Semiconductor device manufacturing method and hot plate

Abstract

To improve the adhesion of a protective film to a semiconductor wafer and improve throughput.SOLUTION: A manufacturing method for a semiconductor device (1) includes: a rib forming step of forming, at an outer peripheral edge of a semiconductor wafer (1), a rib (11) with a ring shape that is thicker than in the center by grinding the center of a back surface of the semiconductor wafer; a back surface film attaching step of attaching a first protective film (14) on a back surface of the semiconductor wafer; an outer peripheral film attaching step of attaching a second protective film (15) so as to cover an outer peripheral edge of the first protective film and an outer periphery of the rib; a heating step of directly heating the first protective film and the second protective film in a hot plate (2) by disposing the back surface of the semiconductor wafer to face a heating surface of the hot plate; and a plating step of plating a front surface of the semiconductor wafer.SELECTED DRAWING: Figure 11

Description

[Technical field]

[0001] The present invention relates to a method for manufacturing a semiconductor device and a hot plate. [Background technology]

[0002] 2. Description of the Related Art Semiconductor devices have a substrate on which semiconductor elements such as IGBTs (Insulated Gate Bipolar Transistors), power MOSFETs (Metal Oxide Semiconductor Field Effect Transistors), and FWDs (Free Wheeling Diodes) are provided, and are used in inverter devices and the like.

[0003] In this type of manufacturing method for a semiconductor device, a plating layer is formed by plating one main surface (front surface) of a semiconductor wafer (see, for example, Patent Document 1). In Patent Document 1, before the plating process, a protective film is formed on the portion where the plating layer is not to be formed. Specifically, in Patent Document 1, a first film is attached to the other main surface (rear surface) of the semiconductor wafer, and a second film is attached to the outer periphery of the semiconductor wafer.

[0004] In the above-mentioned process of attaching the film, air bubbles may get trapped between the semiconductor wafer and the film. In the subsequent plating process, the semiconductor wafer is exposed to a relatively high temperature environment. Therefore, if the air bubbles are expanded by the temperature, the air bubbles become a path for the plating solution to penetrate. As a result, a plating layer is formed in an unnecessary portion, and it is assumed that the semiconductor wafer has an undesirable appearance.

[0005] Therefore, it has been proposed in the past to heat the film after it has been attached and before it is plated in order to improve the adhesion between the film and the semiconductor wafer (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2016-152317 A [Patent Document 2] JP 2011-222898 A Summary of the Invention [Problem to be solved by the invention]

[0007] When heating semiconductor wafers with a film attached thereto, a plurality of semiconductor wafers are stored in a box-shaped cassette and the cassette is then placed in a batch-type oven, which makes it possible to heat a plurality of semiconductor wafers at once.

[0008] However, in a batch oven, the internal space is large, so the temperature inside the oven is likely to be non-uniform. Also, it takes time for the temperature inside the oven to stabilize, which may affect the throughput of the manufacturing equipment. In addition, when the diameter of semiconductor wafers becomes large, problems may occur in which it becomes difficult to automatically transport the cassette.

[0009] The present invention has been made in consideration of these points, and one of its objects is to provide a semiconductor device manufacturing method and a hot plate that can improve the adhesion of a protective film to a semiconductor wafer and improve throughput. [Means for solving the problem]

[0010] A manufacturing method for a semiconductor device according to one embodiment of the present invention includes a rib forming process of grinding the center of the back surface of a semiconductor wafer to form a ring-shaped rib that is thicker at the outer edge of the semiconductor wafer than at the center, a back surface film attaching process of attaching a first protective film to the back surface of the semiconductor wafer, an outer edge film attaching process of attaching a second protective film so as to cover the outer edge of the first protective film and the outer periphery of the rib, a heating process of placing the back surface of the semiconductor wafer opposite the heating surface of a hot plate and directly heating the first protective film and the second protective film with the hot plate, and a plating process of applying a plating process to the surface of the semiconductor wafer.

[0011] Moreover, a hot plate according to one embodiment of the present invention is a hot plate for heating a first protective film and a second protective film attached to a semiconductor wafer, wherein the center of the back surface of the semiconductor wafer is ground to form a ring-shaped rib that is thicker at the outer edge of the semiconductor wafer than at the center, the first protective film is attached to the back surface of the semiconductor wafer, the second protective film is attached so as to cover the outer edge of the first protective film and the outer periphery of the rib, the back surface of the semiconductor wafer is arranged opposite the hot plate, and the hot plate has a heating surface that directly heats the first protective film and the second protective film. Effect of the Invention

[0012] According to the present invention, it is possible to improve the adhesion of the protective film to the semiconductor wafer and also to improve the throughput. [Brief description of the drawings]

