METHOD FOR MANUFACTURING SCHOTTKY DIODE AND CORRESPONDING INTEGRATED CIRCUIT
The Schottky diode structure with a polysilicon layer and insulated metal contacts addresses parasitic effects, enhancing breakdown voltage and reducing current leakage, ensuring effective protection against electrostatic discharges without additional manufacturing steps.
Patent Information
- Application Number
- FR2022007485
- Authority / Receiving Office
- FR · FR
- Patent Type
- Patents
- Current Assignee / Owner
- Filing Date
- 2022-07-21
- Publication Date
- 2025-10-24
- Estimated Expiration
- 2042-07-21
AI Technical Summary
Conventional Schottky diodes suffer from parasitic effects such as parasitic currents and capacitances due to the formation of parasitic bipolar transistors at the metal-semiconductor junctions, leading to increased current leakage and reduced breakdown voltage, which can result in diode destruction.
A Schottky diode structure is designed with a polysilicon layer on a dielectric layer extending deep into the substrate, featuring N-type doped and undoped regions with insulated metal contacts, eliminating the need for heavily doped P-type regions to smooth electric field lines and preventing parasitic effects.
The proposed diode structure avoids parasitic effects, reduces current leakage, and maintains a higher breakdown voltage, thereby protecting integrated circuits from electrostatic discharges without additional manufacturing steps.
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Abstract
Description
Title of the invention: METHOD FOR MANUFACTURING A SCHOTTKY DIODE AND CORRESPONDING INTEGRATED CIRCUIT
[0001] Embodiments and implementations relate to integrated circuits, in particular to Schottky diode manufacturing methods.
[0002] A Schottky diode is an electronic component used for the protection of integrated circuits against electrostatic discharges. An integrated circuit may be provided in an electronic system manufactured from a common substrate, and may for example be designed with a Schottky diode in order to reduce the injection of currents into the substrate, in particular currents from other circuits in the system during its operation.
[0003] The Schottky diode typically has a relatively low voltage threshold and can be forward or reverse biased depending on the voltage applied between the semiconductor region, the cathode, and the conductive region, the anode, of the Schottky diode. More particularly, metal contacts are typically provided on the anode and the cathode and allow a circuit to be connected to the anode and the cathode.
[0004] During forward bias, the current flows from the anode to the cathode via an N-type doped semiconductor well, usually buried in a P-type doped substrate. In particular, the anode forms with the semiconductor well a junction electrically insulated from the cathode by a dielectric layer. The dielectric layer also allows the metal contacts of the anode and cathode regions to be sufficiently distant to avoid a short circuit when the current passes.
[0005] However, the dielectric layer has angular ends at which electric field lines produced between the anode and the cathode become abrupt, thus causing greater current leakage in the substrate and a decrease in the breakdown voltage (known as "breakdown voltage") between the anode and the cathode. A lower breakdown voltage increases the risk of destruction of the diode when it is biased by a voltage higher than the breakdown voltage.
[0006] In this respect, a conventional Schottky diode structure provides for the implantation of heavily doped P-type regions, with an ion concentration typically between 112 and 116 atoms / cm3, between the anode and the dielectric layer. In particular, these implantation regions, often in the form of a ring, make it possible to smooth the electric field lines at the ends of the dielectric layer.
[0007] However, the junctions formed by association by the implantation regions heavily doped P, the N-doped semiconductor well and the P-doped substrate can reproduce the behavior of a bipolar transistor within the structure of the Schottky diode and can therefore lead to parasitic effects, which can subsequently be called "parasitic bipolar transistor" of the diode.
[0008] More particularly, these effects can be the formation of a parasitic capacitance and a generation of parasitic currents which can circulate in the substrate both during reverse biasing, that is to say when the current flows from the cathode to the anode, and during forward biasing of the diode via these junctions. There then remains an undesirable current generated by the Schottky diode in addition to the current injected by the different circuits of the system circulating in the common substrate.
[0009] There is therefore a need to propose a solution making it possible to design a Schottky diode which does not have parasitic currents in its substrate and which makes it possible to limit the injection of current within an electronic system.
