International Business Machines Corporation

Ravindra V Shenoy

Madhav Datta

John Michael Cotte

Leping Li

Steven G Barbee

Thomas Safron Kanarsky

Eugene Henry Ratzlaff

Tony F Heinz

Thomas E Dinan

Lubomyr Taras Romankiw

Gangadhara Swami Mathad

Michael B Pike

Kirk G Berridge

A primary lithium battery particularly adapted for use in self-contained self-powered devices (SSPD) for mobile communication and computing products, such as radio frequency identification tags, PCMCIA cards, and smart cards. The battery has a flexible and compact design, and utilizes a solid polymer electrolyte membrane that preferably has a polyacrylonitrile matrix. Performance of the electrolyte membrane is optimized by controlling the amount of aprotic organic solvents within the membrane within a prescribed range of ratios. In so doing, the performance characteristics of the battery closely approximate that of conventional liquid electrolytes without the safety hazards associated with the risk of liquid electrolyte leakage, and exhibit enhanced performance at sub-ambient temperatures. A further feature is that the battery's cathode is encapsulated within a polymeric matrix that eliminates the exposure hazard posed by lithium intercalation compounds used within the cathode.

Lithium polymer electrolyte battery for sub-ambient temperature

The present invention relates to a chemical etchant for etching metals in the presence of one or more metals not to be etched, the etchant comprising 10-25 gms EDTA, 15-35 gms K.sub.2 HPO.sub.4 and 25-45 gms oxalic acid in a liter of 30% H.sub.2 O.sub.2. More particularly, in the fabrication of interconnections for microchip structures, the present invention addresses the removal of intermediate adherent layers, e.g., Ti--W, without damaging other microchip structures made of other metals, such as Al or Al--Cu test pads; Cu and phased Cr--Cu layers; and Sn--Pb solder bumps. The use of potassium phosphate in the hydrogen peroxide+EDTA bath has been found to significantly reduce the attack on the metal not to be etched. Furthermore, the use of oxalic acid in the bath prevented the deposition of tin oxide on the substrate adherent layer metal, thus facilitating its complete removal.

Selective chemical etching in microelectronics fabrication

A chemical etchant for the removal of titanium-tungsten containing structures from the semiconductors and a method for removing the titanium-tungsten. The etchant comprising a solution of hydrogen peroxide, a salt of EDTA, and an acid, the acid capable of preventing the deposition of tin oxide. The method of removal comprises first obtaining a wafer containing titanium-tungsten. Second, immersing the wafer having titanium-tungsten thereon for a predetermined period of time in an etchant bath comprising a solution of hydrogen peroxide, a salt of EDTA and an acid, the acid capable of preventing the deposition of tin oxide. Third, removing the treated wafer and rinsing the treated wafer and lastly, drying the wafer.

Etching of Ti-W for C4 rework

In through-mask electroetching of a metal film on top of an insulating substrate, the shape of the metal film being etched is a function of the mask opening, the spacing between the openings and the thickness of the mask. An analysis of the electric field around the mask and the metal film is used to determine conditions leading to the formation of islands of unetched metal films within the openings. The analysis is then used to design the mask pattern and eliminate these islands. The increase in the ratio of the mask thickness to the opening width for eliminating the islands also lowers the undercutting of the mask. Premature stoppage of the electroetching process arising from the isolation of the sample film from the contact is also addressed. The electrical contact to the sample is made at one end and a nozzle jet of electrolyte is slowly swept from the far end of the sample towards the electrical contact. The nozzle speed is matched with the metal removal rate and the electrical contact is exposed to the electrolyte at the end of the process.

Elimination of island formation and contact resistance problems during

A method is provided for making a flexible primary battery suitable for microelectronics applications, and more particularly, for use with self-contained self-powered portable devices (SSPD) such as RF-ID tags. The method generally employs photolithography and etching techniques to minimize the thicknesses of metal foils required in the structure of the battery, as well as packaging methods which yield a flexible and durable battery having a thickness of not more than about 0.5 millimeter, and preferably about 0.3 millimeter or less, and a relatively small size on the order of a few square centimeters in surface area.

