CN115197706A - Acid etching solution, silicon wafer processing method and wafer packaging method - Google Patents
Acid etching solution, silicon wafer processing method and wafer packaging method Download PDFInfo
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- CN115197706A CN115197706A CN202210736451.6A CN202210736451A CN115197706A CN 115197706 A CN115197706 A CN 115197706A CN 202210736451 A CN202210736451 A CN 202210736451A CN 115197706 A CN115197706 A CN 115197706A
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- C09K13/00—Etching, surface-brightening or pickling compositions
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- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/02002—Preparing wafers
- H01L21/02005—Preparing bulk and homogeneous wafers
- H01L21/02008—Multistep processes
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- H01L21/02019—Chemical etching
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- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/02041—Cleaning
- H01L21/02043—Cleaning before device manufacture, i.e. Begin-Of-Line process
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Abstract
The invention discloses an acid etching solution, which is prepared by mixing a hydrofluoric acid solution with the concentration of 40-60%, a nitric acid solution with the concentration of 60-75%, a phosphoric acid solution with the concentration of 70-90%, a sulfuric acid solution with the concentration of 90-100% and a citric acid solution with the concentration of 5-15% according to the volume ratio of 1-8. The invention also discloses a silicon wafer processing and wafer packaging method, wherein H is added into the traditional acid solution 3 PO 4 、H 2 SO 4 Two kinds of acid with larger viscosity are used for preventing the acid from entering the silicon wafer body along the gap in the acid corrosion process so as to corrode the silicon wafer body; in the acid corrosion process, the chemicals are ensured to stay on the surface of the silicon wafer for etching, and the cracks of a damage layer caused by grinding can not be used for drilling, so that the stress of the silicon wafer is reduced, and the defects of the prior art are greatly improvedWarpage, total thickness differential (TTV), global Flatness (GFLR), local flatness (SFQR).
Description
Technical Field
The invention relates to the field of chemical corrosive liquid, in particular to an acid corrosive liquid and application thereof.
Background
The polishing and lapping technique for silicon wafers is an essential process in the semiconductor process, and has become an indispensable technique which is important and interdependent with techniques such as photolithography, etching, and ion implantation in the fabrication of Integrated Circuits (ICs). The silicon chip processing procedure mainly comprises a silicon chip grinding and thinning procedure, a chemical corrosion procedure, a silicon chip polishing procedure and a silicon chip cleaning procedure, wherein a grinding disc made of cast iron is used in the grinding and thinning procedure, a damaged layer is formed on the surface of a general silicon chip after grinding due to mechanical damage, as shown in figure 1, the thickness of the damaged layer is related to each parameter of a grinding process, the damaged layer of about 4um is generally caused, the stress at the damaged layer is large, and the subsequent processing procedure is a defect;
the polishing process generally uses a polishing pad and a grinding fluid to carry out the overall planarization of the silicon wafer, and the mechanical action is always kept approximately equal to the chemical action, so the removal amount of the general polishing is small, generally about 0.5um is removed, and the damage layer caused by the grinding cannot be removed sufficiently;
in summary, a chemical etching process is generally used to remove the damaged layer after polishing, so as to ensure that the damaged layer is substantially removed during the subsequent polishing process;
the chemical corrosion is mainly to carry out chemical reaction with a silicon wafer under certain conditions by mixed acid or alkali, so as to achieve the purpose of removing a damaged layer on the surface of the silicon grinding sheet and eliminate the crystal stress caused by incomplete crystal lattices as far as possible.
At present, the chemical corrosion of the 12-inch silicon wafer processing mostly uses alkali solution (KOH or NaOH) and uses a small amount of acid solution (HF + HNO) 3 ) (ii) a While most of the chemical etching in the processing of silicon wafers with the size of 8 inches or less uses an acid solution (HF + HNO 3);
acid etching (HF + HNO) 3 ) The etching is generally isotropic etching and is irrelevant to the crystal orientation of the silicon wafer, so the acid etching can obtain the silicon wafer with approximate mirror polishing; however, because the acid corrosion rate is high, a primary battery is formed at the damaged layer and an electrochemical effect is generated, so that the reaction speed is further increased, and chemicals enter the silicon wafer body along the longitudinal gap of the surface to form a circular pit, so that the flatness parameters TTV, GFLR and SFQR are poor, but because of the isotropic characteristic of acid corrosion, the roughness of the silicon wafer surface is good;
since the alkali etching (KOH or NaOH) is generally anisotropic etching, and is related to the crystal orientation of the silicon wafer, the etching rate is generally (100) > (110) > (111), and therefore, the silicon wafer surface obtained by the alkali etching has poor roughness and no luster; the etching rate of the alkali corrosion is slower, so that the local fluctuation of the surface of the silicon wafer is smaller, the flatness parameters TTV, GFLR and SFQR are better, but the roughness of the surface of the silicon wafer is poorer due to the anisotropic characteristic of the alkali corrosion, and simultaneously, a diamond pattern is formed;
in addition to the flatness parameter difference, the alkali etching generally needs high temperature, which easily causes metal pollution in the silicon wafer and generates deeper etch pits; the acid corrosion generally uses low temperature, and the purity of the used acid liquor is higher, so metal pollution is not easy to generate, and the depth of the generated etching pit is also shallower;
acid solution (HF + HNO) 3 ) HF and HNO in 3 The chemical substances with low viscosity continuously enter the silicon wafer body along a longitudinal gap on the surface while corroding the silicon wafer, so that the flatness parameters of the silicon wafer are influenced;
in practical application, the silicon wafer with the size of 8 inches or less has lower requirement on the flatness of the silicon wafer, so acid corrosion is generally selected, and the characteristics of lower metal pollution, better glossiness and the like of the silicon wafer can be ensured; in the application of 12-inch silicon wafers, the requirement on the flatness of the silicon wafers is high, so that alkali corrosion is generally selected, and chelating agents are selected for controlling metal pollution to remove the metal pollution, but the roughness is always an unsolved problem.
