CN109755099B - Cleaning process for silicon wafer after diffusion - Google Patents
Cleaning process for silicon wafer after diffusion Download PDFInfo
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- CN109755099B CN109755099B CN201711057485.8A CN201711057485A CN109755099B CN 109755099 B CN109755099 B CN 109755099B CN 201711057485 A CN201711057485 A CN 201711057485A CN 109755099 B CN109755099 B CN 109755099B
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Abstract
The invention provides a cleaning process after silicon wafer diffusion, which specifically comprises the following steps of S1: carrying out acid treatment on the diffused silicon wafer; s2: carrying out mixed acid treatment on the silicon wafer subjected to acid treatment; s3: and carrying out organic solvent treatment on the silicon chip treated by the mixed acid. The method has the advantages that due to the adoption of the technical scheme, the silicon wafer is cleaned more conveniently and quickly after being diffused, the cleanliness of the surface of the silicon wafer can more easily meet the requirement of the production specification, the method not only can remove phosphorosilicate glass and borosilicate glass after being diffused on the surface of the silicon wafer and separate the diffused silicon wafer, but also can clean impurities on the surface of the silicon wafer so that the cleanliness of the surface of the silicon wafer can meet the requirement of the production specification, the preparation is made for the subsequent process, and the silicon wafer is cleaned by adopting absolute ethyl alcohol, so that the adsorption of particle impurities on the surface of the silicon wafer is reduced, and the cleanliness of the surface of the silicon wafer is further ensured.
Description
Technical Field
The invention belongs to the technical field of silicon wafer production, and particularly relates to a cleaning process for a silicon wafer after diffusion.
Background
With the development of semiconductor technology, the demand for passivation of semiconductor surface is higher and higher, and as a passivation material, the passivation material should have good electrical performance, reliability, good chemical stability, operability and economy. According to the requirements, the special glass for semiconductor passivation is taken as a more ideal semiconductor passivation material and starts to be applied in the semiconductor industry. A Chip manufactured by using Glass dedicated for semiconductor passivation is called a Glass passivation process Chip (GPP Chip).
The GPP chip is required to diffuse a phosphorus source and a boron source to a silicon wafer before glass passivation, a texturing process is carried out after diffusion, the silicon wafer is required to be cleaned after diffusion, the surface of the silicon wafer is cleaned, meanwhile, phosphorosilicate glass and borosilicate glass formed after the surface of the silicon wafer is diffused are removed, preparation is made for texturing the surface of the silicon wafer before the glass passivation process, at present, the cleaning mode of the silicon wafer after diffusion is cleaning by adopting hydrofluoric acid, only the silicon wafer is cleaned simply, the phosphorosilicate glass and the borosilicate glass formed after the silicon wafer is diffused cannot be removed effectively, and Na, K, Ca, Mg, Zn, Al and other relatively active metals cannot be removed effectively by weak acid HF; the surface of the silicon wafer cleaned by HF is hydrophobic and cannot become an ideal surface, and the surface of the silicon wafer is active and is easy to adsorb particle impurities and the like.
Disclosure of Invention
In view of the above problems, the present invention provides a process for cleaning a silicon wafer after diffusion, which is particularly suitable for cleaning a silicon wafer for manufacturing GPP chips after diffusion, and the process sequentially includes hydrofluoric acid cleaning, pure water cleaning and mixed acid cleaning to remove phosphorosilicate glass and borosilicate glass on the surface of the silicon wafer and clean impurities on the surface of the silicon wafer, so that the cleanliness of the surface of the silicon wafer reaches the requirement of production specification, and absolute ethyl alcohol is used for cleaning to reduce the adsorption of particle impurities on the surface of the silicon wafer.
In order to solve the technical problems, the invention adopts the technical scheme that: a cleaning process for silicon wafer after diffusion comprises the following steps,
s1: carrying out acid treatment on the diffused silicon wafer;
s2: carrying out mixed acid treatment on the silicon wafer subjected to acid treatment;
s3: and carrying out organic solvent treatment on the silicon chip treated by the mixed acid.
