OPTIMIZATION OF THE ORIENTATION OF SUBSTRATES PASSING IN BATCHES THROUGH CHEMICAL TREATMENT BATHS

Abstract

A treatment process applied to a plurality of substrates (Sub) held parallel to each other, the treatment comprising at least two successive treatment sequences, each sequence comprising at least one immersion in at least one chemical bath contained in a vessel equipped with an injection manifold for a treatment solution, the injection manifold comprising dispensing nozzles, the nozzles being distributed along the injection manifold, the substrates (Sub) each being arranged substantially perpendicular to the injection manifold, wherein: a first of the at least two immersions is carried out with the substrates (Sub) oriented according to a first orientation (Or1), located angularly around an axis normal to the substrates; and a second of the at least two immersions is carried out with at least a portion of the substrates oriented according to a second orientation (Or2), distinct from the first orientation (Or1). Figure to be published with the abstract: Fig. 5

Description

Title of the invention: OPTIMIZATION OF THE ORIENTATION OF BATCH-FEEDING SUBSTRATES IN CHEMICAL TREATMENT BATHS TECHNICAL FIELD OF THE INVENTION

[0001] The invention relates to a chemical treatment process used in the semiconductor industry, applied to substrates held parallel to each other in baths of chemical solutions injected by means of an injection ramp equipped with nozzles distributed along its length. TECHNOLOGICAL BACKGROUND

[0002] In semiconductor manufacturing, wet immersion benches, usually referred to as "Wet Benches," are used for various surface treatment processes of the substrates used, such as etching, cleaning, and resin stripping. A Wet Bench can be described as a chemical fume hood comprising several baths, usually automated to process batches of semiconductor wafers or other materials used in this industry for various applications, such as CMOS (Complementary Metal Oxide Semiconductor) circuits, power electronics circuits, MEMS (Micro Electromechanical Systems), radio frequency filters, or pLEDs (Light Emitting Diodes).

[0003] The substrates concerned are typically circular wafers, with standardized diameters ranging from 25.4 mm to 300 mm and a thickness of approximately 0.7 mm, for example, wafers of silicon, Pyrex, sapphire, silicon carbide, gallium arsenide, aluminum nitride, etc. For reasons of automation and efficiency, the substrates are processed in batches, handled using plastic baskets called FOUPs (Front Opening Unified Pods). FOUPs are generally designed to hold 25 substrates to be processed, keeping the substrates parallel to each other, with spacings of approximately one centimeter between two substrates.

[0004] The substrates can thus be automatically immersed in batches in successive chemical treatment baths. More specifically, a Wet Bench can comprise several tanks, each dedicated to a particular chemical treatment using specific solutions, for example, acidic solutions, basic solutions, solutions composed of solvents, or simply deionized water for rinsing. A robot transfers the substrates from the FOUPs into handling baskets specifically designed for wet treatment in the baths and immerses them successively in the baths necessary for the implementation of a treatment recipe. Between two baths, respectively part of two treatment sequences, the substrates can be isolated for characterization, for example of their flatness, their roughness, or any other parameter relevant to their treatment, or for operations such as heat treatments.

[0005] Figure 1(A) shows, from a top view, a schematic view of a typical bath B, comprising an outer tank OutTank and an inner tank InnTank located inside the outer tank. The tanks are designed so that the treatment solution contained in the inner tank can overflow and be collected by the outer tank. A collector Coll is located in the inner tank for receiving a liquid treatment solution for distribution to one or more injection ramps InjRmp for injecting the treatment solution into the bath. The ramp(s) are connected to the collector so as to distribute the solution into the bath by means of nozzles No arranged along their horizontal X direction of extension. Thus, the inlet Ent of a ramp is located at the collector Coll and its distal end Dist is located opposite the collector Coll.If multiple ramps are used, they can be spaced along a horizontal Y direction perpendicular to the X direction.

[0006] Fig. 1(B) illustrates bath B in a side view along a vertical plane. The injection ramps InjRmp are located in the lower part of the inner tank InnTank. When substrates Sub are being processed in bath B, they are placed and held in the inner tank InnTank by means of a handling basket (not shown in this figure) above the injection ramps. The orientation of the substrates transferred from a FOUP to a handling basket for wet processing is maintained, so that the orientation of a substrate in a FOUP corresponds to the orientation of that substrate in the processing baths into which it is successively immersed.

[0007] Fig.1(C) reproduces Fig.1(B), with the added arrows representing the flow of the treatment solution, in this order from the Coll collector, through the InjRmp ramp(s) and then the No nozzles, into the inner tank InnTank and between the Sub substrates and, finally, the continuous injection of the treatment solution into the inner tank causes the latter to overflow into the outer tank OutTank.

