JPH07142436A - Cleaning liquid and cleaning method for silicon wafer - Google Patents

Abstract

PURPOSE:To allow etching on the surface of a silicon wafer while controlling the etching amount by employing a cleaning liquid containing HNO3, HF, HCL and a surfactant, respectively, by specified wt.%. CONSTITUTION:The concentration of gHNO3 is set in the range of 35-65wt.%, preferably in the range of 45-55wt.%, the concentration of HF is set in the range of 0.05-0.5wt.%, preferably in the range of 0.1-0.3wt.%, and the concentration of HCl is set in the range of 0.05-0.5wt.%, preferably in the range of 0.1-0.3wt.%. The concentration of surfactant in the cleaning liquid is set in the range of 0.002-0.1wt.%, preferably in the range of 0.002-0.05wt.%. The surfactant includes polyoxyethylene alkylether, for example. This composition allows etching on the surface of a silicon wafer while controlling the etching amount to several tens Angstrom , especially to 20-30Angstrom .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silicon wafer cleaning liquid which is useful in a semiconductor silicon wafer manufacturing process, a semiconductor device manufacturing process and the like, and a silicon wafer cleaning method using the cleaning liquid.

[0002]

2. Description of the Related Art As a cleaning liquid widely used for removing high-level heavy metal contamination on the surface of a semiconductor silicon wafer, for example, a liquid composed of hydrochloric acid, hydrogen peroxide and water called SC-2 of RCA method (hereinafter referred to as SC-2) SC-2), nitric acid, aqua regia etc. are known. Cleaning of a silicon wafer using these cleaning solutions is usually carried out by holding the silicon wafer in a fluororesin carrier and immersing the silicon wafer in these cleaning solutions for a predetermined time. When a silicon wafer is dipped in the above cleaning liquid, the heavy metal on the surface of the silicon wafer is dissolved and removed. However, when we examined the heavy metal removal effect of these cleaning solutions by contamination with gold, which is the most difficult to remove among the heavy metals, the cleaning effect of aqua regia and SC-2 was about 10 ¹⁵ atoms / cm ² or more. However, if the degree of contamination is lower than this, the cleaning effect is insufficient, and if it is about 10 ¹³ atoms / cm ² or less, the cleaning effect cannot be obtained. This is because if the contamination is less than 10 ¹⁴ atoms / cm ² , a native oxide film is formed on the wafer surface during cleaning and gold atoms are trapped underneath.

Therefore, it is desirable to allow such an oxidizing agent to act while removing the natural oxide film. As such a cleaning liquid, the inventor of the present invention in Japanese Patent No. 613521 discloses aqua regia 1.
We have proposed a cleaning solution consisting of 10 parts by volume of HF and 0.3% or less of HF as a chemical agent for removing the natural oxide film. According to the above-mentioned patent, according to this method, the contamination of 10 ¹⁵ atoms / cm ² of gold is 10 ^{10 in} one cleaning treatment.
It has been shown that it can be reduced to atoms / cm ² . However, the etching action of the silicon wafer surface caused by the action of HNO ₃ and HF is strong because it is promoted by nitrosyl chloride and chlorine generated from aqua regia,
Depending on the HF concentration, the etching amount of this cleaning solution with respect to the silicon wafer may be 1 μm or more, and the microscopic unevenness (haze) generated on the surface of the silicon wafer impairs the mirror state of the surface. Further, when the HF concentration of the cleaning liquid is extremely lowered to such an extent that haze does not occur and the cleaning is performed, the etching amount remarkably varies due to a slight difference in the generation state of nitrosyl chloride or chlorine, which makes it difficult to control the cleaning conditions. Thus, this cleaning solution is not suitable for the manufacturing process of IC, LSI, etc.