[0010] According to one aspect, there is provided a semiconductor device comprising at least one Schottky diode on a substrate, said at least one Schottky diode comprising a polysilicon layer disposed on a dielectric layer extending deep into the substrate and adapted to electrically insulate the polysilicon layer from the substrate, the polysilicon layer having at least one first N-type doped region, called the cathode region, adjacent to at least one second undoped region, called the anode region, a first metal contact disposed on the surface of said at least one first region and a second metal contact disposed on the surface of said at least one second region such that said first metal contact and said second metal contact are adapted to be electrically isolated from each other.
[0011] In other words, a Schottky diode is proposed having a particular topology in which the anode and the cathode are located above the dielectric layer. This particular topology makes it possible to avoid excessively steep electric field lines occurring between the anode and the cathode and therefore does not require the implantation of heavily doped P-type regions at the metal-semiconductor junction of the diode to smooth these electric field lines.
[0012] Therefore, the Schottky diode does not suffer from the parasitic effects associated with the "parasitic bipolar transistor" such as unwanted currents and capacitances.
[0013] Furthermore, the dielectric layer located between the diode and the substrate makes it possible to limit, or even prevent, the passage of a current between the Schottky diode and the substrate, in particular the currents generated by the “parasitic bipolar transistor”.
[0014] According to one embodiment, said first metal contact and said second metal contact are insulated from each other by an oxide layer extending over the polysilicon layer.
[0015] The oxide layer ensures electrical insulation between the first metal contact and the second metal contact. In fact, the metal contacts are used to circulate a current in each anode and cathode and can be insulated from each other by the oxide layer to avoid electrical interference between the different anode and cathode regions.
[0016] According to one embodiment, the material of the metal contacts is a nickel-platinum alloy.
[0017] A nickel and platinum alloy has advantageous electrical conduction characteristics.
[0018] According to one embodiment, the device further comprises at least one non-volatile memory cell comprising a stack of N-type doped polysilicon and a metal contact arranged on the surface of said polysilicon stack. Advantageously: - said polysilicon stack has the same thickness, composition and dopant concentration as the first region of the polysilicon layer, and - said metal contact has the same composition as the first metal contact and the second metal contact.
[0019] According to one embodiment, the device further comprises at least one low-voltage MOS transistor comprising a polysilicon gate region, N-type doped conductive regions and a metal contact arranged on the surface of said gate region. Advantageously: - said polysilicon gate region has the same thickness and composition as the polysilicon layer, - said conductive regions have the same concentration of dopants as the first region of the polysilicon layer, and - said metal contact has the same composition as the first metal contact and the second metal contact.
[0020] According to another aspect, there is also proposed a system for protection against current injections into the substrate, comprising a circuit capable of generating currents in the substrate, the semiconductor device as defined previously, in which said at least one Schottky diode is coupled in parallel to the circuit and configured to limit, or even eliminate, the currents generated by the circuit in the substrate.
[0021] A device comprising a Schottky diode according to this aspect advantageously makes it possible to reduce, or even eliminate, current injections into the substrate of the different circuits of the same system.
[0022] According to another aspect, there is provided a method of manufacturing at least one diode Schottky on a substrate comprising:
[0023] - a formation of a dielectric layer in the substrate so that the di layer electrical extends deep into the substrate,
[0024] - a formation of a polysilicon layer on the dielectric layer, the layer dielectric being adapted to electrically insulate the polysilicon layer from the substrate,
[0025] - doping the polysilicon layer so as to form at least a first N-type doped region, called cathode region, adjacent to at least one second undoped region, called anode region, of the polysilicon layer,
[0026] - a formation of a first metallic contact on the surface of said at least one first region and a second metal contact on the surface of said at least one second region such that said first metal contact and said second metal contact are adapted to be electrically insulated from each other.
[0027] According to one embodiment, the doping of the polysilicon layer comprises masking and etching adapted to form openings at the level of said at least one first region of the polysilicon layer and ion implantation on the polysilicon layer at the level of said openings.
[0028] The different doped regions can thus be formed simultaneously at specific locations in the polysilicon layer.
