Semiconductor element and method for manufacturing the same

Abstract

A semiconductor element and a manufacturing method thereof. A semiconductor element (100) has an electrode (30). The electrode has a copper electrode layer (38). The copper electrode layer contains an element that generates a compound having a higher vapor pressure than atmospheric pressure when combined with hydrogen. Therefore, hydrogen embrittlement of the copper electrode layer can be suppressed.

Description

Technical Field

[0001] The technology disclosed in this specification relates to semiconductor devices and their manufacturing methods. Background Technology

[0002] The semiconductor device in Patent Document 1 has electrodes. Typically, the electrodes of a semiconductor device are made of metals such as aluminum.

[0003] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 2025-025361 Summary of the Invention

[0004] In some semiconductor devices, the electrode layer is made of copper. Using a copper electrode layer as the electrode layer of a semiconductor device can improve the heat dissipation performance of the semiconductor device. The copper electrode layer contains trace amounts of oxides (e.g., copper oxide). Furthermore, when using a semiconductor device, hydrogen can penetrate the interior of the copper electrode layer. If hydrogen penetrates the interior of the copper electrode layer, the oxides react with the hydrogen to produce water. If the produced water turns into water vapor, its volume expansion creates voids within the copper electrode layer. This phenomenon is called hydrogen embrittlement. Hydrogen embrittlement can lead to problems such as reduced electrode strength and reduced thermal conductivity. This specification proposes a technique to suppress hydrogen embrittlement of the copper electrode layer.

[0005] The semiconductor device disclosed in this specification may have electrodes. The electrodes may have a copper electrode layer. The copper electrode layer may contain an element that, when combined with hydrogen, forms a compound with a vapor pressure higher than atmospheric pressure.

[0006] In the aforementioned semiconductor device, if hydrogen penetrates the copper electrode layer during use, it reacts with the elements contained in the copper electrode layer to form a compound. The vapor pressure of this compound is higher than atmospheric pressure, therefore it is a gas. Thus, even if a compound is formed, a phase transition from liquid to gas does not occur, and no volume expansion of the compound occurs. Furthermore, the reaction of the hydrogen penetrating the copper electrode layer with the aforementioned elements suppresses the reaction between the oxides contained within the copper electrode layer and the hydrogen. This suppresses water formation, preventing volume expansion due to water vaporization. Therefore, it is difficult to form pores within the copper electrode layer, thus suppressing hydrogen embrittlement of the copper electrode layer. Attached Figure Description

[0007] Figure 1 This is a schematic diagram of the semiconductor element according to the first embodiment.

[0008] Figure 2 yes Figure 1 A magnified stereoscopic view of the semiconductor element in region II.

[0009] Figure 3 This is an explanatory diagram of the manufacturing method of the semiconductor element according to the first embodiment.

[0010] Figure 4 This is an explanatory diagram of the manufacturing method of the semiconductor element according to the first embodiment.

[0011] Figure 5 This is an explanatory diagram of the manufacturing method of the semiconductor element according to the first embodiment.

[0012] Figure 6 This is an explanatory diagram of the manufacturing method of the semiconductor element according to the first embodiment.

[0013] Figure 7 This is an explanatory diagram of the manufacturing method of the semiconductor element according to the first embodiment.

[0014] Figure 8 This is an explanatory diagram of the manufacturing method of the semiconductor element according to the first embodiment.

[0015] Figure 9 This is an explanatory diagram of the manufacturing method of the semiconductor element according to the second embodiment. Detailed Implementation

[0016] In one example of a semiconductor element disclosed in this specification, the aforementioned element may be fluorine or chlorine.

[0017] Fluorine and chlorine combine with hydrogen to form compounds with vapor pressures higher than atmospheric pressure. Therefore, the presence of fluorine or chlorine in the copper electrode layer can suppress hydrogen embrittlement of the copper electrode layer.

[0018] In one example of the semiconductor device disclosed in this specification, the concentration of the above-mentioned element may be 1 × 10⁻⁶. 16 atoms / cm 3 above.

[0019] The semiconductor device disclosed in this specification may have a semiconductor substrate. The electrode may be connected to the semiconductor substrate. The copper electrode layer may have a main surface on the opposite side of the semiconductor substrate. The concentration of the element in the surface portion near the main surface may be higher than the concentration of the element in the portion deeper than the surface portion from the main surface.