Disclosure of Invention
The present invention is directed to solving at least one of the problems of the prior art. The invention aims to provide an acid etching solution to solve the problem of poor flatness of an acid-etched silicon wafer and ensure that a silicon wafer with low metal pollution, better roughness, better flatness and high glossiness can be obtained.
In a first aspect of the invention, the acid etching solution is prepared by mixing a hydrofluoric acid solution with a concentration of 40% -60%, a nitric acid solution with a concentration of 60% -75%, a phosphoric acid solution with a concentration of 70% -90%, a sulfuric acid solution with a concentration of 90% -100% and a citric acid solution with a concentration of 5% -15% according to a volume ratio of 1-8.
According to the embodiment of the invention, the acid etching solution is prepared by mixing 49% hydrofluoric acid solution, 70% nitric acid solution, 85% phosphoric acid solution, 98% sulfuric acid solution and 10% citric acid solution according to the volume ratio of 1.63.
According to the embodiment of the invention, the acid etching solution is a hydrofluoric acid solution with a concentration of 49%, a nitric acid solution with a concentration of 70%, a phosphoric acid solution with a concentration of 85%, a sulfuric acid solution with a concentration of 98% and a citric acid solution with a concentration of 10% which are mixed according to a volume ratio of 1.53.
According to the embodiment of the invention, the acid etching solution is prepared by mixing 49% hydrofluoric acid solution, 70% nitric acid solution, 85% phosphoric acid solution, 98% sulfuric acid solution and 10% citric acid solution according to the volume ratio of 1.21.
According to the embodiment of the invention, the acid etching solution is a hydrofluoric acid solution with a concentration of 49%, a nitric acid solution with a concentration of 70%, a phosphoric acid solution with a concentration of 85%, a sulfuric acid solution with a concentration of 98% and a citric acid solution with a concentration of 10% which are mixed according to a volume ratio of 1.
In a second aspect of the present invention, the present invention provides a silicon wafer processing method, including the steps of:
s1, silicon wafer pretreatment: cleaning oil stains and impurity particles on the surface of the silicon wafer;
s2, etching by using acid etching solution: putting the silicon wafer into the acid corrosive liquid for soaking and etching to etch a damaged layer on the surface of the silicon wafer;
s3, cleaning to remove pollutants: putting the silicon wafer into DHF/O 3 In the tank, O is always introduced 3 Soaking in dilute hydrofluoric acid solution to clean away pollutant residue;
and S4, drying.
According to the embodiment of the invention, in the step S1, the silicon wafer pretreatment specifically includes: and (3) putting the silicon wafer into ultrapure water containing an oil stain cleaning agent, and soaking for 30-120s.
According to the embodiment of the invention, after the steps S1 and S2 are finished, the silicon wafer is moved to a quick cleaning tank to be dynamically cleaned by ultrapure water, water in the tank continuously overflows, the temperature is 15-25 ℃, and the silicon wafer is soaked for 150-250S.
According to the embodiment of the present invention, in the step S2, the specific steps are: placing the silicon chip in an acid corrosive liquid, soaking for 200-500s, wherein the rotating speed of the silicon chip is 1-5rpm;
according to the embodiment of the invention, in the step S3, the diluted hydrofluoric acid solution is prepared by mixing 49% hydrofluoric acid solution and water in a volume ratio of 1 3 The flow rate of the soaking liquid is 0.5-2L/min, the temperature is 50-66 ℃, and the soaking liquid is soaked for 60-120s.
