Method for measuring the resistance and capacitance of thin films during deposition

Abstract

The invention relates to a method for producing a thin film deposition chip (40), comprising: a) - forming, on a substrate (4) made of an insulating or semiconductor material, a plurality of measurement electrodes (2), each electrode having a central portion and edges inclined towards the surface of the substrate (4); b) - forming a deposition mask (6), defining a deposition window (8), said mask having indentations (10) in the vicinity of the substrate and of the window.

Description

[0001] DESCRIPTION

[0002] Title: METHOD FOR MEASURING THE RESISTANCE AND CAPACITANCE OF THIN FILMS DURING DEPOSITION

[0003] TECHNICAL FIELD AND STATE OF THE PRIOR ART

[0004] The invention relates to the field of measuring resistance and / or capacitance and / or inductance during deposition or during oxidation of thin layers, for example with a thickness greater than approximately 1 nm to 3 nm (or even greater, for example up to 200 nm), metallic, in the presence or absence of reactive gases (for example oxygen and / or nitrogen) semiconducting or even insulating.

[0005] The invention allows adjustment of the properties, for example electrical conduction, of these thin layers, and to resolve the reproducibility problems relating to this type of deposition, in particular when precise characteristics of conductivity or resistance and / or superconducting inductance (which can be adjusted via the resistance of the film at room temperature) and / or capacitance are required for electronic devices.

[0006] Currently, according to known techniques for controlling the reproducibility of tunnel junctions in aluminum or granular aluminum (which is highly non-reproducible), a large number of samples are manufactured and selected or adjusted a posteriori.

[0007] Furthermore, the main in-situ measurement methods are optical methods (interferometry, ellipsometry), which are unreliable for determining resistance, very expensive, and require specific deposition equipment with optical access; furthermore, such equipment is not compatible with some existing machines. Known techniques lack reproducibility with regard to the measurement of the electrical conduction of films obtained by deposition of thin layers, particularly in the presence of oxygen and / or nitrogen and / or hydrogen. This is the case, in particular, for granular aluminum (comprising aluminum grains in an A Os matrix) and tunnel junctions, for example AI-AIO X -AI.

[0008] REPLACEMENT SHEET (RULE 26) We know of a device from the Telemark company which offers resistive measurement: https: / / telemark.com / sheet-resistance-monitor /

[0009] But this device does not solve the mentioned problem because the chip with which the thin film is measured is not well adapted, for several reasons, among others:

[0010] - this is a classic PCB whose surface roughness does not guarantee the continuity of very thin films,

[0011] - the contact pads are generally quite thick on this type of PCB, the film being deposited cannot therefore cover these pads since their thickness is very low (of the order of a few nm for example),

[0012] - the area of ​​deposition of the film on the PCB is not precisely defined, and we must therefore resort to a corrective geometric coefficient presenting numerous uncertainties to return to the resistance per square of the deposited film;

[0013] - the PCB holding block is thick, shadows the material flow during deposition, and cannot be fixed in a position close to the sample of interest, nor at a temperature identical to the latter, which makes it unlikely that the measured PCB has exactly the same resistance per square as the sample of interest; note that the temperature of the plate plays a role in the growth of the films.

[0014] A problem that therefore arises is the lack of reproducibility of the electrical conduction of films obtained by deposition of thin layers, particularly in the presence of oxygen (or another reactive gas). This concerns, for example, granular aluminum (comprising aluminum grains in an AhCh matrix) and Al-Al0x-Al tunnel junctions.

[0015] We find the same problem for:

[0016] - metal deposits (e.g. titanium or chrome) sensitive to residual vacuum and contaminants;

[0017] - alloy deposits by co-evaporation or co-sputtering (or co-pulverization), for example Niobium-silicon, or Yttrium-silicon, or Nickel-Chromium deposits;

[0018] - deposits of dielectric or insulating materials.

[0019] REPLACEMENT SHEET (RULE 26) A problem that also arises is the lack of reproducibility of the oxidation rate of tunnel junctions formed by deposition of a metal layer, followed by oxidation, followed immediately by 2 ème metal layer deposition, e.g. when forming AI-AIO tunnel junctions X -AI, or during the formation of Nb-AI-AIOx-AI-Nb junctions.

[0020] Another problem that arises is the lack of reproducibility of the etching of an oxide layer by ion beam, for example for the resumption of contact on pre-deposited film oxidizing in air (Al, N b...).

[0021] STATEMENT OF THE INVENTION

[0022] The invention aims to solve all or part of these problems.

[0023] It firstly concerns a method for producing a support, or a chip, for depositing films, in particular of the thin film type, comprising: a) - the formation, on a substrate made of an insulating or semi-conducting material, of a plurality of measuring electrodes, each electrode having a central part, inclined edges or with a slope towards the surface of the substrate; b) - the formation of a non-conductive deposition mask, defining a deposition window, this mask comprising notches in the vicinity of the substrate and of said deposition window.

[0024] A deposition support, or chip according to the invention, makes it possible, for example, to control the production of a film, in particular a thin film, by measuring in real time and using the electrodes the evolution of an electrical quantity, for example the conductivity or the electrical resistance of the film being formed, by connecting means for measuring this quantity to the contact pads.

