CN1855550A - Semiconductor device - Google Patents
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- CN1855550A CN1855550A CN 200610073802 CN200610073802A CN1855550A CN 1855550 A CN1855550 A CN 1855550A CN 200610073802 CN200610073802 CN 200610073802 CN 200610073802 A CN200610073802 A CN 200610073802A CN 1855550 A CN1855550 A CN 1855550A
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Abstract
In a semiconductor device of the present invention, a protection diode for protecting a device is formed on an epitaxial layer formed on a substrate. A Schottky barrier metal layer is formed on a surface of the epitaxial layer and a P-type diffusion layer is formed at a lower portion of an end portion of the Schottky barrier metal layer. Then, P-type diffusion layers are formed in a floating state closer to a cathode region side than the P-type diffusion layer, and are capacitively coupled with a metal layer to which an anode potential is applied. This structure reduces a large change in a curvature of a depletion layer, thereby improving a withstand voltage characteristic of the protection diode.
Description
Technical field
The present invention relates to the semiconductor device that the protective circuit element is not destroyed by overvoltage.
Background technology
In existing semiconductor devices, on the N type semiconductor substrate, be formed with N type epitaxial loayer.On the n type diffused layer that is formed on the epitaxial loayer, overlapped to form p type diffused layer.And, on p type diffused layer, form anode electrode, and form cathode electrode at substrate back, utilize the PN junction of two diffusion layers and constitute Zener diode.Periphery at p type diffused layer is formed with P type protection zone, in addition, is formed with another protection zone in its outside.Be formed with the Schottky barrier metal level contiguously with the epitaxial loayer that is surrounded by two protection zones.Constitute Schottky barrier diode by Schottky barrier with the silicide and the epitaxial loayer of metal level.In existing semiconductor devices, Zener diode is connected side by side with Schottky barrier diode, reduce the forward voltage (Vf) (for example, with reference to patent documentation 1) of element self.
In existing semiconductor devices, be formed with the high p type diffused layer of impurity concentration on the surface in N type semiconductor zone, and between this diffusion layer, be formed with the low p type diffused layer of impurity concentration.Be formed at the electrode and the high p type diffused layer ohmic contact of impurity concentration of N type semiconductor region surface, and and the low p type diffused layer of impurity concentration between form Schottky barrier.Be formed with the Zener diode that uses PN junction in the formation zone of the high p type diffused layer of impurity concentration.On the other hand, be formed with the diode that constitutes by Zener diode and Schottky barrier in the formation zone of the low p type diffused layer of impurity concentration.By this structure, reduce the free carrier (hole) that injects to the N type semiconductor zone from p type diffused layer, reduce near the free carrier of accumulating the PN junction zone (hole).And, reduce reverse reverting current density (for example, with reference to patent documentation 2).
In existing planar-type semiconductor device, on be formed at the P type semiconductor zone in N type semiconductor zone, be formed with anode electrode.On the N type semiconductor zone, be formed with the conductivity field plate (Off ィ one Le De プ レ one ト) that is connected with anode electrode.In addition, the equipotential ring electrode that is formed on above the N type semiconductor zone is connected by the resistive field plate with the conductivity field plate.And, will be positioned at the thickness thickening of dielectric film of the bottom, border of conductivity field plate and resistive field plate, will be positioned at the reduced thickness of dielectric film of the resistive field plate bottom of equipotential ring electrode side.By this structure, strengthen the effect of resistive field plate, reduce the curvature of depletion layer of the bottom, border of conductivity field plate and resistive field plate.And, realized the withstand voltage raising (for example, with reference to patent documentation 3) in the zone that electric field is concentrated easily.
As mentioned above, in existing semiconductor devices, in an element, be connected with Zener diode and Schottky barrier diode side by side.By this structure, forward voltage (Vf) can utilize the characteristic of Schottky barrier diode, realizes low voltage drive.But in Schottky barrier diode, principal current is stream with the epitaxial loayer.Therefore, the dead resistance that has on the epitaxial loayer is big, can not reduce the problem of ON resistance value.
In addition, existing semiconductor devices in Zener diode, is formed with P type protection zone below the end of the anode electrode on be formed at epitaxial loayer.Equally, in Schottky barrier diode, below the end of Schottky barrier, be formed with P type protection zone with metal level.By this structure, by the concentrated easily zone of P type protection zone protection electric field.But in that P type protection zone is disposed in the structure of most peripheral, when applying reverse biased, near the end or the Schottky barrier usefulness end of metal level of anode electrode, the curvature of depletion layer changes easily.Particularly, when being disposed near the terminal area of depletion layer in described end, the curvature changing of depletion layer strengthens.As a result, electric field takes place easily in the zone that has had in the curvature changing of depletion layer concentrates, and is difficult to realize the problem of desirable voltage endurance.
In addition, in existing semiconductor devices, when Zener diode moves,, exceedingly accumulate as the free carrier (hole) of minority carrier in N type epitaxial loayer zone.And, when Zener diode is disconnected, be necessary this free carrier of accumulating (hole) is got rid of from p type diffused layer.At this moment, near free carrier (hole) concentration the p type diffused layer uprises, and it is big that the absolute value of the time rate of change of reverse reverting electric current (di/dt) becomes.And the time rate of change (di/dt) that has owing to the reverse reverting electric current causes the problem that the protection diode destroys.
In addition, in existing semiconductor devices, Zener diode is connected side by side with Schottky barrier diode, realizes low voltage drive.But when described diode used as the protection diode of the circuit element that constitutes high-frequency circuit, the parasitic capacitance in the Zener diode was big, has the problem that high frequency characteristics worsens.
