Method for preparing low dark current silicon drift detector based on double-sided temporary bonding process

Abstract

The application relates to a preparation method of a low-dark-current silicon drift detector based on a double-sided temporary bonding process, wherein after the front surface process of an SDD wafer is completed, the front surface of the SDD wafer is temporarily bonded by using temporary bonding glue and a temporary bonding glass slide; then the back surface of the SDD wafer after the temporary bonding is thinned and polished, the back surface of the SDD wafer after the thinning and polishing is subjected to a CMP process to remove a damage layer and reduce the dark current of the device; then the back surface of the SDD wafer is subjected to process manufacturing, after the manufacturing is completed, the glass slide is peeled off from the SDD wafer by using a laser debonding process, and the front surface of the wafer is exposed; wherein when the active area of the SDD wafer is manufactured, doping is shielded by using a thin gate oxide layer to be injected, the shielding oxide layer is removed after the injection is completed, and the dark current of the device is reduced by performing furnace tube oxidation and annealing; when the SDD contact hole oxide layer is removed, a manufacturing process combining dry etching and wet etching is used to avoid damage to the silicon substrate and reduce the dark current of the device.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of semiconductor devices, and relates to a preparation method of a low-dark-current silicon drift detector based on a double-sided temporary bonding process. BACKGROUND

[0002] A silicon drift detector (SDD) is a kind of fully-depleted detector with a lateral drift electric field and a longitudinal PN junction. When a high-energy particle is incident into the device, an electron-hole pair is generated. The majority carriers are drifted to the middle anode region under the action of the lateral drift electric field and are collected. The silicon drift detector is very strict with dark current, which is a core key indicator of the device and directly affects the final energy resolution of the device. The silicon drift detector is mainly applied to medical imaging, X-ray fluorescence spectrometers, X-ray spectrometers, electron microscopes and the like.

[0003] The silicon drift detector has obvious differences from a conventional silicon-based detector in a preparation process. When the conventional silicon-based detector is prepared, only the front surface of a silicon wafer needs to be subjected to processes such as photolithography, etching and implantation, and the back surface does not need to be subjected to processes. However, the silicon drift detector needs to be subjected to processes such as photolithography, etching, implantation and cleaning on both the front and back surfaces of the silicon wafer, and therefore the process control requirement is more strict.

[0004] At present, there are many problems in the preparation process of the silicon drift detector. 1. When the front (back) surface is subjected to pattern photolithography, the non-process surface (process surface) is scratched and contaminated due to the transmission and contact of the processing platform by a mechanical arm. 2. In the ion implantation process, the non-process surface is also scratched and contaminated due to the transmission and contact of the processing platform by the mechanical arm. 3. The contact hole dielectric etching is damaged, which causes the dark current to be large. These problems seriously restrict the preparation and development of the silicon drift detector. SUMMARY

[0005] Therefore, the purpose of the application is to solve the above problems and provide a preparation method of a low-dark-current silicon drift detector based on a double-sided temporary bonding process. The dry etching of the contact hole is combined with wet etching, the damage to the silicon in the contact hole etching process is reduced, and the chip dark current is effectively reduced.

[0006] To achieve the above purpose, the application provides the following technical scheme.

[0007] A preparation method of a low dark current silicon drift detector based on a double-sided temporary bonding process, after the front surface process of the SDD wafer is completed, the front surface of the SDD wafer is temporarily bonded by using temporary bonding glue and a temporary bonding glass slide; then the back surface of the SDD wafer after temporary bonding is thinned and polished, and the back surface of the SDD wafer after thinning and polishing is subjected to a CMP process to eliminate the damage layer and reduce the dark current of the device; then the back surface of the SDD wafer is processed, and after the processing is completed, the glass slide and the SDD wafer are peeled apart by using a laser debonding process, and the front surface of the wafer is exposed;

[0008] In the process of manufacturing the active area of the SDD wafer, the doping is shielded by using a thin gate oxide layer, the shielding oxide layer is removed after the implantation is completed, and the furnace tube is oxidized and annealed to reduce the dark current of the device; when the SDD contact hole oxide layer is removed, a manufacturing process combining dry etching and wet etching is used to avoid damage to the silicon substrate and reduce the dark current of the device.

