CN109427543B - Method for cleaning silicon wafer - Google Patents
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- CN109427543B CN109427543B CN201710769387.0A CN201710769387A CN109427543B CN 109427543 B CN109427543 B CN 109427543B CN 201710769387 A CN201710769387 A CN 201710769387A CN 109427543 B CN109427543 B CN 109427543B
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- 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
- H01L21/02052—Wet cleaning only
Abstract
The method for cleaning a silicon wafer of the present invention is characterized by comprising the steps of sequentially immersing a silicon wafer: (1) immersing in an aqueous solution of dissolved ozone or the like; (2) immersing in an aqueous solution containing hydrogen peroxide and ammonium hydroxide; (3) immersing in an aqueous solution of dissolved ozone or the like; (4) immersing in an aqueous solution containing an organic acid or an organic acid salt having a carboxyl group and hydrofluoric acid; (5) immersing in an aqueous solution containing an organic acid or an organic acid salt containing a carboxyl group; (6) immersing in pure water; and (7) immersing in an aqueous solution of dissolved ozone or the like. Thus, not only large particles having a particle size of 0.1 μm or more but also small particles having a particle size of 0.045 μm or less and intermediate particles having a particle size of more than 0.045 μm and less than 0.1 μm can be reduced.
Description
Technical Field
The present invention relates to a method for cleaning a silicon wafer.
Background
On the surface of a silicon wafer, metal impurities, fine particles having a particle diameter of 1 μm or less, organic substances, and the like adhere in the production process, and processing damage is formed. With the high integration and high functionality of semiconductor devices, there is an increasing demand for a technique for cleaning a silicon wafer, which is free from process damage and contamination of the surface of the silicon wafer with such metal impurities, particles and organic substances, and which satisfies this demand, is extremely important in the entire semiconductor device technology.
Patent document 1 describes a method for cleaning a silicon wafer, which comprises the following steps: a step (11) of immersing the silicon wafer in an aqueous solution (so-called SC-1 solution) containing hydrogen peroxide and ammonium hydroxide; thereafter, a step (12) of immersing the silicon wafer in an oxidizing solution containing 1 or 2 or more species selected from the group consisting of an aqueous solution of dissolved ozone, nitric acid, and an aqueous solution of hydrogen peroxide; thereafter, a step (13) of immersing the silicon wafer in an aqueous solution containing an organic acid or an organic acid salt having a carboxyl group and hydrofluoric acid; thereafter, a step (14) of immersing the silicon wafer in an aqueous solution containing an organic acid or an organic acid salt containing a carboxyl group; and (15) immersing the silicon wafer in an oxidizing solution containing 1 or 2 or more species selected from the group consisting of an aqueous solution of dissolved ozone, nitric acid, and an aqueous solution of hydrogen peroxide. It is said that the cleaning method can remove fine damages caused by the processing and organic substances, metal impurities and fine particles adhering to the surface of the silicon wafer with a small number of steps and in a satisfactory manner.
Documents of the prior art
Patent document
Patent document 1: japanese patent laid-open No. 2000-138198.
Disclosure of Invention
Problems to be solved by the invention
In patent document 1, in the examples thereof, the number of fine particles having a particle size of 0.12 μm or more remaining on the surface of a silicon wafer after washing was evaluated by a particle counter. Further, the washing method of patent document 1 shows that such large particles can be effectively removed and reduced.
However, in patent document 1, no consideration or evaluation is made with respect to fine particles having a particle diameter of less than 0.12 μm. In the case of high integration and high functionality of semiconductor devices, cleaning for effectively removing small particles is also required. Therefore, the present inventors have conducted studies and experiments to find that: although the washing method of patent document 1 can surely remove and reduce large particles having a particle size of 0.1 μm or more effectively, the removal and reduction effects are insufficient for small particles having a particle size of 0.045 μm or less and intermediate particles having a particle size of more than 0.045 μm and less than 0.1. mu.m.
In view of the above problems, an object of the present invention is to provide: a method for cleaning a silicon wafer, which can reduce not only large particles having a particle diameter of 0.1 μm or more but also small particles having a particle diameter of 0.045 μm or less and intermediate-sized particles having a particle diameter of more than 0.045 μm and less than 0.1 μm.
