CONDUCTIVE VIA STRUCTURE

A conductive via structure includes a first dielectric layer, a conductive pad in the first dielectric layer, a second dielectric layer, and a redistribution layer. The second dielectric layer is disposed above the first dielectric layer and has an opening. The conductive pad is in the opening. The opening has a first width at a top surface of the second dielectric layer, a second width at a bottom surface of the second dielectric layer, and a third width between the top surface and the bottom surface of the second dielectric layer. A difference between the first and second width is in a range from about 3 um to about 6 um. The redistribution layer extends from the top surface of the second dielectric layer to the conductive pad. The third width is gradually decreased from the top surface to the bottom surface of the second dielectric layer.

BACKGROUND

Field of Invention

The present invention relates to a conductive via structure.

Description of Related Art

In the fabrication process of a redistribution layer through aluminum deposition, grands of aluminum may affect the efficiency of the subsequent process and the performance of the device. Therefore, in order to avoid formation of grains, the temperature of the aluminum deposition process may be lower. However, the lower temperature makes the thickness of the redistribution layer formed within the opening of the dielectric layer (for example, the conductive via) become thinner. Moreover, aluminum clusters may be formed at the top region of the opening, such that the aluminum deposition efficiency becomes worse. As a result, the electrical connection quality may be degraded.

On the other hand, the greater opening may provide more space for aluminum to be deposited within the opening. However, the greater size of the opening may limit the shrinkage level of the device. As a result, the fabrication of a conductive via structure cannot obey the design rule.

SUMMARY

The invention provides a conductive via structure.

In some embodiments, the conductive via structure includes a first dielectric layer, a conductive pad, a second dielectric layer, and a redistribution layer. The conductive pad is in the first dielectric layer. The second dielectric layer is disposed above the first dielectric layer and has an opening. The conductive pad is in the opening. The opening has a first width at a top surface of the second dielectric layer, a second width at a bottom surface of the second dielectric layer, and a third width between the top surface and the bottom surface of the second dielectric layer. A difference between the first width and the second width is in a range from about 3 um to about 6 um. The redistribution layer extends from the top surface of the second dielectric layer to the conductive pad. The third width is gradually decreased from the top surface of the second dielectric layer to the bottom surface of the second dielectric layer.

In some embodiments, the second dielectric layer has an oblique surface between the top surface and the bottom surface of the second dielectric layer.

In some embodiments, the first width of the opening of the second dielectric layer is greater than 8 um.

In some embodiments, the first width of the opening of the second dielectric layer is in a range from about 9 um to about 13 um.

In some embodiments, the second width of the opening of the second dielectric layer is in a range from about 3 um to about 7 um.

In some embodiments, a ratio of the first width to the second width is in a range from about 1.5 to about 2.2.

In some embodiments, the third width is smaller than the first width, and the third width is greater than the second width.

In some embodiments, the conductive pad has a recess interconnecting with the opening of the second dielectric layer.

In some embodiments, a thickness of the redistribution layer on the top surface of the second dielectric layer is in a range from about 4 um to about 5 um.

In some embodiments, the redistribution layer in the opening of the second dielectric layer has a sidewall surrounding a sub opening, and a fourth width of the sub opening is substantially the same.

In some embodiments, a thickness of the sidewall of the redistribution layer is gradually decreased from the top surface of the second dielectric layer to the bottom surface of the second dielectric layer.

In some embodiments, the second dielectric layer is a composite layer.

In the aforementioned embodiments, since the first width of the second dielectric layer is about 3 um to about 6 um greater than the second width of the second dielectric layer, clusters would not be formed at the top region of the opening during the aluminum deposition process. In other words, the portion of the redistribution layer140within the opening can be thicker. Therefore, the electrical connection quality of the conductive via structure can be improved.

DETAILED DESCRIPTION

FIG. 1is a top view of a conductive via structure100according to some embodiments of the present disclosure.FIG. 2is a cross-sectional view of the conductive via structure100taken along line2-2shown inFIG. 1. Reference is made toFIGS. 1 and 2. The conductive via structure100includes a first dielectric layer110, a second dielectric layer120, a conductive pad130, and a redistribution layer140. In some embodiments, a substrate, such as a silicon substrate, a semiconductor substrate, or the like, may be located below the first dielectric layer110to support and electrically connect to the conductive pad130. The conductive pad130is in the first dielectric layer110. The second dielectric layer120is disposed above the first dielectric layer110and has an opening OP1. The conductive pad130is in the opening OP1. The second dielectric layer120has a top surface122and a bottom surface124opposite to the top surface122. The bottom surface124is in contact with the first dielectric layer110and the conductive pad130. As shown inFIG. 2, the redistribution layer140extends from the top surface122of the second dielectric layer120to the conductive pad130.

