CN118782674B - Photodiode structure and preparation method - Google Patents
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
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Abstract
The invention provides a photodiode structure and a preparation method thereof, and belongs to the technical field of semiconductors. The photodiode structure comprises a substrate, wherein a cutoff ring, a protection ring, an anti-inversion terminal and a neutralization layer are arranged on the substrate, the cutoff ring, the protection ring, the anti-inversion terminal and the neutralization layer are all obtained by doping on the substrate, an oxide layer, a hole, a front metal layer and an insulating layer are sequentially arranged on the front side of the substrate, ions are injected into the back side of the substrate, the metal layer is arranged on the back side of the substrate, the cutoff ring is close to the outermost edge of the substrate, the anti-inversion terminal comprises a region from the protection ring to the outermost edge of the substrate, the surface doping concentration of the anti-inversion terminal is higher than the in-vivo doping concentration, and the neutralization layer is located between the protection ring and the cutoff ring and penetrates through the surface of the anti-inversion terminal to penetrate into the in-vivo of the anti-inversion terminal. The high ion concentration area can be transferred from the surface to the body, the surface electric field is reduced, the surface leakage current is reduced, and the transverse withstand voltage of the device is improved.
Description
Technical Field
The invention relates to the technical field of semiconductors, in particular to a photodiode structure and a photodiode preparation method.
Background
An important parameter of photodiodes is dark (drain) current, which is required to be small in value, on the order of nA. If the dark current is large, the detected noise is large, and the yield is reduced. For example, APD (Avalanche Photodiode) avalanche photodiodes, abbreviated as APD photodiodes, have increased avalanche multiplication compared to conventional photodiodes. Electron hole pairs generated by illumination are multiplied by 10-100 times in avalanche, so that the detection sensitivity of the APD photodiode is remarkably improved.
The photodiode has the problem of unqualified dark current parameters, and the main reasons are that 1, the dark current of a photosensitive area is the dark current of an injection damage repair and anti-reflection layer interface. 2. Dark current at the lateral terminal of the device, namely fixed cations and movable Na+ ions of the field oxide layer, causes the lightly doped P-type substrate to be inverted into N, and causes electric leakage, as can be seen particularly by comparing fig. 1 and 2.
In order to reduce the dark current of the transverse terminal of the class 2 device, the prior art mainly reduces Na+ ion introduction, and the main means is to purchase expensive cleaning and diffusion equipment and strengthen the cleaning facilities and management matched with workshops. However, due to factors such as staff in workshops and natural edible NaCl and salt, na+ cannot be eradicated, and the effect is reduced. And because the silicon dioxide has physical characteristics of absorbing boron and discharging phosphorus, the concentration of P-type ions on the surface is further reduced, and N is easier to form by inversion.
Therefore, the conventional photodiode structure has a problem that dark current of the lateral terminal cannot be effectively reduced.
Disclosure of Invention
The embodiment of the invention aims to provide a photodiode structure and a photodiode manufacturing method, wherein the photodiode structure can effectively realize low leakage current and high transverse voltage resistance of a diode.
In order to achieve the above object, a first aspect of the present application provides a photodiode structure, including a substrate, on which a cutoff ring, a guard ring, an anti-inversion terminal, a photosensitive region, and a neutralization layer are disposed, the cutoff ring, the guard ring, the anti-inversion terminal, and the neutralization layer are all obtained by doping on the substrate, the front surface of the substrate is sequentially provided with an oxide layer, a hole, a front metal layer, and an insulating layer, the back surface of the substrate is implanted with ions, and the back surface of the substrate is provided with a metal layer, wherein:
the cutoff ring is near the outermost edge of the substrate;
The anti-inversion terminal comprises a region from the guard ring to the outermost edge of the substrate, the surface doping concentration of the anti-inversion terminal being higher than the in-vivo doping concentration;
The neutralization layer is positioned between the protection ring and the cutoff ring, and penetrates through the surface of the anti-inversion terminal and goes deep into the body of the anti-inversion terminal.