Means for solving the problems
The present inventors have made intensive studies to achieve the above object and obtained the following findings. First, in the washing method of patent document 1, the present inventors considered that the following 2 points may be a cause of a large amount of remaining of small particles and intermediate-sized particles: (A) the organic matter removing effect of the washing step (11) with the SC-1 solution may be insufficient; (B) after the steps (13) and (14), there is a possibility that an organic acid remains on the surface of the silicon wafer.
Therefore, as a countermeasure for (a), it is assumed that: a cleaning step of immersing the silicon wafer in an oxidizing solution such as an aqueous ozone solution is added before the step of cleaning the silicon wafer with the SC-1 solution (11), and organic substances on the surface of the silicon wafer are removed by the cleaning step. As a countermeasure for (B), it is assumed that: immediately after the step (14), a washing step of immersing the silicon wafer in pure water is added, and the remaining organic acid is removed by this washing step. Further, according to the experiments of the present inventors, it was found that small particles and intermediate-sized particles can be effectively removed by adding the above 2 washing steps.
And, surprisingly, it was found that: with respect to the intermediate-sized particles, when only either one of the washing step of adding the oxidizing liquid before the washing step (11) and the washing step of adding the pure water immediately after the step (14) is performed, the removal effect of the intermediate-sized particles is insufficient, but by performing both of them, the removal effect of the intermediate-sized particles is significantly enhanced.
The present invention has been completed based on the above findings, and the gist thereof is as follows.
(1) A method for cleaning a silicon wafer, comprising the steps of:
a 1 st step of immersing the silicon wafer in a 1 st oxidizing solution containing 1 or 2 or more species selected from the group consisting of an aqueous solution of dissolved ozone, nitric acid and an aqueous solution of hydrogen peroxide;
a 2 nd step of immersing the silicon wafer in an aqueous solution containing hydrogen peroxide and ammonium hydroxide after the 1 st step;
a 3 rd step of immersing the silicon wafer in a 2 nd oxidizing solution containing 1 or 2 or more kinds selected from the group consisting of an aqueous solution of dissolved ozone, nitric acid, and an aqueous solution of hydrogen peroxide, after the 2 nd step;
a 4 th step of immersing the silicon wafer in an aqueous solution containing an organic acid or an organic acid salt having a carboxyl group and hydrofluoric acid after the 3 rd step;
a 5 th step of immersing the silicon wafer in an aqueous solution containing an organic acid or an organic acid salt containing a carboxyl group, after the 4 th step;
a 6 th step of immersing the silicon wafer in pure water after the 5 th step; and
and a 7 th step of immersing the silicon wafer in a 3 rd oxidizing solution containing 1 or 2 or more kinds selected from the group consisting of an aqueous solution of dissolved ozone, nitric acid and an aqueous solution of hydrogen peroxide, after the 6 th step.
(2) The method for cleaning a silicon wafer according to item (1), wherein the 1 st oxidizing solution, the 2 nd oxidizing solution and the 3 rd oxidizing solution are 1 st to 3 rd dissolved ozone aqueous solutions, respectively.
(3) The method for cleaning a silicon wafer according to item (2) above, wherein the ozone concentration in the 1 st and 2 nd dissolved ozone aqueous solutions is 5ppm or more and 10ppm or less, and the ozone concentration in the 3 rd dissolved ozone aqueous solution is 15ppm or more and 30ppm or less.
(4) The method for cleaning a silicon wafer according to any one of the above (1) to (3), wherein a concentration of hydrofluoric acid in the aqueous solution used in the 4 th step is 0.05 mass% or more and 1.0 mass% or less.
(5) The method for cleaning a silicon wafer according to any one of the above (1) to (4), wherein the concentration of the organic acid or organic acid salt in the aqueous solution used in the 4 th step and the 5 th step is 0.001% by mass or more.
(6) The method for cleaning a silicon wafer according to any one of the above (1) to (5), wherein the organic acid or organic acid salt is 1 or 2 or more organic acids or salts thereof selected from the group consisting of: oxalic acid, citric acid, succinic acid, ethylenediaminetetraacetic acid, tartaric acid, salicylic acid, formic acid, maleic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, benzoic acid, acrylic acid, adipic acid, malonic acid, malic acid, glycolic acid, phthalic acid, terephthalic acid, and fumaric acid.