Summary of the invention
The present invention constitutes in view of described problem, and semiconductor device of the present invention is characterized in that, comprising: first and second anode diffusion layer of opposite conductivity type, and it is separated on the semiconductor layer of a conduction type and forms; The cathode diffusion layer of one conduction type, it is formed on the described semiconductor layer; Insulating barrier, it is formed on above the described semiconductor layer; Anode electrode, it is connected with described first and second anode diffusion layer via the contact hole that is formed on the described insulating barrier, and engages with described semiconductor layer Schottky between described first anode diffusion layer and the second plate diffusion layer; The third anode diffusion layer of opposite conductivity type, its on the described semiconductor layer between described second plate diffusion layer and the described cathode diffusion layer via described insulating barrier and described anode electrode or be connected the metal level capacitive coupling of described anode electrode.Therefore, in the present invention, because the protection diode is to be lower than forward voltage (Vf) the ON action (turn-on action) of circuit element, so can not destroyed by overvoltage by the protective circuit element.In addition, in anode region, the 3rd anode diffusion layer is configured in outermost layer.According to this structure, can prevent the withstand voltage deterioration of anode electrode end, the protection diode can be kept desirable voltage endurance.
Semiconductor device of the present invention is characterized in that, disposes above the described second plate diffusion layer of described semiconductor layer by offering the end of the described anode electrode that described contact hole forms.Therefore, in the present invention, the curvature changing of the depletion layer below the anode electrode end can be reduced, prevent that electric field is concentrated, and can prevent to protect the withstand voltage deterioration of diode.
Semiconductor device of the present invention is characterized in that, described third anode diffusion layer is made of the diffusion layer of two kinds of different opposite conductivity type of impurity concentration at least.Therefore, in the present invention, can prevent that the complete depleted layer of third anode diffusion layer is full of, third anode diffusion layer and anode electrode or be connected the metal level capacitive coupling of anode electrode.According to this structure, the third anode diffusion layer becomes the state that has applied electronegative potential, and the protection diode can be kept desirable voltage endurance.
Semiconductor device of the present invention is characterized in that, the diffusion layer of the described opposite conductivity type that the diffusion layer of the described opposite conductivity type that impurity concentration is low is higher than impurity concentration more extends to described cathode diffusion layer side.Therefore, in the present invention, at the third anode diffusion layer, the diffusion layer of the opposite conductivity type that the diffusion layer of the opposite conductivity type that impurity concentration is low is higher than impurity concentration more extends to the cathode diffusion layer side.According to this structure, can reduce the curvature changing on the terminal area of depletion layer, prevent that electric field from concentrating.And, can improve the voltage endurance of protecting diode.
Semiconductor device of the present invention is characterized in that, overlaps to form the discharge diffusion layer of opposite conductivity type on described cathode diffusion layer, connects cathode electrode in the discharge of described opposite conductivity type on diffusion layer.Therefore, in the present invention, in protection during diode action, via cathode diffusion layer, by again in conjunction with and the free carrier in the semiconductor layer (hole) is eliminated.In addition, can with diffusion layer the free carrier in the semiconductor layer (hole) be discharged via the discharge of the opposite conductivity type that has applied cathode potential.According to this structure, can reduce the absolute value of the time rate of change (di/dt) of reverse reverting electric current, prevent to protect the destruction of diode.
Semiconductor device of the present invention is characterized in that, described second plate diffusion layer surrounds described first anode diffusion layer and is configured on every side, and described first anode diffusion layer diffuses to more deep than described second plate diffusion layer.Therefore, in the present invention, first anode diffusion layer is diffused into the deep.According to this structure, strengthen the distance of leaving of first anode diffusion layer and second plate diffusion layer, and widely form the schottky junction zone.And, can prevent to protect the deterioration of the high frequency characteristics of diode, can improve the current capacity on the Schottky diode.
Semiconductor device of the present invention is characterized in that, disposes above described anode electrode to described anode electrode and applies the contact hole that the wiring layer of anode potential is used.Therefore, in the present invention, the anode electrode that can suppress to connect up draw around, dwindle the area of wiring pattern.
In semiconductor device of the present invention, dispose on the described semiconductor layer below the wiring layer that has applied described anode potential and the idiostatic electric field barrier film of described cathode diffusion layer, described electric field barrier film is configured in the zone that the wiring layer that applied described anode potential and described cathode diffusion layer intersect.Therefore, in the present invention, the wiring layer that the electric field barrier film is applied with anode potential relatively has shield effectiveness, can prevent the cathode zone counter-rotating, the situation that anode region and area of isolation are short-circuited.
In the present invention, on semiconductor layer, be formed with Zener diode and the Schottky barrier diode protection diode that disposes arranged side by side.The protection diode utilizes low forward voltage (Vf) characteristic of Schottky barrier diode.And the protection diode is connected side by side with the desired circuit element.By this structure, when circuit element applies overvoltage, the protection diode can prevent that than the first action of circuit element circuit element is destroyed.
In addition, in the present invention, below the end of Schottky barrier, be formed with p type diffused layer with metal level.And, at the p type diffused layer that more is formed with floating state than this p type diffused layer near the cathode zone side.By this structure, when on the protection diode, having applied reverse biased, reduce the curvature changing of Schottky barrier with the depletion layer of the below, end of metal level, improve voltage endurance.
In the present invention, the p type diffused layer of floating state is formed by impurity concentration low diffusion layer and the high diffusion layer of impurity concentration.By this structure, capacitive coupling such as the p type diffused layer of floating state and anode electrode, and on p type diffused layer, apply the current potential different with anode potential.