[0013] [Figure 1] 1 is a cross-sectional view of a semiconductor wafer according to an embodiment of the present invention. [Diagram 2] 2 is a partially enlarged view of the semiconductor wafer shown in FIG. [Diagram 3] FIG. 1 is a cross-sectional view of a semiconductor manufacturing apparatus (oven) according to a comparative example. [Figure 4] 1 is a plan view of a semiconductor manufacturing apparatus according to an embodiment of the present invention, viewed from above; [Diagram 5] FIG. 5 is a cross-sectional view of the semiconductor manufacturing apparatus shown in FIG. [Figure 6] 2 is a flowchart showing an example of a method for manufacturing a semiconductor device according to an embodiment of the present invention. [Figure 7] 5A to 5C are schematic diagrams showing an example of a process of a manufacturing method of a semiconductor device according to an embodiment of the present invention. [Figure 8] 5A to 5C are schematic diagrams showing an example of a process of a manufacturing method of a semiconductor device according to an embodiment of the present invention. [Figure 9] 5A to 5C are schematic diagrams showing an example of a process of a manufacturing method of a semiconductor device according to an embodiment of the present invention. [Figure 10] 5A to 5C are schematic diagrams showing an example of a process of a manufacturing method of a semiconductor device according to an embodiment of the present invention. [Figure 11] 5A to 5C are schematic diagrams showing an example of a process of a manufacturing method of a semiconductor device according to an embodiment of the present invention. [Figure 12] 5A to 5C are schematic diagrams showing an example of a process of a manufacturing method of a semiconductor device according to an embodiment of the present invention. [Figure 13] 1 is a graph showing the change in temperature over time in a protective film heating process. [Figure 14] FIG. 13 is a schematic diagram of a hot plate according to a modified example. [Figure 15] FIG. 13 is a schematic diagram of a hot plate according to another modified example. [Figure 16] FIG. 13 is a schematic diagram of a hot plate according to another modified example. [Figure 17] FIG. 13 is a plan view of a hot plate according to another modified example. [Figure 18] FIG. 18 is a cross-sectional view taken along line AA in FIG. 17. [Figure 19] FIG. 13 is a plan view of a hot plate according to another modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] A semiconductor manufacturing apparatus and a method for manufacturing a semiconductor device to which the present invention can be applied will be described below. FIG. 1 is a cross-sectional view of a semiconductor wafer according to the present embodiment. FIG. 2 is a partially enlarged view of the semiconductor wafer shown in FIG. 1. FIG. 3 is a cross-sectional view of a semiconductor manufacturing apparatus (oven) according to a comparative example. FIG. 4 is a plan view of the semiconductor manufacturing apparatus according to the present embodiment as viewed from above. FIG. 5 is a cross-sectional view of the semiconductor manufacturing apparatus shown in FIG. 4. Note that the semiconductor manufacturing apparatus and the method for manufacturing a semiconductor device described below are merely examples, and are not limited to these and can be modified as appropriate.

[0015] In the following figures, the left-right direction of the semiconductor manufacturing equipment is defined as the X direction, the front-back direction of the semiconductor manufacturing equipment as the Y direction, and the height direction of the semiconductor manufacturing equipment (thickness direction of the semiconductor wafer) as the Z direction. The illustrated X, Y, and Z axes are mutually perpendicular and form a right-handed system. In some cases, the Z direction may be called the up-down direction. These directions (front-back, left-right, up-down directions) are terms used for convenience of explanation, and the corresponding relationship with each of the X, Y, and Z directions may change depending on the posture of the semiconductor device (semiconductor wafer). In this specification, plan view means a view from above the semiconductor manufacturing equipment.

[0016] The semiconductor manufacturing apparatus 100 according to the present embodiment (see FIGS. 4 and 5) forms a plurality of devices (semiconductor device) on a semiconductor wafer 1 and divides the semiconductor wafer 1 into individual chips. The semiconductor device according to the present embodiment is applied to a power conversion device such as a power control unit, and is a power semiconductor module that constitutes an inverter circuit. The semiconductor manufacturing apparatus 100 according to the present embodiment is an apparatus for realizing one step in a method for manufacturing a semiconductor device. For this reason, details of each step that constitutes the method for manufacturing a semiconductor device will be omitted as appropriate, and a step specialized for this invention (a heating step to be described later) will be mainly described. The configuration of the semiconductor manufacturing apparatus 100 is similar, and a description of the apparatus configuration that is not directly related to this invention will be omitted as appropriate.

[0017] First, a semiconductor wafer 1 to be processed will be described. As shown in Figs. 1 and 2, the semiconductor wafer 1 is formed in a disk shape of a predetermined thickness by a semiconductor substrate such as silicon (Si), silicon carbide (SiC), gallium nitride (GaN), and diamond. A predetermined process is performed on the surface of the semiconductor wafer 1, and devices (not shown) are formed in each area partitioned by lattice-shaped division lines. The devices are mainly formed in the central area of ​​the semiconductor wafer 1. For this reason, a ring-shaped excess area (not shown) where no devices are formed is formed in the outer periphery of the semiconductor wafer 1. Also, a notch (not shown) indicating a crystal orientation is formed in a predetermined location on the outer edge of the semiconductor wafer 1.

[0018] In the semiconductor wafer 1 according to this embodiment, a circular recess 10 is formed by grinding, and as a result, the outer periphery of the back surface side of the semiconductor wafer 1 is formed with a ring-shaped rib 11 that is thicker than the center, that is, a so-called rib shape. The recess 10 is formed in the center region (not shown) of the semiconductor wafer 1 described above. The rib 11 is formed in the surplus region (not shown) of the semiconductor wafer 1 described above.

[0019] More specifically, as shown in Fig. 2, chamfered portions 12 are formed on the upper and lower surfaces of the outer peripheral edge of the semiconductor wafer 1. Furthermore, the inner side of the recess 10, i.e., the inner side of the rib 11, forms an inclined surface 13 that is inclined radially outward as it extends downward. With a ribbed wafer, the strength is maintained by the ring-shaped rib 11 on the outer peripheral edge, and warping of the wafer itself and defects during transportation (such as cracks and chips) can be prevented. The width of the ring-shaped rib 11 can be adjusted to maintain strength, and may be, for example, about 2 mm to 4 mm.

