafer loading manipulator having a vacuum cup on the end of manipulator). In the loading or unloading work of the wafer(W), it appears disadvantageous that the vacuum chuck or cup would be unable to chuck the whole surface of the wafer(W) because of the structure of the mold type slice base(40) formed with one step projected outwardly from the wafer surface, however, it is proven that there is no problem to chuck the wafer portion only other than the projected portion of the slice base(40). According to the above process for forming the mold type slice base, as shown in Fig.30, it can form a slice base(40") for covering the lower peripheral edges of two sheets or more than two sheets of the semiconductor wafer(W). In addition, there are two ways such as to re-slice the wafer(W) together with the slice base(40) completely into two sheets, and/or to re-slice the wafer(W) with the half of slice base(40) to remain the last part of the slice base(40) to hold the re-sliced two sheets of the slice base(40) wherein it can unload the two sheets of the wafer(W')(W'). In the former, the slice base is formed with the same width such as the slice base(40) formed in the molding grooves(45) of the molding bed(A 2 ), and in the latter, it can correspond by enlarging the width of the central portion to be sliced such as the slice base(40') formed in the molding grooves(45') of the molding bed(A' 2 ). In case of enlarging the reinforcing range of the slice base(40), or in case of forming the slice base(40) along the orientation flat(Wo) of the semiconductor wafer(W), it can correspond by changing the form of the molding grooves of the molding bed. Regarding the wafer magazine(A 1 ), a general type article on the market is adaptable, however, it suggest to use a specially designed wafer magazine in case of forming a slice base with a wide range such as to form two sheets of the wafer(W) at the same time, or to form a slice base for specially thickened wafer, or specially thickened peripheral edge portion. According to the apparatus referred to the example V, a plurality of semiconductor wafers are aligned to hold vertically in an wafer magazine, the lower peripheral edges of these wafer are inserted into molding grooves having a concave circular arc shape of a molding bed respectively, it is made that the lower peripheral edges of the wafer are supported on V-shape guide slits provided on the both ends of the molding grooves so as to position at the central line of the molding grooves, it can form slicing bases made of hardening type resin to fix with the plurality of semiconductor wafers at the same time so as to cover the lower peripheral edges of the wafer with an equal thickness of the core of the slice base in the both sides. In addition, it can vary the depth of molding the lower ends of the semiconductor wafer into the mold type slice base by adjusting the molding depth the lower end of the wafer into the molding grooves by composing the supporting member of the molding grooves having the concave circular arc shape in the both sides with the other member.

Claims: A process for mounting slice bases (P) on wafers (W) of semiconductor, comprising the steps of: providing a plurality of wafers (W) of semiconductor having impurity diffusion layers (Wb) processed in advance on the respective both sides of said wafers (W) with plane core (Wa) portion without impurity diffusion layer therein; providing a plurality of spacing wafers (1) having larger diameter than said wafer (W) of semiconductor; providing a plurality of slice bases (P); aligning said wafers (W) of semiconductor and said spacing wafers (1) vertically one by one in a wafer magazine (2); pressing from both sides of said wafers (W) of semiconductor and said spacing wafers (1) aligned in axial direction so as to contact each other closely; and applying an adhesive (C) on one edge of said slice bases or on the peripheral edge of said semiconductor wafers (W) in advance, and mounting said slice bases (P) with or without adhesive applied on the peripheral edge of said wafers (W) of semiconductor by inserting said slice bases (P) into between both spacing wafers (1). A process for mounting slice bases (P) on wafers (W) of semiconductor, comprising the steps of: providing a plurality of wafers (W) of semiconductor having impurity diffusion layers (Wb) processed in advance on the respective both sides of said wafers (W) with plane core portion (Wa) without impurity diffusion layer therein, and loading the plurality of wafers (W) of semiconductor into a wafer rack magazine (12) with the wafers (W) of semiconductor equally pitched; providing a plurality of slice bases (P), loading the plurality of said slice bases (P) into another rack magazine (13) for slice bases (P) and applying an adhesive (C) on the upper edges of said slice bases (P) in advance; and mounting the lower peripheral edge of said wafers (W) of semiconductor