In the present invention, the low diffusion layer diffusion layer higher than impurity concentration of impurity concentration that constitutes the p type diffused layer of floating state more extends to cathode electrode side.By this structure, when the protection diode applied reverse biased, the curvature changing on the terminal area of depletion layer reduced, and can improve voltage endurance.
In the present invention, be formed with the p type diffused layer that has applied cathode potential at cathode zone.By this structure, when the protection diode action, can reduce the concentration of the free carrier (hole) in the semiconductor layer.And, can reduce the absolute value of the time rate of change (di/dt) of reverse reverting electric current, prevent to protect the destruction of diode.
In addition, in the present invention, the p type diffused layer that the p type diffused layer of shallow degree diffusion surrounds deep diffusion forms on every side.On two diffusion layers, apply anode potential, on the semiconductor layer surface between two diffusion layers, be formed with schottky junction.By this structure, can widely form the schottky junction zone, can improve the current capacity of Schottky diode.
Description of drawings
Fig. 1 (A), (B) are the profiles of the protection diode of explanation embodiment of the present invention;
Fig. 2 (A), (B) are the profiles of the PN diode of explanation embodiment of the present invention;
Fig. 3 is the figure of the forward voltage (Vf) of explanation protection diode of embodiment of the present invention and PN diode;
Fig. 4 is the figure that the circuit of the protection diode that is assembled with embodiment of the present invention is described;
Fig. 5 is the figure of the parasitic capacitance value of explanation protection diode of embodiment of the present invention and PN diode;
Fig. 6 (A) is the figure of Potential distribution of reverse bias condition of the protection diode of explanation embodiment of the present invention, (B) is the figure of the ionization by collision generation area on the protection diode of explanation embodiment of the present invention;
Fig. 7 is the figure of CONCENTRATION DISTRIBUTION of the free carrier (hole) of explanation protection diode of embodiment of the present invention and PN diode;
Fig. 8 is the plane graph of the protection diode of explanation embodiment of the present invention.
Symbol description
1 protection diode
2 p type single crystal silicon substrates
3 N type epitaxial loayers
5 p type diffused layers
7 n type diffused layers
9 p type diffused layers
10 p type diffused layers
11 p type diffused layers
12 p type diffused layers
14 Schottky barrier metal levels
18 metal levels
20 ends
21 silicide layers
Embodiment
Below, with reference to an execution mode of accompanying drawing 1～7 detailed description semiconductor device of the present invention.Fig. 1 (A) reaches the profile of the protection diode that (B) is the explanation present embodiment.Fig. 2 (A) reaches the profile of the PN diode that (B) is the explanation present embodiment.Fig. 3 is the figure of the forward voltage (Vf) of explanation protection diode of present embodiment and PN diode.Fig. 4 is the figure that the circuit of the protection diode that is assembled with present embodiment is described.Fig. 5 is the figure of the parasitic capacitance value of explanation protection diode of present embodiment and PN diode.Fig. 6 (A) is the protection diode about present embodiment, and the figure of the Potential distribution of reverse bias condition is described.Fig. 6 (B) is the figure of ionization by collision generation area on the protection diode of explanation present embodiment.Fig. 7 is the figure of CONCENTRATION DISTRIBUTION of the free carrier (hole) of explanation protection diode of present embodiment and PN diode.Fig. 8 is the profile of the protection diode of explanation present embodiment.
Shown in Fig. 1 (A), the structure that disposes the protection diode 1 of PN diode and Schottky barrier diode side by side mainly comprises: p type single crystal silicon substrate 2; N type epitaxial loayer 3; The N type is imbedded diffusion layer 4; P type diffused layer 5,6 as the anode region use; N type diffused layer 7,8 as the cathode zone use; P type diffused layer 9,10,11,12,13; Schottky barrier metal level 14 as the anode electrode use; Metal level 15 as the cathode electrode use; Insulating barrier 16,17; The metal level 18 that is connected with anode electrode.
N type epitaxial loayer 3 is deposited in above the p type single crystal silicon substrate 2.In addition, the epitaxial loayer in the present embodiment 3 is corresponding to " semiconductor layer " of the present invention.And, represented on substrate 2, to be formed with the situation of one deck epitaxial loayer 3 in the present embodiment, and the invention is not restricted to this.For example, as " semiconductor layer " of the present invention, also can be the situation that lamination has a plurality of epitaxial loayers on substrate.And,, can only be substrate also, and, also can be n type single crystal silicon substrate, compound semiconductor substrate as substrate as " semiconductor layer " of the present invention.
The N type is imbedded diffusion layer 4 and is formed on substrate 2 and epitaxial loayer 3 these two zones.As shown in the figure, the N type is imbedded diffusion layer 4 and is formed on the formation zone of the protection diode of being divided by area of isolation 19 1.
P type diffused layer 5,6 is formed on the epitaxial loayer 3.P type diffused layer 5 is 1.0E16～17 (/cm by for example its surface impurity concentration
2) about, diffusion depth is that diffusion conditions about 5～6 (μ m) forms.P type diffused layer 6 is 1.0E19～20 (/cm by for example its surface impurity concentration
2) about, diffusion depth is that diffusion conditions about 1～3 (μ m) forms.And p type diffused layer 5 forms N type epitaxial loayer 3 and PN junction zone, and p type diffused layer 5,6 is used as the anode region of PN diode.In addition, the p type diffused layer 5,6 corresponding " first anode diffusion layer of opposite conductivity type " of the present invention of present embodiment.But,, also can only be p type diffused layer 5 or p type diffused layer 6 as " first anode diffusion layer of opposite conductivity type " of the present invention.And also can for example forming on p type diffused layer 5,6, its surface impurity concentration be 1.0E17～18 (/cm
2) about, diffusion depth is the p type diffused layer about 2～4 (μ m), forms 3 heavy diffusion structures.
