JP2010283294A - Method for manufacturing semiconductor device and grinder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent contamination of a silicon wafer due to heavy metal in a device post-step. <P>SOLUTION: This manufacturing method includes; a rear surface grinding step S31 for grinding a rear surface of a silicon substrate to make thickness to ≤100 μm; a rear surface polishing step S32 for polishing the ground rear surface of the silicon substrate; and a heavy metal removing step S33 for immersing at least the rear surface of the silicon substrate into an acid aqueous solution. According to this method, the heavy metal introduced in the rear surface grinding step or the like is extracted by the acid aqueous solution, thereby removing the heavy metal from the silicon wafer. Thus, contamination of the silicon wafer due to the heavy metal in the device post-step is prevented. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for manufacturing a semiconductor device suitable for mounting on a multichip package (MCP). The present invention also relates to a grinder device, and more particularly to a grinder device for grinding or polishing the back surface of a silicon wafer.

  One of the problems in the semiconductor process is that heavy metals as impurities are mixed in the silicon wafer. When heavy metals diffuse into a device region formed on the surface side of a silicon wafer, device characteristics such as pause time failure, retention failure, junction leak failure, and dielectric breakdown of the oxide film are significantly adversely affected. For this reason, in order to suppress the heavy metal mixed in the silicon wafer from diffusing into the device region, the gettering method is generally adopted. Gettering is aimed at preventing heavy metal contamination in a device pre-process for forming a device on the surface of a silicon substrate.

  On the other hand, heavy metal contamination in post-device processes such as thinning of the silicon substrate, wire bonding, or resin encapsulation performed after the pre-device process has not been particularly emphasized. This is a process of grinding and removing the back surface of the silicon wafer in the early stage of the device post-process. Scratches and damage introduced during the back surface grinding act as a gettering source by strong extrinsic gettering (EG). Because.

  However, the final chip thickness is becoming thinner year by year, and in particular, the chip mounted on the MCP is often made thinner to 100 μm or less, and depending on the product, it is currently made thinner to 25 μm or less, and in the future it will be 10 μm or less. Both are predicted. When the thickness of the chip is reduced to 100 μm or less, there arises a problem that the silicon wafer is easily broken due to damage during back grinding. In order to solve such a problem, it is necessary to newly add a process of removing damage after the back surface grinding, that is, a back surface polishing process and a wet etching process by the CMP method.

  However, if the damage on the back surface of the silicon wafer is removed by back surface polishing, the back surface gettering source also disappears, and the EG effect is lost. Moreover, since a thin silicon wafer has a thin intrinsic gettering (IG) layer, a sufficient IG effect cannot be expected with a normal IG layer formed of oxygen precipitates. More specifically, even in the case of an epitaxial wafer or silicon wafer using the IG method, a DZ layer having no oxygen precipitation nuclei including the thickness of the epitaxial film is formed by heat treatment to have a thickness of 10 μm or more from the wafer surface. When the final film thickness of the chip becomes thinner, the IG layer hardly exists and the impurity metal generated in the device post-process cannot be gettered at all.

  As described above, in the thin semiconductor device in which the back surface of the silicon wafer is polished, the problem of heavy metal contamination in the device post-process is beginning to become apparent.

  In this regard, Patent Document 1 discloses a technique for providing gettering capability to a thinned wafer back surface by various methods. For example, a method of depositing a polycrystalline silicon film or nitride film on the back surface of a thinned silicon wafer, a method of damaging the back surface using silica particles, a method of forming a damage layer on the back surface by ion implantation, etc. ing.

JP 2006-41258 A JP 2006-32859 A

  However, since deposition of a polycrystalline silicon film or a nitride film requires a film forming apparatus such as a CVD apparatus, it is not practical for a mass-produced product to form these in a device post-process. Further, the method of damaging the back surface using silica particles is considered to be effective if the chip thickness is thick to some extent, but as already explained, the final chip thickness is 100 μm or less, and in the future 10 μm. If the thickness is reduced to a certain extent, the bending strength is reduced due to the introduction of physical damage due to silica particles and the like, and the problem of chip cracking occurs.

