Nickel-Plating Stack, Semiconductor Device, Manufacturing Apparatus for Nickel-Plating Stack, Method of Manufacturing Nickel-Plating Stack, and Method of Manufacturing Semiconductor Device

This nonprovisional application is based on Japanese Patent Application No. 2024-085311 filed on May 27, 2024 with the Japan Patent Office, the entire contents of which are hereby incorporated by reference.

The present disclosure relates to a nickel-plating stack, a semiconductor device, a manufacturing apparatus for a nickel-plating stack, a method of manufacturing a nickel-plating stack, and a method of manufacturing a semiconductor device.

Conventionally, there has been known a method of manufacturing a nickel-plating stack, wherein a nickel-plating stack is formed on a plating-target member by immersing the plating-target member in a nickel plating solution. The nickel-plating stack is formed by a nickel layer including phosphorus. The plating-target member immersed in the nickel plating solution is removed and is immersed in another nickel plating solution having a different phosphorus concentration, thereby further forming a nickel layer having a different phosphorus concentration. However, when the plating-target member is removed from the nickel plating solution, an oxide film may be formed between the nickel layers. In Japanese Patent Laying-Open No. 2017-128791, two nickel layers having different phosphorus concentrations are formed by changing a condition (concentration, temperature, or the like) of a nickel plating solution without removing a plating-target member from the nickel plating solution.

However, in the above-described conventional method, it is difficult to change a phosphorus concentration a plurality of times among the plurality of nickel layers. Therefore, in the conventional method, there is room for improvement in changing a phosphorus concentration among the plurality of nickel layers.

The present disclosure has been made to solve the above-described problem, and has an object to provide a nickel-plating stack, a semiconductor device, a manufacturing apparatus for a nickel-plating stack, a method of manufacturing a nickel-plating stack, and a method of manufacturing a semiconductor device, so as to readily change a phosphorus concentration among a plurality of nickel layers.

A method of manufacturing a nickel-plating stack according to the present disclosure includes: preparing a nickel plating solution including phosphorus and a sulfur additive, and a plating-target member; and forming a nickel-plating stack on the plating-target member using the nickel plating solution. The nickel-plating stack includes nickel layers having different phosphorus concentrations.

A method of manufacturing a semiconductor device according to the present disclosure uses the above-described method of manufacturing a nickel-plating stack. The plating-target member includes a semiconductor base member.

A manufacturing apparatus for a nickel-plating stack according to the present disclosure includes a container and at least one of a convection mechanism and a shaking mechanism. The container accommodates a nickel plating solution. The convection mechanism causes convection of the nickel plating solution. The shaking mechanism shakes the plating-target material.

A nickel-plating stack according to the present disclosure include at least three or more nickel layers. Two nickel layers having different phosphorus concentrations among the nickel layers are disposed in direct contact with each other.

A semiconductor device according to the present disclosure includes: the nickel-plating stack; and a connection member. A recess is provided in the nickel-plating stack. The nickel-plating stack and the connection member are connected by the recess.

The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.

Hereinafter, embodiments of the present disclosure will be described. It should be noted that in the below-described figures, the same or corresponding portions are denoted by the same reference characters and will not be described repeatedly, unless stated otherwise particularly.

is a schematic cross sectional view of a nickel (Ni) plating stackaccording to a first embodiment. Nickel-plating stackshown inis, for example, a nickel-plating stackformed on a plating-target member, and includes at least three or more nickel layers.

Plating-target membermay be any member. Plating-target membermay be a semiconductor substrate of a semiconductor device. Plating-target membermay include a semiconductor base memberand a wiring layeras described later (see). Nickel-plating stackmay be disposed on wiring layer(see).

As shown in, nickel-plating stackis constituted of the plurality of nickel layers. Nickel-plating stackmay be constituted of three or more nickel layers, may be constituted of five or more nickel layers, or may be constituted of ten or more nickel layers.