[0020] According to this structure, when using semiconductor devices, elements readily react with hydrogen in the surface layer near the main surface. Therefore, in the copper electrode layer, it is possible to suppress the penetration of hydrogen into the portion deeper than the surface layer.

[0021] The semiconductor element disclosed in this specification may also have a polyimide film in contact with the copper electrode layer.

[0022] The polyimide film contains a large amount of hydrogen as an impurity. Based on this structure, hydrogen embrittlement of the copper electrode layer due to hydrogen generated from the polyimide film can be suppressed.

[0023] The semiconductor device manufacturing method disclosed in this specification may include the following steps: forming an electrode having a copper electrode layer on a semiconductor substrate; and exposing the copper electrode layer to CF4 gas while the copper electrode layer is exposed.

[0024] Based on this structure, a copper electrode layer containing fluorine can be formed. Therefore, hydrogen embrittlement of the copper electrode layer can be suppressed.

[0025] The semiconductor device manufacturing method disclosed in this specification includes the following steps: forming an electrode having a copper electrode layer on a semiconductor substrate; and exposing the copper electrode layer to BCl3 gas while the copper electrode layer is exposed.

[0026] Based on this structure, a copper electrode layer containing chlorine can be formed. Therefore, hydrogen embrittlement of the copper electrode layer can be suppressed.

[0027] (First Implementation) Figure 1 The semiconductor element 100 shown has a semiconductor substrate 10. The semiconductor substrate 10 is made of SiC. The semiconductor substrate 10 may also be made of other semiconductor materials such as silicon and gallium nitride. Hereinafter, the thickness direction of the semiconductor substrate 10 will be referred to as the z-direction, a direction parallel to the upper surface 10a of the semiconductor substrate 10 will be referred to as the x-direction, and a direction parallel to the upper surface 10a of the semiconductor substrate 10 and orthogonal to the x-direction will be referred to as the y-direction.

[0028] The semiconductor substrate 10 has a device region 102 and an outer peripheral region 104. A MOSFET (metal oxide semiconductor field effect transistor) is disposed in the device region 102. The outer peripheral region 104 is disposed between the outer peripheral surface 10c of the semiconductor substrate 10 and the device region 102.

[0029] Semiconductor device 100 has an interlayer insulating film 22. The interlayer insulating film 22 is in contact with the upper surface 10a of semiconductor substrate 10 in the region spanning device region 102 and peripheral region 104. Contact holes 24 are provided in the interlayer insulating film 22 within device region 102. Contact holes 26 are provided in the interlayer insulating film 22 within peripheral region 104. The interlayer insulating film 22 is made of highly fluid silicon oxide such as BPSG (Boron-phospho silicate glass).

[0030] Semiconductor device 100 has an upper electrode 30. The upper electrode 30 is disposed within device region 102. The upper electrode 30 is in contact with the upper surface 10a of semiconductor substrate 10 within a contact hole 24. The upper surface of an interlayer insulating film 22 covers the upper electrode 30 around the contact hole 24. Within the contact hole 24, the upper electrode 30 is in ohmic contact with semiconductor substrate 10. The upper electrode 30 has a silicide layer 32, a barrier metal layer 34, a seed layer 36, and a copper electrode layer 38.

[0031] like Figure 1 , Figure 2 As shown, a silicide layer 32 is disposed within the contact hole 24. The silicide layer 32 is composed of a silicide (e.g., titanium silicide). The silicide layer 32 covers the entire upper surface 10a of the semiconductor substrate 10 within the contact hole 24.

[0032] like Figure 1 , Figure 2 As shown, the barrier metal layer 34 has a first barrier metal layer 34a and a second barrier metal layer 34b. The first barrier metal layer 34a covers the entire upper surface of the silicide layer 32 within the contact hole 24. The first barrier metal layer 34a also covers the upper surface of the interlayer insulating film 22 surrounding the contact hole 24. The first barrier metal layer 34a is made of, for example, titanium. The second barrier metal layer 34b covers the entire surface of the first barrier metal layer 34a. The second barrier metal layer 34b is made of, for example, titanium nitride.

[0033] like Figure 1 , Figure 2 As shown, the seed layer 36 has a first seed layer 36a and a second seed layer 36b. The first seed layer 36a covers the entire surface of the second barrier metal layer 34b. The first seed layer 36a is made of, for example, titanium. The second seed layer 36b covers the entire surface of the first seed layer 36a. The second seed layer 36b is made of, for example, copper.

