Preparation method of low dark current silicon drift detector based on double-sided temporary bonding process

Abstract

The invention relates to a method for preparing a low dark current silicon drift detector based on a double-sided temporary bonding process, which comprises the following steps of: after a front surface process of an SDD wafer is finished, carrying out temporary bonding on the front surface of the SDD wafer by adopting a temporary bonding adhesive and a temporary bonding glass slide; thinning and polishing the back surface of the SDD wafer after the temporary bonding is completed, and carrying out a CMP (Chemical Mechanical Polishing) process on the back surface of the SDD wafer after the thinning and polishing to eliminate a damaged layer and reduce the dark current of a device; then, process manufacturing is carried out on the back face of the SDD wafer, after manufacturing is completed, the glass sheet and the SDD wafer are stripped off through a laser debonding process, and the front face of the wafer is exposed; when the active region of the SDD wafer is manufactured, a thin gate oxide layer is adopted for doping for shielding injection, the shielding oxide layer is removed after injection is completed, furnace tube oxidation and annealing are carried out, and the dark current of a device is reduced; when the oxide layer of the SDD contact hole is removed, a manufacturing process combining dry etching and wet etching is adopted, so that damage to a silicon substrate is avoided, and dark current of a device is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductor devices and relates to a method for preparing a low dark current silicon drift detector based on a double-face simultaneous bonding process. Background Art

[0002] Silicon Drift Detector (SDD) is a fully depleted detector with a lateral drift electric field and a longitudinal PN junction. When high-energy particles are incident on the device, electron-hole pairs are generated. Under the action of the lateral drift electric field, most carriers drift to the middle anode area and are collected. Silicon drift detectors have very strict requirements on dark current, which is the core key indicator of the device and directly affects the final energy resolution of the device. Silicon drift detectors are mainly used in medical imaging, X-ray fluorescence spectrometers, X-ray spectrometers, electron microscopes, etc.

[0003] The preparation process of silicon drift detectors is significantly different from that of conventional silicon-based detectors. When preparing conventional silicon-based detectors, only photolithography, etching, injection and other processes need to be performed on the front side of the silicon wafer, and no processes are required on the back side. However, silicon drift detectors require photolithography, etching, injection, cleaning and other processes on both the front and back sides of the silicon wafer, so the process control requirements are more stringent.

[0004] At present, there are many problems in the preparation process of silicon drift detectors: 1. When the front (back) surface is patterned, the back (front) surface will be scratched and contaminated due to the transmission and contact of the processing stage by the mechanical arm; 2. During the ion implantation process, the non-process surface will be scratched and contaminated due to the transmission and contact of the processing stage by the mechanical arm; 3. The etching damage of the contact hole dielectric causes the dark current to increase. These problems have seriously restricted the preparation and development of silicon drift detectors. Summary of the invention

[0005] In view of this, the purpose of the present invention is to solve the above-mentioned problems and provide a method for preparing a low dark current silicon drift detector based on a double-sided simultaneous bonding process, which combines dry etching of contact holes with wet etching, reduces the damage to silicon during the contact hole etching process, and effectively reduces the dark current of the chip.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] A method for preparing a low dark current silicon drift detector based on a double-sided temporary bonding process, after the front side process of the SDD wafer is completed, a temporary bonding adhesive and a temporary bonding glass carrier are used to temporarily bond the front side of the SDD wafer; then the back side of the SDD wafer after temporary bonding is thinned and polished, and then the back side of the SDD wafer after thinning and polishing is subjected to a CMP process to eliminate a damage layer and reduce the dark current of the device; then the back side of the SDD wafer is processed, and after the production is completed, a laser debonding process is used to peel off the glass sheet and the SDD wafer to expose the front side of the wafer;

[0008] Among them, when the active area of ​​the SDD wafer is produced, a thin gate oxide layer is used for shielding injection. After the injection is completed, the shielding oxide layer is removed, and furnace tube oxidation and annealing are performed to reduce the dark current of the device. When the oxide layer of the SDD contact hole is removed, a production 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] Furthermore, the preparation method comprises the following steps:

[0010] S1, cleaning and drying the SDD wafer after the front process is completed for standby use;

[0011] S2, coating and curing the temporary bonding adhesive on the temporary bonding glass slide;

[0012] S3, aligning the SDD wafer after the front process is completed with the temporary bonding glass carrier;

[0013] S4, bonding the aligned SDD wafer and the temporary bonding glass carrier on a bonding machine by applying a set pressure;

[0014] S5, placing the SDD wafer after pressure bonding in a vacuum oven for heat curing to achieve firm adhesion between the SDD wafer and the temporary bonding glass carrier, thus completing temporary bonding of the wafer;

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

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

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

[0018] S9, doping the back active area of ​​the SDD wafer after the CMP process is completed, using a silicon dioxide shielding layer implantation doping process;