[0025] In a method according to the invention, or in a chip or deposition substrate (described later) according to the invention:

[0026] - the window can be positioned above a plurality of electrodes, preferably above all the measuring electrodes, to allow a deposited film to cover them all on a part and electrically connect them together through a track of well-defined geometry;

[0027] - and / or preferably each electrode has a contact pad at one of its ends;

[0028] REPLACEMENT SHEET (RULE 26) - and / or preferably still, the electrodes are, at least in the deposition window, parallel to each other;

[0029] - and / or the edges of the electrodes, inclined towards the surface of the substrate with a slope, preferably a gentle slope, for example at 45°, make it possible to achieve a uniform deposition of a thin film without breaking it; more generally, the electrodes may have edges, forming gentle lateral slopes, with an angle with the surface of the substrate of less than 80°, for example between 15° and 60° (or 50°);

[0030] - and / or preferably the electrodes are made of a non-oxidizing material to allow electrical contact with the thin film deposited on top;

[0031] - and / or the measuring electrodes can be, for example, made of Ti / Au.

[0032] Around the edge of the deposition window, the edge of the insulating mask is suspended by the notches to avoid continuity of the material deposition between the bottom (the deposition made on the substrate and the electrodes) and the top of the mask, which would distort any measurement made with the electrodes.

[0033] The use of electrodes under the film being deposited allows measurements to be taken directly in contact with the film.

[0034] According to one example, the invention makes it possible to control the formation of in-situ Josephson junctions for quantum technologies, by measuring in real time the resistance of an already deposited aluminum film, to determine the oxidized proportion of the film (no longer conducting electric current), to monitor the growth of the oxide and to stop the oxidation on a resistance setpoint.

[0035] According to another example, the invention makes it possible to control the reproducibility of the surface resistance of granular aluminum films (Aluminum evaporated in the presence of oxygen at a partial pressure of some 10 -6 mbars). This can be done either by stopping evaporation at a resistance setpoint measured in real time, or by comparing the resistance curve as a function of thickness to a reference curve, and adjusting in real time the oxygen flow or the aluminum evaporation rate to follow this reference curve.

[0036] A method according to the invention may further comprise a step of producing a resistor or electrode, called a protection resistor, between the mask and the substrate, preferably

[0037] REPLACEMENT SHEET (RULE 26) of high resistance value (greater than 1 MΩ, for example between 1 and 10 MΩ), for example in chrome. A chip or a deposition substrate (described later) according to the invention may comprise such a resistor or electrode, called a protective resistor, preferably of high resistance value (greater than 1 MΩ, for example between

[0038] I and 10 MQ), for example in chrome. This resistance - if present - can be electrically connected in parallel with the film to be deposited. It allows in particular to check the presence and good contact of the in-situ measurement substrate before the deposition is started (It may happen that this substrate is badly positioned and that the deposit is therefore not measurable during growth if it has not been possible to ensure this beforehand). It also makes it possible to limit the current passing through the film being deposited (it is progressively polarized in current, as it grows) and to avoid passing a strong current through the thin film just deposited, which, in the case of certain materials, heats them and modifies their properties. This resistance has for example a thickness between 3 and 100 nm, for example 10 nm. Preferably, this resistance is not located in the deposition window.

[0039] The substrate is for example made of silicon or quartz or sapphire.

[0040] It preferably has a surface, on which a deposit is to be made, with a roughness RA of, for example, between 0.01 nm and 1 nm. Such roughness ensures the continuity of the film between the measuring electrodes and thus allows a current to flow there from the first atomic layers. It is in fact very difficult to produce, in particular by evaporation or sputtering, a very thin film (for example with a thickness of between 1 nm and 50 nm), which is electrically continuous, if the substrate is not atomically flat.

[0041] The measuring electrodes can be made of Ti / Au, for example.

[0042] A method according to the invention may further comprise a step of producing a protective layer for the substrate, advantageously a protective layer on each of the 2 faces of said substrate. This protection may be implemented before cutting the substrate into individual / individual single-use deposition supports or chips.

[0043] REPLACEMENT SHEET (RULE 26) A method according to the invention may further comprise a prior step of planarizing the surface of the substrate.

[0044] Preferably, the deposition window has a transverse orientation, for example perpendicular, to that of at least a portion of the measuring electrodes.

[0045] For example, electrodes are made by evaporation at an angle, for example variable or fixed (with planetary rotation).

[0046] According to one embodiment, the electrodes have edges, forming gentle lateral slopes, with an angle with the surface of the substrate less than 80°, for example between 15° and 60° (or 50°).

[0047] The invention also relates to a support, or a chip, for thin film deposition, comprising: a) a substrate made of insulating or semiconducting material, b) a plurality of measuring electrodes produced on said substrate, each electrode having a central part and inclined edges and / or with a slope towards the surface of the substrate; c) a non-conductive deposition mask, defining a deposition window, this mask comprising notches in the vicinity of the substrate and said window.

[0048] This substrate has the advantages set out above in relation to the production process.

[0049] Such a deposition chip may also include a protective resistor, preferably with a resistance greater than 1 MΩ. This resistor is, for example, made of chrome. It may have a thickness of, for example, between 3 nm and 10 nm or even 100 nm.

[0050] The substrate is for example silicon or chrome or sapphire.

[0051] The measuring electrodes are for example made of Ti / Au.

[0052] A deposition chip according to the invention may further comprise a film or layer, for example made of plastic, for protection, in particular against scratches and dust. According to a preferred embodiment of a method for producing a film deposition support according to the invention, as described above and / or in the remainder of the present application and / or according to a preferred embodiment of a film deposition support, or chip,

[0053] SUBSTITUTE SHEET (RULE 26) thin according to the invention, the deposition window may have an orientation transverse to a plurality of measuring electrodes, for example an orientation perpendicular to that of at least a portion of the measuring electrodes.