[0008] The applied treatments may lead to substrate thinning. For example, the successive application of oxidizing and deoxidizing treatments to a silicon substrate leads to the oxidation of the silicon surface and then the removal of the oxide layer formed. Thus, inhomogeneities in the surface topography of the substrate may appear.

[0009] These irregularities may be negligible for many applications, but for example in cases where thin films of active materials are on a substrate In these substrates, irregularities can become unacceptable. This is the case, for example, with substrates known as SOI (Silicon-On-Insulator) or FD-SOI (Fully Depleted SOI), where the active surface layer may be only a few tens of nanometers thick. In these types of applications, the appearance of inhomogeneities in the surface topography of the layers leads to the rejection of substrates deemed non-compliant with the end user's specifications.

[0010] There is therefore a need to improve the homogeneity of the chemical treatments implemented in wet benches. Description of the invention

[0011] The applicant's objective is to provide a process for treating substrates by batch chemical baths, the process improving the homogeneity of the thicknesses of substrates thus treated.

[0012] To achieve this objective, one aspect of the invention is a treatment method applied to a plurality of substrates held parallel to each other, the treatment comprising at least two successive treatment sequences applied to the substrates, each of the sequences comprising at least one immersion in at least one chemical bath contained in a vessel equipped with an injection manifold for a treatment solution, the injection manifold comprising nozzles for distributing the treatment solution, the nozzles being distributed along the injection manifold, the substrates each being arranged substantially perpendicular to the injection manifold, wherein:

[0013] - a first of at least two soakings is carried out with the substrates oriented according to a first orientation, located angularly around an axis normal to the substrates; and

[0014] - a second of the at least two soakings is carried out with at least a part substrates oriented according to a second orientation, distinct by at least 20° from the first orientation.

[0015] A surprising advantage of changing the orientation of the substrates between two successive wet treatment sequences is that it improves the homogeneity of the surface topography of the treated substrates. This improvement in surface topography can refer to the maximum variations or the standard deviation of the distance from the surface to a median position.

[0016] Applied in particular to the manufacture of FD-SOI type substrates, the process according to the invention makes it possible to improve the overall yield of the manufacturing process by reducing the proportion of substrates not meeting the required specifications. The specifications referred to here relate to the surface topography of the substrates.

[0017] According to additional, non-limiting features of the treatment process according to the invention, considered individually or in any technically feasible combination:

[0018] - the second of the at least two soakings can be carried out with all of the substrates oriented in the second orientation;

[0019] - the second of the at least two soakings can be carried out with first substrates of the plurality of substrates oriented according to the first orientation, and of the second substrates of the plurality of substrates oriented according to the second orientation;

[0020] - the first substrates can be closer to a ramp inlet injection than the second substrates;

[0021] - the method may further include a topography calibration step of the substrates between the first and second of at least two dippings, the positions of the second substrates being able to be determined in response to the calibration step; and

[0022] - the second orientation can be substantially opposite to the first orientation.

[0023] The invention extends to a method for manufacturing a substrate comprising the steps to assemble a donor substrate and a recipient substrate; then to separate a thickness of the donor substrate at the level of a weakening plane formed in the donor substrate, so as to provide the recipient substrate with a thin layer from the donor substrate; then to apply to the recipient substrate provided with the thin layer the treatment process according to the invention.

[0024] According to additional non-limiting features of the manufacturing process of a substrate according to the invention, considered individually or in any technically feasible combination:

[0025] - each of the sequences may comprise a plurality of dips in a plurality of chemical baths each contained in a container equipped with an injection ramp for a treatment solution, the ramps possibly including nozzles for distributing the treatment solutions, the substrates possibly being, during each of the soakings, each arranged substantially perpendicular to the injection ramp of the bath in which they are soaked, process in which: first soakings of the first sequence can be carried out with the substrates oriented according to the first orientation; and second soakings of the second sequence following the first sequence can be carried out with at least part of the substrates oriented according to the second orientation;

[0026] - the first soakings of the first sequence may include a step of cleaning, the first sequence may also include a first step oxidation, and the second soakings of the second sequence may include a first deoxidation step;

[0027] - the treatment process may include a third treatment sequence applied to the substrates, the second sequence and may include at least a third soaking in at least one chemical bath contained in a vessel equipped with an injection manifold for a treatment solution, the injection manifold may include nozzles for distributing the treatment solution, the nozzles may be distributed along the injection manifold, the substrates may each be arranged substantially perpendicular to the injection manifold, process in which: the second sequence may include a second oxidation step; the at least one soaking of the third sequence may include a second deoxidation step; and the third sequence may be carried out with the substrates oriented in a third orientation substantially different from the first and second orientations, the third orientation being able to be located angularly around the axis normal to the substrates;

[0028] - the thin film can have a thickness between 50.10 100 µm and 200.10 10 µm, preferably between 100.10 10 m and 140.10 10 m at the end of the treatment process;

