METHOD TO IMPROVE CMP SCRATCH RESISTANCE FOR NON PLANAR SURFACES
An electronic device is formed by providing a substrate having a recess at a top surface. A layer of an organic protective material is formed over the substrate, with the organic protective material extending into the recess. A polishing process is performed on the layer of protective material. The polishing process may remove a portion of an underlying metal layer over the top surface while protecting the underlying metal layer within the recess.
Under 35 U.S.C. § 120, this continuation application claims the benefit of and priority to U.S. patent application Ser. No. 14/818,275, filed Aug. 4, 2015, now issued as U.S. Pat. No. 9,604,338, the entirety of which is hereby incorporated herein by reference. This application is further related to U.S. patent application Ser. No. 15/434,406, a divisional of Ser. No. 14/818,275, which has been allowed and is incorporated herein by reference in its entirety.
FIELD OF THE INVENTIONThis invention relates to the field of microelectronic devices. More particularly, this invention relates to fabrication methods of microelectronic devices.
BACKGROUND OF THE INVENTIONSome integrated circuits have a protective overcoat (PO) layer over a top metallization layer containing bond pads, with openings in the PO layer exposing the bond pads. The integrated circuits are fabricated by forming a metal liner, suitable for wire bonding, over the PO layer, extending into the PO layer openings and onto the exposed bond pads. The metal liner over the top surface of the PO layer is subsequently removed by a chemical mechanical polish (CMP) process, leaving the metal liner on the bond pads. The CMP process uses a slurry with abrasive particles and corrosive chemicals to remove the metal liner; the abrasive particles and corrosive chemicals attack the metal liner on the bond pads, causing corrosion of the bond pads and reliability problems for the integrated circuit.
Increasing the thickness of the metal liner increases the cost and complexity of the deposition process and the CMP process, and has not demonstrated desired reduction of damage to the metal liner from the CMP slurry. Adding additional pattern steps or plating processes to protect the metal liner also undesirably increase the fabrication cost and complexity. Using thicker top metal increases the difficulty of patterning and limits the minimum features and line separations.
SUMMARY OF THE INVENTIONThe following presents a simplified summary in order to provide a basic understanding of one or more aspects of the invention. This summary is not an extensive overview of the invention, and is neither intended to identify key or critical elements of the invention, nor to delineate the scope thereof. Rather, the primary purpose of the summary is to present some concepts of the invention in a simplified form as a prelude to a more detailed description that is presented later.
A microelectronic device is formed by forming a PO layer over an interconnect region with a bond pad so that the PO layer has an opening which forms a recess; the bond pad being exposed in the recess. A metal liner is formed over the PO layer, extending into the recess and onto the bond pad. A protective layer is formed over the metal liner, extending into the recess. A CMP process removes the protective layer and the metal liner from over the top surface of the PO layer, leaving the protective layer and the metal liner in the recess. The protective layer is subsequently removed from the recess, leaving the metal liner in the recess over the bond pad.
A microelectronic device is formed by providing a substrate having a recess at a top surface, and a liner layer formed over the top surface of the substrate, extending into the recess. A protective layer is formed over the liner layer, extending into the recess. A CMP process removes the protective layer and the liner layer from over the top surface of the substrate, leaving the protective layer and the liner layer in the recess. The protective layer is subsequently removed from the recess, leaving the liner layer in the recess.
The present invention is described with reference to the attached figures. The figures are not drawn to scale and they are provided merely to illustrate the invention. Several aspects of the invention are described below with reference to example applications for illustration. It should be understood that numerous specific details, relationships, and methods are set forth to provide an understanding of the invention. One skilled in the relevant art, however, will readily recognize that the invention can be practiced without one or more of the specific details or with other methods. In other instances, well-known structures or operations are not shown in detail to avoid obscuring the invention. The present invention is not limited by the illustrated ordering of acts or events, as some acts may occur in different orders and/or concurrently with other acts or events. Furthermore, not all illustrated acts or events are required to implement a methodology in accordance with the present invention.