  On the other hand, when a silicon wafer is brought into contact with an acid aqueous solution, it has been conventionally known that heavy metals taken into the silicon wafer are extracted, for example, disclosed in Patent Document 2. Patent Document 2 shows that Cu and Ni in a silicon wafer can be almost completely extracted by immersing a normal silicon wafer having a thickness of 500 to 800 μm in an acid aqueous solution at 200 ° C. for 48 minutes.

  However, Patent Document 2 discloses a method for analyzing heavy metals in a silicon wafer to the last, and it is not assumed that heavy metals in a silicon wafer are removed in a mass production process. In fact, it is not practical to add a process of immersing a silicon wafer in an acid aqueous solution at 200 ° C. for 48 minutes in the device post-process. In the first place, there is no recognition of the problem that heavy metals are mixed into the silicon wafer by back surface grinding or back surface polishing in the device post-process.

  The present invention has been made from such a background, and provides a semiconductor device manufacturing method capable of eliminating heavy metal contamination in a device post-process, and a grinder apparatus capable of eliminating heavy metal contamination. It is.

  A method for manufacturing a semiconductor device according to the present invention includes a thinning step of removing a part of a silicon substrate having a semiconductor element formed on a front surface from the back side, thereby reducing the thickness of the silicon substrate to 100 μm or less. In addition, a backside polishing step for polishing the backside of the silicon substrate, and a heavy metal removal for bringing at least the backside of the silicon substrate into contact with an aqueous acid solution or hot water simultaneously with the thinning step or the backside polishing step or after completion of the backside polishing step. And a process.

  According to the present invention, since the back surface of the silicon substrate is brought into contact with the aqueous acid solution or hot water simultaneously with the thinning step or the back surface polishing step in the device post-process or after the back surface polishing step, mainly the thinning step or The heavy metal mixed in the back surface polishing process can be removed online in the device post-process.

  In the present invention, the acid aqueous solution is preferably a nitric acid aqueous solution, a hydrofluoric acid aqueous solution or a hydrogen peroxide solution. According to this, it is possible to remove heavy metals such as Cu and Ni that have a significant adverse effect on the device region.

  In the present invention, the temperature of the acid aqueous solution in the heavy metal removing step is preferably room temperature to 200 ° C., more preferably room temperature to 100 ° C. This makes it possible to easily incorporate the heavy metal removal step into the device post-process. Even if the back grind protective tape used for grinding or polishing is attached to the surface of the silicon wafer, the back grind protective tape will not deteriorate if the temperature of the aqueous acid solution is not lower than room temperature and not higher than 100 ° C. .

  In the present invention, the contact time between the back surface of the silicon substrate and the aqueous acid solution in the heavy metal removal step is preferably 5 minutes or less. According to this, it becomes possible to prevent a significant decrease in productivity in the device post-process. Moreover, since the semiconductor device targeted by the present invention is thinned to 100 μm or less by the thinning step, a sufficient removal effect can be obtained by treating it with an acid aqueous solution for 1 minute to 5 minutes.

  In the present invention, the heavy metal removal step is preferably performed by supplying the acid aqueous solution instead of the slurry after stopping the supply of the slurry used in the thinning step or the back surface polishing step. According to this, since the heavy metal is removed continuously after the thinning process or the back surface polishing process, the productivity is hardly lowered. Further, since only the aqueous acid solution needs to be supplied instead of the slurry, the apparatus and equipment are hardly changed.

  The thinning step, the back surface polishing step, and the heavy metal removal step are preferably performed in a state where a back grind protective tape is attached to the surface of the silicon substrate. According to this, since the thinning process, the back surface polishing process, and the heavy metal removal process can be continuously performed in a state where the back grind protective tape is applied, high productivity can be ensured.