Therefore, particularly when it is necessary to remove terrible heavy metal contamination, the process of dissolving the heavy metal using SC-2 or aqua regia and the etching process of removing the natural oxide film by dilute hydrofluoric acid are alternately performed. It is being repeated. However, although this cleaning method can remove easily oxidizable metals such as copper, it does not exert a sufficient cleaning effect on gold contamination.For example, dilute hydrofluoric acid-SC-2 treatment was repeated 10 times. However, the concentration of gold contamination on the surface can only be reduced to about 1/2.

By the way, in the semiconductor device manufacturing process, there is a process such as reactive ion etching (RIE) or ion implantation for giving a shallow but strong defect to the surface of a silicon wafer. Since heavy metals generally have a high diffusion rate and thus easily penetrate into such defective regions, a high degree of heavy metal contamination may occur in such a process. Therefore, for such contamination, a cleaning liquid capable of etching and removing the defective area itself is required. On the other hand, the etching should not impair the flatness of the silicon wafer surface. So, dozens of Å, especially
A cleaning solution and method that can control etching with a thickness of 20 to 30 Å are required. This is because the flatness is not impaired if the etching is performed in this range. Also,
In order to realize high productivity, it is desirable that cleaning can be performed by a simple contact treatment for a short time of about 1 minute.

[0006]

Therefore, an object of the present invention is to perform etching while controlling the surface of a silicon wafer with an etching amount of about several tens of liters, and to remove heavy metals such as gold at 10 ¹⁰ atoms / cm 2. A cleaning liquid and a cleaning method for a silicon wafer that can be removed or reduced to ² or less.

[0007]

The present invention provides, as a means for solving the above problems, 35 to 65% by weight of HNO ₃ , 0.05 to 0.
5% by weight HF, 0.05-0.5% by weight HCl and 0.002-0.
Provided is a silicon wafer cleaning liquid containing 1% by weight of a surfactant.

The present invention will be described in detail below. Surfactant As a surfactant , it does not contain metal components and has good wetting and penetrating power to silicon wafers, that is, good wettability and good chemical stability in oxidizing acid solution. For example, any of nonionic, amphoteric and cationic surfactants may be used. Specifically, for example, oxyethylene polymerization adducts such as polyoxyethylene alkyl ether and polyoxyethylene alkylphenol ether; imidazolinium betaine-type amphoteric surfactants; fluorine-based surfactants (perfluoroalkyl if nonionic) Amine oxide, perfluoroalkyl betaine if amphoteric, quaternary ammonium salt similar to perfluoroalkyltrimethylammonium if cationic, and the like. More specifically, the oxyethylene polymerization adduct is, for example,
It is advisable to use a polyoxyethylene nonylphenol ether having an oxyethylene addition mole number of about 10, specifically 9 to 13. Among the above surfactants, a fluorine-based surfactant having a perfluoroalkyl group in the molecule is most preferably used.

The concentration of the above surfactant in the cleaning solution is 0.00
It is 2 to 0.1% by weight, preferably 0.002 to 0.05% by weight. The concentration of the acid component HNO ₃ is 35 to 65% by weight, preferably 45 to 5%.
5% by weight. HF when the concentration of HNO ₃ is less than 35% by weight
Or, if the HCl concentration is not higher than 0.5%, a sufficient removal effect for Au cannot be obtained, and if it exceeds 65% by weight, an abnormal hydrophilic film is likely to occur on the wafer surface, and the cleaning surface integrity is controlled. Is difficult.

The concentration of HF is 0.05 to 0.5% by weight, preferably 0.1 to 0.3% by weight. HF concentration is 0.05% by weight
If it is less than 0, the removal effect on Au is significantly reduced, and
If it exceeds 5% by weight, it becomes difficult to control the etching amount, that is, to secure the flatness.