Effects of the invention
According to the method for cleaning a silicon wafer of the present invention, not only large particles having a particle diameter of 0.1 μm or more but also particles having a small and reliable particle diameter of 0.045 μm or less and an intermediate size of more than 0.045 μm and less than 0.1 μm can be reduced.
Drawings
Fig. 1 is a flowchart showing each step of a method for cleaning a silicon wafer according to an embodiment of the present invention.
Detailed Description
Hereinafter, a method for cleaning a silicon wafer according to an embodiment of the present invention will be described with reference to fig. 1. The cleaning method of the present embodiment is not a single wafer cleaning but a batch cleaning, which is a final cleaning before delivery of the silicon wafer finished with the polishing of the finished product.
(step 1)
First, as shown in S1 in fig. 1, a 1 st step of immersing a silicon wafer in a 1 st oxidizing solution containing 1 or 2 or more species selected from a dissolved ozone aqueous solution, nitric acid, and a hydrogen peroxide aqueous solution is performed. In step 1, S1, organic fine particles and the like adhering to the surface of the silicon wafer are removed by chemical oxidation. In particular, ozone has a strong organic substance decomposition ability, and is therefore more advantageous in removing organic fine particles and the like adhering to the wafer surface. Therefore, the 1 st oxidizing solution is preferably an aqueous solution in which ozone is dissolved. The 1 st step is an important step for effectively reducing the intermediate-sized particles having a particle diameter of more than 0.045 μm and less than 0.1 μm in combination with the 6 th step described later.
The concentration of ozone in the dissolved ozone aqueous solution is preferably 5ppm or more and 10ppm or less. When the concentration of ozone is 5ppm or more, the desired effect described in the previous paragraph can be sufficiently obtained, and when the concentration of ozone is 10ppm or less, an expensive ozone generator is not required, which is advantageous in terms of cost.
The immersion time in this step is not particularly limited, but is preferably 3 minutes to 10 minutes. When the time is 3 minutes or more, the above-mentioned desired action and effect can be sufficiently obtained, and when the time is 10 minutes or less, the washing efficiency is not impaired. The temperature of the 1 st oxidizing solution is not particularly limited, and may be, for example, 15 ℃ to 30 ℃ inclusive, typically room temperature (25 ℃).
(step 2)
Next, as shown in S2 of fig. 1, the 2 nd step of immersing the silicon wafer in an aqueous solution (SC-1 solution) containing hydrogen peroxide and ammonium hydroxide is performed. In the 2 nd step S2, the reduction by ammonia and the oxidation by hydrogen peroxide compete with each other in the same tank, and the surface of the silicon wafer is simultaneously oxidized and reduced, whereby a damaged micro layer having a thickness of about several nanometers on the surface of the wafer can be effectively removed. In addition, particles and organic matters can be removed from the surface of the wafer by the etching action of the ammonium hydroxide solution, and minute damage generated on the wafer due to processing can be removed. The washing in the 2 nd step is preferably carried out by ultrasonic washing. This can reduce uneven cleaning on the wafer surface.
The hydrogen peroxide concentration and the ammonium hydroxide concentration in the aqueous solution used in the present step may be within the range of a normal SC-1 solution, and specifically, the hydrogen peroxide concentration may be 1.5 to 4.0 mass%, and the ammonium hydroxide concentration may be 0.3 to 2.0 mass%.
The immersion time in this step is not particularly limited, but is preferably 3 minutes to 10 minutes. When the time is 3 minutes or more, the above-mentioned desired action and effect can be sufficiently obtained, and when the time is 10 minutes or less, the washing efficiency is not impaired. The temperature of the aqueous solution is not particularly limited, but is preferably 40 ℃ to 80 ℃. This is because the particle removal ability can be sufficiently ensured at 40 ℃ or higher, and the surface roughness of the wafer surface does not become excessively rough at 80 ℃ or lower.
(step 3)
In the SC-1 solution treatment in step 2, metal impurities and fine particles may be reattached. Then, as shown in S3 of fig. 1, the 3 rd step of immersing the silicon wafer in the 2 nd oxidizing solution containing 1 or 2 or more species selected from the group consisting of the dissolved ozone aqueous solution, nitric acid and the hydrogen peroxide aqueous solution is performed. In the 3 rd step S3, the density of the oxide film formed after the 2 nd step is further increased by chemical oxidation, and thus the metal impurities and particles are easily removed from the wafer surface by dissolving the oxide film in the next 4 th step. In particular, the dissolved ozone aqueous solution is rich in oxidizing ability at low concentrations and is easily available. Therefore, the 2 nd oxidizing solution is preferably an aqueous solution in which ozone is dissolved.