FIG. 3is a cross-sectional view of the conductive via structure100shown inFIG. 2, in which the redistribution layer140is omitted. For clarity, the configuration of the second dielectric layer120will be described in detail. The opening OP1of the second dielectric layer120has a first width D1 at the top surface122of the second dielectric layer120and a second width D2 at the bottom surface124of the second dielectric layer120. As shown inFIG. 3, the first width D1 is greater than the second width D2. A difference between the first width D1 and the second width D2 is in a range from about 3 um to about 6 um. The second dielectric layer120has an oblique surface126between and connected to the top surface122and the bottom surface124. In other words, the opening OP1is the space formed by the oblique surface126of the second dielectric layer120. In the present embodiment, the opening OP1is rectangular, and the first width D1 and the second width D2 are the distances between two oblique surface126that are opposite to each other. In some other embodiments, the opening OP1is circular, and the first width D1 and the second width D2 are diameters of opening OP1.

In some embodiments, the second dielectric layer120is a composite layer. A material of the composite layer includes silicon oxide (SiO2) and silicon nitride (SiN). In some embodiments, a thickness of the second dielectric layer120is in a range from about 5 um to about 8 um.

In some embodiments, the first width D1 of the opening OP1of the second dielectric layer120is greater than 8 um. In some other embodiments, the first width D1 of the opening OP1of the second dielectric layer120is in a range from about 9 um to about 13 um. The second width D2 of the opening OP1of the second dielectric layer120is in a range from about 3 um to about 7 um. In some embodiments, a ratio of the first width D1 to the second width D2 is in a range from about 1.5 to about 2.2.

In the present embodiments, the opening OP1further includes a third width D3 between the top surface122and the bottom surface124of the second dielectric layer120. The third width D3 is smaller than the first width D1, and the third width D3 is greater than the second width D2. Specifically, in the present embodiment, the third width D3 is gradually decreased from the top surface122of the second dielectric layer120to the bottom surface124of the second dielectric layer120.

In some embodiments, the conductive pad130includes a recess132located below the opening OP1. In other words, the recess132of the conductive pad130is communicated with the opening OP1.

Reference is made toFIG. 2, the redistribution layer140covers the top surface122and the oblique surface126of the second dielectric layer120. Moreover, the redistribution layer140extends to the recess132of the conductive pad130, such that the redistribution layer140is electrically connected to the conductive pad130. The redistribution layer140on the top surface122of the second dielectric layer120may be electrically connected to a conductive structure, such as a solder ball, solder bump, or the like.

A portion of the redistribution layer140in the opening OP1of the second dielectric layer120has a sidewall142. The redistribution layer140has a sub opening OP2surrounded by the sidewall142. The sub opening OP2of the redistribution layer140is in the opening OP1of the second dielectric layer120. The sub opening OP2is in the opening OP1. In the present embodiment, the sub opening OP2has a fourth width D4 that is substantially the same. In other words, the inner surface140S of the redistribution layer140is substantially straight. In some other embodiments, the fourth width D4 may be gradually decreased from a top surface140T of the redistribution layer140to a bottom surface140B of the redistribution layer140. Accordingly, the fourth width D4 proximal to the top surface122of the second dielectric layer120is greater than or equal to the fourth width D4 proximal to the bottom surface124of the second dielectric layer120.

A portion of the redistribution layer140on the top surface122of the second dielectric layer120has a first thickness T1. The first thickness T1 is a distance between the top surface140T of the redistribution layer140and the top surface122of the second dielectric layer120. The thickness T1 is in a range from about 4 um to about 5 um. In some embodiments, the sidewall142of the redistribution layer140has a second thickness T2 proximal to the top surface122of the second dielectric layer120and a third thickness T3 proximal to the bottom surface124of the second dielectric layer120. Each of the second thicknesses T2 and T3 is a distance between the inner surface140S of the redistribution layer140and the oblique surface126of the second dielectric layer120. In the present embodiment, the second thickness T2 of the sidewall142of the redistribution layer140is greater than the third thickness T3 of the sidewall142of the redistribution layer140. Specifically, the thickness of the sidewall142of the redistribution layer140is gradually decreased from the top surface122of the second dielectric layer120to the bottom surface124of the second dielectric layer120.

