Plasma immersion ion implantation device using liquid or solid precursors without carrier gas

Abstract

The invention relates to a system (SYS1; SYS2) for implanting an ion species by plasma immersion, the system employing a vapour of a precursor of the ion species originating from a vessel containing the precursor in liquid or solid form, the device comprising: - an implantation chamber (IC) configured to receive the semiconductor substrate (SUB); - a plasma source (PS) configured to form a plasma from the precursor vapour and to operate at precursor vapour mass flow rates of less than 20 SCCM; and - a gas line (GL) connecting the vessel (VES) to the plasma source (PS) so as to supply the latter with the precursor vapour, the gas line (GL) being provided with a device (NV; FC) for adjusting the flow rate of the precursor vapour; the precursor having a saturated vapour pressure greater than 667 Pa for a temperature of below 100°C.

Description

Plasma immersion ion implantation equipment using liquid or solid precursors without carrier gas TECHNICAL FIELD OF THE INVENTION

[0001] The field of the invention is that of ion implantation equipment in plasma immersion mode for low pressure processes. TECHNOLOGICAL BACKGROUND

[0002] Plasma immersion ion implantation (which will subsequently be referred to by its English acronym PIII for Plasma Immersion Ion Implantation) allows the implantation of different chemical species by placing a target substrate in a plasma containing the ions of the species to be implanted and by negatively polarizing it in order to accelerate these ions towards its surface.

[0003] PIII implantation allows higher processing rates than ion beam implantation and enables conformal implantation on surfaces with three-dimensional structures, therefore it is well suited to the processing of modern semiconductor components.

[0004] The ion sources used in these machines must create a uniform plasma within a volume large enough to contain the target substrate and encompass the ion sheath that forms due to the substrate's polarization. Thus, RF (inductively coupled plasma, or ICP, or helicon plasma) or microwave sources, such as cyclotron resonance (ECR, or electron cyclotron resonance), can be used. These sources generate plasmas from gases containing the ions to be implanted and are widely used for doping silicon semiconductor components. For example, BF3 or B2H6 gases are used to implant boron, and AsH3 and PH3 gases are used to implant arsenic and phosphorus, respectively.

[0005] However, modern semiconductor components use materials such as SiC, GaN, and SiGe, and new doping species must be used, such as aluminum for SiC, magnesium for GaN, or gallium for SiGe. A major difficulty is the impossibility of finding gases containing these species, which prevents the use of PIII.

[0006] Thus, sputtering ion sources, of the "sputtering" or "cathodic arc plasma" type (also called "hollow cathode"), have been proposed, capable of implanting species from solid precursors. A key reference is André Anders' "Handbook of Plasma Immersion Ion Implantation and Deposition," published by Wiley-VCH in 2000. While these sources are effective in generating numerous types of ions from the atoms of a so-called cathode target, and while their use in PIII has been validated for mechanical surface treatment applications, this method generates a level of particle size incompatible with use in microelectronics, for example, for ion implantation.

[0007] In conventional implantation, ion sources using vapors from solid precursors in powder or granular form have been employed since the 1970s when the use of gases is not feasible. One example is the use of aluminum chloride evaporated under vacuum near the ion source to implant aluminum. However, this method is difficult to implement in PIII due to the risk of significant deposition through recondensation on the plasma source, the walls of the treatment chamber, and, even worse, the target substrate.

[0008] In another field, to form material layers, atomic layer deposition (ALD) or metal-organic chemical vapor deposition (MOCVD) are used. These techniques are increasingly employed for depositing thin films onto the substrates of modern semiconductor components. New liquid precursors covering numerous chemical species of elements (including many metallic species) have been developed. These liquid precursors possess sufficiently high vapor pressures at temperatures below 100°C to be distributed in processing chambers.

[0009] To achieve the required flow rates (several tens, or even hundreds, of SCCMs), these precursors are used in bubblers where a carrier gas, chosen to be neutral for the process, is injected. The combination of heating the bubbler and bubbling with the carrier gas allows vapor from the liquid precursor to be transported at a sufficient flow rate to carry out the deposition process.

[0010] While this method, despite its drawbacks, works for deposition processes, it cannot be used in PIII implantation. This is because the species contained in the carrier gas will also be ionized in the plasma source and thus implanted into the target substrate, which is unacceptable for most of the intended applications. Furthermore, the implantation ratio between ions from the precursor and those from the carrier gas is not controlled. Eliminating the carrier gas prevents the generation of the vapor flow rates necessary for the proper operation of the plasma sources typically used in PIII implantation machines.

