Semiconductor device and method for manufacturing semiconductor device

Abstract

A semiconductor device (1) includes a semiconductor substrate (10) having a surface (10a) and a back surface (10b), a surface electrode (20) disposed on the surface (10a) of the semiconductor substrate (10), and a back surface electrode (30) disposed on the back surface (10b) of the semiconductor substrate (10). The back surface electrode (30) includes a first electrode (31) and a second electrode (32). The first electrode (31) is disposed on the second electrode (32) and includes a molybdenum oxide layer (31a) containing molybdenum oxide. The second electrode (32) includes a nickel layer (32a) containing nickel. The molybdenum oxide layer (31a) is disposed on the outermost layer of the back surface electrode (30) on the side opposite to the semiconductor substrate (10) with respect to the nickel layer (32a).

Description

Technical Field

[0001] This disclosure relates to a semiconductor device and a method for manufacturing a semiconductor device. Background Technology

[0002] In the semiconductor device described in Japanese Patent Application Publication No. 57-54364, a molybdenum thin film is provided on the surface electrode of the high-frequency transistor.

[0003] The semiconductor device described in the aforementioned announcement is a high-frequency horizontal transistor. Therefore, the aforementioned announcement does not contain any description of the back electrode of the semiconductor device. Therefore, the aforementioned announcement does not address the issue of achieving a good electrical connection between the back electrode and the solder. Summary of the Invention

[0004] This disclosure was made in view of the above-mentioned problems, and its object is to provide a semiconductor device and a method for manufacturing the same, which can achieve good electrical bonding between the back electrode and the solder.

[0005] A semiconductor device includes a semiconductor substrate having a surface and a back side, a surface electrode disposed on the surface of the semiconductor substrate, and a back electrode disposed on the back side of the semiconductor substrate. The back electrode includes a first electrode and a second electrode. The first electrode is disposed on the second electrode and includes a molybdenum oxide layer containing molybdenum oxide. The second electrode includes a nickel layer containing nickel. The molybdenum oxide layer is disposed on the outermost layer of the back electrode on the opposite side of the semiconductor substrate from the nickel layer.

[0006] According to the semiconductor device disclosed herein, a good electrical connection can be achieved between the back electrode and the solder.

[0007] The above and other objects, features, aspects and advantages of the invention will become clear from the following detailed description of the invention, which can be understood with reference to the accompanying drawings. Attached Figure Description

[0008] Figure 1 This is a cross-sectional view schematically illustrating the structure of the semiconductor device involved in Embodiment 1.

[0009] Figure 2 This is a flowchart illustrating a method for manufacturing a semiconductor device according to Embodiment 1.

[0010] Figure 3 This is a cross-sectional view schematically illustrating the structure of the semiconductor device involved in Embodiment 2.

[0011] Figure 4 This is a flowchart illustrating a method for manufacturing a semiconductor device according to Embodiment 2.

[0012] Figure 5This is a cross-sectional view schematically illustrating the structure of a modified example of the semiconductor device according to Embodiment 2.

[0013] Figure 6 This is a cross-sectional view schematically illustrating the structure of the semiconductor device involved in Embodiment 3.

[0014] Figure 7 This is a flowchart illustrating a method for manufacturing a semiconductor device according to Embodiment 3.

[0015] Figure 8 This is a cross-sectional view schematically illustrating the structure of the semiconductor device involved in Embodiment 4.

[0016] Figure 9 This is a flowchart illustrating a method for manufacturing a semiconductor device according to Embodiment 4.

[0017] Figure 10 This is a cross-sectional view schematically illustrating the structure of a modified example of the semiconductor device according to Embodiment 4.

[0018] Figure 11 This is a flowchart illustrating a method for manufacturing a semiconductor device according to Embodiment 5.

[0019] Figure 12 This is a cross-sectional view showing the state of picking up the chip during the chip mounting process of the semiconductor device manufacturing method according to Embodiment 5.

[0020] Figure 13 This is a cross-sectional view showing the operation of the chip mounting apparatus in the chip mounting process of the semiconductor device manufacturing method according to Embodiment 5.

[0021] Figure 14 This is a cross-sectional view showing the state after the molybdenum oxide layer has been removed during the cleaning process of the semiconductor device manufacturing method according to Embodiment 5.

[0022] Figure 15 This is a cross-sectional view showing the operation of the cleaning apparatus in the cleaning process of the semiconductor device manufacturing method according to Embodiment 5.

[0023] Figure 16 This is a cross-sectional view showing the operation of other cleaning devices in the cleaning process of the semiconductor device manufacturing method according to Embodiment 5.

[0024] Figure 17 This is a cross-sectional view showing the state of the semiconductor device after cleaning in the cleaning process of the semiconductor device manufacturing method according to Embodiment 5.

[0025] Figure 18This is a top view showing the state of the semiconductor device after cleaning in the cleaning process of the semiconductor device manufacturing method according to Embodiment 5.

[0026] Figure 19 This is a cross-sectional view showing the chip bonding process of the semiconductor device manufacturing method according to Embodiment 5. Detailed Implementation

[0027] The embodiments will now be described with reference to the accompanying drawings. Furthermore, identical or equivalent parts will be labeled with the same reference numerals and will not be described repeatedly.

[0028] Implementation method 1.

[0029] Reference Figure 1 The structure of the semiconductor device 1 according to Embodiment 1 will be described.