[0020] In addition, a protective film 14 (first protective film) for protecting the back surface is attached to the back surface of the semiconductor wafer 1. The protective film 14 is formed in a circular shape so as to cover the entire back surface of the semiconductor wafer 1. The protective film 14 is attached from the bottom surface of the recess 10 along the inclined surface 13 and the lower surface of the rib 11. In other words, the outer periphery of the protective film 14 is bent so as to ride up the step formed by the recess 10.

[0021] Further, a protective film 15 (second protective film) for protecting the outer peripheral edge is attached to the outer peripheral edge of the semiconductor wafer 1. More specifically, the protective film 15 is attached so as to cover the outer peripheral edge of the protective film 14 and the entire outer periphery of the rib 11 including the upper and lower chamfered portions 12.

[0022] The protective film 14 is formed of a material such as polyester. The thickness of the protective film 14 is preferably 30 μm to 100 μm. More preferably, the thickness of the protective film 14 is 50 μm. The protective film 14 has an adhesive layer (not shown) formed on the surface that contacts the back surface of the semiconductor wafer 1. This description is an example, and the numerical values ​​are not limited.

[0023] The protective film 15 is formed of a material such as polyolefin. The thickness of the protective film 15 is preferably 80 μm to 180 μm. More preferably, the thickness of the protective film 15 is 130 μm. The protective film 15 is preferably thicker than the protective film 14. The protective film 15 has an adhesive layer (not shown) formed on the surface that contacts the outer periphery of the semiconductor wafer 1. This is an example, and the numerical values ​​are not limited.

[0024] In the field of semiconductors in recent years, as semiconductor wafers become larger and thinner, the semiconductor wafers themselves become more susceptible to warping. For this reason, it has been proposed to form a ring-shaped rib on the outer periphery of the semiconductor wafer while leaving the thickness of the outer periphery of the wafer as described above, thereby increasing the rigidity of the wafer as a whole and suppressing warping.

[0025] In the manufacturing method of a semiconductor device, one of the main surfaces (front surface) of the semiconductor wafer is plated in one step of forming devices on the front surface. In this case, in order to prevent plating from being performed on areas unrelated to the device region, a protective film is attached in advance to a predetermined area of ​​the semiconductor wafer as described above.

[0026] In the process of attaching the protective film, air bubbles may get trapped between the semiconductor wafer and the protective film. In the subsequent plating process, the semiconductor wafer and the protective film are exposed to a relatively high temperature environment. This may cause the air bubbles to expand due to the temperature, and the plating solution may penetrate into the air bubbles. As a result, a plating layer may be formed in unnecessary areas, resulting in the manufacture of products that are undesirable in appearance.

[0027] Therefore, in the past, after the protective film is attached, the protective film is heated before plating is performed. This softens the adhesive layer of the protective film, and reduces gaps such as air bubbles between the protective film and the semiconductor wafer. As a result, the adhesion between the protective film and the semiconductor wafer is improved.

[0028] Here, a conventional heating process will be described with reference to a comparative example in Fig. 3. As shown in Fig. 3, a plurality of semiconductor wafers 1 with protective films 14, 15 attached thereto are housed in a box-shaped cassette C. At this time, the plurality of semiconductor wafers 1 are arranged upright with their thickness directions facing the left-right direction (Y direction) and lined up in the Y direction. The cassette C is placed in a so-called batch-type oven furnace F, and the cassette C is subjected to a heat treatment.

[0029] However, the internal space of the oven F is much larger than the size of the cassette C and the semiconductor wafer 1. This makes it easy for the temperature inside the oven to become non-uniform. In addition, since it takes time for the temperature inside the oven to stabilize, this may affect the throughput of the entire manufacturing process. In addition, as described above, as the diameter of the semiconductor wafer 1 increases, the cassette C itself also becomes larger, which may cause a problem that automatic transportation becomes difficult.

[0030] Therefore, the present inventors have come up with the present invention by focusing on an effective method for heating the protective films 14, 15 attached to the semiconductor wafer 1. Specifically, in this embodiment, the first protective film 14 and the second protective film 15 attached to the back surface and the outer peripheral edge of the ribbed semiconductor wafer 1 are directly heated by the hot plate 2.

[0031] Here, a partial configuration of the semiconductor manufacturing apparatus 100 according to the present embodiment will be described with reference to Figures 4 and 5. Note that the semiconductor manufacturing apparatus 100 is not limited to the configuration shown in Figures 4 and 5, and can be modified as appropriate.

[0032] 4 and 5, the semiconductor manufacturing apparatus 100 includes a transfer robot H and a hot plate 2. Note that the semiconductor manufacturing apparatus 100 is not limited to these components and may include other components.

[0033] The transport robot H is formed of a plate-like body having a U-shape in a planar view. The transport robot H can place the semiconductor wafer 1 on the upper surface and hold it by suction. For example, the transport robot H may be provided with a suction hole for holding the semiconductor wafer 1 by suction. The transport robot H can be moved to a desired location in the device by a transport mechanism (not shown). This allows the semiconductor wafer 1 to be transported to a predetermined location in the device. The transport robot H may hold the semiconductor wafer 1 by another holding method other than suction holding. The transport robot H is not limited to a plate-like body having a U-shape in a planar view, but may be a plate-like body of a different shape in accordance with the transport mechanism or the holding method of the semiconductor wafer 1.

