CN109755114B - Two-way TVS chip glass blunt front double-sided diffusion process - Google Patents
Two-way TVS chip glass blunt front double-sided diffusion process Download PDFInfo
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- CN109755114B CN109755114B CN201711059126.6A CN201711059126A CN109755114B CN 109755114 B CN109755114 B CN 109755114B CN 201711059126 A CN201711059126 A CN 201711059126A CN 109755114 B CN109755114 B CN 109755114B
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Abstract
The invention discloses a two-way TVS chip double-sided diffusion process before glass passivation, which comprises the following steps: s1, double-sided diffusion, wherein the surface of the silicon wafer is covered with a diffusion source and diffused; s2 texturing is carried out, so that the roughness of the surface of the silicon wafer is increased, and a coating foundation is provided for coating of protective glue in the subsequent glass passivation process of the silicon wafer. The invention has the advantages that the boron diffusion sources are printed on the two sides of the silicon wafer by adopting the screen printing process, so that the coating flow of the liquid source of the silicon wafer is simplified, and the processing period is shortened; the negative pressure diffusion process is adopted after the liquid source is coated, the source return situation of the edge of the silicon wafer is reduced, the diffusion process steps are simplified, and the diffusion efficiency is improved; the manufactured PN junction is uniform, so that the processing cost of the silicon wafer is reduced.
Description
Technical Field
The invention belongs to the field of manufacturing processes of silicon wafers, and particularly relates to a two-sided diffusion process of a bidirectional TVS chip before glass passivation.
Background
A tvs (transient Voltage suppressor) diode, also called a transient suppressor diode, is a commonly used novel high-efficiency circuit protection device, has extremely fast response time (sub-nanosecond level) and relatively high surge absorption capability, and is used in combination with components such as a resistor and a capacitor to perform transient high-Voltage suppression protection. When the two ends of the TVS are subjected to transient high-energy impact, the TVS can change the impedance value between the two ends from high impedance to low impedance at a very high speed so as to absorb a transient large current and clamp the voltage between the two ends of the TVS at a preset value, thereby protecting the following circuit elements from the impact of transient high-voltage spike pulse. The TVS is widely applied to various protective electronic circuits, and has wide market prospect and larger development space.
At present, the manufacture of silicon wafers in the industry mostly adopts a diffusion process to form PN junctions, the common diffusion process in the industry generally adopts one-time full diffusion of a paper source, and as the gap between the silicon wafers after the paper source is sintered is increased, the volatile phosphorus source is diffused to a boron surface to cause source return; the method adopted by the silicon wafer texturing is dry sanding texturing, quartz sand is sprayed out at a high speed to polish the surface of the silicon wafer, and the roughness of the surface of the silicon wafer is increased. However, the silicon wafer subjected to dry sanding texturing has the obvious defects that the silicon wafer subjected to dry sanding texturing is subjected to large stress, so that the silicon wafer is easy to break, the texturing effect is not obvious, the roughness is small, the process flow is complex, and the investment cost is high.
Disclosure of Invention
In order to solve the technical problem, the invention provides a two-sided diffusion process of a bidirectional TVS chip before glass passivation.
The invention provides a two-way TVS chip glass blunt front double-sided diffusion process, which comprises the following steps:
and S1, double-sided diffusion, wherein the surface of the silicon wafer is covered with a diffusion source and diffused.
Wherein, the step S1 is double-sided diffusion, and comprises the following steps:
s1-1, printing a boron diffusion source, printing the boron diffusion source on two sides of the silicon wafer by adopting a screen printing technology, and drying the printed silicon wafer;
s1-2, spraying Al2O3 powder or silicon powder on two surfaces of the silicon wafer;
s1-3, performing negative pressure diffusion, placing the silicon wafer in a diffusion furnace, and pumping the air pressure in the diffusion furnace to a negative pressure;
preferably, the negative pressure diffusion is constant temperature diffusion, and the diffusion temperature is 1250-1300 ℃.
Wherein the step S1, the double-sided diffusion, specifically, is: and depositing a phosphorus source on the surface of the silicon wafer in a mode of carrying phosphorus oxychloride by using nitrogen for phosphorus diffusion.
And step S1, performing texturing after double-sided diffusion, wherein the texturing is wet-process texturing or laser texturing.
Preferably, the wet-method texturing specifically comprises the steps of:
A1. performing diffusion post-treatment, and removing phosphorus borosilicate glass on the surface of the diffused silicon wafer;
A2. placing the treated silicon wafer in a first-stage cleaning solution at 50-70 ℃ for 3-10min, and cleaning with pure water for 10-20 min;
A3. placing the silicon wafer in a second-stage cleaning solution at the temperature of 70-90 ℃ for 20-30min, and cleaning with pure water for 10-20 min;
A4. placing the silicon wafer in a second-stage cleaning solution at 70-90 ℃ for 3-10min, and cleaning with pure water for 10-20 min;
A5. and spin-drying the cleaned silicon wafer, and testing the surface roughness.