In a third aspect of the present invention, a wafer packaging method is provided, which is characterized by comprising the following steps:
s1, pretreatment of a wafer: cleaning oil stains and impurity particles on the surface of the wafer;
s2, etching by using acid etching solution: putting the wafer into the acid corrosive liquid for soaking and etching so as to etch off a damaged layer on the surface of the wafer;
s3, cleaning to remove pollutants: placing the wafer in DHF/O 3 In the tank, O is always introduced 3 Soaking in a diluted hydrofluoric acid solution to clean away contaminant residues;
and S4, drying.
Compared with the prior art, the invention has the following beneficial effects:
(1) The invention adds H into the traditional acid solution 3 PO 4 、H 2 SO 4 The two acids with higher viscosity are prevented from entering the silicon wafer body along the gap in the acid corrosion process, and further corroding the silicon wafer body; the wetting effect of acid with high viscosity is poor, and the surface tension of the acid corrosion solution is high, so that the acid corrosion solution cannot be rapidly diffused to each area of the silicon wafer, therefore, chemicals are guaranteed to stay on the surface of the silicon wafer to be etched in the acid corrosion process, cracks of a damage layer caused by grinding cannot be used for drilling and etching, the stress of the silicon wafer is reduced, and the warping degree, total thickness difference (TTV), global Flatness (GFLR) and local flatness (SFQR) are greatly improved; in acid corrosive liquidH of (A) to (B) 3 PO 4 Citric acid is two ternary weak acids, and multi-stage reversible ionization balance exists in aqueous solution, so ionization H + Weak ability to further inhibit H + The dissociation reduces the corrosion rate and improves the corrosion uniformity; meanwhile, the citric acid has a certain complexing effect, and can complex various metal pollutants, so that the metal pollution is further reduced.
(2) The acid corrosion liquid can be applied to the field of silicon wafer processing and can also be applied to the field of wafer packaging.
Drawings
FIG. 1 is a schematic diagram of a damaged layer of a silicon wafer after grinding;
FIG. 2 is a schematic flow diagram of an acid etching solution for silicon wafer processing according to an embodiment of the present invention;
FIG. 3 is a box plot diagram of the corresponding relationship between different etching processes and the total thickness difference TTV of the silicon wafer;
FIG. 4 is a box diagram of the correspondence between different etching processes and the overall flatness GFLR of the silicon wafer;
FIG. 5 is a box plot diagram of the correspondence between different etching processes and the local flatness SFQR of the silicon wafer.
FIG. 6 is a schematic flow diagram of various etching processes.
Detailed Description
The present invention will be described in detail below. The technical features described below are explained based on typical embodiments and specific examples of the present invention, but the present invention is not limited to these embodiments and specific examples. It should be noted that:
in the present specification, the numerical range represented by the expression "numerical value a to numerical value B" means a range including the end points of numerical values a and B.
In the present specification, "plural" in "plural", and the like means a numerical value of 2 or more unless otherwise specified.
In the present specification, "%" represents mass% unless otherwise specified.
In the present specification, the term "may" includes both the case where a certain process is performed and the case where no process is performed.
In this specification, "optional" or "optionally" means that the subsequently described event or circumstance may or may not occur, and that the description includes instances where the event occurs and instances where it does not.
In the present specification, reference to "some particular/preferred embodiments," "other particular/preferred embodiments," "embodiments," and the like, means that a particular element (e.g., feature, structure, property, and/or characteristic) described in connection with the embodiment is included in at least one embodiment described herein, and may or may not be present in other embodiments. In addition, it is to be understood that the described elements may be combined in any suitable manner in the various embodiments.
The temperature referred to herein as "room temperature" is generally between "10-40 ℃.
First aspect of the invention
The first aspect of the invention provides an acid etching solution, which is prepared by mixing a hydrofluoric acid solution with a concentration of 40-60%, a nitric acid solution with a concentration of 60-75%, a phosphoric acid solution with a concentration of 70-90%, a sulfuric acid solution with a concentration of 90-100% and a citric acid solution with a concentration of 5-15% according to a volume ratio of 1-8.
