Cleaning method and batch-type cleaning equipment each for semiconductor wafer

Abstract

To provide a cleaning method and cleaning equipment each improving the cleaning efficiency in cleaning of a semiconductor wafer.SOLUTION: Batch-type cleaning equipment 10 is batch-type cleaning equipment for a semiconductor wafer, and includes at least one water washing tank 12 performing a cleaning process in which a semiconductor wafer 20 is washed a plurality of times by a QDR method, and the water washing tank 12 has a control function which limits the amount of water discharged per wash in the QDR method to 50% or less of the volume of the tank 12. Water with specific gravity having become greater than that of pure water due to contaminants is collected at the bottom of the tank, consequently the amount of pure water used can be reduced by discharging only the collected water.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present disclosure relates to a method for cleaning semiconductor wafers in a batch cleaning apparatus. [Background technology]

[0002] The semiconductor manufacturing process includes a process of cleaning semiconductor wafers. In this process, a multi-layer batch type cleaning device is used, which arranges tanks containing chemicals and tanks containing pure water, and immerses many wafers in these tanks at once to remove contaminants. Figure 1 is a diagram explaining the multi-layer batch type cleaning device.

[0003] Multi-layer batch cleaning equipment has the advantage of high processing capacity per unit time because it processes multiple wafers simultaneously. However, it has the problem that the processing tank needs to be large to process multiple wafers in a wafer cassette and immerse them all at once, which consumes a large amount of chemicals and pure water. In addition, since multiple wafers are cleaned using chemicals, it takes a long time to rinse with pure water to remove the chemicals remaining after cleaning.

[0004] QDR (Quick Dump Rinse) was devised to solve this problem. Figure 2 is a diagram explaining QDR. QDR is a method in which the inside of a tank is filled with pure water (Figure 2(A)), and the water is rapidly drained from the top to the bottom of the tank until it is empty (Figure 2(B)). By draining water in the same direction as gravity, it is possible to perform a rinse with high cleaning efficiency that generates a uniform downward flow, and it is an excellent cleaning method that is generally widely used (for example, see Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2001-189297 A Summary of the Invention [Problem to be solved by the invention]

[0006] One QDR cycle consists of "filling the tank with pure water" in Figure 2(A) and "draining all the pure water from the tank" in Figure 2(B). Even with the QDR method, there is a limit to the cleaning efficiency of a single QDR cycle, and in order to perform sufficient cleaning, the QDR cycle must be repeated multiple times. This uses a large amount of pure water, which increases manufacturing costs and the environmental burden, making it an issue to improve cleaning efficiency.

[0007] SUMMARY OF THE PRESENT DISCLOSURE In order to solve the above problems, an object of the present invention is to provide a cleaning method and a cleaning apparatus that improve the cleaning efficiency in cleaning semiconductor wafers. [Means for solving the problem]

[0008] In order to achieve the above object, the method for cleaning semiconductor wafers according to the present invention is such that the amount of water discharged per wash in the QDR system is 50% or less of the volume of the washing tank.

[0009] Specifically, the method for cleaning semiconductor wafers according to the present invention is a method for cleaning semiconductor wafers in a batch-type cleaning apparatus, characterized in that in a cleaning step in which the semiconductor wafers are cleaned multiple times by a QDR method in at least one water washing tank of the batch-type cleaning apparatus, the amount of wastewater discharged per time in the QDR method is 50% or less of the volume of the water washing tank.

[0010] Further, a batch-type cleaning apparatus according to the present invention is a batch-type cleaning apparatus for semiconductor wafers, comprising: The cleaning apparatus is characterized in that it is provided with at least one water washing tank for performing a cleaning process in which the semiconductor wafer is washed multiple times by the QDR method, and the water washing tank has a control function for limiting the amount of water discharged per wash in the QDR method to 50% or less of its own volume.

