阅读说明：本技术 一种导电柱的激光形成方法 (Laser forming method of conductive column ) 是由 陈洁 于 2021-01-19 设计创作，主要内容包括：本发明提供了一种导电柱的激光形成方法,其利用激光对导电柱的第二端进行局部退火工艺,以形成具有保形功能和防止漏电功能的金属硅化物层,然后再进行刻蚀形成露头结构。后续在导电柱的第二端形成焊球时,该金属硅化物的硅材料进入焊球中可以保证焊球的接合可靠性且能够抑制氧化。(The invention provides a laser forming method of a conductive column, which utilizes laser to carry out local annealing process on a second end of the conductive column so as to form a metal silicide layer with the functions of shape keeping and electric leakage prevention, and then carries out etching to form an exposed structure. When a solder ball is formed at the second end of the conductive post, the silicon material of the metal silicide enters the solder ball, so that the bonding reliability of the solder ball can be ensured, and the oxidation can be inhibited.)

1. A laser forming method of a conductive column comprises the following steps:

(1) providing an intermediate plate made of silicon material, wherein the intermediate plate is provided with a first surface and a second surface which are opposite;

(2) forming a plurality of conductive pillars in the interposer, first ends of the plurality of conductive pillars being exposed from the first surface, the plurality of conductive pillars having a first aperture;

(3) forming a redistribution layer on the first surface to electrically connect the plurality of conductive pillars;

(4) turning over the interposer and grinding the second surface to expose the second ends of the conductive posts;

(5) respectively irradiating the second ends of the conductive pillars with a laser beam, wherein the diameter of the laser beam is larger than the first aperture, so as to form a metal silicide layer on the side walls of the second ends of the conductive pillars;

(6) continuing to etch the second surface so that second ends of the plurality of conductive pillars protrude from the second surface to form outcrop portions;

(7) and forming a plurality of solder balls on the second ends of the plurality of conductive columns and reflowing so that the solder balls at least comprise silicon.

2. The laser forming method of a conductive post according to claim 1, wherein: between step (6) and step (7), further comprising: a passivation layer is covered on the second surface, and a plurality of openings exposing the second ends of the plurality of conductive pillars are formed in the passivation layer.

3. The laser forming method of a conductive post according to claim 2, wherein: wherein the plurality of openings completely expose the outcropping portion.

4. The laser forming method of a conductive post according to claim 1, wherein: in step (6), when the exposed portion is formed, the sidewall of the conductive pillar under the exposed portion further has a portion of the metal silicide layer thereon.

5. The laser forming method of a conductive post according to claim 1, wherein: the spot area of the laser beam on the second surface is 1.1-1.2 times of the projection area of the conductive column on the second surface.

6. The laser forming method of a conductive post according to claim 1, wherein: the conductive post is formed by electroplating and comprises electroplated copper, electroplated nickel and the like.

7. The laser forming method of a conductive post according to claim 1, wherein: the redistribution layer includes a plurality of stacked routing layers and a plurality of dielectric layers.

Technical Field

The invention relates to the field of semiconductor workpiece packaging test, in particular to a laser forming method of a conductive column.

Background

In the fabrication of interposers or interposers, the formation of conductive posts requires the provision of an exposed structure for the purpose of reliability of electrical connection. However, the exposed structure of the conductive pillar protruding from the surface of the interposer or interposer is prone to be deformed during and after etching, and is also prone to cause a problem of leakage due to diffusion of the material of the conductive pillar to the surroundings.

Disclosure of Invention

Based on solving the above problems, the present invention provides a laser forming method of a conductive pillar, including the following steps:

(1) providing an intermediate plate made of silicon material, wherein the intermediate plate is provided with a first surface and a second surface which are opposite;

(2) forming a plurality of conductive pillars in the interposer, first ends of the plurality of conductive pillars being exposed from the first surface, the plurality of conductive pillars having a first aperture;

(3) forming a redistribution layer on the first surface to electrically connect the plurality of conductive pillars;

(4) turning over the interposer and grinding the second surface to expose the second ends of the conductive posts;

(5) respectively irradiating the second ends of the conductive pillars with a laser beam, wherein the diameter of the laser beam is larger than the first aperture, so as to form a metal silicide layer on the side walls of the second ends of the conductive pillars;

(6) continuing to etch the second surface so that second ends of the plurality of conductive pillars protrude from the second surface to form outcrop portions;

(7) and forming a plurality of solder balls on the second ends of the plurality of conductive columns and reflowing so that the solder balls at least comprise silicon.

According to the embodiment of the invention, between the step (6) and the step (7), the method further comprises the following steps: a passivation layer is covered on the second surface, and a plurality of openings exposing the second ends of the plurality of conductive pillars are formed in the passivation layer.

According to an embodiment of the present invention, wherein the plurality of openings completely expose the outcropping portion.

According to the embodiment of the present invention, in the step (6), when the exposed portion is formed, the sidewall of the conductive pillar located below the exposed portion further has a portion of the metal silicide layer thereon.

According to the embodiment of the invention, the spot area of the laser beam on the second surface is 1.1-1.2 times of the projection area of the conductive pillar on the second surface.