[0030] like Figure 1 As shown, the semiconductor device 1 according to Embodiment 1 includes a semiconductor substrate 10, a surface electrode 20, and a back electrode 30. The semiconductor substrate 10 has a surface 10a and a back surface 10b. The surface electrode 20 is disposed on the surface 10a of the semiconductor substrate 10. The back electrode 30 is disposed on the back surface 10b of the semiconductor substrate 10. The back electrode 30 is disposed on the side of the semiconductor substrate 10 opposite to the surface electrode 20.

[0031] The semiconductor substrate 10 is a Si substrate or a SiC substrate. The layer on the main surface (back side) of the back electrode 30 formed in the semiconductor substrate 10 is an n-type semiconductor layer when the semiconductor device 1 is a diode or a MOSFET (Metal Oxide Semiconductor Field Effect Transistor), and a p-type semiconductor layer when it is an IGBT (Insulated Gate Bipolar Transistor).

[0032] The back electrode 30 comprises multiple metal layers. The back electrode 30 includes a first electrode 31 and a second electrode 32. The first electrode 31 is disposed on the second electrode 32. The first electrode 31 includes a molybdenum oxide layer 31a containing molybdenum oxide. In this embodiment, the first electrode 31 is a molybdenum oxide layer 31a. The second electrode 32 includes a nickel layer 32a containing nickel (Ni). In this embodiment, the second electrode 32 is a nickel layer 32a. The molybdenum oxide layer 31a is disposed on the outermost layer of the back electrode 30 on the side opposite to the semiconductor substrate 10, relative to the nickel layer 32a. In this embodiment, the molybdenum oxide layer 31a is conductive. In this embodiment, to achieve water solubility as described later, molybdenum oxide (Mo... 100-x Ox The oxygen (O) content x contained in the product is preferably 0.1 mol% or more, more preferably 0.5 mol% or more. Furthermore, for electrical conductivity, it is preferably 75 mol% or less, more preferably 66.7 mol% or less.

[0033] In this embodiment, the back electrode 30 includes a third electrode 33 and a fourth electrode 34. The back electrode 30 is stacked from the semiconductor substrate 10 in the order of fourth electrode 34, third electrode 33, second electrode 32, and first electrode 31. The second electrode 32 is disposed on the third electrode 33. The third electrode 33 is disposed on the fourth electrode 34. The fourth electrode 34 is disposed on the back side 10b of the semiconductor substrate 10. The third electrode 33 includes a titanium layer 33a containing titanium (Ti) or a titanium alloy. In this embodiment, the third electrode 33 is a titanium layer 33a. The fourth electrode 34 includes an aluminum layer 34a containing aluminum (Al) or an aluminum alloy. In this embodiment, the fourth electrode 34 is an aluminum layer 34a. The titanium layer 33a is disposed on the aluminum layer 34a.

[0034] Reference Figure 1 and Figure 2 The manufacturing method of the semiconductor device 1 according to Embodiment 1 will be described.

[0035] like Figure 1 and Figure 2 As shown, the manufacturing method of the semiconductor device 1 according to Embodiment 1 includes a process S1 of preparing a semiconductor substrate 10, a process S2 of forming a surface electrode 20, and a process S3 of forming a back electrode 30.

[0036] Furthermore, between the step S2 of forming the surface electrode 20 and the step S3 of forming the back electrode 30, a step for processing the back side of the semiconductor substrate 10 may be provided. For example, the thickness of the semiconductor substrate 10 may be reduced, or a P-type semiconductor layer or an N-type semiconductor layer may be locally formed on the semiconductor substrate 10.

[0037] In step S1 of preparing the semiconductor substrate 10, a semiconductor substrate 10 having a surface 10a and a back surface 10b is prepared. In step S2 of forming the surface electrode 20, the surface electrode 20 is formed on the surface 10a of the semiconductor substrate 10. In step S3 of forming the back surface electrode 30, the back surface electrode 30 is formed on the back surface 10b of the semiconductor substrate 10.

[0038] The process S3 for forming the back electrode 30 includes a process S31 for forming a nickel layer 32a containing nickel and a process S32 for forming a molybdenum oxide layer 31a containing molybdenum oxide. The process S32 for forming the molybdenum oxide layer 31a is performed after the nickel layer 32a formation process S31. The molybdenum oxide layer 31a is formed on the outermost layer of the back electrode 30. In this embodiment, the molybdenum oxide layer 31a is formed on the nickel layer 32a.

[0039] In this embodiment, the process S3 for forming the back electrode 30 includes a process S33 of forming an aluminum layer 34a comprising aluminum or an aluminum alloy on the back side 10b of the semiconductor substrate 10, and a process S34 of forming a titanium layer 33a comprising titanium or a titanium alloy on the aluminum layer 34a. A nickel layer 32a is formed on the titanium layer 33a.

[0040] In the process of forming the back electrode 30, the molybdenum oxide layer 31a is formed, for example, with a thickness of 100 nm or less. The molybdenum oxide layer 31a is preferably formed with a thickness of 10 nm or more and 50 nm or less.

[0041] In step S3, which forms the back electrode 30, the molybdenum oxide layer 31a is formed by reactive sputtering, which uses a mixture of argon and oxygen as the film-forming gas. In reactive sputtering, a molybdenum or molybdenum alloy target is used. The molybdenum alloy target may contain nickel (Ni), niobium (Nb), or titanium (Ti).