Further, the acid treatment comprises the specific steps of soaking the silicon wafer in an acid solution for 36-60 hours, and replacing the acid solution every 10-15 hours.
Further, the acid treatment is hydrofluoric acid treatment.
Further, the mixed acid in the mixed acid treatment in step S2 is nitric acid, hydrofluoric acid, acetic acid, and pure water mixed in a certain ratio.
Further, the specific steps of the mixed acid treatment are as follows:
s21: preparing a mixed acid solution: the volume ratio of nitric acid, hydrofluoric acid, acetic acid and pure water is 2000-: 200-500 ml: 100-300 ml: 2000-;
s22: putting the silicon chip into a mixed acid solution for corrosion treatment, wherein the corrosion time is 10-30 s;
s23: and cleaning the silicon wafer subjected to the mixed acid corrosion treatment by pure water.
Further, the absolute ethanol treatment comprises the following steps:
s31: placing the silicon wafer subjected to mixed acid treatment in absolute ethyl alcohol for dehydration treatment, wherein the dehydration time is 10-30 s;
s32: drying the silicon wafer by using nitrogen, and placing the silicon wafer in a drying oven for drying;
s33: and inspecting the silicon wafer.
Further, the organic solvent treatment is absolute ethyl alcohol treatment.
Further, between the step S1 and the step S2, a water washing is further included.
The invention has the advantages and positive effects that: by adopting the technical scheme, the silicon wafer is more convenient and faster to clean after diffusion, the cleanliness of the surface of the silicon wafer can more easily meet the requirement of the production specification, hydrofluoric acid cleaning, pure water cleaning and mixed acid cleaning are sequentially adopted, phosphorosilicate glass and borosilicate glass diffused on the surface of the silicon wafer can be removed, the diffused silicon wafer is separated, impurities on the surface of the silicon wafer can be cleaned, the cleanliness of the surface of the silicon wafer can meet the requirement of the production specification, preparation is made for subsequent processes, anhydrous ethanol is adopted to carry out dehydration treatment on the silicon wafer, the silicon wafer is rapidly dehydrated, adsorption of particle impurities on the surface of the silicon wafer is reduced, and the cleanliness of the surface of the silicon wafer is further ensured.
Drawings
FIG. 1 is a process flow diagram of the present invention.
Detailed Description
The invention is further described with reference to the following figures and specific embodiments.
As shown in FIG. 1, the invention relates to a cleaning process after silicon wafer diffusion, which comprises the following steps,
s1: carrying out acid treatment on the diffused silicon wafer;
s2: carrying out mixed acid treatment on the silicon wafer subjected to acid treatment;
s3: and carrying out organic solvent treatment on the silicon chip treated by the mixed acid.
Namely, the diffused silicon wafer is sequentially subjected to acid treatment, mixed acid treatment and organic solvent treatment, phosphorosilicate glass or borosilicate glass formed on the surface of the diffused silicon wafer is removed, the silicon wafer is cleaned, and impurities on the surface of the silicon wafer are cleaned, so that the silicon wafer meets the specification requirements and is prepared for the subsequent processes.
And (3) after the diffused silicon wafer is subjected to acid treatment, washing with water, washing an acid solution on the surface of the silicon wafer subjected to acid treatment, separating the silicon wafers adhered together, performing acid treatment and water washing again, spin-drying, and preparing for subsequent mixed acid treatment.