[0029] According to one embodiment, the formation of the first metal contact and the second metal contact comprises:
[0030] - a formation of an oxide layer extending over the polysilicon layer,
[0031] - an etching of the oxide layer partially uncovering said at least one first region and said at least second region of the polysilicon layer, and
[0032] - a siliciding on the surface of said at least one first region and on the surface of said at least one second region such that said first metal contact and said second metal contact are insulated from each other by the oxide layer.
[0033] According to one embodiment, the material of the metal contacts is a nickel-platinum alloy.
[0034] According to one embodiment, the method further comprises manufacturing at least one non-volatile memory cell comprising: - formation of a polysilicon stack carried out simultaneously with the formation of the polysilicon layer, - an N-type doping of said polysilicon stack carried out simultaneously with the doping of the polysilicon layer, and - formation of a metal contact on the surface of said polysilicon stack carried out simultaneously with the formation of the first metal contact and the second metal contact.
[0035] A cointegration of Schottky diodes with non-volatile memory cells makes it possible to manufacture the Schottky diodes “free of charge” in the same process, in particular during the common steps of formation, doping of the poly-silicon layer and formation of the metal contacts. By “free of charge”, it is meant that the process does not require additional steps dedicated exclusively to the formation of the Schottky diodes and therefore makes it possible to reduce the number of steps for the manufacture of the IC semiconductor device, which thus reduces the cost and production time of such an IC device.
[0036] According to one embodiment, the method further comprises manufacturing at least one low-voltage MOS transistor comprising:
[0037] - a formation of a polysilicon gate region carried out simultaneously with the formation of the polysilicon layer,
[0038] - a formation of N-type doped conductive regions carried out simultaneously with the doping of the polysilicon layer, and
[0039] - a formation of a metal contact on the surface of said grid region produced simultaneously with the formation of the first metal contact and the second metal contact.
[0040] A cointegration of Schottky diodes with MOS transistors makes it possible to manufacture the Schottky diodes “free of charge” in the same process, in particular during the steps of forming the gate, source and drain regions as well as during the formation of the metal contacts. By “free of charge”, it is meant that the process does not require additional steps dedicated exclusively to the formation of the Schottky diodes and therefore makes it possible to reduce the number of steps for the manufacture of the IC semiconductor device, which thus reduces the cost and production time of such an IC device.
[0041] Other advantages and characteristics of the invention will appear on examining the detailed description of modes of implementation and embodiment, which are in no way limiting, and the appended drawings in which:
[0042] [Fig.l]
[0043] [Fig.2]
[0044] [Fig.3]
[0045] [Fig.4]
[0046] [Fig.5]
[0047] [Fig.6]
[0048] [Fig.7]
[0049] [Fig. 8]
[0050] [Fig.9]
[0051] [Fig. 10] schematically illustrate embodiments and implementations of the invention.
[0052] [Fig.l] schematically illustrates a semiconductor device IC comprising at least one Schottky diode, for example three diodes D_SCH1, D_SCH2 and D_SCH3, on a substrate SUB. The material of the substrate SUB is typically silicon. The diodes D_SCH1, D_SCH2 and D_SCH3 comprise a layer of polysilicon POLY disposed on a dielectric layer STI.
[0053] The STI dielectric layer is typically a shallow electrical isolation trench (usually referred to as "Shallow Trench Isolation" in English) and is adapted to electrically isolate the polysilicon layer POLY from the substrate SUB. The STI dielectric layer extends deep into the substrate SUB, for example from the surface of the substrate SUB and has a thickness El of between 200 nm and 1000 nm.
[0054] The polysilicon layer POLY, also called poly-Si, is preferably a layer common to the diodes D_SCH1, D_SCH2 and D_SCH3 and has a thickness E2 of between 50 nm and 200 nm.
[0055] Each Schottky diode D_SCH1, D_SCH2 and D_SCH3 comprises a junction comprising a cathode region, corresponding to a first CA region, and an anode region corresponding to a second AN region of the POLY polysilicon layer. The first CA region is N-type doped unlike the second AN region which is not doped. The first CA region has an ion concentration of between 13 and 16 atoms / cm3.
