Semiconductor device solder bump having intrinsic potential for forming an extended eutectic region and method for making and using the same
First Claim
1. A method for making a solder bump on a bonding pad of a semiconductor device, comprising the steps of:
- providing a first metal layer overlying the bonding pad to provide adhesion of the solder bump to the semiconductor device;
providing a second metal layer overlying the first metal layer;
forming in a vacuum environment a first tin layer overlying the second metal layer, wherein the first tin layer and the second metal layer are mutually soluble such that an intermetallic of the second metal layer and the first tin layer may be formed;
in situ forming a lead layer overlying the first tin layer without breaking the vacuum environment, wherein the lead layer is thicker than the first tin layer; and
forming a second tin layer overlying the lead layer without breaking the vacuum environment, wherein the second tin layer is thinner than the lead layer to provide localized eutectic formation at a top of the solder bump during solder reflow.
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Accused Products
Abstract
A semiconductor device (32) has an as-deposited solder bump (34) having the intrinsic potential for forming an extended eutectic region for simplified DCA applications. The as-deposited solder bump (34) has first tin layer (40) overlying the UBM of the bonding pad (14) on the device. The first tin layer reacts with a metal layer (36) in the UBM to form an intermetallic for adhering the solder bump to the bonding pad. A thick lead layer (42) overlies the first tin layer to provide the substantial component of the solder bump. A second tin layer (44) overlies the lead layer to provide localized eutectic formation at the top surface of the bump during reflow. A device having at least this solder bump structure can be directly attached to either ceramic or PC board substrates. Additional layers of tin and /or lead may be supplemented to the basic bump structure to optimize the eutectic formation rate.
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Citations
13 Claims
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1. A method for making a solder bump on a bonding pad of a semiconductor device, comprising the steps of:
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providing a first metal layer overlying the bonding pad to provide adhesion of the solder bump to the semiconductor device; providing a second metal layer overlying the first metal layer; forming in a vacuum environment a first tin layer overlying the second metal layer, wherein the first tin layer and the second metal layer are mutually soluble such that an intermetallic of the second metal layer and the first tin layer may be formed; in situ forming a lead layer overlying the first tin layer without breaking the vacuum environment, wherein the lead layer is thicker than the first tin layer; and forming a second tin layer overlying the lead layer without breaking the vacuum environment, wherein the second tin layer is thinner than the lead layer to provide localized eutectic formation at a top of the solder bump during solder reflow. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 13)
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11. A method for performing direct chip attach comprising the steps of:
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providing a semiconductor device having a first metal layer overlying a bonding pad to provide adhesion for subsequent metal layers to the semiconductor device, a second metal layer overlying the first metal layer, and a solder bump comprising a first tin layer overlying the second metal layer, wherein the first tin layer and the second metal layer are mutually soluble such that an intermetallic of the second metal layer and the first tin layer may be formed, a lead layer overlying the first tin layer, wherein the lead layer is thicker than the first tin layer, and a second tin layer overlying the lead layer, wherein the second tin layer is thinner than the lead layer to provide localized eutectic formation at a top surface of the solder bump during solder reflow; positioning the semiconductor device with the solder bump overlying and facing a conductive trace on a mounting substrate; aligning the solder bump and the conductive trace such that the solder bump is approximately centered over the conductive trace; bringing the solder bump into physical contact with the conductive trace; and heating the solder bump to a temperature approximately in a range of 183°
C. to less than 250°
C., wherein a eutectic liquidus solder composed of the second tin layer and a portion of the lead layer is formed at a surface of the solder bump,wherein the eutectic liquidus solder wets to the conductive trace to join the semiconductor device to the mounting substrate.
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Specification