Laser-drilled three-dimensional spherical electrode detector, design method and application

Abstract

The present invention belongs to the technical field of semiconductor detectors, and discloses a laser-drilled three-dimensional spherical electrode detector, a design method and an application. A groove is formed by multiple uniform drillings by a laser, and ion diffusion is used to dope in the groove to finally form a spherical electrode. An N-type heavily doped anode is doped in the middle of the upper end of an N-type lightly doped silicon substrate, and a plurality of P-type heavily doped upper surface rings are doped on the outer side of the N-type heavily doped anode and arranged at equal intervals; a P-type heavily doped cathode is arranged at the bottom of the N-type lightly doped silicon substrate, and the P-type heavily doped cathode is provided with a P-type heavily doped ring and a P-type heavily doped surface. In the present invention, the distance between the anode and the cathode is the same, so that the potential distribution in the detector is very uniform, and the charge collection rate of the new detector unit is improved; the design of the upper surface heavily doped ring makes the electric field distribution on the inner surface of the detector unit more uniform; according to the existing process, a spherical electrode can be realized by uniformly drilling holes with a laser and ion diffusion doping.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor detectors, and in particular relates to a laser-drilled three-dimensional spherical electrode detector, a design method and an application thereof. Background Art

[0002] At present, with the progress of society and the development of science and technology, the application of semiconductor materials has become an indispensable part of life, and detectors based on semiconductor materials have also emerged. Traditional detector technology is becoming more and more perfect. Among a large number of semiconductor detectors, silicon detectors are widely used in aerospace, astrophysics, high energy physics, nuclear medicine, national defense and other fields due to their superior performance and mature and advanced process technology.

[0003] Common types of silicon detectors include: silicon microstrip detectors, silicon strip pixel detectors, silicon drift chamber detectors, three-dimensional columnar electrode detectors, and three-dimensional trench electrode silicon detectors. With the evolution and development of various types of semiconductor detectors, from two-dimensional to three-dimensional, the structure and performance of detectors are gradually improving and improving.

[0004] Silicon detectors work under reverse bias. When photons or other high-energy particles with a certain energy are incident on the sensitive area of ​​the detector, the energy is transferred to the silicon-based atoms, causing the electrons in them to jump from the valence band to the conduction band, forming electron-hole pairs. Under the action of internal and external electric fields, electrons drift toward the anode and holes drift toward the cathode, and each is collected and processed by the corresponding electrode. At the same time, the electrical signal generated by the detector device is read out through external electronic equipment.

[0005] Any three-dimensional silicon detector device structure has its own unavoidable defects. For example, the traditional three-dimensional groove electrode silicon detector needs to ensure that the etched substrate does not fall off, and the groove electrode cannot completely penetrate the entire silicon substrate. It can only be etched to about 90% of the depth of the silicon substrate. Therefore, compared with the same size laser-drilled three-dimensional spherical electrode detector, the first defect of the traditional three-dimensional groove electrode silicon detector is the existence of a dead zone and the proportion is too large. The dead zone is a weak electric or zero electric field area. If the dead zone occupies a large proportion of the detector substrate, it will lead to poor electrical properties of the detector, such as uneven distribution of potential or electric field, and the charge collection efficiency will also be affected. When the three-dimensional groove detector is processed and manufactured, due to process technology reasons, the substrate cannot be completely etched to the bottom, that is, a certain thickness will be retained on the detector substrate as a substrate to stabilize the mechanical stability of the detector structure unit or array, so as not to cause the substrate to fall off due to etching. The substrate here is a weak electric or zero electric field area. When the detector device is working, this area cannot work normally, so this part of the substrate forms a dead zone.

[0006] Secondly, the traditional three-dimensional groove electrode detector has different electrode spacing, which is also an important reason for the reduction of charge collection rate. The charge collection rate is different for different positions and angles of heavy ion incidence. For example, when incident from the position with the largest electrode spacing, the electric field is the lowest, so it has the greatest charge capture effect on drifting electrons-holes, so the charge collection rate here is the lowest. If incident at the position with the smallest electrode spacing, the charge collection rate is the highest. The difference in electrode spacing has a great impact on the stability of detector performance.