[0042] In step S3, which forms the back electrode 30, the nickel layer 32a is formed by sputtering using argon gas as the film-forming gas. A nickel or nickel alloy target is used in the sputtering process.

[0043] Next, the effects of Implementation Method 1 will be explained.

[0044] For example, as comparative examples, Patent Document 2 (Japanese Patent Application Publication No. Hei 6-77262) and Patent Document 3 (Japanese Patent Application Publication No. 2011-233643) form an Au electrode on the surface of a Ni electrode, which has the function of preventing oxidation of the Ni electrode. However, due to increased demand in recent years, Au has become very expensive (high cost). Furthermore, in Patent Document 4 (Japanese Patent Application Publication No. 2007-63042), a Pd / Au electrode is formed on the surface of a Ni electrode, which, like the case of forming only an Au electrode, has the function of preventing oxidation of the Ni electrode. However, compared to the case of using only an Au electrode, it reduces the amount of Au used, but still consumes Au, resulting in high cost. Moreover, although Pd is offset from Au, its price is still relatively high.

[0045] According to the semiconductor device 1 of Embodiment 1, a molybdenum oxide layer 31a is disposed on the outermost layer of the back electrode 30 on the side opposite to the semiconductor substrate 10, relative to the nickel layer 32a. Therefore, the formation of nickel oxide on the surface of the nickel layer 32a can be suppressed. Thus, by forming nickel oxide on the surface of the nickel layer 32a, the deterioration of solder wettability during soldering of the back electrode 30 can be suppressed. Therefore, when the back electrode 30 is being soldered, a good electrical bond can be achieved between the back electrode 30 and the solder. Furthermore, molybdenum oxide is water-soluble, therefore, it does not need to be removed by wet etching using acidic or alkaline solutions. Therefore, the molybdenum oxide layer 31a can be easily removed, and good soldering can be performed on the surface of the nickel layer 32a where molybdenum oxide formation is suppressed.

[0046] According to the semiconductor device 1 of Embodiment 1, the third electrode 33 includes a titanium layer 33a containing titanium or a titanium alloy. The fourth electrode 34 includes an aluminum layer 34a containing aluminum or an aluminum alloy. Therefore, the back electrode 30 does not use gold, thus reducing the cost of the semiconductor device 1 compared to the case where the back electrode 30 uses gold.

[0047] Furthermore, the molybdenum oxide layer 31a, nickel layer 32a, titanium layer 33a, and aluminum layer 34a can be manufactured using the same manufacturing apparatus. This improves the productivity of the semiconductor device 1.

[0048] According to the manufacturing method of the semiconductor device 1 according to Embodiment 1, in step S3 of forming the back electrode 30, a molybdenum oxide layer 31a is formed on the outermost layer of the back electrode 30. Therefore, the formation of nickel oxide on the surface of the nickel layer 32a can be suppressed. Thus, by forming nickel oxide on the surface of the nickel layer 32a, the deterioration of solder wettability during soldering of the back electrode 30 can be suppressed. Therefore, when the back electrode 30 is soldered, a good electrical bond can be formed between the back electrode 30 and the solder. Furthermore, molybdenum oxide is water-soluble, so it does not need to be removed by wet etching using acidic or alkaline solutions. Therefore, for example, the molybdenum oxide layer 31a can be easily removed by a water washing process using pure water. Furthermore, even if the molybdenum oxide layer 31a remains, by forming the film thickness of the molybdenum oxide layer 31a to be less than 100 nm, the molybdenum oxide layer 31a can be absorbed by the solder, so a good soldering can be performed on the surface of the nickel layer 32a.

[0049] According to the manufacturing method of the semiconductor device 1 according to Embodiment 1, the step S3 of forming the back electrode 30 includes a step S33 of forming an aluminum layer 34a comprising aluminum or an aluminum alloy on the back side 10b of the semiconductor substrate 10, and a step S34 of forming a titanium layer 33a comprising titanium or a titanium alloy on the aluminum layer 34a. Therefore, the back electrode 30 does not use gold, thus reducing the cost of the semiconductor device 1 compared to the case where the back electrode 30 uses gold. Furthermore, the molybdenum oxide layer 31a, nickel layer 32a, titanium layer 33a, and aluminum layer 34a can be manufactured using the same manufacturing apparatus. This improves the productivity of the semiconductor device 1.

[0050] Implementation method 2.

[0051] Unless otherwise specified, Embodiment 2 has the same structure, manufacturing method, and effects as Embodiment 1 described above. Therefore, structures identical to those in Embodiment 1 are labeled with the same reference numerals and will not be described again.

[0052] Reference Figure 3 The structure of the semiconductor device 1 according to Embodiment 2 will be described.

[0053] like Figure 3 As shown, in the semiconductor device 1 according to Embodiment 2, the first electrode 31 includes a molybdenum layer 31b containing molybdenum (Mo). A molybdenum oxide layer 31a is disposed on the molybdenum layer 31b. The molybdenum layer 31b is disposed on a nickel layer 32a.

[0054] Reference Figure 3 and Figure 4 The manufacturing method of the semiconductor device 1 according to Embodiment 2 will be described.