Preferably, the first-stage cleaning liquid is a solution formed by mixing hydrogen peroxide, pure water and 30% by mass of potassium hydroxide solution according to the volume ratio of 6-10:110-120: 1-8;
preferably, the second-stage cleaning solution is a solution formed by mixing a potassium hydroxide solution with the mass fraction of 10-30%, a texturing additive and pure water according to the volume ratio of 0.35-0.42:0.04-0.09: 5-10;
preferably, the third-stage cleaning liquid is a solution formed by mixing hydrofluoric acid, hydrochloric acid and pure water according to a volume ratio of 10-15:30-40: 60-80.
Preferably, the laser texturing specifically includes the following steps:
B1. removing the silicon wafer surface forming layer after diffusion: placing the diffused silicon wafer in a glass corrosive liquid for 3-10min, and cleaning and spin-drying the silicon wafer;
B2. laser texturing: scanning the cleaned silicon wafer on the surface of the silicon wafer by using laser, and making the smooth surface of the silicon wafer into a rough surface;
B3. cleaning after texturing: and after the silicon wafer is subjected to texturing, the silicon wafer is soaked and cleaned in an HF solution, and after the HF solution is cleaned, overflow cleaning and spin-drying are carried out.
Preferably, the glass corrosion liquid is a solution formed by mixing ammonium hydrofluoride, oxalic acid, ammonium sulfate, glycerol, barium sulfate and hot pure water according to the volume ratio of 6-10:8-15:20-30:4-15:10-22: 110-120.
Preferably, the step S1 includes a step of diffusion pretreatment before the double-sided diffusion, specifically:
C1. putting the silicon wafer into a corrosive liquid at 0-15 ℃ for corrosion for 9-50s, so that the double surfaces of the silicon wafer are thinned; cleaning with pure water for 10-20min, and cleaning with corrosive liquid;
C2. treating the silicon wafer in 40-80 deg.C alkali solution for 5-20 min;
C3. two-stage overflow cleaning; primary ultrasonic overflow cleaning; two-stage overflow cleaning; the cleaning time of each stage is 5-20 min;
C4. placing the silicon wafer in 60-100 deg.C acid solution for three-stage acid treatment, wherein the treatment time at each stage is 5-20 min; C5. four-stage overflow cleaning, wherein the cleaning time of each stage is 5-20 min;
preferably, the corrosive liquid is a solution formed by mixing nitric acid, hydrofluoric acid, glacial acetic acid and pure water according to the volume ratio of 10-20:5-10:1-10: 1-10;
preferably, the alkali liquor is potassium hydroxide solution; the acid solution is nitric acid solution.
The invention has the advantages and positive effects that: the bidirectional TVS chip has high required concentration on the phosphorus diffusion source, and the printing process cannot reach the required concentration, so that the phosphorus source is not coated by adopting a screen printing process; the boron diffusion sources are printed on the two sides of the silicon wafer by adopting a screen printing process, so that the coating flow of the liquid source of the silicon wafer is simplified, and the processing period is shortened; the negative pressure diffusion process is adopted after the liquid source is coated, the source return condition of the edge of the silicon wafer is reduced, the diffusion process steps are simplified, the diffusion efficiency is improved, the manufactured PN junctions are uniform, the processing cost of the silicon wafer is reduced, wet-method texturing or laser texturing is adopted to replace the traditional dry-method sanding, the wormhole-shaped suede is manufactured on the surface of the silicon wafer, the roughness of the surface of the silicon wafer is increased, the coating of a subsequent glass passivation process protective layer of the silicon wafer is facilitated, and the adhesive force is increased when the protective layer is coated in the glass passivation process.
Detailed Description
In order to make the technical problems, technical solutions and advantageous effects to be solved by the present invention more apparent, embodiments of the present invention are specifically described below.
The scheme relates to a two-sided diffusion process method before the glass passivation of a bidirectional TVS chip, which comprises two-sided diffusion and wool making, and specifically comprises diffusion pretreatment, phosphorus diffusion (boron diffusion), diffusion aftertreatment and wool making.
The method specifically comprises the following steps:
first, diffusion pretreatment
1) Annealing and cleaning a silicon wafer: annealing and cleaning the cut silicon wafer to remove surface dirt and reduce mechanical damage to the silicon wafer during cutting;
2) thinning the double surfaces of the silicon wafer: the method comprises the following steps of performing double-sided corrosion on a silicon wafer by using a corrosive liquid to remove a surface damage layer:
a. measuring the temperature of the corrosive liquid by a thermometer, wherein the temperature is generally 0-15 ℃, setting the corrosion time of the silicon wafer according to the temperature of the corrosive liquid, wherein the corrosion time is generally 9-50s, determining the corrosion time according to the temperature of the corrosive liquid, placing the silicon wafer into the corrosive liquid for corrosion thinning, and determining the thickness of the thinned double surfaces of the silicon wafer according to the temperature of the corrosive liquid, wherein the thickness is generally 10-20 mu m;
b. after the corrosion is finished, the silicon wafer is placed into a pure water cleaning tank for cleaning, the corrosive liquid in the corrosion thinning process is cleaned, and the cleaning time is 10-20 min;
c. measuring the silicon wafer deduction amount: after the silicon wafer is cleaned, an instrument is used for measuring whether the removal amount of the silicon wafer meets the standard, wherein the measuring instrument used here is a screw micrometer, and can also be other instruments for measuring the thickness, namely, the thickness of the thinned double surfaces of the silicon wafer is measured, and the thickness is generally 10-20 mu m;
d. and after the measurement, carrying out overflow cleaning on the silicon wafer, wherein the purpose of the overflow cleaning is to remove impurities on the surface of the thinned silicon wafer.