[0009] Further, the preparation method comprises the following steps:

[0010] S1, after the front surface process of the SDD wafer is completed, the SDD wafer is cleaned and dried for standby;

[0011] S2, the temporary bonding glass slide is coated with temporary bonding glue and solidified;

[0012] S3, the SDD wafer after the front surface process is aligned with the temporary bonding glass slide;

[0013] S4, the SDD wafer and the temporary bonding glass slide after alignment are bonded by applying a set pressure on a bonding machine device;

[0014] S5, the SDD wafer after pressure bonding is placed in a vacuum oven for heat curing to achieve firm adhesion of the SDD wafer and the temporary bonding glass slide, and the temporary bonding of the wafer is completed;

[0015] S6, the SDD wafer after temporary bonding is subjected to edge removal and cleaning process to remove the residual glue on the edge of the wafer, prevent contamination of the process machine in subsequent processes, and reduce the adhesion and particles on the surface of the wafer;

[0016] S7, the SDD wafer after temporary bonding edge removal is thinned on the back surface, and the SDD wafer is thinned to a thickness of 500±20 μm;

[0017] S8, the SDD wafer after thinning is subjected to a back surface CMP process to remove the back surface damage layer 1-2 μm and adjust the flatness of the wafer;

[0018] S9, after the CMP process is completed, the SDD wafer is back-side active area doped, and a silicon dioxide shielding layer injection doping process is adopted;

[0019] S10, after the active area doping is completed, a BOE solution wet etching is adopted to remove the silicon dioxide shielding layer;

[0020] S11, the wafer after the silicon dioxide shielding layer is removed is regrown with a 300±10nm thick silicon dioxide passivation layer;

[0021] S12, contact hole oxide layer removal is performed, after a dry etching of a 250±10nm thick oxide layer, the last 50nm oxide layer is completely removed by wet etching;

[0022] S13, the SDD wafer after the contact hole fabrication is completed is subjected to metal electrode fabrication;

[0023] S14, the wafer after the metal electrode fabrication is completed is subjected to laser debonding process, so that the SDD wafer is separated from the temporary bonding glass slide;

[0024] S15, the SDD wafer obtained in S14 is subjected to temporary bonding glue removal by using a debonding solution;

[0025] S16, the SDD wafer obtained in S15 is subjected to cleaning, so that the finally fabricated SDD wafer is obtained.

[0026] Further, in step S2, the temporary bonding glue is coated with a thickness of 30±3μm.

[0027] Further, in step S3, the SUSS MA8 double-sided photoetching machine is adopted to complete the alignment of the SDD wafer and the temporary bonding glass slide.

[0028] Further, in step S4, the SDD wafer and the temporary bonding glass slide after the alignment are bonded on the bonding machine device by applying a pressure of 1000N.

[0029] Further, in step S5, the 300±10℃ heat baking is performed in a vacuum oven for 5-7 minutes for solidification.

[0030] The present application has the following beneficial effects:

[0031] 1. The present application is aimed at the characteristics of silicon drift detector requiring double-sided process manufacturing, in order to avoid the damage, dirt, particles and other problems caused by double-sided manufacturing process to the wafer, causing the chip performance to deteriorate, therefore, when the front (back) surface is processed, the back (front) surface is temporarily bonded, so as to avoid damage, dirt and other problems, which can effectively reduce the chip dark current and improve the wafer yield; in order to solve the problem of large chip dark current caused by contact hole medium etching damage, a contact hole dry etching combined with wet etching process is proposed, which reduces the damage to silicon in the contact hole etching process and effectively reduces the chip dark current.

[0032] 2. Since the front surface is temporarily bonded, the front surface can be effectively protected during back surface processing, avoiding damage and dirt, thereby effectively reducing the chip dark current and improving the yield. After the back surface processing is completed, the front surface glass sheet can be effectively removed by laser debonding process without causing damage to the front surface.

[0033] 3. The present application adopts thin oxide layer shielding implantation, which can prevent the introduction of particles and metal dirt during active area doping, and remove the shielding oxide layer after implantation, so as to eliminate implantation damage, improve oxidation quality, and reduce chip dark current. When the contact hole oxide layer is removed, dry etching will cause damage to the silicon substrate, thereby causing the dark current to become large. After most of the oxide layer is removed by dry etching, the last small part of the oxide layer is removed by wet etching, which not only ensures the appearance of the hole but also avoids damage to the silicon substrate, thereby reducing the chip dark current.

