Patent Application
20220399234
This disclosure relates generally to semiconductor device packaging, and more specifically, to semiconductor die singulation.
Semiconductor devices are often found in a large spectrum of electronic products—from sewing machines to washing machines, from automobiles to cellular telephones, and so on. Many of these semiconductor devices are produced in high volumes to drive costs down. Factors such as manufacturing processes may be optimized for high volumes but could adversely affect yield and reliability thus impacting product costs. As technology progresses, semiconductor manufacturers continue to seek ways to improve yield and reliability in these semiconductor devices while keeping product costs in focus.
The present invention is illustrated by way of example and is not limited by the accompanying figures, in which like references indicate similar elements. Elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale.
Generally, there is provided, a semiconductor die singulation method and apparatus for improving yield and reliability. A first trench is formed at the active side of a semiconductor wafer along singulation lanes between adjacent semiconductor die. The first trench is formed by way of an ultra-short pulse (USP) laser during a first laser ablation operation. A second trench is formed along the singulation lanes of the semiconductor wafer by way of a mechanical saw during a sawing operation. A portion of the semiconductor wafer along the singulation lanes remaining between a bottom of the second trench and backside of the wafer is removed by way of a final laser cut. The final laser cut is formed by way of an USP laser configured with a narrower laser beam during a second laser ablation operation to complete the singulation process. By completing the singulation process with the second laser ablation operation, mechanical sawing is limited to an intermediate region of the semiconductor wafer thickness thus preventing mechanical damage to the active side and backside of the plurality of singulated semiconductor die. Accordingly, yield and reliability are improved.
The semiconductor wafer 100 has an active side (e.g., major side having circuitry of the semiconductor die 102) and a backside (e.g., major side opposite of the active side). The semiconductor wafer 100 may be formed from any suitable semiconductor material, such as silicon, germanium, gallium arsenide, gallium nitride and the like. The semiconductor die 102 formed on the semiconductor wafer 100 may include any digital circuits, analog circuits, RF circuits, memory, signal processor, MEMS, sensors, the like, and combinations thereof.
In this embodiment, the width 306 is predetermined based on a width of a saw blade used in a subsequent stage of die singulation and the depth 308 is predetermined based on the depth of the BEOL region 204. For example, the width 306 may be chosen to be ˜60 microns to accommodate a ˜40 micron wide saw blade. In addition, the depth 308 may be chosen to be ˜10 microns such that the first trench 310 extends below the lowest (e.g., first) metallization layer that may be located ˜8 microns below the surface of the active side 208, for example. In other embodiments, other width 306 and depth 308 dimensions may be chosen based on other saw widths and other BEOL depths.
In this embodiment, the width 506 is predetermined based on the width of the saw blade used in the stage of die singulation depicted in
In this embodiment, after the first trench 310 is formed, the remaining depth or thickness of the semiconductor wafer is split between the sawing operation to form the second trench 408 and the second laser ablation operation to form the final cut 510. Accordingly, in some embodiments when the remaining depth is split evenly between the sawing operation and the second laser ablation operations, the depth 308 of the first trench plus the depth 406 of the second trench is greater than half of the thickness 206 of the semiconductor wafer 100.
Performing the singulation of the plurality of the semiconductor die 102 by way of the first laser ablation operation, the sawing operation, and the second laser ablation operation, as provided herein, allows for improved good die per wafer having a clean die edge without recast and eliminating yield loss due to sawing chips. For example, forming the second trench 408 below the BEOL region 204 and having the width 306 of the first trench 310 wider than the blade of the mechanical saw 402, mechanical smearing of the metallization layers of the BEOL region is avoided. And by completing the singulation process with the second laser ablation operation, mechanical sawing is limited to an intermediate region of the semiconductor wafer thickness thus preventing mechanical damage to the active side 208 or 210 backside of the plurality of the semiconductor die 102 of the semiconductor wafer 100.
Generally, there is provided, a method of semiconductor die singulation including forming a first trench along a singulation lane of a semiconductor wafer; forming a second trench along the singulation lane of the semiconductor wafer, the second trench extending from a bottom of the first trench, a portion of the semiconductor wafer remaining between a bottom of the second trench and a backside of the semiconductor wafer; and forming a cut by way of a first laser, the cut extending through the portion of the semiconductor wafer remaining between the bottom of the second trench and the backside of the semiconductor wafer to singulate die of the semiconductor wafer. The first trench may be formed on an active side of the semiconductor wafer. The first trench may extend below the back end of line (BEOL) portion of the semiconductor wafer. The second trench formed along the singulation lane of the semiconductor wafer may be formed by way of a mechanical saw. A width of the first trench may be greater than a width of the second trench. The width of the second trench may be greater than a width of the cut formed through the portion of the semiconductor wafer. The first trench formed along the singulation lane of the semiconductor wafer may be formed by way of a second laser. The first laser and the second laser each may be characterized as an ultra-short pulse laser. A depth of the first trench plus a depth of the second trench may be greater than half of a thickness of the semiconductor wafer.