The cleaning process after the silicon wafer diffusion comprises the following specific steps:
the method comprises the following steps: the method comprises the following steps of carrying out acid treatment on diffused silicon wafers, removing phosphorosilicate glass and borosilicate glass formed on the surfaces of the diffused silicon wafers, separating the silicon wafers which are adhered together after diffusion, carrying out acid treatment on each silicon wafer, and preparing for subsequent mixed acid treatment, wherein the specific steps are as follows:
step S10: cooling the silicon wafers after diffusion is finished, carrying out junction depth inspection, carefully taking down the silicon wafers with qualified junction depth and the simulation wafers after cooling from a silicon boat, transferring the silicon wafers and the simulation wafers into a special container for soaking and post-treatment, and preparing for acid treatment, wherein the special container for acid treatment is a special flower basket for acid treatment, the special flower basket is a polytetrafluoroethylene flower basket, and the silicon wafers are placed in the flower basket;
step S11: pouring the prepared acid solution into a container for acid treatment, wherein the acid for acid treatment is hydrofluoric acid solution, the content of hydrofluoric acid in the hydrofluoric acid solution is 40% -60%, preferably, the concentration of the hydrofluoric acid solution is 49%, the acid treatment container can be an acid treatment tank, the tank does not react with hydrofluoric acid, and the acid treatment container has good sealing performance and is convenient for the silicon wafer to be placed in the container for acid treatment. And pouring the hydrofluoric acid solution into an acid treatment container, wherein the volume of the hydrofluoric acid solution is 2500-.
Step S12: the silicon wafer is soaked in the hydrofluoric acid solution for 36-60 hours, so that the silicon wafer fully reacts with the hydrofluoric acid solution, phosphorosilicate glass and borosilicate glass formed on the surface of the silicon wafer after diffusion are corroded, the hydrofluoric acid solution reacts with the phosphorosilicate glass and the borosilicate glass on the surface of the silicon wafer, the content of hydrofluoric acid in the hydrofluoric acid solution is reduced, the corrosion speed of the surface of the silicon wafer is guaranteed for keeping the concentration of hydrofluoric acid in the hydrofluoric acid solution, the hydrofluoric acid solution is replaced every 10-15 hours for separating the silicon wafers adhered together, the silicon wafers are taken out until the silicon wafers are separated, the silicon wafers are separated after being treated by the hydrofluoric acid, and the phosphorosilicate glass and the borosilicate glass on the surface of the silicon wafer are removed.
Step two: and (2) cleaning the silicon wafer treated by hydrofluoric acid with water, wherein the water cleaning is carried out by selecting pure water, so as to avoid secondary pollution to the silicon wafer, and meanwhile, cleaning the hydrofluoric acid solution on the surface of the silicon wafer, and simultaneously, cleaning the impurities of phosphorosilicate glass and borosilicate glass on the surface of the silicon wafer treated by hydrofluoric acid. The method for cleaning the silicon wafer by pure water comprises the following specific steps: putting a flower basket which is taken out from a hydrofluoric acid solution and is used for containing the silicon wafers into a pure water tank for overflow cleaning, wherein the overflow cleaning time is 30-60min, the overflow cleaning enables the pure water flow to be 4-10L/min, cleaning the silicon wafers in the flower basket, cleaning the hydrofluoric acid solution and impurities on the surfaces of the silicon wafers, drying after cleaning, and removing the moisture on the surfaces of the silicon wafers. In the process of overflow cleaning, if silicon wafers adhered together are found, slightly scratching the silicon wafers by using a blade, and soaking the silicon wafers together with the silicon wafers with the oxide films on the surfaces in a hydrofluoric acid solution, wherein the oxide films and phosphorosilicate glass and borosilicate glass on the surfaces of the silicon wafers are soaked in the hydrofluoric acid solution for etching off the oxide films on the surfaces of the silicon wafers, the hydrofluoric acid solution used in the process is the hydrofluoric acid-treated hydrofluoric acid solution, the soaking time in the hydrofluoric acid is 5-10min, cleaning is carried out by using pure water after soaking, the hydrofluoric acid solution on the surfaces of the silicon wafers is cleaned, meanwhile, impurities of the oxide films etched off by the hydrofluoric acid solution on the surfaces of the silicon wafers are cleaned, and drying is carried out after the pure water cleaning.