The concentration of ozone in the dissolved ozone aqueous solution is preferably 5ppm to 10 ppm. When the concentration of ozone is 5ppm or more, the desired effect described in the previous paragraph can be sufficiently obtained, and when the concentration of ozone is 10ppm or less, an expensive ozone generator is not required, which is advantageous in terms of cost.
The immersion time in this step is not particularly limited, but is preferably 3 minutes to 10 minutes. When the time is 3 minutes or more, the above-mentioned desired action and effect can be sufficiently obtained, and when the time is 10 minutes or less, the washing efficiency is not impaired. The temperature of the second oxidation liquid 2 is not particularly limited, and may be, for example, 15 ℃ to 30 ℃ inclusive, and typically may be room temperature (25 ℃).
(step 4)
Next, as shown in S4 of fig. 1, a 4 th step of immersing the silicon wafer in an aqueous solution containing an organic acid or an organic acid salt having a carboxyl group and hydrofluoric acid is performed. In the 4 th step S4, the metal impurities and particles doped into the oxide film in the 2 nd and 3 rd steps are removed from the wafer surface by dissolving the oxide film. Specifically, the following phenomenon is considered to occur. First, hydrofluoric acid dissolves the oxide film to completely remove the oxide film from the wafer surface. Immediately after the metal impurities and particles are detached from the wafer surface, the metal impurities form metal complex salts by organic acid ions. The complex ion of the metal complex salt is a negative ion. In addition, the surface of the wafer from which the oxide film is removed and the surface of the released particles are both negatively charged by adsorption of organic acid ions. As a result, the re-adhesion of metal impurities and particles to the wafer surface can be prevented.
By changing the kind and concentration of the organic acid or the organic acid salt, the metal complexing effect based on the organic acid ion and the surface potential (zeta potential) of the metal complex salt can be controlled. That is, the complex-forming ability of the organic acid ion is chemically determined according to the complex stability constant of the organic acid ion and the metal ion forming the complex. The larger the constant, the more capable of promoting complex ion formation. As previously described, the charge of the metal ion changes from positive to negative by forming a complex ion.
The kind and concentration of the organic acid or organic acid salt in the aqueous solution used in this step are determined according to the kind of the metal impurities to be removed. The concentration of the organic acid or organic acid salt is preferably 0.001% by mass or more, more preferably 0.003 to 10% by mass. When the amount is 0.001 mass% or more, the complexing action of the metal impurity ions released from the wafer surface becomes sufficient.
Examples of the organic acid or organic acid salt used in the present step include 1 or 2 or more organic acids or salts thereof selected from the following: oxalic acid, citric acid, succinic acid, ethylenediaminetetraacetic acid, tartaric acid, salicylic acid, formic acid, maleic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, benzoic acid, acrylic acid, adipic acid, malonic acid, malic acid, glycolic acid, phthalic acid, terephthalic acid, and fumaric acid. The organic acids or organic acid salts listed above have a complexing effect on metal ions that contaminate the wafer impurities.
The concentration of hydrofluoric acid in the aqueous solution used in this step is preferably 0.05% by mass or more and 1.0% by mass or less, and more preferably 0.1% by mass or more and 0.5% by mass or less. When the amount is 0.05% by mass or more, the peeling effect of the natural oxide film on the wafer surface can be sufficiently obtained, and when the amount is 1.0% by mass or less, the reattachment of fine particles in the liquid is hardly caused.
The immersion time in this step is not particularly limited, but is preferably 3 minutes to 10 minutes. When the time is 3 minutes or more, the above-mentioned desired action and effect can be sufficiently obtained, and when the time is 10 minutes or less, the washing efficiency is not impaired. The temperature of the aqueous solution is not particularly limited, and may be, for example, 15 ℃ to 30 ℃ inclusive, and typically may be room temperature (25 ℃).