The etching solution is prepared by mixing nitric acid, hydrofluoric acid, glacial acetic acid and pure water according to a certain proportion, and the etching solution can etch and thin the silicon wafer well, wherein the mixing proportion is mixing according to a volume proportion and mixing according to a volume proportion of 10-20:5-10:1-10: 1-10.
3) And (3) sequentially processing the thinned silicon wafer: the thinned silicon chip is sequentially subjected to alkali treatment, overflow cleaning, acid cleaning, overflow cleaning and spin-drying, so as to remove mechanical damage on the surface of the silicon chip and remove impurities such as metal ions, organic solvents and the like on the surface of the silicon chip, namely,
a. placing the thinned silicon wafer in alkali liquor for treatment, wherein the alkali liquor is potassium hydroxide solution, the temperature of the potassium hydroxide solution is 40-80 ℃, the alkali treatment time is within 5-20min, and the alkali treatment is primary alkali treatment, namely primary alkali treatment is carried out;
b. after the alkali treatment is finished, putting the silicon wafer into pure water for overflow cleaning to remove alkali liquor on the surface of the silicon wafer, wherein the cleaning comprises three steps, firstly, overflow cleaning is adopted, the overflow cleaning adopts two-stage overflow cleaning, ultrasonic overflow cleaning is adopted after the two-stage overflow cleaning, the ultrasonic overflow cleaning adopts one-time ultrasonic overflow cleaning, the overflow cleaning is adopted after the ultrasonic overflow cleaning, the two-stage overflow cleaning is adopted, the cleaning time of each step is within 5-20min, the two-stage overflow cleaning refers to that the silicon wafer is subjected to two-time water cleaning to fully remove other solution impurities on the surface of the silicon wafer, and the one-stage ultrasonic overflow cleaning refers to one-time ultrasonic overflow cleaning;
c. placing the cleaned silicon wafer in an acid solution for acid treatment, wherein the acid solution used for the acid treatment is a nitric acid solution, the temperature of the nitric acid is 60-100 ℃, the acid treatment time is within 5-20min, the acid treatment is a three-stage acid treatment, namely, the three-stage acid treatment is carried out, and the acid treatment time is the same for each time;
d. after the acid treatment is finished, putting the silicon wafer into pure water for overflow cleaning to remove acid liquor on the surface of the silicon wafer, wherein the overflow cleaning time is within 5-20min, the overflow cleaning is four-stage overflow cleaning, namely, four times of overflow cleaning is carried out, and the time for each overflow cleaning is the same;
e. and spin-drying the cleaned silicon wafer, so that impurities such as water and the like cannot exist on the surface of the silicon wafer.
Two-sided diffusion
According to different types of products, when the type of the silicon wafer is a P-type bidirectional TVS chip, phosphorus diffusion texturing is performed on the two sides of the silicon wafer; and when the type of the silicon chip is an N-type bidirectional TVS chip, the two sides of the silicon chip are subjected to boron diffusion texturing.
Phosphorus diffusion: aiming at the P-type bidirectional TVS chip, because the P-type bidirectional TVS chip has high requirement concentration on the phosphorus diffusion source and the printing process can not reach the required concentration, the phosphorus source is coated without adopting the screen printing process.
41) And when the temperature of the phosphorus diffusion furnace reaches 1000 ℃, pushing the silicon wafer to be subjected to phosphorus diffusion to a constant temperature region, depositing a phosphorus source on the surface of the silicon wafer in a mode of carrying phosphorus oxychloride by nitrogen when the temperature is increased to 1200 ℃, and discharging the silicon wafer after phosphorus diffusion is carried out for 2 hours.
B, boron diffusion: aiming at an N-type bidirectional TVS chip;
42) double-sided printing of boron diffusion source: the method is characterized in that a phosphorus and boron source is diffused and coated on a silicon wafer by adopting a screen printing technology, the diffusion source is coated on the surface of the silicon wafer by adopting a screen printing process, the screen printing is a principle of realizing continuous plate separation by utilizing screen plate tension, and the printing comprises three elements: ink (paste), doctor blade, screen; the ink (slurry) consists of a functional component, a bonding component and an organic carrier, and has the following characteristics: viscosity, a property that impedes the flow of a fluid substance, is a measure of the ability of the fluid to interact with molecules to produce an inhibition of relative movement between the molecules; yield value, the force that the ink is subjected to must be greater than a certain value to flow; thixotropy, the ink is changed from thick to thin along with stirring action when being stirred by external force, and when the stirring action is stopped, the original consistency is recovered again; the fluidity of the ink is determined by the viscosity, yield value and thixotropy of the ink, and the ink can flow like a liquid under the action of the gravity of the ink.