Method for making a thin flexible primary battery for microelectronics

A tool and process for electroetching metal films or layers on a substrate employs a linear electrode and a linear jet of electrolyte squirted from the electrode. The electrode is slowly scanned over the film by a drive mechanism. The current is preferably intermittent. In one embodiment a single wafer surface (substrate) is inverted and the jet is scanned underneath. In another embodiment wafers are held vertically on opposite sides of a holder and two linear electrodes, oriented horizontally and on opposite sides of the holder, are scanned vertically upward at a rate such that the metal layers are completely removed in one pass. The process is especially adapted for fabricating C4 solder balls with triple seed layers of Ti--W (titanium-tungsten alloy) on a substrate, phased Cr--Cu consisting of 50% chromium (Cr) and 50% copper (Cu), and substantially pure Cu. Solder alloys are through-mask electrodeposited on the Cu layer. The seed layers conduct the plating current. During etching the seed layers are removed between the solder bumps to isolate them. The phased Cr--Cu and Cu layers are removed by a single electroetching operation in aqueous potassium sulfate and glycerol with cell voltage set to dissolve the phased layer more quickly than the Cu, avoiding excessive solder bump undercutting in the copper layer. The cell voltage may be such that the solder bump is only slightly undercut so as to form a stepped base C4 structure upon reflowing. Ti--W is removed by a chemical process.

Electroetching method and apparatus

A nozzle is provided for use in electroetching a vertically oriented workpiece, comprising a housing having a top, sides, and bottom for creating a flow of etching solution on the workpiece, and means for shaping the flow of etching solution into a moving channel to improve etch uniformity of the workpiece.

Vertical electroetch tool nozzle and method

A tool and process for electroetching metal films or layers on a substrate employs a linear electrode and a linear jet of electrolyte squirted from the electrode. The electrode is slowly scanned over the film by a drive mechanism. The current is preferably intermittent. In one embodiment a single wafer surface (substrate) is inverted and the jet is scanned underneath. In another embodiment wafers are held vertically on opposite sides of a holder and two linear electrodes, oriented horizontally and on opposite sides of the holder, are scanned vertically upward at a rate such that the metal layers are completely removed in one pass. The process is especially adapted for fabricating C4 solder balls with triple seed layers of Ti-W (titanium-tungsten alloy) on a substrate, phased Cr-Cu consisting of 50% chromium (Cr) and 50% copper (Cu), and substantially pure Cu. Solder alloys are through-mask electrodeposited on the Cu layer. The seed layers conduct the plating current. During etching the seed layers are removed between the solder bumps to isolate them. The phased Cr-Cu and Cu layers are removed by a single electroetching operation in aqueous potassium sulfate and glycerol with cell voltage set to dissolve the phased layer more quickly than the Cu, avoiding excessive solder bump undercutting in the copper layer. The cell voltage may be such that the solder bump is only slightly undercut so as to form a stepped base C4 structure upon reflowing. Ti-W is removed by a chemical process.

Electroetching process for seed layer removal in electrochemical

A chemical etchant (and a method for forming the etchant) is disclosed for removing thin films of titanium-tungsten alloy in microelectronic chip fabrication. The alloy removed is preferably 10% Ti and 90% W, which is layered onto a substrate under chromium and copper seed layers for electrodeposition of C4 solder bumps. In this application the Ti--W etchant should not attack aluminum, chromium, copper, or lead-tin solders, and should dissolve Ti--W rapidly. The invention achieves this with a mixture of 30% by weight hydrogen peroxide and water, to which is added EDTA and potassium sulfate. The hydrogen peroxide etches Ti--W rapidly at temperatures between 40.degree. C. and 60.degree. C. EDTA forms a complex with tungsten to prevent plating of the Pb--Sn solder with W, and potassium sulfate forms a protective coating on the Pb--Sn solder to protect it from chemical attack.

Selective etching of TiW for C4 fabrication

A contactless method and apparatus for in-situ chemical etch monitoring of an etching process during etching of a workpiece with a wet chemical etchant are disclosed. The method comprises steps of providing a base member having a reference surface; releasably securing the workpiece to the base member; providing at least two sensors disposed on the base member to be proximate to but not in contact with the outer perimeter of the workpiece surface; and monitoring an electrical characteristic between said at least two sensors, wherein a prescribed change in the electrical characteristic is indicative of a prescribed condition of the etching process.

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Peekskill, NY, United States of America

Ravindra V Shenoy