As described below, each of nickel layersis formed using a nickel (Ni) plating solution including phosphorus (P). That is, nickel layerincludes phosphorus. Two nickel layersdisposed adjacent to each other have different phosphorus concentrations. No oxide film is formed between the plurality of nickel layers. That is, the two nickel layers disposed adjacent to each other are disposed in direct contact with each other.

Specifically, the plurality of nickel layersinclude a first layer, a second layer, and a third layer. First layeris adjacent to second layer. Third layeris adjacent to second layer. Third layeris disposed in a region opposite to a region in which first layeris disposed when viewed from second layer. That is, first layer, second layer, and third layerare stacked in this order.

No oxide film is formed between first layerand second layer. That is, first layeris in direct contact with second layer. No oxide film is formed between second layerand third layer. That is, second layeris in direct contact with third layer.

A phosphorus concentration in first layeris different from a phosphorus concentration in second layer. Moreover, the phosphorus concentration in second layeris different from a phosphorus concentration in third layer. The phosphorus concentration in first layermay be more than or less than the phosphorus concentration in second layer. The phosphorus concentration in second layermay be more than or less than the phosphorus concentration in third layer. Thus, the phosphorus concentrations in adjacent nickel layersare different from each other.

A combination of nickel layersto be stacked may be changed in accordance with properties of nickel layerscorresponding to the phosphorus concentrations. Table 1 shows physical properties of each of a low phosphorus layer, a medium phosphorus layer, and a high phosphorus layer. From the top, Table 1 shows phosphorus concentration, crystal state, magnetic property, saltwater resistance spray time (unit: Hr), acid resistance, hardness (Vickers hardness) before heat treatment, hardness (Vickers hardness) after heat treatment, coefficient of thermal expansion, electrical resistivity, internal stress, wear resistance, and solder wettability. The hardness after heat treatment indicates hardness after performing heat treatment at 400° C. for one hour. The wear resistance is represented by an indicator indicated by the Test Wear Index (TWI). The TWI indicates resistance of a material against mechanical effects such as friction and abrasion.

When the phosphorus concentration in nickel layeris 1 mass % or more and 4 mass % or less, nickel layeris the low phosphorus layer described in Table 1. When the phosphorus concentration in nickel layeris 5 mass % or more and 8 mass % or less, nickel layeris the medium phosphorus layer described in Table 1. When the phosphorus concentration in nickel layeris 9 mass % or more and 12 mass % or less, nickel layeris the high phosphorus layer described in Table 1.

It should be noted that in Table 1, A, B, and C represent evaluations on each of the acid resistance and the solder wettability. It is indicated that B is more excellent than C. It is indicated that A is more excellent than B. That is, it is indicated that A has the most excellent evaluation among A, B, and C. Moreover, the saltwater resistance spray time indicates a time to a stage at which a specific value is exceeded in a saltwater spray test. A degree of corrosion is evaluated through both appearance observation and mass-material measurement.

Nickel-plating stackmay be a nickel-plating stackin which the low phosphorus layer and the medium phosphorus layer are sequentially stacked. The low phosphorus layer has relatively inferior corrosion resistance, but the medium phosphorus layer has excellent corrosion resistance. Therefore, when the low phosphorus layer and the medium phosphorus layer are sequentially stacked, the corrosion resistance of the low phosphorus layer is complemented by the medium phosphorus layer. Moreover, each of the low phosphorus layer and the medium phosphorus layer has a magnetic property when heated.

Nickel-plating stackmay be a nickel-plating stackin which the medium phosphorus layer and the high phosphorus layer are sequentially stacked. The medium phosphorus layer has relatively inferior solder wettability, but the high phosphorus layer has excellent solder wettability. Therefore, when the medium phosphorus layer and the high phosphorus layer are sequentially stacked, the solder wettability of the medium phosphorus layer is complemented by the high phosphorus layer. Moreover, the medium phosphorus layer has a magnetic property when heated. It should be noted that the high phosphorus layer does not have a magnetic property.

