Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L24/00—Arrangements for connecting or disconnecting semiconductor or solid-state bodies; Methods or apparatus related thereto
  • H01L24/80—Methods for connecting semiconductor or other solid state bodies using means for bonding being attached to, or being formed on, the surface to be connected
  • H01L24/81—Methods for connecting semiconductor or other solid state bodies using means for bonding being attached to, or being formed on, the surface to be connected using a bump connector
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L2224/00—Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
  • H01L2224/80—Methods for connecting semiconductor or other solid state bodies using means for bonding being attached to, or being formed on, the surface to be connected
  • H01L2224/81—Methods for connecting semiconductor or other solid state bodies using means for bonding being attached to, or being formed on, the surface to be connected using a bump connector
  • H01L2224/818—Bonding techniques
  • H01L2224/81801—Soldering or alloying
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
  • H01L2924/0001—Technical content checked by a classifier
  • H01L2924/00013—Fully indexed content
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
  • H01L2924/01—Chemical elements
  • H01L2924/01006—Carbon [C]
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
  • H01L2924/01—Chemical elements
  • H01L2924/01013—Aluminum [Al]
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
  • H01L2924/01—Chemical elements
  • H01L2924/01029—Copper [Cu]
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
  • H01L2924/01—Chemical elements
  • H01L2924/01033—Arsenic [As]
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
  • H01L2924/01—Chemical elements
  • H01L2924/01058—Cerium [Ce]
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
  • H01L2924/01—Chemical elements
  • H01L2924/01073—Tantalum [Ta]
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
  • H01L2924/01—Chemical elements
  • H01L2924/01079—Gold [Au]
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
  • H01L2924/01—Chemical elements
  • H01L2924/01082—Lead [Pb]
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
  • H01L2924/013—Alloys
  • H01L2924/014—Solder alloys
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
  • H01L2924/19—Details of hybrid assemblies other than the semiconductor or other solid state devices to be connected
  • H01L2924/1901—Structure
  • H01L2924/1904—Component type
  • H01L2924/19041—Component type being a capacitor
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
  • H01L2924/19—Details of hybrid assemblies other than the semiconductor or other solid state devices to be connected
  • H01L2924/1901—Structure
  • H01L2924/1904—Component type
  • H01L2924/19042—Component type being an inductor

