Conductive paste and semiconductor component having conductive bumps made from the conductive paste

Conductive paste and semiconductor composition with conductive bumps made from the conductive paste

The present invention was filed in US Patent No. 09/323,464 on June 1, 1999.

The present invention generally relates to electrical interconnection, and more particularly to interconnection bumps.

Semiconductor manufacturers often form conductive bumps on semiconductor wafers to promote electrical contact with substrates, such as printed circuit boards, tape automated bonding (TAB) substrates, lead frames, and so on. The advantages of using conductive bumps include: increased input and output (I/O) strength, which results in a smaller device "footprint", increased signal transmission speed due to shorter interconnections, reduced vertical profile, and lower device weight.

Typically, the conductive bump is formed by depositing a layer of shielding or template material on the substrate, forming an opening in the solder shield, disposing a conductive paste in the opening, and reflowing the conductive paste to form a conductive bump. The disadvantage of the currently available conductive paste is that voids are formed in the conductive bumps after the conductive paste is reflowed. These voids weaken the junction between the conductive bump and the substrate, which leads to reliability problems. In addition, residual flux that is difficult to remove is left after the reflow step. The residual flux reduces the bonding strength between the conductive bumps and the unfilled material, and increases the leakage current of the device.

Therefore, it would be advantageous to have a conductive paste for manufacturing conductive bumps and a manufacturing method for manufacturing conductive bumps with a reduced number of voids. It would be more advantageous to be able to form conductive bumps that are easy and cost-effective after reflow.

1 is a highly enlarged cross-sectional view of the semiconductor wafer during the initial stage of manufacturing according to a specific embodiment of the present invention; FIG. 2 is a highly enlarged cross-sectional view of the semiconductor wafer of FIG. 1 during manufacturing; and FIG. 3 is the height of the semiconductor wafer of FIG. 1 An enlarged cross-sectional view showing conductive bumps formed thereon according to a specific embodiment of the present invention.

For simplicity and clarity of description, the elements in the drawings are not necessarily drawn to a certain scale, and the same reference numbers in different drawings represent the same elements.

Detailed description of the drawings

Generally, the present invention proposes a conductive paste, such as a solder paste, and a method of using the conductive paste to form conductive bumps. The conductive bumps produced by using the conductive paste of the present invention have fewer gaps than the currently available conductive paste manufacturers. In addition, any residual conductive paste left after reflow can be easily removed with water.

According to the first embodiment of the present invention, the conductive paste is formed by combining a tin alloy with a flux composition containing an aromatic carboxylic acid flux and a solvent. Suitable tin alloys include: tin-silver alloy (SnAg3.5) containing about 3.5% by weight of silver; tin-copper alloy (SnCu0.7) containing about 0.7% by weight of copper; containing about 2% by weight of silver and about 2% by weight % Bismuth tin-silver-bismuth alloy (SnAg2Bi2); tin-silver-copper alloy (SnAg4 Cu0.5) containing about 4% by weight silver and about 0.5% by weight copper; tin-antimony alloy containing about 5% by weight antimony ( SnSb5); and tin-lead alloy (SnPb), wherein the tin content in the tin-lead alloy is about 2% by weight to about 70% by weight. The aromatics have the following general formula:<chemistry general="n"><img file="TWI282992B_D0001.tif" /></chemistry>

Wherein R is hydrogen or an alkyl group including 1 to 16 carbon atoms; and n is an integer of 0 to 3.

The polymer solvent is a non-boiling polymer solvent with the following general formula:<chemistry general="n"><img file="TWI282992B_D0002.tif" /></chemistry>

Wherein n is an integer from 6 to 100; R1 is hydrogen or an alkyl group containing 1 to 20 carbon atoms; and R2 is hydrogen or an alkyl group containing 1 to 20 carbon atoms.

