EP4212966A1 - Verfahren zur begrenzung der verformung einer uhr aus silizium - Google Patents

Verfahren zur begrenzung der verformung einer uhr aus silizium Download PDF

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Publication number
EP4212966A1
EP4212966A1 EP23151601.4A EP23151601A EP4212966A1 EP 4212966 A1 EP4212966 A1 EP 4212966A1 EP 23151601 A EP23151601 A EP 23151601A EP 4212966 A1 EP4212966 A1 EP 4212966A1
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EP
European Patent Office
Prior art keywords
silicon
timepiece
wafer
thermal oxidation
hairsprings
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP23151601.4A
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English (en)
French (fr)
Inventor
Enrica MONTINARO
Nicolas Tille
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Sigatec Sa
Richemont International SA
Original Assignee
Sigatec Sa
Richemont International SA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Sigatec Sa, Richemont International SA filed Critical Sigatec Sa
Publication of EP4212966A1 publication Critical patent/EP4212966A1/de
Pending legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G04—HOROLOGY
    • G04B—MECHANICALLY-DRIVEN CLOCKS OR WATCHES; MECHANICAL PARTS OF CLOCKS OR WATCHES IN GENERAL; TIME PIECES USING THE POSITION OF THE SUN, MOON OR STARS
    • G04B17/00—Mechanisms for stabilising frequency
    • G04B17/04—Oscillators acting by spring tension
    • G04B17/06—Oscillators with hairsprings, e.g. balance
    • G04B17/066—Manufacture of the spiral spring
    • G—PHYSICS
    • G04—HOROLOGY
    • G04B—MECHANICALLY-DRIVEN CLOCKS OR WATCHES; MECHANICAL PARTS OF CLOCKS OR WATCHES IN GENERAL; TIME PIECES USING THE POSITION OF THE SUN, MOON OR STARS
    • G04B1/00—Driving mechanisms
    • G04B1/10—Driving mechanisms with mainspring
    • G04B1/14—Mainsprings; Bridles therefor
    • G04B1/145—Composition and manufacture of the springs
    • G—PHYSICS
    • G04—HOROLOGY
    • G04B—MECHANICALLY-DRIVEN CLOCKS OR WATCHES; MECHANICAL PARTS OF CLOCKS OR WATCHES IN GENERAL; TIME PIECES USING THE POSITION OF THE SUN, MOON OR STARS
    • G04B13/00—Gearwork
    • G04B13/02—Wheels; Pinions; Spindles; Pivots
    • G—PHYSICS
    • G04—HOROLOGY
    • G04B—MECHANICALLY-DRIVEN CLOCKS OR WATCHES; MECHANICAL PARTS OF CLOCKS OR WATCHES IN GENERAL; TIME PIECES USING THE POSITION OF THE SUN, MOON OR STARS
    • G04B15/00—Escapements
    • G04B15/14—Component parts or constructional details, e.g. construction of the lever or the escape wheel
    • G—PHYSICS
    • G04—HOROLOGY
    • G04B—MECHANICALLY-DRIVEN CLOCKS OR WATCHES; MECHANICAL PARTS OF CLOCKS OR WATCHES IN GENERAL; TIME PIECES USING THE POSITION OF THE SUN, MOON OR STARS
    • G04B17/00—Mechanisms for stabilising frequency
    • G04B17/04—Oscillators acting by spring tension
    • G04B17/045—Oscillators acting by spring tension with oscillating blade springs
    • G—PHYSICS
    • G04—HOROLOGY
    • G04B—MECHANICALLY-DRIVEN CLOCKS OR WATCHES; MECHANICAL PARTS OF CLOCKS OR WATCHES IN GENERAL; TIME PIECES USING THE POSITION OF THE SUN, MOON OR STARS
    • G04B17/00—Mechanisms for stabilising frequency
    • G04B17/04—Oscillators acting by spring tension
    • G04B17/06—Oscillators with hairsprings, e.g. balance
    • G04B17/063—Balance construction
    • G—PHYSICS
    • G04—HOROLOGY
    • G04B—MECHANICALLY-DRIVEN CLOCKS OR WATCHES; MECHANICAL PARTS OF CLOCKS OR WATCHES IN GENERAL; TIME PIECES USING THE POSITION OF THE SUN, MOON OR STARS
    • G04B17/00—Mechanisms for stabilising frequency
    • G04B17/20—Compensation of mechanisms for stabilising frequency
    • G04B17/22—Compensation of mechanisms for stabilising frequency for the effect of variations of temperature
    • G04B17/227—Compensation of mechanisms for stabilising frequency for the effect of variations of temperature composition and manufacture of the material used
    • G—PHYSICS
    • G04—HOROLOGY
    • G04D—APPARATUS OR TOOLS SPECIALLY DESIGNED FOR MAKING OR MAINTAINING CLOCKS OR WATCHES
    • G04D3/00—Watchmakers' or watch-repairers' machines or tools for working materials