In an embodiment of the present application, the guard rings are plural, and the neutralization layer is located between the guard ring closest to the cut-off ring and the cut-off ring.
In the embodiment of the application, a plurality of neutralization layers are arranged, and a plurality of neutralization layers are arranged between the protection ring and the stop ring at intervals.
In the embodiment of the application, the number of the protection rings is multiple, the number of the neutralization layers is multiple, one neutralization layer is positioned between the protection ring closest to the cut-off ring and the cut-off ring, and the other neutralization layers are respectively positioned between the two protection rings.
In the embodiment of the application, the ions in the neutralization layer are P-ions, an N-type structure is arranged between the protection ring and the stop ring, and the neutralization layer is positioned on the N-type structure.
In the embodiment of the application, the concentration of 0-1 um away from the surface of the substrate in the anti-inversion terminal is lower than the concentration of 2-3 um away from the surface of the substrate.
The second aspect of the present application provides a method for manufacturing a photodiode structure as described above, the method comprising:
Sequentially constructing a cutoff ring, a protection ring and a photosensitive region on a substrate, wherein the cutoff ring is close to the outermost edge of the substrate;
constructing an anti-inversion terminal on the substrate, wherein the anti-inversion terminal comprises a region from the guard ring to the outermost edge of the substrate, and the surface doping concentration of the anti-inversion terminal is higher than the in-vivo doping concentration;
building a neutralization layer on the substrate, the neutralization layer being located between the guard ring and the cutoff ring, the neutralization layer penetrating through the surface of the anti-inversion terminal into the body of the anti-inversion terminal;
Sequentially constructing a hole, a front metal layer and an insulating layer on the front surface of the substrate;
And implanting ions into the back surface of the substrate and constructing a back metal layer.
In an embodiment of the present application, the guard rings are plural, and a neutralization layer is constructed on the substrate, including:
a neutralizing layer is built on the substrate in a region between a guard ring nearest the stop ring and the stop ring.
In an embodiment of the present application, constructing a neutralizing layer on the substrate includes:
A plurality of neutralizing layers are built up on the substrate at a regional spacing between the guard ring and the cutoff ring.
In an embodiment of the present application, the guard rings are plural, and a neutralization layer is constructed on the substrate, including:
Constructing a neutralization layer on the substrate in the area between the guard ring nearest to the stop ring and the stop ring;
and respectively constructing a neutralization layer in the area between any two protection rings on the substrate.
In the embodiment of the application, the ions in the neutralization layer are P-ions, and the neutralization layer is constructed on the substrate and comprises the following steps:
an N-type structure is constructed in a region between the guard ring and the stop ring on the substrate;
Photoetching is carried out on the N-type structure, and a second dopant is implanted into the substrate to form a second terminal doped region, wherein the second dopant is P-ion;
And removing photoresist from the substrate on which the second terminal doped region is formed, and exposing the second terminal doped region to obtain a neutralization layer.
According to the technical scheme, the cutoff ring, the protection ring, the anti-inversion terminal, the photosensitive region and the neutralization layer are arranged on the substrate, the front surface of the substrate is sequentially provided with the oxidation layer, the hole, the front surface metal layer and the insulation layer, ions are injected into the back surface of the substrate, the metal layer is arranged on the back surface of the substrate, the cutoff ring is close to the outermost edge of the substrate, the anti-inversion terminal comprises a region from the protection ring to the outermost edge of the substrate, the surface doping concentration of the anti-inversion terminal is higher than the in-vivo doping concentration, the neutralization layer is located between the protection ring and the cutoff ring, and the neutralization layer penetrates through the surface of the anti-inversion terminal to penetrate deep into the body of the anti-inversion terminal. The anti-inversion structure is formed by diffusion doping, the surface concentration is higher, a neutralizing layer is added on the basis of the anti-inversion structure, and the part with higher surface concentration of the anti-inversion structure is neutralized by the newly added neutralizing layer to form a neutralizing layer with low doping concentration, so that a region with high ion concentration can be transferred from the surface to the inside of a body, the surface electric field is reduced, the surface leakage current is reduced, and the transverse withstand voltage of the device is also improved. The sensitivity of the device to Na+ ions is also reduced, and the workshop equipment and management cost are reduced.