As described above, since the first width D1 of the second dielectric layer120is about 3 um greater to about 6 um than the second width D2 of the second dielectric layer120(seeFIG. 3), the first width D1 is greater than 8 urn, the second width D2 is in a range from about 3 urn to about 7 urn, the material of the redistribution layer140(e.g., aluminum) would not be clustered at the top region of the opening OP1(seeFIG. 2). Therefore, the aluminum deposition efficiency for forming the redistribution layer140in the opening OP1may be improved, and the redistribution layer140may have a thicker sidewall142. With such configuration, the electrical connection quality of the conductive via structure100can be improved.

Specifically, since the operation temperature during the typical aluminum deposition is lower (for example, about 200° C.), there is no re-flow process employed. As a result, it's hard to form the sidewall142of the redistribution layer140with a thickness that can provide sufficient electrical connection quality. In some embodiments, in order to provide sufficient electrical connection quality between the sidewall142of the redistribution layer140and the conductive pad130, the third thickness T3 of the sidewall142may be greater than 600 nm.

For example, Table 1 shows three exemplary conductive via structures, Samples 1-3. Samples 1-3 have different first widths D1 and third thicknesses T3.

As shown in Table 1, Sample 1 has a first width D1 that is smaller than 8 um. Therefore, the third thickness T3 is smaller than 600 nm. On the other hand, Samples 2-3 each has a first width D1 that is greater than 8 um. As such, the third thicknesses T3 may be both greater than 600 nm. Moreover, as shown in Samples 1-3, the greater the first widths D1 are, the thicker the sidewalls142are formed.

Table 2 shows two exemplary conductive via structures, Samples 4-5. Samples 4-5 have different first widths D1, differences between the first width D1 and the second width D2 (D1−D2), and third thicknesses T3.

As shown in Table 2, Sample 4 and Sample 5 each has a first width D1 that is greater than 8 um and a difference between the first width D1 and the second width D2 that is greater than 3 um. Therefore, the third thicknesses T3 are both greater than 600 nm. Moreover, although the first widths D1 of Sample 4 and Sample 5 are similar, the thicknesses T3 is greater when the difference between the first width D1 and the second width D2 is greater. That is, as long as the differences between the first width D1 and the second width D2 are greater than 3 urn, the thicknesses T3 of the sidewall142can be as thick as the desired value or be thicker than the desired value (e.g., 600 nm). Therefore, the first width D1 can be smaller, for example, smaller than 13 urn. Accordingly, the minimization of the conductive via structure100can be achieved.

According to Samples 1-5, with the configurations of the second dielectric layer120described above, clusters of the redistribution layer140would not be formed at the top region of the opening OP1during the aluminum deposition process. Therefore, it is easier to deposit a thicker sidewall142of the redistribution layer140. With such configuration, the electrical connection quality of the conductive via structure100can be improved.

It is to be noted that the connection relationships of the elements described above will not be repeated in the following description, and only aspects related to another type of the second dielectric layer will be described.

FIG. 4is a cross-sectional view of a conductive via structure200according to another embodiment of the present disclosure. The conductive via structure200is similar to the conductive via structure100inFIG. 3. The difference is that a second dielectric layer220of the conductive via structure200has a top portion220A and a bottom portion220B below the top portion220A. The bottom portion220B is located between the top portion220A and the first dielectric layer110. In other words, the bottom portion220B is located between the top portion220A and the conductive pad130. The conductive via structure200has an opening OP3surrounded by the top portion220A and the bottom portion220B.

The opening OP3surrounded by the top portion220A has the first width D1 at the top surface222of the second dielectric layer220that is substantially the same as the first width D1 described in the conductive via structure100ofFIG. 1. In the present embodiment, the opening OP3in the top portion220A has a constant width.

The opening OP3surrounded by the bottom portion220B has a second width D2 at the bottom surface224of the second dielectric layer220that is substantially the same as the second width D2 described in the conductive via structure100ofFIG. 1. The opening OP3in the bottom portion220B further has a third width D3 between the top portion220A and the bottom surface224of the second dielectric layer220. The third width D3 is greater than the second width D2 and is smaller than the first width D1. In the present embodiment, the third width D3 of the opening OP3in the bottom portion220B is gradually decreased from the top portion220A to the bottom surface224of the second dielectric layer220.

Other structural details of the conductive via structure200are the same as the conductive via structure100. Accordingly, the conductive via structure200has the same advantages as the conductive via structure100, and a description will not be repeated hereinafter.