[0029] - the thin film may include a silicon layer;

[0030] - the thin film may include an interposed thin film of silicon oxide between the silicon layer and the receiving substrate;

[0031] - during each of the soakings, the substrates can be positioned above the ramp of the injection concerned and can each be oriented in such a way that their respective extension planes are substantially vertical. BRIEF DESCRIPTION OF THE FIGURES

[0032] Other features and advantages of the invention will become apparent from the detailed description of the invention which follows with reference to the accompanying figures in which:

[0033] [Fig. 1] The [Fig. 1] represents a typical bath of a Wet Bench;

[0034] [Fig.2] Fig.2 is a diagram of a process according to a first mode of realization ;

[0035] [Fig.3] The [Fig.3] illustrates steps in the process of the [Fig.2];

[0036] [Fig.4] Fig.4 illustrates the typical geometry of a substrate used in industry of the semiconductor;

[0037] [Fig. 5] Fig. 5 represents an implementation of the principle of the invention, with orientations of a substrate in a manipulation basket and treated in Wet Bench;

[0038] [Fig.6] Figure [Fig.6] illustrates steps of soaking in a bath according to the first method of realization ;

[0039] [Fig.7] Figure [Fig.7] illustrates homogeneity characterization results of surface topography of 25 substrates according to their position in a FOUP.

[0040] [Fig.8] The [Fig.8] is a diagram of a process according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0041] First embodiment

[0042] A first embodiment of the present invention is described by means of Figures 1 to 7 and the associated description below. In this first embodiment, all the substrates in a batch of substrates handled using a FOUP have the same orientation in the FOUP.

[0043] According to a particular embodiment of the invention, an FD-SOI type substrate is prepared. Such a substrate typically consists of a thin layer of monocrystalline silicon transferred onto a receiver substrate made of bulk monocrystalline silicon, with a layer of silicon oxide interposed between the silicon thin layer and the receiver substrate. In this structure, the silicon oxide electrically insulates the silicon thin layer from the receiver substrate. The latter is intended to form the active semiconductor layer of electronic devices, in which transistor channels will be formed. The so-called "fully depleted" technology requires obtaining a silicon layer sufficiently thin so that, depending on the device, the depletion zone of the transistor channels extends over the entire thickness of the layer.To obtain usable devices, the transistors must have similar characteristics across the entire substrate, which requires excellent homogeneity in the thickness of the semiconductor layer and therefore of its surface topography. We are talking about thicknesses on the order of 120 Å which must be homogeneous across the entire substrate, preferably to within approximately ±5 Å.

[0044] FD-SOI technology is still recent and the manufacturing processes it involves are under development and / or optimization. In this context, the applicant sought to reduce the rate of substrate rejection due to inhomogeneity in the thickness of the silicon thin film during the final stages, which include heat and / or oxidation treatments, as well as wet bench treatments.

[0045] Among the many parameters studied, it appeared that, for FD-SOI type substrates in preparation, the position they occupy in a FOUP is correlated with their rejection rate. As a reminder, a FOUP typically contains 25 substrates at spatially ordered positions numbered from 1 to 25. It was found that the substrates occupying the highest numbered positions in the FOUP, Typically, positions 17 to 25 are the most likely to exhibit homogeneity defects in the thickness of the thin film, these homogeneity defects being significant enough to justify the disposal of the affected substrates.

[0046] The FOUPs are used, among other things, for handling substrates before their transfer into handling baskets adapted for wet processing, known as "wet carriers" in English terminology, for batch immersion in chemical baths such as the one illustrated in [Fig. 1]. The substrates' positions 17 to 25 bring them closer to the distal ends of the injection ramps.

[0047] However, during investigations seeking to explain this phenomenon, calculations showed that the pressure in the treatment solution injection ramps increases with distance from the collector and that a simultaneous reduction in flow velocity in the ramp and an increase in flow velocity at the nozzle outlet are observed.

[0048] The inventors then hypothesized that the inhomogeneities in substrate surface topography are generated by fluidic phenomena occurring during wet bench treatments. Process improvement tests were conducted to resolve this inhomogeneity problem, based on the hypothesis that the chemical bath treatments in the wet bench were the cause. Among these tests, it appeared that adjusting the substrate orientation between two wet bench steps, rather than keeping it constant, significantly improves the thickness homogeneity of the substrates.