The concentration of HCl is 0.05 to 0.5% by weight,
It is preferably 0.1 to 0.3% by weight. If the HCl concentration is less than 0.05% by weight, the effect of removing Au is remarkably reduced, and if it exceeds 0.5% by weight, it becomes difficult to control the etching amount, that is, to secure the flatness. Other additives In the silicon wafer cleaning liquid of the present invention, organic acids (for example, acetic acid) for controlling etching and Br ₂ for strengthening oxidizing power are added within a range that does not impair the cleaning effect.
Etc. may be added. Preparation of Cleaning Solution In the cleaning method of the present invention, the cleaning effect is reduced depending on the preparation method of the cleaning solution. The most preferable preparation method is a method of adding calculated amounts of hydrofluoric acid, hydrochloric acid, and a pure water diluting solution of a surfactant aqueous solution in this order to 55 to 70% by weight of nitric acid. However, the order of hydrofluoric acid and hydrochloric acid may be reversed. However, if the addition of the surfactant precedes the hydrofluoric acid or hydrochloric acid, the cleaning effect is reduced. Thus, even if it is prepared by the preferred method, the cleaning effect of the cleaning solution is reduced after 2 hours. Therefore, it is desirable to perform the preparation just before the cleaning in the raw material liquid mixing tank directly connected to the cleaning device.

Since sufficient mixing is required at each stage of addition during the preparation, the mixing and preparing apparatus including the mechanism for measuring the raw material liquid is complicated and special care is required for the management. On the other hand, a two-liquid mixing method has been devised. According to this method, 1
A cleaning effect and etching amount with good reproducibility can be obtained by mixing and preparing once. The two-liquid mixing method is a method in which the above-mentioned four kinds of aqueous solutions and pure water are preliminarily combined in a suitable combination to prepare two liquids, and these two liquids are mixed at the time of cleaning to prepare a cleaning liquid.
Therefore, the cleaning liquid of the present invention may be provided as a two-liquid type of, for example, a liquid prepared by mixing hydrochloric acid, hydrofluoric acid, and a surfactant in pure water, and concentrated nitric acid. Further, it may be provided as a two-liquid type of a liquid containing concentrated nitric acid and hydrofluoric acid and a liquid containing hydrochloric acid and a surfactant. The two liquids thus provided are mixed at the time of use to prepare a cleaning liquid. Since these two-component type compounded liquids can be stored for a long period of time, they can be prepared in advance.

By adjusting the concentration of the above-mentioned acid component, it is possible to adjust the etching power with respect to the silicon wafer and hence the etching rate. Decrease the concentration of HCl and HF when the HNO ₃ concentration is high, and HC when the HNO ₃ concentration is low.
The required etching power can be obtained by increasing the concentrations of l and HF. Although a higher HNO ₃ concentration is likely to enhance the cleaning effect, environmental pollution due to the HNO ₃ atmosphere is likely to occur, so it is necessary to give sufficient consideration to the exhaust system. Therefore, it is desirable to select a composition with a low HNO ₃ concentration in cases such as immersion cleaning of wafers that use a large amount of chemicals. HNO ₃
Since the evaporation of water is suppressed, the environmental pollution can be significantly reduced even if the HNO ₃ concentration is increased to enhance the cleaning effect. Cleaning the silicon wafer by cleaning liquid in the cleaning invention of the silicon wafer, comprising a silicon wafer surface from contacting with the cleaning liquid. The heavy metal on the surface of the silicon wafer is dissolved and removed in the cleaning liquid. Generally, 30 seconds for silicon wafer
The desired cleaning is achieved by contacting the cleaning liquid for about 3 minutes. Specifically, by selecting the composition of the cleaning liquid,
For example, by contacting the surface of the silicon wafer with the cleaning solution of the present invention for about 1 minute, the contamination amount of gold, copper, iron and other heavy metals can be reduced to 1/100 or less of that before cleaning,
Furthermore, if the above cleaning is performed twice in succession, it can be reduced to 1/10000 or less.