[0011] If the substance to be rinsed has a higher specific gravity than water, the concentration of the substance will be higher in the lower part of the washing tank than in the upper part. Therefore, by draining only the pure water in the lower part where the concentration of the substance is high (water whose specific gravity has become higher than that of the pure water due to the substance), the substance can be removed from the semiconductor wafer while reducing the amount of pure water used, thereby improving cleaning efficiency. Therefore, the present invention can provide a cleaning method and a cleaning apparatus that improve the cleaning efficiency in cleaning semiconductor wafers.

[0012] In addition, the method for cleaning semiconductor wafers according to the present invention is characterized in that the number of cleaning steps in the cleaning step is increased so that the total amount of wastewater in the cleaning step becomes equal to the amount of wastewater in a case where cleaning is performed without reducing the amount of wastewater per step.

[0013] The control function of the batch cleaning apparatus according to the present invention is characterized in that the number of cleaning cycles in the cleaning process is increased so that the total amount of wastewater discharged in the cleaning process becomes equal to the amount of wastewater discharged in a cleaning process without reducing the amount of wastewater discharged per cycle.

[0014] By reducing the amount of pure water used per QDR cycle, the number of QDR cycles can be increased, thereby improving the cleaning effect of the wafer.

[0015] The above-mentioned inventions can be combined as much as possible. Effect of the Invention

[0016] The present invention can provide a cleaning method and a cleaning apparatus that can improve the cleaning efficiency in cleaning semiconductor wafers. [Brief description of the drawings]

[0017] [Figure 1] FIG. 1 is a diagram illustrating a multi-layer batch type cleaning apparatus. [Diagram 2] FIG. 1 is a diagram illustrating QDR. [Diagram 3]1A to 1C are diagrams illustrating a semiconductor wafer cleaning method according to the present invention. [Figure 4] FIG. 1 is a diagram illustrating a cleaning device according to the present invention. [Diagram 5] FIG. 1 is a diagram illustrating the effects of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] The embodiments of the present invention will be described with reference to the accompanying drawings. The embodiments described below are examples of the present invention, and the present invention is not limited to the following embodiments. Note that components with the same reference numerals in this specification and drawings indicate the same components.

[0019] The semiconductor wafer cleaning method of this embodiment will be described with reference to FIGS. FIG. 4 is a diagram illustrating a batch-type cleaning apparatus 10 for carrying out the present cleaning method. The batch-type cleaning apparatus 10 is a batch-type cleaning apparatus for semiconductor wafers, and is equipped with at least one water rinsing tank 12 that performs a cleaning process in which semiconductor wafers 20 are cleaned multiple times by the QDR method, and the water rinsing tank 12 is characterized by having a control function that limits the amount of water discharged per cleaning in the QDR method to 50% or less of its own volume. The batch cleaning apparatus 10 includes a chemical bath 11 and a final water rinsing bath 13 in addition to the water rinsing bath 12. As shown in FIG.

[0020] FIG. 3 is a diagram illustrating the principle of this cleaning method. For example, when a semiconductor wafer with contaminants (such as sulfuric acid, a chemical used in semiconductor cleaning) that have a higher specific gravity than water is immersed in pure water in a washing tank, the concentration of the contaminants dissolved in the pure water will be higher in the lower part of the washing tank than in the upper part (Fig. 3(A)). In other words, the water, whose specific gravity has become higher than that of pure water due to the contaminants, collects in the lower part of the tank. Therefore, this cleaning method drains only the pure water containing the contaminants from the lower part, where the concentration is higher (Fig. 3(B)). The amount of pure water drained in this case is, for example, 50% of the volume of the washing tank.

[0021] Here, the contaminant concentration of the pure water remaining in the washing tank after the pure water at the bottom is drained (the pure water that was at the top before draining) is extremely low, and there is almost no reattachment of contaminants to the semiconductor wafers. Therefore, in this cleaning method, the pure water remaining in the washing tank is reused for the next cycle of cleaning. In other words, the first QDR cycle of this cleaning method is "filling the tank with pure water" in Figure 3(A) and "draining part of the pure water in the tank from the bottom" in Figure 3(B). As with the conventional method, the QDR cycle is repeated multiple times. The second and subsequent QDR cycles are "adding new pure water to the pure water remaining in the tank to fill the tank with pure water" in Figure 3(A) and "draining part of the pure water in the tank from the bottom" in Figure 3(B).