[0007] In response to the above-mentioned defects of traditional three-dimensional groove detectors, a new type of hemispherical shell electrode silicon detector has been proposed in recent years. The structural model of this detector can indeed solve the defects of traditional three-dimensional groove detectors such as uneven electric field potential distribution and large dead zone. As a detector unit, the structural performance of the spherical detector is very outstanding and can be realized in theoretical simulation, but the ideal spherical structure is relatively difficult to manufacture in process.

[0008] The laser-drilled three-dimensional spherical electrode detector of the present invention can utilize existing process technology to form grooves by multiple uniform drillings with a laser, and doping is performed in the grooves by ion diffusion to finally form a spherical electrode. The distance between the anode and the cathode is made the same, and multiple equally spaced heavily doped rings are added to the upper surface to make the electric field potential distribution more uniform and reduce the dead zone.

[0009] Through the above analysis, the problems and defects of the prior art are as follows:

[0010] The performance of existing silicon detectors is relatively low, and the ideal spherical structure is relatively difficult to manufacture.

[0011] The difficulty of solving the above problems and defects is:

[0012] Traditional three-dimensional groove electrode detectors have their own unavoidable defects, and ideal spherical detectors are extremely difficult to manufacture.

[0013] The significance of solving the above problems and defects is:

[0014] As a detector unit, the structural performance of the spherical detector is very outstanding. Through clever structural design, existing processes such as laser etching and ion diffusion can be used to realize the spherical electrode design, so that it does not only exist in theoretical simulation. And by adding a heavy doping ring on the upper surface, the electric field is made more uniform and the dead zone is reduced. These technologies have greatly improved the performance of silicon detectors. Summary of the invention

[0015] In view of the problems existing in the prior art, the present invention provides a laser-drilled three-dimensional spherical electrode detector, a design method and an application thereof.

[0016] The present invention is implemented as follows: a design method for a laser-drilled three-dimensional spherical electrode detector, comprising:

[0017] The grooves are formed by multiple and uniform drilling with a laser, and doping is performed in the grooves by ion diffusion to eventually form a spherical electrode.

[0018] The structural dimensions and internal structure are calculated using the formula. The formula is as follows:

[0019] Given d=R,pitch P,gap g=βP

[0020] x i =iP(i=1,2,....N)

[0021]

[0022]

[0023] y N =ξR(ξtakes a value of 0.9)

[0024] d=R,x N =R,y N =ξR,(0<ξ<1),P,W,g

[0025]

[0026] x i =iP(i=1,....,N)

[0027]

[0028] Where R = 200 μm, β = 0.8, P = 20 μm, W = 16, x i Represents the distance from the center coordinate of the etching column to the origin, y i represents the height of the etching column, i represents the etching column number, N represents the number, y 10 =0.9*R.

[0029] The radius of the N-type collector anode on the upper surface is 17.5 μm, and the radius of the anode aluminum electrode contact layer is 17.5 μm. The spacing between the inner and outer circles of all heavily doped rings on the upper surface is 17.5 μm, and the spacing between each ring is 3.5 μm.

[0030] There are ten etching rings in the substrate of the present invention (etching columns in the X-axis section), the column width is 16 μm, and the column spacing is 4 μm. From the inside to the outside, the central abscissa and ordinate of each etching column are:

[0031] x 1=20μm,y 1 =1.0025μm; x 2 =40μm,y 2 =4.04μm; x 3 =60μm,y 3 =9.212μm; x 4 =80μm,y 4 =16.6969μm; x 5 =100μm,y 5 =26.7949μm; x 6 =120μm,y 6 =40.00μm; x 7 =140μm,y 7 =57.1714μm; x 8 =160μm,y 8 =80μm; x 9 =180μm,y 9 =112.822μm; x 10 =200μm,y 10 =180μm.