The heavy metal dissolved in the cleaning liquid of the present invention rarely reversely adsorbs to the silicon wafer. For example, even if the copper concentration in the cleaning liquid reaches 100 ppb, the adsorption amount on the silicon wafer is on the order of 10 ⁸ atoms / cm ² . Therefore,
A sufficient cleaning effect can be obtained only by covering the silicon wafer with an extremely thin liquid layer of the cleaning liquid, for example, a liquid layer of 0.1 to 1 mm.

Since the cleaning liquid of the present invention contains a surfactant, it has a very high wettability with respect to a silicon wafer, and as a result, the entire surface of the wafer can be covered with a thin liquid layer as described above. Specifically, for example, a silicon wafer is held horizontally in a rotatable state, and the cleaning liquid of the present invention is dropped on the surface of the silicon wafer while being horizontally rotated to cover the entire surface of the wafer with a liquid layer ( For example, 10 to 20 cc may be dropped on a 6-inch silicon wafer). After the surface of the silicon wafer is uniformly covered with the cleaning liquid for a predetermined period of time, rinsed with pure water, and then a series of cleaning treatments (so-called paddle treatment) of increasing the rotation and drying by centrifugation are performed. Good. Drying may be performed by blowing a clean atmosphere. Also, holding the silicon wafer vertically and pouring or spraying the cleaning liquid from above, an extremely thin liquid layer of the cleaning liquid is formed on the surface of the silicon wafer and left for a predetermined time,
Cleaning may be performed by a series of steps of rinsing with pure water, wiping a warm and clean atmosphere and drying.

Generally, when a silicon wafer is washed with a cleaning liquid and then dried before being rinsed with pure water, the fine particles in the cleaning liquid adhere firmly to a dry region on the silicon wafer, It becomes difficult to remove fine particles with a pure water rinse. However, the cleaning liquid of the present invention has high wettability to a silicon wafer, and the silicon wafer is less likely to dry before being treated with a pure water rinse. In particular, the cleaning liquid containing a fluorine-based surfactant has high wettability, and for example, even if only 0.01% of the surfactant is mixed, it is possible to enter the pure water rinsing process while almost the entire surface of the silicon wafer remains wet. 0.02 surfactant
%, It is possible to obtain reliable wettability. In addition, even when a hydrocarbon-based surfactant is blended, sufficient wettability of the cleaning liquid can be obtained by adding almost twice as much hydrocarbon-based surfactant as when a fluorine-based surfactant is blended. .

[0017]

[Function] In the cleaning liquid of the present invention, the addition of a small amount of HF to HNO ₃ , which is the main component, etches the surface of a silicon wafer without forming a natural oxide film. Generate enough nitrosyl chloride to dissolve and remove surface metal contamination.

Nitrosyl chloride promotes etching, while the added surfactant acts to suppress etching, and the addition of a proper amount of the surfactant controls the amount of nitrosyl chloride generated sufficiently. . With these, the etching rate of silicon wafers is 20 to 30Å /
It is controlled to about a minute, and the flatness of the wafer surface after cleaning is not impaired.

[0019]

EXAMPLES Examples of the present invention will be shown below. The present invention is not limited to the following examples.

In each example,% in the composition of the cleaning liquid (aqueous solution) represents% by weight. Unless otherwise specified, the cleaning solution according to the present invention was prepared by adding hydrofluoric acid, hydrochloric acid, and a surfactant in this order to nitric acid.

The cleaning effect of the present invention was confirmed by a tracer method using a radioisotope (RI). For example, when confirming the cleaning effect on gold contamination, ¹⁹⁸ Au is used as a labeling element,
The cleaning effect was examined by comparing the radiation dose of ¹⁹⁸ Au on the surface of the silicon wafer before and after cleaning, and obtaining the ratio of the gold adhering to the silicon wafer after cleaning to that before cleaning (hereinafter referred to as the residual rate). did. For copper contamination and iron contamination, ⁶⁴ Cu and ⁵⁹ Fe were similarly used as labeling elements.