[0034] The hot plate 2 is configured by incorporating a heater (not shown) into a disk-shaped base 20. The base 20 is circular in plan view and is formed to be sufficiently larger than the outer diameter of the semiconductor wafer 1. The base 20 is not limited to a circular shape and may be formed in any shape, such as a rectangle. The upper surface of the base 20 serves as a heating surface capable of heating the semiconductor wafer 1 (first protective film 14 and second protective film 15). The heating surface can be heated to a desired temperature by a heater. The heating surface may be coated with a resin to prevent sticking, as will be described in detail later.

[0035] The hot plate 2 also has push-up pins 21 that can protrude and retract from the heating surface. Specifically, the push-up pins 21 are formed of a cylindrical shaft extending in the Z direction. In a plan view, a plurality of push-up pins 21 (three in this embodiment) are arranged at equal angular intervals in the circumferential direction. The plurality of push-up pins 21 are arranged biased toward the outer periphery of the base 20, and more specifically, are arranged at a location corresponding to a location directly below the rib 11 of the semiconductor wafer 1. The push-up pins 21 have rounded upper ends and are configured to be protruded and retracted in the Z direction from the heating surface. The upper ends of the push-up pins 21 are capable of abutting against the rear side (first protective film 14 and second protective film 15) of the semiconductor wafer 1. The push-up pins 21 in FIG. 5 are not shown in the cross-sectional view, but are shown for convenience of explanation. For this reason, FIG. 5 does not limit the position of the push-up pins 21, and the push-up pins 21 may be located anywhere in the circumferential direction as long as they are located directly below the rib 11. Similarly, the number of the push-up pins 21 can be changed as appropriate. The same applies to Figs. 11, 14 to 16, 18, and 19 shown below.

[0036] According to the semiconductor manufacturing apparatus 100 configured in this manner, the back surface of the semiconductor wafer 1 is placed facing the heating surface of the hot plate 2, and the first protective film 14 and the second protective film 15 can be directly heated by the hot plate 2 (see FIG. 11 described later). As a result, even if air bubbles are generated between the semiconductor wafer 1 and each protective film, the adhesive layer of the protective film is softened by the temperature, making it easier to remove the air bubbles. In other words, it is possible to improve the adhesion of the protective film to the semiconductor wafer 1.

[0037] Furthermore, the hot plate 2 can reduce the time required for the temperature to stabilize at a desired temperature compared to heating in a conventional batch-type oven furnace F. Furthermore, in the case of the hot plate 2, automatic transportation can be achieved by the transport robot H, which was difficult with the conventional batch-type oven furnace F. Therefore, the throughput of the device can be improved and the semiconductor wafers 1 can be processed efficiently.

[0038] Next, a method for manufacturing a semiconductor device according to the present embodiment will be described with reference to Figs. 6 to 12. Fig. 6 is a flow chart showing an example of a method for manufacturing a semiconductor device according to the present embodiment. Figs. 7 to 12 are schematic diagrams showing an example of a process of the method for manufacturing a semiconductor device according to the present embodiment. In particular, Figs. 11A-11C show an operational transition diagram of workpiece transportation during the protective film heating process. Note that the method for manufacturing a semiconductor device shown below is merely an example, is not limited to this configuration, and can be modified as appropriate.

[0039] As shown in FIG. 6, the method for manufacturing a semiconductor device according to the present embodiment includes the following steps: (1) a surface element structure formation step (step S1: see FIG. 7 ); (2) a rib forming step (step S2: see FIG. 8); (3) a back surface etching process (step S3); (4) a backside ion implantation process (step S4); (5) a heat treatment step (step S5); (6) An oxide film removing step (step S6); (7) A back electrode forming process (step S7); (8) A backside film attaching process (step S8: see FIG. 9 ); (9) A peripheral film attachment process (step S9: see FIG. 10 ); (10) a protective film heating step (step S10: see FIG. 11 ); (11) a surface plating process (step S11: see FIG. 12 ); (12) An outer peripheral film peeling step (step S12); (13) A back surface film peeling step (step S13). The order of these steps can be changed as appropriate as long as no contradiction occurs.

[0040] First, as shown in Fig. 7, in the surface element structure forming step, various element structures (not shown) are formed on the surface of a semiconductor wafer 1 having a substantially uniform thickness of, for example, about 700 µm. For example, the emitter electrode of the front surface element structure consisting of a MOS gate (insulating gate consisting of metal-oxide film-semiconductor) structure of a field stop (FS) type IGBT is formed. The emitter electrode may be, for example, a metal film mainly composed of aluminum (Al). The emitter electrode may be patterned in the region where each semiconductor chip is to be formed. The element structure is formed by an existing method. A plating layer is selectively formed on the surface of the emitter electrode in a surface plating step (S11) described later.

[0041] Next, a rib forming process is carried out. As shown in Fig. 8, in the rib forming process, the center of the back surface of the semiconductor wafer 1 is ground, and a ring-shaped rib 11 that is thicker than the center is formed on the outer periphery of the semiconductor wafer 1. The thickness of the remaining part of the ground recess 10 may be, for example, about 100 µm. By reducing the thickness of the recess 10, the resistance component of the semiconductor substrate in the semiconductor device can be reduced.

[0042] Next, a back surface etching process is performed. In the back surface etching process, the unevenness formed on the back surface of the semiconductor wafer 1 by grinding or the like in advance and the damage caused on the back surface by grinding are removed by etching. The method of removing the unevenness is not limited to etching, and various methods can be adopted. The amount of etching may be about 20 μm, for example. This removes the damage caused by grinding, and the mechanical stress caused by the damage caused by grinding can be alleviated.