[0056] Furthermore, the Schottky diodes D_SCH1, D_SCH2 and D_SCH3 comprise a first metal contact CA_MC and a second metal contact AN_MC. The first metal contact CA_MC is arranged on the surface of the first region CA of each of the diodes and the second metal contact AN_MC is arranged on the surface of the second region AN of each of the diodes such that the first metal contact CA_MC and the second metal contact AN_MC are adapted to be electrically isolated from each other. In particular, the first metal contact CA_MC and the second metal contact AN_MC are sufficiently distant from each other to prevent any electrical connection between the first contact CA_MC and the second contact AN_MC. A person skilled in the art will be able to determine the distance between the first metal contact CA_MC and the second metal contact AN_MC to enable them to be electrically isolated. For example, a distance of between 100 nm and 2 pm may be provided..
[0057] Advantageously, the first metal contact CA_MC and the second metal contact AN_MC are insulated from each other by an oxide layer MSK_SIL extending over the polysilicon layer POLY. The material of the oxide layer MSK_SIL may be silicon oxide SiO2 for example. The oxide layer MSK_SIL has an E3 thickness between 1 nm and 50 nm.
[0058] The MSK_SIL oxide layer ensures better electrical insulation between the first metal contact and the second metal contact.
[0059] The first contact CA_MC and the second contact AN_MC respectively of each of the diodes D_SCH1, D_SCH2 and D_SCH3 make it possible to connect an electronic circuit (not shown) to the anode and the cathode of each of the diodes. In particular, the first contact CA_MC makes it possible to circulate a current in the first region CA and the second contact AN_MC makes it possible to circulate a current in the second region AN. Furthermore, the electrical insulation between the first contact CA_MC and the second contact AN_MC prevents the passage of current between the first contact CA_MC and the second region AN and the passage of current between the second contact AN_MC and the first region CA. Thus, electrical interference between the diodes D_SCH1, D_SCH2 and D_SCH3 is limited.
[0060] Each Schottky diode has a particular topology in which the anode and the cathode are located above the STI dielectric layer. This particular topology makes it possible to avoid excessively abrupt electric field lines occurring between the anode and the cathode and therefore does not require implanting P-doped regions at the metal-semiconductor junction of each diode to smooth these electric field lines.
[0061] Therefore, each of the Schottky diodes does not suffer from the parasitic effects linked to the “parasitic bipolar transistor” such as unwanted currents and capacitances.
[0062] Furthermore, the dielectric layer STI located between the diodes D_SCH1, D_SCH2 and D_SCH3 and the substrate SUB makes it possible to limit, or even prevent, the passage of a current between the diodes and the substrate, in particular the currents generated by the “parasitic bipolar transistor”.
[0063] Advantageously, the material of the first metal contact CA_MC and of the second metal contact AN_MC is a nickel-platinum alloy of chemical formula NiPt. The nickel-platinum alloy in fact has resistance to oxidation at room temperature and relatively high conductivity.
[0064] [Fig. 2] schematically illustrates an alternative of the semiconductor device IC, in which the diodes D_SCH1, D_SCH2 and D_SCH3 have been manufactured in cointegration with other electronic components. By "cointegration" is meant that the Schottky diodes can be manufactured together with other components in a common manufacturing process which may include in particular steps of manufacturing the diodes and the other components carried out simultaneously, as described below.
[0065] More particularly, the semiconductor device IC comprises at least one non-volatile memory cell CELL, for example two memory cells, and at least one low-voltage MOS transistor LV, for example four low-voltage transistors.
[0066] The memory cells CELL each comprise a stack of N-type doped polysilicon CELL_POLY and a metal contact CELL_MC arranged on the surface of the stack of polysilicon CELL_POLY.
[0067] The CELL_POLY polysilicon stack has the same thickness E2, the same composition and the same dopant concentration as the first CA region of the POLY polysilicon layer.
[0068] Furthermore, the metal contact CELL_MC has the same composition as the first metal contact CA_MC and the second metal contact AN_MC.