In addition, the scraper is used for pressing the pulp into the leaking holes of the silk screen at a certain speed and at a certain angle, and the scraper keeps a certain pressure on the silk screen during printing to ensure that the pulp is pressed into the leaking holes of the silk screen, and is generally made of polyurethane rubber or fluorinated rubber.
The factors of the scraper influencing the printing effect are as follows: the hardness of the scraper is lower, the thickness of a printed pattern is larger, and the scraper material must ensure that the cutting edge has good linearity; the screen is easy to deform due to overlarge pressure of the scraper, the printed patterns are inconsistent, the abrasion of the scraper and the screen is also aggravated, and residual slurry exists on the printed screen due to the overlarge pressure of the scraper; the scraper speed is set according to the printing pattern and the viscosity of printing slurry, and the higher the speed is, the shorter the time for the slurry to enter the mesh is, and the poorer the filling property is; the scraper angle is set to be related to the slurry, the higher the viscosity value of the slurry is, the poorer the fluidity is, the larger the downward pressure of the slurry to be scraped by the scraper is, and the smaller the scraper angle is; the angle adjusting range of the common scraper is 45-75 degrees.
Screens play an important role in screen printing: the screen is a support for the emulsion required for pattern formation; meanwhile, the output of the printing ink when penetrating through the screen can be controlled by utilizing the silk screen; ideal plate separation is realized by utilizing the tension of the screen printing plate; the screen thickness determines the print thickness. This requires the wire mesh to have some strength: the most ideal screen printing plate has the characteristics of high strength and difficult deformation, the types of the screen printing plates required by different printing effects are different, in the embodiment, a diffusion source is printed on the surface of a silicon wafer, a precision screen with middle strength and medium and low extensibility is adopted, the tensile strength of the material used by the screen is 30-40% higher than that of a standard tension material, and the screen printing plate has high dimensional accuracy stability and brushing resistance.
The method for printing the boron diffusion source on the two sides of the silicon wafer by adopting a screen printing process specifically comprises the following steps:
a. printing a boron diffusion source on one side of a silicon wafer: spraying a boron diffusion source on a screen printing plate, wherein the screen printing plate is woven by engineering plastics, placing a silicon wafer below the screen printing plate, applying pressure at a certain angle from the upper part of the screen printing plate by using a scraper, and printing the boron diffusion source on the surface of the silicon wafer, wherein the angle of the scraper is 40-90 degrees, the printing pressure is 30N-120N, the plate interval is 1-3mm, the printing speed is 50-300mm/S, the height of the scraper is 1-3mm, and the hardness of the scraper is 40-80 HRC;
b. placing the silicon wafer printed with the boron diffusion source in a drying oven, and drying the boron diffusion source, wherein the drying time is determined according to the printing amount of the boron diffusion source, the drying time is generally 1-30min, and the temperature is 90-180 ℃;
c. b, printing a boron diffusion source on the other surface of the silicon wafer according to the process steps of the step a and the step b, and baking, wherein the baking time is determined according to the printing amount of the boron diffusion source, the baking time is 1-30min generally, and the temperature is 90-180 ℃;
d. after baking, spraying Al2O3 powder or silicon powder on two sides of the silicon wafer.
52) Stacking sheets and loading into a boat: the silicon wafers are stacked pairwise oppositely and are loaded into a boat, namely, the boron source surface and the boron source surface of the silicon wafers are stacked oppositely, the silicon wafers are placed into a silicon carbide boat after being stacked, and blocking pieces are placed at the front and rear positions of the silicon carbide boat to tightly press the silicon wafers, so that the space in a diffusion furnace can be fully utilized after negative pressure diffusion is carried out, the working efficiency is high, and multiple batches of silicon wafers can be diffused at one time;
62) negative pressure diffusion: carrying out negative pressure diffusion on the silicon wafer loaded in the carbonization boat in a diffusion furnace to manufacture uniform PN junctions; wherein, the specific steps of negative pressure diffusion in the step are as follows:
a. placing the carbonization boat with the silicon chip in a diffusion furnace, placing the carbonization boat in a constant temperature area of the diffusion furnace, closing a furnace door, and pumping the air pressure in the diffusion furnace to negative pressure, generally 10-101Kpa, by using a vacuum pump;
b. raising the temperature of the diffusion furnace from 550-650 ℃ to 1250-1300 ℃ for constant-temperature diffusion for 10-20 h;
c. after the diffusion is finished, the temperature of the diffusion furnace is reduced to 550-650 ℃, and the carbonization boat containing the silicon wafer is pulled out of the diffusion furnace.
Third, texturing
The texturing step comprises
7) Diffusion post-treatment
8) Texturing the surface of a silicon wafer:
if the wet-method texture surface making is adopted, the specific steps comprise the following steps:
71) and (3) diffusion post-treatment: and (3) placing the diffused silicon wafer in acid for diffusion post-treatment, flushing the separated silicon wafer with water, cleaning the surface with mixed acid, and removing phosphorus and borosilicate glass on the surface of the diffused silicon wafer. The acid used for the diffusion post-treatment in the step is hydrofluoric acid solution, and the mixed acid for cleaning the surface of the silicon wafer is nitric acid, hydrofluoric acid, glacial acetic acid and pure water which are mixed according to a certain proportion, wherein the certain proportion is mixed according to the volume proportion of 1000-3000:300-800:100-400: 1000-3000.