[0055] like Figure 3 and Figure 4 As shown, in the manufacturing method of the semiconductor device 1 according to Embodiment 2, step S3 for forming the back electrode 30 includes step S35 for forming a molybdenum layer 31b containing molybdenum on the nickel layer 32a. After step S31 for forming the nickel layer 32a, step S35 for forming the molybdenum layer 31b is performed. After step S35 for forming the molybdenum layer 31b, step S32 for forming a molybdenum oxide layer 31a is performed. The molybdenum oxide layer 31a is formed on the molybdenum layer 31b.

[0056] Here, the thickness of the molybdenum layer 31b is preferably 20 nm or more and 500 nm or less. When the thickness of the molybdenum layer 31b is thinner than 20 nm, it is not possible to fully exert its function of preventing surface oxidation of the nickel layer 32a. Furthermore, when the thickness of the molybdenum layer 31b is thicker than 500 nm, it is difficult to manufacture the semiconductor device 1 at low cost.

[0057] In step S3, which forms the back electrode 30, the molybdenum layer 31b is formed by sputtering using argon as the film-forming gas. The molybdenum oxide layer 31a is formed by reactive sputtering using a mixture of argon and oxygen as the film-forming gas.

[0058] Reference Figure 5 The structure of a modified example of the semiconductor device 1 according to Embodiment 2 will be described.

[0059] like Figure 5 As shown, in a modified example of the semiconductor device 1 according to Embodiment 2, the molybdenum layer 31b is formed in an island shape. A molybdenum oxide layer 31a is formed on the island-shaped molybdenum layer 31b. The molybdenum oxide layer 31a is formed to fill the gaps between the island-shaped molybdenum layers 31b.

[0060] Next, the effects of Implementation Method 2 will be explained.

[0061] According to the semiconductor device 1 of Embodiment 2, a molybdenum oxide layer 31a is disposed on a molybdenum layer 31b. The molybdenum layer 31b is disposed on a nickel layer 32a. Therefore, the molybdenum layer 31b can suppress the formation of nickel oxide on the surface of the nickel layer 32a due to oxygen contained in the reactive sputtering gas during the film formation of the molybdenum oxide layer 31a. Therefore, when the back electrode 30 is soldered, a good electrical bond can be achieved between the back electrode 30 and the solder.

[0062] According to the manufacturing method of the semiconductor device 1 according to Embodiment 2, in step S3 of forming the back electrode 30, a molybdenum layer 31b is formed on the nickel layer 32a. A molybdenum oxide layer 31a is formed on the molybdenum layer 31b. Therefore, the molybdenum layer 31b suppresses the formation of nickel oxide on the surface of the nickel layer 32a due to oxygen contained in the reactive sputtering gas during the film formation of the molybdenum oxide layer 31a. Therefore, when the back electrode 30 is soldered, good electrical bonding can be achieved between the back electrode 30 and the solder. Furthermore, since the molybdenum oxide 31a is formed on the molybdenum layer 31b, the formation of the molybdenum oxide layer 31a becomes easier.

[0063] According to the manufacturing method of the semiconductor device 1 according to Embodiment 2, the molybdenum layer 31b is formed by sputtering using a molybdenum or molybdenum alloy target, wherein argon gas is used as the film-forming gas. The molybdenum oxide layer 31a is formed by reactive sputtering using the same molybdenum or molybdenum alloy target, wherein a gas containing a mixture of argon and oxygen is used as the film-forming gas. Therefore, by using sputtering and reactive sputtering, the molybdenum layer 31b and the molybdenum oxide layer 31a can be formed at high speed. Therefore, the productivity of the semiconductor device 1 can be improved.

[0064] Implementation method 3.

[0065] Unless otherwise specified, Embodiment 3 has the same structure, manufacturing method, and effects as Embodiment 1 described above. Therefore, structures identical to those in Embodiment 1 are labeled with the same reference numerals and will not be described again.

[0066] Reference Figure 6 The structure of the semiconductor device 1 according to Embodiment 3 will be described.

[0067] like Figure 6 As shown, in the semiconductor device 1 according to Embodiment 3, the second electrode 32 includes a nickel nitride layer 32b containing nickel nitride. The nickel nitride layer 32b is disposed on the nickel layer 32a. The molybdenum oxide layer 31a is disposed on the nickel nitride layer 32b. In this embodiment, in order to have oxidation resistance as described later, nickel oxide (Ni 100-y N y The nitrogen (N) content y contained in the product is preferably 0.1 mol% or more, more preferably 0.5 mol% or more. Furthermore, for electrical conductivity, it is preferably 55 mol% or less, more preferably 40 mol% or less.

[0068] Reference Figure 6 and Figure 7 The manufacturing method of the semiconductor device 1 according to Embodiment 3 will be described.

[0069] like Figure 6 and Figure 7 As shown, in the manufacturing method of the semiconductor device 1 according to Embodiment 3, step S3 for forming the back electrode 30 includes step S36 for forming a nickel nitride layer 32b containing nickel nitride on a nickel layer 32a. Step S36 for forming the nickel nitride layer 32b is performed after step S31 for forming the nickel layer 32a. Step S32 for forming the molybdenum oxide layer 31a is performed after step S36 for forming the nickel nitride layer 32b. The molybdenum oxide layer 31a is formed on the nickel nitride layer 32b.

[0070] In the process of forming the back electrode 30, the nickel nitride layer 32b is formed, for example, with a thickness of 100 nm or less. Preferably, the nickel nitride layer 32b is formed with a thickness of 10 nm or more and 30 nm or less.