[0069] The low-voltage MOS transistors LV each comprise a polysilicon gate region GOX and conductive regions, i.e. a source region S and a drain region D, doped with N type. In addition, the low-voltage MOS transistors LV comprise a metal contact LV_MC arranged on the surface of the gate region GOX.
[0070] The polysilicon gate region GOX has the same thickness E2 and the same composition as the polysilicon layer POLY and the conductive regions S, D have the same dopant concentration as the first region CA of the polysilicon layer POLY.
[0071] Furthermore, the metal contact LV_MC has the same composition as the first metal contact CA_MC and the second metal contact AN_MC.
[0072] [Fig.3] illustrates a protection system SYS against current injections in the SUB substrate.
[0073] The system SYS comprises a CONV circuit and the semiconductor device as previously described in relation to [Fig.l] or 2. The CONV circuit may be a direct voltage converter (usually referred to as a "DC-DC converter" or "direct-direct converter") for example. The CONV circuit may be connected to a power source PWR making it possible to deliver a direct current Ipwr to the CONV circuit.
[0074] At least one of the Schottky diodes D_SCH1, D_SCH2 and D_SCH3, for example the diode D_SCH1, is coupled in parallel to the CONV circuit between the CONV circuit and the power source PWR. The diode D_SCH1 is thus configured to limit, or even eliminate, the injection of a portion of the current Ipwr by the CONV circuit into the substrate SUB.
[0075] [Fig.4] schematically illustrates a mode of implementation of a method of fa brication of Schottky diodes D_SCH1, D_SCH2 and D_SCH3. Such a fabrication method is used to form a semiconductor device IC, as shown in [Fig.l] and 2.
[0076] The method comprises forming 100 an STI dielectric layer in a SUB substrate. [Fig.5] schematically illustrates a result of the formation 100 of the STI dielectric layer in a sectional view.
[0077] The STI dielectric layer is known to be formed between electronic components of an integrated circuit in order to prevent current leakage from one component to another. As will be described later, the method advantageously uses such an STI dielectric layer not only to isolate two components located next to each other, but also to isolate the substrate SUB from components that may be subsequently formed above the STI dielectric layer, such as the Schottky diodes D_SCH1, D_SCH2 and D_SCH3.
[0078] The formation 100 of the dielectric layer STI can be carried out by etching the silicon of the substrate SUB so as to form a trench in depth of the substrate SUB and by filling the trench with a dielectric material, such as silicon dioxide of chemical formula SiO2 for example. The electrical insulation capacity of the dielectric layer depends on several factors such as the choice of the dielectric material and the thickness of the dielectric layer STI.
[0079] Indeed, the dielectric layer STI can provide a thickness El of between 200 nm and 1000 nm.
[0080] The method also comprises a formation 101 of a layer of polysilicon POLY on the dielectric layer STI. [Fig.6] schematically illustrates a result of the formation 101 of the layer of polysilicon POLY according to a sectional view.
[0081] As explained above, the dielectric layer STI is suitable for electrically insulating the polysilicon layer POLY from the substrate SUB. The polysilicon layer POLY can be, for example, formed by low pressure chemical vapor deposition, better known by the English acronym “LPCVD” for “Low Pressure Chemical Vapor Deposition”.
[0082] The polysilicon layer POLY can cover both partially and completely the dielectric layer STI, so as not to be in direct contact with the substrate SUB.
[0083] The method comprises a 102 doping of the polysilicon layer POLY. [Fig.7] schematically illustrates a 102 doping of the polysilicon layer POLY, in particular during an ion implantation step, according to a sectional view. The 102 doping is carried out so as to form at least a first CA region, for example three regions, doped with N type adjacent to at least a second undoped AN region, for example three regions, of the polysilicon layer POLY. The steps for carrying out the 102 doping are detailed below and are in no way limiting.
[0084] First, masking and etching are performed on the polysilicon layer POLY. An example of masking and etching is shown in [Fig.7] in which a MSK_IPL mask was previously formed on the POLY polysilicon layer and then etched.
[0085] In particular, the masking and etching are adapted to form openings at the level of the first CA regions of the polysilicon layer POLY.