[0034] like Figure 1 , Figure 2 As shown, the copper electrode layer 38 covers the entire surface of the second seed layer 36b. The copper electrode layer 38 is disposed on top of the interlayer insulating film 22 surrounding the contact hole 24. The thickness of the copper electrode layer 38 (i.e., the dimension in the z-direction) is greater than the thickness of both the barrier metal layer 34 and the seed layer 36. The copper electrode layer 38 contains fluorine (i.e., F).

[0035] The upper surface 38u of the copper electrode layer 38 is the main surface located on the opposite side of the semiconductor substrate 10. The copper electrode layer 38 has a surface portion 38a located near the upper surface 38u, a side portion 38c located near the side portion 38s of the copper electrode layer 38, and a lower portion 38b.

[0036] The surface layer 38a is disposed within the area of ​​the upper surface 38u containing the copper electrode layer 38. For example, the thickness (i.e., the dimension in the z-direction) of the surface layer 38a is 60 nm. The surface layer 38a contains fluorine. The fluorine concentration of the surface layer 38a is, for example, 1 × 10⁻⁶. 16 atoms / cm 3 That's all. Additionally, the fluorine concentration in the surface layer 38a is, for example, 1 × 10⁻⁶. 21 atoms / cm 3 the following.

[0037] Side portion 38c is provided within the area of ​​side portion 38s containing copper electrode layer 38. The thickness (i.e., dimension in the x-direction) of side portion 38c is smaller than the thickness of surface portion 38a. Side portion 38c contains fluorine.

[0038] The lower layer 38b is located below the surface layer 38a (i.e., in a region deeper than the surface layer 38a) and is not exposed in the area of ​​the side layer 38s. The lower layer 38b has a lower fluorine concentration than the surface layer 38a and the side layer 38c. Therefore, the purity of copper in the lower layer 38b is higher than that in the surface layer 38a and the side layer 38c.

[0039] Semiconductor element 100 has signal electrode pads 50. The signal electrode pads 50 are disposed within an outer peripheral region 104. The signal electrode pads 50 are disposed within and around a contact hole 26. The signal electrode pads 50 have a polysilicon film 52, a barrier metal layer 54, a seed layer 56, and a copper electrode layer 58. The polysilicon film 52 covers the upper surface 10a of the semiconductor substrate 10 within the contact hole 26. The barrier metal layer 54 covers the entire upper surface of the polysilicon film 52. Additionally, the barrier metal layer 54 covers the upper surface of the interlayer insulating film 22 surrounding the contact hole 26. The barrier metal layer 54, seed layer 56, and copper electrode layer 58 each have the same structure as the barrier metal layer 34, seed layer 36, and copper electrode layer 38.

[0040] Semiconductor device 100 has a polyimide film 60. The polyimide film 60 is disposed in device region 102 and peripheral region 104. The polyimide film 60 covers the upper surface of interlayer insulating film 22. The polyimide film 60 is in contact with the side surfaces of upper electrode 30 and signal electrode pads 50. That is, the polyimide film 60 is in contact with the side surface 38s of copper electrode layer 38. The upper surface 38u of copper electrode layer 38 and the upper surface of copper electrode layer 58 are exposed from the polyimide film 60.

[0041] The semiconductor element 100 has a lower electrode 40. The lower electrode 40 is in contact with the entire area of ​​the lower surface 10b of the semiconductor substrate 10.

[0042] When using semiconductor element 100, signal terminals are connected to signal electrode pads 50, and signals are applied to signal electrode pads 50 via the signal terminals. Additionally, external terminals are connected to the upper electrode 30 (i.e., copper electrode layer 38), and other external terminals are connected to the lower electrode 40, with current flowing between the upper electrode 30 and the lower electrode 40. Furthermore, heat generated by semiconductor element 100 is dissipated to the outside via the upper electrode 30 and the lower electrode 40. That is, the upper electrode 30 and the lower electrode 40 also function as heat dissipation paths.