Definitions

  • the present invention relates to the field of manufacturing parts for watchmaking.
  • the invention relates more particularly to a method for limiting the deformation of a silicon timepiece, in particular a silicon hairspring.
  • the movements of mechanical watches are regulated by means of a mechanical regulator comprising a resonator, that is to say an elastically deformable component whose oscillations determine the rate of the watch.
  • a mechanical regulator comprising a resonator, that is to say an elastically deformable component whose oscillations determine the rate of the watch.
  • Many watches include, for example, a regulator comprising a hairspring as a resonator, mounted on the axis of a balance wheel and set in oscillation by means of an escapement.
  • the natural frequency of the balance-spring couple makes it possible to regulate the watch and depends in particular on the stiffness of the balance-spring.
  • the stiffness of the hairspring also defines its intrinsic vibratory characteristics, such as the natural frequency and the resonant frequencies.
  • the natural frequency of an elastic system is the frequency at which this system oscillates when it is in free evolution, that is to say without exciting force.
  • a resonance frequency of an elastic system subjected to an exciting force is a frequency at which a local maximum of displacement amplitude can be measured for a given point of the elastic system.
  • the displacement amplitude follows an upward slope before this resonance frequency, and follows a downward slope afterwards, at any point that does not correspond to a vibration node.
  • the recording of the displacement amplitude as a function of the excitation frequency shows a displacement amplitude peak or resonance peak which is associated with or which characterizes the resonance frequency.
  • the natural frequency of the regulator member formed by the balance spring of stiffness R coupled to a balance wheel of inertia l is in particular proportional to the square root of the stiffness of the balance spring.
  • the main specification of a spiral spring is its stiffness, which must be within a well-defined range in order to be paired with a balance wheel, which forms the inertial element of the oscillator. This pairing operation is essential to precisely adjust the frequency of a mechanical oscillator.
  • silicon hairsprings can be manufactured on a single wafer using micro-fabrication technologies. It is in particular known to produce a plurality of hairsprings in silicon with very high precision by using photolithography and machining/etching processes in a silicon wafer.
  • the methods for producing these mechanical hairsprings generally use monocrystalline silicon wafers, but wafers made of other materials can also be used, for example polycrystalline or amorphous silicon, other semiconductor materials, glass, ceramic , carbon, carbon nanotubes or a composite comprising these materials.
  • monocrystalline silicon belongs to the cubic crystalline class m3m whose coefficient of thermal expansion (alpha) is isotropic.
  • Silicon has a very negative value of the first thermoelastic coefficient, and consequently the stiffness of a silicon resonator, and therefore its natural frequency, varies greatly according to the temperature.
  • the documents EP1422436 , EP2215531 And WO2016128694 describe a spiral-type mechanical resonator made from a core (or two cores in the case of WO2016128694 ) in monocrystalline silicon and whose variations in temperature of the Young's modulus are compensated by a layer of amorphous silicon oxide (SiO 2 ) surrounding the core (or cores), the latter being one of the rare materials having a thermoelastic coefficient positive.
  • SiO 2 amorphous silicon oxide
  • the document WO2019/180596 proposes to arrange the plates horizontally and on a support, making it possible to limit the deformations related to the own weight of the hairspring and to the heat.
  • the applicants have found another unexpected solution to this problem.
  • the solution identified can be generalized to other silicon timepieces for which it is essential to control the dimensions and manufacturing tolerances.
  • the invention relates to a process for limiting the deformation of a silicon timepiece formed in a wafer, during thermal oxidation, characterized in that the thermal oxidation is carried out on a highly doped silicon timepiece.
  • Another aspect of the invention relates to a use of a wafer comprising at least one layer of highly doped silicon, to limit the deformation of a timepiece formed in said highly doped silicon layer, during thermal oxidation.
  • Another aspect may relate to a process for the thermal oxidation of a silicon timepiece, comprising a preliminary step consisting in heavily doping the silicon timepiece, and in which the thermal oxidation step is free of reversal or modification of the orientation with respect to gravity of the highly doped silicon timepiece.
  • Another aspect may relate to a process for the thermal oxidation of a silicon timepiece, in which the thermal oxidation step is free from reversal or modification of the orientation with respect to gravity of the piece of silicon timepiece, and in which the method comprises a preliminary step consisting in heavily doping the silicon timepiece, so as to limit the deformation of the timepiece during thermal oxidation.
  • the method may include a step of etching the timepiece into a silicon wafer, leaving a portion attached to a base substrate and forming at least one free end of the substrate.
  • a free end will be retained by the rest of the timepiece and in particular by the portion attached to the base substrate, which could cause deformation of the timepiece during thermal oxidation, but the use highly doped silicon eliminates or reduces this risk of deformation, even without a reversal step.
  • WO2019/180596 describes the steps that make it possible to etch watch components, particularly hairsprings, in a wafer (also called a wafer) of silicon. These lithography steps are well known to those skilled in the art and are incorporated by reference into the present application.
  • This wafer can be of different types, comprising a single layer of silicon, or a layer of silicon arranged on a layer of silicon oxide (SOI), or several layers of silicon, with a layer of silicon oxide interposed between the silicon layers.
  • SOI silicon oxide