[0049] Measurement results such as those illustrated in the graph in [Fig. 7] confirmed the inventors' hypothesis. [Fig. 7] illustrates the maximum topography deviations (peak-to-valley measurement), indicated in angstroms on the ordinate, measured for each of 25 substrates, numbered on the abscissa according to their respective positions in a FOUP, treated in a batch by chemical baths in a wet bench. Two curves are shown. The RefProc curve represents the reference measurements, obtained for a batch that underwent conventional treatment, with the substrate orientations remaining the same for successive wet bench operations.The NewProc curve represents the measurements for a batch that has undergone a new treatment, differing from the conventional treatment of the reference curve only by a change in the orientation of the substrates between two successive sequences of operations, each including one or more WetBench operations: the orientation of the substrates has, in this particular case, been changed by 180°. The treatment in question here corresponds to the implementation of steps Or.Stpl to Final of process 100 illustrated by [Fig.2] and described below.

[0050] From the curves in [Fig. 7], it can be seen that, for a given position in a FOUP, the topographies of the substrates that underwent the new treatment are more regular and less dispersed than those that underwent the reference treatment. These measurements, representative of other tests carried out to validate the principle of the invention, confirm the effectiveness of the change in substrate orientation. This is particularly true for the last positions in the FOUP, and allows the substrates located at these positions to fall within the specification limits.

[0051] On this basis, the inventors developed process 100 for preparing a substrate intended to accommodate FD-SOI technology devices, illustrated by Figures 2 to 6. This process represents a variant of a conventional process compared to which it reduces the substrate rejection rate by about 2%, according to the inventors' experience.

[0052] In a first DonSubPrep step of process 100, a DonSub donor substrate is supplied and optionally prepared for the subsequent manufacturing steps. The DonSub donor substrate may consist of a single-crystal silicon wafer. The DonSub donor substrate may be in the form of a circular wafer of standardized dimensions, for example, 150 mm or 200 mm in diameter. However, the invention is in no way limited to these dimensions or this shape. In the context of the present example, the donor substrate undergoes thermal oxidation to form an OxLay layer of silicon oxide on its surface, as illustrated in [Fig. 3](A).

[0053] The process includes introducing at least one so-called "light" species, in particular chosen from inert gases, helium, and hydrogen, into the donor substrate DonSub during an IMP step. This introduction may correspond to an implantation, that is to say, an ion bombardment of a top flat face DonTop of the donor substrate DonSub by ions of the chosen light species or species such as hydrogen and / or helium ions.

[0054] In a manner known per se, and as illustrated by [Fig.3](A), the implanted ions form a weakening plane Frgl, which will subsequently serve to separate from the donor substrate a layer of material between the implantation surface DonTop and the weakening plane.

[0055] The nature, the dose of the implanted species and the implantation energy are chosen according to the thickness of the layer that one wishes to separate from the donor substrate DonSub and the physico-chemical properties of the latter.

[0056] In a RecSubPrep step, illustrated in [Fig. 3](B), the RecSub receiving substrate is provided to receive a thin film transferred from the donor substrate. The RecSub receiving substrate may have the same dimensions and shape as the SubDon donor substrate. For reasons of availability and cost, The RecSub receiving substrate can be a monocrystalline or polycrystalline silicon wafer.

[0057] At an assembly step Ass, illustrated by [Fig.3](C) and subsequent to the step lmp of formation of the embrittlement plane Frgl, the upper flat face DonTop of the donor substrate DonSub is assembled to an upper flat face RecTop of the recipient substrate RecSub.

[0058] Prior to the assembly step, it is possible to prepare the faces of the substrates to be assembled by a cleaning, brushing, drying, polishing, or activation step, for example by plasma.

[0059] The assembly step may correspond to the intimate contact of the donor substrate DonSub with the device substrate DevSub by molecular adhesion and / or electrostatic bonding.

[0060] At the end of this assembly step, we have a Set resulting from the assembly of the donor substrate DonSub and the receiver substrate RecSub, the DonTop face of the donor substrate DonSub adhering to the RecTop face of the receiver substrate RecSub.

[0061] At a Fract step, the Set assembly is treated in such a way as to cleave the donor substrate at the level of the embrittlement plane Frgl and thus detach a DonSubi layer which remains attached to the receiving substrate RecSub.

[0062] This detachment fracture step may thus include applying heat treatment to the entire Set assembly in a temperature range of approximately 80°C to 300°C to enable the transfer of the DonSub layer to the DevSub device substrate by fracturing the DonSub substrate at the Frgl embrittlement plane. As an alternative to, or in addition to, the heat treatment, this step may include applying a sheet or jet of gaseous or liquid fluid to the Frgl embrittlement plane.

[0063] Figure 3(D) illustrates this operation, with the separation of the donor substrate DonSub into two parts, DonSubi and DonSub2, at the embrittlement plane. The DonSubi portion forms a layer that remains attached to the recipient substrate RecSub. The resulting structure comprises a silicon layer DonMat adhering to the RecSub substrate, with a silicon oxide layer OxLay interposed between the DonMat layer and the RecSub substrate.