N type diffused layer 7,8 on epitaxial loayer 3, surround p type diffused layer 5 around and form a ring-type.N type diffused layer 7,8 and N type epitaxial loayer 3 are used as the cathode zone of PN diode and Schottky barrier diode.And,, reduce parasitic resistance values by n type diffused layer 7 is formed wide diffusion zone.On the other hand, n type diffused layer 8 is narrow diffusion zones, and by forming the high zone of impurity concentration, seeks low resistanceization.In addition, the n type diffused layer 7,8 corresponding " cathode diffusion layer of a conduction type " of the present invention of present embodiment.But, as " the cathode diffusion region territory of a conduction type " of the present invention, can only be n type diffused layer 5, also can be multilayer diffusion structures such as triple diffusion structure.
P type diffused layer 9 on epitaxial loayer 3, surround p type diffused layer 5 around and form a ring-type.P type diffused layer 9 is 1.0E15～16 (/cm by for example its surface impurity concentration
2) about, diffusion depth is that diffusion conditions about 1～3 (μ m) forms.P type diffused layer 9 is formed on the below that the Schottky barrier that becomes anode electrode is used the end 20 of metal level 14.Schottky barrier is concentrated mitigation with the electric field on the end 20 of metal level 14, and improve the voltage endurance of protection diode 1.In addition, the p type diffused layer 9 corresponding " the second plate diffusion layer of opposite conductivity type " of the present invention of present embodiment.But,, also can form MULTIPLE DIFFUSION structures such as triple diffusion structure as " the second plate diffusion layer of opposite conductivity type " of the present invention.
P type diffused layer 10,11 makes it form region overlapping and is formed on than p type diffused layer 9 more close n type diffused layer 7 sides.P type diffused layer 10,11 surround p type diffused layers 5 around and form a ring-type.P type diffused layer 10 is 1.0E15～16 (/cm by for example its surface impurity concentration
2) about, diffusion depth is that diffusion conditions about 1～3 (μ m) forms.And p type diffused layer 11 is 1.0E17～18 (/cm by for example its surface impurity concentration
2) about, diffusion depth is that diffusion conditions about 2～4 (μ m) forms.And p type diffused layer 10,11 forms as the diffusion layer of floating.In addition, be described in detail hereinafter, on p type diffused layer 10, overlap to form the impurity concentration p type diffused layer 11 higher than p type diffused layer 10.By this structure, can prevent the situation that the depleted layer of p type diffused layer 10,11 overlapping areas is full of when protection diode 1 applies reverse biased.Its result, p type diffused layer 10,11 overlapping areas can keep and metal level 18 or Schottky barrier metal level 14 capacity coupled states.In addition, the p type diffused layer 10,11 corresponding " the third anode diffusion layer of opposite conductivity type " of the present invention of present embodiment.But,,, under this condition, can carry out design alteration arbitrarily so long as not depleted layer of diffusion structure that is full of in part zone of p type diffused layer gets final product at least as " the third anode diffusion layer of opposite conductivity type " of the present invention.
P type diffused layer 12,13 overlapping its form the zone and are formed on the n type diffused layer 7.P type diffused layer 12,13 surround p type diffused layers 5 around and form a ring-type.P type diffused layer 12 is 1.0E16～17 (/cm by for example its surface impurity concentration
2) about, diffusion depth is that diffusion conditions about 5～6 (μ m) forms.P type diffused layer 13 is 1.0E19～20 (/cm by for example its surface impurity concentration
2) about, diffusion depth is that diffusion conditions about 1～3 (μ m) forms.And n type diffused layer 8 contacts with the metal level 15 that uses as cathode electrode with p type diffused layer 13.By this structure, p type diffused layer 12,13 and n type diffused layer 7,8 become idiostatic.In addition, the p type diffused layer 12,13 corresponding " the discharge diffusion layer of opposite conductivity type " of the present invention of present embodiment.But, as " the discharge diffusion layer of opposite conductivity type " of the present invention, also can only be p type diffused layer 5, in addition, can also be MULTIPLE DIFFUSION structures such as triple diffusion structure.
Schottky barrier is formed on above the epitaxial loayer 3 with metal level 14.Schottky barrier is for example piled up titanium nitride (TiN) layer with metal level 14 on titanium (Ti) layer.Shown in thick line, on the surface of the epitaxial loayer 3 between p type diffused layer 5 and the p type diffused layer 9, be formed with Titanium silicide (TiSi
2) layer be silicide layer 21.And, constitute Schottky barrier diode with the silicide layer 21 and the epitaxial loayer 3 of metal level 14 by Schottky barrier.In addition, also can replace titanium (Ti) layer and use tungsten (W), molybdenum (Mo), tantalum (Ta), cobalt (Co), nickel (Ni), platinum metals such as (Pt).At this moment, as silicide layer 20, be formed with tungsten silicide (WSi
2) layer, molybdenum silicide (MoSi
2) layer, cobalt silicide (CoSi
2) layer, nickel silicide (NiSi
2) layer, platinum silicide (PtSi
2) layer etc.