[0011] The use of liquid precursors such as TMA (trimethylaluminum) has been reported for implanting aluminum using ion beam implantation (cited as an example in patent document US2009 / 0190908). In this case, the use of a carrier gas is not problematic because the scanning magnet filters out ions other than those to be implanted, thus allowing only the chosen ions—aluminum ions in the case of TMA—to be implanted. Furthermore, the small volume of ion sources in ion beam implanters does not require high gas flow rates, and the use of carrier gases is not mandatory.

[0012] Liquid or solid precursors with saturated vapor pressures of 1 torr to 2 torr in a temperature range of 20°C to 50°C are known for their use in ion implantation or plasma immersion implantation (see US patent document 8367531 B1). However, these saturated vapor pressures require the use of a carrier gas to achieve the flow rates of several tens of SCCM (Standard Cubic Centimeters per Minute, a mass flow rate unit commonly used in the field) necessary for the operation of the plasma sources used in conventional PIII devices.

[0013] Patent document EP 3 005 396 B1 describes an ion implantation system employing a subatmospheric pressure storage device for a composition containing aluminum for aluminum doping. This composition comprises at least one halogen, a one-carbon alkyl group, and aluminum. However, halogens often form troublesome contaminants when ion implantation is performed in semiconductor materials. Furthermore, this document mentions a check valve, which introduces a pressure drop in the vapor flow of the composition and thus limits the system to certain compounds with a vapor pressure high enough to pass from the storage device to the implantation chamber.

[0014] We therefore see that there is no technically satisfactory solution for implanting species such as aluminium, magnesium or gallium into substrates intended for use in the manufacture of semiconductor devices.

[0015] An object of the invention is a plasma immersion ion implantation system capable of using liquid or solid precursors without requiring the use of a carrier gas, and in particular for the implantation of species not available in the form of a gaseous precursor.

[0016] With a view to achieving these objectives, a first aspect of the invention is a system for implanting an ion species into a semiconductor substrate by plasma immersion, the system being intended to use a vapor of a precursor of the ion species from a container containing the precursor in liquid or solid form, the system comprising: an implantation chamber configured to accommodate the semiconductor substrate; a plasma source fluidically connected to the implantation chamber, configured to form a plasma from the vapor of the precursor and to work at mass flow rates of the precursor vapor less than 20 SCCM, preferably less than 10 SCCM, even more preferably less than 5 SCCM;and a gas line configured to fluidly connect the vessel to the plasma source so as to supply the latter with precursor vapor, the gas line being equipped with a precursor vapor flow adjustment device configured to be adjustable to obtain a flow rate between 1 SCCM and 20 SCCM; the vessel connected to the gas line, the precursor having a saturated vapor pressure greater than 667 Pa for a temperature below 100°C; and;

[0017] a temperature control system for the container, the container being equipped with a heating system intended to heat the container itself.

[0018] A first advantage of this device is its ability to implant by plasma immersion ion species not found in the form of gaseous precursors, and which therefore allows the use of a wide range of precursors including liquid precursors.

[0019] A second advantage of the device is that it does not require a carrier gas to transport vapor from the precursor to the plasma source where it will be converted into plasma. Therefore, the implantation is not disrupted or contaminated by carrier gas.

[0020] A third advantage is that, among the wide range of possible precursors, there is a probability of finding one that satisfies a particular application, and in particular one that will be relatively neutral in terms of contamination of the substrate to be implanted.

[0021] According to additional, non-limiting features of the first aspect of the invention, considered individually or in any technically feasible combination: the gas line may have a conductance greater than 2.5 × 10 -3 l / s, preferably greater than 2.5×10 -2l / s; the gas line may be equipped with a heating system; the gas line may be equipped with at least one first valve, the flow adjustment device, and a second valve distributed in that order between an inlet and an outlet of the gas line, the outlet opening into a volume defined by the plasma source; the plasma source may be an inductively coupled radiofrequency plasma source or a cyclotron resonance microwave plasma source; the plasma source may comprise a first chamber into which the gas line opens, a second chamber opening into the implantation chamber, and a pressure drop device fluidly connecting the first chamber to the second chamber; at least one magnetic coil surrounds the plasma source;The implantation system may further include an analysis system configured to analyze the chemical composition of a gas located in the gas line or in the implantation chamber, the system being configured to start an ion implantation operation only if a concentration of a given chemical species in the gas, measured by means of the analysis system, is below a predetermined threshold; the liquid or solid precursor may be chosen from TMA, TMGa, TEGa, TEP, DMAs, DEAs, TMSb, TMBi, DMTe, DMSe, DMDSe, TMIn, and SbF5; the liquid or solid precursor may be DMAH; the implantation system may be devoid of a carrier gas injection system in the vessel containing the precursor; in operation, there may be a two-way opposing flow fluidic connection between an internal volume of the vessel and the plasma source passing through the gas line.