on the upper edges of said slice bases (P) by placing said rack magazine (12) loaded with said wafers (W) of semiconductor on said other rack magazine (13) loaded with said slice bases (P) so that said wafers (W) of semiconductor rest on said slice bases (P) by gravity. The process according to claim 2, wherein a slice base (P') is formed as a U-shaped slit type slice base having thicker core thickness than the core thickness of semiconductor wafer (W), said U-shaped slit type slice base (P') receives the lower peripheral edge of said semiconductor wafer (W) so as to insert said lower edge of semiconductor wafer (W) into said U-shaped slit portion (20') of said slice base (P') for mounting said semiconductor wafer (W) on said slice base (P'). The process according to claim 2 wherein a slice base (P) is formed as an L-shaped step type slice base (P") having thicker core thickness than the core thickness of semiconductor wafer (W), said L-shaped step type slice base (P") is used to mount the lower peripheral edge of said semiconductor wafer (W) on the step portion of said L-shaped step type slice base (P") so as to join the lower part of said semiconductor wafer (W) along the L-shaped step portion of said slice base (P"). An apparatus for mounting slice bases (P) on semiconductor wafers (W) comprising: a wafer rack magazine (12) having a plurality of equally pitched guide racks (16) formed in opposed interior walls of said magazine (12) for loading or unloading vertically a plurality of semiconductor wafers (W) into or from said guide racks (16) in said magazine (12), said plurality of semiconductor wafers (W) having impurity diffusion layers (Wb) processed in advance on the respective both sides of said wafers with plane core portion (Wa) without impurity diffusion layer therein; a slice base rack magazine (13) having a plurality of guide grooves (14) with the same pitch formed on the upper surface of said slice base rack magazine (13) for loading or unloading vertically a plurality of said slice bases (P) into said guide grooves (14); and a plurality of guide pins (18b) projected on the bottom surface of said wafer rack magazine (12) so as to engage with a plurality of guide holes (18a) bored on the base plate of said slice base rack magazine (13); a rectangular opening (17) provided in the bottom of said wafer rack magazine (12) so as to expose the lower peripheral edges of said semiconductor wafers (W) loaded in the magazine (12) to admit the upper edges of said slice bases (P) loaded on the guide grooves (14) of said slice base rack magazine (13) to join with the lower peripheral edges of said semiconductor wafers (W) respectively for mounting the slice bases (P) with the semiconductor wafers (W) when the wafer rack magazine (12) is put on the slice base rack magazine (13) so as to engage each other through the guide pins (18b) and guide holes (18a). The apparatus according to claim 5, wherein said slice base (P) has a U-shaped slit (P') or L-shaped step (P") for mounting vertically said semiconductor wafer (W) including the lower edge surface of said semiconductor wafer (W). A process for molding slice bases (P) and simultaneously connecting them to semiconductor wafers (W) comprising the steps of: providing a plurality of semiconductor wafers (W) having impurity diffusion layers (Wb) processed in advance on the respective both sides of said wafers with plane core portion (Wa) without impurity diffusion layer therein; providing a plurality of spacing wafers (1) having larger diameter than said wafer (W) of semiconductor; providing a viscous adhesive (C') selected from a group consisting of thermosetting resin; aligning alternately said semiconductor wafers (W) and said spacing wafers (1) vertically one by one in a wafer magazine (2) so as to form a valley between adjacent spacing wafers (1) having the larger diameter than the semiconductor wafer (W) constituting the bottom portion of said valley; pressing inwardly from both sides of said semiconductor wafers (W) and said spacing wafers (1) aligned vertically one by one in axial direction so as to contact each other closely; and pouring an amount of said adhesive (C') into said valley constituted by adjacent spacing wafers (1) so as to mold a slice base (30) on and connect it to the upper peripheral edge of said semiconductor wafer (W) through a thermosetting process. The process according to claim 7, wherein a mold type slice base (30) is formed as a crescent-shape on said upper peripheral edge of said semiconductor wafer (W). A process for molding slice bases (40) and simultaneously connecting them to the lower peripheral edges of semiconductor wafers (W) comprising the steps of: providing a plurality of semiconductor wafers (W) having impurity diffusion layers (Wb) processed in advance on the respective both sides of said wafers (W) with plane core portion (Wa) without impurity diffusion layer