Metal level 15 is formed on above the epitaxial loayer 3.Metal level 15 be for example on barrier metal layer lamination the structure of aluminium silicon (AlSi) layer, aluminum bronze (AlCu) layer or aluminium copper silicon (AlSiCu) layer is arranged.And metal level 15 is used as cathode electrode, is applied with cathode potential on n type diffused layer 8 and p type diffused layer 13.
Insulating barrier 16,17 is formed on epitaxial loayer 3 tops.Insulating barrier 16,17 is optionally lamination silicon oxide layer, silicon nitride film, TEOS (Tetra-Ethyl-Orso-Silicate) film, BPSG (BoronPhosPho Silicate Glass) film, SOG (SPin On Glass) film etc. and form for example.On insulating barrier 16, be formed with contact hole 22.Contact hole 22 is buried underground with metal level 14 by Schottky barrier, and Schottky barrier is used as anode electrode with metal level 14.In addition, the insulating barrier 16,17 corresponding " insulating barrier " of the present invention of present embodiment.But, as " insulating barrier " of the present invention, so long as optionally lamination the film of described silicon oxide layer etc. get final product.
Metal level 18 covers the top, formation zone of p type diffused layer 10,11 and is formed on above the insulating barrier 17.Insulating barrier 18 be for example on barrier metal layer lamination the structure of aluminium silicon (AlSi) layer, aluminum bronze (AlCu) layer or aluminium copper silicon (AlSiCu) layer.The contact hole 23 that 18 pairs of insulating barriers are formed on the insulating barrier 17 is buried underground, is connected with metal level 14 with Schottky barrier.By this structure, the part of p type diffused layer 10,11 overlapping areas is via insulating barrier 16,17, field oxide film 23 etc. and metal level 18 capacitive coupling at least.And, on the part of p type diffused layer 10,11 overlapping areas, apply current potential at least than how much higher hope of anode electrode.At least the part of p type diffused layer 10,11 overlapping areas and N type epitaxial loayer 3 constitute reverse bias condition, improve the voltage endurance of protection diode 1.
In addition, in the present embodiment, shown in Fig. 1 (B), Schottky barrier with metal level 14 also can be shown in Fig. 1 (A) metal level 18 such, cover the top, formation zone of p type diffused layer 10,11 and form.In this case, at least the part of p type diffused layer 10,11 overlapping areas via insulating barrier 16, field oxide film 24 etc. and Schottky barrier with metal level 14 capacitive coupling.And, at least on the part of p type diffused layer 10,11 overlapping areas, for example can apply the current potential different by the thickness of adjusting insulating barrier 16,17 etc. with anode electrode, can adjust the voltage endurance of protection diode 1.
N type epitaxial loayer 33 is deposited in above the p type single crystal silicon substrate 32.The N type is imbedded diffusion layer 34 and is formed on substrate 32 and epitaxial loayer 33 these two zones.P type diffused layer 35,36,37 is formed on the epitaxial loayer 33.P type diffused layer 35,36 and N type epitaxial loayer 33 form the PN junction zone, and p type diffused layer 35,36,37 uses as the anode region of PN diode.
N type diffused layer 38,39 is formed on the epitaxial loayer 33.The cathode zone that n type diffused layer 38,39 and N type epitaxial loayer 33 are used as the PN diode uses.And p type diffused layer 40,41 is formed on the n type diffused layer 38.
Insulating barrier 42 is formed on above the epitaxial loayer 33, is formed with contact hole 43,44 on insulating barrier 42.Metal level 45 is connected with p type diffused layer 37 via contact hole 43, and is used as anode electrode.Metal level 46 is connected with n type diffused layer 39, p type diffused layer 41 via contact hole 44, and is used as cathode electrode.
Insulating barrier 47 is formed on the insulating barrier 42, is formed with contact hole 48 on insulating barrier 47.Metal level 49 is connected with metal level 45 via contact hole 48.And metal level 49 covers the top, formation zone of p type diffused layer 36 and forms, and has the field plate effect.
In addition, in the present embodiment, shown in Fig. 2 (B), the metal level 49 that metal level 45 also can be shown in Fig. 2 (A) is such, covers the top, formation zone of p type diffused layer 36 and forms.
Then, in Fig. 3, represent to protect the forward voltage (Vf) of diode 1, dot the forward voltage (Vf) of PN diode 31 with solid line.
Such described with reference to Figure 1, on protection diode 1, dispose PN diode and Schottky barrier diode side by side.According to this structure as can be known, for example when Vf was less than or equal to 0.8 (V), the forward current (If) of protection diode 1 was greater than PN diode 31, and current capacity is good.On the other hand, when for example If was 1.0E-8 (A), protection diode 1 drove with the electronegative potential that is lower than PN diode 31.Promptly; according to this element characteristic; is connected side by side with protection diode 1 by the MOS transistor that will be connected etc., when for example protecting MOS transistor etc. for example not to be subjected between cathode ray tube (Block ラ ゥ Application) discharge or the destruction of the overvoltage of generation when disconnecting such as the L load of induction-motor load etc. etc. with lead-out terminal.
Specifically, the circuit that is expressed as follows among Fig. 4, that is, between power line (Vcc) and ground connection (GND), be connected in series N channel type MOS transistor X, Y, and the drain electrode of the source electrode of MOS transistor X and MOS transistor Y is connected with lead-out terminal.
At this, illustrate on the lead-out terminal of the circuit that does not connect protection diode 1 between power line (Vcc) and the lead-out terminal to apply superpotential situation.Between source electrode-drain electrode of the MOS transistor X of the state that does not apply reverse biased, apply forward bias voltage drop by overvoltage.At this moment, flow through the electric current more than or equal to feasible value between source electrode-drain electrode, the PN junction zone is destroyed, and MOS transistor X is destroyed.