  The grinder device according to the present invention is a grinder device for grinding or polishing a back surface of a silicon wafer, and a pad that faces the back surface of the silicon wafer, and a supply unit that supplies an acid aqueous solution to the back surface of the silicon wafer. It is characterized by providing. According to the present invention, it is possible to remove heavy metals in a silicon wafer continuously with grinding or polishing of the silicon wafer.

  As described above, according to the present invention, the device post-process, particularly the thinning process and the back surface polishing, can be performed without using a film forming apparatus or an ion implanter in the device post-process or physically damaging the back surface of the chip. The heavy metal introduced into the back surface of the silicon substrate in the process can be removed. As a result, it is possible to increase the yield of semiconductor devices thinned to 100 μm or less while preventing a significant increase in manufacturing costs in the device post-process and a reduction in the bending strength of the chip.

1 is a schematic cross-sectional view illustrating a semiconductor device 10 structure according to a preferred embodiment of the present invention. It is a schematic sectional drawing which shows the structure of the semiconductor device 10 by a modification. 1 is a schematic cross-sectional view showing a structure of an MCP 20 using a semiconductor device 10. 4 is a flowchart for roughly explaining a method for manufacturing the semiconductor device 10. It is a flowchart for demonstrating a device back process (step S30). It is a schematic diagram which shows the structure of the grinder apparatus 30 by preferable embodiment of this invention.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a schematic cross-sectional view illustrating the structure of a semiconductor device 10 according to a preferred embodiment of the present invention.

  As shown in FIG. 1, the semiconductor device 10 according to the present embodiment includes a silicon substrate 11 and a device region 12 provided on the surface 11 a side of the silicon substrate 11. The thickness of the silicon substrate 11 is reduced to 100 μm or less, which makes it suitable for mounting on an MCP. The back surface 11b of the silicon substrate 11 is mirror-polished. Thereby, although the total thickness is reduced to 100 μm or less, the bending strength is ensured, so that the chip is prevented from cracking.

The silicon substrate 11 is not particularly limited, but is a so-called P-substrate doped with boron, and the specific resistance of the silicon substrate 11 based on the boron concentration is adjusted to 1 Ω · cm or more and 100 Ω · cm or less. . Although not particularly limited, the initial oxygen concentration of the silicon substrate 11 is preferably 7 × 10 ¹⁷ atoms / cm ³ or more. This is because the oxygen precipitate formed by the heat treatment functions as a gettering source for heavy metals such as Cu and Ni. The oxygen precipitation heat treatment for forming oxygen precipitates on the silicon substrate 11 may be performed before the device pre-process, or may be substituted by a thermal process in the device pre-process.

  The device region 12 is a region where a semiconductor element such as a MOS transistor, a passive element such as a cell capacitor, and a metal wiring are formed. Among these, at least the semiconductor element is formed on the surface layer portion including the surface 11 a of the silicon substrate 11. Further, the metal wiring and the like are formed above the surface 11a of the silicon substrate 11. Although the boundary between the device region 12 and other regions in the silicon substrate 11 is not necessarily clear, the thickness of the device region 12 can be defined as the maximum depth of the depletion layer. The maximum depth of the depletion layer depends on the device design, but is about 10 μm, for example.

  The device configuration formed in the device region 12 differs depending on the type of the semiconductor device 10. For example, examples of the semiconductor device 10 include logic devices such as MPU and DSP, and memory devices such as DRAM and flash memory.

  In the present embodiment, the silicon substrate 11 hardly contains heavy metals such as Cu and Ni. This is because heavy metals are extracted and removed from the back surface 11b side of the silicon substrate 11 by the heavy metal removal step described later.