81) Texturing the surface of a silicon wafer: the surface of the silicon wafer can be subjected to wet texturing or laser texturing.
When the wet-process texturing process is adopted, before texturing, phosphorus and borosilicate glass on the surface of a silicon wafer subjected to diffusion treatment are removed by adopting high-temperature water vapor and hydrofluoric acid, and then the wet-process texturing is adopted, and the method specifically comprises the following steps:
a. stacking the silicon chip single sheets after the diffusion post-treatment on a silicon carbide boat, wherein the silicon carbide boat is subjected to oxidation treatment and is provided with a clamping groove, and placing the silicon chip-loaded silicon carbide boat on a quartz pipe orifice;
b. slowly pushing the silicon carbide boat into a constant temperature area by using a furnace hook, and covering a quartz furnace cap;
c. starting a starting program of the oxidation furnace and starting a timer;
d. sounding a buzzer, closing a timer, starting a water vapor generator, starting heating, pressing a timer switch again, sounding the buzzer, closing the timer, closing a nitrogen switch, raising the temperature of an oxidation furnace to 1080-;
e. after the silicon carbide boat is taken out, the silicon carbide boat is placed on a stainless steel platform and fully cooled to room temperature, the purification workbench is started in the process, and the high-efficiency function is adopted, so that the air in the purification workbench is filtered and purified, and other impurities are prevented from being mixed when the silicon wafer is cooled;
f. taking out the cooled silicon wafer from a silicon carbide boat, placing the silicon wafer in a container, wherein the container is a flower basket and is used for containing the silicon wafer, the marking surface of the silicon wafer is also towards the U-shaped surface of the flower basket, soaking the flower basket in a tank filled with 49% hydrofluoric acid solution for 5-15 minutes, taking out the flower basket, placing the flower basket in a water tank, flushing and spin-drying the flower basket, and removing a damaged layer on the surface of the oxidized silicon wafer;
g. preparing a corrosion cleaning solution: respectively preparing a first-stage cleaning solution, a second-stage cleaning solution and a third-stage cleaning solution, and preparing for making wool, specifically comprising the following steps:
g1. weighing a proper amount of potassium hydroxide, and preparing a potassium hydroxide solution with the mass fraction of 10-30%;
g2. preparing a first-stage cleaning solution: mixing hydrogen peroxide, pure water and 10-30% of potassium hydroxide solution according to the volume ratio of 6-10:110-120:1-8 to prepare a first-stage cleaning solution;
g3. preparing a second-stage cleaning solution: mixing the prepared potassium hydroxide solution with the mass fraction of 10-30%, the texturing additive and pure water according to the volume ratio of 0.35-0.42:0.04-0.09:5-10 to prepare a second-stage cleaning solution;
g4. preparing a third-stage cleaning solution: mixing hydrofluoric acid, hydrochloric acid and pure water according to the volume ratio of 10-15:30-40:60-80 to prepare a third-stage cleaning solution.
h. Pouring the prepared etching cleaning solution into a corresponding cleaning tank, and setting the temperature of the cleaning tank, namely,
h1. pouring the prepared first-stage cleaning solution into a first-stage cleaning tank, starting a heating device, and setting the temperature to be 50-70 ℃;
h2. pouring the prepared second-stage cleaning solution into a second-stage cleaning tank, starting a heating device, and setting the temperature to be 70-90 ℃;
h3. and pouring the prepared third-stage cleaning solution into a third-stage cleaning tank.
i. Placing the silicon chip with the glass removed in a flower basket, wherein the marking surface of the silicon chip is also towards the U-shaped surface of the flower basket;
j. when the temperature of each stage of cleaning tank reaches a set value, placing the flower basket containing the silicon wafers into a first stage cleaning tank, taking out the flower basket containing the silicon wafers after 3-10min, placing the flower basket into a water tank for flushing for 10-20min, wherein the flushing time is to remove the first stage cleaning solution on the surfaces of the silicon wafers;
k. placing the flower basket filled with the silicon wafers after being flushed into a second-stage cleaning tank, taking out the flower basket after 20-30min, placing the flower basket into a water tank, and flushing for 10-20min, wherein the flushing purpose is to remove second-stage cleaning liquid on the surfaces of the silicon wafers;
putting the washed flower basket into a third-stage washing tank, taking out the flower basket with the silicon wafers after 3-10min, putting the flower basket into a water tank, and washing for 10-20min, wherein the purpose of washing is to remove third-stage washing liquid on the surfaces of the silicon wafers;
and m, spin-drying the cleaned silicon wafer, and testing the surface roughness.
As can be known from test data, the wet-process texturing effect is obvious, the surface roughness of the silicon wafer before texturing is 0.596, and the surface roughness of the silicon wafer after texturing is 0.832.