Definitions

• the invention relates to the mounting of sensors of physical quantities capable of operating in a harsh environment.
• the assembly consists in transferring a micro-machined sensor to a base provided with electrical connection pins.
• the sensor is produced for example from one or more machined silicon wafers, comprising mechanical elements (membranes, beams, seismic masses, etc.), electronic elements (capacity armatures, or strain gauges in particular), electrical connections, and metal contact pads allowing the electrical connection with the pins of the base when the sensor is fixed on the base.
• the senor is bonded or soldered by its rear face to the base, in a central part of the latter surrounded by the connection pins which pass through the base.
• the connection pads of the sensor, on the front of it, are connected by welded wires (technique called “wire-bonding") between the pads and the tops of the connection pins which protrude from the surface of the base.
• the invention aims to propose a less expensive solution, having good mechanical strength qualities, a reduced size, and usable in a large number of applications, including in particular pressure sensors and accelerometers.
• a physical quantity sensor comprising at least one micro-machined plate provided with conductive connection pads on a main face, and a base provided with conductive connection pins, the main face being turned towards the base and each connection pad coming opposite a corresponding pin end, an electrolytic deposit of metal or metals coating the end of each pin and the corresponding connection pad so as to establish a rigid fixing between this end and the pad.
• electrolytic deposition is meant a deposition of metal or metals (alloy of metals or deposition of several metals) on a conductive zone, obtained by migration of metal ions from a liquid solution. Migration can be caused either by the passage of an electric current (conventional electrolytic bath with current supply electrodes), or by chemical reaction without current supply (so-called “electroless” deposit).
• the production method according to the invention therefore consists
• the active part comprising at least one plate provided with connection pads on a front face
• the base being provided with conductive pins whose ends are spatially arranged so that each end comes to rest against a respective stud of the plate when the front face of this one is brought closer to the base, - to hold the plate against the base and immerse the plate and at least the spindle ends in a bath electrolytic, and electrolytically depositing conductive metal on the pin ends and the studs with a sufficient metal thickness to ensure rigid fixing between the pins and the studs by the deposited metal.
• the electrolytic deposition on the pads and on the pins achieves in a way a weld with the addition of metal between these pads and the pins, and the resistance of this weld in difficult environment is much higher than that which would be obtained if one used a simple conductive glue between the pins and the studs.
• this fixing is done without the need to bring the studs to high temperature as would be the case with a real weld or solder.
• the electroplating attachment operation is carried out without mechanical stress between the studs and the pins.
• This process can be implemented collectively for batches of sensors, without involving expensive machinery such as those which allow automatic wire-bonding.
• the pins may have a height above the surface of the base, for example a few millimeters for a base of one centimeter in diameter, so that the sensor is suspended in a relatively flexible manner due to the inherent flexibility of pin. It is therefore less subject to the constraints that the base can withstand, in particular to the constraints of thermal expansion, shocks, vibrations, etc.
• connection pins and the connection pads covered with electrolytic metal are covered with an insulating layer to eliminate the risks of short-circuit or the paths of current leakage between pins when these are placed in a liquid environment. or gaseous not perfectly insulating (humid and salty air for example, or water).
• the insulating layer can be produced by electrolytic oxidation or nitriding, or by a second conductive metallic deposit and an oxidation or nitriding of this second deposit. It can also be made by depositing mineral insulation by chemical decomposition possibly assisted by plasma. For less severe environments, deposition of an insulating organic layer can be envisaged.
• FIG. 3 shows the sensor according to the invention at the end of the manufacturing process.
• the invention will be described only with regard to a pressure sensor which must operate in a harsh environment, for example an exhaust gas pressure sensor of an internal combustion engine, or a pressure sensor placed inside the cylinder of such an engine.
• a harsh environment for example an exhaust gas pressure sensor of an internal combustion engine, or a pressure sensor placed inside the cylinder of such an engine.
• the environment is harsh due to the very high temperatures (several hundred degrees Celsius) and the harmfulness of the ambient environment (aggressive gases).
• the invention is however applicable to other sensors.
• FIG. 1 represents a sensor according to the invention, with an active part and a base, in a phase which precedes the fixing of the active part on the base.
• the active part of the sensor is formed in this example from two welded silicon plates 10 and 12, machined so as to delimit a cavity 14 closed by a thin silicon membrane 16.
• the plate 10 could be made of glass.
• these elements are strain gauges formed directly in the silicon (by implantation of suitable dopants in the silicon) or formed in a layer of silicon separated from the silicon substrate by an insulating layer (structure silicon on insulator, called "SOI For "silicon on insulator”).
• SOI structure silicon on insulator
• these gauges can be made on the membrane inside the cavity 14; if the environment is less difficult, they can be formed outside of the cavity 14.
• the gauges are sensitive to deformations of the membrane, caused by the pressure variations that one wants to measure.
• connection pads 22 which are conductive metal surfaces serving for the electrical connection with external pins.
• the front face, or main face, of the active part of the sensor is that which faces downwards in FIG. 1.
• the front face is generally protected by a passivation layer 24 (made of silicon oxide or nitride for example) which covers the entire surface except for the connection pads 22 or at least their central part.
• a base 30 is made through which metallic connection pins 32 are at least equal to the number of connection pads present on the sensor and necessary for the operation thereof. This.
• the upper part of the pins is located above the base and protrudes from the surface thereof.
• the lower part descends below the lower surface of the base and can be plugged, for example, into a female connector or into holes in a printed circuit, or connected by soldering to individual conducting wires, etc.
