CN209016068U - Based on a kind of silicon drifting detector (SDD) for controlling surface field - Google Patents
Based on a kind of silicon drifting detector (SDD) for controlling surface field Download PDFInfo
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Abstract
The utility model discloses a kind of based on a kind of silicon drifting detector (SDD) for controlling surface field, including sequentially connected front surface electrode, cylindrical n-type silicon main body and rear surface electrode；Front surface electrode includes internal the first p+ type round screw thread cathode loop for being successively nested with closing cathode circle starting point ring, inner sealing cathodic protection ring and n+ type circular anode；The first closing cathode circle terminal ring and the first outer closure cathodic protection ring are successively socketed with outside first p+ type round screw thread cathode loop last ring；The width for closing cathode circle starting point ring, inner sealing cathodic protection ring, the first closing cathode circle terminal ring, the first outer closure cathodic protection ring and the first every ring of p+ type round screw thread cathode loop is equal；Rear surface electrode includes the 2nd p+ type round screw thread cathode loop of the embedded circular cathode to connect with its first ring, and the 2nd p+ type round screw thread cathode loop last ring is successively socketed with the second closing cathode circle terminal ring and the second outer closure cathodic protection ring outside.
Description
Technical field
The utility model belongs to pulsar X-ray detection and establishes navigation system large database concept technical field, especially relates to
And a kind of reach the big of best drift field and minimum surface current based on control surface field and silica/silicon interface area
The two-sided silicon drifting detector (SDD) in the gaps such as area cylindrical helical.
Background technique
From the sixties in last century, semiconductor detector comes out and is applied to core X-ray detection X, has up to the present sent out
Several generations is opened up, performance is continuously improved, and common semiconductor detector includes: Au Si surface barrier detector, lithium drifted detector Si
(Li), Si-PIN photodiode detector, silicon drifting detector (SDD) (SDD).The working principle of silicon drifting detector (SDD) (SDD) is,
It is made by substrate of N-type high resistance silicon wafer, is injected separately into P+ type sheath, shape in the plane of incidence of N-type silicon chip (substrate) and the back side
At P-N junction, when applying reverse bias voltage, complete depletion type semiconductor regions are formed, at this moment incident X-rays generation can be detected
Hole and electronics pair intrinsic region, more sub (electronics) that X-ray generates reach anode by drift potential paddy, to find out X
Ray.
Silicon drifting detector (SDD) (SDD) is the core in Xray fluorescence spectrometer, and the quality of performance, which directly affects, is
The working efficiency of system, good detector have good energy resolution and high counting properties.Leakage current is silicon drift detection
The main source of the noise of device, it directly affects energy resolution quality and sensitivity height；The cathode loop of silicon drifting detector (SDD)
After distance is more and more wider, larger dead zone will form, break electronics drift channel between adjacent two ring, so that electronics cannot float
It moves on to anode and is collected, therefore SDD detector cannot work normally again, so that SDD detector dies.
The silicon drifting detector (SDD) based on a kind of control surface field of the utility model, to the ultrapure High Resistivity Si material silicon of exploration
Drifting detector (Silicon Drift Detector, SDD) carrier drift Behavior law, heavy doping electrode growth rule,
Photoelectromagnetic Heat transmission and coupling mechanism, complexity in large-scale SDD detector array physical structure bearing mechanism, electronics read-out system
Background noise characteristic and seeker ground verification experimental verification platform construction principle of irradiation space environment etc. are of great significance.
Utility model content
The purpose of the utility model is to provide a kind of based on a kind of silicon drifting detector (SDD) for controlling surface field, SDD tool
Standby best drift field and minimum surface current, leakage current and the dead zone for overcoming existing SDD are excessive, drift field is bad, very
To the obstructed influence to SDD resolution ratio and sensitivity of drift field.
The utility model the technical scheme adopted is that based on it is a kind of control surface field silicon drifting detector (SDD), including
Front surface electrode, front surface electrode connect with a bottom surface of cylindrical n-type silicon main body；Cylindrical n-type silicon main body another
Bottom surface connects with rear surface electrode；
The front surface electrode includes the first p+ type round screw thread cathode loop, and the first p+ type round screw thread cathode loop is nested with
There is circular anode；
The rear surface electrode includes the 2nd p+ type round screw thread cathode loop, and the 2nd p+ type round screw thread cathode loop is embedded with
The circular cathode to connect with its first ring.
Further, closing cathode circle is successively nested between the first p+ type round screw thread cathode loop and circular anode
Shape starting point ring and inner sealing cathodic protection ring；The is successively socketed with outside last ring of the first p+ type round screw thread cathode loop
One closing cathode circle terminal ring and the first outer closure cathodic protection ring.
Further, the second closing cathode circle is successively socketed with outside last ring of the 2nd p+ type round screw thread cathode loop
Shape terminal ring and the second outer closure cathodic protection ring；The second P+ type round screw thread cathode loop and the first P+ type round screw thread yin
The ion implanting depth of polar ring, resistivity, square resistance, the first ring radius, last ring radius, adjacent two czermak space are homogeneous
Deng；Spiral ring width of the spiral ring width of the second P+ type round screw thread cathode loop less than the first P+ type round screw thread cathode loop
Degree.