The thickness of each of nickel layersmay be, for example, 0.1 μm or more and 0.4 μm or less. The average value of thickness of each of nickel layersin nickel-plating stackmay be 0.1 μm or more and 0.5 μm or less. The lower limit of the average value of thickness may be 0.15 μm or 0.2 μm. The upper limit of the average value of thickness may be 0.4 μm or 0.3 μm. The average value may be 0.23 μm, for example. The thickness of nickel-plating stack(total thickness of nickel layers) may be 0.3 μm or more and 10 μm or less. The lower limit of the thickness may be 1 μm, 2 μm, 3 μm, or 4 μm. The upper limit of the thickness may be 8 μm, 6 μm, or 5 μm. The thickness may be, for example, 4.3 μm. Thus, since the thickness of each of nickel layersis of a submicron level, internal stress of nickel-plating stackis relaxed.

Thus, by forming nickel layershaving different phosphorus concentrations, a nickel-plating stackto attain an effect corresponding to a purpose of use can be obtained. In particular, by forming three or more nickel layershaving different phosphorus concentrations, effects can be attained such as improvement in wear resistance, improvement in corrosion resistance, improvement in solder wettability, increase in hardness (Vickers hardness), and relaxation of stress.

Next, a manufacturing apparatusfor nickel-plating stackaccording to the first embodiment will be described.is a schematic diagram of manufacturing apparatusfor nickel-plating stackaccording to the first embodiment. Nickel-plating stackis formed using manufacturing apparatusshown in. Manufacturing apparatusfor nickel-plating stackincludes a container, a convection mechanism, and a shaking mechanism. Manufacturing apparatusmay include at least one of convection mechanismand shaking mechanism, and may include both convection mechanismand shaking mechanismas shown in.

Containeraccommodates nickel (Ni) plating solutionand plating-target member. Nickel plating solutionis, for example, an electroless nickel plating solution and includes phosphorus (P) and a sulfur additive. The sulfur additive is, for example, thiocyanate hydrochloride or the like.

By immersing plating-target memberin nickel plating solution, nickel-plating stackconstituted of nickel layersis manufactured. A rate of forming nickel layeris changed depending on an amount of the sulfur additive included in nickel plating solution. Moreover, when a relative flow velocity of nickel plating solutionwith respect to plating-target memberon which nickel layeris to be formed is changed, a frequency of contact between a surface of plating-target memberand nickel ions in nickel plating solutionis changed. As a result, the rate of forming a nickel film on the surface of plating-target memberis increased. Since the rate of forming nickel layeris changed in this way, the phosphorus concentrations in nickel layersare changed. For example, when the amount of the sulfur additive included in nickel plating solutionis smaller, the phosphorus concentration in nickel layerto be formed is increased. When the relative flow velocity of nickel plating solutionwith respect to the surface of plating-target memberis faster, the phosphorus concentration in nickel layerto be formed is decreased.

Manufacturing apparatusshown informs the plurality of nickel layershaving different phosphorus concentrations by changing amounts of nickel (Ni) and phosphorus (P) to come into contact with plating-target memberper unit time. That is, nickel-plating stackhaving a phosphorus concentration gradient is manufactured.

In order to manufacture nickel-plating stackaccording to the first embodiment, at least one of convection mechanismand shaking mechanismis used.

Convection mechanismcauses convection of nickel plating solution. Nickel plating solutionmay be circulated using convection mechanismas shown in. As a result, the convection of nickel plating solutionmay be caused in container.

Specifically, as shown in, convection mechanismhas a tubular pathand a pump. Both ends of tubular pathare connected to container. Nickel plating solutionflows from containerinto tubular pathvia one end of tubular pathas indicated by an arrow, and passes through the inside of tubular path. Pumpis provided in tubular path. That is, pumpis provided between one end and the other end of tubular path. Pumpsends out nickel plating solution. Nickel plating solutionhaving passed through tubular pathflows into containeragain via the other end of tubular path

In this way, nickel plating solutionin containeris circulated through tubular path. That is, the flow rate of nickel plating solutionto come into contact with plating-target member(amount of nickel plating solutionto come into contact with plating-target memberper unit time) may be adjusted by circulating nickel plating solutionusing convection mechanism.