[0071] In step S3, which forms the back electrode 30, the nickel layer 32a is formed by sputtering using argon as the film-forming gas. The nickel nitride layer 32b is formed by reactive sputtering using a mixture of argon and nitrogen as the film-forming gas. Both the sputtering and reactive sputtering methods use a nickel or nickel alloy target.

[0072] Next, the effects of implementation method 3 will be explained.

[0073] According to the semiconductor device 1 of Embodiment 3, a nickel nitride layer 32b is disposed on a nickel layer 32a. Therefore, the nickel nitride layer 32b suppresses the formation of nickel oxide (which has oxidation resistance) on the surface of the nickel layer 32a due to oxygen contained in the reactive sputtering gas during the deposition of the molybdenum oxide layer 31a. Therefore, when the back electrode 30 is soldered, a good electrical bond can be achieved between the back electrode 30 and the solder. Furthermore, the nickel nitride layer 32b improves oxidation resistance and chemical resistance, thereby enhancing the reliability of the semiconductor device 1.

[0074] According to the manufacturing method of the semiconductor device 1 according to Embodiment 3, in step S3 of forming the back electrode 30, a nickel nitride layer 32b is formed on the nickel layer 32a. A molybdenum oxide layer 31a is formed on the nickel nitride layer 32b. Therefore, the nickel nitride layer 32b can suppress the formation of nickel oxide on the surface of the nickel layer 32a due to oxygen contained in the reactive sputtering gas during the deposition of the molybdenum oxide layer 31a. Therefore, when the back electrode 30 is soldered, good electrical bonding can be achieved between the back electrode 30 and the solder. Furthermore, since the nickel nitride layer 32b is formed on the nickel layer 32a, its formation becomes easier.

[0075] According to the manufacturing method of the semiconductor device 1 according to Embodiment 3, the nickel layer 32a is formed using a nickel or nickel alloy target by sputtering, which uses argon gas as the film-forming gas. The nickel nitride layer 32b is formed using the same nickel or nickel alloy target by reactive sputtering, which uses a gas composed of a mixture of argon and nitrogen as the film-forming gas. Therefore, the nickel layer 32a and the nickel nitride layer 32b can be formed at high speed. Therefore, the productivity of the semiconductor device 1 can be improved.

[0076] Implementation method 4.

[0077] Unless otherwise specified, Embodiment 4 has the same structure, manufacturing method, and effects as Embodiments 1 to 3 described above. Therefore, structures identical to those in Embodiment 1 are labeled with the same reference numerals and will not be described again.

[0078] Reference Figure 8 The structure of the semiconductor device 1 according to Embodiment 4 will be described.

[0079] like Figure 8 As shown, in the semiconductor device 1 according to Embodiment 4, the first electrode 31 includes a molybdenum layer 31b containing molybdenum. A molybdenum oxide layer 31a is disposed on the molybdenum layer 31b. The second electrode 32 includes a nickel nitride layer 32b containing nickel nitride. The nickel nitride layer 32b is disposed on the nickel layer 32a. The molybdenum layer 31b is disposed on the nickel nitride layer 32b. The molybdenum oxide layer 31a is disposed on the nickel nitride layer 32b.

[0080] Reference Figure 8 and Figure 9 The manufacturing method of the semiconductor device 1 according to Embodiment 4 will be described.

[0081] like Figure 8 and Figure 9 As shown, in the manufacturing method of the semiconductor device 1 according to Embodiment 4, step S3 for forming the back electrode 30 includes step S36 of forming a nickel nitride layer 32b containing nickel nitride on a nickel layer 32a, and step S35 of forming a molybdenum layer 31b containing molybdenum on the nickel nitride layer 32b. Step S36 for forming the nickel nitride layer 32b is performed after step S31 for forming the nickel layer 32a. Step S35 for forming the molybdenum layer 31b is performed after step S36 for forming the nickel nitride layer 32b. Step S32 for forming the molybdenum oxide layer 31a is performed after step S35 for forming the molybdenum oxide layer 31a. The molybdenum oxide layer 31a is formed on the molybdenum layer 31b. The molybdenum layer 31b is disposed on the nickel nitride layer 32b.

[0082] Reference Figure 10 The structure of a modified example of the semiconductor device 1 according to Embodiment 4 will be described.

[0083] like Figure 10 As shown, in a modified example of the semiconductor device 1 according to Embodiment 4, the molybdenum layer 31b is formed in an island shape. A molybdenum oxide layer 31a is formed on the island-shaped molybdenum layer 31b. The molybdenum oxide layer 31a is formed to fill the gaps between the island-shaped molybdenum layers 31b.

[0084] Next, the effects of implementation method 4 will be explained.

[0085] According to the semiconductor device 1 of Embodiment 4, a molybdenum oxide layer 31a is disposed on a molybdenum layer 31b. A nickel nitride layer 32b is disposed on a nickel layer 32a. The molybdenum layer 31b is disposed on the nickel nitride layer 32b. Therefore, the formation of nickel oxide on the surface of the nickel layer 32a due to oxygen contained in the reactive sputtering gas during the deposition of the molybdenum oxide layer 31a can be suppressed. Therefore, when the back electrode 30 is soldered, a good electrical bond can be achieved between the back electrode 30 and the solder.