[0043] Next, a backside ion implantation process is performed. In the backside ion implantation process, ions (dopants) are implanted into the backside of the semiconductor wafer 1. The ion implantation method may be an existing method. For example, ion implantation of n-type impurities for forming an n-type buffer layer and ion implantation of p + Then, ion implantation of p-type impurities to form a p-type collector layer may be performed.

[0044] Next, a heat treatment step is performed. In the heat treatment step, the semiconductor wafer 1 is heated to a predetermined temperature. This activates the ions implanted in the semiconductor wafer 1. Various heating methods can be used.

[0045] Next, an oxide film removing process is carried out. In the oxide film removing process, the hardened layer (oxide film) on the surface of the semiconductor wafer 1 is removed by etching or the like. The removal of the surface hardened layer is not limited to etching, and various methods can be adopted. Specifically, the surface hardened layer is a natural oxide film or the like formed on the surface layer of the semiconductor wafer 1, and may be removed by, for example, dilute hydrofluoric acid (HF).

[0046] Next, a back surface electrode formation process is performed. In the back surface electrode formation process, an electrode is formed on the back surface of the semiconductor wafer 1. The electrode is formed of a metal film of a predetermined thickness, for example, by vapor deposition or sputtering. The electrode is formed, for example, by laminating an aluminum layer, a titanium layer, a nickel layer, and a gold layer in this order.

[0047] Next, a back surface film attachment step is performed. As shown in Fig. 9, in the back surface film attachment step, a protective film 14 is attached to the entire back surface of the semiconductor wafer 1. As described above, the recesses 10 and the ribs 11 are entirely covered with the protective film 14. The attachment of the protective film 14 may be performed automatically by a device or may be performed manually. Also, the protective film 14 may be attached in a vacuum to prevent air bubbles from being trapped between the semiconductor wafer 1 and the protective film 14.

[0048] Next, a peripheral film attachment step is performed. As shown in Fig. 10, in the peripheral film attachment step, protective film 15 is attached so as to cover the peripheral edge of protective film 14 and the outer periphery of rib 11. At the peripheral edge of semiconductor wafer 1, the upper and lower surfaces are sandwiched between protective film 15. In addition, the peripheral edge of protective film 14 is sandwiched between semiconductor wafer 1 and protective film 15. The attachment of protective film 15 may be performed automatically by a device or may be performed manually.

[0049] Next, a protective film heating step is performed. As shown in Fig. 11, in the protective film heating step, first, the semiconductor wafer 1 is transported to the hot plate 2 by the transport robot H. The semiconductor wafer 1 with the protective films 14, 15 attached thereto is sucked and held by the transport robot H. Specifically, as shown in Fig. 11A, the upper surface of the transport robot H abuts against the lower surface 15a of the protective film 15 covering the rib 11, and the protective film 15 is sucked to the upper surface of the transport robot H.

[0050] The transport robot H transports the semiconductor wafer 1 directly above the hot plate 2. The back surface of the semiconductor wafer 1 is placed facing the heating surface of the hot plate 2. Specifically, as shown in FIG. 11B, the hot plate 2 has three lifting pins 21 protruding at a predetermined height from the upper surface (heating surface) of the base 20. The transport robot H moves so that the outer periphery (ribs 11) of the semiconductor wafer 1 is positioned directly above each of the lifting pins 21.

[0051] Furthermore, the transport robot H is adjusted to a height where the lower surface of the protective film 15 abuts against the tips of the push-up pins 21. Then, the transport robot H releases the suction hold of the semiconductor wafer 1, and is adjusted to a height where it is separated from the lower surface 15a of the protective film 15, and retreats from below the semiconductor wafer 1. As shown in Fig. 4, the transport robot H has a U-shape in a plan view, and is disposed so as to pass between the push-up pins 21 in a plan view, so that the transport robot H does not interfere with the push-up pins 21. In the above, in order to prevent defects (such as cracks and chips) during transportation of the semiconductor wafer 1 having a ribbed shape, the case has been shown in which the semiconductor wafer 1 is transported while being suction-held by the transport robot H at the ribs 11, but the semiconductor wafer 1 may be held by another method. For example, a countersink may be provided in the transport robot H and the semiconductor wafer 1 may be held by placing it in the countersink. Also, the semiconductor wafer 1 may be held from its front surface by a Bernoulli chuck.

[0052] When the transport robot H retreats from below the semiconductor wafer 1, the semiconductor wafer 1 is supported by the three push-up pins 21. Thereafter, the three push-up pins 21 are retracted into the base 20. As a result, the semiconductor wafer 1 is lowered, and the lower surface 15a of the protective film 15 comes into contact with the heating surface, as shown in FIG. 11C.

[0053] The heating surface of the hot plate 2 is heated in advance to a desired temperature by a heater. For example, the temperature of the heating surface is heated to about 70° C. to 80° C. Therefore, it is possible to directly heat the protective films 14 and 15 from the moment the semiconductor wafer 1 comes into contact with the heating surface.

[0054] The protective films 14, 15 are softened by being heated. As a result, even if air bubbles are trapped between the semiconductor wafer 1 and the protective films 14, 15, the air bubbles can be removed to improve the adhesion between them. Note that a certain gap is left between the protective film 14 and the heating surface at the recess 10 of the semiconductor wafer 1. However, the gap is not large enough to affect the heating of the protective film 14, so that the heat from the heating surface can be directly transferred to the protective film 14. Note that the gap between the lower surface of the protective film 14 and the heating surface may be, for example, about 100 μm.