[0019] S10, after the active area is doped, the silicon dioxide shielding layer is removed by wet etching with BOE solution;

[0020] S11, regrowing a 300±10 nm thick silicon dioxide passivation layer on the wafer from which the silicon dioxide shielding layer has been removed;

[0021] S12, removing the oxide layer of the contact hole, using dry etching to etch the 250±10nm thick oxide layer, and then completely removing the last 50nm oxide layer by wet etching;

[0022] S13, manufacturing metal electrodes on the SDD wafer after the contact holes are manufactured;

[0023] S14, performing a laser debonding process on the wafer after the metal electrode is manufactured, and separating the SDD wafer from the temporary bonded glass carrier;

[0024] S15, removing the temporary bonding adhesive from the SDD wafer obtained in S14 using an adhesive removal solution;

[0025] S16, cleaning the SDD wafer obtained in S15 to obtain a finally manufactured SDD wafer.

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

[0027] Furthermore, in step S3, a SUSSMA8 double-sided photolithography machine is used to align the SDD wafer with the temporary bonded glass carrier.

[0028] Further, in step S4, the aligned SDD wafer is bonded to the temporary bonding glass carrier on a bonding machine by applying a pressure of 1000N.

[0029] Further, in step S5, the solidified product is cured by heating in a vacuum oven at 300±10° C. for 5 to 7 minutes.

[0030] The beneficial effects of the present invention are:

[0031] 1. In view of the fact that silicon drift detectors need to be processed on both sides, in order to avoid scratches, contamination, particles, etc. on the wafer during the double-sided production process, which would cause deterioration of chip performance, the reverse (front) side is temporarily bonded when the front (reverse) side is processed to avoid scratches, contamination, etc., which can effectively reduce the dark current of the chip and improve the wafer yield. In view of the problem of large dark current of the chip caused by contact hole dielectric etching damage, a process of dry etching of contact holes combined with wet etching is proposed, which reduces the damage to silicon during the contact hole etching process and effectively reduces the dark current of the chip.

[0032] 2. Since the front side is temporarily bonded, the front side can be effectively protected during the back side process to avoid scratches and contamination, thereby effectively reducing the dark current of the chip and improving the yield rate. After the back side process is completed, the laser debonding process can be used to effectively remove the front side glass sheet without causing damage to the front side.

[0033] 3. The present invention uses a thin oxide layer to shield the injection, which can prevent the introduction of particles and metal contamination when the active area is doped. After the injection is completed, the shielding oxide layer is removed. During the high-temperature furnace tube oxidation, the injection damage can be eliminated, the oxidation quality can be improved, and the dark current of the chip can be reduced. When the contact hole oxide layer is removed, the dry etching will damage the silicon substrate, thereby increasing the dark current. After most of the oxide layer is etched by dry etching, the last small part of the oxide layer is removed by wet etching, which not only ensures the morphology of the hole but also avoids damage to the silicon substrate, thereby reducing the dark current of the chip.

[0034] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below in conjunction with the accompanying drawings, wherein:

[0036] Figure 1 It is a schematic flow chart of the method for preparing a low dark current silicon drift detector based on a double-face simultaneous bonding process in the present invention. DETAILED DESCRIPTION

[0037] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0038] Among them, the drawings are only used for illustrative explanations, and they only represent schematic diagrams rather than actual pictures, and should not be understood as limitations on the present invention. In order to better illustrate the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of actual products. For those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0039] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right", "front", "rear", etc. indicate the orientation or position relationship, they are based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the terms describing the position relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0040] See also Figure 1 , is a method for preparing a low dark current silicon drift detector based on a double-face simultaneous bonding process, comprising the following steps:

[0041] S1, cleaning and drying the SDD wafer after the front process is completed for standby use;

[0042] S2, coating the temporary bonding adhesive on the temporary bonding glass slide to a thickness of 30±3 μm and curing the adhesive;

[0043] S3. Align the SDD wafer after the front process is completed with the temporary bonded glass carrier; use the SUSSMA8 double-sided lithography machine to achieve the alignment of the SDD wafer and the glass carrier.

[0044] S4, bonding the aligned SDD wafer and the temporary bonding glass carrier on a bonding machine by applying a pressure of 1000N;

[0045] S5, placing the wafer after pressure bonding in a vacuum oven for curing at 300±10°C for 5-7 minutes, so as to achieve a firm adhesion between the SDD wafer and the temporary bonding glass slide, and complete the temporary bonding of the wafer;

[0046] S6. After the temporary bonding, the SDD wafer is subjected to edge removal and cleaning processes to remove residual adhesive on the edge of the wafer, prevent contamination of the process machine in subsequent processes, and reduce contamination and particles on the surface of the wafer;

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

[0048] S8, after the SDD wafer is thinned, a back CMP process is performed to remove 1 to 2 μm of the back damage layer and adjust the wafer flatness;

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

[0050] S10, after the active area is doped, the silicon dioxide shielding layer is removed by wet etching with a BOE solution;