Further, the closing cathode circle starting point ring, inner sealing cathodic protection ring, the first closing cathode circle terminal
The width of ring, the first outer closure cathodic protection ring and the first every ring of p+ type round screw thread cathode loop is equal；The closing cathode circle
The gap of shape starting point ring and inner sealing cathodic protection ring, inner sealing cathodic protection ring and the first p+ type round screw thread cathode loop first
The gap of ring, the gap of the first p+ last ring of type round screw thread cathode loop and the first closing cathode circle terminal ring, the first envelope
Closing the gap of cathode circle terminal ring and the first outer closure cathodic protection ring, to be equal to the first p+ type round screw thread cathode loop adjacent
The gap of two rings.
Further, the second closing cathode circle terminal ring, the second outer closure cathodic protection ring and the 2nd p+ type circle
The width of the every ring of shape spiral cathode ring is equal；Described 2nd p+ last ring of type round screw thread cathode loop and the second closing cathode circle
The gap in the gap of shape terminal ring, the second closing cathode circle terminal ring and the second outer closure cathodic protection ring is equal to the 2nd p
The gap of adjacent two ring of+type round screw thread cathode loop.
The beneficial effects of the utility model are: being had two-sided based on a kind of silicon drifting detector (SDD) for controlling surface field
Spiral cathode ring, and each every ring width of spiral cathode ring is equal, adjacent two ring effectively reduce SDD surface current apart from constant；
Setting closing cathode circle starting point ring and inner sealing cathode between the first p+ type round screw thread cathode loop and n+ type circular anode
Protection ring, between the first p+ type round screw thread cathode loop and the 2nd p+ last ring of type round screw thread cathode loop and the boundary SDD
Outer closure cathode circle terminal ring and outer closure cathodic protection ring are set, electric field breakdown is effectively prevent, obtains minimum leakage current,
Even distributed electric field, protection SDD.Leakage current and the dead zone for overcoming existing SDD are excessive, drift field is bad or even drift field
The obstructed influence to SDD resolution ratio and sensitivity, ensure that intensity 0.5~15keV grenz ray particle high-energy
It differentiates and efficiently collects.
Detailed description of the invention
In order to illustrate the embodiment of the utility model or the technical proposal in the existing technology more clearly, below will be to embodiment
Or attached drawing needed to be used in the description of the prior art is briefly described, it should be apparent that, the accompanying drawings in the following description is only
It is some embodiments of the utility model, for those of ordinary skill in the art, in the premise not made the creative labor
Under, it is also possible to obtain other drawings based on these drawings.
Fig. 1 is the structure principle chart of the utility model SDD；
Fig. 2 is the front surface round screw thread cathode loop schematic diagram of the utility model SDD；
Fig. 3 is the front surface round screw thread cathode loop center enlarged diagram of the utility model SDD；
Fig. 4 is that n+ type circular anode electrode, inner sealing yin is added in the front surface round screw thread cathode loop of the utility model SDD
The schematic diagram of pole protection ring and closing cathode circle starting point ring；
Fig. 5 is that n+ type circular anode electrode, inner sealing yin is added in the front surface round screw thread cathode loop of the utility model SDD
The center enlarged diagram of pole protection ring and closing cathode circle starting point ring；
Fig. 6 is the front surface round screw thread cathode ring size definition figure of the utility model SDD；
Fig. 7 is that closing cathode circle terminal ring schematic diagram is added in the front surface round screw thread cathode loop of the utility model SDD；
Fig. 8 is that outer closure cathodic protection ring schematic diagram is added in the front surface round screw thread cathode loop of the utility model SDD；
Fig. 9 is the back side round screw thread cathode loop schematic diagram of the utility model SDD；
Figure 10 is the back side round screw thread cathode loop center enlarged diagram of the utility model SDD；
Figure 11 is that closing cathode circle terminal ring schematic diagram is added in the back side round screw thread cathode loop of the utility model SDD；
Figure 12 is that outer closure cathodic protection ring schematic diagram is added in the back side round screw thread cathode loop of the utility model SDD；
Figure 13 is the utility model SDD three-dimensional simulation distribution map of the electric field；
(leakage current of detector is in Naan for the leakage current and the I-V schematic diagram of bias voltage that Figure 14 is the utility model SDD
(nA) grade)；
(output capacitance of detector flies the anode capacitance and the C-V schematic diagram of bias voltage that Figure 15 is the utility model SDD
Method (fF) grade).
In figure, 1. front surface electrodes, the first p+ type round screw thread cathode loop of 1-1., 1-2.n+ type circular anode, 1-3. envelope
Cathode circle starting point ring, 1-4. inner sealing cathodic protection ring are closed, 1-5. first closes cathode circle terminal ring, the first covering of 1-6.
Close cathodic protection ring, 2.n type silicon main body, 3. rear surface electrodes, the 2nd p+ type round screw thread cathode loop of 3-1., the round yin of 3-2.
Pole, 3-3. second close cathode circle terminal ring, 3-4. the second outer closure cathodic protection ring.