[0086] According to the manufacturing method of the semiconductor device 1 according to Embodiment 4, in the process of forming the back electrode 30, a nickel nitride layer 32b is formed on the nickel layer 32a. A molybdenum layer 31b is formed on the nickel nitride layer 32b. A molybdenum oxide layer 31a is formed on the molybdenum layer 31b. Therefore, by means of the molybdenum layer 31b and the nickel nitride layer 32b, the formation of nickel oxide on the surface of the nickel layer 32a due to oxygen contained in the reactive sputtering gas during the film formation of the molybdenum oxide layer 31a can be suppressed. Therefore, when the back electrode 30 is soldered, a good electrical bond can be achieved between the back electrode 30 and the solder. Furthermore, since the molybdenum oxide 31a is formed on the molybdenum layer 31b, the formation of the molybdenum oxide layer 31a becomes easier.

[0087] Implementation method 5.

[0088] Unless otherwise specified, Embodiment 5 has the same structure, manufacturing method, and effects as Embodiment 1 described above. Therefore, structures identical to those in Embodiment 1 are labeled with the same reference numerals and will not be described again.

[0089] Reference Figures 11-19 The manufacturing method of the semiconductor device 1 according to Embodiment 5 will be described.

[0090] like Figure 11 and Figure 19 As shown, the manufacturing method of the semiconductor device 1 according to Embodiment 4 further includes a step S4 of bonding to a circuit board 80. Step S4 of bonding to the circuit board 80 is performed after step S3 of forming the back electrode 30.

[0091] like Figure 11 As shown, there is a dicing process between the process S32 of forming oxide film layer 31a and the chip mounting process S41, in which the wafer is processed into a chip by dicing.

[0092] In step S4, the back electrode 30 is bonded to the circuit board 80 via solder 70. Step S4 includes a chip mounting step S41, a cleaning step S42, and a chip bonding step S43. The cleaning step S42 is performed after the chip mounting step S41. The chip bonding step S43 is performed after the cleaning step S42.

[0093] like Figure 12 As shown, in the manufacturing method of the semiconductor device 1 according to Embodiment 5, the semiconductor device 1 is picked up in the chip mounting step S41 of the step S4 of bonding the circuit board 70. If residual adhesive 41 of the cutting tape 40 is generated during picking, poor bonding will occur between the back electrode 30 and the solder.

[0094] like Figure 13As shown, in the chip mounting step S41 of the process S4 of bonding the circuit board 80, the chip mounting apparatus 50 has the function of rotating the semiconductor device 1 by 180° while holding the semiconductor device 1. The chip mounting apparatus 50 is configured to transfer the semiconductor device 1 to the next process while holding the semiconductor device 1.

[0095] like Figures 14-16 As shown, in the manufacturing method of the semiconductor device 1 according to Embodiment 5, in the cleaning step S42 of the process S4 of bonding the circuit substrate 80, at least a portion of the molybdenum oxide layer 31a of the back electrode 30 is removed. Figure 14 As shown, the entire molybdenum oxide layer 31a can be removed.

[0096] like Figure 15 As shown, the molybdenum oxide layer 31a is removed by a cleaning solution 61 provided by a cleaning apparatus 60. The cleaning apparatus 60 has a conveying mechanism that enables continuous cleaning while maintaining the semiconductor device 1. The cleaning apparatus 60 includes a water supply mechanism for supplying water to the cleaning solution 61 and a drainage mechanism for draining the cleaning solution 61. Furthermore, the cleaning apparatus 60 includes a drying mechanism comprising nitrogen purging, hot air, and rotation.

[0097] The cleaning solution 61 is a water-soluble cleaning solution. The hydrogen ion index of the water-soluble cleaning solution is preferably above pH 4 and below pH 6. Examples of water-soluble cleaning solutions include pure water, water-soluble flux, and reducing water (hydrogen water). With the back electrode 30 positioned on the upper side, the molybdenum oxide layer 31a can be removed by applying the cleaning solution 61 to the upper surface of the molybdenum oxide layer 31a of the back electrode 30.

[0098] like Figure 16 As shown, with the back electrode 30 positioned on the lower side, the molybdenum oxide layer 31a can be removed by providing cleaning fluid 61 to the lower surface of the molybdenum oxide layer 31a of the back electrode 30. The cleaning fluid 61 flows upward within the cleaning device 60 to supply water to the back electrode 30, and after cleaning, it flows downward within the cleaning device 60 to drain water.

[0099] like Figure 17 and Figure 18 As shown, a portion of the molybdenum oxide layer 31a may remain. The molybdenum oxide layer 31a may remain on the outer periphery of the back electrode 30. In addition, the molybdenum oxide layer 31a may remain at the four corners of the back electrode 30.

[0100] like Figure 19As shown, in the manufacturing method of the semiconductor device 1 according to Embodiment 5, in the chip bonding process S43 of the process S4 of bonding the circuit substrate 80, after at least a portion of the molybdenum oxide layer 31a of the back electrode 30 has been removed in the cleaning process S42, the back electrode 30 is bonded to the circuit substrate 80 via solder 70. A nickel solder mixture layer 71 is formed between the nickel layer 32a and the solder 70.

[0101] A power module is formed by sealing the semiconductor device 1 manufactured in this way with resin through housing-type or packaged wiring.

[0102] Next, the effects of implementation method 5 will be explained.