Step three: the silicon wafer cleaned by pure water is subjected to mixed acid treatment, phosphorosilicate glass and borosilicate glass which are not removed and are treated by hydrofluoric acid on the surface of the silicon wafer are further corroded to be removed, and particle impurities on the surface of the silicon wafer are cleaned, wherein mixed acid used in the mixed acid treatment is nitric acid, hydrofluoric acid, acetic acid and pure water which are mixed according to a certain proportion, and the nitric acid, the hydrofluoric acid, the acetic acid and the pure water are 3000ml together according to the volume ratio of 2000: 200-500 ml: 100-300 ml: 2000-3000ml were mixed.
The specific steps of the mixed acid treatment are as follows:
step S14: and (3) carrying out mixed acid preparation according to the volume ratio, carrying out preparation before 1-2h of mixed acid treatment, and fully stirring for later use after the preparation is finished.
Step S15: pouring the prepared mixed acid into an etching tank, placing silicon wafers in the etching tank and immersing the silicon wafers in the mixed acid solution to etch the silicon wafers, wherein the etching time is 10-30s, selecting the number of the silicon wafers soaked in the mixed acid solution according to the volume of the etching tank, generally selecting every 4500ml for processing 700 pieces of silicon wafers, enabling each silicon wafer to be in contact with the mixed acid solution, etching the residual phosphorosilicate glass and borosilicate glass on the surfaces of the silicon wafers after being processed by hydrofluoric acid, and cleaning particle impurities on the surfaces of the silicon wafers.
Step S16: and after the corrosion is finished, taking out the polytetrafluoroethylene flower basket containing the silicon wafer from the mixed acid solution, putting the polytetrafluoroethylene flower basket into a water tank for overflow cleaning, wherein the overflow cleaning is carried out by adopting pure water, the cleaning time is 5-15min, the flow of the pure water is 4-10L/min, and the mixed acid solution on the surface of the silicon wafer and the impurities of the corroded phosphorosilicate glass and borosilicate glass are cleaned.
Step four: the silicon wafer treated by the mixed acid is treated by the organic solvent, the organic solvent is absolute ethyl alcohol, the purpose of treating the silicon wafer by the absolute ethyl alcohol is to absorb the moisture on the surface of the silicon wafer, absorb the mixed acid which is not cleaned on the surface of the silicon wafer, and simultaneously remove other impurities on the surface of the silicon wafer to rapidly dehydrate the silicon wafer. The absolute ethyl alcohol treatment comprises the following specific steps:
step S17: placing the silicon wafers subjected to mixed acid treatment in absolute ethyl alcohol for dehydration treatment, absorbing water on the surfaces of the silicon wafers, wherein the dehydration time is 10-30s, selecting the number of the silicon wafers treated each time according to a container containing the absolute ethyl alcohol, generally selecting 1500-2000 silicon wafers treated each time, and ensuring that each silicon wafer can be contacted with the absolute ethyl alcohol.
Step S18: placing the silicon wafer dehydrated by absolute ethyl alcohol into a nitrogen box for nitrogen drying within 30min, wherein the flow rate of nitrogen in the nitrogen box is 30-60L/min, the purpose of nitrogen blowing is to dry the moisture on the surface of the silicon wafer, placing the silicon wafer dried by nitrogen into an oven for drying, opening the oven in advance before drying so as to enable the temperature of the oven to reach a set temperature, ensuring that the oven is in a set temperature range before the silicon wafer enters the oven, and drying the silicon wafer in the oven at constant temperature, wherein the oven is an infrared oven, heating and drying the silicon wafer by infrared, the set temperature of the oven is 80-100 ℃, the baking time is 30-90min, and the purpose of baking by the oven is to further dry the moisture of the silicon wafer so as to enable the surface of the silicon wafer to reach the dryness within the specification, and after the drying time is over, taking out the silicon wafer and naturally cooling the silicon wafer.