Conventional acid solution (HF + HNO) 3 ) The chemical corrosion process of the silicon chip is shown as the following reaction formula, wherein HNO 3 Is an oxidizing agent for silicon, HF is an etchant for silicon:
3Si+4HNO 3 →3SiO 2 +4NO+2H 2 O
SiO 2 +6HF→H 2 SiF 6 (soluble substance) +2H 2 O
Acid solution (HF + HNO) 3 ) HF and HNO in (1) 3 The chemical substances with low viscosity continuously enter the silicon wafer body along a longitudinal gap on the surface while corroding the silicon wafer, so that the flatness parameters of the silicon wafer are influenced;
in the invention, H is added into the traditional acid solution 3 PO 4 、H 2 SO 4 The two acids with higher viscosity are prevented from entering the silicon wafer body along the gap in the acid corrosion process, and further corroding the silicon wafer body; the wetting effect of acid with high viscosity is poor, and the surface tension of the acid corrosion solution is high, so that the acid corrosion solution cannot be rapidly diffused to each area of the silicon wafer, therefore, chemicals are guaranteed to stay on the surface of the silicon wafer to be etched in the acid corrosion process, cracks of a damage layer caused by grinding cannot be used for drilling and etching, the stress of the silicon wafer is reduced, and the warping degree, total thickness difference (TTV), global Flatness (GFLR) and local flatness (SFQR) are greatly improved;
h in acid etching solution 3 PO 4 Citric acid is two ternary weak acids, and multi-stage reversible ionization equilibrium exists in aqueous solution, so that ionization H + Weak ability to further inhibit H + The dissociation reduces the corrosion rate and improves the corrosion uniformity; meanwhile, the citric acid has a certain complexing effect, and can complex various metal pollutants, so that the metal pollution is further reduced.
According to the embodiment of the invention, the acid etching solution is prepared by mixing a hydrofluoric acid solution with a concentration of 49%, a nitric acid solution with a concentration of 70%, a phosphoric acid solution with a concentration of 85%, a sulfuric acid solution with a concentration of 98% and a citric acid solution with a concentration of 10% according to a volume ratio of 1.63.
According to the embodiment of the invention, the acid etching solution is a hydrofluoric acid solution with a concentration of 49%, a nitric acid solution with a concentration of 70%, a phosphoric acid solution with a concentration of 85%, a sulfuric acid solution with a concentration of 98% and a citric acid solution with a concentration of 10% which are mixed according to a volume ratio of 1.53.
According to the embodiment of the invention, the acid etching solution is a hydrofluoric acid solution with a concentration of 49%, a nitric acid solution with a concentration of 70%, a phosphoric acid solution with a concentration of 85%, a sulfuric acid solution with a concentration of 98% and a citric acid solution with a concentration of 10% which are mixed according to a volume ratio of 1.21. .
When the contents of the four components are respectively set within the above ranges, a target silicon wafer having good warpage, total Thickness Variation (TTV), global Flatness (GFLR), local flatness (SFQR) parameters is obtained when processing a silicon wafer.
Second aspect of the invention
The second aspect of the present invention provides a use of the acid etching solution according to the first aspect of the present invention for silicon wafer processing, in particular for chemically etching a silicon wafer, as shown in fig. 2, wherein the method comprises the following steps:
s1, silicon wafer pretreatment: cleaning oil stains and impurity particles on the surface of the silicon wafer;
s2, etching by using acid etching solution: putting the silicon wafer into an acid corrosive liquid for soaking and etching so as to etch off a damaged layer on the surface of the silicon wafer;
s3, cleaning to remove pollutants: putting the silicon wafer into DHF/O 3 In the tank, O is always introduced 3 Soaking in dilute hydrofluoric acid solution to clean away pollutant residue;
and S4, drying.
The silicon wafer processing process comprises the following steps: grinding and thinning the silicon wafer → chemical etching → polishing the silicon wafer → cleaning the silicon wafer, and when the silicon wafer is ground and thinned, a small amount of organic matters or oil stains exist in the grinding liquid. In step S1, the silicon wafer pretreatment specifically includes: and (3) putting the silicon wafer into deionized water containing an oil stain cleaning agent, and soaking for 30-120s. The step is used for removing organic matters, oil stains and impurity particles on the silicon wafer.
According to the embodiment of the invention, after the step S1 is finished, the silicon wafer is moved to a quick cleaning tank to be dynamically cleaned by ultrapure water, water in the tank continuously overflows, the temperature is 15-25 ℃, and the silicon wafer is soaked for 150-250S. The step is used for removing the residual oily cleaning agent in the step S1.
According to the embodiment of the present invention, in the step S2, the specific steps are: and (3) placing the silicon wafer into an acid corrosion solution, soaking for 200-500s, and rotating the silicon wafer at the speed of 1-5rpm.
According to the embodiment of the invention, in the step S2, the concentration of the acid etching solution is monitored, the concentration of the acid etching solution is kept in dynamic balance, and the solution is automatically replenished when the concentration is low. The step is used for keeping the dynamic balance of the concentration of the acid etching solution so as to ensure the uniformity of the etching speed of the acid etching solution and be suitable for the pipeline action.
According to the embodiment of the invention, after the step S2 is finished, the silicon wafer is moved to a rapid cleaning tank to be dynamically cleaned by ultrapure water, water in the tank continuously overflows, the temperature is 20 ℃, and the silicon wafer is soaked for 180S. This step is used to prevent the acid etchant from continuing etching and to wash away the residues on the silicon wafer.