[0032] The radius of the cathode aluminum electrode contact layer on the lower surface is 200 μm.

[0033] Furthermore, in the spherical electrode, the distance between the anode and the cathode is the same, so that the potential distribution in the spherical electrode is uniform. Fig.14 shown.

[0034] Another object of the present invention is to provide a laser drilling three-dimensional spherical electrode detector provided with:

[0035] N-type lightly doped silicon substrate;

[0036] The middle of the upper end of the N-type lightly doped silicon substrate is doped with an N-type heavily doped anode, and the outer side of the N-type heavily doped anode is doped with a plurality of P-type heavily doped upper surface rings arranged at equal intervals;

[0037] A P-type heavily doped cathode is arranged at the bottom of the N-type lightly doped silicon substrate.

[0038] Furthermore, the P-type heavily doped cathode is provided with a P-type heavily doped ring and a P-type heavily doped surface, the P-type heavily doped ring is provided with a plurality of equidistantly arranged rings, and the P-type heavily doped surface is located at the bottom of the P-type heavily doped ring.

[0039] Furthermore, the doping depths of the multiple P-type heavily doped rings in the N-type lightly doped silicon substrate gradually increase from the middle to the outside.

[0040] Furthermore, the upper end of the N-type heavily doped anode and the lower end of the P-type heavily doped cathode are connected to an anode aluminum electrode contact layer and a cathode aluminum electrode contact layer, respectively.

[0041] Furthermore, the upper end of the N-type lightly doped silicon substrate is covered with an upper surface SiO 2 The lower end of the N-type lightly doped silicon substrate is covered with a lower surface SiO 2 layer.

[0042] Combining all the above technical solutions, the advantages and positive effects of the present invention are as follows:

[0043] The detector in the present invention is spherical in design, and the distance between the anode and the cathode is the same, so that the potential distribution in the detector is very uniform (such as Fig.14 ), which improves the charge collection rate of the new detector unit.

[0044] The design of the heavily doped ring on the upper surface of the present invention makes the electric field distribution on the inner surface of the detector unit more uniform.

[0045] According to the existing technology, the present invention can realize a spherical electrode by uniformly drilling holes with a laser and ion diffusion doping.

[0046] The invention has a small full depletion voltage and low energy consumption. In the absence of radiation, the full depletion voltage is 23V, which is lower than the full depletion voltage of a conventional three-dimensional trench detector of the same size, and has smaller leakage current and capacitance.

[0047] The presence of the entire lower surface electrode in the present invention makes it easier to arrange into an array and greatly reduces the dead zone. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0049] Figure 1 It is a schematic diagram of the structure of a laser-drilled three-dimensional spherical electrode detector provided in an embodiment of the present invention.

[0050] Figure 2 It is a cross-sectional view of a laser-drilled three-dimensional spherical electrode detector provided in an embodiment of the present invention.

[0051] Figure 3 It is a schematic diagram of the contact layer structure of the anode aluminum electrode provided in an embodiment of the present invention.

[0052] Figure 4It is a schematic diagram of a P-type heavily doped ring structure provided in an embodiment of the present invention.

[0053] Figure 5 It is a schematic diagram of the cathode aluminum electrode contact layer structure provided in an embodiment of the present invention.

[0054] In the figure: 1. Anode aluminum electrode contact layer; 2. N-type heavily doped anode; 3. P-type heavily doped upper surface ring; 4. Upper surface SiO 2 layer; 5, N-type lightly doped silicon substrate; 6, P-type heavily doped ring; 7, P-type heavily doped surface; 6 and 7 form a P-type heavily doped cathode; 8, cathode aluminum electrode contact layer; 9, lower surface SiO 2 layer.

[0055] Figure 6 is an electron concentration curve diagram provided by an embodiment of the present invention.