[0064] At this stage of preparation and in the context of the example of an FD-SOI substrate, the thin DonMat layer remaining on the RecSub substrate after the Fract detachment step can have a thickness of between 200 and 300 nm, and the OxLay layer a thickness of between 25 and 35 nm.

[0065] Finishing steps of the DonSubi layer are then necessary to improve the crystalline and surface quality of the DonMat layer and adjust its thickness to a target thickness. These finishing steps are collectively designated as Finish and correspond to the treatments from the Or.Stpl step to the Final step in the diagram of [Fig. 2]. The steps marked "WB" in the diagram are steps implemented in a wet bench, in tanks such as the InnTank tank illustrated in [Fig. 1].

[0066] As mentioned above, the finishing steps will require orienting the substrates. Substrates commonly used in the semiconductor industry are generally circular in shape but include markers to determine the crystallographic orientations of the single-crystal materials used, where applicable.

[0067] Figure 4 illustrates the main types of markers. Figures 4(A) and 4(B) respectively illustrate Sub substrates in their extension plane, these substrates being circular except for a flat (called a "fiat" in English terminology) or a notch (called a "notch" in English terminology). These markers indicate the crystallographic orientation of the substrates and can be used to orient them when placing them in the FOUP. A single substrate may have more than one flat.

[0068] For explanatory purposes, the steps are separated into three successive sequences, Seq1, Seq2, and Seq3, in that order, each being associated with a given substrate configuration in a FOUP during the wet bench soak treatment(s) implemented during the considered sequence. Three configurations, Or-Con[Fig.1], Or-Con[Fig.2], and Or-Con[Fig.3], are respectively associated with sequences Seq1, Seq2, and Seq3, as illustrated in [Fig.2], and are defined by the substrate orientations.

[0069] The first step of the process 100 following the Fract step is an Or.Stpl step for orienting the Sub substrates in a carrier basket, optionally a FOUP, thus defining the first Or-Con configuration [Fig. 1] of substrate orientation, illustrated in [Fig. 6](A). In this example, the substrates are oriented and manipulated so that, when transferred into wet carriers WC for immersion in the Wet Bench baths, their respective orientation markers are aligned along an Orl orientation aligned with the upward vertical direction Z of the bath, as illustrated by [Fig. 5](A). [Fig. 5] shows views in the extension plane of one of the substrates immersed in a bath, normal to the X direction.In general, orientations are located angularly around the X axis, parallel to the extension direction of an injection ramp and perpendicular to the extension planes of the substrates, and are defined by an angle around the measured X axis. relative to the vertical Z. Alternatively, directions other than the vertical Z direction could be retained for the Orl orientation.

[0070] The first Seq.l sequence begins with the Ot.Stpl step and is completed by Cleanl, HT1, Clean2 and 0X1 processing steps which follow, in that order, the Or.Stpl step.

[0071] The Cleanl and Clean2 steps are cleaning steps performed in a wet bench, designed to remove surface particles or particles buried near the surface, and / or metallic contaminants. The HT1 step is a heat treatment step, preferably at a temperature between 1000°C and 1200°C, preferably between 1075°C and 1175°C, under a reducing atmosphere such as a hydrogen atmosphere. This step is designed to smooth the substrate surfaces by increasing the mobility of the surface atoms. The OX1 step is a heat treatment step whose function is to stabilize the bond between the DonLay thin film and the RecSub substrate and to form an oxide layer. The OX1 step can be carried out by heat treatment at a temperature between 800°C and 1000°C under an oxidizing atmosphere, preferably around 950°C.The oxide layer will be removed subsequently, which will allow the removal of a thickness of the transferred layer that was damaged by the lmp implantation and Fract. fracturing steps.

[0072] The second sequence, Seq.2, begins following the OX1 oxidation step with a new Or.Stp2 step for orienting the substrates in the FOUP, according to the principles described for the Or.Stpl step. This time, the substrate markers are arranged in an Or2 orientation distinct from the Orl orientation, i.e., such that the Or2 orientation differs by at least 20° from the Orl orientation, as illustrated in [Fig. 5](B). This orientation can be defined by preparatory tests, in order to adapt the Or2 orientation to the Orl orientation and to the characteristics of the DonSubl layer (topography, roughness, etc.) following the Fract detachment step. This orientation is not particularly limited and will preferably be adapted to each layer to be treated.

[0073] In a particular case taken as an example, the benefits of which have been discussed in relation to the curves in [Fig. 7], the Or2 orientation is located opposite to the Orl orientation of the Or.Stpl step, that is, according to an Or2 orientation that, in this example, is substantially opposite (180°) to the Z direction, as illustrated by [Fig. 5](D). Substantially opposite means an orientation between 170° and 190° with respect to the Z direction.