[0022] A second aspect of the invention relates to a method for ion implantation in a semiconductor substrate, implementing the system according to the first aspect of the invention, comprising the steps of: pumping an atmosphere contained in the implantation chamber, the system being configured to also pump an atmosphere contained in the container; adjusting the flow control device to obtain a flow rate between 1 SCCM and 20 SCCM; adjusting the pumping speed of the atmosphere contained in the implantation chamber to obtain a pressure between 10 -3 Pa and 100 Pa in the implantation chamber; and turn on the plasma.

[0023] According to additional non-limiting features of the first aspect of the invention, considered individually or in any technically feasible combination: the method comprising a step of starting up the heating system with which the container is equipped so as to achieve a desired saturated vapor pressure in the container; and the method may further comprise a step of filling the container with a gas via the gas line.

[0024] The system and the process inherit the advantages of the device they employ. BRIEF DESCRIPTION OF THE FIGURES

[0025] 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:

[0026] Lare represents the assembly of a plasma immersion ion implantation device with a source of ionic species to be implanted;

[0027] Lare represents a first example of a plasma immersion ion implantation system;

[0028] Laillustre a second example of a plasma immersion ion implantation system;

[0029] Laillustre a process of first use of the system illustrated by the ;

[0030] Laillustre a method of using the system illustrated by the ; and

[0031] Laillustre another method of using the system illustrated by the. DETAILED DESCRIPTION OF THE INVENTION

[0032] First method of implementation

[0033] A first method of implementation is illustrated by Figures 1 and 2.

[0034] Figure 1 illustrates the two elements which, when assembled as shown in Figure 2, form the SYS1 system for implanting an ionic species into a SUB substrate by plasma immersion. The first element is a DEV ion implantation device. The second element is a PSce source of an LP precursor of the ionic species to be implanted, this source being able to be connected to the DEV device. The DEV device comprises an IC implantation chamber, a PS plasma source, and a GL gas line connecting the PS plasma source to the PSce source.

[0035] The PSce source here includes a connection system Con, which may consist of a set of pipes, valves, and fittings, preferably designed to minimize the pressure drop generated by this assembly. At a minimum, this assembly includes a shut-off valve, intended to completely isolate the outlet used to connect a VES container holding an LP precursor of ions to be implanted to the DEV device. The DEV device is considered a fixed, permanently installed device. The PSce source is a mobile component, designed to contain a consumable, the LP precursor, and must therefore be replaced as this consumable is consumed. The PSce source is typically installed in a gas box GB located near the DEV device. The gas line GL may connect the DEV device to the PSce source and may be located partly inside the gas box GB and partly outside it.The GL gas line can be located entirely outside the GB gas box.

[0036] The operating principle of the SYS1 system is as follows. The gas line LG has a sufficiently high conductance (or, in other words, the pressure losses associated with the gas line are sufficiently low) so that the pressure inside the vessel can reach the saturated vapor pressure of the precursor while allowing sufficient vapor flow to the plasma source for it to effectively generate a plasma from this precursor vapor. Insufficient conductance in the gas line would prevent a sufficient gas flow to supply the plasma source. This effect is even more pronounced when the saturated vapor pressure of the precursor is low.

[0037] The vessel can be heated to a temperature T1 to increase the saturated vapor pressure and maintain a pressure P within the vessel, sufficient to achieve the desired flow rate for plasma generation and ion implantation of the ions formed from the vapor by the plasma source. To this end, the gas line GL and its constituent components (pipes, valves, flow control elements, etc.) must have maximized conductance to minimize pressure losses and achieve the required flow rate for the plasma source, even for precursors with low saturated vapor pressures, typically a few torrs.

[0038] The gas line is connected to a plasma source requiring only a low flow rate, typically on the order of 1 to 10 SCCM, such as the plasma source described in patent document WO 2012 / 168575 A2. Other plasma sources capable of operating at low flow rates, such as certain ECR sources, could be used.