Additional features and advantages of embodiments of the invention will be set forth in the detailed description which follows.
Drawings
The accompanying drawings are included to provide a further understanding of embodiments of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain, without limitation, the embodiments of the invention. In the drawings:
FIG. 1 schematically illustrates a schematic diagram of a raw APD photodiode structure;
FIG. 2 schematically illustrates an oxide layer induced N-inversion scheme;
FIG. 3 schematically illustrates an APD photodiode structure schematic of a novel junction termination structure in accordance with an embodiment of the present application;
FIG. 4 schematically illustrates a process flow diagram of a novel APD structure in accordance with an embodiment of the application;
fig. 5 schematically shows a schematic diagram of a terminal structure 2 according to an embodiment of the application;
fig. 6 schematically illustrates a 2-segment schematic of a terminal structure with an N-type structure added according to an embodiment of the application;
fig. 7 schematically shows a terminal NP exchange diagram according to an embodiment of the application.
Detailed Description
The following describes the detailed implementation of the embodiments of the present invention with reference to the drawings. It should be understood that the detailed description and specific examples, while indicating and illustrating the invention, are not intended to limit the invention.
In order to facilitate explanation of the scheme, the APD avalanche photodiode is mainly used for explanation, and compared with a common photodiode, the APD photodiode has an avalanche multiplication function. Electron hole pairs generated by illumination are multiplied by 10-100 times in avalanche, so that the detection sensitivity of the APD photodiode is remarkably improved. Because the avalanche effect of electrons is better than that of holes, APD devices are all electron avalanche type. In the substrate selection, a common photodiode can use a P-type semiconductor wafer substrate or an N-type semiconductor wafer substrate, and an APD device must use a P-type substrate. The P-type substrate is used as a photosensitive absorption layer, and electron hole pairs generated by illumination are generated. Electrons are negatively charged and flow to the positive electrode with positive voltage, and positive holes flow to the negative electrode directly after PN junction avalanche amplification. An APD photodiode uses a light doped P-type substrate of 1000 ohm cm or more.
Referring to fig. 3, fig. 3 schematically illustrates an APD photodiode structure schematic of a novel junction termination structure in accordance with an embodiment of the present application. The embodiment provides a photodiode structure, which comprises a substrate, wherein a cutoff ring, a protection ring, an anti-inversion terminal, a photosensitive region and a neutralization layer are arranged on the substrate, the cutoff ring, the protection ring, the anti-inversion terminal and the neutralization layer are all obtained by doping on the substrate, an oxide layer, a hole, a front metal layer and an insulating layer are sequentially arranged on the front surface of the substrate, ions are injected into the back surface of the substrate, and a metal layer is arranged on the back surface of the substrate, wherein the cutoff ring is close to the outermost edge of the substrate, the anti-inversion terminal comprises a region from the protection ring to the outermost edge of the substrate, the surface doping concentration of the anti-inversion terminal is higher than the in-vivo doping concentration, the neutralization layer is located between the protection ring and the cutoff ring, and the neutralization layer penetrates through the surface of the anti-inversion terminal to penetrate deep into the in-vivo of the anti-inversion terminal.