[0054] In a deposition chip according to the invention, the electrodes may have edges, forming lateral slopes with an angle with the surface of the substrate less than 80°, for example between 15° and 60° (or 50°).

[0055] The invention also relates to a method for depositing a layer, for example a thin layer, for example with a thickness of between 1 nm and 100 nm or even 200 nm. Such a method comprises a step of depositing a layer in the deposition window of a support or a deposition chip according to the invention, and a measurement, preferably during said deposition, of at least one electrical quantity, for example the conductivity and / or the electrical resistance at zero frequency (or in direct current or in DC), or more generally the electrical impedance at finite frequency (or in alternating current or in AC) which gives simultaneous access to the resistance and / or the capacitance and / or the inductance at the terminals of at least 2 measuring electrodes.

[0056] From the resistance measurement, knowing the geometry of the measured wire, we can deduce a resistivity or a resistance per square, which is an intrinsic property of the film not dependent on the geometry.

[0057] An insulating film can be deposited to create, for example, a capacitance, in which case its impedance at finite frequency is measured.

[0058] A deposit can thus be made, partly on the substrate, partly on the electrodes, the latter making it possible to measure said electrical quantity, for example the electrical resistance and / or the capacitance and / or the inductance of the deposit or of the deposited layer. In such a method, the deposition of the layer can for example be obtained by sputtering, or by chemical vapor deposition technique or by evaporation by electron gun or by co-evaporation or by co-sputtering.

[0059] A deposition process according to the invention makes it possible to produce:

[0060] - a metallic layer formed from an element chosen for example from gold, silver, copper, platinum, iridium, titanium, vanadium, niobium, tantalum, chromium, etc.

[0061] SUBSTITUTION SHEET (RULE 26) - or a metallic layer comprising a metallic element in the presence of a reactive gas (oxygen, and / or nitrogen and / or hydrogen), such as for example granular aluminium (Al + O2), or aluminium nitrides, or titanium or niobium or silicon hydrides;

[0062] - or a deposit of a Niobium-silicon, or Yttrium-silicon, or Nickel-Chromium alloy;

[0063] - or a tunnel junction consisting of two metal deposits separated by an insulating barrier, for example a Josephson junction in AI-AIO X -AI, or in Nb-AI-AIO x -AI-Nb;

[0064] - or an insulating or semiconducting layer such as Si, or Si-O, or Si-H, or Ge; in this case we can use a simultaneous measurement of the capacitance and resistance of the layer.

[0065] The invention also relates to a method of etching a layer produced in the deposition window of a substrate or a deposition chip according to the invention, comprising a step of etching this layer, and of measuring at least one electrical quantity at the terminals of at least 2 measuring electrodes.

[0066] Such a process makes it possible, for example, to etch an oxide layer onto a layer of material, for example to be able to reestablish electrical contact.

[0067] Etching is carried out, for example, by ion beam or reactive plasma.

[0068] According to a particular embodiment of a method according to the invention, the measurement of at least one electrical quantity can be carried out using a micro-connector, for example a micro-USB connector.

[0069] The deposition or etching of the layer can be stopped when said electrical quantity reaches a target value.

[0070] During a deposition, the conditions thereof (for example pressure and / or temperature) can be adjusted based on the results of the measurement carried out in real time by the invention.

[0071] The invention also relates to the production of a film or a thin layer, while simultaneously carrying out, with the deposition of this film or this layer, a deposition on a chip according to the invention and / or according to a method according to the invention. The invention therefore makes it possible to replicate, for the chip and / or the method according to the invention, the conditions implemented

[0072] REPLACEMENT SHEET (RULE 26) for the deposit of interest, which is carried out in parallel, and thus to control the evolution of the latter, in particular from the point of view of the conductivity of the deposited film.

[0073] The layer deposited in a method according to the invention or on a chip according to the invention has, for example, a thickness of between 1 nm and 200 nm.

[0074] BRIEF DESCRIPTION OF THE DRAWINGS

[0075] -Figures 1A-1B represent steps in carrying out a method according to the invention; -Figure IC represents a deposit obtained by a method according to the invention;

[0076] -Figure 1D represents an alternative embodiment of a method according to the invention;

[0077] -Figure 1E represents a deposit made on a chip obtained by the process variant according to the invention;

[0078] - figures 2A - 2C represent a deposition substrate (figure 2A), produced in accordance with the invention, a deposited film (figure 2B), and an enlargement thereof (figure 2C);

[0079] - figure 3 represents a plurality of chips according to the invention produced on a “wafer”;

[0080] - Figure 4A is a view of an individual chip produced in accordance with the invention;

[0081] - Figure 4B is a view of an example of use of the device according to the invention, comprising the chip inserted into a micro USB connector and connected to a measuring instrument, placed next to 3 other samples of interest, on which the thin-layer film is deposited simultaneously;

[0082] - figures 5A - 5D represent various measurements carried out using in particular a device according to the invention (figures 5A, B, D).

[0083] - Figures 6A - 8C represent various other measurements carried out using a method and a deposition chip according to the invention.

[0084] SUBSTITUTE SHEET (RULE 26) DETAILED DISCLOSURE OF THE INVENTION

[0085] Steps of an embodiment of a method according to the invention will be explained in connection with Figures 1A - 1B. This method leads to the production of a support or a chip on which it will then be possible to carry out a deposit.

[0086] Electrodes 2 (figure 1A, which is a view in a YZ plane), for example in Ti / Au, are produced on a substrate 4, for example in Silicon covered with a layer of SiO2 (for example 500 nm thick). At least 2 of these electrodes are produced, but preferably (for reasons of precision) a higher number are produced, for example 4 electrodes.