[0039] The IC implantation chamber is equipped with a substrate holder (SC) designed to support the substrate (SUB). The substrate (SUB) can be a semiconductor substrate such as a silicon wafer (Si), silicon carbide (SiC), gallium nitride (GaN), or silicon-germanium alloy (SiGe). The substrate holder can be movable, for example, rotatable, and is preferably electrically connected to a high-voltage (HV) source to negatively bias it, so as to attract positive ions from a plasma generated by the plasma source (PS). The negative bias and / or the plasma are generally pulsed to avoid electrical arcing related to cladding extension. In some cases, a high-voltage, high-frequency (tens to hundreds of kHz) sinusoidal alternating bias may be used.

[0040] The IC implantation chamber is connected to a VAC vacuum pump configured to evacuate the gases present in the chamber and create a low-pressure environment.

[0041] The PS plasma source defines an open volume on the IC implantation chamber, a volume in which the plasma source is configured to generate a plasma from a source gas.

[0042] In this embodiment, illustrated in Figure 1, the volume consists of a main chamber PR and an auxiliary chamber AUX separated by a perforated partition PP, but other configurations are possible. The perforated partition PP acts as a pressure drop device interposed between the two chambers of the plasma source. The auxiliary chamber AUX opens into the installation chamber IC and is interposed between the main chamber PR and the installation chamber IC. The gas line opens into the main chamber PR.

[0043] The plasma source can be based on various known principles of gas excitation to form a plasma. More specifically, the plasma source can be, for example, an inductively coupled radio frequency plasma source or a cyclotron resonance microwave plasma source. The PS plasma source illustrated in the diagram can include a first radio frequency antenna ANT1 surrounding the main chamber, configured to excite the gas brought to the main chamber by the gas line GL and thus generate a plasma. A first confinement coil CC1 can optionally surround the radio frequency antenna ANT1.

[0044] Optionally, a second ANT2 radio frequency antenna can surround the auxiliary chamber, configured to excite the gas supplied to the main chamber by the GL gas line and thus generate a plasma. A second CC2 confinement coil can optionally surround the ANT2 radio frequency antenna.

[0045] Regarding the other characteristics of the DEV device, reference can be made to the general knowledge of those skilled in the art, and in particular to the publication of international patent application WO 2012 / 168575 A2. Specifically, such a plasma source is configured to operate at precursor vapor mass flow rates below 20 SCCM, preferably below 10 SCCM, and even more preferably below 5 SCCM. The plasma source must be designed so that this low flow rate is sufficient to achieve the pressures necessary for plasma ignition and maintenance; that is, a pressure high enough that the electron trajectory imposed by the source's excitation electromagnetic field exceeds the mean free path of collision between these electrons and the vapor molecules in the source.This condition must allow the ignition and maintenance of a plasma of sufficient density to then diffuse into the treatment chamber to the substrate.

[0046] The gas line GL is configured to connect the main chamber PR of the plasma source to the container VES containing an ion precursor LP to be implanted, in liquid or solid form. The precursor has a saturated vapor pressure greater than 667 Pa, or 5 Torr, at temperatures below 100°C, which allows access to certain precursors with vapor pressures lower than 0.1 Torr at 25°C. The gas line is equipped at its inlet En with a flange Fl for connection to the container VES. The connection can be made by attaching the connection system Con of the source PSce to the flange Fl, as illustrated. The type of flange used is not particularly restricted, as long as a leak-proof connection is ensured between the inside of the gas line and the inside of the container.

[0047] As explained above, the GL gas line must exhibit high conductance, preferably greater than 2.5×10 -3 l / s (to allow a flow rate of 1 SCCM under 5 torr), even more preferably greater than 2.5×10 -2 l / s (to allow a flow rate of 10 SCCM under 5 torr). It is also this high conductance, combined with heating of the vessel and the line, that allows the use of precursors with saturated vapor pressures below 0.1 Torr at 25°C, but in all cases with a value, at the vessel heating temperature, greater than the pressure drop in the line calculated at the desired steam flow rate (for example, 5 torr at 100°C for 100 SCCM for a line with a pressure drop of 2.5 × 10 -2l / s). Thus, preferably, the gas line GL and / or the vessel VES are free of any element that could reduce the conductance between an internal volume Vol of the vessel VES and the plasma source PS. Such an element could be a check valve. In this way, during operation, there is a two-way fluidic connection with opposing flows between an internal volume Vol of the vessel and the plasma source PS via the gas line GL. By two-way fluidic connection with opposing flows, it is understood that the gases are free to move in both directions between the internal volume Vol of the vessel VES and the plasma source PS, even though a pressure differential between these two areas naturally results in a directional flow.