In the following, ¹⁹⁸ Au, ⁶⁴ Cu and ⁵⁹ Fe are
Gold, copper and iron labeled with ¹⁹⁸ Au, ⁶⁴ Cu and ⁵⁹ Fe respectively are shown. Example 1 A p-type semiconductor silicon wafer contaminated with ¹⁹⁸ Au of approximately 10 ¹³ atoms / cm ² [electrical resistivity: several Ωcm, crystal orientation: (10
[0]] was washed with a cleaning liquid (aqua regia or SC-2) or a cleaning liquid of the present invention, which has been conventionally considered to have a strong dissolving effect on gold metal, and the residual rate of ¹⁹⁸ Au after cleaning was compared. The results are shown in Table 1.

[0023]

[Table 1] In Table 1, (A) is the ¹⁹⁸ Au residual rate after the first washing, and (B) is the ¹⁹⁸ Au residual rate after the second washing. When aqua regia or SC-2 was used, the silicon wafer was treated with dilute hydrofluoric acid (HF: H ₂ O = 1: 10) immediately after the first cleaning, and then the second cleaning was performed. . On the other hand, when the cleaning solution of the present invention was used, the silicon wafer was not treated with dilute hydrofluoric acid, but rinsed with pure water, and then the second cleaning was performed.

From the results of this example, the cleaning with aqua regia or SC-2 can remove the gold contamination up to 45% at most even if the surface of the silicon wafer is cleaned twice in succession. On the other hand, when the cleaning solution of the present invention is used, even if there is 10 ¹³ atoms / cm ² of gold contamination on the silicon wafer surface,
It can be confirmed that the residual rate can be removed up to 0.6%, that is, the order of 10 ¹⁰ atoms / cm ² by cleaning twice, and the residual rate 0.02%, that is, the order of 10 ⁹ atoms / cm ² can be removed by performing the cleaning twice consecutively. It was It was also confirmed that the cleaning liquid of the present invention requires a short cleaning time of 1 minute. Example 2 A p-type semiconductor silicon wafer contaminated with ¹⁹⁸ Au containing approximately 10 ¹² atoms / cm ² of a cleaning liquid containing a surfactant and a cleaning liquid not containing a surfactant [electrical resistivity: several Ωcm, crystal orientation:
(100)] was washed and compared. Each silicon wafer was washed 5 times with the cleaning liquid having the composition shown in Table 2 and the stability of the cleaning effect was examined. The acid concentration of each cleaning solution in Table 2 was adjusted so that the etching amount for the silicon wafer was 15 Å on average at room temperature for 1 minute.
The results are shown in Table 2.

From Table 2, it can be seen that the cleaning solution containing no surfactant has an unstable cleaning effect and cannot be controlled, whereas the cleaning solution of the present invention has a slight difference in cleaning effect depending on the type of the surfactant. However, it was confirmed that the cleaning effect was stable when any of the surfactants was used. Also,
It was also confirmed that the cleaning liquid containing the surfactant having a perfluoroalkyl group in the molecule has a particularly high cleaning effect and is stable. This result shows that the present invention has high reliability with no variation in the obtained cleaning result.

[0026]

[Table 2] Example 3 In the cleaning liquid of the present invention in which the composition of the acid components is HNO ₃ 55%, HF 0.1%, and HCl 0.1%, several cleaning liquids having different surfactant (perfluoroalkyl quaternary ammonium salt) concentrations were prepared. Then, the etching rate was determined for each cleaning solution. The washed silicon wafer was a p-type semiconductor silicon wafer [electrical resistivity: several Ωcm, crystal orientation: (100)]. Washing was performed at 25 ° C for 1 minute. The results are shown in Fig. 1.