[0074] A second Or-Con configuration [Fig.1] of substrate orientation is thus defined, illustrated in [Fig.6](B).

[0075] The Desoxl, HT2, Clean3 and OX2 processing steps follow, in that order, the Or.Stp2 step, and complete the second Seq.2 sequence.

[0076] The Desoxl step is a substrate deoxidation step performed by attacking the oxide formed during step 0X1, carried out in a wet bench. This can involve attacking the oxide layer with a hydrofluoric acid solution. The Clean3 step is a cleaning step. The HT2 step, like the HT1 step, is a heat treatment step under a reducing atmosphere, designed to smooth the substrate surfaces by increasing the mobility of the surface atoms. The Cleanl, Clean2, and Clean3 steps can be implemented using the RCA process. The 0X2 step is a sacrificial thermal oxidation step, which, by removing the oxide formed, will thin the DonMat thin film and potentially improve its flatness. This step can be implemented by means of a heat treatment in an oxidizing atmosphere, similarly to step 0X1.

[0077] The third Seq.3 sequence begins, following the 0X2 oxidation step, with a new Or.Stp3 substrate orientation step in the FOUP, according to the principles described for the Or.Stpl step. This time, the substrate markers follow an Or3 orientation distinct from the Orl and Or2 orientations, for example, by at least 20° relative to each of Orl and Or2, and defined in this example by an angle of approximately 135° relative to the Z direction as shown in [Fig. 5](C), thus defining a third Or-Con[Fig. 3] substrate orientation configuration, illustrated in [Fig. 6](C). The 135° angle can be retained for the advantages it provides in terms of topographic homogeneity obtained at the end of the third Seq.3 sequence for the DonMat layer when the Orl orientation is defined by the Z direction.

[0078] The Desox2 and Final processing steps follow, in that order, the Or.Stp3 step. The Desox2 step, carried out in a wet bench, is similar to the Desoxl step. The Final step is a cleaning and thinning step carried out conventionally using individual substrate processing equipment, and not using a wet bench like the other soaking steps mentioned above.

[0079] At the end of the Final step, the DonMat thin film has a thickness between 50.10 10om and 200.10 10 m, preferably between 100.10 10 m and 140.10 10 m.

[0080] To summarize, the three treatment sequences Seql, Seq2 and Seq3 follow one another, each corresponding to a substrate orientation configuration, Or-Con[Fig.1], Or-Con[Fig.2] and Or-Con[Fig.3], respectively, as illustrated by [Fig.2].

[0081] The steps mentioned above are well-known in the semiconductor field. The cleaning steps may, for example, be so-called "RCA clean" cleanings, according to industry terminology (named after the acronym for Radio Corporation of America). Such a cleaning process involves the successive immersion of the substrate in an SCI solution ("Standard Clean 1") containing ammonium hydroxide (NH4O2), hydrogen peroxide (H2O2), and deionized water, and then in an SC2 solution ("Standard Clean 1"). 2” for “standard cleaning 2”) containing hydrochloric acid (HCl), hydrogen peroxide (H2O2), and deionized water. RCA cleaning also includes immersing the substrate in rinsing solutions, typically deionized water, inserted before and / or after each immersion in the SCI, SC2 solutions.

[0082] The SCI solution is primarily intended to remove isolated particles from the surface of the substrate and particles buried near this surface, and to prevent their redeposition. The SC2 solution, on the other hand, is primarily intended to remove metallic contaminants that may have deposited on the surface of the thin film, notably by forming chlorides. A detailed description of this RCA cleaning process and its evolution can be found in the brochure "RCA Critical Cleaning Process," dated August 6, 2007, and published by Microtech System, Inc.

[0083] In the process, the treatment sequences may include wet or other steps such as heat or plasma treatments, steps for measuring and characterizing the substrates, and adjustments to the recipes and their parameters (duration, temperature, etc.) based on the results of the measurements and characterizations. In other words, the treatment steps are not limited to wet bench processes.

[0084] Second embodiment

[0085] This embodiment is illustrated by means of [Fig.8].

[0086] In the first embodiment, the substrates are all treated and oriented in the same way. However, measurements carried out on the homogeneity of the surface topography of the substrates showed that only the substrates furthest from the Coll collector, i.e. the substrates closest to the distal end of the injection ramp, are affected by a lack of homogeneity following the chemical treatments implemented in Wet Bench.

[0087] More specifically, in measurements carried out for batches of 25 substrates treated in FOUP, the homogeneity defects made the substrates non-compliant with the specifications required for locations 17 to 25, i.e. the furthest from the Coll collector, while the thickness homogeneity of the substrates placed at locations 1 to 16 remained within the tolerance limits of the specifications for the substrates.

[0088] Consequently, rather than orienting the substrates in an undifferentiated manner as in the first embodiment, it is possible to orient the substrates differently according to their respective locations in a FOUP.