But, in the present embodiment, between power line (Vcc) and lead-out terminal, be connected with protection diode 1 and MOS transistor X side by side.At this moment, as described in reference Fig. 3,, then protect diode 1 action earlier, can make the most of electric current that produces by overvoltage flow to power line (Vcc) by protection diode 1 if on lead-out terminal, apply overvoltage.As a result, the electric current that will flow through between source electrode-drain electrode of MOS transistor X owing to overvoltage reduces, and can prevent the destruction in PN junction zone.
Then, expression is applied to voltage on the anode electrode and the relation of parasitic capacitance C (fF) in Fig. 5.And, represent to protect diode 1 with solid line, dot PN diode 31.
Such described with reference to Figure 1, on protection diode 1, dispose PN diode and Schottky barrier diode side by side.And, on protection diode 1, to compare with PN diode 31, the PN junction zone that is formed on the epitaxial loayer 3 is few.By this structure, when having applied reverse biased, the parasitic capacitance of protection diode 1 becomes and lacks than the parasitic capacitance of PN diode 31.And protection diode 1 can reduce the leakage of high-frequency signal by the minimizing of parasitic capacitance.For example, when circuit bank shown in Figure 4 was packed the efferent of high-frequency circuit into, protection diode 1 more can reduce the deterioration of high frequency characteristics than PN diode 31.
Then, in Fig. 6 (A), heavy line is represented the end regions of depletion layer, and dotted line is represented equipotential line, and chain-dotted line is represented the equipotential line of 328 (V).As shown in the figure, on p type diffused layer 10,11, has form and zone that be applied with the current potential higher slightly than anode potential as the diffusion layer of floating.P type diffused layer 10,11 overlapping areas are the high impurity concentration zone, shown in solid line, have the zone of depleted layer underfill.And as mentioned above, this is because p type diffused layer 10,11 and metal level 18 capacitive coupling that not depleted layer is full of.
In addition, the concentrated Schottky barrier of electric field taking place is easily protected by p type diffused layer 9 with the end 20 of metal level 14.As mentioned above, p type diffused layer is a low impurity concentration, and as shown in the figure, p type diffused layer 9 depleted layers are full of.But p type diffused layer 9 is between p type diffused layer 5,6 and p type diffused layer 10,11 that not depleted layer is full of.By this structure, with below the end 20 of metal level 14, the interval of equipotential line does not narrow down at Schottky barrier, becomes to be difficult to take place the state that electric field is concentrated.That is to say that p type diffused layer 9 is by being protected from the depletion layer of the border extension of p type diffused layer 5,6 and epitaxial loayer 3 with from the depletion layer of the border extension of p type diffused layer 10,11 and epitaxial loayer 3.
In the p type diffused layer 10,11, p type diffused layer 10 is extended to cathode electrode side.As implied above, p type diffused layer 10 is a low impurity concentration, and as shown in the figure, not depleted layer is full of.And in the zone that is formed with p type diffused layer 10, pass lentamente at the interval of equipotential line.That is, the p type diffused layer 10 that is full of of depleted layer is configured in the most peripheral of anode electrode side.By this structure, as shown in the figure, reduce the curvature changing in the terminal area of depletion layer, improve the voltage endurance of protection diode 1.Its result, the problem of the withstand voltage deterioration that improvement causes by forming Schottky barrier diode realizes the low forward driving of voltage (Vf) based on Schottky barrier diode.
As shown in the hatched area of Fig. 6 (B), ionization bumps near the zone that p type diffused layer 10 that is positioned at cathode electrode side and p type diffused layer 11 intersect.From this figure, also can learn,, prevent to take place easily Schottky barrier that electric field concentrates with the withstand voltage deterioration on the end 20 of metal level 14 by forming p type diffused layer 10,11.
Then, among Fig. 7, solid line represents to protect the CONCENTRATION DISTRIBUTION of the free carrier (hole) in the A-A section (with reference to Fig. 1 (A)) of diode 1, and dotted line is represented the CONCENTRATION DISTRIBUTION of the free carrier (hole) in the B-B section (with reference to Fig. 2 (A)) of PN diode 31.In addition, the longitudinal axis is represented the concentration of the free carrier (hole) in the epitaxial loayer, and transverse axis is represented the distance left from anode region.And, be illustrated in the CONCENTRATION DISTRIBUTION under the state that applies Vf=0.8 (V) on protection diode 1 and the PN diode 31 respectively among the figure.
At first, as shown in Figure 1, during 1 action of protection diode, apply forward voltage (Vf), and on epitaxial loayer 3, inject free carrier (hole) from p type diffused layer 5 in the PN junction zone of p type diffused layer 5 and N type epitaxial loayer 3.On the other hand, as shown in Figure 2, during 31 actions of PN diode, apply forward voltage (Vf) in the PN junction zone of p type diffused layer 34 and N type epitaxial loayer 33 equally, and on epitaxial loayer 33, inject free carrier (hole) from p type diffused layer 34.That is, protection diode 1 and PN diode 31 the two near zone at p type diffused layer 5,34 form the concentration in roughly the same free carrier (hole).