[0086] An ion implantation is then carried out on the polysilicon layer POLY at the level of said openings. The ions are implanted in the first CA regions located under the openings of the MSK_IPL mask. Preferably, the ion concentration of the first CA regions after doping is between Ie 12 and Ie 16 atoms / cm3. The MSK_IPL mask prevents the ions from reaching the second AN regions covered by this MSK_IPL mask.
[0087] For example, the first CA regions can be doped in the same way as source and drain regions of a MOS transistor or lightly doped drain regions, usually called “LDD” for “Low Doped Drain” in English. The first CA regions in this case have an ionic concentration of less than 115 atoms / cm3. Cointegration with MOS transistors can thus be facilitated by choosing one or the other of these types of doping.
[0088] The first CA regions may also undergo predoping which may be advantageous for cointegration with CELL memory cells.
[0089] At the end of the ion implantation, a removal of the MSK_IPL mask can be carried out (not shown) revealing the surfaces of the first N-type doped CA regions, corresponding to the cathode regions, and of the second undoped AN regions, corresponding to the anode regions of the diodes D_SCH1, D_SCH2 and D_SCH3.
[0090] The method comprises a formation of CA_MC and AN_MC metal contacts on the surface of the POLY polysilicon layer. The formation of the metal contacts comprises an etching 103 of an MSK_SIL oxide layer and a siliciding 104 carried out on the surface of the first CA regions and the second AN regions of the POLY polysilicon layer.
[0091] [Fig.8] schematically illustrates the result of the formation and etching 103 of the MSK_SIL oxide layer according to a sectional view.
[0092] The MSK_SIL oxide layer extends over the POLY polysilicon layer and covers the surfaces of the first CA regions and the second AN regions. The material of the MSK_SIL oxide layer may be, for example, silicon oxide (SiO2).
[0093] The etching 103 of the MSK_SIL oxide layer partially uncovers the first CA regions and the second AN regions of the POLY polysilicon layer. More particularly, the etching 103 makes it possible to remove the MSK_SIL oxide layer on either side of the junctions between the first CA regions and the second AN regions.
[0094] On the one hand, the MSK_SIL oxide layer, like a mask, makes it possible to avoid the formation of metal contacts on or near the junctions between the first CA regions and the second AN regions and to form, on the other hand, openings at the locations where the MSK_SIL oxide layer has been etched.
[0095] [Fig.9] schematically illustrates the result of siliciding 104 according to a sectional view.
[0096] The siliciding 104 is carried out on the surface of the first CA regions and the second AN regions of the polysilicon layer POLY, under the openings formed by the mask MSK_SIL. The siliciding 104 is a technique well known to those skilled in the art making it possible to transform by chemical reaction the polycrystalline silicon on the surface of the first CA regions and the second AN regions into a silicide.
[0097] In particular, the silicide can be obtained by diffusing metals into the silicon. For example, metals such as platinum and nickel can be diffused into the polysilicon POLY layer through the openings to form a silicide layer of a nickel-platinum alloy (NiPt). The siliciding 104 makes it possible to improve the ohmic contact between the silicide layer and the polysilicon POLY layer.
[0098] Therefore, the silicide layers form first CA_MC metal contacts on the surface of the first CA regions and second AN_MC metal contacts on the surface of the second AN regions.
[0099] Furthermore, the first metal contacts CA_MC and the second metal contacts AN_MC are adapted to be insulated from each other by the oxide layer MSK_SIL.
[0100] [Fig. 10] illustrates the method of manufacturing Schottky diodes D_SCH1, D_SCH2 and D_SCH3 according to another variant making it possible to obtain the semiconductor device described in relation to [Fig.2].
[0101] The method according to this variant comprises the formation 101 of the polysilicon layer POLY, the doping 102 of the polysilicon layer POLY and the formation of the metal contacts CA_MC and AN_MC as described previously in relation to figures 6, 7, 8 and 9 in cointegration with other electronic components.
[0102] On the one hand, the method can comprise a fabrication of non-volatile memory cells CELL. The formation 101 of the polysilicon layer POLY is carried out simultaneously for the fabrication of memory cells CELL and the diodes D_SCH1, D_SCH2 and D_SCH3 as is schematically illustrated in [Fig. 10].