[0056] Figure 7 It is a partially enlarged view of the electron concentration curve provided by an embodiment of the present invention.

[0057] Figure 8 This is a simulation diagram of electric field distribution provided by an embodiment of the present invention.

[0058] Fig. 9 This is a simulation diagram of the electric field distribution of a traditional three-dimensional groove detector of the same size provided by an embodiment of the present invention.

[0059] Fig.10 It is a potential distribution simulation diagram provided by an embodiment of the present invention.

[0060] Fig.11 This is a simulation diagram of the potential distribution of a conventional three-dimensional trench detector of the same size provided by an embodiment of the present invention.

[0061] Fig.12 is a leakage current curve diagram provided by an embodiment of the present invention.

[0062] Fig.13 This is a comparison diagram of leakage current between the present invention and a conventional three-dimensional trench detector of the same size provided by an embodiment of the present invention.

[0063] Fig.14 In the spherical electrode provided by an embodiment of the present invention, the distance between the anode and the cathode is the same, so that the potential distribution in the spherical electrode is uniform. DETAILED DESCRIPTION

[0064] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0065] In view of the problems existing in the prior art, the present invention provides a laser-drilled three-dimensional spherical electrode detector, which is described in detail below in conjunction with the accompanying drawings.

[0066] The present invention provides a design method for a laser-drilled three-dimensional spherical electrode detector, comprising:

[0067] The grooves are formed by multiple and uniform drilling with a laser, and doping is performed in the grooves by ion diffusion to eventually form a spherical electrode.

[0068] In the spherical electrode, the distance between the anode and the cathode is the same, so that the potential distribution in the spherical electrode is uniform.

[0069] like Figures 1 to 5 As shown, the laser-drilled three-dimensional spherical electrode detector provided in the embodiment of the present invention is provided with a 400 μm*400 μm*200 μm cubic column N-type lightly doped silicon substrate 5, and the N-type lightly doped silicon substrate 5 is N-type lightly doped, and the doping concentration is 1×10 12 / cm 3 The top layer of the N-type lightly doped silicon substrate 5 is an anode aluminum electrode contact layer 1 covering the N-type heavily doped anode 2, serving as a central anode signal output point.

[0070] The upper surface of the N-type lightly doped silicon substrate 5 is composed of eight P-type heavily doped upper surface rings 3 and a central heavily doped anode. The doped rings are doped with a concentration of 1×10 18 / cm 3 The P-type is heavily doped, the doping depth is 1μm, and the anode is doped with a concentration of 1×10 18 / cm 3 N-type heavily doped, with a doping depth of 1μm.

[0071] The cathode consists of ten etched rings (etched columns in the X-axis section) and a heavily doped lower surface. The etched rings are formed into P-type heavily doped rings by ion diffusion, with a doping concentration of 1×10 19 / cm 3 , the lower surface is doped with a concentration of 1×10 18 / cm 3 The P-type heavily doped surface has a doping depth of 1 μm. The P-type heavily doped surface plays the role of connecting the etching rings, making the cathode a whole. The bottom is the cathode aluminum electrode contact layer 8 covering the heavily doped lower surface, which serves as the cathode voltage input point.

[0072] The top and bottom portions of the laser-drilled three-dimensional spherical electrode detector in the embodiment of the present invention where there is no electrode contact layer are covered with SiO 2 The aluminum electrode contact layer on the upper and lower surfaces is 1 μm thick, and the upper surface SiO 2 Layer 4 and lower surface SiO 2 Layer 9 has a thickness of 0.5 μm.

[0073] In a preferred embodiment of the present invention, the structural dimensions and internal structure are calculated by a formula. The formula is as follows:

[0074] Given d=R,pitch P,gap g=βP

[0075] x i =iP(i=1,2,....N)

[0076]

[0077]

[0078] y N =ξR(ξtakes a value of 0.9)

[0079] d=R,x N =R,y N =ξR,(0<ξ<1),P,W,g

[0080]

[0081] x i =iP(i=1,....,N)

[0082]

[0083] Where R = 200 μm, β = 0.8, P = 20 μm, W = 16, x i Represents the distance from the center coordinate of the etching column to the origin, y i represents the height of the etching column, i represents the etching column number, N represents the number, y 10 =0.9*R.