Specific embodiment
The following will be combined with the drawings in the embodiments of the present invention, carries out the technical scheme in the embodiment of the utility model
Clearly and completely describe, it is clear that the described embodiments are only a part of the embodiments of the utility model, rather than whole
Embodiment.Based on the embodiments of the present invention, those of ordinary skill in the art are without making creative work
Every other embodiment obtained, fall within the protection scope of the utility model.
Based on a kind of silicon drifting detector (SDD) for controlling surface field, as shown in Figure 1, by front surface electrode 1, cylinder n type
Silicon main body 2 and rear surface electrode 3 form；Front surface electrode 1 connects with a bottom surface of cylindrical n-type silicon main body 2；Rear surface electricity
Pole 3 connects with another bottom surface of cylindrical n-type silicon main body 2；
As shown in Fig. 2~Fig. 5, front surface electrode 1 includes the first p+ type round screw thread cathode loop 1-1, and the first p+ type is round
The first ring of spiral cathode ring 1-1 is embedded to be cased with closing cathode circle starting point ring 1-3；It is embedded to close cathode circle starting point ring 1-3
It is cased with inner sealing cathodic protection ring 1-4；Inner sealing cathodic protection ring 1-4 is embedded to be cased with n+ type circular anode 1-2；Such as Fig. 7 and figure
Shown in 8, last ring of the first p+ type round screw thread cathode loop 1-1 is externally provided with the first closing cathode circle terminal ring 1-5, and first
Closing cathode circle terminal ring 1-5 is externally provided with the first outer closure cathodic protection ring 1-6.Close cathode circle starting point ring 1-3, interior envelope
The width for closing cathodic protection ring 1-4 and the first p+ type round screw thread cathode loop the first ring of 1-1 is equal, and inner sealing cathodic protection ring
In 1-4, closing cathode circle starting point ring 1-3 and the first p+ type round screw thread cathode loop 1-1 the first ring three between adjacent the two
Gap is equal to the gap of adjacent two ring of the first p+ type round screw thread cathode loop 1-1；First closing cathode circle terminal ring 1-5, first
The width of outer closure cathodic protection ring 1-6 and the first p+ type round screw thread cathode loop 1-1 last ring is equal, and the first closing yin
Polar circle shape terminal ring 1-5, the first outer closure cathodic protection ring 1-6 and the first p+ type round screw thread cathode loop 1-1 last ring three
Both adjacent gap is equal to the gap of adjacent two ring of the first p+ type round screw thread cathode loop 1-1 in person；
As shown in figs. 9 to 12, rear surface electrode includes the 2nd p+ type round screw thread cathode loop 3-1, and the 2nd p+ type is round
Spiral cathode ring the first ring of 3-1 is embedded with circular cathode 3-2, circular cathode 3-2 and the 2nd p+ type round screw thread cathode loop 3-1
First ring connects；2nd p+ type round screw thread cathode loop 3-1 last ring is externally provided with the second closing cathode circle terminal ring 3-3,
Second closing cathode circle terminal ring 3-3 is externally provided with the second outer closure cathodic protection ring 3-4.Second closing cathode circle terminal ring
The width of 3-3, the second outer closure cathodic protection ring 3-4 and the 2nd p+ type round screw thread cathode loop 3-1 last ring is equal, and
Two closing cathode circle terminal ring 3-3, the second outer closure cathodic protection ring 3-4 and the 2nd p+ type round screw thread cathode loop 3-1 are most
Both adjacent gap is equal to the gap of adjacent two ring of the 2nd p+ type round screw thread cathode loop 3-1 in latter ring three.
It closes cathode circle starting point ring 1-3, the first closing cathode circle terminal ring 1-5 and the second closing cathode is round eventually
The effect of point ring 3-3 is that two of the first p+ type round screw thread cathode loop 1-1 and the 2nd p+ type round screw thread cathode loop 3-1 are opened
Mouth is closed, and is guaranteed the terminal of the first p+ type round screw thread cathode loop 1-1 and the 2nd p+ type round screw thread cathode loop 3-1 and is risen
Point place potential and electric field distributing homogeneity, will not because of geometry fracture and cause potential electric field distribution unexpected change
Change, while also making the overall structure of the first p+ type round screw thread cathode loop 1-1 and the 2nd p+ type round screw thread cathode loop 3-1 beautiful
Symmetrically.