[0043] When using the semiconductor element 100, hydrogen released from the polyimide film 60 and hydrogen diffused from the atmosphere into the semiconductor element 100 may intrude into the copper electrode layer 38. Within the copper electrode layer 38, oxides (e.g., copper oxide) exist as impurities. If the copper electrode layer 38 does not contain fluorine, the copper oxide within the copper electrode layer 38 reacts with hydrogen to generate water within the copper electrode layer 38. When the generated water changes into water vapor, its volume expands, forming pores within the copper electrode layer 38. That is, hydrogen embrittlement occurs in the copper electrode layer 38. In contrast, in this embodiment, since the copper electrode layer 38 contains fluorine, the hydrogen intruding into the copper electrode layer 38 reacts with fluorine to generate hydrogen fluoride (i.e., HF). Hydrogen fluoride is a compound with a vapor pressure higher than atmospheric pressure and is a gas. Therefore, even if fluorine changes into hydrogen fluoride within the copper electrode layer 38, a phase transition from liquid to gas does not occur, and no volume expansion occurs. As a result, it is difficult for pores to form inside the copper electrode layer 38, and hydrogen embrittlement of the copper electrode layer 38 can be suppressed. In this embodiment, in particular, since fluorine is contained in the surface portion 38a and the side portion 38c of the copper electrode layer 38, the fluorine contained in the surface portion 38a and the side portion 38c reacts with the hydrogen that has penetrated into the copper electrode layer 38. Therefore, hydrogen has difficulty penetrating into the interior of the copper electrode layer 38 (i.e., the lower layer 38b). Thus, hydrogen embrittlement in the lower layer 38b can be effectively suppressed. In this way, hydrogen embrittlement can be suppressed in this embodiment, thereby suppressing the deterioration of the thermal conductivity and electrical conductivity of the copper electrode layer 38.

[0044] Furthermore, due to the low fluorine concentration in the lower layer 38b, the copper in the lower layer 38b has high purity. Therefore, high thermal conductivity and electrical conductivity can be achieved in the upper electrode 30.

[0045] Hydrogen embrittlement of the copper electrode layer is prone to occur in semiconductor devices having a polyimide film because hydrogen is released from the polyimide film. In contrast, as in this embodiment, if the copper electrode layer 38 contains fluorine, hydrogen embrittlement of the copper electrode layer 38 can be suppressed even when the polyimide film 60 is in contact with it. Therefore, using a fluorine-containing copper electrode layer in a semiconductor device having a polyimide film is more advantageous.

[0046] Furthermore, in the above embodiment, the lower layer 38b has a lower fluorine concentration than the surface layer 38a, but the lower layer 38b may also have the same fluorine concentration as the surface layer 38a. This structure can also suppress hydrogen embrittlement.

[0047] The copper electrode layer 58 has the same structure as the copper electrode layer 38, and therefore the copper electrode layer 58 performs the same function as the copper electrode layer 38. Thus, hydrogen embrittlement of the copper electrode layer 58 of the signal electrode pad 50 can be suppressed.

[0048] Next, the manufacturing method of the first embodiment will be described. Furthermore, the steps of forming the upper electrode 30 and the polyimide film 60 in the manufacturing method of the semiconductor element 100 will be described below.

[0049] First, such as Figure 3 As shown, an interlayer insulating film 22 is formed on the upper surface 10a of the semiconductor substrate 10. Next, a silicide layer 32 is formed within the contact hole 24. Then, a barrier metal layer 34 and a seed layer 36 are formed to cover the upper surface of the silicide layer 32 and the upper surface of the interlayer insulating film 22.

[0050] Next, as Figure 4 As shown, a resist mask 70 with an opening 72 is formed on the seed layer 36. The opening 72 is formed on the upper part of the contact hole 24. The contact hole 24 and its surrounding portion are disposed within the opening 72.

[0051] Next, as Figure 5 As shown, for example, a copper electrode layer 38 is formed on the seed layer 36 within the opening 72 using a plating technique. Then, the resist mask 70 is removed.

[0052] Next, as Figure 6 As shown, the seed layer 36 is removed by wet etching. In addition, the copper electrode layer 38 is also etched during the etching of the seed layer 36, but since the copper electrode layer 38 is sufficiently thicker than the seed layer 36, the reduction rate of the thickness of the copper electrode layer 38 is minimal.

[0053] Next, as Figure 7As shown, the barrier metal layer 34 is etched using reactive ion etching with CF4 gas. Here, the portion of the barrier metal layer 34 exposed from the copper electrode layer 38 is removed. At this time, since the upper surface 38u of the copper electrode layer 38 is exposed, the upper surface 38u is exposed to CF4 gas. Therefore, fluorine contained in the CF4 gas diffuses into the surface portion 38a of the copper electrode layer 38. Additionally, since the side surface 38s of the copper electrode layer 38 is exposed, the side surface 38s is exposed to CF4 gas. Therefore, fluorine contained in the CF4 gas diffuses into the side surface portion 38c of the copper electrode layer 38. Therefore, the fluorine concentration increases in the surface portion 38a and the side surface portion 38c. In the lower layer portion 38b, the fluorine concentration hardly increases. In the lower layer portion 38b, the fluorine concentration is below the detection limit. Furthermore, although the copper electrode layer 38 is also etched during the etching of the barrier metal layer 34, since the copper electrode layer 38 is sufficiently thicker than the barrier metal layer 34, the reduction rate of the thickness of the copper electrode layer 38 is extremely small.