In this embodiment, the substrate may be a doped substrate, and may be a doped P-, or a doped N-, and the substrate obtained by the above method may be a substrate P-, or an N-, which is mainly used for explaining the scheme by using the substrate P-for convenience of explanation. The cutoff ring, the protection ring, the anti-inversion terminal and the neutralization layer are all obtained by doping on the substrate, the cutoff ring is near the edge of the substrate, the protection ring can be one or more, the protection ring and the cutoff ring are obtained by injecting dopants to corresponding positions, the dopants in the protection ring and the cutoff ring are different, for example, the cutoff ring is injected with P+, and the protection ring is injected with N. The region where the anti-inversion terminal is located is the region from the guard ring to the outermost edge of the substrate, and the whole region is annular, and can be obtained by injecting P into the region, so that the formed anti-inversion terminal is the P anti-inversion terminal. The anti-inversion terminal sequentially comprises a surface part and an internal part from the surface of the substrate to the inner direction of the substrate, wherein the doping concentration of the surface part is lower than that of the internal part. The neutralization layer is arranged between the protection ring and the stop ring, the neutralization layer is an annular area, N-neutralization layer can be obtained by doping N in the area, the depth of the neutralization layer penetrates into the body of the anti-inversion terminal from the surface of the anti-inversion terminal, and the specific depth can be determined according to practical conditions. The substrate is also provided with a photosensitive area, the front surface of the substrate is one surface with a cutoff ring, a protection ring, an anti-inversion terminal and a neutralization layer, and the other surface is the bottom surface of the substrate.
It should be noted that, the front surface of the substrate is provided with an oxide layer, a hole, a front metal layer and an insulating layer, which are all implemented by using the existing technology, and will not be described herein again. The ion is implanted into the back surface of the substrate, and the metal layer is disposed on the back surface of the substrate, which can be achieved by adopting the existing technology, and will not be described herein.
In the implementation process, a cutoff ring, a protection ring, an anti-inversion terminal, a photosensitive region and a neutralization layer are arranged on the substrate, an oxidation layer, a hole, a front metal layer and an insulation layer are sequentially arranged on the front surface of the substrate, ions are injected into the back surface of the substrate, and the metal layer is arranged on the back surface of the substrate, wherein the cutoff ring is close to the outermost edge of the substrate, the anti-inversion terminal comprises a region from the protection ring to the outermost edge of the substrate, the surface doping concentration of the anti-inversion terminal is higher than the in-vivo doping concentration, the neutralization layer is located between the protection ring and the cutoff ring, and the neutralization layer penetrates through the surface of the anti-inversion terminal to penetrate deep into the in-vivo of the anti-inversion terminal. The anti-inversion structure is formed by diffusion doping, the surface concentration is higher, a neutralizing layer is added on the basis of the anti-inversion structure, and the part with higher surface concentration of the anti-inversion structure is neutralized by the newly added neutralizing layer to form a neutralizing layer with low doping concentration, so that a region with high ion concentration can be transferred from the surface to the inside of a body, the surface electric field is reduced, the surface leakage current is reduced, and the transverse withstand voltage of the device is also improved. The sensitivity of the device to Na+ ions is also reduced, and the workshop equipment and management cost are reduced.
In some embodiments, the guard ring is a plurality of guard rings, and the neutralizing layer is located between the guard ring nearest the cutoff ring and the cutoff ring.
In the present embodiment, in the case where there are a plurality of guard rings, the neutralization layer is in the region between the outermost guard ring and the cutoff ring.
In some embodiments, the plurality of neutralization layers is provided in plurality, with a plurality of neutralization layer spacings disposed between the guard ring and the cutoff ring.
In this embodiment, the neutralization layer may include a plurality of annular portions, each of which is disposed at intervals.
The terminal structure is multi-section by arranging the plurality of neutralization layers, so that more parts are transferred from the surface to the inside of the body from the area with high ion concentration, the surface electric field is further reduced, the surface leakage current is reduced, and the transverse withstand voltage of the device is improved.
In some embodiments, the guard rings are plural, and the neutralization layer is plural, wherein one neutralization layer is located between the guard ring nearest to the stop ring and the stop ring, and the other neutralization layer is located between two guard rings, respectively.
In this embodiment, one neutralization layer is located between the guard ring closest to the stop ring and the stop ring, and the other neutralization layers are respectively located between the two guard rings, so that a plurality of diode structures can be formed.
By forming a plurality of diode structures, the voltage dividing capability of the device can be improved, and the transverse voltage withstand of the device is further improved.