The above is the configuration of the semiconductor device 10. The configuration of the semiconductor device 10 is not limited to the configuration shown in FIG. 1. For example, as shown in FIG. 2, an epitaxial film 13 may be provided on the surface 11 a of the silicon substrate 11. In this case, the device region 12 is formed on the surface layer of the epitaxial film 13. When such an epitaxial film 13 is used, the dopant species and dopant concentration to the silicon substrate 11 are not particularly limited, but a so-called P + substrate doped with a high concentration of boron is preferably used. According to this, the heavy metal that has not been extracted is gettered by the boron contained in the silicon substrate 11. In this case, the dose of boron is preferably 1.2 × 10 ¹⁷ atoms / cm ³ or more and 5.5 × 10 ¹⁹ atoms / cm ³ or less (2 mΩ · cm to 200 mΩ · cm), preferably 4 × 10. More preferably, it is ¹⁷ atoms / cm ³ or more and less than 1 × 10 ¹⁸ atoms / cm ³ (20 mΩ · cm or more and 100 mΩ · cm or less).

  FIG. 3 is a schematic cross-sectional view showing the structure of the MCP 20 using the thinned semiconductor device 10. The MCP 20 shown in FIG. 3 has a configuration in which four semiconductor devices 10 are stacked on a package substrate 21. The semiconductor device 10 and the package substrate 21 that are vertically adjacent to each other are fixed by an adhesive 22. Further, the semiconductor device 10 and the package substrate 21 are connected by the bonding wire 23, whereby each semiconductor device 10 is electrically connected to the external electrode 24 via an internal wiring (not shown) provided on the package substrate 21. Connected. A sealing resin 25 for protecting the semiconductor device 10 and the bonding wire 23 is provided on the package substrate 21.

  In the MCP 20 having such a configuration, since the thickness of one semiconductor device 10 is reduced to, for example, about 100 μm, the entire thickness of the MCP can be reduced to, for example, about 1 mm. For this reason, the application to the use as which a low profile is requested | required, such as a mobile apparatus, is suitable.

  Next, a method for manufacturing the semiconductor device 10 will be described with reference to a flowchart.

  FIG. 4 is a flowchart for roughly explaining a method for manufacturing the semiconductor device 10. As shown in FIG. 4, the manufacturing process of the semiconductor device 10 is roughly classified into three processes: a silicon wafer manufacturing process (step S10), a device pre-process (step S20), and a device post-process (step S30). . Hereinafter, each process will be described in detail.

  The silicon wafer manufacturing process (step S10) is performed by cutting a silicon wafer from a silicon ingot pulled up by the Czochralski (CZ) method. The specific resistance of the silicon wafer can be adjusted by the amount of boron added to the silicon melt, and the initial oxygen concentration can be adjusted by convection control of the silicon melt. Moreover, an oxygen precipitate is formed by performing heat treatment as necessary. Further, an epitaxial film is formed as necessary.

  The device pre-process (step S20) is a process of forming a semiconductor element or the like on the silicon substrate 11 (or the epitaxial film 13). However, since it differs depending on the type of semiconductor device to be manufactured, details thereof are omitted. Examples of the semiconductor device include logic semiconductor devices such as MPU and DSP, and memory semiconductor devices such as DRAM and flash memory.

  FIG. 5 is a flowchart for explaining the device post-process (step S30) in the first embodiment.

  As shown in FIG. 5, in the device post-process, first, the back grinding of the silicon wafer is performed (step S31). The back surface grinding is performed by roughly grinding a part of the silicon substrate 11 from the back surface side, thereby reducing the thickness of the silicon substrate 11 to 100 μm or less. Note that this step (thinning step) is not limited to grinding but can be performed by etching or the like.

  Next, the polished back surface of the silicon substrate 11 is mirror-polished (step S32), whereby the damage introduced by the back surface grinding (step S31) is removed and the mechanical strength is increased. The back grinding (step S31) and back grinding (step S32) described above are performed in a state where a back grind protective tape is attached to the front side of the silicon wafer (silicon substrate 11) in order to protect the device region 12. Is preferred.