[0048] The gas line GL is preferably equipped with a first valve V1 and a second valve V3 located respectively on the inlet side En and the outlet side Ex of the gas line. Between these two valves, the gas line GL is preferably equipped with a gas flow adjustment device.

[0049] The first valve, V1, isolates the GL gas line from the VES container when they are connected. The second valve, V3, is optional and allows, if desired, the installation chamber to be isolated from the gas line, thus preventing the entry of air or nitrogen during maintenance operations requiring nitrogen ventilation or opening of the installation chamber.

[0050] The gas flow adjustment device in the DEV device illustrated in Figure 1 consists of a needle valve (NV), which, during device operation, regulates the flow of vapor from the precursor source (PSce) to the plasma source. This flow rate depends on the type of precursor used, the temperature applied to the vessel, the opening of the needle valve, and the pressure in the implantation chamber (IC). The pressure in the implantation chamber (IC) must be significantly lower than the pressure in the vessel (VES). In practice, this condition is met, as typical pressures in the implantation chamber during operation are on the order of 10 -2 Pa to 10 Pa, for a pressure of around 1000 Pa in the container.

[0051] Depending on the intended use, and in particular depending on the type of ion precursor used for ion implantation, the LG gas line can be equipped with an H2 heating system, the usefulness of which will be discussed below.

[0052] The PSce source of an LP precursor of the ionic species to be implanted essentially comprises a VES container that can be hermetically sealed. The PSce source may also include the elements necessary for introducing the precursor into the container and the conventional elements required for a hermetic connection of the container to the gas line (fittings, flange, valves, etc.).

[0053] The VES container is designed to hold an ion precursor to be implanted in liquid or solid form. Preferably, this is a precursor for which no gaseous precursor currently exists, thus forcing the use of an alternative solution.

[0054] The principle is that the precursor has a sufficiently high saturated vapor pressure at sufficiently low temperatures so that by simple heating, or even without heating depending on the case, a vapor pressure high enough to supply the PS plasma source via the LG gas line can be obtained.

[0055] Thus, in the system illustrated in Figure 1, the VES container contains a precursor LP in liquid form and is equipped with a heating system H1 designed to heat the container itself in order to vaporize the precursor when necessary, generating a vapor that will be delivered to the plasma source PS via the gas line GL. Of course, the precursor could also be in solid form within the container.

[0056] The usable precursors must meet certain criteria. The system operates on a low-pressure basis, but a certain pressure level must still be maintained to ensure compatibility with the system components, particularly the plasma source, the vapor flow control equipment (flow controllers operating at low pressure require pressure variations of a few torr, typically around 5 torr to 10 torr between their upstream and downstream ends), and the materials used for the gas line, which must exhibit a low outgassing rate relative to the expected vapor flow rate. Considering these criteria, it is possible to determine that usable precursors are those with saturated vapor pressures greater than 5 torr, preferably 10 torr, at temperatures between 60°C and 100°C.Where possible, given the intended applications, precursors with saturated vapor pressures greater than 5 Torr, preferably 10 Torr, can be chosen for temperatures of 25°C, thus eliminating the need for heating systems H1 and H2.

[0057] Among the precursors known to meet at least one of the above criteria are (conventional abbreviation of the chemical formula name followed in parentheses by the precursor's chemical formula): TMA (Al(CH3)3), DMAH (AlH(CH3)2), TMGa (Ga(CH3)3), TEGa (Ga(C2H5)3), TEP ((C2H5)3PO4), DMAs (C2H7AsO4), DEAs (C4H 11 AsO2), TMSb (Sb(CH3)3), TMBi (Bi(CH3)3), DMTe (Te(CH3)2), DMSe (Se(CH3)2), DMDSe (Se2(CH3)2), TMIn (In(CH3)3), or SbF5.

[0058] The H1 and H2 heating systems of the VES vessel and the GL gas line and its associated elements (valves, needle valve) can for example consist of flexible heating resistances wrapped around the element(s) concerned.

