Semiconductor device including a solder compound containing a compound Sn/Sb

A semiconductor device and method is disclosed. In one embodiment, the semiconductor device comprises a semiconductor die comprising a first surface and a second surface opposite to the first surface, a first metallization layer disposed on the first surface of the semiconductor die, a first solder layer disposed on the first metallization layer, wherein the first solder layer contains the compound Sn/Sb, and a first contact member comprising a Cu-based base body and a Ni-based layer disposed on a main surface of the Cu-based base body, wherein the first contact member is connected with the Ni-based layer to the first solder layer.

CROSS-REFERENCE TO RELATED APPLICATION

This Utility Patent Applications claims priority to German Patent Application No. 10 2018 123 924.6, filed Sep. 27, 2018, which is incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a semiconductor device, an electronic device and to a method for fabricating a semiconductor device.

BACKGROUND

Decisions have been made by the European Union to ban environmentally hazardous substances in the near future.

These decisions have been made with regard to end-of-life vehicles ELV and to electrical and electronic Equipment (RoHS, Restriction of (the use of certain) Hazardous Substances in electrical and electronic equipment) and indicated that hazardous substances such as lead should be banned. In particular for power applications semiconductor dies and clips are nowadays soldered with a high Pb based soft solder paste. Since the EU wants to ban Pb, an alternative die and clip attach system has to be developed to be at least as good as the high Pb based paste system.

SUMMARY

A first aspect of the present disclosure relates to a semiconductor device. The semiconductor device according to the first aspect comprises a semiconductor die comprising a first surface and a second surface opposite to the first surface, a first metallization layer disposed on the first surface of the semiconductor die, a first solder layer disposed on the first metallization layer, the first solder layer containing the compound Sn/Sb, and a first contact member comprising a Cu-based base body and a Ni-based layer disposed on a main surface of the Cu-based base body, wherein the first contact member is connected with the Ni-based layer to the first solder layer.

According to an embodiment of the semiconductor device of the first aspect the solder layer further comprises an Ni/Sb phase. According to a further embodiment thereof, the solder comprises one or more further phases wherein the Ni/Sb phase is the dominant phase. The one or more further phases can be a Ni/Sn phase or two or three Ni/Sn phase of different material composition.

According to an embodiment of the semiconductor device of the first aspect the compound Sn/Sb of the solder layer is Pb free.

According to an embodiment of the semiconductor device of the first aspect the material composition of the compound Sn/Sb is such that the ratio of Sb in the compound is in a range from 17% to 90%. Such a ratio can be provided in order to reach a melting temperature of the solder material greater than 270° C.

According to an embodiment of the semiconductor device of the first aspect besides the ratio of Sb, the material composition is comprised of Sn or Sn with other materials, wherein Sn is predominant. The other materials may comprise one or more Ag, Au, Pt, Cu, Ni, and Pd.

According to an embodiment of the semiconductor device of the first aspect the material composition of the compound Sn/Sb is such that the melting point of the compound Sn/Sb is higher than 270° C. As already mentioned above this can, for example, be achieved by adjusting a ratio of Sb in a range from 17% to 90% in the Sb/Sn solder material which is deposited on the semiconductor die. During second level soldering a minimum melting temperature of 270° C. of the solder material is required.

According to an embodiment of the semiconductor device of the first aspect a thickness of the Ni-based layer is in a range from 100 nm to 7 μm.

According to an embodiment of the semiconductor device of the first aspect the contact member is comprised of a leadframe, a clip, a direct bonded copper, or an active metal brazing.

According to an embodiment of the semiconductor device of the first aspect a thickness of the contact member is in a range from 100 μm to 5 mm.

According to an embodiment of the semiconductor device of the first aspect the first metallization layer comprises a stack of two or more layers. The layers may comprise one or more of a Ti layer, an NiV layer, an NiP layer, an Ag layer, or an Al layer.

According to an embodiment of the semiconductor device of the first aspect the semiconductor die is one or more of a power die, a transistor die, a power transistor die, a vertical transistor die, an IGBT die, a diode die, or any other die which comprises which comprises a vertical structure and comprising contact pads on both opposing main surfaces.

According to an embodiment of the semiconductor device of the first aspect, the semiconductor device further comprises a second metallization layer disposed on the second surface of the semiconductor die, a second solder layer disposed on the second metallization layer, the second solder layer containing a compound Sn/Sb, a second contact member comprising a Cu-based base body and a Ni-based layer disposed on a main surface of the Cu-based base body, wherein the second contact member is connected with the Ni-based layer to the second solder layer. In such an embodiment the semiconductor die can be comprised of one or more of the types of semiconductor dies as were mentioned above.

According to an embodiment of the semiconductor device of the first aspect the second contact member is one or more of a clip, a directed bonded copper, an active metal braze, or a heat spreader.

According to an embodiment of the semiconductor device of the first aspect, wherein the first contact member is a leadframe and the second contact member is a clip.

A second aspect of the present disclosure relates to a semiconductor device. The semiconductor device according to the second aspect comprises a semiconductor chip comprising a first main surface and a second main surface opposite to the first main surface, a first contact member comprising a Cu-based base body and a Ni-based layer disposed on a main surface of the Cu-based base body, and a solder compound containing the compound Sn/Sb and being disposed between the semiconductor chip and the Ni-based layer.

