IC Microanalysis LLC – January __, 2011 IntroductionA review of US patent xxxxxxx and cursory technical research was performed in order todetermine the possible current and future product market applications and adoption for theinvention. ConclusionsThe invention is primarily focused towards product areas that require high aspect ratio etchingof materials which is of great interest in a number of product areas.Possible Product Market Applications Product Market Product Feature 3D wafer level packaging through-silicon vias multi-layered integrated circuit devices through-silicon vias power semiconductors trench (power MOSFETs) high-density DRAMs capacitor trenches CCD or CMOS image sensors Through-silicon vias microelectromechanical systems (MEMS) etching individual components o actuators o photonic devices o piezoelectronic devices solar cells through-silicon vias flat panel displays through-silicon viasMarket AdoptionThe primary current methodology for etching high-profile trenches and defining features isDeep Reactive-Ion Etching (DRIE) using the Bosch methodology. This method uses InductivelyCoupled Plasma (ICP) etchers to perform multiple etch and deposition phases, producing anearly vertically-etched pattern or trench.Some elements of the ‘xxx invention are likely used in current processes, such as pulsed RFdrive and pulsed biasing. However, the utilization of electro-negative gases and synchronizedtiming of the RF and biasing pulses does not appear to be currently used.Future market adoption within the remaining lifetime of the ‘xxx patent depends upon howwell the existing processes work with decreasing feature sizes and increasing utilization of theprocesses across more product lines. Based upon a cursory first-generation citation analysis,some aspects of the invention are seen as innovative. A more detailed analysis would berequired to determine which aspects hold the most promise.
IC Microanalysis LLC – January __, 2011A great deal of research is on-going to develop better methods for high-aspect ratio etching.Some of these are focused on the utilization of electro-negative gases (primarily halogen) andminimizing the electrons to obtain ion-ion plasmas.The primary inventive aspect of the ‘xxx is the synchronized timing of the RF and biasing pulsesto enable the most efficient ion-ion etching with the addition of an electro-negative gas. Toproduce both positive and negative ions the timing of the pulses in relation to each other arecritical. No research papers were found that indicated anyone else was working on processesthat produced both types of ions, except for those of the patents author. Based upon thelimited forward citations, the apparent lack of similar research in the critical areas covered bythis patent during the first ten years of the patents’ life, and the success of current applications,it is speculated that at this specific time the chance of market adoption of the ‘xxx invention islow.However, it should be understood that some of the defined product markets are still in theirearly stages of development and growth, so innovative new processes are regularly beingdeveloped. In addition, existing inventions that may have application to these markets are likelyto be incorporated as these technologies evolve. The ‘xxx invention is generally focused on anarea of technology (high aspect ratio etching) that is of growing interest and utilization in manyof these product markets. So currently unforeseen problems in any of these market areas mayrequire solutions that may be addressed by the ‘xxx invention, potentially increasing its value. DiscussionBrief Patent OverviewThe USPxxxxxxx invention describes a plasma etching system using ion-ion (electron-free)plasmas, an electro-negative gas, and synchronized RF drive and substrate bias timing.The primary inventive element is the synchronization of a substrate bias waveform to a pulsedRF drive. A delay is included between the end of the RF drive pulse and the start of the biaspulse to allow the electron population to drop to approximately zero. By using a source gasmixture which has highly electro-negative components, substrate bombardment with negativeions can be achieved. Inductively-coupled RF drive is used for plasma generation in thepreferred embodiment.Possible Product ApplicationsThe invention is primarily focused towards applications that require high-aspect ratio etching ofmaterials. These include MEMs components and through-silicon vias for 3D wafer levelpackaging, multi-layered integrated circuits, solar cells, image sensor chips, and flat-paneldisplays. Possible applications also include trenches in power MOSFETs and capacitor trenchesin high density DRAMs. Many of these product area applications are still in their infancy, and
IC Microanalysis LLC – January __, 2011therefore enjoy extensive research and development efforts in both industry and universityenvironments.Similar Current Applications and EquipmentThe primary current methodology for etching high-profile trenches and defining features forMEMs devices is the Deep Reactive-Ion Etching (DRIE). This methodology uses two primarytechnologies, Bosch and Cryogenic. The Bosch method has gained favor for current productmanufacturing and is widely utilized in many of the product application areas described above.The method uses multiple etch and deposit phases to produce a nearly isotropic etched patternor trench. DRIE etchers are currently available from a number of manufacturers and are usedextensively in the MEMs industry and are becoming the favored methodology for through-silicon vias.Inductively-coupled RF drive with pulsing of the drive voltage and substrate bias is currentlyused for plasma generation in DRIE equipment. Tegal has an extensive line of DRIE equipment(http://www.tegal.com/default.aspx). Cursory technical research did not find any evidence thatthese systems utilized an electro-negative gas or synchronization of the RF drive pulses with thesubstrate bias pulses as required by some of the invention claims. However, application notesdid show pulsing of the bias supply to help prevent notching at the silicon dioxide interface –(http://www.tegal.com/applicationdetail.aspx?applicationID=13).Yield Engineering Systems currently produces plasma cleaning systems that have “electron-free” operating modes, but detailed inspection of the systems drive and biasing systems wasbeyond the scope of this analysis. An associated Application Note is shown at this link:http://www.bita.lu/datasheets/GT-AN-125-LU.pdfA more detailed investigation into current processes and equipment should be considered toestablish which elements of the ‘xxx may already be utilized.