The flow rate of nickel plating solutionto come into contact with plating-target memberis determined by a circulation flow rate of nickel plating solutionflowing into and out of container. The circulation flow rate may be 30 L/minute or more and 60 L/minute or less, or may be 40 L/minute or more and 50 L/minute or less.

When the circulation flow rate is increased, the number of times of making contact between plating-target memberand nickel ions in nickel plating solutionper unit time is increased. That is, when the flow rate of nickel plating solutionto come into contact with the surface of plating-target memberis increased, nickel layerhaving a low phosphorus concentration is formed.

When nickel layerhaving a low phosphorus concentration is formed, the amount of the sulfur additive in nickel plating solutionbecomes small. Therefore, nickel plating solutionis adjusted to form nickel layerhaving a high phosphorus concentration. As a result, nickel layerhaving a high phosphorus concentration is formed adjacent to nickel layerhaving a low phosphorus concentration.

Thus, nickel layerhaving a desired phosphorus concentration can be formed by adjusting the flow rate of nickel plating solutionto come into contact with plating-target member.

Plating-target memberis accommodated in containeras described above. Plating-target memberis immersed in contact with nickel plating solution. Plating-target membermay be held by shaking mechanism. Shaking mechanismshakes, for example, in an upward/downward direction. As a result, plating-target memberis shaken in the upward/downward direction. Shaking mechanismmay shake in a leftward/rightward direction, for example. In this way, the flow rate of nickel plating solutionto come into contact with plating-target membermay be adjusted by shaking plating-target member.

When nickel layeris formed, hydrogen gas is generated at the surface of plating-target member. When the formation of nickel layerproceeds with the hydrogen gas remaining at the surface of plating-target member, a defect called a pit or pinhole is generated. In order to prevent the generation of the defect, shaking mechanismmay include a shocking mechanism. Shocking mechanismmay be, for example, an air cylinder or an oscillation cam. As shown in, shocking mechanismmay be disposed on an inner wall surface of container.

Shocking mechanismapplies a shock to plating-target member. In this way, the hydrogen gas generated at the surface of plating-target membercan be removed from the surface of plating-target member. Moreover, with shocking mechanism, the effect of the convection of nickel plating solutionis increased.

A period of shaking by shaking mechanismmay be, for example, 1 second or more and 5 seconds or less. A period of applying the shock to plating-target memberby shocking mechanismmay be the same as the period of shaking by shaking mechanism.

Thus, by using shaking mechanismto adjust the flow rate of nickel plating solutionto come into contact with plating-target member, nickel layerhaving a desired phosphorus concentration can be formed.

In order to adjust the flow rate of nickel plating solutionto come into contact with plating-target member, convection mechanismmay be used, shaking mechanismmay be used, or both convection mechanismand shaking mechanismmay be used.

is a schematic diagram of a modification of manufacturing apparatusfor nickel-plating stackaccording to the first embodiment.corresponds to. Manufacturing apparatusshown inbasically has the same configuration as that of manufacturing apparatusshown inand can attain the same effect, but is different therefrom in that nickel plating solutionis stirred.

Specifically, as shown in, convection mechanismhas a fan. When fanis rotated, nickel plating solutionin containeris stirred. Convection mechanismmay have a stirrer instead of fan

In this way, nickel plating solutionin containermay be stirred using convection mechanismhaving fan. By stirring nickel plating solution, the flow rate of nickel plating solutionto come into contact with plating-target membermay be adjusted.

The flow rate of nickel plating solutionto come into contact with plating-target memberis determined by the rotation speed of convection mechanismthat stirs nickel plating solution. The rotation speed of convection mechanismmay be 400 rpm or more and 1000 rpm or less, or may be 600 rpm or more and 800 rpm or less.

When the rotation speed of convection mechanismis increased, the number of times of making contact between plating-target memberand nickel ions in nickel plating solutionis increased. That is, nickel layerhaving a low phosphorus concentration is formed by increasing the flow rate of nickel plating solutionto come into contact with the surface of plating-target member.