[0087] Preferably, each of these electrodes has edges 2i, 22 (figure 1A), forming gentle lateral slopes, with an angle a: this angle is measured in the plane (yOz), at the edge of the electrodes, between the lower face of the electrode 2 (interface with the substrate 4) and its upper face (interface with the air), for example between 15° and 50°. In other words, the thickness of each electrode decreases progressively from the top thereof to the surface of the substrate 4. To achieve this inclination, evaporation under angle can be carried out with a variable angle, or a fixed angle and a planetary rotation.This inclination makes it possible, in particular for very thin films 20, for example with a thickness of less than 50 nm or 60 nm, to subsequently produce a continuous deposit 20 (see figure IC), both on the surface of the substrate 4 and of the electrodes 2, to form, from the first nanometers deposited, an electrical continuity between all the electrodes 2, thus allowing in-situ measurement. This inclination is particularly important for very thin films 20, for example with a thickness of less than 50 nm or 60 nm, or as a general rule with a thickness less than approximately 2 times the thickness of the electrodes 2, specifically if these are not deposited by ALD technique (“Atomic Layer Deposition”).

[0088] In their thickest part, these electrodes 2 have for example a thickness of a few tens of nm, for example still between 10 nm and 50 nm, by

[0089] SUBSTITUTION SHEET (RULE 26) example still about 40 nm, more generally less than 100 nm thick or

[0090] 200 nm.

[0091] Preferably, the ends of these electrodes opposite the deposition window form contact pads 2c for connection to power supply and / or measurement means (see figures 2A).

[0092] On the same substrate, provided with electrodes 2 (figure 1B, which is a view in the XoZ plane), a resin mask 6 is deposited in order to define a deposition window 8. This mask has notches 10 in the part close to the substrate and to the zone 8 in which the deposition will be carried out. The notches 10 are protected from deposition by an overhang 61 of the resin mask 6. Thus the deposition of material will be interrupted at the level of the notches 10 and the measured film will have a geometry defined by the window 8; the material deposited on the mask 6 will not be electrically connected to the material deposited on the substrate; such lateral deposits would interfere with and distort the resistance measurement. The material of the lower part of the mask is removed by selective etching in the region in the vicinity of the substrate 4 and close to the deposition window 8.The shape of this mask defines the geometry of the deposit to be made subsequently and for which we will wish to measure an electrical quantity in situ, during growth, using the electrodes 2. This well-defined geometry contributes to very good precision in measuring the conductivity of this deposit (if applicable, its resistance per square or its susceptance), for example better than 1%. Figure IC represents a deposit 20 made on the chip of Figure IB, in a sectional view along the YOZ plane (Figure IB). It should be noted that the sectional view of Figure IC is independent of the variant (with or without protective resistance).

[0093] Thus, a region 8 is defined for a future deposition, above the electrodes 2 and on the surface of the substrate 4, between the edges of the resin mask 6. It is this deposit whose resistance will be measured, for example during an evaporation process, and using the electrodes 2. The geometry of this deposit is thus defined precisely, in particular thanks to the notches 10, which allows a very good measurement of the resistivity of the evaporated film. A particularly advantageous embodiment is that of a deposition region

[0094] REPLACEMENT SHEET (RULE 26) which extends along an X axis, perpendicular to the Y direction in which the electrodes 2 extend in the measurement region.

[0095] Window 8 can be positioned above all the measuring electrodes to allow a deposited film to cover them all in part and electrically connect them together through a track of well-defined geometry.

[0096] Alternatively (Figure 1D), after the formation of the electrodes 2 but before the formation of the mask 8, one or more resistors 12 called protection resistors are produced, preferably of high value, for example greater than 1 MOhm, possibly less than 100 MOhms. This resistor is for example made of Cr. Its thickness can be of the order of a few nm, for example between 4 nm and 10 nm, or even greater (for example up to 100 nm). This resistor is deposited on the electrodes 2, across and above the latter, and it will be electrically connected in parallel with a deposited film. It makes it possible to check the presence and good contact of the in-situ measurement chip before the deposition is started (it may happen that the chip is badly positioned and that the film is therefore not measurable during growth if this could not be ensured beforehand).It also limits the current passing through the thin film during the first nanometers of deposition, which, in the case of certain materials, heats them up and modifies their properties.

[0097] These problems (ensuring that the control chip can be measured in situ before deposition has begun; limiting the current flowing through the film being deposited and thus avoiding film damage) can in some cases prevent in situ measurement, and the presence of this protective resistor helps overcome them.

[0098] Figure 1E shows a deposit 20 made on the chip of Figure 1D, in a sectional view along the same plane XOZ as Figure 1D. The deposit 20 has a geometry defined by the shape of the mask 8.

[0099] Whatever the embodiment, a deposition chip 40 has thus been formed. This chip comprises the substrate 4, the electrodes 2, optionally the resistor(s) 12, and the deposition window 8, delimited by the mask 6. It has, for example, dimensions of 3.5 mm x 7 mm x 350 pm, allowing it to be inserted into a female micro USB type connector, the internal dimensions of which are approximately 3.6 mm wide, 3.6 mm long and 3.6 mm wide.

[0100] REPLACEMENT SHEET (RULE 26) depth and 0.7mm thick. When the chip is inserted into such a connector, the connector's spring contacts rest on the contact pads 2c, and the part with the deposition window 8 is exposed.

[0101] Deposition can be performed on this chip, for example by electron gun evaporation, or by sputtering, or by co-evaporation or by co-sputtering or chemical vapor deposition.