In practical applications, the number of the first outer closure cathodic protection ring 1-6 and the second outer closure cathodic protection ring 3-4 can
To determine according to specific actual needs, the consistent first outer closure yin of a certain number of width and gap appropriate can be set
Pole protection ring 1-6 and the second outer closure cathodic protection ring 3-4.The purpose of the setting of front surface electrode 1 inner sealing cathodic protection ring 1-4
It is the one effective electric field buffer area of increase between the first p+ type round screw thread cathode loop 1-1 and n+ type circular anode 1-2, prevents
The only electric field breakdown between the first p+ type round screw thread cathode loop 1-1 and n+ type circular anode 1-2.First outer closure cathode is set
The purpose of protection ring 1-6 and the second outer closure cathodic protection ring 3-4 are, in the first p+ type round screw thread cathode loop 1-1 and the 2nd p
Increase an effective electric field buffer area between+type last ring of round screw thread cathode loop 3-1 and the boundary SDD, prevents the first p+
Electric field between type round screw thread cathode loop 1-1 and the 2nd p+ type last ring of round screw thread cathode loop 3-1 and the boundary SDD is hit
It wears, which would generally cause high leakage current, and therefore SDD cannot can be worked normally again, so that SDD dies.In addition,
First closing cathode circle terminal ring 1-5 and the second additional multiple first outer closure cathodes of closing cathode circle terminal ring 3-3 are protected
The purpose of retaining ring 1-6 and the second outer closure cathodic protection ring 3-4 are to be electrically isolating the first p+ type round screw thread cathode loop 1-
1 and the 2nd p+ type round screw thread cathode loop 3-1, and what voltage is not taken over, play the role of being uniformly distributed electric field, protection SDD.
The key of SDD design is how to design the cathode loop of upper and lower surface to provide the best drift channel of an electronics and drift
Move electric field.Based on a kind of design method of silicon drifting detector (SDD) (SDD) for controlling surface field, the first p+ type round screw thread is kept
Cathode loop 1-1 and the 2nd p+ type every ring of round screw thread cathode loop 3-1 keep the oxidation silicon area between cathode loop minimum apart from constant
Change, to reduce surface current, achieve the purpose that minimum leakage current, and dead zone area can be made minimum.
Based on a kind of design method of silicon drifting detector (SDD) for controlling surface field, specifically comprise the following steps:
Step S1, according to front surface electrode 1 the first P+ type round screw thread cathode loop 1-1 radial r point resistance value, really
The voltage's distribiuting of fixed first P+ type round screw thread cathode loop 1-1:
The voltage's distribiuting of SDD front surface electrode 1 is provided by the first P+ type spiral cathode ring 1-1 of heavy doping, first
P+ type spiral cathode ring 1-1 is formed by ion implanting；As shown in fig. 6, the first P+ type round screw thread cathode loop 1-1 exists
The width of radial r point is W (r), i.e. W (r) defines width of the helical ring in radial r point of the first P+ type round screw thread cathode loop 1-1
Degree；P (r) is spacing of the first P+ type round screw thread cathode loop 1-1 adjoining spiral ring in radial r point, and G (r) is the first P+ type circle
Shape spiral cathode ring 1-1 adjoining spiral ring can obtain in the gap of radial r point from Fig. 6:
P (r)=W (r)+G (r)；Formula (2)
Calculate resistance value R (r) of the helical ring in radial r point of the first P+ type round screw thread cathode loop 1-1:
Wherein, t is the ion implanting depth of the first P+ type round screw thread cathode loop 1-1, t not with the variation of radial r point and
Variation；ρ is the resistivity of the first P+ type round screw thread cathode loop 1-1 (ion implanted regions)；L is the first P+ type round screw thread yin
Perimeter of the polar ring 1-1 in radial r point；ρsFor the square resistance of the first P+ type round screw thread cathode loop 1-1 ion implanted regions；
The first P+ type round screw thread cathode loop 1-1 is defined in the helical ring perimeter of radial r point are as follows:
L=α r；Formula (4)
Wherein, r refers in particular to the first P+ type round screw thread cathode loop (1-1) in the helical ring radius of radial r point；α is the first P+
Type round screw thread cathode loop 1-1 radial r point helical ring perimeter coefficient, by the several of the first P+ type round screw thread cathode loop 1-1
What shape determines, for circular spiral cathode ring, in perimeter L=2 π r of radial r point, therefore the π of α=2；Similarly, for pros
The helical ring cathode of shape,For regular hexagon, L=6r, α=6；The spiral shell of the utility model front surface
Revolving cathode loop is circle, therefore the π of α=2；
The spiral cathode ring of the utility model front surface electrode 1 is provided in round, and is because of round detector current voltage
Distribution is most uniform.Since detector is that cylindrical geometric is symmetrical, internal electric field Potential Distributing not with rotation angle change and
Variation, is the best structure and most basic structure of detector cells, and square and hexagonal structure deviate from cylindrical
It is geometrically symmetric, thus caused by asymmetry potential electric field distribution inside detector can be made to become with the variation of rotation angle
Change, so that design is also more complicated.