  • the component is etched in the silicon layer or in a group of silicon layers.
  • Silicon can be of different natures, monocrystalline, polycrystalline or even amorphous.
  • these oxidation steps are carried out in an oxidation furnace 10, at temperatures typically between 600° C. and 1300° C. and for example between 1000° C. and 1100° C., which makes it possible to form a layer of silicon oxide (SiO 2 ) which covers the wafer and the etched components, consuming silicon from the wafer.
  • a treatment time of between 30 minutes and 30 hours can be provided.
  • the wafers are loaded into the oven by being arranged horizontally.
  • this solution cannot work for wafers 12 arranged vertically, in particular in furnaces 10 with horizontal loading, as represented on the figure 1 .
  • the doping is high boron or phosphorus doping.
  • high doping we mean an average concentration of dopant within the same wafer greater than 1 ⁇ 10 18 , more particularly greater than 1 ⁇ 10 19 , even more particularly greater than 5 ⁇ 10 19 atoms per cm 3 .
  • a high doping can be defined as a doping corresponding to a resistivity smaller than 0.01 ohm.cm, or even a resistivity between 0.0045 and 0.0055 ohm.cm, even more particularly a resistivity of 0.005 ohm.cm.
  • a heavily doped silicon part will have a resistivity smaller than 0.01 ohm.cm, or even a resistivity of between 0.0045 and 0.0055 ohm.cm, even more particularly a resistivity of 0.005 ohm.cm.
  • Provision can be made, in a non-limiting manner, to carry out a negative N-type doping with phosphorus or redphosphorus, arsenic, antimony, or a positive P-type doping with boron.
  • the effects of doping are particularly sensitive with hairsprings made of monocrystalline silicon, in particular having crystalline orientations ⁇ 100> or ⁇ 110>. It is in fact the types of silicon which are particularly subject to deformation during a thermal oxidation operation.
  • FIG. 4 represents the results of measurements carried out on a batch A1 of hairsprings of a first geometry, in undoped silicon and having undergone an oxidation step in a vertical position and on a batch B1 of hairsprings in silicon, of the same first geometry and strongly doped, having undergone the same oxidation step in a vertical position.
  • the parts of batch A1 were made of undoped ⁇ 100> silicon, and have an electrical conductivity of between 1.2 and 6.7 ohm.cm.
  • the parts of batch B1 were made of heavily doped silicon ⁇ 100> (in this non-limiting example, it is phosphorus doping, N doping, negative), and have an electrical conductivity between 0.003 and 0 .01 ohm.cm.
  • All the parts of batch A1 and all the parts of batch B1 were engraved to present the same geometry, and were then subjected to the same thermal oxidation step in a vertical position (in this non-limiting example, it is exposure to a temperature of between 1000°C and 1100°C and for a period of between 1 hour and 30 hours depending on the desired thickness of silicon oxide). Before the thermal oxidation step, all the parts (lots A1 and B1) have a conforming geometry.
  • There figure 4 represents the results of measurements of the radius of the terminal curve of the hairsprings, carried out on the parts of batch A1 and the parts of batch B1, after the thermal oxidation step.
  • There figure 4 represents: the minimum and maximum tolerances respectively R m and R M that the radius of the terminal curve must respect, the number of parts for each class of radius values, and the Gaussian curves constructed from the measured populations.
  • the parts of batch A1 present a large dispersion (standard deviation measured of 0.072 mm), with a little more than half of the parts outside the range of tolerances [R m -R M ], while the parts of batch B1 have low dispersion (standard deviation of 0.027 mm) and are all within the tolerance range [R m -R M ].
  • These data show that the use of highly doped silicon makes it possible to significantly reduce the deformations during the thermal oxidation step, with in the example above, a reduction by three of the variability of the value of the radius of the terminal curve of the hairsprings, and parts that all remain within the tolerance range after thermal oxidation.
  • the parts of batch A and batch B were made of undoped ⁇ 111> silicon, and have an electrical conductivity of between 1.0 and 10.0 ohm.cm.
  • the parts of batch C were made of heavily doped ⁇ 111> silicon (in this non-limiting example, it is doping with phosphorus, N doping, negative), and have an electrical conductivity of between 0.001 and 0.005 ohm.cm.
  • the parts of batch A were subjected to a thermal oxidation step carried out in one go (in this non-limiting example, it is an exposure to a temperature between 1000°C and 1100°C and for a duration between 1h and 30h depending on the desired thickness of silicon oxide), in a vertical position.
  • the parts of batch B were subjected to a thermal oxidation stage in vertical position, with an intermediate reversal with respect to gravity.
  • the parts of lot C were subjected to a thermal oxidation step carried out in one go, in a vertical position, like the parts of lot A.
  • Lot A parts have an end curve radius of approximately 3.205 mm
  • Lot B parts have an end curve radius of approximately 3.147 mm
  • Lot C parts have an end curve radius of approximately 3.147 mm. terminal curve of about 3.107 mm.
  • the use of a highly doped silicon wafer makes it possible to avoid the deformations encountered with undoped silicon wafers, during thermal oxidation steps during which the wafers are arranged vertically, without having to flip or change the orientation of the wafers between successive oxidation steps.
  • the effect is also obtained when the wafers are arranged horizontally, even if this deformation is less noticeable, the fact remains that the hairsprings can deform outside the plane of the wafer, under the effect of their weight, and that such deformation is also limited with heavily doped hairsprings.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Metallurgy (AREA)
  • Manufacturing & Machinery (AREA)
  • Crystals, And After-Treatments Of Crystals (AREA)
EP23151601.4A 2022-01-14 2023-01-13 Verfahren zur begrenzung der verformung einer uhr aus silizium Pending EP4212966A1 (de)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP22151563.8A EP4212965A1 (de) 2022-01-14 2022-01-14 Verfahren zur begrenzung der verformung einer uhrenkomponente aus silizium