[0102] Prior to any deposition, including that of the electrodes 2, the surface of the substrate 4 may be subjected to a process to reduce its roughness, for example to obtain a roughness RA of between 0.01 nm and 1 nm. This step contributes to good continuity of the thin films, such as the film 20, which have a nanometric thickness, for example between 5 nm and 50 nm, and which will be produced on the chip.

[0103] This roughness control ensures the continuity of the film between the measuring electrodes and thus allows a current to flow through it, from the first atomic layers. It is indeed very difficult to produce (particularly by evaporation or sputtering) a very thin film (for example with a thickness between 1 nm and 50 nm), which is electrically continuous, if the substrate is not atomically flat.

[0104] Figure 2A represents a chip 40 according to the invention, ready to receive a deposit in the window 8. The section along plane I corresponds to figures 1A and 1C (respectively before and after deposition of the film 20), the section along plane II corresponds to figure 1E (after deposition of the film 20), the section along plane III corresponds to figures 1B and 1D (before deposition of the film 20). In this figure 2A, we see 4 different conductors or electrodes 2 which, at least in the deposition zone 8, extend parallel to each other and in the direction X, and the resin mask 6 which defines the deposition window 8, which extends in the direction Y perpendicular to X.The outermost electrodes 2 can be connected, by the contact pads 2c, to a current source 14 and a voltage can be measured with a voltage measuring device 16 connected to the other two electrodes; alternatively, one of the two electrodes located on the same side of the deposition support (relative to the middle of the support in the y direction) can be connected to a positive terminal of a current source, the other electrode on the same side to the positive terminal of a voltmeter.

[0105] REPLACEMENT SHEET (RULE 26) electrodes located on the other side of the support will be connected to the negative terminal of the current source and the voltmeter; alternatively, for a measurement using only two electrodes, the contact pads 2c can be connected to a voltage source and a current can be measured with a device such as an ammeter. If a protective resistor 12 has been made as explained above in connection with figures 1C and 1D, it can be used to test the presence and positioning of the chip in a measurement device, even before the sample is deposited. Advantageously, the ends 2e 2c of the electrodes 2 to be connected to a current source 14 and to the voltage measurement device 16 are wider to facilitate contacts.

[0106] The invention therefore makes it possible to produce a deposition and measurement chip 40, which comprises electrodes 2 which will make it possible to carry out a measurement of the thin layer of interest subsequently deposited; thus, a very precise value of the conductivity (or for example of the resistance) of this thin layer is obtained.

[0107] Figures 2B and 2C represent successive enlargements of a deposition chip 40 (or chip) according to the invention, on which the deposition zone 8 and the mask 6 or parts thereof are recognized, in particular in Figure 2C where the notch 10 is visible.

[0108] These figures were obtained from photos taken with a 15keV scanning electron microscope, under the following experimental conditions:

[0109] - Substrate 4 of 350 pm, Si / SiOz of 500 nm thickness;

[0110] - 2 electrodes of titanium and gold 40 nm thick;

[0111] - mask resin 6: LOL2000- S 1813 with respective thicknesses of 200nm and 1.4pm;

[0112] The region between electrodes 2 and mask 6 in deposition window 8 designates the portion of the film whose resistance is measured during evaporation. As seen in Figure 2B, in this example, a wire with an aspect ratio of 5 squares is deposited.

[0113] Such chips are preferably made collectively. Thus, as seen in Figure 3, a plurality of individual chips 40 (up to several dozen, for example about 50) can be made on a “wafer” 32 with a diameter of for example 2 inches. Each chip is preferably single-use.

[0114] SUBSTITUTE SHEET (RULE 26) The substrate 32 thus produced, comprising a plurality of chips 40, may be protected by a protective layer 30 (FIG. 3), for example a layer of adhesive of the type used in a clean room, preferably on both sides; FIG. 3 does not show the layer 30 on the top surface to allow the individual chips 40 to be seen.

[0115] This substrate can then be cut, for example with a diamond saw, into single-use chips 40. Such a chip is visible in Figure 4A. It is thus possible to obtain up to several dozen, for example around 50, such individual chips on a wafer 32, for example 2 inches. The footprint of each chip is preferably the dimensions of a micro-USB connector 42, as understood in Figure 4B and the dimensions which have already been indicated above. This very reduced size makes it possible to mechanically fix the measurement support, including the chip, the connector and its cable, as close as possible to the sample to be deposited, avoiding problems of shadowing and spatial inhomogeneity.

[0116] Alternatively, another type of connector (pogo type, or spring-loaded blades) can be used; however, USB offers excellent compactness for a system combining the functions of holding and electrical connection.

[0117] Such a connector and its wires can be integrated into a housing without disturbing the deposit.

[0118] At each deposition, the user removes the possible protective layer 30 from one of the chips, and slides it into the connector (as in figure 4B). In less than a minute the device is installed and ready to measure. The user can check that the chip is correctly inserted thanks to the protective resistor 12, if present. The measurement can be carried out simply for example using an RLC bridge (not shown in the figures), which can be of commercial type, easily interfaced on the deposition equipment, to stop the deposition when a resistance setpoint is reached. Alternatively, one can measure with a DC multimeter, of the SMU type; this 2nd method is more precise, and can be implemented when one wishes to measure for example very weak oxide layers on a very conductive material.

[0119] The example of a silicon substrate 4 was given above, but a substrate of another material having a crystalline structure, for example quartz or

[0120] REPLACEMENT SHEET (RULE 26) sapphire. The nucleation of thin-film layers on a crystalline substrate, as well as the resistivity of the resulting thin layers, depends on the lattice parameters of the substrate and those of the deposited material; a crystalline substrate with a lattice parameter adapted to the deposition to be carried out is therefore chosen. Choosing the same substrate for the deposition and for the in-situ measurement allows the result to be reproduced most faithfully.