It calculates in radial r point, the voltage difference △ V (r) of the first P+ type round screw thread cathode loop 1-1 adjoining spiral ring:
Δ V (r)=IR (r)=E (r) P (r)；Formula (1)
Wherein I is the electric current in the first P+ type round screw thread cathode loop 1-1, in the actual design and operation of spiral cathode ring
In, the electric current I inside spiral cathode ring is one in advance by design specified value, and the electric current given in the utility model is 50 μ
A；E (r) is surface field of the first P+ type round screw thread cathode loop 1-1 in radial r point；
Step S2, it keeps adjacent two czermak space of the first P+ type round screw thread cathode loop (1-1) constant, determines the preceding table of SDD
The width distribution of face the first P+ type round screw thread cathode loop 1-1:
The geometry of first P+ type round screw thread cathode loop 1-1 and formula (1)~formula (4) are combined:
ρsα rI=P (r) E (r) W (r)；Formula (6)
For the first P+ type round screw thread cathode loop 1-1 of SDD detector front surface, the every czermak space of its helical ring is kept not
Become, that is, keeping adjacent injection zone in the clearance G (r) of radial r point is constant G, this pattern (2) becomes:
P (r)=W (r)+G；Formula (7)
Usual G value in the first ring width half to the first ring width, i.e. 0.5W1≤G≤W1；W1For the first P+ type circle
The width of every ring of shape spiral cathode ring 1-1, W1Usually tens microns to 100 microns；W1Value to guarantee the value of G not
Less than 5 microns, it is not more than 100 microns.In the limiting case, the minimum value of P is 10 microns, therefore the minimum value of W (r) is 5 micro-
Rice.
The design method for generally yielding minimum leakage current and best surface electric field in the past is that P (r) is with radial r point
Increase and increase, and G (r) is again directly proportional to P (r), so G (r) is also increased with the increase of r.G (r) is by not having
There is the SiO of injection2Constitute, so, there is surface state as caused by defect in it, surface state number with the surface area of G (r)
Directly proportional, surface state can cause tracking current, so the surface area of G (r) is bigger, the leakage current on surface is bigger, so that
The leakage current of SDD is bigger.So the numerical value of r is bigger when designing large area SDD before, the contribution of tracking current can be brighter
It is aobvious, therefore, to reduce the bigger phenomenon of surface area numerical value as caused by G (r) in the case where the numerical value of r is bigger to the greatest extent.It
In preceding common design, the size of G (r) is usually that more than ten μm of increase of several circles (near r=200 μm) by is several to the end
Circle is greater than 500 μm.And in the utility model design, it keeps the numerical value in the entire gap SDD constant, is only minimized more than ten of μ
M can thus be significantly reduced the surface area as caused by G (r), to reduce tracking current.The design is relative to biography
There is innovation and advantage in system design, but since gap and spacing are not proportional relations, it can be more complicated in calculating and design.
Convolution (6) and formula (7) rewrite formula (5) are as follows:
Whether the first P+ type round screw thread cathode loop 1-1 can depending on it surely in the taking for surface field E (r) of radial r point
The distribution of optimized electronic drift field is provided, and a simple easy analytic solutions can be obtained in integral calculation later,
The form of E (r) can be any given by designer；
By formula (8) can obtain the first P+ type round screw thread cathode loop 1-1 radial r point adjoining spiral interannular away from P (r) are as follows:
Step S3, the rotation angle and radial direction r point of the first P+ type round screw thread cathode loop 1-1 of front surface electrode 1 are calculated
Relationship:
Defining θ is rotation angle of the first P+ type of front surface round screw thread cathode loop 1-1 in radial r point, calculates θ and radial direction
The relationship of r point are as follows:
Wherein, r1It is the radius of front surface the first P+ type round screw thread cathode loop the first ring of 1-1；
Formula (9) are substituted into formula (12), can obtain the rotation angle of front surface the first P+ type round screw thread cathode loop 1-1 with
The relationship θ (r) of radial r point, typically, since P (r) is more complicated, formula (12) can not calculate the parsing relationship θ of θ and r
(r), numerical approximation can only be done；But when E (r) takes certain special functional forms, formula (12) can provide θ and radial direction r point
Parsing relationship；Taking E (r) and radial direction r point relationship is linear relationship:
Wherein, R is the radius of last ring of front surface the first P+ type round screw thread cathode loop 1-1；VE1It is front surface first
The voltage of P+ type round screw thread cathode loop the first ring of 1-1, VoutBe front surface the first P+ type round screw thread cathode loop 1-1 last
The voltage of ring；VE1Value between 0~10V, VoutValue between 100~400V.
In this case, the first P+ type of front surface round screw thread cathode loop 1-1 is in the potential of radial r point:
Φ(r1)=VE1, Φ (R)=Vout；
In this case by formula (5) and formula (9) it can be concluded that front surface the first P+ type round screw thread cathode loop 1-1 is in diameter
Spacing P (r) to r point adjoining spiral ring is unrelated with radial r point, and the spacing is constant P, and the value of P is generally at tens microns
To between 200 microns, the minimum value of P by the attainable minimum dimension of chip technology and the required most great circle number of application Lai
It determines, in practical applications, the minimum value of P is generally in 10 microns, and the maximum value of P generally limits less, but it is necessary
It is more much smaller than outmost turns radius R, to guarantee that cathode loop has two circles or more:
At this point, width W (r) of the helical ring of the first P+ type round screw thread cathode loop 1-1 of front surface in any radial direction r point
It is also constant:
W (r)=P-G；Formula (11)
By formula (10) and formula (12) it can be concluded that the rotation of corresponding front surface the first P+ type round screw thread cathode loop 1-1
The relationship θ (r) of gyration and radial direction r point are as follows:
Radial r point and the rotation angle of the first P+ type of front surface round screw thread cathode loop 1-1 can be solved by formula (16)
Relationship are as follows:
Step S4, the drift path i.e. drift field of the second P+ type round screw thread cathode loop 3-1 of rear surface electrode is determined
Second P+ type round screw thread cathode loop 3-1 is in the potential of radial r point:
Ψ (r)=VB+ γ Φ (r) (0 < γ < 1)；Formula (18)
Wherein, γ is ratio tune of the first P+ type of front surface round screw thread cathode loop 1-1 in the potential Φ (r) of radial r point
Parameter is saved, value is generally 0.1~0.4；VBIt is second P+ type round screw thread cathode loop the first ring of 3-1 of rear surface electrode
Voltage；
VBValue be usually SDD total depletion voltage Vfd, it may be assumed that
Wherein, e is elementary charge amount, e=1.602 × 10-19Coulomb, NdIt is the second P+ type round screw thread yin of rear surface
The doping concentration of polar ring 3-1, d are the thickness of SDD, and ε is dielectric constant, ε0It is permittivity of vacuum；VBGeneral value is in 60-
Between 120V.