[0103] On the other hand, the method may comprise a fabrication of low-voltage MOS transistors LV. The fabrication of low-voltage MOS transistors LV comprises a formation of polysilicon GOX gate regions carried out simultaneously with the formation 101 of the polysilicon layer POLY.
[0104] The fabrication of the non-volatile memory cells CELL comprises a formation of a polysilicon stack CELL_POLY and an N-type doping of the polysilicon stack CELL_POLY. The formation of the polysilicon stack CELL_POLY is carried out simultaneously with the formation of the polysilicon layer POLY. The N-type doping of the polysilicon stack CELL_POLY is carried out simultaneously with the doping of the polysilicon layer POLY. The polysilicon stack CELL_POLY can be doped by one of the ion implantations mentioned previously as an example. The fabrication of the non-volatile memory cells CELL also comprises a formation of a metal contact CELL_MC on the surface of the polysilicon stack CELL_POLY. The formation of the metal contact CELL_MC is carried out simultaneously with the formation of the first metal contact CA_MC and the second metal contact AN_MC.
[0105] The fabrication of the low-voltage MOS transistors LV also comprises a formation of conductive regions, i.e. a source region S and a drain region D, and a formation of a metal contact LV_MC on the surface of the gate region GOX. The formation of the conductive regions is carried out simultaneously with the 102 doping of the polysilicon layer POLY. More particularly, the 102 doping makes it possible to apply an N-type doping, for example by one of the examples of ion implantation mentioned previously, to form the cathode regions CA of the diodes D_SCH1, D_SCH2 and D_SCH3 and the semiconductor regions of the low-voltage MOS transistors LV.
[0106] The formation of a metal contact LV_MC on the surface of the gate region GOX is carried out simultaneously with the formation 103 of the first metal contact CA_MC and the second metal contact AN_MC.
[0107] The manufacture of Schottky diodes D_SCH1, D_SCH2 and D_SCH3 according to this variant makes it possible to manufacture the Schottky diodes “free of charge” in the same process, in particular during the steps common to the manufacture of memory cells CELL and / or low-voltage MOS transistors LV. By “free of charge”, it is meant that the process does not require additional steps dedicated exclusively to the formation of the Schottky diodes D_SCH1, D_SCH2 and D_SCH3 and therefore makes it possible to reduce the number of steps for the manufacture of the semiconductor device IC, which thus reduces the cost and production time of such an IC device.
Claims
Claims
1. Semiconductor device comprising at least one Schottky diode on a substrate (SUB), said at least one Schottky diode (D_SCH1, D_SCH2, D_SCH3) comprising a polysilicon layer (POLY) arranged on a dielectric layer (STI) extending deep into the substrate (SUB) and adapted to electrically insulate the polysilicon layer (POLY) from the substrate (SUB), the polysilicon layer (POLY) having at least one first N-type doped region (CA), called the cathode region, adjacent to at least one second undoped region (AN), called the anode region, a first metal contact (CA_MC) arranged on the surface of said at least one first region (CA) and a second metal contact (AN) arranged on the surface of said at least one second region (AN) such that said first metal contact (CA_MC) and said second metal contact (AN_MC) are adapted to be electrically isolated from each other,the device further comprising at least one non-volatile memory cell (CELL) comprising a stack of N-type doped polysilicon (CELL_POLY) and a metal contact (CELL_MC) arranged on the surface of said stack of polysilicon (CELL_POLY), in which: said stack of polysilicon (CELL_POLY) has the same thickness (E2), the same composition and the same concentration of dopants as the first region (CA) of the layer of polysilicon (POLY), - said metal contact (CELL_MC) has the same composition as the first metal contact (CA_MC) and as the second metal contact (AN_MC).,
2. A semiconductor device according to claim 1, wherein said first metal contact (CA_MC) and said second metal contact (AN_MC) are insulated from each other by an oxide layer (MSK_SIL) extending over the polysilicon layer (POLY).