Preferably, the flux composition includes about 12.5% by weight of 4-hydroxybenzoic acid as an aromatic carboxylic acid flux, and about 87.5% by weight of polypropylene glycol ether as a non-boiling polymer solvent. In addition, when using this chemical formula as a flux composition, it is preferable to perform a double reflow step to form conductive bumps.

According to the second embodiment of the present invention, the conductive paste is formed by combining a tin alloy with a flux composition containing an aromatic carboxylic acid flux, a flux carrier and a solvent. Suitable tin alloys include: tin-silver alloy (SnAg3.5) containing about 3.5% by weight of silver; tin-copper alloy (SnCu0.7) containing about 0.7% by weight of copper; containing about 2% by weight of silver and about 2% by weight Tin-silver-bismuth alloy (SnAg2Bi2) containing about 4% by weight of silver and about 0.5% by weight of copper (SnAg4Cu0.5); containing about 5% by weight of antimony (SnSb5) ); and tin-lead alloy (SnPb), wherein the tin content in the tin-lead alloy is about 2% by weight to about 70% by weight. The aromatics have the following general formula:<chemistry general="n"><img file="TWI282992B_D0003.tif" /></chemistry>

Wherein R is hydrogen or an alkyl group including 1 to 16 carbon atoms; and n is an integer of 0 to 3.

The carrier has the following general formula:<chemistry general="n"><img file="TWI282992B_D0004.tif" /></chemistry>

Where n is an integer from 5 to 100.

The polymer solvent is a non-boiling polymer solvent with the following general formula:<chemistry general="n"><img file="TWI282992B_D0005.tif" /></chemistry>

Wherein n is an integer from 6 to 100; R1 is hydrogen or an alkyl group containing 1 to 20 carbon atoms; and R2 is hydrogen or an alkyl group containing 1 to 20 carbon atoms.

Preferably, the flux composition includes about 12.5% by weight of 4-hydroxybenzoic acid as an aromatic carboxylic acid flux, about 33.3% by weight of polyethylene glycol, ie where n=20, as a flux carrier, and about 54.2% by weight Polypropylene glycol ether is used as a non-boiling polymer solvent. In addition, when using this formulation as a flux composition, it is preferable to use a tin-lead alloy as the metal, wherein the weight percentage of tin in the tin-lead alloy is about 2% to about 70% by weight.

According to the third embodiment of the present invention, the conductive paste is formed by combining a tin alloy and a flux composition as described in the second embodiment, except that the flux of the third embodiment includes aromatics and fatty acids. A mixture of family acids. The aliphatic acid has the following general formula:<chemistry general="n"><img file="TWI282992B_D0006.tif" /></chemistry>

Where n is an integer of 0-16.

Similar to the second embodiment, the flux composition preferably includes about 12.5% by weight of 4-hydroxybenzoic acid as an aromatic carboxylic acid flux, and about 33.3% by weight of polyethylene glycol, that is, where n=20, as a flux The carrier, and about 54.2% by weight polypropylene glycol butyl ether as the non-boiling polymer solvent.

According to the fourth embodiment of the present invention, the conductive paste is formed by combining a tin alloy with a flux composition containing an aromatic carboxylic acid flux, a flux carrier, a second flux and a solvent. Similar to the first and second embodiments, suitable tin alloys include: tin-silver alloy (SnAg3.5) containing about 3.5% by weight of silver; tin-copper alloy (SnCu0.7) containing about 0.7% by weight of copper; A tin-silver-bismuth alloy (SnAg2Bi2) containing about 2% by weight silver and about 2% by weight bismuth; a tin-silver-copper alloy (SnAg4Cu0.5) containing about 4% by weight silver and about 0.5% by weight copper; containing about 5 wt% antimony tin-antimony alloy (SnSb5); and tin-lead alloy (SnPb), wherein the tin content in the tin-lead alloy is about 2% to about 70% by weight. The aromatics have the following general formula:<chemistry general="n"><img file="TWI282992B_D0007.tif" /></chemistry>

Wherein R is hydrogen or an alkyl group including 1 to 20 carbon atoms; and n is an integer of 0 to 3.