In some embodiments, the ions in the neutralization layer are P-ions, an N-type structure is disposed between the guard ring and the stop ring, and the neutralization layer is located on the N-type structure.
In this embodiment, in the case where the anti-inversion terminal is a P anti-inversion terminal, the neutralization layer is doped with N to obtain an N-neutralization layer, and correspondingly, in the case where the ion in the neutralization layer is a P-ion, an N-type structure is arranged on the P anti-inversion terminal, and then a P-neutralization layer, i.e., the neutralization layer is doped with P-ion, is arranged on the N-type structure.
The N-type structure may be disposed between the guard ring and the stop ring, and the neutralization layer may be disposed on the N-type structure as a whole as a neutralization layer, so that the neutralization layer of the structure may be disposed between the guard ring closest to the stop ring and the stop ring, may be disposed between the guard ring and the stop ring at a distance, may be disposed between the guard ring closest to the stop ring and the stop ring, and may be disposed between the two guard rings, with the other neutralization layers being disposed between the two guard rings, respectively.
And an N-type structure is arranged between the protection ring and the cut-off ring, and the neutralization layer is positioned on the N-type structure, so that the terminal structure exchanged by NPs can be realized.
In some embodiments, the concentration of 0-1 um from the substrate surface in the anti-inversion terminal is lower than the concentration of 2-3 um from the substrate surface.
In the embodiment, the concentration of 0-1 um away from the surface of the substrate in the anti-inversion terminal is lower than the concentration of 2-3 um away from the surface of the substrate through software simulation calculation, and the anti-inversion terminal has lower surface doping concentration and higher bulk doping concentration, so that the device has higher breakdown voltage and lower leakage current.
The embodiment also provides a photodiode manufacturing method for manufacturing the above photodiode structure, the photodiode manufacturing method includes the following steps:
step 210, sequentially constructing a cutoff ring, a protection ring and a photosensitive region on a substrate, wherein the cutoff ring is close to the outermost edge of the substrate;
In this embodiment, the construction of the cutoff ring P+ and the guard ring N on the substrate P-is exemplified by substrate dicing, which involves placing the substrate to be processed on processing equipment ready for subsequent processing steps. RCA cleaning, namely cleaning the surface of the substrate by using an RCA cleaning method to remove organic and inorganic impurities on the surface so as to ensure the smooth proceeding of subsequent process steps. Sacrificial oxidation, namely forming an oxide layer on the surface of the substrate and using the oxide layer as a bottom layer of a photoetching pattern. Photolithography, which is to perform photolithography on the oxide layer, cover the entire substrate surface with photoresist, and then form a desired pattern through steps of exposure and development. And etching, namely transferring the photoetching pattern onto the oxide layer by utilizing an etching process to form a required structure. Photoresist stripping, namely removing the photoresist to expose the oxide layer below. The first lithography is performed on the oxide layer, and the shape and position of the stop ring P+ are defined. Stopping the P+ implantation, namely implanting P+ dopants into the substrate by ion implantation and other methods to form a P+ doped region. Photoresist removing, namely removing the photoresist to expose the P+ doped region, and obtaining the stop ring P+. Photolithography is then performed on the oxide layer, the entire surface is covered with photoresist, and then a desired guard ring pattern is formed through steps of exposure and development. And etching, namely transferring the photoetching pattern onto the oxide layer by utilizing an etching process to form a structure of the protection ring. Photoresist stripping, namely removing the photoresist to expose the oxide layer below. And (3) photoetching the guard ring N, namely photoetching on the oxide layer, and defining the shape and the position of the guard ring P+. And (4) protecting N implantation, namely implanting N dopants into the substrate by ion implantation and the like to form an N doped region. Photoresist removing, namely removing the photoresist to expose the N doped region, and obtaining the protection ring N. Photolithography is performed on the substrate to define the shape and position of the photosensitive region, followed by etching of the photosensitive region with a hydrofluoric acid solution, followed by cleaning of the photosensitive region with an RCA cleaning method to remove impurities that may remain, followed by oxidation treatment to form an oxide layer or a sacrificial layer as a subsequent process step to form the photosensitive region. Photolithography is performed on the substrate to define the shape and position of the photosensitive region P, then high-energy P-type dopants are implanted into the substrate by ion implantation or the like to form P-type doped regions, the photoresist is then removed to expose the underlying doped regions, and then rapid thermal annealing is performed to activate the doped materials and repair lattice defects. Then, an n+ type dopant is implanted into the substrate by ion implantation or the like to form an n+ type doped region, then the doped region is annealed by using a laser, then BOE etching and RCA cleaning are performed for cleaning and removing residual impurities, then oxidation treatment is performed under low temperature conditions, and then low pressure chemical vapor deposition is performed for depositing a thin film material to form a photosensitive region P.