If the laser texturing is adopted, the specific steps comprise the following steps:
72) and (3) diffusion post-treatment: the method comprises the following steps of forming a layer of forming layer on the surface of a diffused silicon wafer, wherein the forming layer is made of phosphorus and borosilicate glass, removing the phosphorus and borosilicate glass on the surface of the diffused silicon wafer by using glass corrosive liquid, corroding the phosphorus and borosilicate glass formed after the liquid diffusion source of the silicon wafer is diffused by using the glass corrosive liquid, and preparing for next laser texturing, and specifically comprises the following steps:
a. soaking the diffused silicon wafer in a glass corrosive liquid for 0.5-4h to remove phosphorus and borosilicate glass on the surface of the diffused silicon wafer, wherein the glass corrosive liquid is prepared by mixing ammonium hydrofluoride, oxalic acid, ammonium sulfate, glycerol, barium sulfate and hot pure water according to a certain proportion, and the mixing proportion is 20-30% by weight: 10-20%: 10-20%: 0-10%: 20-30%: mixing at a ratio of 10-20%.
b. Ultrasonic cleaning is carried out on the silicon wafer soaked with the glass corrosive liquid, the glass corrosive liquid on the surface of the silicon wafer is removed, meanwhile, phosphorus and borosilicate glass on the surface of the silicon wafer, which are incompletely reacted with the glass corrosive liquid, are removed by ultrasonic waves, wherein the ultrasonic cleaning is carried out on the silicon wafer soaked with the corrosive liquid for one time, and the ultrasonic cleaning time is generally 5-30 min;
c. washing the silicon wafer subjected to ultrasonic cleaning with water, further washing the glass corrosive liquid possibly remained on the surface of the silicon wafer, wherein only one-time overflow washing is carried out, namely, the silicon wafer subjected to ultrasonic cleaning is placed in a water tank for one-time flushing, and is taken out after the flushing, and the one-time overflow washing time is generally 5-30 min;
d. cleaning the silicon wafer after the overflow cleaning in the previous step with nitric acid to further remove residual impurities on the surface of the silicon wafer, namely, cleaning the silicon wafer in nitric acid, wherein the time for cleaning with nitric acid is generally 5-30 min;
e. washing the silicon wafer cleaned by nitric acid with water, diluting and washing the nitric acid on the surface of the silicon wafer in the previous step to remove the nitric acid, and performing four-time overflow washing on the silicon wafer cleaned by nitric acid, namely sequentially putting the silicon wafer cleaned by nitric acid into four water tanks for flushing, wherein the four-stage overflow washing time is generally 5-30 min;
f. and (5) drying the silicon wafer after the overflow cleaning by using a drying machine.
82) Texturing the surface of a silicon wafer: the laser texturing is to respectively perform laser texturing on two sides of a silicon wafer, and the cleaned silicon wafer is scanned on the surface of the silicon wafer by using laser, and the method comprises the following specific steps: the cleaned silicon wafer is placed on a working platform of a laser, the laser is applied to scan the surface of the silicon wafer, when the laser scans, the laser beam of the laser linearly scans from left to right, and the laser beam is sequentially linearly and linearly scanned on the surface of the silicon wafer from top to bottom, and the whole surface of the silicon wafer is completely scanned once, namely, when the laser beam of the laser is scanned on the surface of the silicon wafer, controlling the diameter of a light spot formed by a laser beam to be 10-80 mu m, firstly carrying out linear scanning on the surface of the silicon wafer in the transverse direction, after one transverse scanning is finished, the laser beam moves downwards, and transverse linear scanning is continuously carried out next to the transverse direction which is finished by scanning, namely, the laser beam sequentially carries out a plurality of times of transverse scanning in the longitudinal direction, and a scanning track is formed on the surface of the silicon wafer; after one surface of the silicon wafer is scanned, the silicon wafer is turned over, and the other surface of the silicon wafer is scanned and subjected to texturing, namely, the two surfaces of the silicon wafer are both subjected to laser scanning, and the two surfaces of the silicon wafer are subjected to texturing.
The principle of laser texturing is as follows: the laser beam irradiates on the silicon wafer, the surface of the silicon wafer is in a molten state due to the high-temperature action of the facula of the laser beam and the high-temperature action of the laser beam, and after the silicon wafer is scanned, the silicon wafer is cooled to form molten polysilicon crystals on the surface of the silicon wafer.
The silicon chip is when through laser scanning, the laser beam of laser instrument assembles on the laser surface, because the high temperature effect of laser, make the silicon chip surface take place the phenomenon of melting, the back is scanned to the light beam of laser instrument, silicon chip surface molten state forms melting polycrystalline silicon through the cooling, make the silicon chip through the scanning back, make unevenness's melting polycrystalline silicon on the silicon chip surface, make the roughness on silicon chip surface increase, coating that the protection was glued in the technology of follow-up glass blunt of silicon chip provides the coating basis, make the protection glue adhesive force increase when the coating, be difficult for droing.
The silicon wafer is scanned by laser, the surface of the silicon wafer forms a molten state due to the action of high temperature, so that the removal amount of the silicon wafer reaches 4-5 mu m, and the monocrystalline silicon on the surface of the whole silicon wafer is made into rugged molten polycrystalline silicon by laser. Meanwhile, laser scanning can remove phosphorus and borosilicate glass on the surface of the silicon wafer, which are not removed by the glass etching solution.