3. A semiconductor device according to claim 1 or 2, wherein the material of the metal contacts (CA_MC, AN_MC) is a nickel-platinum alloy.
4. Semiconductor device according to one of the preceding claims, further comprising at least one low-voltage MOS transistor (LV) comprising a polysilicon gate region (GOX), N-type doped conductive regions (S, D) and a metal contact (LV_MC) arranged on the surface of the grid region (GOX), in which: - said polysilicon gate region (GOX) has the same thickness (E2) and the same composition as the polysilicon layer (POLY), - said conductive regions (S, D) have the same dopant concentration as the first region (CA) of the polysilicon layer (POLY), - said metal contact (LV_MC) has the same composition as the first metal contact (CA_MC) and the second metal contact (AN_MC).
5. System (SYS) for protection against current injections into the substrate (SUB), comprising: - a circuit (CONV) capable of generating currents in the substrate (SUB), - the semiconductor device (IC) as defined by claims 1 to 4, wherein said at least one Schottky diode (D_SCH1, D_SCH2) is coupled in parallel to the circuit (CONV) and configured to limit the currents generated by the circuit (CONV) in the substrate (SUB).
6. Method for manufacturing at least one Schottky diode (D_SCH1, D_SCH2, D_SCH3) on a substrate (SUB) comprising: - a formation of a dielectric layer (STI) in the substrate (SUB) such that the dielectric layer (STI) extends deep into the substrate (SUB), - a formation of a polysilicon layer (POLY) on the dielectric layer (STI), the dielectric layer (STI) being adapted to electrically insulate the polysilicon layer (POLY) from the substrate (SUB), - a doping of the polysilicon layer (POLY) so as to form at least a first N-type doped region (CA), called the cathode region, adjacent to at least a second undoped region (AN), called the anode region, of the polysilicon layer (POLY), - a formation of a first metal contact (CA_MC) on the surface of said at least one first region (CA) and of a second metal contact (AN_MC) on the surface of said at least one second region (AN) so that said first metal contact (CA_MC) and said second metal contact (AN_MC) are adapted to be electrically isolated from each other, the method further comprising a fabrication of at least one non-volatile memory cell (CEL) comprising: - a formation of a polysilicon stack (CELL_POLY) carried out simultaneously with the formation of the polysilicon layer (POLY), - an N-type doping of said polysilicon stack (CELL_POLY) carried out simultaneously with the doping of the polysilicon layer (POLY), and - a formation of a metal contact (CELL_MC) on the surface of said polysilicon stack (CELL_POLY) carried out simultaneously with the formation of the first metal contact (CA_MC) and the second metal contact (AN_MC).
7. The method of claim 6, wherein the doping of the polysilicon (POLY) layer comprises masking and etching adapted to form openings at said at least one first region (CA) of the polysilicon (POLY) layer and ion implantation on the polysilicon (POLY) layer at said openings.
8. Method according to claim 6 or 7, wherein the formation of the first metal contact (CA_MC) and the second metal contact (AN_MC) comprises: - a formation of an oxide layer (MSK_SIL) extending over the polysilicon layer (POLY), - an etching of the oxide layer (MSK_SIL) partially uncovering said at least one first region (CA) and said at least one second region (AN) of the polysilicon layer (POLY), and - a surface siliciding of said at least one first region (CA) and of said at least one second region (AN) so that said first metal contact (CA_MC) and said second metal contact (AN_MC) are isolated from each other by the oxide layer (MSK_SIL).
9. Method according to one of claims 6 to 8, in which the material of the metal contacts (CA_MC, AN_MC) is a nickel-platinum alloy.
10. Method according to one of claims 6 to 9, further comprising a fabrication of at least one low-voltage MOS transistor (LV) comprising: - a formation of a polysilicon gate region (GOX) carried out simultaneously with the formation of the polysilicon layer (POLY), - a formation of N-type doped conductive regions (S, D) carried out simultaneously with the doping of the polysilicon layer (POLY), and - a formation of a metal contact (LV_MC) on the surface of said gate region (GOX) made simultaneously with the formation of the first metal contact (CA_MC) and the second metal contact (AN_MC).