[0103] According to the manufacturing method of the semiconductor device 1 according to Embodiment 5, the back electrode 30 is bonded to the circuit board 80 via solder 70. Therefore, a semiconductor device 1 can be provided in which the back electrode 30 is bonded to the circuit board 80 via solder 70.

[0104] According to the manufacturing method of the semiconductor device 1 according to Embodiment 5, after at least a portion of the molybdenum oxide layer 31a of the back electrode 30 has been removed in the cleaning process S42, the back electrode 30 is bonded to the circuit board 80 via solder 70. Therefore, even if residual adhesive 41 of the cutting tape 40 is generated during pickup, the residual adhesive 41 can be removed together with the molybdenum oxide layer 31a. As a result, the occurrence of poor bonding between the back electrode 30 and the solder can be suppressed. Therefore, when the back electrode 30 is soldered, a good electrical bond can be achieved between the back electrode 30 and the solder.

[0105] According to the manufacturing method of the semiconductor device 1 according to Embodiment 5, by leaving a portion of the molybdenum oxide layer 31a, solder 70 can be prevented from creeping along the side of the semiconductor device 1. Furthermore, it facilitates the uniformization of the solder 70 thickness.

[0106] The above-described embodiments can be combined appropriately.

[0107] It should be understood that the embodiments disclosed herein are illustrative rather than restrictive in all respects. The scope of this disclosure is defined by the claims rather than the foregoing description and is intended to include all modifications with the same meaning and scope as the claims.

[0108] The various methods disclosed herein are summarized and recorded below as appendices.

[0109] (Note 1) A semiconductor device, comprising: A semiconductor substrate having a front and a back surface; Surface electrodes disposed on the surface of the semiconductor substrate; and A back electrode disposed on the back side of the semiconductor substrate. The back electrode includes a first electrode and a second electrode. The first electrode is disposed on the second electrode and includes a molybdenum oxide layer containing molybdenum oxide. The second electrode includes a nickel layer containing nickel. The molybdenum oxide layer is disposed on the outermost layer of the back electrode on the opposite side of the semiconductor substrate, relative to the nickel layer.

[0110] (Note 2) The semiconductor device as described in Note 1, The back electrode includes a third electrode and a fourth electrode. The second electrode is disposed on the third electrode. The third electrode is disposed on the fourth electrode. The third electrode includes a titanium layer containing titanium or a titanium alloy. The fourth electrode includes an aluminum layer containing aluminum or an aluminum alloy. The titanium layer is disposed on the aluminum layer.

[0111] (Note 3) Semiconductor devices as described in Note 1 or 2, The first electrode includes a molybdenum layer containing molybdenum. The molybdenum oxide layer is disposed on the molybdenum layer. The molybdenum layer is disposed on the nickel layer.

[0112] (Note 4) Semiconductor devices as described in Note 1 or 2, The second electrode includes a nickel nitride layer containing nickel nitride. The nickel nitride layer is disposed on the nickel layer.

[0113] (Note 5) The semiconductor device as described in Note 1, The first electrode includes a molybdenum layer containing molybdenum. The molybdenum oxide layer is disposed on the molybdenum layer. The second electrode includes a nickel nitride layer containing nickel nitride. The nickel nitride layer is disposed on the nickel layer. The molybdenum layer is disposed on the nickel nitride layer.

[0114] (Appendix 6) A method for manufacturing a semiconductor device, comprising: The process of preparing a semiconductor substrate having a front and a back surface; The process of forming surface electrodes on the surface of the semiconductor substrate; and The process of forming a back electrode on the back side of the semiconductor substrate. The process of forming the back electrode includes a process of forming a nickel layer containing nickel and a process of forming a molybdenum oxide layer containing molybdenum oxide. The molybdenum oxide layer is formed on the outermost layer of the back electrode.

[0115] (Note 7) The method for manufacturing a semiconductor device as described in Note 6, The process of forming the back electrode includes forming an aluminum layer containing aluminum or an aluminum alloy on the back side of the semiconductor substrate, and forming a titanium layer containing titanium or a titanium alloy on the aluminum layer. The nickel layer is formed on the titanium layer.

[0116] (Note 8) The method of manufacturing a semiconductor device as described in Note 6 or 7, The process of forming the back electrode includes the process of forming a molybdenum-containing layer on the nickel layer. The molybdenum oxide layer is formed on the molybdenum layer.

[0117] (Note 9) The method for manufacturing a semiconductor device as described in Note 8, In the process of forming the back electrode, the molybdenum layer is formed by reactive sputtering, which uses argon gas as the film-forming gas. The molybdenum oxide layer is formed by reactive sputtering, which uses a mixture of argon and oxygen as the film-forming gas.

[0118] (Note 10) The method of manufacturing a semiconductor device as described in Note 6 or 7, The process of forming the back electrode includes the process of forming a nickel nitride layer containing nickel nitride on the nickel layer. The molybdenum oxide layer is formed on the nickel nitride layer.

[0119] (Note 11) The method for manufacturing a semiconductor device as described in Note 10, In the process of forming the back electrode, the nickel layer is formed by reactive sputtering, which uses argon gas as the film-forming gas. The nickel nitride layer is formed by reactive sputtering, which uses a mixture of argon and nitrogen as the film-forming gas.

[0120] (Note 12) The method for manufacturing a semiconductor device as described in Note 6, The process of forming the back electrode includes the process of forming a nickel nitride layer containing nickel nitride on the nickel layer, and the process of forming a molybdenum layer containing molybdenum on the nickel nitride layer. The molybdenum oxide layer is formed on the molybdenum layer.