According to an embodiment of the present invention, the conductive pillar is formed by electroplating and includes copper electroplating, nickel electroplating, and the like.

According to an embodiment of the present invention, the redistribution layer includes a plurality of stacked routing layers and a plurality of dielectric layers.

The invention has the following advantages: the invention uses laser to carry out local annealing process on the second end of the conductive column to form a metal silicide layer with shape-preserving function and electric leakage preventing function, and then carries out etching to form an exposed structure. When a solder ball is formed at the second end of the conductive post, the silicon material of the metal silicide enters the solder ball, so that the bonding reliability of the solder ball can be ensured, and the oxidation can be inhibited.

Drawings

Fig. 1-7 are schematic diagrams of a laser forming method of a conductive pillar of the present invention.

Detailed Description

The invention aims to provide a laser forming method of a conductive column with both shape keeping function and electric leakage prevention function.

Referring to fig. 1 to 7, the laser forming method of the conductive post of the present invention includes the steps of:

referring to fig. 1, an interposer 1 made of silicon material is provided, where the interposer 1 has a first surface and a second surface opposite to each other. The silicon material may be a polycrystalline silicon or a single crystal silicon material, and the interposer 1 may have a thickness of 1-5 mm. The interposer 1 should have a certain rigidity as an interposer.

Next, a plurality of conductive pillars 2 are formed in the interposer 1, first ends of the plurality of conductive pillars 2 are exposed from the first surface, and the plurality of conductive pillars 2 have a first aperture. The plurality of conductive posts 2 may be formed by forming blind vias by laser ablation on the first surface of the interposer 1 and filling the vias with a plating metal material, preferably nickel plating or copper plating.

Referring to fig. 2, a redistribution layer 3 electrically connecting the plurality of conductive pillars 2 is formed on the first surface of the interposer 1. The redistribution layer 3 may include a plurality of wiring layers and a plurality of dielectric layers (not shown) stacked, wherein the plurality of wiring layers may be formed by CVD, PVD, magnetron sputtering, or the like, and the plurality of dielectric layers may be formed by a method selected from PECVD, magnetron sputtering methods.

Referring to fig. 3, the interposer 1 is turned over, and the second surface of the interposer 1 is ground, so that the second ends of the conductive pillars 2 are exposed. The polishing can be performed by a conventional CMP process, and may further include a cleaning step such as acid washing, water washing, etc. to ensure flatness of the second surface.

Referring to fig. 4, the second ends of the conductive pillars 2 are respectively irradiated with a laser beam having a diameter larger than the first aperture to form a metal silicide layer 4 on sidewalls of the second ends of the conductive pillars 2. The metal silicide layer 4 is located between the conductive pillar 2 and the interposer 1, and is not easily etched away by a subsequent wet etching process. The energy of the laser beam should be higher than the critical temperature for forming the metal silicide 4, which may be determined according to the material of the conductive pillar 2. The generation of the laser beam may be performed by a he — ne laser or a carbon dioxide laser, and in order not to affect the material of the other interposer 1 on the second surface, the spot area of the laser beam on the second surface is 1.1-1.2 times the projection area of the conductive post 2 on the second surface.

Specifically, the laser beam irradiation process makes the top of the second end of the conductive post 2 have a round curved surface. A portion of the curved surface is covered by a metal silicide layer 4, which ensures the silicon content in the subsequent solder ball.

Referring to fig. 5, the etching of the second surface is continued so that the second ends of the plurality of conductive pillars 2 protrude from the second surface to form an outcrop portion. The outer side wall of the outcrop structure is completely wrapped by the metal silicide 4, so that the outcrop structure is conformal and can prevent the problem of electric leakage. Further, after etching, the metal silicide 4 also has a portion between the conductive post 2 and the intermediate plate 1, which portion can ensure good bonding reliability and leakage resistance.

Referring to fig. 6, a passivation layer 5 is covered on the second surface, and the passivation layer 5 may be a polymer material or an inorganic material, such as polyimide or silicon nitride. And, a plurality of openings 6 exposing second ends of the plurality of conductive pillars 2 are formed in the passivation layer 5. The second plurality of openings 6 expose at least a portion of the metal silicide layer 4, and preferably the first plurality of openings completely expose the exposed portion to ensure that more silicon can subsequently enter the solder balls.

Referring to fig. 7, a plurality of solder balls 7 are formed on the second ends of the conductive pillars 2 and reflowed, so that the solder balls 7 are mixed with a portion of the metal silicide layer 4, and at this time, the solder balls 7 at least include silicon. The solder balls 7 may be lead-tin solder, which comprises silicon, which ensures the reliability of the solder balls 7.

The invention uses laser to carry out local annealing process on the second end of the conductive column 2 to form a metal silicide layer 4 with shape-preserving function and electric leakage preventing function, and then carries out etching to form an outcrop structure. When the solder ball 7 is formed at the second end of the conductive pillar 2, the silicon material of the metal silicide layer 4 enters the solder ball, so that the bonding reliability of the solder ball 7 can be ensured and the oxidation can be inhibited.

Finally, it should be noted that: it should be understood that the above examples are only for clearly illustrating the present invention and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications of the invention may be made without departing from the scope of the invention.