• the base can be insulating or conductive, but in the latter case it is necessary to provide that an insulator 33 (for example glass in the case of a metal base) fills the passages in which the pins are inserted, in order to electrically isolate the pins from each other.
• the base is made of a metal alloy such as Kovar, with glass bushings. It could be made of insulating ceramic, or even plastic for moderate temperature environments.
• the spatial arrangement of the pins in the base is such that when the front face of the sensor (lower face in FIG. 1) is brought closer to the upper part of the base, each pin comes to bear in direct contact (mechanical and electrical) respectively with a connection pad 22 of the sensor.
• the method according to the invention then consists in immersing in an electrolytic bath the active part of the sensor as well as the upper part of the pins, keeping them in contact with the studs, so that a conductive metallic deposit is formed, by electrolytic migration, both on the studs and on the upper part of the pins.
• the electrolytic deposition operation (with or without electric current to carry out the electrolysis) is continued until the thickness of metal deposited is sufficient to ensure a rigid mechanical connection between each of the pins and a corresponding stud of the part sensor active.
• FIG. 2 represents the sensor thus rigidly fixed to its base.
• the part of the studs 22 and the pins 32 which has been in contact with the electrolytic bath is entirely covered with a layer 34 of deposited metal.
• the metal has not deposited on the non-conductive parts of the sensor (the passivation layer 24 in particular).
• all of the spindle part protruding from the base is covered because all this part has been immersed in the bath, but this is not compulsory; it suffices that the spindle area in the immediate vicinity of the connection pad is immersed in the bath.
• the metal deposited by electrolysis can in particular be copper or gold, or nickel, but other metals are possible. Several metals can be deposited. A metal alloy or a co-deposition of two or more metals can also be envisaged.
• the connection pads can be made of gold or aluminum or other metals or a combination of metals (several metallic layers sometimes overlapped). If the deposit is made by conventional electrolysis with current flow in a solution containing metal ions, we arrange to connect all the pins together during the time of electrolysis (preferably by the back of the base, c (i.e. by a part which does not immerse in the electrolytic bath). An appropriate electrolysis potential difference is applied between these pins and another electrode immersed in the bath.
• Electroless deposition is also possible; in this case the electrolysis occurs by simple chemical reaction between the pins or bond pads and the ionic solution of the electrolytic bath without application of external potential differences.
• the thickness of metal deposit on the pins may be a few tens of micrometers or more to ensure a rigid mechanical weld between the pins and the surface of the sensor.
• the upper part of the pins, protruding above the upper surface of the base, can have a very short length, or a long length to then ensure a certain flexibility of connection between the sensor and its base, the flexibility being due to the natural flexibility of the pins, the greater the thinner the pins and the longer their protruding part.
• This layer serves as a passivation layer, in particular preventing electrical leakage of current between the pins when the latter are in a non-perfectly insulating atmosphere (salty air atmosphere, etc.).
• This passivation layer can not only prevent electrical leakage through the ambient air, but it can also prevent penetration of moisture towards the conductive parts of the sensor.
• the nature of this layer is obviously a function of the severity of the ambient conditions: a mineral layer will be necessary for high temperatures, an organic layer may be sufficient if the temperature remains below 200 ° C. for example.
• the mineral layers which can be deposited are for example silicon oxide, silicon nitride, silicon carbide, and even diamond.
• an organic layer could be silicone or parylene.
• a particularly " effective process for harsh environments may consist in particular of carrying out electrolytic oxidation or nitriding of the conductive metal surface of the pins and of the sensor pads.
• the metal layer 34 which was used to weld is electrolytically oxidized or nitride the sensor on the pins, by immersing the sensor in a new electrolytic bath suitable for this oxidation or nitriding.
• a second metal layer is deposited by electrolysis, on top of layer 34 (especially if layer 34 is not not easy to oxidize or nitride electrolytically, or if the oxidation or nitriding results in a layer insufficiently resistant to environmental aggression, it is preferable to deposit a second metallic layer which is more easily oxidizable or nitriding); the second layer can be nickel or tantalum for example; then oxidize or nitride the d second metal layer, either in an oxidizing or nitriding gas atmosphere or by immersing the sensor and the pins in an oxidizing or nitriding chemical or electrolytic bath.
• the insulating layer is formed by an electrolytic deposition of insulator (metal oxide or metal nitride).
• the formation of the passivation layer can be carried out more conventionally by depositing an inorganic insulating layer (silicon oxide or silicon nitride) by gas deposition assisted by plasma.
• the additional layer is not limited to covering the visible conductive parts of the sensor, it covers all the parts exposed to the source of deposition product in the deposition reactor.
• the insulating protective layer thus deposited makes it possible in particular to avoid having to protect the sensor by an insulating oil bath and a metal membrane as was sometimes done in the prior art to avoid electrical leakage between pins brought to potentials. different.
• FIG. 3 shows the sensor provided with an additional protective layer 36 on all the conductive parts.
• the figures show straight conductive pins.
• This has the advantage of facilitating the application of the end of the pins against the conductive pads during electrolysis; this also subsequently has the advantage of better decoupling the sensor from its base, avoiding transmitting excessive efforts or undesirable vibrations to the active part, while the active part, by its very nature, is particularly sensitive to mechanical stresses.
• the invention is particularly applicable to pressure, force, acceleration, temperature sensors, operating in a harsh environment.

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• Engineering & Computer Science (AREA)
• Computer Hardware Design (AREA)
• Microelectronics & Electronic Packaging (AREA)
• Power Engineering (AREA)
• Measuring Fluid Pressure (AREA)
• Pressure Sensors (AREA)

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• 2000
  • 2000-08-11 FR FR0010582A patent/FR2812969B1/fr not_active Expired - Fee Related
• 2001
  • 2001-08-07 US US10/110,065 patent/US6647759B2/en not_active Expired - Fee Related
  • 2001-08-07 EP EP01963070A patent/EP1307911A1/de not_active Withdrawn
  • 2001-08-07 WO PCT/FR2001/002568 patent/WO2002015257A1/fr active Application Filing

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