In the instant example, the bond pads 116 are formed by a single damascene copper process, so that top surfaces 118 of the bond pads 116 are substantially coplanar with a top surface 120 of the dielectric material 108. A PO layer 122 is formed over the top surfaces 118 of the bond pads 116 and the top surface 120 of the dielectric material 108. The PO layer 122 includes one or more layers of dielectric material, such as silicon dioxide, silicon nitride, silicon oxynitride, polyimide and/or other dielectric material. The PO layer 122 is patterned to have recesses 124 which expose portions of the top surfaces 118 of the bond pads 116. The recesses 124 may have widths 126 of, for example, 50 microns to 150 microns, to accommodate typical wire bonds to the bond pads 116. Depths 128 of the recesses 124, which corresponds to a thickness of the PO layer 122, may be, for example, 2 microns to 4 microns. In the instant example, a top surface 130 of the PO layer 122 is substantially planar over the microelectronic device 100 outside of the recesses 124.
A metal liner 132 is formed over the PO layer 122, extending into the recesses 124 and onto the exposed portions of the top surfaces 118 of the bond pads 116. The metal liner 132 on the top surface 118 of the bond pads 116 in the recesses 124 is below the top surface 130 of the PO layer 122 adjacent to the recesses 124. The metal liner 132 may be a layer stack including an adhesion layer 134 contacting the bond pads 116 and a bond layer 136 providing a bonding surface. The adhesion layer 134 may include, for example, titanium, titanium nitride, titanium tungsten, tantalum, tantalum nitride, chromium or nickel. The bond layer 136 may include, for example, aluminum, palladium, ruthenium, platinum, or gold. The metal liner 132 may optionally include one or more metal layers, such as palladium, aluminum or nickel, between the adhesion layer 134 and the bond layer 136. The metal liner 132 may be 100 nanometers to 3 microns thick, advantageously providing low process cost for the metal liner 132 formation compared to thicker metal liners. The layers of the metal liner 132 may be formed by any combination of sputtering, evaporation, electroplating, electroless plating, ALD, reactive sputtering, MOCVD or other thin film formation method.
A layer of protective material 138 is formed over the metal liner 132. In the instant example, the layer of protective material 138 may be an organic polymer material such as photoresist or novolac resin, mixed with a solvent. The layer of protective material 138 may be dispensed in a thick layer which fills the recesses 124, as part of a spin coat process. The layer of protective material 138 may be a material which is used in other processes in the fabrication sequence for the microelectronic device 100, and the method of forming the layer of protective material 138 may use equipment which is used in other processes in the fabrication sequence for the microelectronic device 100, thus advantageously eliminating a need to install dedicated equipment and provide dedicated material to form the layer of protective material 138.
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In the instant example, the bond pads 216 are formed by an etch-defined process, so that top surfaces 218 of the bond pads 216 are higher than a top surface 220 of the dielectric material 208. A PO layer 222, comprising a first PO sub-layer 248 and a second PO sub-layer 250, is formed over the top surfaces 218 of the bond pads 216 and the top surface 220 of the dielectric material 208. The first PO sub-layer 248 includes one or more layers of inorganic dielectric material, such as silicon dioxide, silicon nitride and/or silicon oxynitride. The second PO sub-layer 250 is formed over the first PO sub-layer 248. The second PO sub-layer 250 includes organic dielectric material such as polyimide. The PO layer 222 is patterned to have recesses 224 which expose portions of the top surfaces 218 of the bond pads 216 and the dummy bond pads 246. In the instant example, a top surface 230 of the PO layer 222 is not planar over the microelectronic device 200 outside of the recesses 224.