IC Microanalysis LLC – January __, 2011Cursory Patent Innovation and Citation AnalysisWith a filing date of xxxxx, the ‘xxx invention still has a good lifetime value. A number ofapplication areas are heavily researched so development of new methodologies is ongoing.Examinations of the ‘xxx first generation forward citations using the USPTO online databaseshows only these three citing patents: USPxxxxxxx – Assignee: US Navy USPxxxxxxx – Assignee: Hitachi USPxxxxxxx – Assignee: Silicon GenesisComparing these citations to USPxxxxxxx referenced by the inventor in the ‘xxx Background andSummary, we find that the ‘xxx patent currently has thirty-six first generation forward citations.The original file date of the ‘xxx is October 1996, so it is approaching the end of its useful life.However, a cursory search shows the inventor has a number of more recent patents with betterlifetime value and somewhat similar inventive features, including: USPxxxxxxx USPxxxxxxx USPxxxxxxxThe number of forward citations is sometimes indicative of the innovative nature of theinvention. In this case, the significantly higher citation rate for the ‘xxx may mean the inventivemethodology described may be more innovative and more likely to see in current and/or nearfuture utilization in products than the ‘xxx.However, the ‘xxx incorporates many of the elements of the ‘xxx, and synchronization of thesupply and bias signals may be relatively easy to implement. Therefore, the improved etchingsaid to be produced by the inventive features in the ‘xxx may be recognized as having a highervalue in the future as feature sizes decrease.
IC Microanalysis LLC – January __, 2011 Independent Claims - Element Similarity Table Claim 1 (least limiting) Claim 14 Claim 19 Claim 27A method for plasma A method for surface A method for plasma A method for plasmaprocessing, comprising the modification by negative processing, comprising the processing, comprising thesteps of: ion bombardment, steps of: actions of: comprising the steps of: applying power pulses defining an intensity modulation waveform to a chambergenerating a substantially generating approximately generating an electron-electron-free ion-ion equal populations of free ion-ion plasmaplasma positive and negative ionsin proximity to at least one in proximity to a in proximity to at least firstsubstrate substrate and second substratesapplying a bias signal having applying a bias signal applying a bias signal having applying differentsignal components of having signal components alternating positive and respective bias signals toalternating positive and of alternating positive negative polarities to a said substratesnegative polarities to said and negative polarities substrate, said bias signalsubstrate defining an envelope and imposing a delay between at least some trailing edges of said modulation waveform and the respective next leading edges of said bias signal envelopeat times when said ion-ion during time periods when at times when said ion-ionplasma is present the number of free plasma is present electrons proximate to said substrate is less than a specified fraction of the number of ions in one of said populationsto induce bombardment of to induce bombardment to induce bombardment ofsaid substrate by both of said substrate by ions said first substrate by ionsnegative and positive ions of both said populations of desired chemistry and energy, with substantially no electron bombardment said delay being sufficient to cause the free electron density to become less than a specified fraction of the positive ion density inside said chamber to regulate the voltage and/or composition of said plasma by ion bombardment of said second substrate