During laser scanning, the used laser is an infrared laser or other lasers, and can be selected according to production requirements, the laser frequency of the laser is 0.1MHz-1MHz, the power is 10-50W, the scanning speed of the laser is 3-40m/s, the smooth surface of the silicon wafer is made into a rough surface, and the roughness of the surface of the silicon wafer is improved from 0.3m to 0.5-1.5 mu m; and when the silicon wafer is subjected to laser scanning, the silicon wafer is placed on a working platform of a laser, the silicon wafer is fixed and placed, the silicon wafer is placed in the air at normal temperature and normal pressure, the laser is applied to scan the surface of the silicon wafer, namely, the silicon wafer is not limited by the environment by applying the laser scanning, so that the silicon wafer texturing process is simplified, the equipment investment is reduced, and the silicon wafer texturing process is simple, convenient to operate and simple in texturing.
Cleaning after texturing: the method comprises the steps of soaking and cleaning with an acid solution, performing two-stage overflow cleaning after the acid solution is cleaned, and performing spin-drying, wherein the acid solution is a hydrofluoric acid solution, and the purpose of cleaning is to clean impurities generated on the surface of a silicon wafer scanned by laser.
After the laser texturing process, a layer of rugged polysilicon is respectively attached to two surfaces of the silicon wafer, so that the monocrystalline silicon wafer with the polysilicon attached to the surface is formed.
After the steps, phosphorus and borosilicate glass on the surface of the silicon wafer after diffusion treatment are removed by using a glass corrosive liquid prepared according to a certain proportion, the surface of the silicon wafer is subjected to texturing by using a laser texturing method, and the surface of the silicon wafer is subjected to roughness test after texturing is finished, so that the surface roughness of the silicon wafer before texturing is 0.3m, the surface roughness of the silicon wafer after texturing is 0.5-1.5 mu m, the texturing effect is obvious, and the uniform surface roughness of the silicon wafer is prepared for coating a protective adhesive for a subsequent silicon wafer passivation process.
The invention has the advantages and positive effects that: the bidirectional TVS chip has high required concentration on the phosphorus diffusion source, and the printing process cannot reach the required concentration, so that the phosphorus source is not coated by adopting a screen printing process; the boron diffusion sources are printed on the two sides of the silicon wafer by adopting a screen printing process, so that the coating flow of the liquid source of the silicon wafer is simplified, and the processing period is shortened; the negative pressure diffusion process is adopted after the liquid source is coated, the source return condition of the edge of the silicon wafer is reduced, the diffusion process steps are simplified, the diffusion efficiency is improved, the manufactured PN junctions are uniform, the processing cost of the silicon wafer is reduced, wet-method texturing or laser texturing is adopted to replace the traditional dry-method sanding, the wormhole-shaped suede is manufactured on the surface of the silicon wafer, the roughness of the surface of the silicon wafer is increased, the coating of a subsequent glass passivation process protective layer of the silicon wafer is facilitated, and the adhesive force is increased when the protective layer is coated in the glass passivation process.
While one embodiment of the present invention has been described in detail, the description is only a preferred embodiment of the present invention and should not be taken as limiting the scope of the invention. All equivalent changes and modifications made within the scope of the present invention shall fall within the scope of the present invention.
Claims (5)
1. The utility model provides a two-way TVS chip glass blunt preceding two-sided diffusion technology which characterized in that includes the following step:
s1, double-sided diffusion, wherein the surface of the silicon wafer is covered with a diffusion source and diffused;
the step S1 comprises the step of diffusion pretreatment before double-sided diffusion, and specifically comprises the following steps:
C1. putting the silicon wafer into a corrosive liquid at 0-15 ℃ for corrosion for 9-50s, so that the double surfaces of the silicon wafer are thinned; cleaning with pure water for 10-20min, and cleaning with corrosive liquid;
C2. treating the silicon wafer in 40-80 deg.C alkali solution for 5-20 min;
C3. two-stage overflow cleaning; primary ultrasonic overflow cleaning; two-stage overflow cleaning; the cleaning time of each stage is 5-20 min;
C4. placing the silicon wafer in 60-100 deg.C acid solution for three-stage acid treatment, wherein the treatment time at each stage is 5-20 min;
C5. four-stage overflow cleaning, wherein the cleaning time of each stage is 5-20 min;
the corrosive liquid is a solution formed by mixing nitric acid, hydrofluoric acid, glacial acetic acid and pure water according to the volume ratio of 10-20:5-10:1-10: 1-10;
the step S1 is double-sided diffusion and comprises the following steps:
s1-1, printing a boron diffusion source, printing the boron diffusion source on two sides of the silicon wafer by adopting a screen printing technology, and drying the printed silicon wafer;