[0054] Next, as Figure 8 As shown, a polyimide film 60 is formed to cover the interlayer insulating film 22 and the upper electrode 30. At this time, the polyimide film 60 is in contact with the side surface 38s and the upper surface 38u of the copper electrode layer 38. During the formation process of the polyimide film 60, hydrogen diffuses from the polyimide film 60 to the copper electrode layer 38. However, since the copper electrode layer 38 contains fluorine, hydrogen embrittlement in the copper electrode layer 38 is suppressed.

[0055] After that, as Figure 2 As shown, the polyimide film 60 on the upper part of the copper electrode layer 38 is removed, exposing the upper surface 38u of the copper electrode layer 38. This completes the process. Figure 1 The semiconductor element 100 shown.

[0056] In the manufacturing method of the first embodiment described above, a copper electrode layer 38 containing fluorine can be formed. Therefore, when using the semiconductor device 100, hydrogen embrittlement of the copper electrode layer 38 can be suppressed.

[0057] (Second Implementation) In the semiconductor device of the second embodiment, copper electrode layers 38 and 58 contain chlorine (Cl) instead of fluorine. Regarding other structures, the second embodiment is the same as the first embodiment. Chlorine reacts with hydrogen to produce hydrogen chloride (HCl). The vapor pressure of hydrogen chloride is higher than atmospheric pressure. Therefore, similar to the case with fluorine, hydrogen embrittlement of the copper electrode layer 38 is suppressed.

[0058] Next, the manufacturing method of the second embodiment will be described. In the manufacturing method of the second embodiment, the processing is performed in the same manner as in the manufacturing method of the first embodiment until... Figure 6 The state shown. Next, as... Figure 9As shown, the barrier metal layer 34 exposed from the copper electrode layer 38 is removed by reactive ion etching using BCl3 gas. At this time, chlorine diffuses into the surface portion 38a and the side portion 38c of the copper electrode layer 38. Thus, a copper electrode layer 38 containing chlorine in the surface portion 38a and the side portion 38c is obtained. Subsequently, a polyimide film 60 is formed in the same manner as in the first embodiment, thereby completing the semiconductor device.

[0059] The embodiments have been described in detail above, but these are merely illustrative and do not limit the scope of the claims. The technology described in the claims includes technologies obtained by various modifications and alterations to the specific examples described above. The technical elements described in this specification or drawings are useful individually or in various combinations, and are not limited to the combinations described in the claims at the time of application. Furthermore, the technology illustrated in this specification or drawings achieves multiple objectives simultaneously, and achieving one of these objectives is itself technically useful.

Claims

1. A semiconductor element having electrodes, characterized in that, The electrode has a copper electrode layer. The copper electrode layer contains elements that, when combined with hydrogen, generate compounds with a vapor pressure higher than atmospheric pressure.

2. The semiconductor device according to claim 1, characterized in that, The element is fluorine or chlorine.

3. The semiconductor device according to claim 1 or 2, characterized in that, The concentration of the element is 1×10 16 atoms / cm 3 above.

4. The semiconductor device according to claim 1 or 2, characterized in that, It also has a semiconductor substrate, The electrode is connected to the semiconductor substrate. The copper electrode layer has a main surface on the opposite side of the semiconductor substrate. The concentration of the element in the surface layer near the main surface is higher than the concentration of the element in the portion deeper than the surface layer from the main surface.

5. The semiconductor element according to claim 1 or 2, characterized in that, It also has a polyimide film in contact with the copper electrode layer.

6. A method for manufacturing a semiconductor device, characterized in that, It has the following processes: The process of forming an electrode with a copper electrode layer on a semiconductor substrate; and The process of exposing the copper electrode layer to CF4 gas while the copper electrode layer is exposed.

7. A method for manufacturing a semiconductor device, characterized in that, It has the following processes: The process of forming an electrode with a copper electrode layer on a semiconductor substrate; and The process of exposing the copper electrode layer to BCl3 gas while the copper electrode layer is exposed.

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