According to the embodiment of the invention, in the step S3, the diluted hydrofluoric acid solution is prepared by hydrofluoric acid solution with the concentration of 49% and water in a volume ratio of 1:30-70, and O 3 The flow rate of the soaking liquid is 0.5-2L/min, the temperature is 50-66 ℃, and the soaking liquid is soaked for 60-120s. The cleaning method is characterized in that pollutant residues including metal are cleaned, HF only reacts with silicon oxide and does not react with silicon, ozone is used for accelerating silicon oxidation to generate silicon oxide, and meanwhile, a diluted hydrofluoric acid solution can remove a natural oxidation film on the surface of a silicon wafer so as to be beneficial to removal of metal and organic pollutants embedded in an oxidation layer.
According to an embodiment of the present invention, the step S4 is a specific step of drying: and slowly pulling the silicon wafer, and drying by using infrared, wherein the temperature of an infrared heater is set to be 120-180 ℃, and the pulling time is 30-70s. The silicon wafer was drained during slow pull and infrared accelerated drying was used.
Third aspect
The third aspect of the invention provides a wafer packaging method, in particular to a wafer back surface chemical corrosion method, which comprises the following steps:
s1, wafer pretreatment: cleaning oil stains and impurity particles on the surface of the silicon wafer;
s2, etching by using acid etching solution: putting the silicon wafer into the acid etching solution of the first aspect for soaking and etching to etch off a damaged layer on the surface of the wafer;
s3, cleaning to remove pollutants: placing the wafer in DHF/O 3 In the tank, O is always introduced 3 Soaking in dilute hydrofluoric acid solution to clean away pollutant residue;
and S4, drying.
After the wafer is manufactured, the silicon wafer is still in the shape of the silicon wafer, and the electrical connection in the wafer cannot be connected to the outside, so that the wafer needs to be further processed to ensure that signal input/output and voltage supply can be performed normally, and meanwhile, the chip is protected from the influence of external temperature, humidity, pressure and the like, even the chip fails, so that the processing is the wafer packaging process.
The wafer packaging process mainly includes a lead frame process, a ball grid array process, a through silicon via technology, rewiring and the like.
The wafer packaging process flow comprises the following steps: attaching a blue film adhesive tape on the front surface of the wafer → grinding and thinning the back surface of the wafer → removing the blue film adhesive tape on the front surface of the wafer → chemical etching/dry etching on the back surface of the wafer → cutting the wafer → attaching → bonding → wire connection → plastic packaging → baking after marking → electroplating/ball filling → cutting.
Considering that the wafer is finally cut into chips, the thickness of the wafer needs to be controlled to be reasonable, smooth cutting is ensured, and the warping degree and the risk of breaking the thinned wafer are ensured;
a large amount of mechanical stress remains after the polishing process, and a large amount of voids and stress, which may cause wafer breakage in the subsequent processing, are also present, as shown in fig. 1; therefore, the purpose of removing the damaged layer on the surface of the silicon grinding sheet is generally achieved by chemical etching/dry etching, and the crystal stress caused by incomplete crystal lattice is eliminated as much as possible.
The etching solution is mainly used for a chemical etching process of the back of a wafer.
Silicic acid corrosive liquid (HF + HNO) 3 ) The silicon wafer is isotropically etched, and is irrelevant to the crystal orientation of the silicon wafer, so the silicon wafer with approximate mirror polishing can be obtained by acid corrosion; however, since the acid corrosion rate is high, a primary cell is formed at the damaged layer and an electrochemical effect occurs, so that the reaction speed is further increased, and chemicals enter the silicon wafer body along a longitudinal gap on the surface to form a circular pit, which also causes poor flatness of the wafer;
the acid etching solution solves the problem of poor flatness of the wafer corroded by the traditional acid, and ensures that the wafer with better flatness and high gloss can be obtained;
conventional acid solution (HF + HNO) 3 ) HF and HNO in 3 The chemical substances with low viscosity continuously enter the wafer body along the longitudinal gap of the surface while corroding the wafer, so that the flatness parameters of the wafer are influenced;
the acid etching solution of the invention uses H 3 PO 4 、H 2 SO 4 The acid with higher viscosity is prevented from entering the wafer body along the gap in the acid corrosion process, so that the wafer body is corroded; the wetting effect of the acid with high viscosity is poor, the surface tension of the acid solution is high, and the acid solution HS cannot be diffused to each area of the wafer quickly, so that chemicals are guaranteed to stay on the surface of the wafer for etching in the acid corrosion process, cracks of a damage layer caused by grinding cannot be used for drilling, the stress of the wafer is reduced, the warping degree of the wafer is greatly improved, and the risk of wafer breakage is reduced;
h in acid etching solution 3 PO 4 Citric acid is two ternary weak acids, and multi-stage reversible ionization equilibrium exists in aqueous solution, so that ionization H + Weak ability to further inhibit H + The dissociation reduces the corrosion rate and improves the corrosion uniformity; meanwhile, the citric acid has a certain complexing effect, and can complex various metal pollutants, so that the metal pollution is further reduced.