Then, as shown in Figure 1, in protection diode 1, by forming Schottky barrier diode, p type diffused layer 9 and p type diffused layer 10,11 separate and form.By this structure, apply the forward PN junction area decreases of voltage (Vf), and the free carrier (hole) that is injected on the N type epitaxial loayer 3 reduces.Its result compares with PN diode 31, and in protection diode 1, from the zone that p type diffused layer 5 leaves, the concentration of free carrier (hole) reduces.In addition, in epitaxial loayer 3, cause conductivity characteristic measurement modulation (Den Guide degree becomes Tone) by distribution free carrier (hole), principal current is with low ON resistance circulation.And, can solve the problem of the big Schottky barrier diode of ON resistance value.
At last, as shown in Figure 1, the cathode zone of protection diode 1 forms the dual diffusion structure that is made of n type diffused layer 7,8.By this structure, at n type diffused layer 7 near zones, the free carrier (hole) that injects from p type diffused layer 5 combines with the free carrier (electronics) that injects from n type diffused layer 7,8 again.At this moment, can spread significantly, promote combination again by making n type diffused layer 7.
In addition, in protection diode 1, on n type diffused layer 7, be formed with the p type diffused layer 12,13 that has applied cathode potential.And, not carrying out above-mentioned combination again, the free carrier (hole) that arrives p type diffused layer 12,13 is discharged outside epitaxial loayer 3 from p type diffused layer 12,13.Its result, near the concentration of the free carrier (hole) the cathode zone descends significantly, also can reduce the concentration of the free carrier (hole) in the epitaxial loayer 3.On the other hand, as shown in Figure 2, the cathode zone of PN diode 31 also has identical structure, and near the concentration of the free carrier (hole) the cathode zone descends significantly.
As mentioned above, form Schottky barrier diode, and form the cathode zone of discharging free carrier (hole) easily from epitaxial loayer 3 at protection diode 1.By this structure, can reduce the concentration of accumulating near the free carrier (hole) the PN junction zone of protection diode 1.Its result when protection diode 1 disconnects, reduces the absolute value of the time rate of change (di/dt) of reverse reverting electric current, can obtain soft recovery characteristics (Application Off ト リ カ バ リ one characteristic).And, the destruction that can prevent the protection diode 1 that the time rate of change (di/dt) by the reverse reverting electric current causes.
As shown in Figure 8, protection diode 1 for example forms ellipse.At oval-shaped linearity region L, on the central area, dispose the p type diffused layer 5 (by the solid line area surrounded) that uses as anode region.And on oval-shaped linearity region L and curve regions R, that surrounds p type diffused layer 5 forms a ring-type with p type diffused layer 9 (by the chain-dotted line area surrounded) on every side.As mentioned above, p type diffused layer 9 is concentrated Schottky barrier and is relaxed with the electric field on the end 20 (with reference to Fig. 1) of metal level 14 (with reference to Fig. 1), improve the voltage endurance of protection diode 1.
On oval-shaped linearity region L and curve regions R, that surrounds p type diffused layer 9 forms a ring-type with p type diffused layer 10 (by the chain-dotted line area surrounded), 11 (by the double dot dash line area surrounded) on every side.As mentioned above, p type diffused layer 10,11 uses as the diffusion layer of floating.
On oval-shaped linearity region L and curve regions R, the n type diffused layer 7 (by three chain-dotted line area surrounded) that will be used as cathode zone on every side that surrounds p type diffused layer 10 forms a ring-type.And on the zone that is formed with n type diffused layer 7, overlapping its forms the zone and one is formed with p type diffused layer 12 (by four chain-dotted line area surrounded) annularly.In addition, though do not illustrate, on p type diffused layer 5, overlapping its forms the zone and is formed with p type diffused layer 6 (with reference to Fig. 1).And on n type diffused layer 7, overlapping its forms and is formed with n type diffused layer 8 (with reference to Fig. 1) and p type diffused layer 13 (with reference to Fig. 1) regionally.
By this structure, protection diode 1 can pass through electric current in oval-shaped linearity region L and curve regions R, improve current capacity.In addition, in oval-shaped curve regions R, according to its curve shape and p type diffused layer 9, electric field is concentrated and is obtained relaxing, and can improve the voltage endurance of protection diode 1.By protecting diode 1 to form ellipse, can dwindle component size.
As shown in the figure, offer to the part of p type diffused layer 9 from p type diffused layer 5 and be formed with contact hole 22 (with reference to Fig. 1).Via contact hole 22, Schottky barrier is connected with p type diffused layer 5, N type epitaxial loayer 3 (with reference to Fig. 1) and p type diffused layer 9 with metal level 14.As mentioned above, Schottky barrier is formed directly into above the epitaxial loayer 3 (with reference to Fig. 1) with metal level 14.And Schottky barrier forms with the state of keeping flatness with the wide zone of metal level 14 in contact hole 22.By this structure, can Schottky barrier with metal level 14 just above the contact hole 23 that is connected with metal level 14 of formation metal level 18 and Schottky barrier.That is, on the contact hole 22 of Schottky barrier, be formed with contact hole 23 with metal level 14 usefulness.Its result, can suppress cloth alignment Schottky barrier with metal level 14 draw around, can dwindle the wiring pattern area.In addition, in the explanation of Fig. 8,, use same symbol to the structural element identical with structural element shown in Figure 1.And, this same-sign of expression in the bracket in Fig. 8.