A metal liner 232 is formed over the PO layer 222, extending into the recesses 224 and onto the bond pads 216 and dummy bond pads 246. The metal liner 232 on the top surface 218 of the bond pads 216 and dummy bond pads 246 in the recesses 224 is below the top surface 230 of the PO layer 222 adjacent to the recesses 224. The metal liner 232 may be a single metal layer or layer stack including an adhesion layer and a bond layer. The metal liner 232 may include, for example, the metals listed in reference to
A first sub-layer 252 of a layer of protective material 238 is formed over the metal liner 232. In the instant example, the first sub-layer 252 may be an organic polymer material, mixed with a solvent. The first sub-layer 252 may be applied by a first spray process 254; the first sub-layer 252 extends into the recesses 224 and onto the bond pads 216 and the dummy bond pads 246. Spray application of the first sub-layer 252 may advantageously provide more uniform coverage for a large or irregularly shaped substrate 202 compared to spin coating. The first sub-layer 252 may use material and equipment which are used in other processes in the fabrication sequence for the microelectronic device 200, accruing the advantage discussed in reference to
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A liner layer 332 is formed over the top surface 320 of the substrate 302, extending into the recesses 324. The liner layer 332 may be one or more layers of metal, semiconductor or dielectric material. The liner layer 332 may be formed, for example, by any combination of sputtering, evaporation, electroplating, ALD, reactive sputtering, MOCVD, or vapor phase transfer. In the instant example, the liner layer 332 does not fill the recesses 324.
A layer of protective material 338 is formed over the liner layer 332, covering the liner layer 332 in the recesses 324. The layer of protective material 338 may include one or more layers of material, such as photoresist, resin, or polymer, possibly mixed with a solvent to obtain a desired thickness. The layer of protective material 338 may be formed, for example, by spin coating, spray or vapor phase transfer. The layer of protective material 338 may be baked, cured or otherwise treated to remove solvent and obtain a desired CMP removal rate. In the instant example, the layer of protective material 338 is not patterned through a process using a photolithographic operation, advantageously reducing fabrication cost and complexity of the microelectronic device 300.
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While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only and not limitation. Numerous changes to the disclosed embodiments can be made in accordance with the disclosure herein without departing from the spirit or scope of the invention. Thus, the breadth and scope of the present invention should not be limited by any of the above described embodiments. Rather, the scope of the invention should be defined in accordance with the following claims and their equivalents.
Claims
1. A method of forming an electronic device, comprising:
- providing a substrate having a recess in a top surface of the substrate;
- forming a layer of an organic protective material over the substrate, the layer of organic protective material extending into the recess and covering the top surface;
- performing a polishing process on the layer of protective material.
2. The method of claim 1, wherein the layer of protective material comprises photoresist.
3. The method of claim 1, wherein the layer of protective material comprises a resin.
4. The method of claim 1, wherein the layer of protective material comprises polymer.
5. The method of claim 1, wherein the layer of protective material comprises a material mixed with a solvent.
6. The method of claim 5, wherein the layer of protective material is treated to remove solvent.
7. The method of claim 1, wherein forming a layer of an organic protective material includes spin-coating the organic protective material onto the top surface.
8. The method of claim 1, wherein the top surface of the substrate comprises a dielectric material.
9. The method of claim 1, wherein the polishing processes comprises chemical-mechanical polishing.
10. The method of claim 1, wherein a metal layer is located over the substrate surface and within the recess prior to forming a layer of an organic protective material over the substrate, and the polishing process removes the metal layer from over the top surface and leaves a remaining portion of the metal layer within the recess.
11. The method of claim 10, wherein the metal layer comprises a first metal sublayer and a different second metal sublayer.
12. The method of claim 10, wherein the remaining portion is conductively coupled to an underlying electronic circuit.
13. The method of claim 10, wherein the protective material has a higher removal rate than does the metal layer for the polishing process.
14. The method of claim 10, wherein the remaining portion is located directly on a copper pad.
15. The method of claim 14, wherein the copper pad is a dummy bond pad.
16. A method of forming an electronic device, comprising:
- providing a substrate having a recess in a top surface of the substrate;
- forming a layer of an organic protective material over the substrate, the layer of organic protective material extending into the recess and covering the top surface;
- performing a polishing process on the layer of protective material, thereby removing a portion of an underlying metal layer located over the top surface while protecting the underlying metal layer within the recess.
Type: Application
Filed: Sep 5, 2018
Publication Date: Jan 3, 2019
Inventors: Jonathan Philip Davis (Allen, TX), Andrew Frank Burnett (Plano, TX), Brian Edward Zinn (Lucas, TX)
Application Number: 16/121,666