Drift field E in SDD detector electronics drift channeldrIt is:
Or
E (r) is determined by formula (5), and Φ (r) is determined by formula (17)；Point that formula (15) and (16) pass through surface field
Cloth calculates electric field of the electronics inside the SDD on drift channel, i.e. electronics drift field.This electronics drift field directly determines
The speed of SDD electronics drift and the orientation of drift orbit, therefore be important step of SDD drift orbit optimization.
Step S5, the design of the second P+ type round screw thread cathode loop 3-1 of SDD detector rear surface electrode is determined
Convolution (13) and formula (18) obtain the second P+ type of rear surface round screw thread cathode loop 3-1 in the potential of radial r point:
Electric field E of the second P+ type round screw thread cathode loop 3-1 of rear surface in radial r pointB(r) are as follows:
Wherein, r1BIt is round with the first P+ type of front surface for second P+ type round screw thread cathode loop 3-1 the first ring radius
Spiral cathode ring 1-1 the first ring radius is equal, i.e. r1 B=r1；RBFor second P+ type round screw thread cathode loop 3-1 last ring half
Diameter, i.e. R equal with first P+ type round screw thread cathode loop last ring radius of 1-1 of front surfaceB=R；Vout BFor the second P+ type
Last loop voltag of round screw thread cathode loop 3-1；VB outBy material, doping thickness and Vout、VE1Setting determine,
VB outValue generally between 0~300V.
The adjoining spiral interannular of rear surface the second P+ type round screw thread cathode loop 3-1 is set away from PBIt (r) is constant PB, adjacent
Spiral czermak space is constant GB, and GBIt is equal with front surface the first P+ type round screw thread cathode loop 1-1 adjoining spiral czermak space, i.e.,
GB=G, then:
Wherein, ρB sFor the square resistance of rear surface the second P+ type round screw thread cathode loop 3-1 ion implanted regions, αBAfter being
Surface the second P+ type round screw thread cathode loop 3-1 radial r point perimeter coefficient, and by the second P+ type round screw thread cathode loop
What the geometry of 3-1 determined, and αB=α.
Calculate the square resistance ρ of the second P+ type of rear surface round screw thread cathode loop 3-1 ion implanted regionsB s:
Wherein, ρB s=ρs, tBIt is the ion implanting depth of rear surface the second P+ type round screw thread cathode loop 3-1, tBNot with diameter
Change, t to the variation of r pointB=t；ρBIt is the electricity of rear surface the second P+ type round screw thread cathode loop 3-1 (ion implanted regions)
Resistance rate, ρB=ρ.
The spiral ring width W of rear surface the second P+ type round screw thread cathode loop 3-1BIt is also constant:
WB=PB-GB；Formula (23)
Corresponding the second P+ type of rear surface round screw thread cathode loop 3-1 rotates angle, θBChange with the variation of r,
Are as follows:
By formula (22) and formula (25) it can be concluded that the second P+ type of rear surface round screw thread cathode loop 3-1 radial r point spiral shell
It revolves ring and rotates angle are as follows:
In general, G can be takenB=kPB, wherein 0 < k < 1；In practical applications, 0.3≤k≤0.5 is generally taken, this is practical
Novel GB=G.