The flux carrier has the following general formula:<chemistry general="n"><img file="TWI282992B_D0008.tif" /></chemistry>

Where n is an integer from 5 to 100.

The second flux has the following general formula:<chemistry general="n"><img file="TWI282992B_D0009.tif" /></chemistry>

Where n is an integer of 0-16.

The polymer solvent is a non-boiling polymer solvent with the following general formula:<chemistry general="n"><img file="TWI282992B_D0010.tif" /></chemistry>

Wherein n is an integer of 6 to 100; R1 is hydrogen or an alkyl group having 1 to 18 carbon atoms; and R2 is hydrogen or an alkyl group having 1 to 18 carbon atoms.

Preferably, the flux composition includes 17% by weight of 4-hydroxybenzoic acid as an aromatic acid flux, 12% by weight of polyethylene glycol as a flux carrier, 6% by weight of adipic acid as a second flux carrier, and 65 The weight% polypropylene glycol ether is used as a non-boiling polymer solvent.

The technology of combining the components of the flux composition and the metal alloy is known to those skilled in the art.

FIG. 1 is a highly enlarged cross-sectional view of a semiconductor wafer 10, which has a surface 11 and a number of connection pads 13 formed on the surface 11. As shown in FIG. In addition, a layer 12 of dielectric material is formed on the surface 11. If necessary, an under-bump metallization layer 15 may be formed on the connection pad 13. The technology of forming connection pads on the surface of a semiconductor wafer and forming under-bump metallization on the connection pads is known to those skilled in the art. In addition, it is well known that semiconductor wafers are composed of many semiconductor chips containing circuit components, such as transistors, diodes, integrated circuits, passive components, and so on. The connection pad 13 and the under-bump metallization layer 15 make electrical contact with the appropriate position of the integrated circuit or semiconductor device. It should be noted that the circuit components are not shown in FIG. 1.

Referring to FIG. 1, a layer of solder shielding material 14 and bonding pad 12 are formed on the surface 11. The solder shielding layer 14 is patterned, so the metallization layer 15 under the bump is exposed. It should be understood that the use of a layer of flux shielding material is not a limitation of the present invention. For example, a mechanical template or the like can be used instead of a layer of flux shielding material.

Referring now to FIG. 2, the conductive paste 16 is formulated according to the present invention, applied to the flux shielding layer 14 and applied to the openings in the flux shielding layer 14. Preferably, the conductive paste 16 is dispersed or spread on the surface of the flux shielding layer 14 so as to roughly cover the surface of the semiconductor wafer 10. Use a squeegee (not shown) or other suitable tools to sweep the conductive paste 16 across the flux shielding layer and fill the openings in the flux layer 14 considerably. The excess conductive paste is removed from the surface of the flux shielding layer 14.

Referring now to FIG. 3, the solder shield is removed, and the conductive paste is reflowed to form conductive bumps 18. The conductive bump 18 is also referred to as a solder bump. After that, water is used to clean the conductive bumps to remove flux residues.

Although the conductive paste 16 is shown and described as on a semiconductor wafer, it should be understood that this is not a limitation of the present invention. For example, the conductive bump can be formed on a printed circuit board, an elastic circuit, metalized ceramic or glass, or the like.

It should be expected that a conductive paste and a method of using the conductive paste will be proposed so far. The conductive paste of the present invention produces conductive bumps that have less voids than conventional pastes. One reason for reducing the number of voids is the formation of hydrogen bonds between the hydroxyl and carboxyl groups on the aromatic carboxylic acid flux and the alkoxy group on the solvent, so very high flux concentrations can be used in the paste. Another advantage of the present invention is that the residual flux can be easily cleaned with water. In addition, in order to reduce the cost of cleaning conductive bumps, the use of water is a more environmentally friendly system.