According to FIG. 1, in order to prepare a cleaning solution having an etching rate of about 20 to 30 Å / min, which is suitable for cleaning silicon wafers, the concentration of the surfactant in the cleaning solution should be 0.1.
It was shown that the addition should be made within the range of 002% to 0.05%. Example 4 In the cleaning liquid of the present invention containing 0.02% of perfluoroalkyl betaine, the cleaning effect on ¹⁹⁸ Au contamination when the concentration of the acid component was changed was examined. The results are shown in Table 3. The residual rate of ¹⁹⁸ Au in Table 3 is ¹⁹⁸ A on the p-type semiconductor silicon wafer [electrical resistivity: several Ωcm, crystal orientation: (100)].
This is the case where u contamination (10 ¹² atoms / cm ² ) was cleaned with each cleaning solution at 25 ° C for 40 seconds.

[0028]

[Table 3]From Table 3, HNO₃The higher the concentration¹⁹⁸High cleaning effect of Au
And HNO₃If the concentration of HF or HCl is low,
It turns out that sufficient cleaning effect can be obtained by increasing the concentration.
ItExample 5 When the cleaning liquid of the present invention is washed at a temperature of 10 ° C or lower
N-type semiconductor silicon wafer [electrical resistivity: several Ω
cm, crystal orientation: (100)] above 10¹²atoms / cm²of ¹⁹⁸Au dirt
The cleaning effect on dyeing was examined. The results are shown in Table 4. Messenger
The surfactant used was a perfluoroalkyl quaternary ammonia.
It is a nium-nium salt. The washing was performed for 40 seconds.

[0029]

[Table 4]From Table 4, washing just by slightly increasing the concentration of HF and HCl
Even if the temperature of the cleaning solution is lowered to 10 ° C or less, the cleaning solution has sufficient cleaning power.
Understand to give. Moreover, a cleaning experiment is performed at 5 ° C.
HNO in the clean booth₃Concentration is in contact with Cree
It was 1 ppb or less, which was almost the same as the concentration of the room. This
If the same cleaning is performed at 25 ° C, clean
HNO in the booth₃Concentration reaches 18 ppb and needs sufficient exhaust
And Example 6 In preparing the cleaning solution of the present invention, other raw material solutions for nitric acid
N-type semiconductor silicon wafer when the order of addition is changed
Above [electrical resistivity: several Ωcm, crystal orientation: (100)]¹⁹⁸Au dirt
Dyeing (10¹²atoms / cm²) To the cleaning effect of the cleaning liquid
I investigated the effect of The composition of the cleaning solution is HNO₃55%, HF 0.1
%, HCl 0.1%, surfactant 0.02%. Surfactant
Is a perfluoroalkyl quaternary ammonium salt.
Washing was performed at 20 ° C. for 1 minute. The results are shown in Table 5. With *
The cleaning liquids Nos. 601 and 602 are examples of the present invention, and
Is a comparative example.

[0030]

[Table 5] In addition to these, the following additions were made after sufficient stirring after addition. It can be seen that the cleaning effect decreases when the addition of the surfactant precedes the hydrofluoric acid and the hydrochloric acid. Example 7 Solution A and solution B shown in Table 6 were separately prepared and mixed at the time of use to prepare the cleaning solution of the present invention, and the cleaning effect of the cleaning solution was examined. n-type semiconductor silicon wafer [electrical resistivity:
Several Ωcm, crystal orientation: (100)] on ¹⁹⁸ Au contamination (10 ¹² atom
The cleaning effect and etching amount of the cleaning solution with respect to s / cm ² ) were examined. Washing was performed at 20 ° C. for 1 minute. The results are shown in Table 6. The surfactant used is perfluoroalkyl No. 4
It is a high grade ammonium salt.