[0059] The heating system H1 has the function of bringing the inside of the VES container to a temperature T1 sufficient for a saturated vapor pressure usable by the SYS1 system to be obtained.

[0060] The gas line and its associated components must be maintained at a temperature T2 sufficient to prevent any risk of condensation of precursor vapor on the line walls and its associated components (valves, flow control devices). Temperature T2 must be greater than or equal to temperature T1. This temperature T2 is obtained and then maintained by means of the H2 heating system.

[0061] Second method of implementation

[0062] The SYS2 system of a second mode of implementation of the invention is illustrated by the, the and the illustrate methods of implementation of the SYS2 system.

[0063] With the exception of the NV needle valve, the SYS2 system incorporates the entire SYS1 system from the first implementation mode and functions in the same way, so one can refer to the description of the SYS1 system, including for the aspect relating to the GB gas box, not illustrated by the.

[0064] A key difference between the SYS2 and SYS1 systems is that the NV needle valve is replaced by a FC flow controller. This flow controller can be, for example, a mass flow controller (MFC) or a pressure flow controller (PFC). In all cases, the FC flow controller is a device that allows adjustment of the flow rate or pressure in the GL gas line, regardless of the LP precursor temperature (T1) in the VES vessel. Naturally, the operating conditions, and in particular the T1 temperature inside the VES vessel, must be compatible with the pressure drop caused by the pressure loss in the gas line due to the presence of the FC flow controller.In other words, the acceptable pressure drop must fall within the flow controller's specifications. Under these conditions, the FC flow controller allows control of the flow rate or vapor pressure in the plasma source, independent of the exact temperature T1 of the precursor in the vessel. The FC flow controller can be a low differential pressure mass flow meter; this type of flow meter can operate with pressure differences between 0.5 and 10 mbar.

[0065] In addition to the replacement of the NV valve, the SYS2 system includes optional elements listed and described below, not present in the SYS1 system, and which can be included in the SYS2 system independently of each other.

[0066] The GL gas line includes a V2 valve located downstream of the gas flow adjustment device and upstream of the V3 valve. This V2 valve allows the GL gas line to be isolated between the PSce source and the IC implant chamber, and provides a safety function in case of failure of the V3 valve.

[0067] A pumping and ventilation system is designed to perform pumping and ventilation cycles on the gas line. One advantage of this system is that it removes gases and contaminants present in the gas line before connecting the VES container. This avoids the risk of precursor vapor contamination during ion implantation, as well as fire hazards, given that some precursors are pyrophoric (such as TMA). Ventilation is preferably performed using an inert gas such as nitrogen.

[0068] The pumping and ventilation system may include (i) an N2 line line(i) a supply of neutral gas N2 to the gas line GL, a valve V4 controlling the opening and closing of this line, and (ii) a pumping line PMP line connecting the GL gas line to a PMP pump, a V5 valve controls the opening and closing of this line.

[0069] A pressure sensor P Sens .GL can be arranged to measure the pressure at the inlet En of the gas line, this pressure being considered representative of the pressure inside the VES container when it is open on the gas line (i.e. when the container opening system on the gas line, not shown in the figures), is open.

[0070] A pressure sensor P Sens.IC can be arranged to measure the pressure in the implantation chamber.

[0071] A Gas.Anal gas analysis system can be installed on the GL gas line, the PS plasma source, or the IC implantation chamber. In the example shown, it is installed on the IC implantation chamber. This system can be a residual gas analyzer (RGA), which may include a mass spectrometer configured to analyze the gas present in, in this case, the implantation chamber.

[0072] A CONT control system can be configured to control all or part of the GL gas line valves and the DEV device, including the H1 heater, as well as the Gas.Anal gas analysis system and the P pressure sensor. Sens so as to be able to implement the processes described below in a centralized and automated manner. Alternatively, the processes can be implemented in whole or in part manually.

[0073] Combined with the CONT control system, the H1 heater constitutes a system for controlling the temperature of the precursor and, ultimately, the pressure at the inlet of the gas line, which makes it possible to control the gas flow up to the plasma source and / or to achieve operational parameters compatible with the gas flow control elements along the GL line.

[0074] This is a diagram of a 400 first use process of the SYS2 system. This process has, in part, the function of removing an inert gas filling the VES container in addition to the LP precursor during its transport to its place of use.

[0075] Indeed, due to the highly reactive nature of most of the precursors used, suppliers of these products fill the free volume of the containers with inert gases such as nitrogen or helium. After connecting a new container to the gas line, it will therefore be necessary to vent any inert gas it may contain before starting an ion implantation procedure.