In another embodiment, there is provided, a method of semiconductor die singulation including forming a first trench on an active side of a semiconductor wafer by way of a laser; forming a second trench in the semiconductor wafer, the second trench extending from a bottom of the first trench, a portion of the semiconductor wafer remaining between a bottom of the second trench and a backside of the semiconductor wafer; and forming a cut by way of the laser, the cut extending through the portion of the semiconductor wafer remaining between the bottom of the second trench and the backside of the semiconductor wafer to singulate die of the semiconductor wafer. The second trench formed in the semiconductor wafer may be formed by way of a mechanical saw. The first trench may extend below the back end of line (BEOL) portion of the semiconductor wafer. A width of the first trench may be greater than a width of the second trench. The width of the second trench may be greater than a width of the cut formed through the portion of the semiconductor wafer. The laser may be characterized as an ultra-short pulse laser. The laser may be configured to generate a first beam size when forming the first trench and configured to generate a second beam size when forming the cut, the second beam size smaller than the first beam size.
In yet another embodiment, there is provided, a method of semiconductor die singulation including forming a first trench on an active side of a semiconductor wafer by way of a first laser beam having a first beam size; forming a second trench in the semiconductor wafer by way of a mechanical saw, the second trench extending downward from a bottom of the first trench, a portion of the semiconductor wafer remaining between a bottom of the second trench and a backside of the semiconductor wafer; and forming a cut by way of a second laser beam having a second beam size, the cut extending through the portion of the semiconductor wafer remaining between the bottom of the second trench and the backside of the semiconductor wafer to singulate die of the semiconductor wafer. A width of the first trench may be greater than a width of the second trench. The width of the second trench may be greater than a width of the cut formed through the portion of the semiconductor wafer. The first laser beam and the second laser beam and may each be generated by an ultra-short pulse laser, and wherein the first beam size may be larger than the second beam size.
By now, it should be appreciated that there has been provided a semiconductor die singulation method and apparatus for improving yield and reliability. A first trench is formed at the active side of a semiconductor wafer along singulation lanes between adjacent semiconductor die. The first trench is formed by way of an ultra-short pulse (USP) laser during a first laser ablation operation. A second trench is formed along the singulation lanes of the semiconductor wafer by way of a mechanical saw during a sawing operation. A portion of the semiconductor wafer along the singulation lanes remaining between a bottom of the second trench and backside of the wafer is removed by way of a final laser cut. The final laser cut is formed by way of an USP laser configured with a narrower laser beam during a second laser ablation operation to complete the singulation process. By completing the singulation process with the second laser ablation operation, mechanical sawing is limited to an intermediate region of the semiconductor wafer thickness thus preventing mechanical damage to the active side and backside of the plurality of singulated semiconductor die. Accordingly, yield and reliability are improved.
The terms “front,” “back,” “top,” “bottom,” “over,” “under” and the like in the description and in the claims, if any, are used for descriptive purposes and not necessarily for describing permanent relative positions. It is understood that the terms so used are interchangeable under appropriate circumstances such that the embodiments of the invention described herein are, for example, capable of operation in other orientations than those illustrated or otherwise described herein.
Although the invention is described herein with reference to specific embodiments, various modifications and changes can be made without departing from the scope of the present invention as set forth in the claims below. Accordingly, the specification and figures are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of the present invention. Any benefits, advantages, or solutions to problems that are described herein with regard to specific embodiments are not intended to be construed as a critical, required, or essential feature or element of any or all the claims.
Furthermore, the terms “a” or “an,” as used herein, are defined as one or more than one. Also, the use of introductory phrases such as “at least one” and “one or more” in the claims should not be construed to imply that the introduction of another claim element by the indefinite articles “a” or “an” limits any particular claim containing such introduced claim element to inventions containing only one such element, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an.” The same holds true for the use of definite articles.
Unless stated otherwise, terms such as “first” and “second” are used to arbitrarily distinguish between the elements such terms describe. Thus, these terms are not necessarily intended to indicate temporal or other prioritization of such elements.