[0031]

[Table 6] Although the composition of the cleaning liquid is the same as that of the previous example and the cleaning conditions are not changed, the cleaning effect of this two-liquid mixing method is not different from the best one in the case of sequential addition, and the etching amount is well controlled. Example 8 After a process such as reactive ion etching or ion implantation, a crystal defect occurs on the surface of a silicon wafer, and therefore surface etching of several tens of liters or more may be necessary to remove the defect. The decrease in the flatness of the surface of the silicon wafer during such etching is often caused by the fact that the etching rate of the cleaning liquid varies depending on the crystal orientation. Therefore, n-type semiconductor silicon wafer [electrical resistivity: several Ωcm, crystal orientation: (100)] (hereinafter referred to as (100)) and n-type semiconductor silicon wafer [electrical resistivity: several Ωcm, crystal orientation: (111)] (Hereafter, (111)
Two different types of silicon wafers having different crystal orientations are used as cleaning solutions (HNO ₃ 55%, HF 0.1%, HCl 0.1%) of the present invention.
%, Perfluoroalkyldimethylhydroxyethyl quaternary ammonium salt 0.02%), and the etching amount of the silicon wafer surface after cleaning was compared. Wash 25
It was carried out at 0 ° C for 10 minutes.

The etching amounts of (100) and (111) are both 1
There was a difference between 20Å and 180Å, and there was no significant difference between the two. From this example, it was confirmed that the etching action of the cleaning liquid of the present invention was not affected by the crystal orientation of the silicon wafer. Example 9 The amount of ¹⁹⁸ Au adsorbed from the cleaning liquid of the present invention on the surface of a silicon wafer was determined by changing the concentration of ¹⁹⁸ Au in the cleaning liquid. The results are shown in Figure 2.

From FIG. 2, it can be understood that even if a high concentration of gold is present in the cleaning liquid of the present invention, the amount of gold re-adsorbed on the silicon wafer in the cleaning liquid is extremely small. Example 10 A 6-inch silicon wafer in which ¹⁹⁸ Au was contaminated with 10 ¹² to 10 ¹³ atoms / cm ² on only one side was set in an experimental apparatus having a structure similar to that of a photoresist spin coater with its side facing upward, and HNO ₃ About 5 cc of a cleaning solution containing 55%, HF 0.2%, HCl 0.2% and polyoxyethylene alkylnonyl ether 0.02% was dropped while rotating the silicon wafer, spread on the entire surface of the silicon wafer, and the rotation was stopped to Let stand for a minute. Then rotate the silicon wafer again,
Pour pure water, rinse for 30 seconds, and dry by high speed rotation,
The residual rate of ¹⁹⁸ Au on the surface of the silicon wafer was determined. The 6-inch silicon wafer contaminated with ⁶⁴ Cu or ⁵⁹ Fe was also washed in the same manner, and the residual ratio of ⁶⁴ Cu or ⁵⁹ Fe was obtained. As a result, the residual rate of ¹⁹⁸ Au was 0.6%, which was ⁶⁴ Cu.
The residual rate was 0.2% and the ⁵⁹ Fe residual rate was 0.1% or less.

Even when the above-mentioned drying was carried out by spraying clean nitrogen, good removal results were obtained in the same manner as above for each contamination of ¹⁹⁸ Au, ⁶⁴ Cu or ⁵⁹ Fe. Example 11 As in Example 9, a silicon wafer contaminated with ¹⁹⁸ Au, ⁶⁴ Cu or ⁵⁹ Fe was held almost vertically, and the same cleaning solution as in Example 9 was sprayed onto the surface of the silicon wafer from above. After confirming that the entire surface of the silicon wafer was wet with the cleaning liquid, it was left for 1 minute, rinsed with pure water, and sprayed with high-purity air that had been microfiltered to dry it. When the heavy metal residual rate on the surface of the silicon wafer was determined, the residual rate of ¹⁹⁸ Au was
The residual rate of ⁶⁴ Cu was 0.2% and the residual rate of ⁵⁹ Fe was 0.1% or less.