Step S6, closing yin is set gradually in the first p+ type round screw thread cathode loop the first ring of 1-1 of front surface electrode 1
Polar circle shape starting point ring 1-3, inner sealing cathodic protection ring 1-4 and n+ type circular anode 1-2；In the first p+ type round screw thread cathode loop
The first closing cathode circle terminal ring 1-5 and the first outer closure cathodic protection ring 1-6 are set gradually outside last ring of 1-1；And it sets
Set closing cathode circle starting point ring 1-3, inner sealing cathodic protection ring 1-4, the first closing cathode circle terminal ring 1-5 and first
The width of outer closure cathodic protection ring 1-6 is equal with the width of the first every ring of p+ type round screw thread cathode loop 1-1, closing cathode circle
The gap of shape starting point ring 1-3 and inner sealing cathodic protection ring 1-4, closing cathode circle starting point ring 1-3 and the first p+ type circle spiral shell
Gap, the first p+ type last ring of round screw thread cathode loop 1-1 and the first closing cathode for revolving the first ring of cathode loop 1-1 are round eventually
The gap of point ring 1-5, the gap of the first closing cathode circle terminal ring 1-5 and the first outer closure cathodic protection ring 1-6 and the first p
The gap of adjacent two ring of+type round screw thread cathode loop 1-1 is equal；
Step S7, in the 2nd p+ type round screw thread cathode loop 3-1 of front surface electrode 3, setting connects with its first ring
Circular cathode 3-2 sets gradually the second closing cathode circle terminal in the 2nd p+ type round screw thread cathode loop 3-1 outside last ring
Ring 3-3 and the second outer closure cathodic protection ring 3-4；And the second closing cathode circle terminal ring 3-3 and the second outer closure yin are set
Pole protection ring 3-4 width is equal with the width of the 2nd every ring of p+ type round screw thread cathode loop 3-1, the 2nd p+ type round screw thread cathode
The gap of last ring of ring 3-1 and the second closing cathode circle terminal ring 3-3, the second closing cathode circle terminal ring 3-3 and the
The gap of the gap of two outer closure cathodic protection ring 3-4, two ring adjacent with the 2nd p+ type round screw thread cathode loop 3-1 is equal.
In the utility model, design gaps are constant, and gap width G is oneself setting, between showing that spiral is changed according to formula (10)
Away from P, then according to formula W (r)=P-G, it can be deduced that the width W of helical ring, all due to the utility model intermediate gap and spacing
It is constant to be to maintain constant, so spiral ring width is also to keep constant constant, using gained radius r and rotates angle, θ
Relationship can directly obtain spiral ring structure.
It, can be very intuitively from seeing that drift channel is the figure among detector in Figure 13 due to reasonable optimization design
13 indicate three-dimensional coordinate, and wherein X-coordinate is radial direction, and Y-coordinate is thickness direction, and Z coordinate indicates the diameter in detector SDD
To with the three-dimensional electric field direction in plane defined in thickness direction.As can be seen that net distribution is electric field in detector
Three-dimensional distribution map can be clearly seen that a mountain valley, as shown by arrows in figure, and this mountain valley is real in field distribution
It is exactly electronics drift channel on border, this channel is fully located at the inside of detector, i.e., completely in the diagonal of the defined plane of XY
On line, and it is directed toward and collects anode.It being stated alternatively, the lines that arrow mark goes out are drift channel of the electronics in SDD, by
Figure 13 can be seen that channel represented by this line and be fully located on the diagonal line of X/Y plane, not intersect with X or Y, therefore,
Electronics drift channel is entirely located in inside detector, that is to say, that drift channel without departing from detector radial direction and
Thickness direction, while being directed toward collection anode, i.e. direction n+ type circular anode 1-2 can ensure that electronics can be received by anode in this way
Collection, without floating to the part other than anode；Bias voltage is added to can be seen that due to cathode by the cathode to tow sides
The effect of potential dividing ring, potential form gradient distribution in drift channel, form electric field by potential difference, electronics will be in the electric field
Anode is drifted under effect, is then collected by anode.Obvious potential electric field distribution is all the center to be parallel to Z axis by anode
Axisymmetric, such distribution is determined by the symmetrical structure of cylindrical detector.The symmetrical structure refers to, detector
Potential electric field be distributed, cylindrical distribution unrelated with θ, the central axis of cylinder is z-axis.Figure 13 illustrates the drift of the utility model silicon
The three-dimensional electric field of shift detector is distributed, since electric field is the differential of Potential Distributing, electronics drift channel can be more clear as it can be seen that
It is entirely inside detector and to be directed toward anode.Drift channel illustrates this by anode collection well among detector
The SDD of utility model has preferable drift field.
Figure 14 illustrates the relationship of the utility model silicon drifting detector (SDD) leakage current and bias voltage, be detector one most
Important parameter, the abscissa in figure is the bias voltage being added on SDD detector, its value is negative voltage, the vertical seat on the left side
Mark is to indicate anode leakage stream I1, it can be seen that for its value when bias voltage is equal to -100V, the leakage current of 3nA is very small
, the ordinate on the right indicates the leakage current I of the first cathode loop of front surface2With the leakage current I of the second cathode loop3, its value is negative
, indicating that we design is optimization, has reached the leakage current of very little.
Figure 15 illustrates the relationship of ready-made detector anode capacitance and bias voltage, it is another weight of detector
The parameter wanted, abscissa are the bias voltages being added on the first p+ type round screw thread cathode loop 1-1 of front surface, its value is negative
Value, ordinate is the capacitor of anode, it can be seen that with the increase of bias voltage, anode capacitance sharply declines, reach fF with
Under, the result of measurement probably in 650fF or so, has reached the local noise of system.Actual anode capacitance, according to calculating and mould
Quasi- result (dotted line indicates in figure) can also continue to decline with the increase of bias voltage, until 100 fF or so, substantially
It is to reach minimum value 100fF in total depletion voltage, that is, between 40-50V, this is also optimization design as a result, reaching super
Primary anode capacitor, extra small anode capacitance can provide extra small output electronics noise together, can also reach the energy point of superelevation in this way
Resolution.