[0055] Next, a surface plating step (which may simply be referred to as a plating step) is carried out. As shown in FIG. 12, in the surface plating step, a plating process is performed on the surface of the semiconductor wafer. Specifically, a plating layer 16 of a predetermined thickness is formed on the surface of the semiconductor wafer 1. The plating layer 16 is formed on the entire surface of the emitter electrode on the upper surface of the semiconductor wafer 1 where the protective films 14, 15 are not attached. The plating layer 16 may be a layer formed by laminating a nickel plating layer and then laminating a gold plating layer on the entire surface of the nickel plating layer. The plating layer 16 is formed by exposure to an electroless plating bath at about 70°C to 80°C for 40 to 50 minutes, for example.

[0056] Next, a peripheral film peeling step is performed. In the peripheral film peeling step, the protective film 15 is peeled off from the semiconductor wafer 1. The peeling off of the protective film 15 may be performed automatically by an apparatus or may be performed manually.

[0057] Next, a back surface film peeling process is performed. In the back surface film peeling process, the protective film 14 is peeled off from the semiconductor wafer 1. The peeling of the protective film 14 may be performed automatically by an apparatus or may be performed manually.

[0058] The subsequent steps are not directly related to the present invention, so a description thereof will be omitted.

[0059] As described above, in this embodiment, after the protective films 14, 15 are attached to the semiconductor wafer 1 on which the ribs 11 are formed, the protective films 14, 15 are directly heated on the heating surface of the hot plate 2. This makes it possible to remove air bubbles in the protective films 14, 15 in a short time and to manufacture a good semiconductor device without forming an unnecessary plating layer in the subsequent plating step.

[0060] Here, referring to Fig. 13, the temperature rise when the protective film is heated will be described by comparing the present application with the conventional method. In Fig. 13, the horizontal axis represents time, and the vertical axis represents temperature. The solid line in the graph represents the example of the present application, and the temperature is, for example, the temperature of the heating surface. The two-dot chain line in the graph represents the conventional example, and the temperature is the temperature inside the furnace.

[0061] As shown in FIG. 13, in the past, it took, for example, about 10 minutes to raise the temperature to the target heating temperature T. Furthermore, in the past, after the target heating temperature T was reached, it took another 10 to 20 minutes to actually process the semiconductor wafer 1. This affected the takt time of the device. In contrast, in the present application, it is possible to significantly shorten the time to reach the target heating temperature T, for example, to 2 to 3 minutes. Moreover, it is possible to shorten the time to actually process the semiconductor wafer 1, after the target heating temperature T is reached, to 1 to 2 minutes. As a result, it is possible to improve the throughput of the entire device. In this way, by using the hot plate 2, it is possible to shorten the rise time to reach the target heating temperature T and shorten the takt time of the entire heating process.

[0062] In addition, when applying the heating process of the protective films 14, 15 of the present invention, an example of various parameters of the semiconductor wafer 1 and the protective films 14, 15 is as follows. For example, as shown in Fig. 2, the thickness D1 of the semiconductor wafer 1 is 725 µm. The remaining thickness D2 of the semiconductor wafer 1 at the location where the recess 10 is formed is 100 µm. The depth D3 of the recess 10 is 625 µm. Note that D1 = D2 + D3.

[0063] Further, the distance D4 from the upper surface of the semiconductor wafer 1 to the lower surface of the protective film 15 is 905 μm. The distance D5 from the bottom surface of the recess 10 to the lower surface of the protective film 15 is 805 μm. Furthermore, the distance D6 from the lower surface of the protective film 14 located directly below the recess 10 to the lower surface of the protective film 15 is 755 μm. Note that this description does not limit the numerical values.

[0064] Note that various materials can be selected for the protective films 14 and 15, but for example, the protective film 15 is preferably made of a material that is more flexible than the protective film 14. This is because the protective film 15 is bent into a U-shape in cross section so as to cover the entire outer periphery of the rib 11, and therefore it is preferable that the protective film 15 is easy to bend. Furthermore, the adhesive layer of the protective films 14 and 15 may be made of a material whose adhesiveness changes when irradiated with ultraviolet (UV) rays or a material whose adhesiveness changes depending on the temperature.

[0065] Next, modified examples will be described with reference to Figures 14 to 19. Figures 14 to 19 are schematic diagrams of hot plates according to modified examples.

[0066] In the above embodiment, the case where the upper surface of the base 20 is the heating surface that directly contacts the lower surface (protective film 15) of the semiconductor wafer 1 has been described, but the present invention is not limited to this configuration. For example, as shown in FIG. 14, a resin film 22 of a predetermined thickness may be formed on the upper surface of the base 20, and at least a part of the protective film 15 may be brought into contact with the resin film 22. In this case, the upper surface of the resin film 22 becomes the heating surface. The resin film 22 is formed of, for example, a fluorine-based resin. By forming the resin film 22, it is possible to prevent the protective film 15 from sticking to the hot plate 2. In addition, the thickness of the resin film 22 is preferably 20 μm to 300 μm. More preferably, the thickness of the resin film 22 is 20 μm to 50 μm. Within this range, it is possible to effectively prevent the protective film 15 from sticking while ensuring thermal conductivity.