[0034] Other advantages, objects and features of the present application will be set forth in part in the following specification, and in part will become apparent to those skilled in the art from a consideration of the following specification, or can be learned from practice of the present application. The objects and other advantages of the present application can be realized and attained by the following description. BRIEF DESCRIPTION OF DRAWINGS

[0035] In order to make the purpose, technical scheme and advantages of the present application more clear, the preferred detailed description of the present application will be combined with the drawings as follows, wherein:

[0036] Figure 1 The flowchart of the preparation method of the low dark current silicon drift detector based on the double-sided temporary bonding process in the present application. DETAILED DESCRIPTION

[0037] Following, the embodiments of the present application will be described in detail by specific examples, and other advantages and effects of the present application can be easily understood by those skilled in the art from the disclosure of this specification. The present application can also be implemented or applied by other different specific embodiments, and various modifications or changes can be made to the details in this specification based on different views and applications without departing from the spirit of the present application. It should be noted that the drawings provided in the following examples only illustrate the basic concept of the present application in a schematic manner, and the following examples and features in the examples can be combined with each other without conflict.

[0038] The drawings are only used for illustrative description, and the representation is only a schematic diagram, not a physical diagram, and cannot be understood as a limitation of the present application; in order to better illustrate the embodiments of the present application, some components in the drawings will be omitted, enlarged or reduced, and do not represent the actual product size; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings can be omitted.

[0039] The same or similar reference numerals in the drawings of the embodiments of the present application correspond to the same or similar components; in the description of the present application, it should be understood that if the terms "upper", "lower", "left", "right", "front", "back" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, only for the convenience of describing the present application and simplifying the description, and not to indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, therefore the positional relationship described in the drawings is only used for illustrative description, and cannot be understood as a limitation of the present application, for those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0040] Please refer to Figure 1 It is a kind of preparation method of low dark current silicon drift detector based on double-sided temporary bonding process, comprising the following steps:

[0041] S1, after the front process of SDD wafer is completed, it is cleaned and dried for standby;

[0042] S2, the temporary bonding glass slide is coated with temporary bonding glue 30±3 μm and solidified;

[0043] S3, the SDD wafer after the front process is completed is aligned with the temporary bonding glass slide; SUSSMA8 double-sided photoetching machine is used to realize the alignment of SDD wafer and glass slide.

[0044] S4, the SDD wafer and the temporary bonding glass slide after alignment are bonded on the bonding machine equipment by applying pressure 1000N;

[0045] S5, placing the wafer after the pressure bonding is completed in a vacuum oven for 300±10°C heat baking for 5-7 minutes to solidify, realizing the firm adhesion of the SDD wafer and the temporary bonding glass slide, and completing the temporary bonding of the wafer;

[0046] S6, removing the edge and cleaning process of the SDD wafer after the temporary bonding is completed, removing the edge residual glue of the wafer, preventing the pollution of the process machine in the subsequent process, and reducing the adhesion and particles on the wafer surface;

[0047] S7, back thinning of the SDD wafer after the temporary bonding edge is completed, thinning the SDD wafer to a thickness of 500±20μm;

[0048] S8, back surface CMP process of the SDD wafer after the thinning is completed, removing the back surface damage layer of 1-2μm, and adjusting the wafer flatness;

[0049] S9, back surface active area doping of the SDD wafer after the CMP process is completed, using the silicon dioxide shielding layer injection doping process;

[0050] S10, after the active area doping is completed, using the BOE solution wet etching to remove the silicon dioxide shielding layer;

[0051] S11, regrowing 300±10nm silicon dioxide passivation layer of the wafer after removing the silicon dioxide shielding layer;

[0052] S12, contact hole oxide layer removal, after dry etching 250±10nm oxide layer, finally 50nm oxide layer is completely removed by wet etching;

[0053] S13, metal electrode fabrication of the wafer after the contact hole fabrication is completed;

[0054] S14, laser debonding process of the wafer after the metal electrode fabrication is completed, laser power 4W, frequency 60kHz, separating the SDD wafer and the temporary bonding glass slide;

[0055] S15, using special adhesive remover to remove the temporary bonding adhesive of the SDD wafer obtained in S14;

[0056] S16, cleaning the SDD wafer obtained in S15 to obtain the finally fabricated SDD wafer.