Examples
Embodiments of the present invention will be described in detail below with reference to examples, but those skilled in the art will appreciate that the following examples are only illustrative of the present invention and should not be construed as limiting the scope of the present invention. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products commercially available.
Example 1
The acid etching solution is prepared by mixing 49% hydrofluoric acid solution, 70% nitric acid solution, 85% phosphoric acid solution, 98% sulfuric acid solution and 10% citric acid solution according to the volume ratio of 1.
The acid corrosion solution comprises the following components in percentage by mass: 3.28 percent of hydrofluoric acid, 33.95 percent of nitric acid, 19.92 percent of phosphoric acid, 15.18 percent of sulfuric acid, 0.59 percent of citric acid and the balance of water.
Example 2
The acid etching solution is prepared by mixing 49% hydrofluoric acid solution, 70% nitric acid solution, 85% phosphoric acid solution, 98% sulfuric acid solution and 10% citric acid solution according to the volume ratio of 1.63.
The acid corrosion solution comprises the following components in percentage by mass: 5% of hydrofluoric acid, 40% of nitric acid, 18% of phosphoric acid, 10% of sulfuric acid, 1% of citric acid and the balance of water.
Example 3
The acid etching solution is prepared by mixing 49% hydrofluoric acid solution, 70% nitric acid solution, 85% phosphoric acid solution, 98% sulfuric acid solution and 10% citric acid solution according to the volume ratio of 1.53.
The acid corrosion solution comprises the following components in percentage by mass: 8% of hydrofluoric acid, 35% of nitric acid, 25% of phosphoric acid, 20% of sulfuric acid, 0.25% of citric acid and the balance of water.
Example 4
The acid etching solution is prepared by mixing 49% hydrofluoric acid solution, 70% nitric acid solution, 85% phosphoric acid solution, 98% sulfuric acid solution and 10% citric acid solution according to the volume ratio of 1.21.
The acid corrosion solution comprises the following components in percentage by mass: 5% of hydrofluoric acid, 45% of nitric acid, 18% of phosphoric acid, 13% of sulfuric acid, 0.5% of citric acid and the balance of water.
Industrial applicability
The acid etching solution provided by the invention can be industrially prepared and used for processing silicon wafers, and is particularly used for chemically etching silicon wafers.
Example 5
Taking the acid etching solution of the embodiment 1 as an example, a silicon wafer processing method comprises the following steps:
putting the flower basket with the silicon wafer into ultrapure water, wherein the solution needs to contain an oil stain cleaning agent, and soaking for 60s at 65 ℃;
moving the flower basket to a quick cleaning tank through a mechanical arm to dynamically clean the flower basket with ultrapure water, wherein water in the tank continuously overflows and is soaked for 180s at the temperature of 20 ℃;
moving the flower basket containing the silicon wafers into an acid corrosion solution through a mechanical arm, soaking for 300s at the temperature of 20 ℃, and stabilizing the rotating speed of the silicon wafers in the flower basket at 3rpm to ensure the etching uniformity; monitoring the concentration, automatically discharging the existing acid corrosive liquid when the concentration is low, supplementing the liquid, and etching off the damaged layer;
moving the flower basket to a quick cleaning tank through a mechanical arm to dynamically clean the flower basket with ultrapure water, wherein the temperature is 20 ℃, and soaking for 180s; so as to prevent the acid corrosive liquid from continuously etching and wash away residues on the silicon wafer;
moving a flower basket to DHF/O by a robotic arm 3 In the tank, the diluted hydrofluoric acid solution is prepared by 49% hydrofluoric acid solution and water according to the volume ratio of 1;
slowly lifting the flower basket by a mechanical arm, and drying by using infrared, wherein the temperature of an infrared heater is set at 150 ℃, and the lifting time is 50s.
Comparative experiment
Selecting 10 crystal bars, extracting 9 silicon wafers from each crystal bar at continuous positions, totaling 90 silicon wafers (the grinding process is completed), wherein 30 silicon wafers are subjected to alkali corrosion (KOH) and recorded as an experimental group A;30 silicon wafers were subjected to conventional acid etching (HF + HNO) 3 ) Taken as test group B;30 wafers were acid-etched using the acid etching solution of example 1, and this was designated as test group C. The process flow for each set is shown with reference to FIG. 6.