[0051] S11, regrowing a 300±10nm silicon dioxide passivation layer on the wafer with the silicon dioxide shielding layer removed;

[0052] S12, removing the oxide layer of the contact hole, using dry etching to etch 250±10nm of the oxide layer, and then completely removing the last 50nm of the oxide layer by wet etching;

[0053] S13, manufacturing metal electrodes on the wafer after the contact holes are manufactured;

[0054] S14, performing a laser debonding process on the wafer after the metal electrode is manufactured, with a laser power of 4W and a frequency of 60kHz, to separate the SDD wafer from the temporary bonded glass carrier;

[0055] S15, removing the temporary bonding adhesive from the SDD wafer obtained in S14 using a special adhesive removal solution;

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

[0057] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution, which should be included in the scope of the claims of the present invention.

Claims

1. A method for preparing a low dark current silicon drift detector based on a double-face simultaneous bonding process, characterized in that: After the SDD wafer front process is completed, the SDD wafer front is temporarily bonded using temporary bonding glue and temporary bonding glass carrier; then the SDD wafer back after temporary bonding is thinned and polished, and then the SDD wafer back after thinning and polishing is subjected to CMP process to eliminate the damage layer and reduce the device dark current; then the SDD wafer back is processed, and after the production is completed, the glass sheet and the SDD wafer are separated by laser debonding process to expose the wafer front; Among them, when the active area of ​​the SDD wafer is produced, a thin gate oxide layer is used for shielding injection. After the injection is completed, the shielding oxide layer is removed, and furnace tube oxidation and annealing are performed to reduce the dark current of the device. When the oxide layer of the SDD contact hole is removed, a production process combining dry etching and wet etching is used to avoid damage to the silicon substrate and reduce the dark current of the device.

2. The method for preparing a low dark current silicon drift detector based on a double-face simultaneous bonding process according to claim 1, characterized in that: The preparation method comprises the following steps: S1, cleaning and drying the SDD wafer after the front process is completed for standby use; S2, coating and curing the temporary bonding adhesive on the temporary bonding glass slide; S3, aligning the SDD wafer after the front process is completed with the temporary bonding glass carrier; S4, bonding the aligned SDD wafer and the temporary bonding glass carrier on a bonding machine by applying a set pressure; S5, placing the SDD wafer after pressure bonding in a vacuum oven for heat curing to achieve firm adhesion between the SDD wafer and the temporary bonding glass carrier, thus completing temporary bonding of the wafer; S6. After the temporary bonding, the SDD wafer is subjected to edge removal and cleaning processes to remove residual adhesive on the edge of the wafer, prevent contamination of the process machine in subsequent processes, and reduce contamination and particles on the surface of the wafer; S7, thinning the back side of the SDD wafer after temporary bonding and edge removal, and thinning the SDD wafer to a thickness of 500±20μm; S8, after the SDD wafer is thinned, a back CMP process is performed to remove 1 to 2 μm of the back damage layer and adjust the wafer flatness; S9, doping the back active area of ​​the SDD wafer after the CMP process is completed, using a silicon dioxide shielding layer implantation doping process; S10, after the active area is doped, the silicon dioxide shielding layer is removed by wet etching with a BOE solution; S11, regrowing a 300±10 nm thick silicon dioxide passivation layer on the wafer from which the silicon dioxide shielding layer has been removed; S12, removing the oxide layer of the contact hole, using dry etching to etch the 250±10nm thick oxide layer, and then completely removing the last 50nm oxide layer by wet etching; S13, manufacturing metal electrodes on the SDD wafer after the contact holes are manufactured; S14, performing a laser debonding process on the wafer after the metal electrode is manufactured, and separating the SDD wafer from the temporary bonded glass carrier; S15, removing the temporary bonding adhesive from the SDD wafer obtained in S14 using an adhesive removal solution; S16, cleaning the SDD wafer obtained in S15 to obtain a finally manufactured SDD wafer.

3. The method for preparing a low dark current silicon drift detector based on a double-face simultaneous bonding process according to claim 2, characterized in that: In step S2, a temporary bonding glue coating is applied with a thickness of 30±3 μm.

4. The method for preparing a low dark current silicon drift detector based on a double-face simultaneous bonding process according to claim 2, characterized in that: In step S3, a SUSSMA8 double-sided photolithography machine is used to align the SDD wafer with the temporary bonded glass carrier.

5. The method for preparing a low dark current silicon drift detector based on a double-face simultaneous bonding process according to claim 2, characterized in that: In step S4, the aligned SDD wafer is bonded to the temporary bonding glass carrier on a bonding machine by applying a pressure of 1000N.

6. The method for preparing a low dark current silicon drift detector based on a double-face simultaneous bonding process according to claim 2, characterized in that: In step S5, the material is cured by heating in a vacuum oven at 300±10° C. for 5 to 7 minutes.

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