[0121] As explained above, in a variant of a method and a device according to the invention, a protective resistor 12 is produced, for example in Cr. This resistor makes it possible, on the one hand, to limit the current in the layer during growth and thus to avoid heating (and annealing) of this layer, linked to its electrical measurement and, on the other hand, to ensure the presence and proper functioning of the measurement substrate before the start of deposition. However, being connected in parallel with the layer which will be deposited, it imposes an upper limit on the measurable value of the resistance of the deposited film, typically of the same order of magnitude as the resistor 12. It will be possible to use a substrate without a protective resistor 12 in cases where it is desired to measure very high surface resistance values, and if necessary to use more precise measurement equipment, with integrated current limitation and / or amplifier.

[0122] Figures 5A - 5D represent different measurements of different characteristics, carried out in particular using a deposition support according to the invention, during evaporation of an aluminum layer at a speed of 1 nm / s, under a partial oxygen pressure of 2.10 -5 mbar on a Si / SiOz substrate:

[0123] - Figure 5A represents the resistance measurement, carried out with a LCR819 type bridge and divided by the number of squares (here 5, see for example figure 2B), thus providing the resistance per square Rc of the deposited layer as a function of time t. The first points of the acquisition (before 3.5s) are beyond the measurement range of the device, and / or before the film is electrically continuous;

[0124] - Figure 5B represents the deposited thickness e, measured with a quartz balance, as a function of time; we see that a deposit according to the invention can be produced for a thickness between a few nm, between for example 5 nm and 30 nm or 40 nm;

[0125] - Figure 5C represents the resistance per square Rc as a function of the deposited thickness e (two quantities recorded simultaneously during deposition). The electrical measurement is

[0126] REPLACEMENT SHEET (RULE 26) possible from a thickness of 3.5nm. The first measured point corresponds to a resistance of 20MΩ, at the upper limit of the measurement range of the device used for this experiment.

[0127] - Figure 5D represents the resistivity of the film as a function of its thickness e, this resistivity being calculated as the product of Rc and t.

[0128] The deposition of the film is stopped when the target value of 260 Q of the resistance per square is obtained, target value represented by curve 44 in broken lines in Figures 5A, 5C and 5D.

[0129] A chip according to the invention can be connected, for example by a connector as mentioned in this description, to a measuring device itself interfaced on a computer or microcomputer which makes it possible to collect and / or process and / or store measured data, in particular conductivity data (therefore including capacitance and / or inductance data) or resistance and / or thickness data and possibly to display them on visualization means such as a screen. These figures show that the measured electrical quantity (here the resistance) can converge towards a target value fairly quickly; the invention is therefore entirely suitable for practical implementation, to produce films with a thickness for example between a few nm and 100 nm or even a thickness of the order of a few hundred nm. In fact, the thickness that can be deposited is mainly limited by the height of the notches 10 (as illustrated in FIG. 1B).Furthermore, the accuracy of the final characteristics of the device will depend on the resistivity of the layers and the accuracy of the measuring device. For example, if we use a resin 6 of type LOL2000 in which the notches 10 can be up to 200 nm high, we will be limited to a deposit with a thickness of approximately 200 nm in order not to make an electrical contact on the edges of the mask. Generally speaking, we can deposit films with a thickness in the entire range of thicknesses commonly used in quantum circuit applications.

[0130] In addition, it is possible to place wires and a measuring box in the vacuum or ultra-vacuum of the deposition system, for example an evaporator, without damaging it.

[0131] REPLACEMENT SHEET (RULE 26) Depending on the materials constituting the elements present on the chip, care should be taken not to heat above a limit temperature so as not to deform these elements. For example, for Au electrodes, as well as for the S1813 resin used for mask 6, it is preferable not to heat the measurement box above a limit temperature, here around 150°C.

[0132] Whatever the implementation, it is possible to cool the measurement sample in situ if the deposition is done cold, without limit on the low temperature.

[0133] The invention makes it possible, for example, to control in situ the manufacture of a film, by carrying out, simultaneously with the deposition of this film, a deposition on a chip according to the invention and / or according to a method according to the invention. The invention makes it possible to replicate, for the chip and / or the method according to the invention, the conditions implemented for the deposition of interest, which is carried out in parallel, simultaneously, and thus to control the evolution of the latter, in particular from the point of view of the conductivity of the deposited film.

[0134] In such a method, one or more steps of depositing one or more films (or samples) that one wishes to manufacture can be carried out and, in parallel, a measurement can be carried out using a chip and / or a method according to the invention. A method of manufacturing a sample can comprise numerous film deposition steps, and at each of them, this deposition can be controlled independently using a chip or a method according to the invention.

[0135] Indeed, in a deposition chamber, we can assume that the deposition is homogeneous and will be the same for the deposition measured using a chip and / or a method according to the invention and for the sample being manufactured.

[0136] So we can have:

[0137] Realization of a 1 er deposit (more generally of a n ème deposit, n>l) of a sample to be produced and, simultaneously, on a chip and / or according to a method according to the invention;

[0138] Production of a 2 ème deposit (more generally of order n+1), for example on the 1 er deposition (more generally on the n-order deposition), of the sample to be produced and, simultaneously, on the chip and / or according to a method according to the invention.

[0139] REPLACEMENT SHEET (RULE 26) The invention therefore applies to the production of an nth deposit, of the sample to be produced and, simultaneously, on the chip and / or according to a method according to the invention.