  In the above back grinding process (step S31) and back polishing process (step S32), particularly heavy metals such as Cu may enter from the back surface 11b of the silicon substrate 11. Such heavy metal introduced in the device post-process is sucked from the back surface 11b of the silicon substrate 11 in the next heavy metal removal process (step S33).

  The heavy metal removing step (step S33) is performed by immersing at least the back surface 11b of the silicon substrate 11 in an acid aqueous solution. Thereby, the heavy metal introduced from the back surface 11b of the silicon substrate 11 in steps S31 and S32 is sucked again from the back surface 11b of the silicon substrate 11. As a result, the silicon substrate 11 can be in a state where there is almost no heavy metal.

  The acid aqueous solution used in the heavy metal removing step (step S33) is preferably a nitric acid aqueous solution, a hydrofluoric acid aqueous solution, or a hydrogen peroxide solution. According to this, it becomes possible to effectively remove heavy metals such as Cu and Ni, which have a significant adverse effect on the device region. In addition, although the effect as acid aqueous solution is not acquired, it is possible to extract a heavy metal also using warm water instead of acid aqueous solution. The temperature of the hot water is preferably 40 ° C. or higher. This is because the effect of removing heavy metals cannot be obtained sufficiently when the temperature of the hot water is less than 40 ° C., particularly below room temperature. As described above, the heavy metal removal step (step S33) is preferably performed in a state where the back grind protection tape at the time of back surface grinding / polishing is attached to the front surface side of the silicon wafer.

  The temperature of the acid aqueous solution in the heavy metal removal step (step S33) is preferably room temperature or higher and 100 ° C. or lower. This makes it possible to easily incorporate the heavy metal removal step into the device post-process. Even if the back grind protective tape used for grinding or polishing is attached to the surface of the silicon wafer, the back grind protective tape will not deteriorate if the temperature of the aqueous acid solution is not lower than room temperature and not higher than 100 ° C. . On the other hand, as described in Patent Document 2, in order to almost completely extract Cu and Ni from a normal silicon wafer having a thickness of 500 to 800 μm, it is necessary to heat the acid aqueous solution to about 200 ° C. However, in this embodiment, since the silicon substrate 11 is thinned to 100 μm or less, it is not necessary to heat the acid aqueous solution to such a high temperature.

  The contact time between the back surface 11b of the silicon substrate 11 and the acid aqueous solution in the heavy metal removing step (step S33) is preferably 5 minutes or less. According to this, it becomes possible to prevent a significant decrease in productivity in the device post-process. On the other hand, as described in Patent Document 2, in order to almost completely extract Cu and Ni from a normal silicon wafer having a thickness of 500 to 800 μm, it is necessary to contact an acid aqueous solution for about 48 minutes. However, in this embodiment, since the silicon substrate 11 is thinned to 100 μm or less, it is not necessary to contact the acid aqueous solution for a long time.

  Next, the silicon wafer is diced into individual chips (step S34). Thereby, the chip | tip (semiconductor device 10) separated into pieces is completed.

  After that, when the separated semiconductor device 10 is mounted on a package substrate or the like and wire bonding or resin sealing is performed, the MCP is completed (step S35).

  Thus, in this embodiment, since the heavy metal introduced in the back surface grinding process (step S31) and the back surface polishing process (step S32) is removed from the back surface 11b side, diffusion of heavy metal to the device region 12 is prevented. Is prevented.

  In the above embodiment, the heavy metal removal step (step S33) is performed after the back surface grinding step (step S31) and the back surface polishing step (step S32), which are thinning steps, but the heavy metal removal step (step S33). ) Can be performed simultaneously with or continuously with the back surface grinding step (step S31) or the back surface polishing step (step S32). In this case, the backside grinding device or the backside polishing device needs to be slightly changed, but it is not necessary to separately perform the heavy metal removal step (step S33), so that the productivity is not lowered.