[0035]

EFFECTS OF THE INVENTION The silicon wafer cleaning liquid and cleaning method of the present invention are applied to the surface of a silicon wafer of several tens of liters, particularly 20
The etching amount can be controlled with an etching amount of about 30Å, and the flatness of the surface is not impaired. Moreover, pollution of gold and other heavy metals can be reduced to 1/100 or less. Heavy metal contamination level in controlled VLSI manufacturing process is 10 ¹² atom
Since it is about s / cm ² , this cleaning can reduce it to 10 ¹⁰ atoms / cm ² or less.

The etching rate and etching amount of the silicon wafer cleaning liquid of the present invention can be adjusted by adjusting its composition. For example, by adjusting the etching rate to 20 to 30Å / min and adjusting the cleaning time, it is possible to obtain the above-mentioned etching amount of about 10 to 20Å in one cleaning, and to perform two repeated cleanings. Even so, substantially flatness can be obtained in VLSI manufacturing.

Further, the silicon wafer cleaning liquid of the present invention can be used even at a temperature of 10 ° C. or lower, depending on the composition selected, without reducing the cleaning effect. Therefore, even when acid contamination in the clean room working environment is a problem, acid scattering from the cleaning liquid can be substantially prevented by using the cleaning liquid at a temperature of 10 ° C. or lower.

Further, since the silicon wafer cleaning liquid of the present invention has a very high wettability with respect to a silicon wafer, the surface of the cleaning liquid can be kept wet until the pure water is rinsed, and the fine particles in the cleaning liquid are silicon wafers. It rarely adheres to the surface and is advantageous in terms of measures against particulate contamination.

In addition, since the silicon wafer cleaning liquid of the present invention hardly causes reverse contamination of the wafer due to the metal components in the cleaning liquid, a simple contact treatment of forming a thin layer of the cleaning liquid on the surface of the silicon wafer is sufficient for a sufficient cleaning effect. Can be raised. Therefore, the cleaning liquid can be used in a single-wafer cleaning device.

[Brief description of drawings]

1 is an etching rate of the cleaning solution of the present invention for a p-type silicon wafer [crystal orientation: (100), electrical resistivity: several Ωcm] obtained in Example 3 and a fluorine-based surfactant contained in the cleaning solution. 3 is a graph showing the relationship with the concentration of.

FIG. 2 is a graph showing the relationship between the concentration of ¹⁹⁸ Au in a cleaning liquid and the amount of ¹⁹⁸ Au adsorbed from the cleaning liquid on the surface of a silicon wafer, obtained in Example 9.

Claims (7)

[Claims] 1. A silicon wafer cleaning solution comprising 35 to 65% by weight of HNO ₃ , 0.05 to 0.5% by weight of HF, 0.05 to 0.5% by weight of HCl and 0.002 to 0.1% by weight of a surfactant. 2. The silicon wafer cleaning liquid according to claim 1, wherein the surfactant is a compound having a perfluoroalkyl group in the molecule. 3. A two-liquid type comprising concentrated hydrochloric acid and a liquid prepared by mixing hydrochloric acid, hydrofluoric acid and a surfactant in pure water, and mixed and prepared before use. The silicon wafer cleaning liquid according to 1 or 2. 4. A liquid obtained by mixing concentrated nitric acid and hydrofluoric acid,
The silicon wafer cleaning liquid according to claim 1 or 2, which is provided in a two-liquid type of a liquid containing hydrochloric acid and a surfactant, and is mixed and prepared before use. 5. A method of cleaning a silicon wafer, which comprises contacting a silicon wafer with the silicon wafer cleaning liquid according to claim 1 or 2. 6. The method for cleaning a silicon wafer according to claim 5, wherein the silicon wafer cleaning liquid is brought into contact with the silicon wafer at a temperature of 10 ° C. or lower. 7. The method for cleaning a silicon wafer according to claim 5, wherein the silicon wafer is brought into contact with the cleaning liquid by covering the surface of the silicon wafer with the liquid layer of the silicon wafer cleaning liquid.