(step 5)
Next, as shown in S5 of fig. 1, a 5 th step of immersing the silicon wafer in an aqueous solution containing an organic acid or organic acid salt containing a carboxyl group is performed. In the 5 th step S5, the metal impurities and particles remaining on the wafer surface without being completely removed in the 4 th step are further effectively removed. These metal impurities and fine particles are residues of the solid-liquid interface in the step 4, are in an equilibrium state in the water film forming the solvent molecular layer on the wafer surface, and are not adsorbed on the wafer surface. The metal impurities form metal complex salts by organic acid ions. Organic acid ions are adsorbed in the particles. As a result, the metal complex salt and the fine particles, which have been negatively charged by the organic acid ions, are easily released from the wafer surface, as in the case of the 4 th step. In the 5 th step, a solution containing an organic acid or an organic acid salt having the same composition as that in the 4 th step may be used, and the concentration or the kind of the organic acid or the organic acid salt may be changed.
The kind and concentration of the organic acid or organic acid salt in the aqueous solution used in this step are determined according to the kind of the metal impurities to be removed. The concentration of the organic acid or organic acid salt is preferably 0.001% by mass or more, more preferably 0.003 to 10% by mass. When the amount is 0.001 mass% or more, the complexing action of the metal impurity ions released from the wafer surface becomes sufficient.
The organic acid or organic acid salt suitably used in this step is the same as that exemplified in step 4.
It is preferable that a trace amount of hydrofluoric acid is further added to the aqueous solution used in this step. Thus, the natural oxide film formed on the wafer surface can be slightly etched, and the fine particles and metal impurities on the natural oxide film can be easily transferred to the aqueous solution. That is, the addition of hydrofluoric acid can remove the metal impurities in the natural oxide film as well as the natural oxide film. In this case, the concentration of hydrofluoric acid is preferably 0.1 mass% or less, and more preferably 0.01 mass% or less. If the amount exceeds 0.1 mass%, the natural oxide film on the surface is excessively etched, and the surface potential of the wafer in the aqueous solution varies, which may cause re-adhesion of particles and metal.
The immersion time in this step is not particularly limited, but is preferably 3 minutes to 10 minutes. When the time is 3 minutes or more, the above-mentioned desired action and effect can be sufficiently obtained, and when the time is 10 minutes or less, the washing efficiency is not impaired. The temperature of the aqueous solution is not particularly limited, and may be, for example, 15 ℃ to 30 ℃ inclusive, and typically may be room temperature (25 ℃).
(step 6)
Next, as shown in S6 of fig. 1, a 6 th step of immersing the silicon wafer in pure water is performed. In step 6, S6, the organic acid or organic acid salt used in steps 4 and 5 is removed from the residual components and organic substances adhering to the wafer surface. That is, the organic substances adhering to the wafer surface are removed in the 6 th step before being oxidized and adhering to the wafer surface in the 7 th step. The 6 th step is an important step for effectively reducing the intermediate-sized particles having a particle diameter of more than 0.045 μm and less than 0.1 μm in combination with the 1 st step described above.
The immersion time in this step is not particularly limited, but is preferably 3 minutes to 10 minutes. When the time is 3 minutes or more, the above-mentioned desired action and effect can be sufficiently obtained, and when the time is 10 minutes or less, the washing efficiency is not impaired. The temperature of pure water is not particularly limited, but is preferably 15 ℃ to 50 ℃, and more preferably 18 ℃ to 25 ℃.
(step 7)
Finally, as shown in S7 of fig. 1, a 7 th step of immersing the silicon wafer in a 3 rd oxidizing solution containing 1 or 2 or more species selected from the group consisting of a dissolved ozone aqueous solution, nitric acid, and a hydrogen peroxide aqueous solution is performed. In the 7 th step S7, first, the effect of removing silicide-type metals (particularly Cu) contaminating the wafer surface and its vicinity is improved; second, the organic matter adhered to the wafer surface without being completely removed in the step 6 is decomposed and removed; thirdly, the surface of the wafer after washing is chemically protected by an oxide film. Cu is directly dissolved in a slightly acidic solution having a high oxidation potential and removed. Further, the surface of the wafer is protected by a chemical oxide film, thereby reliably preventing the adhesion of particles on the solid-gas interface. In particular, the dissolved ozone aqueous solution is rich in oxidizing ability at low concentrations and is easily available. Therefore, the 3 rd oxidizing solution is preferably an aqueous solution in which ozone is dissolved.
