1. Field of the Invention
The present invention relates to the dicing of microelectronic device wafers into individual microelectronic dice. In particular, the present invention relates to using a laser dicing in the presence of an anion plasma.
2. State of the Art
In the production of microelectronic devices, integrated circuitry is formed in and on microelectronic device wafers, which is usually comprised primarily of silicon, although other materials such as gallium arsenide and indium phosphide may be used. As shown in
After the integrated circuits 202 on the microelectronic device wafer 200 have been subjected to preliminary testing for functionality (wafer sort), the microelectronic device wafer 200 is diced (cut apart), so that each area of functioning integrated circuitry 202 becomes a microelectronic die that can be used to form a packaged microelectronic device. One exemplary microelectronic wafer dicing process uses a circular diamond-impregnated dicing saw, which travels down two mutually perpendicular sets of dicing streets 204 lying between each of the rows and columns. Of course, the dicing streets 204 are sized to allow passage of a wafer saw blade between adjacent integrated circuits 202 without causing damage to the circuitry.
As shown in
Prior to dicing, the microelectronic device wafer 200 is mounted onto a sticky, flexible tape 216 (shown in
However, in the dicing of microelectronic device wafers 200, the use of industry standard dicing saws results in a rough edge along the interconnect layer 208 and results in stresses being imposed on the interconnect layer 208. This effect is most prevalent when the interconnect layer 208 has ductile copper traces or interconnects. This rough edge and the stresses imposed is a source of crack propagation into and/or delamination of the interconnect layer 208, through the guard ring 206, and into the integrated circuitry 202 causing fatal defects.
To eliminate rough edges in the interconnect layer 208, a laser, such as a Nd:YAG Laser (amplifying medium of neodymium-doped yttrium aluminium garnate (YAG)) at 355 nm, may be used to dice the microelectronic device wafer 200 or at least ablate a trench in the interconnect layer 208 (as lasers may cut/ablate slowly through the entire thickness of the microelectronic device wafer) followed by dicing completely through the remainder of the microelectronic device wafer 200 with a standard wafer saw. However, laser ablation of silicon or silicon containing materials (such as silicon dioxide, silicon nitride, or the like, used as dielectric layers in the interconnect layer) results in elemental silicon being released (broken bonds with other chemical elements), which immediately oxidizes and deposits as debris in molten form onto the microelectronic device wafer 200. This debris can cause issues with the attachment of the final product, as it prevents the wetting of the external interconnects 220 between with the external device (not shown).
To prevent such contamination, a chemical resist or other sacrificial layer 222 is deposited over the microelectronic device wafer 200, as shown in
Therefore, it would be advantageous to develop apparatus and techniques to effectively dice microelectronic device wafers with a laser while reducing or substantially eliminating the deposition of debris on the end product microelectronic die.
While the specification concludes with claims particularly pointing out and distinctly claiming that which is regarded as the present invention, the advantages of this invention can be more readily ascertained from the following description of the invention when read in conjunction with the accompanying drawings to which:
In the following detailed description, reference is made to the accompanying drawings that show, by way of illustration, specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. It is to be understood that the various embodiments of the invention, although different, are not necessarily mutually exclusive. For example, a particular feature, structure, or characteristic described herein, in connection with one embodiment, may be implemented within other embodiments without departing from the spirit and scope of the invention. In addition, it is to be understood that the location or arrangement of individual elements within each disclosed embodiment may be modified without departing from the spirit and scope of the invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the appended claims, appropriately interpreted, along with the full range of equivalents to which the claims are entitled. In the drawings, like numerals refer to the same or similar functionality throughout the several views.
The present invention includes apparatus and methods of dicing a microelectronic device wafer by laser ablating at least an interconnect layer portion of the microelectronic device wafer in the presence of an anion plasma, wherein the anion plasma reacts with debris from the laser ablation to form a reaction gas.
The interconnect layer 108 is generally alternating layers 112 of dielectric material, including but not limited to silicon dioxide, silicon nitride, fluorinated silicon dioxide, carbon-doped silicon dioxide, silicon carbide, various polymeric dielectric materials (such as SiLK available for Dow Chemical, Midland, Mich.), and the like, and patterned electrically conductive material, including copper, aluminum, silver, titanium, alloys thereof, and the like. The methods and processes for fabricating the interconnect layer 108 as well as the minor constituent materials in the various layers thereof will be evident to those skilled in the art.
As previously discussed, a plurality of dicing streets 104 separates individual integrated circuitry 102. Generally, the dicing streets 104 run perpendicularly to separate the integrated circuitry 102 into rows and columns. At least one guard ring 106 may isolate integrated circuitry 102 from dicing streets 104, as discussed previously in relation to
One embodiment of the present invention includes using a laser, such as a Nd:YAG Laser (amplifying medium of neodymium-doped yttrium aluminium garnate (YAG)) (for example, a Model 2700 Micromachining System made by Electro Scientific Industries, Inc. of Portland, Oreg., USA), to ablate away at least a portion of the microelectronic device wafer 100 (for example ablating through the interconnect layer 108). However, this laser ablation is performed in the presence of an anion plasma. The anion plasma generation is well known in the art, wherein gases such as fluorine (F2), chlorine (Cl2), and/or the like is charged into an anion plasma (F−, Cl−, and/or the like, respectively). The specific operating parameters of a plasma generating system will vary depending on the gas used, as will be understood by those skilled in the art.
In one embodiment, as shown in
Si+4+4F−→SiF4
The resulting reaction gas 136 is simply exhausted from the system. The reaction gas 136 can, of course, recovered and reused in other microelectronic die processing steps. Naturally, this process is not limited to microelectronic device fabrication and can be applied to laser ablating any silicon containing material.
Since the laser beam 124 cuts/ablates a smooth-sided trench 142, it will not propagate cracks in or cause delamination of the layers comprising the interconnect layer 108. Although the laser can cut completely through the microelectronic device wafer 100, it is a slow process. In one embodiment, the laser ablation is discontinued after forming the trench 142 through the interconnect layer 108, as shown in
Having thus described in detail embodiments of the present invention, it is understood that the invention defined by the appended claims is not to be limited by particular details set forth in the above description, as many apparent variations thereof are possible without departing from the spirit or scope thereof.
Number | Date | Country | |
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Parent | 10742486 | Dec 2003 | US |
Child | 11145367 | Jun 2005 | US |