[0022] In other words, if the number of QDR cycles is the same, this cleaning method achieves the same degree of contaminant removal compared to conventional QDR cleaning (Figure 2) while consuming a smaller amount of pure water. Therefore, this cleaning method can efficiently remove contaminants from semiconductor wafers (while reducing the amount of pure water used).

[0023] In addition, the amount of pure water discharged and the number of QDR cycles in Fig. 3(B) may be set in the cleaning device according to the cleanliness level required for cleaning semiconductor wafers (specific resistivity of pure water in the final water rinsing tank). In other words, the amount of pure water discharged may be 50% or less of the volume of the water rinsing tank. In addition, the number of QDR cycles does not need to be the same as that of the conventional cleaning method, and the number of QDR cycles may be increased by the amount of pure water used in one QDR cycle being reduced.

[0024] (Example) FIG. 5 shows the results of an experiment to explain the effect of the cleaning method of the present embodiment. In this experiment, the chemical tank 11 was filled with sulfuric acid. First, the semiconductor wafer 20 was immersed in the chemical tank 11. The time for treating the semiconductor wafer 11 with sulfuric acid was the same in both the embodiment and the comparative example. Next, QDR was performed in the water rinsing tank 12. In the comparative example, all the pure water in the water rinsing tank 12 was drained as in the conventional case, and the QDR cycle was repeated 15 times. On the other hand, in the embodiment, only half the volume of the pure water in the water rinsing tank 12 was drained, and the QDR cycle was repeated 30 times. That is, in this experiment, the total amount of pure water used in the water rinsing tank 12 was the same. The semiconductor wafer 20 that had been subjected to QDR in the water rinsing tank 12 was immersed in the final water rinsing tank 13. Then, the transition of the resistivity value of the pure water in the final water rinsing tank 13 was measured.

[0025] 5 is a graph showing the transition of the pure water resistivity in the Example and the Comparative Example. The amount of pure water used was the same in the Example and the Comparative Example, but the pure water resistivity at the end of the treatment in the final water rinsing tank 13 (540 s) was higher in the Example, which had a larger number of DR cycles, than in the Comparative Example, resulting in a higher cleaning effect.

[0026] (effect) The cleaning method of the present invention can shorten the cleaning time and reduce the amount of pure water used in a pretreatment cleaning apparatus for semiconductor wafers (especially a multi-tank batch type cleaning apparatus), and can improve the cleaning efficiency by improving the cleaning effect with the same amount of pure water used. [Explanation of symbols]

[0027] 10: Batch cleaning equipment 11: Chemical tank 12:Washing tank 13:Final washing tank 20: Semiconductor wafer

Claims

1. A method for cleaning semiconductor wafers in a batch-type cleaning apparatus, comprising: In a cleaning step of cleaning the semiconductor wafer multiple times by a QDR method in at least one water cleaning tank of the batch cleaning apparatus, A method for cleaning semiconductor wafers, characterized in that the amount of water discharged per one cycle in said QDR system is 50% or less of the volume of said water washing tank.

2. 2. The method for cleaning semiconductor wafers according to claim 1, wherein the number of cleanings in the cleaning step is increased so that a total amount of wastewater in the cleaning step becomes equal to an amount of wastewater in a case where the amount of wastewater per cleaning step is not reduced.

3. A batch cleaning apparatus for semiconductor wafers, comprising: The semiconductor wafer is washed multiple times by a QDR method using at least one water washing tank. The batch-type cleaning apparatus is characterized in that the washing tank has a control function for limiting the amount of wastewater discharged per one use in the QDR system to 50% or less of its own volume.

4. 4. The batch cleaning apparatus according to claim 3, wherein the control function increases the number of cleanings in the cleaning process so that a total amount of drainage in the cleaning process becomes equal to an amount of drainage in a case where cleaning is performed without reducing the amount of drainage per cleaning.

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