[0067] Also, as shown in FIG. 15, a circular protrusion 23 may be formed on the heating surface (upper surface of the base 20) of the hot plate 2 at a location corresponding to the recess 10 of the semiconductor wafer 1. The circular protrusion 23 has an outer diameter smaller than the diameter of the inner periphery of the rib 11 and protrudes in the Z direction by a predetermined thickness. It is preferable that the circular protrusion 23 is formed to a size that fits within the recess 10 when the semiconductor wafer 1 is placed on the hot plate 2. According to this configuration, the circular protrusion 23 fills the gap between the lower surface of the protective film 14 and the heating surface, and the heating surface is closer to the lower surface of the protective film 14. The height of the circular protrusion 23 may be a height at which the protective film 14 and the protective film 15 contact the heating surface. As a result, the protective film 14 can be effectively heated. The upper surface of the circular protrusion 23 may be in contact with the protective film 14. Also, when the semiconductor wafer 1 is placed on the hot plate 2, the circular protrusion 23 functions as a positioning member for the recess 10.

[0068] 16, a resin film 22 may be formed on the entire upper surface of the base 20 on which the circular protrusion 23 is formed. With this configuration, it is possible to suppress the adhesion of the protective film 14 while enhancing the heating effect of the protective film 14.

[0069] 17 and 18, when a circular protrusion 23 is formed on the upper surface of the base 20, the hot plate 2 may have a groove 24 formed on the upper surface of the circular protrusion 23 and a communication hole 25 communicating with the groove 24. The communication hole 25 is formed to extend in the Z direction at the center of the base 20. A suction source (not shown) may be connected to the lower end of the communication hole 25. The grooves 24 extend radially from the communication hole 25 toward the outside in the radial direction. The grooves 24 preferably have a semicircular cross-sectional shape when viewed from the extension direction (radial direction). With such grooves 24 and communication holes 25, it is possible to ensure an escape route for air between the recess 10 and the circular protrusion 23 when the semiconductor wafer 1 is placed on the hot plate 2. Furthermore, when the heated semiconductor wafer 1 is pushed up by the push-up pin 21, the groove 24 and the communication hole 25 serve as an air passage, making it possible to realize the pushing-up operation of the semiconductor wafer 1 without applying stress to the recess 10.

[0070] In the above embodiment, the rib-shaped semiconductor wafer 1 is used to suppress the overall warpage, but it is assumed that the semiconductor wafer 1 itself may still warp slightly. For example, as shown in FIG. 19, it is assumed that the semiconductor wafer 1 is curved such that the thin central portion is convex upward when the concave portion 10 faces downward. In this case, it is preferable that the upper surface (heating surface) of the circular convex portion 23 facing the curved portion also has a spherical shape with the upper side being convex. By forming the heating surface in accordance with (along with) the warped shape of the semiconductor wafer 1, it is possible to minimize the gap between the heating surface and the protective film 14 and further enhance the heating effect. In this case, a resin film 22 may be formed on the upper surface of the circular convex portion 23.

[0071] As described above, the present embodiment and the modified examples have been described, but other embodiments may be obtained by combining the above-described embodiment and modified examples in whole or in part.

[0072] In addition, the present embodiment is not limited to the above-mentioned embodiment and modification, and may be modified, substituted, or altered in various ways without departing from the spirit of the technical idea. Furthermore, if the technical idea can be realized in a different way due to technological progress or a different derived technology, it may be implemented using that method. Therefore, the claims cover all embodiments that may be included in the scope of the technical idea.

[0073] The features of the above embodiment are summarized below. The manufacturing method of the semiconductor device according to the above embodiment includes a rib forming process of grinding the center of the back surface of a semiconductor wafer to form a ring-shaped rib that is thicker at the outer edge of the semiconductor wafer than at the center, a back surface film attaching process of attaching a first protective film to the back surface of the semiconductor wafer, an outer peripheral film attaching process of attaching a second protective film so as to cover the outer edge of the first protective film and the outer periphery of the rib, a heating process of placing the back surface of the semiconductor wafer opposite the heating surface of a hot plate and directly heating the first protective film and the second protective film with the hot plate, and a plating process of applying a plating process to the surface of the semiconductor wafer.

[0074] In the method for manufacturing a semiconductor device according to the above embodiment, a resin film of a predetermined thickness is formed on the heating surface of the hot plate, and in the heating process, at least a portion of the second protective film is in contact with the resin film.

[0075] In the method for manufacturing a semiconductor device according to the above embodiment, the resin film is made of a fluorine-based resin.

[0076] In the manufacturing method of a semiconductor device according to the above embodiment, a circular protrusion having an outer diameter smaller than the diameter of the inner circumference of the rib is formed on the heating surface of the hot plate, and in the heating process, the semiconductor wafer is placed on the heating surface of the hot plate so that the circular protrusion fits inside the rib.

[0077] In the method for manufacturing a semiconductor device according to the above embodiment, the hot plate has a groove formed in the upper surface of the circular convex portion and a communication hole communicating with the groove.

[0078] In the method for manufacturing a semiconductor device according to the above embodiment, the semiconductor wafer is curved so as to be convex upward, and the heating surface of the hot plate has a spherical shape so as to be convex upward.

[0079] The hot plate of the above embodiment is a hot plate that heats a first protective film and a second protective film attached to a semiconductor wafer, wherein the center of the back surface of the semiconductor wafer is ground to form a ring-shaped rib that is thicker than the center at the outer edge of the semiconductor wafer, the first protective film is attached to the back surface of the semiconductor wafer, and the second protective film is attached so as to cover the outer edge of the first protective film and the outer periphery of the rib, the back surface of the semiconductor wafer is arranged opposite the first protective film and the second protective film, and the hot plate has a heating surface that directly heats the first protective film and the second protective film.