Step 220, constructing an anti-inversion terminal on the substrate, wherein the anti-inversion terminal comprises a region from the guard ring to the outermost edge of the substrate, and the surface doping concentration of the anti-inversion terminal is higher than the in-vivo doping concentration;
In this embodiment, photolithography may be performed on the oxide layer to define the shape and position of the anti-inversion terminal, and then high-energy P-type dopants are implanted into the substrate by ion implantation or the like to form a P-doped region of the terminal. Or ordinary implantation, and then diffusion oxidation promotion is carried out to form a terminal P doped region. And then, a photoresist removing step is carried out, namely photoresist is removed, and the doped region below is exposed, so that the anti-inversion terminal is obtained.
Step 230, constructing a neutralization layer on the substrate, wherein the neutralization layer is positioned between the protection ring and the stop ring, and penetrates through the surface of the anti-inversion terminal and goes deep into the body of the anti-inversion terminal;
In this embodiment, photolithography is performed on the oxide layer for defining the shape and position of the terminal N. Then, implanting N-type dopants into the substrate by ion implantation or the like to form a terminal N-doped region, removing the photoresist to expose the doped region below, performing BOE etching, namely etching the surface by using a hydrofluoric acid solution, performing an RCA cleaning step, cleaning the surface by using an RCA cleaning method to remove impurities possibly remained, performing diffusion oxidation promotion, namely performing oxidation treatment to promote formation of an oxide layer, and finally forming a neutralization layer.
Step 240, sequentially constructing a hole, a front metal layer and an insulating layer on the front surface of the substrate;
In this embodiment, photolithography is performed on a substrate to define the shape and position of a hole, then a hole BOE etching is performed, a hole is formed by etching the area after photolithography with a hydrofluoric acid solution (BOE), then photoresist is removed to expose the hole structure below, and a metal deposition process is performed on the substrate to form a metal layer. Photolithography is then performed on the metal layer to define structures and patterns on the metal layer. And then etching the area on the metal layer to form a required metal structure, and removing the photoresist to expose the metal structure below. Then, alloying treatment is carried out on the metal layer so as to improve the performance of the metal layer, polyimide (PI) solution is spin-coated on the substrate, and a film is formed. Photolithography is then performed on the PI film to define structures and patterns on the PI film. The PI film is then cured to provide the desired physical and chemical properties.
It should be noted that, the forming of the PN junction terminal structure in the steps 230-240 may be implemented by one high-energy P-type injection, one N-type injection, one diffusion push-junction, or may be implemented by one normal P-type injection, one diffusion push-junction, one N-type injection, and then a second diffusion push-junction, which is not limited in this embodiment.
Because the curvature of the surface electric field is large and the interface state is increased, the breakdown voltage and leakage current of the PN junction on the surface are far greater than those in the PN junction. By utilizing this characteristic, the weak link is transferred from the surface to the body by means of two injection in the steps 230-240, so that the diode can realize low leakage current and high transverse voltage resistance.
And 250, implanting ions into the back surface of the substrate and constructing a back metal layer.