s1-2, spraying Al2O3 powder or silicon powder on two surfaces of the silicon wafer;
s1-3, performing negative pressure diffusion, placing the silicon wafer in a diffusion furnace, and pumping the air pressure in the diffusion furnace to a negative pressure; the negative pressure diffusion comprises the following specific steps:
a. placing the carbonization boat with the silicon chip in a diffusion furnace, placing the carbonization boat in a constant temperature area of the diffusion furnace, closing a furnace door, and pumping the air pressure in the diffusion furnace to a negative pressure by using a vacuum pump, wherein the negative pressure is 10-101 Kpa;
b. raising the temperature of the diffusion furnace from 550-650 ℃ to 1250-1300 ℃ for constant-temperature diffusion for 10-20 h;
c. after the diffusion is finished, the temperature of the diffusion furnace is reduced to 550-650 ℃, and the carbonization boat containing the silicon wafer is pulled out of the diffusion furnace;
or the like, or, alternatively,
the step S1 is specifically that double-sided diffusion is carried out: depositing a phosphorus source on the surface of the silicon wafer in a mode of carrying phosphorus oxychloride by nitrogen for phosphorus diffusion;
the method comprises the step of S1, wherein the step of texturing is carried out after double-sided diffusion, the texturing is wet-process texturing or laser texturing, and the laser texturing specifically comprises the following steps:
B1. removing the silicon wafer surface forming layer after diffusion: placing the diffused silicon wafer in a glass corrosive liquid for 3-10min, and cleaning and spin-drying the silicon wafer; the glass corrosive liquid is a solution formed by mixing ammonium hydrofluoride, oxalic acid, ammonium sulfate, glycerol, barium sulfate and hot pure water according to the volume ratio of 6-10:8-15:20-30:4-15:10-22: 110-120;
B2. laser texturing: scanning the cleaned silicon wafer on the surface of the silicon wafer by using laser, making the smooth surface of the silicon wafer into a rough surface, and performing laser texturing on the two surfaces of the silicon wafer respectively to form uneven molten polycrystalline silicon crystals on the surface of the silicon wafer;
B3. cleaning after texturing: and after the silicon wafer is subjected to texturing, the silicon wafer is soaked and cleaned in an HF solution, and after the HF solution is cleaned, overflow cleaning and spin-drying are carried out.
2. The bidirectional TVS chip before blunting glass double-sided diffusion process of claim 1, wherein: the wet-process texturing specifically comprises the following steps:
A1. performing diffusion post-treatment, and removing phosphorus borosilicate glass on the surface of the diffused silicon wafer;
A2. placing the treated silicon wafer in a first-stage cleaning solution at 50-70 ℃ for 3-10min, and cleaning with pure water for 10-20 min;
A3. placing the silicon wafer in a second-stage cleaning solution at the temperature of 70-90 ℃ for 20-30min, and cleaning with pure water for 10-20 min;
A4. placing the silicon wafer in a third-stage cleaning solution at 70-90 ℃ for 3-10min, and cleaning with pure water for 10-20 min;
A5. and spin-drying the cleaned silicon wafer, and testing the surface roughness.
3. The bidirectional TVS chip before blunting double-sided diffusion process of claim 2, wherein: the first-stage cleaning solution is a solution formed by mixing hydrogen peroxide, pure water and 30% by mass of a potassium hydroxide solution according to a volume ratio of 6-10:110-120: 1-8; the second-stage cleaning solution is a solution formed by mixing a potassium hydroxide solution with the mass fraction of 10-30%, a texturing additive and pure water according to the volume ratio of 0.35-0.42:0.04-0.09: 5-10; the third-stage cleaning liquid is a solution formed by mixing hydrofluoric acid, hydrochloric acid and pure water according to the volume ratio of 10-15:30-40: 60-80.
4. The bidirectional TVS chip before blunting glass double-sided diffusion process of claim 1, wherein:
the alkali liquor is potassium hydroxide solution.
5. The bidirectional TVS chip before blunting glass double-sided diffusion process of claim 1, wherein: the acid solution is nitric acid solution.
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| CN101916786A (en) * | 2010-06-22 | 2010-12-15 | 南通明芯微电子有限公司 | High-power planar junction bidirectional TVS diode chip and production method thereof |
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| CN105304753A (en) * | 2015-09-25 | 2016-02-03 | 中国电子科技集团公司第四十八研究所 | N-type cell boron diffusion technology |
| CN105355654A (en) * | 2015-10-13 | 2016-02-24 | 上海瞬雷电子科技有限公司 | Low-voltage transient-suppression diode chip with low electric leakage and high reliability and production method |
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| CN101916786A (en) * | 2010-06-22 | 2010-12-15 | 南通明芯微电子有限公司 | High-power planar junction bidirectional TVS diode chip and production method thereof |
| CN104538501A (en) * | 2015-01-15 | 2015-04-22 | 中利腾晖光伏科技有限公司 | N-type double-sided battery and manufacturing method thereof |
| CN105304753A (en) * | 2015-09-25 | 2016-02-03 | 中国电子科技集团公司第四十八研究所 | N-type cell boron diffusion technology |
| CN105355654A (en) * | 2015-10-13 | 2016-02-24 | 上海瞬雷电子科技有限公司 | Low-voltage transient-suppression diode chip with low electric leakage and high reliability and production method |
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