[0089] Thus, in this second embodiment, the substrates are separated into two groups, a first group composed of Subi substrates located on the collector side in the FOUP and a second group consisting of Sub2 substrates located opposite the collector in the FOUP.

[0090] The only changes between the two embodiments concern the orientation configurations, and more specifically the Or-Con configuration [Fig.2] as explained with reference to [Fig.8].

[0091] In the Or-Con configuration [Fig. 1], all substrates, Subi and Sub2, are oriented in the same way, with the Orl orientation aligned with the Z direction, as illustrated by [Fig. 5](A). The Or-Con configuration [Fig. 1] of the second embodiment is therefore identical to the Or-Con configuration [Fig. 1] of the first embodiment.

[0092] In the Or-Con configuration [Fig.2], the Subi substrates located on the collector side are oriented along the Z direction, as in the Or-Con configuration [Fig.1]. In contrast, the Sub2 substrates are oriented along the Or2 orientation substantially opposite to the Z direction, as illustrated by [Fig.5](B).

[0093] An optional calibration step Cal can be implemented between the Seq1 and Seq2 sequences. This Cal step aims to characterize the surface topography of the substrates in order to determine which substrates should be considered as Sub2 substrates whose orientation should be changed to the Or2 orientation for the second Seq2 operation sequence.

[0094] The calibration step can, in particular, determine from which position in the FOUP the substrates should be considered as Sub2 substrates. In this case, the Sub2 substrates are located consecutively in the FOUP as illustrated by [Fig. 8]. For example, Substrates whose surface topography inhomogeneity exceeds a predetermined criterion, such as a predetermined value for a so-called "peak-to-valley" height measurement or for a standard deviation of the distance of the surface from a median position of that surface, can be assigned as Sub2 substrates.

[0095] In the Or-Con configuration [Fig. 3], the Subsi and Subs2 substrates are all oriented along the Or3 orientation, as illustrated by [Fig. 5](C). The Or-Con configuration [Fig. 3] of the second embodiment is therefore identical to the Or-Con configuration [Fig. 3] of the first embodiment.

[0096] By means of this sequence of steps, the set of substrates Subi and Sub2 meets the required specifications without it being necessary to change the orientation of the substrates Subi between the Seql and Seq2 sequences.

[0097] An alternative to the second embodiment is that the Sub2 substrates may have non-consecutive locations, possibly on the one hand at the first positions in the FOUP and on the other hand at the last positions in the FOUP, if the chemistry and fluid dynamics of a particular soaking require such a configuration. The decision regarding the positions of the substrates Sub2 can follow the results of Cal characterization or feedback from the practitioner. For example, substrates placed at opposite ends of a FOUP may have characteristics that prevent them from meeting required specifications, while substrates located in a central part of the FOUP do meet these specifications. The invention is not limited to a particular location of Sub2 substrates, even though preliminary results have shown that it applies particularly well to substrates located in FOUP positions far from the Coll collector.

[0098] In the examples above, the flats and notches of the substrates considered are used to ensure their orientation. The invention is not limited to this solution, and any type of marking or any other method of locating the orientation of the substrates can be used for their orientation in a FOUP or any other substrate handling device.

[0099] In this document, when it is specified that the substrates are arranged substantially perpendicular to an extension direction of an injection manifold, it is understood that this refers to flat substrates of very reduced thickness (for example, more than 50 times or more than 100 times smaller) compared to their lateral dimensions, and that the injection manifold is perpendicular to the extension plane of each of the substrates, the extension plane in which the lateral dimensions are measured. For example, in the case of a substantially circular substrate, the lateral dimension may be a diameter.

[0100] Although an FD-SOI substrate is used as an example for the above embodiments, the invention is not limited to this particular case, and any type of semiconductor, ferroelectric or piezoelectric material, or any other type of material can be considered for the donor substrate. The RecSub receiving substrate can be made of any material, for example silicon, sapphire, or glass, and can have any shape.

[0101] In addition, the DonSub substrate, the RecSub substrate, or both can be prepared so as to be provided with electrically or thermally insulating layers, electrical charge trapping layers, or layers promoting assembly between the two substrates during the Ass step below.

[0102] The invention is not limited to the embodiments described above and variations thereof may be made without departing from the scope of the invention as defined by the claims.