The utility model reduces the surface area in gap by reducing gap width, to reach reduction tracking current
With reduce dead zone purpose, and because use circular symmetric structure, make internal electric field distribution do not change with the variation of angle, reach
The purpose for being uniformly distributed to drift field and being collected by anode, to realize optimal drift field.The design of the utility model
By reducing tracking current, drift field is preferably improved, to improve the performance of detector.Figure 15 is shown ultralow
Noise also illustrates that the utility model can reach high energy resolution well.
Due to respectively adding a voltage difference on the spiral cathode ring on two surfaces, so there is a transverse direction in the silicon body
Electric field forms electronics drift channel from the outermost fourth finger of spiral cathode ring of SDD to the circular collection anode electrode at center.Electronics
Drift to collection anode along drift channel in the effect of this electric field, generated charge (voltage) signal intensity and provide
SDD detectable signal.According to the relationship of charge-trapping and time, the initial signal of SDD is exactly all to being collected by no signal (0)
Charge and generate signal (1), this charge signal is converted into voltage signal in circuit, is then amplified, ultimately form SDD output
Signal.
The above is only the preferred embodiment of the utility model only, is not intended to limit the protection model of the utility model
It encloses.Any modification, equivalent substitution, improvement and etc. made within the spirit and principle of the present invention, are all contained in this reality
With in novel protection scope.
Claims (5)
1. based on a kind of silicon drifting detector (SDD) for controlling surface field, which is characterized in that including front surface electrode (1), front surface
Electrode (1) connects with a bottom surface of cylindrical n-type silicon main body (2)；Another bottom surface of n-type silicon main body (2) and rear surface
Electrode (3) connects；
The front surface electrode (1) includes the first p+ type round screw thread cathode loop (1-1), the first p+ type round screw thread cathode loop
(1-1) is embedded to be cased with n+ type circular anode (1-2)；
The rear surface electrode (3) includes the 2nd p+ type round screw thread cathode loop (3-1), the 2nd p+ type round screw thread cathode loop
(3-1) is embedded with the circular cathode (3-2) to connect with its first ring.
2. according to claim 1 based on a kind of silicon drifting detector (SDD) for controlling surface field, which is characterized in that described the
Closing cathode circle starting point ring is successively nested between one p+ type round screw thread cathode loop (1-1) and n+ type circular anode (1-2)
(1-3) and inner sealing cathodic protection ring (1-4)；
The first closing cathode circle terminal is successively socketed with outside last ring of the first p+ type round screw thread cathode loop (1-1)
Ring (1-5) and the first outer closure cathodic protection ring (1-6).
3. according to claim 1 based on a kind of silicon drifting detector (SDD) for controlling surface field, which is characterized in that described the
The second closing cathode circle terminal ring (3-3) and the are successively socketed with outside two p+ type round screw thread cathode loop (3-1) last ring
Two outer closure cathodic protection rings (3-4)；
The ion implanting of the second P+ type round screw thread cathode loop (3-1) and the first P+ type round screw thread cathode loop (1-1) is deep
Degree, resistivity, square resistance, the first ring radius, last ring radius, adjacent two czermak space are equal；
The spiral ring width of the second P+ type round screw thread cathode loop (3-1) is less than the first P+ type round screw thread cathode loop (1-
1) spiral ring width.
4. according to claim 2 based on a kind of silicon drifting detector (SDD) for controlling surface field, which is characterized in that the envelope
Close cathode circle starting point ring (1-3), inner sealing cathodic protection ring (1-4), the first closing cathode circle terminal ring (1-5), first
The width of outer closure cathodic protection ring (1-6) and the first p+ type round screw thread cathode loop (1-1) every ring is equal；
The gap of closing cathode circle starting point ring (1-3) and inner sealing cathodic protection ring (1-4), closing cathode circle starting point
The gap of ring (1-3) and the first p+ type round screw thread cathode loop (1-1) first ring, the first p+ type round screw thread cathode loop (1-1)
The gap of last ring and the first closing cathode circle terminal ring (1-5), the first closing cathode circle terminal ring (1-5) and first
The gap of outer closure cathodic protection ring (1-6) is equal to the gap of adjacent two ring of the first p+ type round screw thread cathode loop (1-1).
5. according to claim 3 based on a kind of silicon drifting detector (SDD) for controlling surface field, which is characterized in that described the
Two closings cathode circle terminal ring (3-3), the second outer closure cathodic protection ring (3-4) and the 2nd p+ type round screw thread cathode loop
The width of (3-1) every ring is equal；
Between described 2nd p+ type round screw thread cathode loop (3-1) last ring and the second closing cathode circle terminal ring (3-3)
The gap of gap, the second closing cathode circle terminal ring (3-3) and the second outer closure cathodic protection ring (3-4) is equal to the 2nd p+ type
The gap of adjacent two ring of round screw thread cathode loop (3-1).
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