JPH0567620A - Bump formation - Google Patents

Abstract

(57) [Summary] (Modified) [Purpose] To eliminate the phenomenon that bumps provided on electrode parts of semiconductor devices formed on a wafer are peeled off due to aging after device mounting. [Structure] A barrier metal 6 is deposited on the entire surface of the semiconductor element 2 by sputtering, and then a photosensitive resist is applied,
The photosensitive resist is patterned so as to connect all the electrode portions 4 on the semiconductor element through the cutting area 3 between the semiconductor elements, and the barrier metal is etched using this as a mask.
The photosensitive resist is peeled off, and the wafer is washed with pure water.
The photosensitive polyimide 12 is applied on the entire surface and patterned so that only the electrode portions are opened, and bumps are formed in the openings by wet plating using the etched barrier metal as a plating electrode. Next, the photosensitive polyimide is heat-baked at a predetermined temperature to polyimidize the photosensitive polyimide and the film thickness thereof is halved so that the formed bumps protrude from the polyimide film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming bumps suitable for device mounting on electrode parts of semiconductor devices formed in large numbers on a wafer.

[0002]

2. Description of the Related Art As shown in FIG. 11, a large number of semiconductor elements 2 formed on a wafer 1 are divided by a cutting area 3.
As shown in FIG. 12, a wiring protective film 5 is formed in addition to the electrode portion 4. A conventional method for forming bumps for mounting elements on the electrode portion 4 is to first form a barrier on the entire surface of the wafer 1 on which a large number of semiconductor elements 2 are formed as shown in FIGS. 11 and 12, as shown in FIG. After depositing the metal 6 by sputtering, as shown in FIG. 14, a thick film photosensitive resist 7 for straight bumps is applied to the entire surface. Next, the photosensitive resist 7 is patterned by photolithography as shown in FIG. 15 so that only the electrode portion 4 is opened. Next, as shown in FIG. 16, bumps 8 are formed in the openings by the wet plating method using the barrier metal 6 as a plating electrode. Next, as shown in FIG. 17, the photosensitive resist 7 is peeled off, and the wafer 1 is washed with pure water. Then, a photosensitive resist 9 is applied on the entire surface as shown in FIG. 18, and the photosensitive resist 9 is patterned so as to cover the bumps 8 by photolithography as shown in FIG. Next, the barrier metal 6 is etched as shown in FIG. 20 using the patterned photosensitive resist 9 as a mask to prevent the bumps 8 from being altered or dissolved, and the electrical short circuit of the individual bumps 8 is cut off. Then, as shown in FIG. 21, by removing the photosensitive resist 9 covering the bumps 8,
The bump formation was completed.

By the way, in the conventional bump forming method, when the barrier metal 6 is etched, the etching also progresses laterally immediately below the bumps 8 to cause a recess 10 due to side etching as shown in FIG. Then, the etching liquid remains in the recesses 10, and the remaining etching liquid that could not be completely removed even by cleaning progresses the etching of the barrier metal 6 immediately below the bumps 8 due to aging after mounting the element, and finally the bumps 8 are peeled off. That phenomenon occurs. The etching solution remains because the bumps 8 on the barrier metal 6 are extremely thick as compared with the barrier metal 6 and pure water does not reach the depressions 10 sufficiently during cleaning of the etching solution.

[0004]

In view of the above, the present invention reduces the progress of side etching that occurs immediately below the bumps, completely removes the etching solution, and the barrier metal immediately below the bumps is etched due to aging after device mounting. Therefore, it is an object of the present invention to provide a bump forming method capable of improving the reliability of the bump by eliminating the phenomenon that the bump is peeled off.

[0005]

According to the bump forming method of the present invention for solving the above problems, in forming bumps on electrode portions of a large number of semiconductor elements formed on a wafer, first, After depositing a barrier metal on the entire surface by sputtering, apply a photosensitive resist, and then pattern the photosensitive resist so as to connect all the electrode portions on the semiconductor element through the cutting area between the semiconductor elements,
Next, the barrier metal is etched using the patterned photosensitive resist as a mask, the photosensitive resist used as the mask is peeled off, the wafer is washed with pure water, then photosensitive polyimide is applied to the entire surface, and then only the electrode portion is applied. To form openings, bumps are formed in the openings by a wet plating method using the etched barrier metal as a plating electrode, and then the wafer is heat-baked at a predetermined temperature to polyimidize the photosensitive polyimide. At the same time, the film thickness is halved, the formed bump is projected from the polyimide film, and then the barrier metal and the polyimide film on the cutting area between the semiconductor elements are cut.

[0006]

In the bump forming method of the present invention described above, when the barrier metal is etched, only the photosensitive resist having a relatively small film thickness serves as a mask, so that the side etching of the barrier metal is less advanced. In addition, since the etching solution is completely removed by cleaning the wafer with pure water after peeling the photosensitive resist, the barrier metal under the bump may be etched due to aging after mounting the element, and the bump may peel off. There is no. In addition, since the photosensitive polyimide used as a mask for plating has a film thickness reduced to half by baking, it is possible to mount an element using bumps without peeling, and in addition, it functions as a second wiring protection film. ,
Reliability is improved.