Step S19: and (3) performing appearance sampling inspection on the silicon wafer after absolute ethyl alcohol and drying, wherein the phosphorus surface is grey white, no obvious colored pattern is a qualified piece, the unqualified silicon wafer is reworked, and the acid treatment, the water cleaning, the mixed acid cleaning and the organic solvent cleaning are repeated, wherein the mixed acid treatment time is increased in the reworking process so as to ensure that the silicon wafer is qualified, and the additional mixed acid treatment time is 30-60 s.
The invention has the advantages and positive effects that: by adopting the technical scheme, the silicon wafer is more convenient and faster to clean after diffusion, the cleanliness of the surface of the silicon wafer can more easily meet the requirement of the production specification, hydrofluoric acid cleaning, pure water cleaning and mixed acid cleaning are sequentially adopted, phosphorosilicate glass and borosilicate glass after the surface of the silicon wafer is diffused can be removed, impurities on the surface of the silicon wafer can be cleaned, the cleanliness of the surface of the silicon wafer can meet the requirement of the production specification, preparation is made for subsequent procedures, the silicon wafer is cleaned by adopting absolute ethyl alcohol, the silicon wafer is quickly dehydrated, the adsorption of particle impurities on the surface of the silicon wafer is reduced, and the cleanliness of the surface of the silicon wafer is further ensured.
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 (1)
1. A cleaning process after silicon wafer diffusion is characterized in that: the method specifically comprises the following steps of,
s1: and (3) carrying out acid treatment on the diffused silicon wafer: soaking a silicon wafer in an acid solution, wherein the silicon wafer is soaked in the acid solution for 36-60 hours, and the acid solution is replaced every 10-15 hours, the acid treatment is hydrofluoric acid treatment, and the concentration of the hydrofluoric acid is 49% -60%; carrying out overflow cleaning on the silicon wafer after the acid treatment, wherein the overflow cleaning time is 30-60min, and the pure water flow during the overflow cleaning is 4-10L/min;
s2: carrying out mixed acid treatment on the silicon wafer subjected to acid treatment; the specific steps of the mixed acid treatment are as follows:
s21: preparing a mixed acid solution: the nitric acid, the hydrofluoric acid, the acetic acid and the pure water are configured according to the volume ratio of 2000-3000ml, 200-500ml, 100-300ml, 2000-3000 ml;
s22: placing a silicon wafer in the mixed acid solution for corrosion treatment, wherein the corrosion time is 10-30 s;
s23: cleaning the silicon wafer subjected to mixed acid corrosion treatment by pure water, wherein the cleaning time is 5-15min, and the flow of the pure water is 4-10L/min;
s3: carrying out organic solvent treatment on the silicon wafer treated by the mixed acid; the organic solvent treatment is absolute ethyl alcohol treatment, and the absolute ethyl alcohol treatment comprises the following steps:
s31: placing the silicon wafer subjected to mixed acid treatment in absolute ethyl alcohol for dehydration treatment, wherein the dehydration time is 10-30 s;
s32: drying the silicon wafer by using nitrogen, and placing the silicon wafer in a drying oven for drying;
s33: inspecting the silicon wafer;
and (3) performing appearance sampling inspection on the silicon wafer which is subjected to the organic solvent treatment, wherein the phosphorus surface is grey white, no obvious colored pattern is taken as a qualified wafer, the unqualified silicon wafer is reworked, and the acid treatment, the water cleaning, the mixed acid cleaning and the organic solvent cleaning are repeated, wherein the time of the mixed acid treatment is increased in the reworking process so as to ensure that the silicon wafer is qualified, and the time of the mixed acid treatment is 30-60 s.
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Address after: 300380 2nd floor, block a, No.12 Haitai East Road, Huayuan Industrial Zone, Xiqing District, Tianjin Patentee after: TCL Huanxin Semiconductor (Tianjin) Co.,Ltd. Address before: 300380 2nd floor, block a, No.12 Haitai East Road, Huayuan Industrial Zone, Xiqing District, Tianjin Patentee before: TIANJIN HUANXIN TECHNOLOGY & DEVELOPMENT Co.,Ltd. |
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