[0084] The radius of the N-type collector anode on the upper surface is 17.5 μm, and the radius of the anode aluminum electrode contact layer is 17.5 μm. The spacing between the inner and outer circles of all heavily doped rings on the upper surface is 17.5 μm, and the spacing between each ring is 3.5 μm.

[0085] There are ten etching rings in the substrate of the present invention (etching columns in the X-axis section), the column width is 16 μm, and the column spacing is 4 μm. From the inside to the outside, the central abscissa and ordinate of each etching column are:

[0086] x 1 =20μm,y 1 =1.0025μm; x 2 =40μm,y 2 =4.04μm; x 3 =60μm,y3 =9.212μm; x 4 =80μm,y 4 =16.6969μm; x 5 =100μm,y 5 =26.7949μm; x 6 =120μm,y 6 =40.00μm; x 7 =140μm,y 7 =57.1714μm; x 8 =160μm,y 8 =80μm; x 9 =180μm,y 9 =112.822μm; x 10 =200μm,y 10 =180μm.

[0087] The radius of the cathode aluminum electrode contact layer on the lower surface is 200 μm.

[0088] The working principle of the present invention is:

[0089] The laser-drilled three-dimensional spherical electrode detector provided in the embodiment of the present invention can utilize existing process technology to form grooves by multiple uniform drillings with a laser, and doping is performed in the grooves by ion diffusion to finally form a spherical electrode. The basic principle of the three-dimensional spherical electrode detector is the same as that of many other types of detectors, which is a PN junction or a PIN junction. The laser-drilled three-dimensional spherical electrode detector provided in the embodiment of the present invention forms a PN junction between the etched column and the silicon substrate, and forms an external electric field by applying a reverse bias voltage, so that electrons drift toward the anode and holes drift toward the cathode. The electrons are collected by the central anode on the upper surface of the detector, so the potential here is the highest. Then, after the feedback current signal is processed by the external integrated circuit, information such as the energy, position, and motion trajectory of the incident particle can be obtained.

[0090] In the current research field of silicon detectors, the effects of depletion voltage, capacitance, leakage current, potential, electric field, charge collection and other parameters on the energy resolution, collection efficiency, noise and energy consumption of silicon detectors are generally used as indicators to evaluate whether the performance of the detector is superior.

[0091] By comparing the characteristics of the electrical properties of traditional three-dimensional groove detectors of the same size, such as leakage current, depletion voltage, electric field potential distribution, etc., the advantages of laser drilling three-dimensional spherical electrode detectors in structure and performance are explained. The reason for the leakage current is the surface effect of the PN junction; the particle charge on the surface of the device causes the image charge inside the device, which causes the PN junction to produce surface induction, thereby forming a surface depletion region and causing the depletion region to change, resulting in surface leakage current. Therefore, the smaller the leakage current, the smaller the impact on the depletion region, the smaller the noise of the detector, and the higher the energy resolution. By comparison, the leakage current of the laser drilling three-dimensional spherical electrode detector is three orders of magnitude smaller than that of the three-dimensional groove detector of the same size. In addition, the electric field distribution of the detector is uniform, the potential distribution is highly symmetrical, and its properties are more stable. The electron drift orbit will be more obvious, and the energy resolution and collection efficiency will be better. By comparison, the laser drilling three-dimensional spherical electrode detector is superior to the three-dimensional groove detector of the same size and has a smaller depletion voltage. The presence of the entire electrode on the lower surface of the detector makes it have enough space to apply the bias voltage, and it is easier to arrange it into an array and greatly reduce the dead zone.