The alkali corrosion procedure for experimental group a was as follows:
putting the flower basket filled with the silicon wafers into 43-45% potassium hydroxide solution, and soaking for 120s at 90 ℃;
moving the flower basket to a quick cleaning tank through a mechanical arm to dynamically clean the flower basket with ultrapure water, wherein the temperature is 20 ℃, and soaking for 300s;
moving the flower basket to HF/H by a mechanical arm 2 O 2 In a tank, wherein HF is 49% hydrofluoric acid solution, H 2 O 2 Adopting 35% hydrogen peroxide solution, hydrofluoric acid solution and H 2 O 2 Soaking the solution for 300s at the temperature of 20 ℃ in a volume ratio of 2;
moving the flower basket to a quick cleaning tank through a mechanical arm to dynamically clean the flower basket with ultrapure water, wherein the temperature is 20 ℃, and soaking for 300s;
moving the flower basket into an ultrapure water tank by a mechanical arm, and soaking for 30s at the temperature of 60 +/-10 ℃;
slowly lifting the flower basket by a mechanical arm, and drying by using infrared, wherein the infrared temperature is set at 150 ℃, and the lifting time is 50s;
experimental group B procedure was as follows: (HF + HNO) 3 Acid etching)
Putting the flower basket with the silicon wafer into ultrapure water, wherein the solution needs to contain an oil stain cleaning agent, and soaking for 60s at 65 ℃;
moving the flower basket to a quick cleaning tank by a mechanical arm, and soaking for 180s at the temperature of 20 ℃;
moving the basket of flowers to HF/HNO by a robot arm 3 HF is 49% hydrofluoric acid solution, HNO 3 Adopting 70% nitric acid solution, hydrofluoric acid solution and HNO 3 The volume ratio of (1) to (10), the temperature is 20 ℃, the soaking time is 270s, the rotating speed of the silicon wafer in the flower basket is stabilized at 3rpm, and the etching uniformity is ensured;
moving the flower basket to a quick cleaning tank by a mechanical arm, and soaking for 180s at the temperature of 20 ℃;
moving the flower basket into a DHF/O3 groove by a mechanical arm, wherein the diluted hydrofluoric acid is prepared by 49% hydrofluoric acid and water according to the volume ratio of 1;
slowly lifting the flower basket by a mechanical arm, and drying by using infrared, wherein the infrared temperature is set at 150 ℃, and the lifting time is 50s;
experimental group C scheme reference example 5;
after chemical etching, the test group a, the test group B and the test group C perform flatness measurement by using a measuring device to obtain Total Thickness Variation (TTV), global Flatness (GFLR) and local flatness (SFQR) data, which are shown in table 1; the test data was plotted as box plots, as shown in fig. 4-5.
TABLE 1 Total thickness Difference TTV, overall flatness and local flatness SFQR levels of silicon wafers treated with different corrosive liquids
As can be seen from the results of FIGS. 3 to 5, the acid solution of Experimental group A (HF + HNO) 3 ) The total thickness difference (TTV), the Global Flatness (GFLR) and the local flatness (SFQR) of the processed silicon wafer are worse than the alkali corrosion, which indicates that acid (HF + HNO) 3 ) The etched surface has poor appearance, and mainly the acid solution continuously etches the gaps of the silicon wafer through the damaged gaps; meanwhile, the total thickness difference (TTV), the Global Flatness (GFLR) and the local flatness (SFQR) of the silicon wafer treated by the acid etching solution in the embodiment 1 are better than those of alkali corrosion in a comparison experiment group C, which shows that the acid etching solution can well avoid the transfer etching of a silicon wafer damage layer and ensure the surface appearance of the silicon wafer.
In conclusion, the acid etching solution in the patent keeps the advantages of the traditional acid solution, namely good roughness, low metal pollution and high glossiness, and also obtains better silicon wafer flatness compared with alkali etching.
In addition, the acid etching solution provided by the invention can also be used in the field of wafer packaging, and is mainly used for a chemical etching process of the back surface of a wafer, the steps of the method are similar to those of a method for chemically etching a silicon wafer, and the process parameters are different according to the removal amount.
Example 6
A wafer packaging method comprises the following steps:
putting the flower basket with the wafer into ultrapure water, wherein the solution needs to contain an oil stain cleaning agent and is soaked for 60s at 65 ℃;
moving the flower basket to a quick cleaning tank through a mechanical arm to dynamically clean the flower basket with ultrapure water, wherein water in the tank continuously overflows and is soaked for 180s at the temperature of 20 ℃;
moving the flower basket with the wafer into an acid corrosion solution through a mechanical arm, soaking for 300s at 20 ℃, stabilizing the rotating speed of the wafer in the flower basket at 3rpm, and ensuring the uniformity of etching; monitoring the concentration, automatically discharging the existing acid corrosive liquid when the concentration is low, supplementing the liquid, and etching away the damaged layer;
moving the flower basket to a quick cleaning tank through a mechanical arm to dynamically clean the flower basket with ultrapure water, wherein the temperature is 20 ℃, and soaking for 180s; so as to prevent the acid corrosive liquid from continuously etching and wash away residues on the wafer;
moving a flower basket to DHF/O by a robotic arm 3 In the tank, the diluted hydrofluoric acid solution is prepared by 49 percent hydrofluoric acid solution and water according to the volume ratio of 1;
the flower basket was slowly pulled up by a robot arm and dried using infrared, the temperature of the infrared heater was set at 150 ℃ and the pulling time was 50s.