  A method of performing the heavy metal removal step (step S33) simultaneously with or continuously with the back surface grinding step (step S31) or the back surface polishing step (step S32) is not particularly limited, but the back surface grinding step (step S31). Alternatively, it is preferable to supply an aqueous acid solution instead of the slurry after stopping the supply of the slurry used in the back surface polishing step (step S32). According to this, the change of the back surface grinding device or the back surface polishing device can be minimized.

  FIG. 6 is a schematic diagram showing a configuration of a grinder device 30 according to a preferred embodiment of the present invention. The grinder device 30 can be used in the back grinding process (step S31) or the back grinding process (step S32).

A grinder device 30 shown in FIG. 6 includes a polishing head (grinding head) 31 that holds a silicon wafer 40, a rotating plate 33 to which a polishing pad (grinding pad) 32 is attached, and an abrasive such as silica (SiO ₂ ) fine particles. And an acid aqueous solution supply unit 35 for supplying an acid aqueous solution such as a nitric acid aqueous solution, a hydrofluoric acid aqueous solution, and a hydrogen peroxide solution.

  A spindle mechanism (not shown) that rotates the silicon wafer 40 is connected to the polishing head 31. Further, a spindle mechanism (not shown) for rotating the polishing pad 32 is connected to the rotating plate 33. As a result, since the back surface of the silicon wafer 40 and the polishing pad 32 face each other through the slurry, uniform polishing (or grinding) is performed.

  When the grinder device 30 having such a configuration is used, after the polishing (or grinding) is finished, the supply of the slurry from the slurry supply unit 34 is stopped, and instead, the acid aqueous solution is supplied from the acid aqueous solution supply unit 35 do it. At this time, it is desirable to continue the rotation of the silicon wafer 40 and the polishing pad 32. Thereby, it becomes possible to remove heavy metals continuously after polishing (or grinding). It is not essential to supply the acid aqueous solution after the slurry supply is stopped, and the slurry and the acid aqueous solution may be supplied simultaneously. According to this, it becomes possible to remove heavy metals simultaneously with polishing (or grinding).

  As described above, according to the present embodiment, the heavy metal is sucked out of the silicon wafer by using the acid aqueous solution, so that the mechanical strength of the semiconductor device 10 whose back surface is mirror-polished is ensured, and the device region It becomes possible to prevent contamination.

  The preferred embodiments of the present invention have been described above, but the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. Needless to say, it is included in the range.

[Comparative Example 1]
A plurality of boron-doped CZ wafers having a diameter of 100 mm, a thickness of 525 μm, an initial oxygen concentration of 1.6 × 10 ¹⁸ atoms / cm ³ and a specific resistance of 10 Ω · cm were prepared. With the back grind protective tape attached to the surface of these wafers, the back surface of the wafer was ground to reduce the thickness to 200 μm. Next, the back surface of the wafer was polished by 3 μm with a CMP apparatus and finished with a mirror finish.
Next, the sample was taken out from the CMP apparatus, the back grind protective tape was removed, and then washed with pure water. Thereafter, a mixed solution of HF and HNO ₃ was dropped onto the back surface of this sample, and the mixed solution was recovered after etching silicon to a depth of 1 μm from the back surface. The Cu contamination concentration contained in this recovered liquid was measured by an atomic absorption method. As a result, the Cu concentration in the collected mixed solution was 3.5 × 10 ¹⁰ atoms / cm ² .

[Example 1]
Three samples were fabricated that were back-finished like the silicon wafer used in the comparative example. Next, the sample is moved into the washing tub with the bag-lined tape attached, and 3% nitric acid aqueous solution of 0.1%, 5% and 20% concentration heated to 70 ° C is contacted with the back surface for 3 minutes. Then, the Cu contamination concentration was measured in the same manner as in the comparative example. As a result, the Cu concentration in the collected mixed solution was less than 1 × 10 ¹⁰ atoms / cm ² .