Claims

Demands

1. A treatment method applied to a plurality of substrates (Sub; Sub1, Sub2) held parallel to each other, the treatment comprising at least two successive sequences (Seq1, Seq2) of treatments applied to the substrates, each of the sequences comprising at least one soaking in at least one chemical bath contained in a container (InnTank) equipped with an injection ramp (InjRmp) of a treatment solution, the injection ramp comprising nozzles (No) for distributing the treatment solution, the nozzles (No) being distributed along the injection ramp (InjRmp), the substrates (Sub) each being arranged substantially perpendicular to the injection ramp (InjRmp), in which: - a first (Clean1, Clean2) of the at least two soakings is carried out with the substrates (Sub; Sub1-Orl, Sub2-Orl) oriented according to a first orientation (Orl), located angularly around an axis (X) normal to the substrates ;and - a second (Desoxl, Clean3) of the at least two soakings is carried out with at least a part (Sub; Sub2-Or2) of the substrates oriented according to a second orientation (Or2), distinct by at least 20° from the first orientation (Orl).;

2. The process according to claim 1, wherein the second (Desoxl, Clean3) of the at least two dips is carried out with all of the substrates (Sub) oriented in the second orientation (Or2).

3. The process according to claim 1, wherein the second (Desoxl, Clean3) of the at least two dips is carried out with: - first substrates (Subi) of the plurality of substrates oriented along the first orientation (Orl), and - second substrates (Sub2) of the plurality of substrates oriented along the second orientation (Or2).

4. The method according to claim 3, wherein the first substrates (Subi) are closer to an inlet (Ent) of the injection ramp (InjRmp) than the second substrates (Sub2).

5. The method according to claim 3 or 4, further comprising a substrate topography calibration (Cal) step between the first and second of at least two dippings, positions second substrates (Sub2) being determined in response to the calibration step.

6. The method according to any one of claims 1 to 5, wherein the second orientation (Or2) is substantially opposite to the first orientation (Orl).

7. A method for manufacturing a substrate comprising the steps of: - assembling (Ass) a donor substrate (DonSub) and a receiving substrate (RecSub); then - separating (Fract) a thickness of the donor substrate at a plane (Frgl) of embrittlement formed in the donor substrate (DonSub), so as to provide the receiving substrate (RecSub) with a thin layer (DonSubi) from the donor substrate (DonSub); then - applying to the receiving substrate (RecSub) provided with the thin layer (DonSubi) the treatment process according to any one of claims 1 to 6.

8. The process according to claim 7, wherein each of the sequences (Seql, Seq2) comprises a plurality of dips (Cleanl, Clean2, Desoxl, Clean3) in a plurality of chemical baths each contained in a container (InnTank) equipped with an injection ramp (InjRmp) of a treatment solution, the ramps comprising nozzles (No) for distributing the treatment solutions, the substrates (Sub; Subi, Sub2) being, during each of the dips, each arranged substantially perpendicular to the injection ramp of the bath in which they are dipped, process wherein: - the first dips (Cleanl, Clean2) of the first sequence (Seql) are carried out with the substrates (Sub; Subi, Sub2) oriented according to the first orientation (Orl); and - the second soakings (Desoxl, Clean3) of the second sequence (Seq2) following the first sequence (Seql) are carried out with at least a part (Sub ; Sub2) of the substrates oriented according to the second orientation (Or2).

9. The process according to claim 8, wherein: - the first dips of the first sequence (Seql) comprise a cleaning step (Cleanl), the first sequence further comprising a first oxidation step (0X1), and - the second dips of the second sequence comprise a first deoxidation step (Desoxl).

10. The process according to claim 9, the treatment process comprising a third sequence (Seq3) of treatments applied to the substrates, the second sequence (Seq2) and comprising at least one third soaking in at least one chemical bath contained in a container (InnTank) equipped with an injection manifold (InjRmp) of a treatment solution, the injection manifold comprising nozzles (No) for distributing the treatment solution, the nozzles (No) being distributed along the injection manifold (InjRmp), the substrates (Sub) each being arranged substantially perpendicular to the injection manifold (InjRmp), process wherein: - the second sequence (Seq2) comprises a second oxidation step (0X2); - the at least one soaking of the third sequence (Seq3) comprises a second deoxidation step (Desox2); and - the third sequence is carried out with the substrates (Sub;Subi, Sub2) oriented according to a third orientation (Or3) substantially different from the first orientation (Orl) and the second orientation (Or2), the third orientation (Or3) being located angularly around the axis (X) normal to the substrates.;

11. The process according to any one of claims 7 to 10, wherein the thin film (DonMat) has a thickness between 50.10 10om and 200.10 10 m, preferably between 100.10 10 m and 140.10 10 m at the end of the treatment process.

12. The method according to any one of claims 7 to 11, wherein the thin film (DonSubi) comprises a layer (DonMat) of silicon.

13. The method according to claim 12, wherein the thin film (DonSubi) comprises a thin film (OxLay) of silicon oxide interposed between the silicon layer (DonMat) and the receiving substrate (RecSub).

14. The method according to any one of the preceding claims, wherein, during each of the dips, the substrates are located above the relevant injection ramp and are each oriented in such a way that their respective extension planes are substantially vertical.

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