therein loaded at equal pitch and in alignment in a wafer rack magazine (A 1 ) for said semiconductor wafers (W), the lower peripheral edge portions of said semiconductor wafers (W) are exposed through a rectangular opening (41b) provided at the bottom of said wafer rack magazine (A 1 ); providing a viscous adhesive (C') selected from a group consisting of thermosetting resin; pouring an amount of said adhesive (C') respectively into molding grooves (45) provided on the upper surface of a slice base molding bed (44), placing said wafer rack magazine (A 1 ) loaded with said semiconductor wafers (W) therein on said slice base molding bed (44) so as to insert said lower peripheral edges of said semiconductor wafers (W) exposed in said rectangular opening (41b) to a predetermined depth in the adhesive (C') for moulding and simultaneously connecting the slice bases (40) on the semiconductor wafers (W); and unloading said semiconductor wafers (W) incorporated with said molded slice bases (40) at the same time from said wafer rack magazine (A 1 ) engaged with said slice base molding bed (44), upon the completion of adequate thermosetting process of said adhesive material (C') within said molding grooves (45) of said slice base molding bed (44). The process according to claim 7 or claim 9, wherein said thermosetting resin (C') is selected from a group consisting of epoxy type resin given with a desirous viscosity by mixing talc into said thermosetting resin. The process according to claim 9, wherein said mold type slice base (40) is molded so as to adhere to the lower peripheral edge of said semiconductor wafer (W), and so as to cover both sides of the lower portion of said semiconductor wafer (W). The process according to claim 11, wherein said mold type slice base (40) is molded as almost a crescent shape on the lower peripheral edge of said semiconductor wafer (W). The process according to claim 11, wherein said mold type slice base (40) is molded around the lower peripheral edges of two of said semiconductor wafers (W) overlapped. An apparatus (A) for molding slice bases (40) and simultaneously connecting them to the peripheral edges of semiconductor wafers (W), comprising: a wafer rack magazine (A 1 ) having equally pitched guide racks (42) in the opposed interior walls of said magazine (A 1 ) for loading or unloading vertically a plurality of semiconductor wafers (W) into or from said guide racks (42) in said magazine (A 1 ); a rectangular opening (41b) provided at the bottom portion of said wafer rack magazine (A 1 ) so as to expose the lower peripheral edges of said semiconductor wafers (W) when loaded vertically into the magazine (A 1 ); a slice base molding bed (44) having a plurality of molding grooves (45) with the same pitch formed as a concave crescent shape on the upper surface of said slice base molding bed (44) for pouring an adhesive (C') into each molding groove (45) to mold slice bases (40) and simultaneously to connect them around the lower peripheral edge portions of said semiconductor wafers (W), and V-shaped guide slits (46) provided integrally with both ends of said crescent shaped molding grooves (45) formed on the upper surface of said molding bed (44) for receiving the lower peripheral edges of semiconductor wafers (W) when they have been loaded vertically in order to accurately position the lower edge of semiconductor wafer (W) along the center line of said molding grooves (45) filled by the adhesive material (C'). The apparatus according to claim 14, wherein said V-shaped guide slit portions (46) are provided separately to attach with both ends of said crescent shaped molding grooves (45) on the molding bed (44), and are adjustable to adjust the level of V-shaped slits so as to adjust the depth of inserting the lower edge of said semiconductor wafer (W) into the molded slice base (40) within the molding groove (45). A slice base (P") mounted on the peripheral edge of a semiconductor wafer (W) having impurity diffusion layers (Wb) processed in advance on the respective both sides of said wafers with plane core portion (Wa) without impurity diffusion layer therein comprising: said slice base (P") mounted on the lower peripheral edge of said semiconductor wafer (W) so as to be rigidly engaged with the core of said slice base (P"), characterised in that said slice base (P") has a U-shaped slit (20') or an L-shaped step (20) in sectional view so as to join the lower peripheral edge of semiconductor wafer (W) with said U-shaped slit (20') or said L-shaped step (20) of said slice base (P").

Inventors: HIGUCHI HIDEO, IGARASHI ZENICHI, KASAHARA AKIO, KIMURA HIROKASU, SATO TSUTOMU, YOSHIMURA YASUSHI, HIGUCHI,HIDEO, IGARASHI,ZENICHI, KASAHARA,AKIO, KIMURA,HIROKASU, SATO,TSUTOMU, YOSHIMURA,YASUSHI
Applicants: NAOETSU DENSHI KOGYO KK, NAOETSU ELECTRONICS COMPANY
Application year: 1990
Main classification: H01L21
IPC codes: H01L21, B28D5, B28D1