[0080] In the hot plate according to the above embodiment, a resin film having a predetermined thickness is formed on the heating surface, and the second protective film is heated with at least a portion of the second protective film in contact with the resin film.

[0081] In the hot plate according to the above embodiment, the resin film is made of a fluorine-based resin.

[0082] In the hot plate according to the above embodiment, a circular protrusion having an outer diameter smaller than the diameter of the inner periphery of the rib is formed on the heating surface, and the semiconductor wafer is placed on the heating surface so that the circular protrusion fits inside the rib.

[0083] The hot plate according to the above embodiment has a groove formed in the upper surface of the circular protrusion, and a communication hole communicating with the groove.

[0084] In the hot plate according to the above embodiment, the semiconductor wafer is curved so as to be convex upward, and the heating surface has a spherical shape so as to be convex upward.

[0085] The hot plate according to the above embodiment has push-up pins that are disposed directly below the ribs and can rise and fall relative to the heating surface. [Industrial Applicability]

[0086] As described above, the present invention has the effect of improving the adhesion of a protective film to a semiconductor wafer and improving throughput, and is particularly useful in a manufacturing method for a semiconductor device and a hot plate used therein. [Explanation of symbols]

[0087] 100 Semiconductor manufacturing equipment 1. Semiconductor wafer 2. Hot plate 10 Recess 11 Ribs 12 Chamfer 13 Slope 14 First protective film 15 Second protective film 15a: Lower surface of second protective film 16 Plating layer 20 Foundations 21 Push-up pin 22 Resin Film 23 Circular protrusion 24 groove 25 Communication hole

Claims

1. A rib forming process in which the center of the back surface of a semiconductor wafer is ground to form a ring-shaped rib that is thicker on the outer periphery of the semiconductor wafer than on the center; a back surface film attaching step of attaching a first protective film to a back surface of the semiconductor wafer; a peripheral film attaching step of attaching a second protective film so as to cover the peripheral edge of the first protective film and the outer periphery of the rib; a heating step of placing a back surface of the semiconductor wafer facing a heating surface of a hot plate and directly heating the first protective film and the second protective film with the hot plate; a plating step of plating a surface of the semiconductor wafer; Equipped with A resin film having a predetermined thickness is formed on the heating surface of the hot plate, In the heating step, at least a portion of the second protective film is in contact with the resin film.

2. The method for manufacturing a semiconductor device according to claim 1 , wherein the resin film is made of a fluorine-based resin.

3. A rib forming process in which the center of the back surface of the semiconductor wafer is ground to form a ring-shaped rib that is thicker on the outer periphery of the semiconductor wafer than the center; a back surface film attaching step of attaching a first protective film to a back surface of the semiconductor wafer; a peripheral film attaching step of attaching a second protective film so as to cover the peripheral edge of the first protective film and the outer periphery of the rib; a heating step of placing a back surface of the semiconductor wafer facing a heating surface of a hot plate and directly heating the first protective film and the second protective film with the hot plate; a plating step of plating a surface of the semiconductor wafer; Equipped with a circular protrusion having an outer diameter smaller than the diameter of the inner periphery of the rib is formed on the heating surface of the hot plate; In the heating step, the semiconductor wafer is placed on the heating surface of the hot plate such that the circular protrusion is located inside the rib.

4. The hot plate is A groove formed on an upper surface of the circular protrusion; The method for manufacturing a semiconductor device according to claim 3 , further comprising: a through hole communicating with said groove.

5. The semiconductor wafer is curved so that the upper side is convex, 5. The method for manufacturing a semiconductor device according to claim 3, wherein the heating surface of the hot plate has a spherical shape with an upward convex surface.

6. A hot plate for heating a first protective film and a second protective film attached to a semiconductor wafer, comprising: a ring-shaped rib having a thickness greater than that of a center of the semiconductor wafer is formed on an outer periphery of the semiconductor wafer by grinding a center of the back surface of the semiconductor wafer; the first protective film is attached to the back surface of the semiconductor wafer; the second protective film is attached so as to cover an outer periphery of the first protective film and an outer periphery of the rib, a heating surface that faces the back surface of the semiconductor wafer and directly heats the first protective film and the second protective film; A resin film having a predetermined thickness is formed on the heating surface, The second protective film is heated with at least a portion of the second protective film in contact with the resin film.

7. 7. The hot plate according to claim 6, wherein the resin film is made of a fluorine-based resin.

8. A hot plate for heating a first protective film and a second protective film attached to a semiconductor wafer, comprising: a ring-shaped rib having a thickness greater than that of a center of the semiconductor wafer is formed on an outer periphery of the semiconductor wafer by grinding a center of the back surface of the semiconductor wafer; the first protective film is attached to the back surface of the semiconductor wafer; the second protective film is attached so as to cover an outer periphery of the first protective film and an outer periphery of the rib, a heating surface that faces the back surface of the semiconductor wafer and directly heats the first protective film and the second protective film; A circular protrusion having an outer diameter smaller than the diameter of the inner periphery of the rib is formed on the heating surface, The semiconductor wafer is placed on the heating surface such that the circular protrusion is located inside the rib.

9. A groove formed on an upper surface of the circular protrusion; The hot plate according to claim 8 , further comprising a communication hole communicating with said groove.

10. The semiconductor wafer is curved so that the upper side is convex, 10. The hot plate according to claim 8, wherein the heating surface has a spherical shape with an upward convex surface.

11. 11. The hot plate according to claim 6, further comprising push-up pins arranged directly below the ribs and capable of rising and falling relative to the heating surface.

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