In this embodiment, the back side of the device may be thinned to reduce the thickness of the device, and then material or dopant is implanted into the back side to alter the performance of the device. The substrate is then laser treated to improve the backside implanted material or dopant. The back side of the substrate is metallized and then the back side metal layer is alloyed, after which the device is tested to verify its performance, function or quality. The tests include electrical tests, structural tests, performance tests, etc. to ensure that the device meets specification requirements.
In the implementation process, a cutoff ring, a protection ring and a photosensitive region are sequentially constructed on a substrate, the cutoff ring is close to the outermost edge of the substrate, an anti-inversion terminal is constructed on the substrate, the anti-inversion terminal comprises a region from the protection ring to the outermost edge of the substrate, the surface doping concentration of the anti-inversion terminal is higher than the in-vivo doping concentration, a neutralization layer is constructed on the substrate, the neutralization layer is positioned between the protection ring and the cutoff ring, the neutralization layer penetrates through the surface of the anti-inversion terminal and goes deep into the body of the anti-inversion terminal, a hole, a front metal layer and an insulating layer are sequentially constructed on the front surface of the substrate, ions are injected on the back surface of the substrate, and a back metal layer is constructed. The anti-inversion structure is formed by diffusion doping, so that the surface concentration is higher, a neutralizing layer is added on the basis of the anti-inversion structure, and the part with higher surface concentration of the anti-inversion structure is neutralized by the newly added neutralizing layer to form a neutralizing layer with low doping concentration, thereby transferring a region with high ion concentration from the surface to the inside of a body, reducing the surface electric field, reducing the surface leakage current and improving the transverse withstand voltage of the device. The sensitivity of the device to Na+ ions is also reduced, and the workshop equipment and management cost are reduced.
The following description will take an APD photodiode preparation as an example, please refer to fig. 4, which includes steps 1-11, and the process flow is as follows:
1, substrate throwing, RCA cleaning, sacrificial oxidation- (zero layer) photoetching, zero layer etching, photoresist removing, stop ring P+ (1 st time) photoetching, stop ring P+ injection and photoresist removing (stop ring P+);
2, photoetching the protection ring N (the 2 nd time), injecting the protection ring N, photoresist removing and protecting ring;
3, terminal P (3 rd time) photoetching, terminal P high-energy injection, photoresist removing and terminal P;
4, terminal N (4 th time) photoetching, terminal N injection, photoresist removal, BOE corrosion, RCA cleaning, diffusion oxidation promotion- (terminal N);
5 photo-etching the photosensitive region (5 th time), BOE etching the photosensitive region, RCA cleaning, sacrificial oxidation and the photosensitive region;
Photoetching a photosensitive region P (6 th time), injecting high-energy P, removing photoresist, annealing RTP, injecting N+ in the photosensitive region, annealing by laser, etching BOE, cleaning RCA, oxidizing at low temperature, and performing low-pressure chemical vapor deposition (Low Pressure Chemical Vapor Deposition, LPCVD) - - (photosensitive region P);
7, hole (7 th time) photoetching, hole BOE corrosion, photoresist removing and hole (punching on the oxide layer);
front side metallization-metal (8 th time) lithography-metal etching-photoresist removal-alloy- (front side metallization);
9 PI spin-coating- -PI (9 th time) lithography- -PI curing- - (PI);
Back thinning-back implant (layer 10) -laser annealing- (back implant);
back metal (11 th layer) -alloy-test (back metal).
In some embodiments, the guard ring has a plurality of guard rings, and the building the neutralizing layer on the substrate includes building the neutralizing layer on the substrate in a region between the guard ring nearest the cutoff ring and the cutoff ring.
In this embodiment, the above-described construction process is the same as the above-described step 230, except that the region between the guard ring closest to the stop ring and the guard ring is located when the lithography positioning is performed on the oxide layer. As shown in fig. 4, the neutralization layer in the figure is between the guard ring nearest the cutoff ring and the cutoff ring.