At last, at oval-shaped curve regions R, in the below of the wiring layer that has applied anode potential (not shown), applied the wiring layer and the zone that n type diffused layer 7 intersects of anode potential at least, dispose electric field barrier film 51.Electric field barrier film 51 is for example by forming with the common operation of the operation of the gate electrode that forms MOS transistor (not shown), and formed by polysilicon film.And via the contact hole on the insulating barrier that is formed between epitaxial loayer 3 and the electric field barrier film 51 52,53, electric field barrier film 51 is connected with diffusion layer as cathode zone.That is, on electric field barrier film 51, be applied with identical with cathode potential in fact current potential.By this structure, electric field barrier film 51 has shield effectiveness for the wiring layer that has applied anode potential.And, can prevent owing to the potential difference between cathode potential and the anode potential makes cathode zone counter-rotating, and anode region and area of isolation 19 (with reference to Fig. 1) situation about being short-circuited.
In the present embodiment, the situation that forms silicide layer 21 between the p type diffused layer 5 that uses as anode region and the p type diffused layer 9 is illustrated.According to this structure, spread deeplyer by p type diffused layer 5 than p type diffused layer 9, the bottom surface of p type diffused layer 5 is left much to vertical direction from epitaxial loayer 3 surfaces.And, from the depletion layer of the boundary expansion of p type diffused layer 5 and epitaxial loayer 3 wide zone broadening to horizontal direction.Its result can strengthen the distance of leaving of p type diffused layer 5 and p type diffused layer 7, enlarges the formation zone of silicide layer 21.As a result, can not increase the p type diffused layer that is connected with anode electrode, improve the current capacity on the Schottky barrier diode.In addition,, can suppress the increase of parasitic capacitance, prevent the deterioration of high frequency characteristics by suppressing the increase in PN junction zone.But the invention is not restricted to this.In order to improve forward voltage (Vf) characteristic of the Schottky barrier diode in the protection diode,, silicide layer 21 is formed on the wide zone widening between p type diffused layer 5 and the p type diffused layer 9.And, also can be between p type diffused layer 5 and p type diffused layer 9, apply the p type diffused layer of anode potential again with certain intervals configuration roughly.At this moment,, reduce the curvature changing that silicide layer 21 forms the depletion layer on the zone, can keep the voltage endurance of protection diode by a plurality of p type diffusion regions territory.In addition, in the scope that does not break away from the object of the invention, can carry out various changes.
Claims (8)
1. a semiconductor device is characterized in that, comprising:
First and second anode diffusion layer of opposite conductivity type, it is separated on the semiconductor layer of a conduction type and forms;
The cathode diffusion layer of one conduction type, it is formed on the described semiconductor layer;
Insulating barrier, it is formed on above the described semiconductor layer;
Anode electrode, it is connected with described first and second anode diffusion layer via the contact hole that is formed on the described insulating barrier, and engages with described semiconductor layer Schottky between described first anode diffusion layer and the second plate diffusion layer;
The third anode diffusion layer of opposite conductivity type, its on the described semiconductor layer between described second plate diffusion layer and the described cathode diffusion layer via described insulating barrier and described anode electrode or be connected the metal level capacitive coupling of described anode electrode.
2. semiconductor device as claimed in claim 1 is characterized in that, disposes above the described second plate diffusion layer of described semiconductor layer by offering the end of the described anode electrode that described contact hole forms.
3. semiconductor device as claimed in claim 1 is characterized in that, described third anode diffusion layer is formed by the diffusion layer of two kinds of different opposite conductivity type of impurity concentration at least.
4. semiconductor device as claimed in claim 3 is characterized in that, the diffusion layer of the described opposite conductivity type that the diffusion layer of the described opposite conductivity type that impurity concentration is low is higher than impurity concentration more extends to described cathode diffusion layer side.
5. semiconductor device as claimed in claim 1 is characterized in that, overlaps to form the discharge diffusion layer of opposite conductivity type on described cathode diffusion layer, and is connected with cathode electrode in the discharge of described opposite conductivity type on diffusion layer.
6. semiconductor device as claimed in claim 1 is characterized in that, described second plate diffusion layer surrounds described first anode diffusion layer and is configured on every side, and described first anode diffusion layer diffuses to more deep than described second plate diffusion layer.
7. semiconductor device as claimed in claim 1 is characterized in that, disposes above described anode electrode to described anode electrode and applies the contact hole that the wiring layer of anode potential is used.
8. semiconductor device as claimed in claim 7, it is characterized in that, dispose on the described semiconductor layer below the wiring layer that has applied described anode potential and the idiostatic electric field barrier film of described cathode diffusion layer, described electric field barrier film is configured on the zone that the wiring layer that applied described anode potential and described cathode diffusion layer intersect.
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| JP2005098964 | 2005-03-30 | ||
| JP098964/05 | 2005-03-30 | ||
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN103681787A (en) * | 2012-09-20 | 2014-03-26 | 英飞凌科技股份有限公司 | Chip edge sealing |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS62165978A (en) * | 1986-01-17 | 1987-07-22 | Sanyo Electric Co Ltd | Protective diode |
| FR2803103B1 (en) * | 1999-12-24 | 2003-08-29 | St Microelectronics Sa | SCHOTTKY DIODE ON SILICON CARBIDE SUBSTRATE |
| JP3749191B2 (en) * | 2001-03-22 | 2006-02-22 | 松下電器産業株式会社 | High voltage semiconductor device |
| JP4477309B2 (en) * | 2003-05-09 | 2010-06-09 | Ｎｅｃエレクトロニクス株式会社 | High breakdown voltage semiconductor device and manufacturing method thereof |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103681787A (en) * | 2012-09-20 | 2014-03-26 | 英飞凌科技股份有限公司 | Chip edge sealing |
| CN103681787B (en) * | 2012-09-20 | 2016-08-17 | 英飞凌科技股份有限公司 | There is the semiconductor device that chip edge seals |
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