[0140] The invention makes it possible, for example, to control in situ the manufacture of Josephson junctions for quantum circuits, by measuring in real time the surface oxidation rate of an aluminum film already deposited and by stopping the oxidation on a resistance setpoint. Another application is the control of the reproducibility of the surface resistance of granular aluminum films (Aluminum evaporated in the presence of oxygen at a partial pressure of some 10-6 mbar). This can be done either by stopping evaporation at a resistance setpoint measured in real time, or by comparing the resistance curve as a function of thickness to a reference curve, and adjusting in real time the oxygen flow or the aluminum evaporation rate to follow this reference curve.

[0141] The invention has been described above in the case of a deposition. Another application of the invention is the monitoring of the resistance of a layer during etching, for example by an ion beam or a reactive plasma. The invention makes it possible, for example, to stop etching when the surface oxide layer is removed or, more generally, when the desired conduction properties are achieved; the etched layer is formed by a method according to the invention, i.e. by controlling its resistance during its formation. This allows, for example, good contact recovery on a layer previously manufactured and having undergone lithography steps, aging and / or air oxidation. For this, the chip preferably has the same manufacturing history as the sample of interest.

[0142] Whatever the application, it is possible, during deposition and / or oxidation and / or etching, to regulate the parameters of the deposition machine according to the observed electrical values.

[0143] One field of application of the invention concerns quantum circuits integrating superconductors, Josephson junctions, or more generally thin films (deposited for example by electron gun), of which we wish to control the surface resistance, the capacitance value, or the inductance value with a precision better than 1%, 0.1% or 0.01%.

[0144] SUBSTITUTE SHEET (RULE 26) The invention may also be applied to any type of thin film deposition (e.g. by sputtering, or by chemical vapor deposition) for which such precision is required.

[0145] Many deposition methods are compatible with resistance measurement and with the introduction into the deposition machine of cables and connectors allowing a measurement according to the invention. Depending on the deposition method, it will be possible to filter the measured signals, or to check that the chip carrier materials are not degraded by reactive species of a plasma, etc.

[0146] Examples of results obtained with a deposition chip according to the invention will be presented.

[0147] A first example (figures 6A and 6B) concerns an application to the monitoring of a metal deposit with the protection resistor 12 (which shows its usefulness). Figure 6A represents the evolution of a measured resistance (curve 1e) as a function of time, divided by the number of squares (there are 5 in this example) of the deposition window. Curve 1e represents the evolution of the thickness, measured simultaneously with a quartz balance.

[0148] Figure 6B represents the evolution of this same resistance as a function of the thickness, in particular in the last decade of the resistance scale (corresponding to a thickness substantially between 3 nm and 15 nm). The deposition is stopped at a resistance value of 57 Q, which corresponds to a thickness of 15 nm.

[0149] At the start of deposition (at t=0) no film has yet been deposited, the device measures the protection resistance of 5 MΩ, which results in an arbitrary value of 10 6 Q / square (see the constant part of the I curve between t=0 and t=4s). This indicates the correct connection of the in situ measurement chip.

[0150] After 4 seconds (see curve le), a duration which corresponds to a film thickness of 2 nm, the resistance of the latter is of the order of the shunt resistance and begins to be measurable by the device.

[0151] For a resistance below 100 kΩ / square (which corresponds to a thickness of approximately 2.5 nm) the measured resistance value is dominated by that of the film which

[0152] REPLACEMENT SHEET (RULE 26) increases (the 5 MΩ shunt resistance no longer plays a role, since the resistance of the film is very low compared to that of the shunt).

[0153] The initial evolution of the curve le, in the form of staircase steps, is attributed to a change in the measuring range of the device and to an instrumental limitation that can be overcome with better quality equipment.

[0154] Evaporation stops at the desired square resistance, here at a value of approximately 57 ohms (see horizontal dashed line).

[0155] Another example (figures 7A and 7B) concerns an application to the monitoring of the evolution of a chromium layer under oxidation (after deposition) and the effectiveness of an encapsulation layer.

[0156] Figure 7A shows the time-dependent evolution of the square resistance of a 15 nm thick uncoated chromium layer when exposed to air just after deposition. The resistance evolves slowly with time (only the first 120 seconds after opening the deposition chamber are shown here) and continues to evolve over the following days and months.

[0157] Figure 7B shows the time-dependent evolution of the square resistance of a 10 nm thin chromium film coated with 20 nm Al I2O3 when exposed to air just after deposition. Oxidation of the film is stopped by the coating.

[0158] Yet another example (Figures 8A - 8C) concerns an application to the in situ monitoring of the etching of a 30 nm thick, non-oxidized evaporated aluminum layer during etching with an argon beam.

[0159] Figure 8A represents the evaporation step (curve Is: evolution of the resistance as a function of time, curve Ils: evolution of the thickness), Figure 8B the etching step, and Figure 8C the evolution over time of the calculated thickness Ise and the etching rate or speed ls v , also calculated.

[0160] In situ measurement allows the characterization of the etching rate or speed in a given device. An etching step can be used, for example, to ensure good

[0161] REPLACEMENT SHEET (RULE 26) contact between 2 metals, during a manufacturing step, or to remove a protective layer, or to finely adjust the resistance of a deposited layer.