In some embodiments, building a neutralizing layer on the substrate includes:
A plurality of neutralizing layers are built up on the substrate at a regional spacing between the guard ring and the cutoff ring.
In this embodiment, the above construction process is the same as the above step 230, and will not be described here again. As shown in fig. 5, there are 2 neutralization layers between the guard rings.
The terminal structure is multi-section by constructing a plurality of neutralization layers, so that more parts are transferred from the surface to the inside of the body from the area with high ion concentration, the surface electric field is further reduced, the surface leakage current is reduced, and the transverse withstand voltage of the device is improved.
In some embodiments, the guard ring has a plurality, and the building of the neutralization layer on the substrate includes:
firstly, constructing a neutralization layer on the area between the protection ring closest to the cut-off ring and the cut-off ring on the substrate;
then, a neutralization layer is respectively constructed in the area between any two protection rings on the substrate.
The above construction is the same as the step 230, except that in performing photolithographic positioning on the oxide layer, one is in the region between the guard ring nearest to the stop ring and the stop ring, and the other is in the region between any two guard rings. As shown in fig. 6, one neutralization layer is between the guard rings and the cutoff ring, and the other neutralization layer is between the two guard rings.
One neutralization layer is positioned between the guard ring nearest to the cut-off ring and the cut-off ring, and the other neutralization layers are respectively positioned between the two guard rings, so that a plurality of diode structures can be formed. By forming a plurality of diode structures, the voltage dividing capability of the device can be improved, and the transverse voltage withstand of the device is further improved.
In some embodiments, the ions in the neutralization layer are P-ions, and constructing the neutralization layer on the substrate includes:
Firstly, an N-type structure is constructed in a region between the protection ring and the stop ring on the substrate;
Then, photoetching is carried out on the N-type structure, and a second dopant is implanted into the substrate to form a second terminal doped region, wherein the second dopant is P-ion;
and finally, removing photoresist from the substrate on which the second terminal doped region is formed, and exposing the second terminal doped region to obtain a neutralization layer.
In this embodiment, in the case where the anti-inversion terminal is a P anti-inversion terminal, the neutralization layer is doped with N to obtain an N-neutralization layer, and correspondingly, in the case where the ion in the neutralization layer is a P-ion, an N-type structure is arranged on the P anti-inversion terminal, and then a P-neutralization layer, i.e., the neutralization layer is doped with P-ion, is arranged on the N-type structure. As shown in fig. 7, an N-type structure is first built on the anti-inversion terminal, and then a P-neutralization layer is built on the N-type structure to form a neutralization layer.
And an N-type structure is constructed between the protection ring and the cut-off ring, and the neutralization layer is positioned on the N-type structure, so that the terminal structure exchanged by NPs can be realized.
It should also be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises an element.
The foregoing is merely exemplary of the present application and is not intended to limit the present application. Various modifications and variations of the present application will be apparent to those skilled in the art. Any modification, equivalent replacement, improvement, etc. which come within the spirit and principles of the application are to be included in the scope of the claims of the present application.
Claims (11)
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| EP0675549A1 (en) * | 1994-03-22 | 1995-10-04 | Nec Corporation | Superlattice avalanche photodiode |
| TW202230825A (en) * | 2021-01-29 | 2022-08-01 | 弗勞恩霍夫爾協會 | Photodiode with orthogonal layer structure |
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| FR3027156A1 (en) * | 2014-10-10 | 2016-04-15 | St Microelectronics Crolles 2 Sas | LOW DARK CURRENT PHOTODIODE |
| CN110176501A (en) * | 2019-05-30 | 2019-08-27 | 深圳市美浦森半导体有限公司 | A kind of preparation method of MPS structure process silicon carbide diode |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| EP0675549A1 (en) * | 1994-03-22 | 1995-10-04 | Nec Corporation | Superlattice avalanche photodiode |
| TW202230825A (en) * | 2021-01-29 | 2022-08-01 | 弗勞恩霍夫爾協會 | Photodiode with orthogonal layer structure |
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