The semiconductor chip of the semiconductor device of the second aspect may be comprised of a semiconductor die comprising a first surface and a second surface opposite to the first surface, and a first metallization layer disposed on the first surface of the semiconductor die in which case the first solder layer is disposed on the first metallization layer.

Further embodiments of the semiconductor device of the second aspect can be formed with embodiments of a semiconductor device of the first aspect or by adding one or more features as described in embodiments of a semiconductor device described further below.

A third aspect of the present disclosure relates to a semiconductor device. The semiconductor device according to the third aspect comprises an electronic component comprising a base body and a metallization layer disposed on a main surface of the base body, a solder layer disposed on the first metallization layer, the solder layer containing an Ni/Sb phase, and contact member comprising a Cu-based base body and a Ni-based layer disposed on a main surface of the Cu-based base body, wherein the contact member is connected with the Ni-based layer to the solder layer.

According to an embodiment of the semiconductor device of the third aspect, the solder layer contains a compound Sn/Sb. According to this embodiment, the solder process is carried out in such a way that an Sn/Sb solder material is not completely transformed into Ni/Sb and other intermetallic phases. According to another embodiment, the solder layer does not contain a compound Sn/Sb in which case the solder process is carried out in such a way that an Sn/Sb solder material is completely transformed into Ni/Sb and other intermetallic phases.

Further embodiments of the semiconductor device of the third aspect can be formed with embodiments of a semiconductor device of one of the first or second aspects or by adding one or more features as described in embodiments of a semiconductor device described further below.

A forth aspect of the present disclosure relates to a method for fabricating a semiconductor device. The method according to the forth aspect comprises providing a contact member comprising a Cu-based base body and a Ni-based layer disposed on a main surface of the Cu-based base body, providing a semiconductor die comprising a first surface and a second surface opposite to the first surface and a metallization layer disposed on the first surface of the semiconductor die, applying a solder material on one or more of the metallization layer of the semiconductor die or the Ni-based layer of the contact member, the solder material being based on a compound Sn/Sb, arranging the semiconductor die onto the contact member so that the soldering material is disposed between them, performing a solder process, in particular a reflow process, and thereby transforming the solder material into a solder layer and connecting the contact member with the semiconductor die.

According to an embodiment of the method according to the forth aspect, performing the reflow process comprises generating an Ni/Sb phase and one or more further phases, if any (see next paragraph). According to an embodiment thereof, the reflow process is carried out in such a way that the resulting solder layer still also contains the compound Sn/Sb. According to another embodiment the reflow process is carried out in such a way that the resulting solder layer does not contain the compound Sn/Sb.

According to an embodiment of the method according to the forth aspect, performing the reflow process comprises generating a Ni/Sb phase and one or more further phases wherein the Ni/Sb phase is the dominant phase. The one or more further phases may comprise an Ni/Sn phase or two more Ni/Sn phases of different material composition.

According to an embodiment of the method according to the forth aspect, the solder material is applied on both the semiconductor die and the contact member wherein equal or different kinds of solder material can be used.

According to an embodiment of the method according to the forth aspect, the solder material is applied in the form of a solder paste. The solder paste can be applied by dispensing or printing onto the semiconductor die or the contact member.

According to an embodiment of the method according to the forth aspect, a semiconductor die is provided having first and second metallization layers on its first and second main surfaces, and after arranging the semiconductor die with its first surface onto a first contact member, solder material is applied onto the second surface of the semiconductor die, a second contact member is arranged above the second surface so that the solder material is disposed in between, followed by a reflow process as already described above. With this embodiment a device as shown inFIG. 2may be fabricated.

Further embodiments of the method of the forth aspect can be formed with embodiments of a semiconductor device of one of the first to third aspects or by adding one or more features as described in embodiments of a semiconductor device described further below.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1shows an example of a semiconductor device according to one or more of the first to third aspects. The semiconductor device10ofFIG. 1comprises a semiconductor die1comprising a first lower main surface and a second upper main surface opposite to the first surface. The semiconductor device10comprises a metallization layer2which is disposed on the first surface of the semiconductor die1. The metallization layer2may be connected with an electronic device or circuitry disposed in the semiconductor die and may comprise one or more metallic layers.

The semiconductor device10ofFIG. 1further comprises a solder layer3disposed on the metallization layer2, wherein the solder layer3contains the compound Sn/Sb. The solder layer3may further contain an Ni/Sb phase and possibly further phases, in particular Ni/Sn phases, wherein the Ni/Sb is dominant.

The semiconductor device10ofFIG. 1further comprises a contact member4comprising a Cu-based base body4aand a Ni-based layer4bdisposed on a main surface of the Cu-based base body4a, wherein the contact member4is connected with the Ni-based layer4bto the solder layer3.