[0092] The technical solution of the present invention is further described below in conjunction with simulation experiments.

[0093] FIG6 is a graph showing an electron concentration curve provided by an embodiment of the present invention. Figure 7 It is a partial enlarged view of the electron concentration curve provided by the embodiment of the present invention. As the bias voltage increases from 0V to 33V, the electron concentration continues to decrease (the depletion region of the detector continues to expand) until it reaches complete depletion. It can be seen that when the voltage reaches 23V, the electron concentration in the depletion region has begun to be lower than the concentration of the silicon substrate by 1×10 12 / cm 3 , so we judge the depletion voltage value to be 23V.

[0094] Figure 8 This is a simulation diagram of electric field distribution provided by an embodiment of the present invention.

[0095] Fig. 9 This is a simulation diagram of the electric field distribution of a traditional three-dimensional groove detector of the same size provided by an embodiment of the present invention. It can be clearly seen that the electric field distribution of the present invention is more uniform than that of the traditional three-dimensional groove detector.

[0096] Fig.10 This is a simulation diagram of the electric potential distribution of the invention.

[0097] Fig.11 This is a simulation diagram of the potential distribution of a conventional three-dimensional groove detector of the same size provided by an embodiment of the present invention. It can be clearly seen that the potential distribution of the present invention is more symmetrical than that of the conventional three-dimensional groove detector.

[0098] Fig.12is a leakage current curve diagram provided by an embodiment of the present invention.

[0099] Fig.13 This is a comparison diagram of the leakage current of the present invention and the traditional three-dimensional groove detector of the same size provided by the embodiment of the present invention. It can be clearly seen that the leakage current of the present invention is much smaller than the leakage current of the traditional three-dimensional groove detector.

[0100] like Fig.14 As shown, in a preferred embodiment of the present invention, in the spherical electrode, the distance between the anode and the cathode is the same, so that the potential distribution in the spherical electrode is uniform.

[0101] In the description of the present invention, unless otherwise specified, "plurality" means two or more than two; the orientations or positional relationships indicated by the terms "upper", "lower", "left", "right", "inner", "outer", "front end", "rear end", "head", "tail", etc. are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", "third", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0102] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any modification, equivalent substitution and improvement made by any technician familiar with the technical field within the technical scope disclosed by the present invention and within the spirit and principle of the present invention should be covered by the protection scope of the present invention.

Claims

1. A design method for a laser-drilled three-dimensional spherical electrode detector, characterized in that: The design method of the laser-drilled three-dimensional spherical electrode detector comprises: The grooves are formed by multiple and uniform drilling with a laser, and ion diffusion is used to dope the grooves, eventually forming a spherical electrode. The laser-drilled three-dimensional spherical electrode detector forms a PN junction between the etched column and the silicon substrate, and forms an external electric field by applying a reverse bias voltage, so that the electrons drift toward the anode and the holes drift toward the cathode. The electrons are collected by the central anode on the upper surface of the detector, so the potential here is the highest; then the feedback current signal is processed by the external integrated circuit to obtain information about the energy, position, and motion trajectory of the incident particles; In the spherical electrode, the distance between the anode and the cathode is the same, so that the potential distribution in the spherical electrode is uniform; The design method of the laser-drilled three-dimensional spherical electrode detector further includes the design of structural dimensions and internal structure, which is calculated by the following formula: Set d = R, spacing P, gap g = βP x i =iP(i=1,2,....N) d=R,x N =R,y N =ξR,(0<ξ<1), Where R = 200 μm, β = 0.8, P = 20 μm, W = 16, x i Represents the distance from the center coordinate of the etching column to the origin, y i represents the height of the etching column, i represents the etching column number, N represents the number, and y 10 =0.9*R.

2. An application of the design method as claimed in claim 1 in the design of aerospace probes.

3. An application of the design method as claimed in claim 1 in detector design in the fields of astrophysics, high energy physics, nuclear medicine and national defense.

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