[0121] (Note 13) A method for manufacturing a semiconductor device as described in at least one of Notes 6 to 12, It also includes a process of bonding the back electrode to the circuit board via solder.

[0122] (Note 14) The method for manufacturing a semiconductor device as described in Note 13, The bonding process to the circuit board includes a cleaning process that removes at least a portion of the molybdenum oxide layer of the back electrode. During the cleaning process, with at least a portion of the molybdenum oxide layer on the back electrode removed, the back electrode is bonded to the circuit board via the solder.

[0123] While embodiments of the invention have been described, it should be considered that the embodiments disclosed herein are illustrative in all respects and not restrictive. The scope of the invention is to be defined by the claims, including all modifications within the same meaning and scope as the claims.

Claims

1. A semiconductor device, characterized in that, include: A semiconductor substrate having a front and a back surface; Surface electrodes disposed on the surface of the semiconductor substrate; as well as A back electrode disposed on the back side of the semiconductor substrate. The back electrode includes a first electrode and a second electrode. The first electrode is disposed on the second electrode and includes a molybdenum oxide layer containing molybdenum oxide. The second electrode includes a nickel layer containing nickel. The molybdenum oxide layer is disposed on the outermost layer of the back electrode on the opposite side of the semiconductor substrate, relative to the nickel layer.

2. The semiconductor device as claimed in claim 1, characterized in that, The back electrode includes a third electrode and a fourth electrode. The second electrode is disposed on the third electrode. The third electrode is disposed on the fourth electrode. The third electrode includes a titanium layer containing titanium or a titanium alloy. The fourth electrode includes an aluminum layer containing aluminum or an aluminum alloy. The titanium layer is disposed on the aluminum layer.

3. The semiconductor device as claimed in claim 1, characterized in that, The first electrode includes a molybdenum layer containing molybdenum. The molybdenum oxide layer is disposed on the molybdenum layer. The molybdenum layer is disposed on the nickel layer.

4. The semiconductor device as claimed in claim 1, characterized in that, The second electrode includes a nickel nitride layer containing nickel nitride. The nickel nitride layer is disposed on the nickel layer.

5. The semiconductor device as claimed in claim 1, characterized in that, The first electrode includes a molybdenum layer containing molybdenum. The molybdenum oxide layer is disposed on the molybdenum layer. The second electrode includes a nickel nitride layer containing nickel nitride. The nickel nitride layer is disposed on the nickel layer. The molybdenum layer is disposed on the nickel nitride layer.

6. A method for manufacturing a semiconductor device, characterized in that, include: The process of preparing a semiconductor substrate having a front and a back surface; The process of forming a surface electrode on the surface of the semiconductor substrate; as well as The process of forming a back electrode on the back side of the semiconductor substrate. The process of forming the back electrode includes a process of forming a nickel layer containing nickel and a process of forming a molybdenum oxide layer containing molybdenum oxide. The molybdenum oxide layer is formed on the outermost layer of the back electrode.

7. The method for manufacturing a semiconductor device as claimed in claim 6, characterized in that, The process of forming the back electrode includes forming an aluminum layer containing aluminum or an aluminum alloy on the back side of the semiconductor substrate, and forming a titanium layer containing titanium or a titanium alloy on the aluminum layer. The nickel layer is formed on the titanium layer.

8. The method for manufacturing a semiconductor device as claimed in claim 6, characterized in that, The process of forming the back electrode includes the process of forming a molybdenum-containing layer on the nickel layer. The molybdenum oxide layer is formed on the molybdenum layer.

9. The method for manufacturing a semiconductor device as claimed in claim 8, characterized in that, In the process of forming the back electrode, the molybdenum layer is formed by reactive sputtering, which uses argon gas as the film-forming gas. The molybdenum oxide layer is formed by reactive sputtering, which uses a mixture of argon and oxygen as the film-forming gas.

10. The method of manufacturing a semiconductor device as claimed in claim 6, characterized in that, The process of forming the back electrode includes the process of forming a nickel nitride layer containing nickel nitride on the nickel layer. The molybdenum oxide layer is formed on the nickel nitride layer.

11. The method of manufacturing a semiconductor device as claimed in claim 10, characterized in that, In the process of forming the back electrode, the nickel layer is formed by reactive sputtering, which uses argon gas as the film-forming gas. The nickel nitride layer is formed by reactive sputtering, which uses a mixture of argon and nitrogen as the film-forming gas.

12. The method for manufacturing a semiconductor device as claimed in claim 6, characterized in that, The process of forming the back electrode includes forming a nickel nitride layer containing nickel nitride on the nickel layer, and forming a molybdenum layer containing molybdenum on the nickel nitride layer. The molybdenum oxide layer is formed on the molybdenum layer.

13. The method for manufacturing a semiconductor device as claimed in claim 6, characterized in that, It also includes a process of bonding the back electrode to the circuit board via solder.

14. The method for manufacturing a semiconductor device as claimed in claim 13, characterized in that, The bonding process to the circuit board includes a cleaning process that removes at least a portion of the molybdenum oxide layer of the back electrode. During the cleaning process, with at least a portion of the molybdenum oxide layer on the back electrode removed, the back electrode is bonded to the circuit board via the solder.

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