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EP4212966A1 true EP4212966A1 (de) 2023-07-19

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EP23151601.4A Pending EP4212966A1 (de) 2022-01-14 2023-01-13 Verfahren zur begrenzung der verformung einer uhr aus silizium

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Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1422436A1 (de) 2002-11-25 2004-05-26 CSEM Centre Suisse d'Electronique et de Microtechnique SA Spiraluhrwerkfeder und Verfahren zu deren Herstellung
EP2215531A1 (de) 2007-11-28 2010-08-11 Manufacture et fabrique de montres et chronomètres Ulysse Nardin Le Locle SA Mechanischer oszillator mit einem optimierten thermoelastischen koeffizienten
WO2016128694A1 (fr) 2015-02-13 2016-08-18 Tronic's Microsystems Oscillateur mécanique et procédé de réalisation associe
EP3159746A1 (de) * 2015-10-19 2017-04-26 Rolex Sa Stark verbesserte siliziumfeder für uhr
WO2019180596A1 (fr) 2018-03-20 2019-09-26 Patek Philippe Sa Geneve Procede de fabrication de composants horlogers en silicium
EP3709098A1 (de) * 2019-03-14 2020-09-16 Seiko Epson Corporation Uhrenkomponente, uhrwerk und uhr
CH716696A2 (fr) * 2019-10-15 2021-04-15 Sigatec Sa Procédé de fabrication de spiraux horlogers.

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1422436A1 (de) 2002-11-25 2004-05-26 CSEM Centre Suisse d'Electronique et de Microtechnique SA Spiraluhrwerkfeder und Verfahren zu deren Herstellung
EP2215531A1 (de) 2007-11-28 2010-08-11 Manufacture et fabrique de montres et chronomètres Ulysse Nardin Le Locle SA Mechanischer oszillator mit einem optimierten thermoelastischen koeffizienten
WO2016128694A1 (fr) 2015-02-13 2016-08-18 Tronic's Microsystems Oscillateur mécanique et procédé de réalisation associe
EP3159746A1 (de) * 2015-10-19 2017-04-26 Rolex Sa Stark verbesserte siliziumfeder für uhr
WO2019180596A1 (fr) 2018-03-20 2019-09-26 Patek Philippe Sa Geneve Procede de fabrication de composants horlogers en silicium
EP3709098A1 (de) * 2019-03-14 2020-09-16 Seiko Epson Corporation Uhrenkomponente, uhrwerk und uhr
CH716696A2 (fr) * 2019-10-15 2021-04-15 Sigatec Sa Procédé de fabrication de spiraux horlogers.

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