[0057] Finally, it is to be explained that the above embodiments are only used to illustrate the technical solutions of the present application and not to limit, although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions, which should be covered in the scope of the claims of the present application.

Claims

1. A method for fabricating a low dark current silicon drift detector based on a two-sided face-to-face bonding process, characterized in that: After the front surface process of the SDD wafer is completed, the front surface of the SDD wafer is temporarily bonded by using temporary bonding glue and a temporary bonding glass slide; then the back surface of the SDD wafer after temporary bonding is thinned and polished, and the back surface of the SDD wafer after thinning and polishing is subjected to a CMP process to eliminate a damage layer and reduce a dark current of the device; then the back surface of the SDD wafer is subjected to process manufacturing, and after the manufacturing is completed, the glass slide is separated from the SDD wafer by using a laser debonding process, and the front surface of the wafer is exposed; In the process of manufacturing the active region of the SDD wafer, doping is shielded by using a thin gate oxide layer, the shielded oxide layer is removed after implantation, and the wafer is subjected to furnace tube oxidation and annealing to reduce the dark current of the device; in the process of removing the contact hole oxide layer of the SDD, a manufacturing process combining dry etching and wet etching is used to avoid damage to the silicon substrate and reduce the dark current of the device; The preparation method comprises the following steps: S1, the SDD wafer after the front surface process is completed is cleaned and dried for standby; S2, the temporary bonding glass slide is coated with temporary bonding glue and solidified; S3, the SDD wafer after the front surface process is completed is aligned with the temporary bonding glass slide; S4, the SDD wafer and the temporary bonding glass slide after alignment are bonded by applying a set pressure on a bonding machine device; S5, the SDD wafer after pressure bonding is placed in a vacuum oven for heat curing to achieve firm adhesion of the SDD wafer and the temporary bonding glass slide, and the temporary bonding of the wafer is completed; S6, the SDD wafer after temporary bonding is subjected to edge removal and cleaning process to remove the residual glue on the edge of the wafer, prevent contamination of the process machine in the subsequent process, and reduce the adhesion and particles on the surface of the wafer; S7, the SDD wafer after temporary bonding edge removal is thinned on the back surface, and the SDD wafer is thinned to a thickness of 500±20μm; S8, the SDD wafer after thinning is subjected to back surface CMP process to remove the back surface damage layer of 1-2μm and adjust the flatness of the wafer; S9, the SDD wafer after the CMP process is subjected to back surface active region doping, and a silicon dioxide shielding layer implantation doping process is used; S10, after the active region doping is completed, the silicon dioxide shielding layer is removed by using BOE solution wet etching; S11, the wafer after removing the silicon dioxide shielding layer is regrown with a 300±10nm thick silicon dioxide passivation layer; S12, contact hole oxide layer removal is performed, and after dry etching of a 250±10nm thick oxide layer, the last 50nm oxide layer is completely removed by wet etching; S13, the SDD wafer after the contact hole manufacturing is completed is subjected to metal electrode manufacturing; S14, the wafer after the metal electrode manufacturing is completed is subjected to laser debonding process to separate the SDD wafer from the temporary bonding glass slide; S15, the SDD wafer obtained in S14 is subjected to temporary bonding glue removal by using a glue removing solution; S16, the SDD wafer obtained in S15 is cleaned to obtain the finally manufactured SDD wafer.

2. The method for fabricating low dark current silicon drift detector based on double-sided temporary bonding process according to claim 1, wherein: In step S2, the thickness of the temporary bonding glue coating is 30±3μm.

3. The method of claim 1, wherein the method further comprises: forming a passivation layer on the first surface of the silicon wafer; and forming a second passivation layer on the second surface of the silicon wafer. In step S3, the alignment of the SDD wafer and the temporary bonding glass slide is completed by using SUSS MA8 double-sided photoetching machine.

4. The method of claim 1, wherein the method further comprises: forming a passivation layer on the front surface of the silicon wafer; and forming a backside passivation layer on the back surface of the silicon wafer. In step S4, the SDD wafer and the temporary bonding glass slide after the alignment are bonded by applying a pressure of 1000 N on the bonding machine device.

5. The method of claim 1, wherein the method further comprises: In step S5, the curing is performed in a vacuum oven at 300±10℃ for 5-7 minutes. ​

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