[Example 2]
In the same manner as in Example 1, three samples were contacted with 5% nitric acid aqueous solution for 3 minutes, 5 minutes, 10 minutes, and 30 minutes, and then the Cu contamination concentration was measured in the same manner as in the comparative example. As a result, the Cu concentration in the collected mixed solution was less than 1 × 10 ¹⁰ atoms / cm ² .

[Example 3]
Three samples were fabricated that were back-finished like the silicon wafer used in the comparative example. Next, the sample was moved into the washing tub with the bag-lined tape attached, and three levels of 0.1%, 5%, 10% concentration hydrofluoric acid aqueous solution heated to 70 ° C. were applied to the processed surface for 3 minutes. After pouring, the Cu contamination concentration was measured in the same manner as in the comparative example. As a result, the Cu concentration in the collected mixed solution was less than 1 × 10 ¹⁰ atoms / cm ² .

[Example 4]
As in the comparative example, after polishing the back surface of the wafer by 3 μm with a CMP apparatus, the supply of the slurry liquid was stopped, pure water was allowed to flow for 1 minute while the plate was kept rotating, and further heated to 50 ° C. at 1% concentration. Hydrogen water was allowed to flow for 2 minutes. Further, washing was performed with pure water. Thereafter, the Cu contamination concentration was measured in the same manner as in the comparative example. As a result, the Cu concentration in the collected mixed solution was less than 1 × 10 ¹⁰ atoms / cm ² .

[Example 5]
As in the comparative example, after processing the back surface with a CMP apparatus with the back grind protective tape applied, 70 ° C. pure water was brought into contact with the back surface processed surface for 3 minutes, and then the Cu concentration was adjusted in the same manner as in comparative example 1. It was measured. As a result, Cu concentration of the recovered mixed solution was ^{1.2 × 10 10 atoms / cm 2} .

DESCRIPTION OF SYMBOLS 10 Semiconductor device 11 Silicon substrate 11a Silicon substrate surface 11b Silicon substrate back surface 12 Device region 13 Epitaxial film 20 MCP
21 Package substrate 22 Adhesive 23 Bonding wire 24 External electrode 25 Sealing resin 30 Grinder device 31 Polishing head (grinding head)
32 Polishing pad (grinding pad)
33 Rotating plate 34 Slurry supply unit 35 Acid aqueous solution supply unit 40 Silicon wafer

Claims (7)

Removing a part of the silicon substrate on which the semiconductor element is formed on the front surface from the back side, thereby reducing the thickness of the silicon substrate to 100 μm or less;
A back surface polishing step for polishing the back surface of the thinned silicon substrate;
A heavy metal removal step of contacting at least the back surface of the silicon substrate with an acid aqueous solution or warm water simultaneously with the thinning step or the back surface polishing step or after the back surface polishing step is completed. Method.   2. The method of manufacturing a semiconductor device according to claim 1, wherein the acid aqueous solution is a nitric acid aqueous solution, a hydrofluoric acid aqueous solution, or a hydrogen peroxide solution.   3. The method of manufacturing a semiconductor device according to claim 1, wherein the temperature of the acid aqueous solution in the heavy metal removing step is not less than room temperature and not more than 100 ° C. 3.   4. The method for manufacturing a semiconductor device according to claim 1, wherein a contact time between the back surface of the silicon substrate and the aqueous acid solution in the heavy metal removing step is 5 minutes or less. 5.   5. The heavy metal removing step is performed by supplying the acid aqueous solution instead of the slurry after stopping the supply of the slurry used in the thinning step or the back surface polishing step. The manufacturing method of the semiconductor device as described in any one.   6. The method according to claim 1, wherein at least the thinning step, the back surface polishing step, and the heavy metal removal step are performed in a state where a back grind protective tape is attached to a surface of the silicon substrate. The manufacturing method of the semiconductor device of description.   A grinder device for grinding or polishing a back surface of a silicon wafer, comprising: a pad facing the back surface of the silicon wafer; and a supply unit for supplying an acid aqueous solution to the back surface of the silicon wafer.

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