[0076] At the start of the process, all the system valves are closed.

[0077] At step 10, before opening valve V1, several pumping and venting cycles are performed using the pumping and venting system, ending with a pumping cycle. Valves V4 and V5 are opened alternately in order to introduce an inert gas into the GL line via the N2 line in the first stage of the cycle. line when valve V4 is open, then, in a second step of the cycle, pump the neutral gas through the PMP line linewhen valve V5 is open. Valve V2 is preferably open during this step, and the flow controller can be controlled to allow good fluid communication (i.e., low pressure loss) between its upstream and downstream sides.

[0078] At step 20 following step 10, a leak test is performed between the IC implantation chamber and the V1 valve.

[0079] At step 30 following step 20, in response to confirmation of the absence of leakage, valves V1, V2, and V3, the flow control device, and, if applicable, a valve on the source PSce allowing communication from inside the VES container to the GL gas line, are opened. The vacuum pump VAC is running and pumping the atmosphere from the implantation chamber IC so as to also pump the atmosphere from the VES container, along with precursor vapor LP and possibly an inert gas. The pressure P in the container must reach the saturated vapor pressure of the precursor at its temperature. This will be ambient temperature if the heating system H1 is not operating. In the absence of an inert gas, either because it has been pumped elsewhere or because

[0080] At a step 40 following step 30, if necessary, the heating systems H1 and H2 are activated to reach the temperatures T1 and T2 of the VES container and the GL gas line, respectively, as desired by the operator, depending on the type of ion to be implanted, and therefore the precursor to be evaporated. Temperatures T1 and T2 respectively allow (i) obtaining the desired saturated vapor pressure and ensuring a sufficient vapor flow rate for, for example, an ion implantation process, and (ii) preventing redeposition of the generated vapor on the walls of the gas line.

[0081] At step 50 following step 40, a vacuum is created by pumping into the implantation chamber using the vacuum pump VAC. The valves and flow control device are adjusted to ensure a gas flow consisting of residual container fill gas VES and precursor vapor. The gas flow is maintained until the pressure stabilizes, for example, as measured at the inlet of the gas line GL by the pressure sensor P. Sens .

[0082] At this step 50, it is possible to verify the total evacuation of the filling gas from the container using the Gas.Anal gas analysis system, and to maintain the gas flow until the absence of the filling gas is confirmed, or at least until its concentration falls below a predetermined limit.

[0083] At a step 60 following step 50, when the absence of the filling gas has been confirmed, the flow adjustment device is set to obtain a desired flow rate in the plasma source, between 1 SCCM and 20 SCCM.

[0084] At step 70 following step 60, the pumping speed of the implantation chamber is adjusted to obtain a desired pressure in the ionization chamber, for example between 10 -3 between 100 Pa and 100 Pa, preferably between 10 -2 Pa to 10 Pa.

[0085] At a step 80 following step 70, the plasma is turned on by means of the PS plasma source, and the pore-substrate is polarized by means of the HV high voltage source.

[0086] At step 90, following step 80, when the desired implantation dose is reached, valves V3 and V1 are successively closed. This step concludes the initial use procedure of the SYS2 system.

[0087] This is a diagram of a process 500 for using the SYS2 system that can be used repeatedly after process 400 has been implemented once following the connection of a new PSce source to the DEV device.

[0088] During process 500, steps 40, 30, 60, 70, 80, and 90, defined individually within the description of process 400, are implemented in that order. In this case, step 40 is not intended to remove an inert gas, which has already been removed during process 400, but rather to prepare the system for implementation, in terms of degassing the equipment.

[0089] Figure 1 is a diagram of a process 600 for using the SYS2 system, preparing the system for a change of the VES container. To this end, it may be preferable to introduce a gas into the container before closing it and disconnecting it from the rest of the system. This filling can be accomplished in step 100, during which valve V2 is closed, valve V1 is opened, and a gas, preferably an inert gas such as nitrogen, is introduced at a desired pressure into the GL gas line by means of the N2 line. line , so as to introduce it into the container through it.

[0090] The implementation methods described in this document can be combined. In particular, the flow controller of the YS2 system could be replaced by the NV needle valve. The various components present in the SYS2 system that are absent from the SYS1 system can be included in the SYS2 system independently of each other.