[0007]

EXAMPLE An example of the bump forming method of the present invention will be described with reference to the drawings. As shown in FIGS. 11 and 12, a plurality of cutting areas 3 are formed on a wafer 1 on an electrode portion 4 of a semiconductor element 2. In forming bumps, first, as shown in FIG. 1, a barrier metal 6 (Ti1000Å, Pd3000 from the lower layer) is formed on the entire surface of a wafer 1 on which a large number of semiconductor elements 2 are formed.
After depositing Å) by sputtering, a photosensitive resist (positive type) 11 was applied to a film thickness of 1.2 μm as shown in FIG. Next, the photosensitive resist 11 was patterned as shown in FIG. 3 so as to connect all the electrode portions 4 on the semiconductor element 2 through the cut area 3 between the semiconductor elements 2. Then, the barrier metal 6 is etched using the patterned photosensitive resist 11 as a mask as shown in FIG. 4, the photosensitive resist 11 used as a mask is peeled off as shown in FIG. 5, and the wafer 1 is washed with pure water. did. Next, as shown in FIG. 6, photosensitive polyimide (negative type) 12 was applied on the entire surface to a film thickness of 30 μm. Next, as shown in FIG. 7, the photosensitive polyimide 12 is patterned so that only the electrode portion 4 is opened, and the etched barrier metal 6 is used as a plating electrode by wet plating to form Au in the opening portion as shown in FIG. Bumps (straight type) 13 were formed. Then, put the whole wafer 1 in a furnace, raise it to 140 ° C in N ₂ atmosphere for 30 minutes, raise to 400 ° C in 60 minutes after 30 minutes in this state, and bake for 60 minutes in this state and let it cool. The photosensitive polyimide 12 was polyimidized and the thickness thereof was halved as shown in FIG. 9 so that the formed Au bump 13 was projected from the polyimide film 12 '. After that, the polyimide film 12 'and the barrier metal 6 on the cutting area 3 between the semiconductor elements 2 were cut as shown in FIG. 10 to cut off the electrical short circuit of each Au bump 13.

When the portion of the barrier metal 6 immediately below the Au bump 13 thus formed was inspected, no side etching was confirmed, and the depression 10 as in the conventional case shown in FIG.
Did not occur.

[0009]

As described above, according to the bump forming method of the present invention, there is no progress of side etching of the barrier metal immediately below the bump, and the etching solution is completely removed so that the barrier immediately below the bump changes with time after mounting the element. The phenomenon that the metal is etched and the bump is peeled off disappears. In addition, since the photosensitive polyimide used as a plating mask has a film thickness that is halved by firing, it is possible to mount an element using bumps without peeling, and as a wiring protection film for the second layer, reliability is improved. Is improved.

[Brief description of drawings]

FIG. 1 is a diagram showing a process of an embodiment of a bump forming method of the present invention.

FIG. 2 is a diagram showing a process of an embodiment of a bump forming method of the present invention.

FIG. 3 is a diagram showing steps of an embodiment of the bump forming method of the present invention.

FIG. 4 is a diagram showing steps of an embodiment of the bump forming method of the present invention.

FIG. 5 is a diagram showing steps of an embodiment of the bump forming method of the present invention.

FIG. 6 is a diagram showing steps of an embodiment of the bump forming method of the present invention.

FIG. 7 is a diagram showing steps of an embodiment of the bump forming method of the present invention.

FIG. 8 is a diagram showing steps of an embodiment of the bump forming method of the present invention.

FIG. 9 is a diagram showing steps of an embodiment of the bump forming method of the present invention.

FIG. 10 is a diagram showing a process of an embodiment of the bump forming method of the present invention.

FIG. 11 is a top view of a wafer on which a large number of semiconductor elements are formed.

12 is an enlarged perspective view showing an electrode portion of a semiconductor element on the upper surface of the wafer of FIG. 11.

FIG. 13 is a diagram showing steps of a conventional bump forming method.

FIG. 14 is a diagram showing steps of a conventional bump forming method.

FIG. 15 is a diagram showing steps of a conventional bump forming method.

FIG. 16 is a diagram showing steps of a conventional bump forming method.

FIG. 17 is a diagram showing steps of a conventional bump forming method.

FIG. 18 is a diagram showing steps of a conventional bump forming method.

FIG. 19 is a diagram showing steps of a conventional bump forming method.

FIG. 20 is a diagram showing steps of a conventional bump forming method.

FIG. 21 is a diagram showing steps of a conventional bump forming method.

[Explanation of symbols]

 1 Wafer 2 Semiconductor Element 3 Cutting Area 4 Electrode Section 5 Wiring Protective Film 6 Barrier Metal 11 Photosensitive Resist 12 Photosensitive Polyimide 12 'Polyimide Film 13 Au Bump

Claims (1)

[Claims] 1. In forming bumps on electrode portions of a large number of semiconductor elements formed on a wafer, first, a barrier metal is deposited on the entire surface of the semiconductor element by sputtering, and then a photosensitive resist is applied. The photosensitive resist is patterned so that all electrode parts on the semiconductor element are connected through the cutting area between the semiconductor elements, and the barrier metal is etched using the patterned photosensitive resist as a mask. Is removed, the wafer is washed with pure water, then photosensitive polyimide is applied to the entire surface, and then patterned so that only the electrode portion is opened. The above-mentioned etched barrier metal is used as a plating electrode for wet plating. To form a bump in the opening, then heat-bak the wafer at a specified temperature to remove the photosensitive polyimide. A bump forming method, wherein the film thickness is reduced to half and the formed bump is projected from the polyimide film, and then the barrier metal and the polyimide film on the cutting area between the semiconductor elements are cut.