The concentration of ozone in the dissolved ozone aqueous solution is preferably 15ppm to 30 ppm. In this step, the residual organic acid needs to be decomposed, and therefore, the concentration of ozone needs to be higher than the concentration of ozone in the 1 st step and the 3 rd step, and the concentration of ozone is preferably 15ppm or more. In addition, the limit of dissolution of ozone in pure water is about 30 ppm.
The immersion time in this step is not particularly limited, but is preferably 3 minutes to 10 minutes. When the time is 3 minutes or more, the above-mentioned desired action and effect can be sufficiently obtained, and when the time is 10 minutes or less, the washing efficiency is not impaired. The temperature of the 3 rd oxidizing solution is not particularly limited, and may be, for example, 15 ℃ to 30 ℃ inclusive, and typically may be room temperature (25 ℃).
According to the method for cleaning a silicon wafer of the present embodiment described above, not only large particles having a particle diameter of 0.1 μm or more but also small particles having a particle diameter of 0.045 μm or less and intermediate particles having a particle diameter of more than 0.045 μm and less than 0.1 μm can be reduced.
Examples
(examples of the invention)
The 25 unwashed silicon wafers that had been polished to a finish according to a conventional method were subjected to a cleaning treatment under the following conditions. First, as a 1 st step, each wafer was immersed in an aqueous solution of dissolved ozone having an ozone concentration of 5ppm at a liquid temperature of 25 ℃ for 5 minutes. Next, as the 2 nd step, each wafer was immersed in an SC-1 solution (H) having a liquid temperature of 60 ℃ 2 O 2 Concentration: 2.6% by mass, NH 4 OH concentration: 0.6 mass%, remainder: a mixture of pure water) for 5 minutes. This procedure was carried out by ultrasonic washing. Next, as the 3 rd step, each wafer was immersed in an aqueous solution of dissolved ozone having an ozone concentration of 5ppm at a liquid temperature of 20 ℃ for 5 minutes. Next, as a 4 th step, an aqueous solution obtained by adding 0.05 mass% hydrofluoric acid to a solution obtained by mixing 0.06 mass% oxalic acid as an organic acid with respect to pure water was prepared, and each wafer was immersed at a liquid temperature of 20 ℃ for 5 minutes. Next, as a 5 th step, a solution in which 0.6 mass% of oxalic acid as an organic acid was added to pure water was prepared, and each wafer was immersed at a liquid temperature of 20 ℃ for 5 minutes. Next, as the 6 th step, each wafer was immersed in pure water at a liquid temperature of 20 ℃ for 5 minutes. Finally, as the 7 th step, each wafer was immersed in an aqueous solution of dissolved ozone having an ozone concentration of 20ppm at a liquid temperature of 20 ℃ for 5 minutes.
Comparative example 1
25 silicon wafers were washed by the same method as in the present invention example except that the 1 st step and the 6 th step were not performed. This washing method corresponds to the washing method described in patent document 1.
Comparative example 2
25 silicon wafers were washed by the same method as in the inventive example except that only the 6 th step was not performed. This washing method corresponds to the washing method described in patent document 1, in which only the 1 st step is added.
Comparative example 3
25 silicon wafers were washed by the same method as in the present invention example except that the 1 st step was not performed. This washing method corresponds to the washing method described in patent document 1, in which only the 6 th step is added.
< evaluation of the number of particles >
LPD having a particle size of 0.1 μm or more, LPD having a particle size of more than 0.045 μm and less than 0.1 μm, and LPD having a particle size of 0.045 μm or less were measured on the surface of each wafer after washing by a laser particle counter (SP-2, manufactured by KLA-tencor Co., Ltd.). The average number of LPDs of 25 LPDs in the inventive examples and comparative examples 1 to 3 is shown in table 1.
[ Table 1]
As is clear from Table 1, in the present invention examples, large particles having a particle diameter of 0.1 μm or more can be sufficiently reduced as in comparative examples 1 to 3. In the present invention example, it is also possible to sufficiently reduce small particles having a particle diameter of 0.045 μm or less and intermediate particles having a particle diameter of more than 0.045 μm and less than 0.1 μm. In particular, although the reduction effect is not much obtained in comparative example 2 in which only the 1 st step is added or comparative example 3 in which only the 6 th step is added to the washing method described in patent document 1, the reduction effect is dramatically increased in the present invention example in which both the 1 st step and the 6 th step are added.