The removal amount of the damaged layer in this embodiment is 300 + -10 μm, and a wafer with high flatness and high gloss is obtained.
The above examples of the present invention are merely examples for clearly illustrating the present invention and are not intended to limit the embodiments of the present invention. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the claims of the present invention.
Claims (10)
1. The acid etching solution is characterized by being prepared by mixing a hydrofluoric acid solution with the concentration of 40-60%, a nitric acid solution with the concentration of 60-75%, a phosphoric acid solution with the concentration of 70-90%, a sulfuric acid solution with the concentration of 90-100% and a citric acid solution with the concentration of 5-15% according to the volume ratio of 1-8.
2. The acid etching solution according to claim 1, wherein the acid etching solution is a hydrofluoric acid solution having a concentration of 49%, a nitric acid solution having a concentration of 70%, a phosphoric acid solution having a concentration of 85%, a sulfuric acid solution having a concentration of 98%, and a citric acid solution having a concentration of 10% mixed at a volume ratio of 1.
3. The acid etching solution according to claim 1, wherein the acid etching solution is a hydrofluoric acid solution having a concentration of 49%, a nitric acid solution having a concentration of 70%, a phosphoric acid solution having a concentration of 85%, a sulfuric acid solution having a concentration of 98%, and a citric acid solution having a concentration of 10% mixed at a volume ratio of 1.
4. The acid etching solution according to claim 1, wherein the acid etching solution is a hydrofluoric acid solution with a concentration of 49%, a nitric acid solution with a concentration of 70%, a phosphoric acid solution with a concentration of 85%, a sulfuric acid solution with a concentration of 98%, and a citric acid solution with a concentration of 10% mixed in a volume ratio of 1.
5. A silicon wafer processing method is characterized by comprising the following steps:
s1, silicon wafer pretreatment: cleaning oil stains and impurity particles on the surface of the silicon wafer;
s2, etching by using acid etching solution: putting a silicon wafer into the acid etching solution of any one of claims 1 to 4 for soaking and etching to etch away a damaged layer on the surface of the silicon wafer;
s3, cleaning to remove pollutants: putting the silicon wafer into DHF/O 3 In the tank, O is always introduced 3 Under the condition of (2), soaking in diluteIn hydrofluoric acid solution to clean away the contaminant residue;
and S4, drying.
6. The silicon wafer processing method according to claim 5, wherein in step S1, the silicon wafer pretreatment specifically comprises: and (3) putting the silicon wafer into ultrapure water containing an oil stain cleaning agent, and soaking for 30-120s.
7. The silicon wafer processing method according to claim 5,
after the steps S1 and S2 are finished, the silicon wafer is moved to a quick cleaning tank to be dynamically cleaned by ultrapure water, water in the tank continuously overflows, the temperature is 15-25 ℃, and the silicon wafer is soaked for 150-250S.
8. The silicon wafer processing method according to claim 5, wherein in the step S2, the specific steps are as follows: and (3) placing the silicon wafer into an acid corrosion solution, and soaking for 200-500s at the silicon wafer rotating speed of 1-5rpm.
9. The method for processing silicon wafers as set forth in claim 5, wherein the diluted hydrofluoric acid solution is a 49% hydrofluoric acid solution and water at a volume ratio of 1 3 The flow rate of the soaking liquid is 0.5-2L/min, the temperature is 50-66 ℃, and the soaking liquid is soaked for 60-120s.
10. A wafer packaging method is characterized by comprising the following steps:
s1, pretreatment of a wafer: cleaning oil stains and impurity particles on the surface of the wafer;
s2, etching by using acid etching solution: putting the wafer into the acid etching solution of any one of claims 1 to 4 for soaking and etching to etch away the damaged layer on the surface of the wafer;
s3, cleaning to remove pollutants: placing the wafer in DHF/O 3 In the tank, O is always introduced 3 Soaking in a diluted hydrofluoric acid solution to clean away contaminant residues;
and S4, drying.
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| CN116246947A (en) * | 2023-05-11 | 2023-06-09 | 粤芯半导体技术股份有限公司 | Wafer surface roughening method and preparation method of semiconductor device |
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