FIG. 2shows an example of a semiconductor device according to one or more of the first to third aspects. The semiconductor device20ofFIG. 2comprises a semiconductor die11comprising a first surface and a second surface opposite to the first surface and a first metallization layer12disposed on the first surface of the semiconductor die11, and a second metallization layer22disposed on the second surface of the semiconductor die11. The semiconductor device20furthermore comprises a first solder layer13disposed on the first metallization layer12, and a second solder layer23disposed on the second metallization layer22, wherein both the first and second solder layer13and23contain a compound Sn/Sb. The semiconductor device20furthermore comprises a first contact member4comprising a Cu-based base body4aand a Ni-based layer4bdisposed on a main surface of the Cu-based base body4a, wherein the first contact member4is connected with the Ni-based layer4bto the first solder layer3. The semiconductor device20furthermore comprises a second contact member24comprising a Cu-based base body24aand a Ni-based layer24bdisposed on a main surface of the Cu-based base body24a, wherein the second contact member24is connected with the Ni-based layer24bto the second solder layer23.

FIG. 3shows a flow diagram for illustrating a method for fabricating a semiconductor device according to the forth aspect of the present disclosure.

As shown inFIG. 3, the method30comprises providing a contact member comprising a Cu-based base body and a Ni-based layer disposed on a main surface of the Cu-based base body (31), providing a semiconductor die comprising a first surface and a second surface opposite to the first surface and a metallization layer disposed on the first surface of the semiconductor die (32), applying a solder material on one or more of the metallization layer of the semiconductor die or the Ni-based layer of the contact member, the solder material being based on a compound Sn/Sb (33), arranging the semiconductor die onto the contact member so that the soldering material is disposed between them (34), and performing a solder process, in particular a reflow process, and thereby transforming the solder material into a solder layer and connecting the contact member with the semiconductor die (35).

As indicated above, it is possible to apply the solder material onto one or both of the semiconductor die and the contact member. The solder material can be applied in the form of a solder paste by dispensing or printing.

After placement of the semiconductor die onto the contact member, the reflow process may be performed by heating the stack in a reflow or box oven with a specific temperature profile which fits to the mentioned materials and thicknesses. Afterwards the standard production flow is followed.

FIG. 4comprisesFIG. 4A to 4Fand shows cross-sectional representations of intermediate products for illustrating an exemplary method for fabricating a semiconductor according to a forth aspect.

As shownFIG. 4A, a leadframe44is provided, the leadframe44comprising a Cu-based base body44A and a Ni-based layer44B disposed on a main surface of the base body44A. The Cu-based base body44A might be comprised of pure Cu, or an alloy of Cu and another metal, and it may also comprise some dopings.

As shownFIG. 4B, a semiconductor chip41is provided comprising a semiconductor die41A, a first metallization layer41B disposed on a first main surface of the semiconductor die41A, and a second metallization layer41C disposed on a second main surface of the semiconductor die41A. The semiconductor die41A may comprise one or more of a power die, a transistor die, a power transistor die, a vertical transistor die, an IGBT die, a diode die, or any other die which comprises a vertical structure and comprises contact pads on both opposing main surfaces.

As shownFIG. 4C, a first solder material43is applied onto the first metallization layer41B of the semiconductor die41A by dispensing or printing.

As shownFIG. 4D, the semiconductor chip41is placed onto the leadframe44, i.e. onto the Ni based layer44B of the leadframe44so that the first solder material43is disposed between them.

As shownFIG. 4E, a second solder material46is applied onto the semiconductor chip41, i.e. onto the second metallization layer41C. The second solder material46can be dispensed or printed onto the upper surface of the equal or different to the first solder material43.

As shownFIG. 4F, a Cu based clip47is placed onto the second solder material46. The clip47might be comprised of pure Cu, or an alloy of Cu and another metal, and it may also comprise some dopings.

Thereafter a reflow process is performed by heating the stack in a reflow or box oven with a specific temperature profile fitting to the solder materials and their thicknesses. Thereby the solder materials are transformed into respective solder layers and the semiconductor chip41is connected to the leadframe44and the clip47.

FIG. 5shows an example of a liquid phase projection diagram of a ternary alloy phase of Sn, Sb, and Ni.

It can be seen in the diagram that without the Sb the Sn would at least partially form a Ni3Sn4phase in contact with the Ni, which phase is known to be rather brittle. The Sb content avoids the formation of this brittle phase. As can be derived from the diagram, a minimum amount of Sb is required to force the formation of the hexagonal Ni/Sb-phase instead of the monoclinic Ni3Sn4phase. From experimental evidence, it is found that the Sb has to exceed a certain amount, as has already been stated above. The intersection line can also be seen in the ternary alloy phase diagram, but as this was calculated for the equilibrium state and the soldering process is usually in a non-equilibrium state, the required amount of Sb in a solder material is higher than can be derived from thermodynamic calculations.

The details of the diagram ofFIG. 5are as follows.

From a minimum temperature T(min)=673 K to a maximum temperature T(max)=2561.7 K one can recognize the following four-phase intersection points with the liquid:

Wherein

FIG. 6shows an SEM-EDX measurement which illustrates the formation of the intermetallic Ni/Sb phase in the solder layer.

As can further be seen, none of the brittle Ni3Sn4phase is formed even in direct vicinity of the Ni layers in accordance with the alloy phase diagram.