Industrial applicability
According to the method for washing silicon wafers of the present invention, not only large particles having a particle diameter of 0.1 μm or more but also small particles having a particle diameter of 0.045 μm or less and intermediate particles having a particle diameter exceeding 0.045 μm and smaller than 0.1 μm can be reduced.
Description of the reference numerals
S1 Process 1
S2 No. 2
S3 Process 3
S4 No. 4
S5 the 5 th step
S6 No. 6
S7 step 7.
Claims (6)
1. A method for cleaning a silicon wafer, comprising the steps of:
a 1 st step of immersing the silicon wafer in a 1 st oxidizing solution containing 1 or 2 or more species selected from the group consisting of an aqueous solution of dissolved ozone, nitric acid and an aqueous solution of hydrogen peroxide;
a 2 nd step of immersing the silicon wafer in an aqueous solution containing hydrogen peroxide and ammonium hydroxide after the 1 st step;
a 3 rd step of immersing the silicon wafer in a 2 nd oxidizing solution containing 1 or 2 or more kinds selected from the group consisting of an aqueous solution of dissolved ozone, nitric acid, and an aqueous solution of hydrogen peroxide, after the 2 nd step;
a 4 th step of immersing the silicon wafer in an aqueous solution containing an organic acid or an organic acid salt having a carboxyl group and hydrofluoric acid after the 3 rd step;
a 5 th step of immersing the silicon wafer in an aqueous solution containing an organic acid or an organic acid salt containing a carboxyl group, after the 4 th step;
a 6 th step of immersing the silicon wafer in pure water after the 5 th step; and
and a 7 th step of immersing the silicon wafer in a 3 rd oxidizing solution containing 1 or 2 or more kinds selected from the group consisting of an aqueous solution of dissolved ozone, nitric acid, and an aqueous solution of hydrogen peroxide, after the 6 th step.
2. The method for cleaning a silicon wafer according to claim 1, wherein the 1 st oxidizing solution, the 2 nd oxidizing solution and the 3 rd oxidizing solution are 1 st to 3 rd dissolved ozone aqueous solutions, respectively.
3. A method for cleaning a silicon wafer as set forth in claim 2, wherein the ozone concentration in the 1 st and 2 nd dissolved ozone aqueous solutions is 5ppm or more and 10ppm or less, and the ozone concentration in the 3 rd dissolved ozone aqueous solution is 15ppm or more and 30ppm or less.
4. A method for cleaning a silicon wafer according to any one of claims 1 to 3, wherein the concentration of hydrofluoric acid in the aqueous solution used in the 4 th step is 0.05 mass% or more and 1.0 mass% or less.
5. A method for cleaning a silicon wafer according to any one of claims 1 to 4, wherein the concentration of the organic acid or organic acid salt in the aqueous solution used in the 4 th step and the 5 th step is 0.001% by mass or more.
6. The method for cleaning a silicon wafer according to any one of claims 1 to 5, wherein the organic acid or organic acid salt is 1 or 2 or more organic acids or salts thereof selected from the group consisting of: oxalic acid, citric acid, succinic acid, ethylenediaminetetraacetic acid, tartaric acid, salicylic acid, formic acid, maleic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, benzoic acid, acrylic acid, adipic acid, malonic acid, malic acid, glycolic acid, phthalic acid, terephthalic acid, and fumaric acid.
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| DE69916728T2 (en) * | 1998-08-28 | 2005-04-28 | Mitsubishi Materials Corp. | Method for cleaning a semiconductor substrate |
| JP3239998B2 (en) * | 1998-08-28 | 2001-12-17 | 三菱マテリアルシリコン株式会社 | Semiconductor substrate cleaning method |
| JP2004327878A (en) * | 2003-04-28 | 2004-11-18 | Sumitomo Mitsubishi Silicon Corp | Method of washing silicon wafer |
| KR101232249B1 (en) * | 2004-08-10 | 2013-02-12 | 간또 가가꾸 가부시끼가이샤 | Semiconductor substrate cleaning liquid and semiconductor substrate cleaning process |
| JP4613744B2 (en) * | 2005-08-10 | 2011-01-19 | 株式会社Ｓｕｍｃｏ | Cleaning method of silicon wafer |
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