[0162] SUBSTITUTION SHEET (RULE 26)

Claims

CLAIMS 1. Method for producing a chip (40) for depositing thin films, comprising: a) - the formation, on an insulating or semi-conducting substrate (4), of a plurality of measuring electrodes (2), each electrode having a central part and edges (2i, 2z) inclined towards the surface of the substrate (4); b) - the formation of a non-conductive deposition mask (6), defining a deposition window (8), above the electrodes (2) and on the surface of the substrate (4), between edges of the resin mask (6), this mask comprising notches (10) in the vicinity of the substrate and said deposition window.

2. Method according to claim 1, further comprising a step of producing a protective electrode (12) between the mask (6) and the substrate (4).

3. Method according to claim 2, the protective electrode having a resistance greater than 1 MΩ.

4. Method according to claim 2 or 3, the protective electrode being made of chrome and / or having a thickness of between 3 nm and 100 nm.

5. Method according to one of claims 1 to 4, the substrate (4) being made of silicon or quartz or sapphire.

6. Method according to one of claims 1 to 5, the substrate having a surface roughness RA of between 0.01 nm and 1 nm.

7. Method according to one of claims 1 to 6, the measuring electrodes (2) being made of Ti / Au.

8. Method according to one of claims 1 to 5, further comprising a step of producing a protective layer (30) for the substrate. SUBSTITUTION SHEET (RULE 26) 9. Method according to one of claims 1 to 8, the deposition window (8) having an orientation perpendicular to that of at least part of the measuring electrodes (2).

10. Method according to one of claims 1 to 9, the electrodes (2) being produced by angle evaporation.

11. Method according to one of claims 1 to 10, the electrodes (2) having edges (2i, 2z), forming lateral slopes, with an angle, with the surface of the substrate, less than 80°, for example between 15° and 60°.

12. Method according to one of claims 1 to 11, comprising a prior step of planarizing the surface of the substrate (4).

13. Thin film deposition chip (40), comprising: a) a substrate (4) made of an insulating or semiconducting material b) on said substrate (4) a plurality of measuring electrodes (2), each electrode having a central portion and edges (21, 22) inclined towards the surface of the substrate (4); c) a non-conductive deposition mask (6), defining a deposition window (8), above the electrodes (2) and on the surface of the substrate (4), between edges of the resin mask (6), this mask comprising notches (10) in the vicinity of the substrate and of said deposition window.

14. Chip according to claim 13, further comprising a protective electrode (12) between the mask (6) and the substrate (4).

15. Chip according to claim 14, the protective electrode having a resistance greater than 1 MΩ. SUBSTITUTION SHEET (RULE 26) 16. Chip according to claim 14 or 15, the protective electrode being made of chrome and / or having a thickness of between 3 nm and 10 nm.

17. Chip according to one of claims 13 to 16, the substrate (4) being made of silicon or chrome or sapphire.

18. Chip according to one of claims 13 to 17, the measuring electrodes (2) being made of Ti / Au.

19. Chip according to one of claims 13 to 18, further comprising a layer (30) for protecting the substrate.

20. Chip according to one of claims 13 to 19, the deposition window (8) having an orientation perpendicular to that of at least part of the measuring electrodes (2).

21. Chip according to one of claims 13 to 20, the electrodes (2) having edges (2i, 2z), forming lateral slopes, with an angle less than 80°, for example between 15° and 60°.

22. Method for depositing a layer, called a thin layer, comprising a step of depositing a layer in the deposition window (8) of a chip according to one of claims 13 to 21, and of measuring at least one electrical quantity at the terminals of at least 2 measuring electrodes (2).

23. Method according to claim 22, the deposition of the layer being obtained by sputtering, or by chemical vapor deposition or by electron gun or by coevaporation or by co-sputtering.

24. Method according to one of claims 22 or 23, the deposited layer forming: SUBSTITUTION SHEET (RULE 26) - a metallic layer formed from an element chosen from gold, silver, copper, platinum, iridium, titanium, vanadium, niobium, tantalum, chromium, etc.; - or a metallic layer formed from an element in the presence of a reactive gas (oxygen and / or nitrogen and / or hydrogen), such as for example granular aluminium (Al + 02), or aluminium nitrides, or titanium or niobium nitrides, or silicon hydrides; - or a deposit of a Niobium-silicon, or Yttrium-silicon, or Nickel-Chromium alloy; - or a tunnel junction comprising two metal deposits separated by an insulating barrier, for example a Josephson junction in AI-AIO X -AI, or in Nb-AI-AIO x -AI-Nb ; - or an insulating or semiconducting layer such as Si, or Si-O, or Si-H, or Ge; in this case we can use a simultaneous measurement of the capacitance and resistance of the layer.

25. Method according to one of claims 22 to 24, the deposited layer having a thickness of between 1 nm and 200 nm.

26. Method according to one of claims 22 to 24, the deposited layer having a thickness of between 1 nm and 60 nm.

27. Method for producing a sample comprising a plurality of films or layers, this method comprising, simultaneously with the deposition of each film or each layer, carrying out a method according to one of claims 22 to 26.

28. Method of etching a layer produced in the window (8) of a chip according to one of claims 13 to 21, comprising a step of etching this layer, and measuring at least one electrical quantity at the terminals of at least 2 measuring electrodes (2).

29. Method according to one of claims 22 to 29, the deposition or etching of the layer being stopped when said electrical quantity reaches a target value. SUBSTITUTION SHEET (RULE 26) 30. Method according to one of claims 22 to 29, the measurement of at least one electrical quantity being carried out using a micro-connector, for example a micro-USB connector.

31. Method according to one of claims 22 to 30, at least one measured electrical quantity being the conductivity or electrical resistance of a layer being deposited or being etched and produced partly on the substrate (4), partly on the electrodes (2). SUBSTITUTION SHEET (RULE 26)

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