[0091] In this document, the figures are not necessarily to scale. Some features and components may be shown exaggerated relative to other components or in a somewhat schematic form, and some details of conventional elements may not be shown for the sake of clarity and conciseness.

[0092] Of course the invention is not limited to the implementation methods described and alternative embodiments can be made without departing from the scope of the invention as defined by the claims.

Claims

System (SYS1; SYS2) for implanting an ion species into a semiconductor substrate by plasma immersion, the system being designed to use vapor of a precursor of the ion species from a vessel (VES) containing the precursor in liquid or solid form, the system comprising: - an implantation chamber (IC) configured to receive the semiconductor substrate (SUB); - a plasma source (PS) fluidically connected to the implantation chamber (IC), configured to form a plasma from the precursor vapor and to operate at precursor vapor mass flow rates of less than 20 SCCM, preferably less than 10 SCCM, even more preferably less than 5 SCCM; and - a gas line (GL) configured to fluidly connect the vessel (VES) to the plasma source (PS) so as to supply the latter with the precursor vapor, the gas line (GL) being equipped with a device (NV;FC) precursor steam flow adjustment configured to be adjustable to obtain a flow rate between 1 SCCM and 20 SCCM; - the vessel (VES) connected to the gas line (GL), the precursor having a saturated vapor pressure greater than 667 Pa for a temperature less than 100°C; and - a temperature control system (H1, CONT) for the vessel (VES), the vessel (VES) being equipped with a heating system (H1) intended to heat the vessel (VES) itself. The system according to claim 1, wherein the gas line has a conductance greater than 2.5×10 -3 l / s, preferably greater than 2.5×10 -2 l / s. The system according to claim 1 or 2, wherein the gas line is provided with a heating system (H2). The System according to any one of claims 1 to 3, wherein the gas line (GL) is provided with at least a first valve (V1), the flow adjustment device (NV; FC), and a second valve (V3) distributed in that order between an inlet (En) and an outlet (Ex) of the gas line, the outlet opening into a volume (PR, AUX) defined by the plasma source. The System according to any one of claims 1 to 4, wherein the plasma source is an inductively coupled radiofrequency plasma source or a cyclotron resonance microwave plasma source. The System according to any one of claims 1 to 5, wherein the plasma source comprises a first chamber (PR) into which the gas line (GL) opens, a second chamber (AUX) opening onto the implantation chamber (TC), and a pressure loss device (PP) fluidly connecting the first chamber (PR) to the second chamber (AUX). The System according to any one of claims 1 to 6, wherein at least one magnetic coil (CC1, CC2) surrounds the plasma source (PS). The System according to any one of claims 1 to 7, further comprising an analysis system (Gas.Anal) configured to analyze a chemical composition of a gas located in the gas line or in the implantation chamber, the system being configured to start an ion implantation operation only if a concentration of a given chemical species in the gas, measured by means of the analysis system, is below a predetermined threshold. The System according to any one of claims 1 to 8, wherein the liquid or solid precursor is selected from TMA, TMGa, TEGa, TEP, DMAs, DEAs, TMSb, TMBi, DMTe, DMSe, DMDSe, TMIn, and SbF5. The System according to any one of claims 1 to 8, wherein the liquid or solid precursor is DMAH. The system according to any one of claims 1 to 10, lacking a carrier gas injection system in the container (VES) containing the precursor (LP). The system according to any one of claims 1 to 11, wherein, in operation, there is a two-way opposite flow fluidic connection between an internal volume (Vol) of the container and the plasma source (PS) passing through the gas line (GL). A method for ion implantation in a semiconductor substrate, implementing the system according to any one of claims 1 to 12, comprising the steps of: - pumping (30) an atmosphere contained in the implantation chamber (IC), the system being configured to also pump an atmosphere contained in the vessel (VES); - adjusting (60) the flow adjustment device to obtain a flow rate between 1 SCCM and 20 SCCM; - adjusting (70) a pumping speed of the atmosphere contained in the implantation chamber (IC) to obtain a pressure in the chamber between 10 -3 Pa and 100 Pa in the implantation chamber; and- turn on (80) the plasma. The process according to claim 13 and claim 3, the process comprising a step (40) of starting up the heating system (H1) with which the container (VES) is equipped so as to achieve a desired saturated vapor pressure in the container (VES). Ion implantation method according to claim 13 or claim 14, comprising a step (100) of filling the container (VES) with a gas via the gas line (GL).

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