JPH06216098A - Cleaning method for silicon wafer - Google Patents

Abstract

PURPOSE:To provide a wafer having a clean spontaneous oxide film by adding chelating agent in which complexan or carboxylate ligand of a value of a specific range is substituted for other acid group to cleanser to clean the wafer, and then rinsing it with water added with fluoric acid of a specific value or more. CONSTITUTION:A silicon wafer contaminated by forming 10<12>atoms/cm<2> of <59>Fe to iron hydroxide colloid is cleaned by using chelating agent as SC-1 liquid containing NH4OH:H2O2:H2O=1vol.:1vol.:5vol. at 70 deg.C for 10min. That is, the agent in which complexan or its carboxylate group ligand of 0.1 to 100ppm is replaced with other acid group is added to cleanser containing alkali.hydrogen peroxide.water. The wafer is cleaned. Then, it is rinsed by using water added with fluoric acid of 1ppm or more. Thus, the wafer having a clean spontaneous oxide film can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor silicon wafer manufacturing process and a method for cleaning a silicon wafer surface in a semiconductor device manufacturing process.

[0002]

2. Description of the Related Art Particle contamination and chemical contamination are the targets for cleaning semiconductor silicon wafers. A widely used cleaning method for these is called the RCA method, which is three kinds of cleaning solutions, that is, a cleaning solution containing ammonium hydroxide, hydrogen peroxide and water (SC-1), and a cleaning solution containing diluted hydrofluoric acid. (DHF), a cleaning solution (SC-2) containing hydrochloric acid, hydrogen peroxide and water is used for cleaning.

When the cleaning method was first introduced, the idea of the cleaning action was only for chemical pollution.
That is, SC-1 is used to remove metal and organic contamination forming an ammine complex ion, and the natural oxide film formed at this time is subjected to the following DHF (usually HF: H ₂ O = 1 volume: 50 to 200 volume).
The impurities that have been captured by this film are removed at the same time by dissolving and removing with SC-2, and the metal that remains until the end is removed with SC-2, which has a strong action of dissolving heavy metals. In this cleaning method, it is said that a clean natural oxide film is finally formed, and since this film is formed, the wafer after cleaning is hydrophilic.

Thereafter, it was recognized that SC-1 has an excellent effect of removing fine particles as compared with other cleaning liquids, and now the RCA method has been widely adopted particularly in the field of LSI. The standard SC-1 composition is ammonia water (28% by weight): hydrogen peroxide solution (30 to 35% by weight):
Water = 1 volume: 1 volume: 5 volumes, and the treatment using this washing solution is generally at 70 to 80 ° C for about 10 minutes. Since this treatment is accompanied by a slight etching action on the silicon surface and may cause fine pits on the silicon surface, means such as increasing the dilution of water or decreasing the concentration of ammonia have been appropriately tried. .

In the above-mentioned cleaning by the RCA method, a sufficient rinse with pure water is required to remove the cleaning liquid adsorbed on the wafer surface and the wafer carrier after the processing with each cleaning liquid and send it to the next processing. That is, this cleaning method requires at least three cleaning processes and three pure water rinsing processes. Therefore, from the viewpoint of productivity, as a cleaning device in a mass production plant, a structure is adopted in which a carrier carrying a large number of wafers is continuously transported and sequentially immersed in a multi-tank (in this case, 6 or more) processing tank. ing.

[0006]

By the way, in the process of removing the natural oxide film by dilute hydrofluoric acid (DHF) after the cleaning by SC-1, contrary to the effect of removing particles by SC-1, the back surface of the wafer is reversed. Or, the concentration of fine particles on the wafer surface usually increases due to fine particles or the like separated from the periphery of the carrier or the wall of the carrier. Moreover, the effect of removing fine particles is weak in the SC-2 cleaning which is performed subsequent to the cleaning with DHF, and it is difficult to sufficiently remove the adhered fine particles. Therefore, at present, the pattern miniaturization of LSI has progressed, and the importance of removing fine particles has increased rapidly.
By changing the order of the CA method, cleaning has been attempted in the order of DHF → SC-1 → SC-2.

However, in the above cleaning sequence, SC
Unless the order of the chemicals used for -1 is extremely high,
There is a problem that sufficient cleanliness cannot be obtained even after the final SC-2 cleaning. That is, in SC-1 cleaning, Fe, Al, etc. in the cleaning liquid are very likely to be adsorbed on the wafer and are taken into the natural oxide film grown during cleaning. However,
Subsequent SC-2 cleaning has no etching effect on the silicon surface, leaving a considerable amount of these metals as impurities. For this reason, the concentration of Fe and Al in the SC-1 cleaning solution is about 0.01 ppb with high purity only by trying to suppress the adsorption amount of Fe and Al after SC-1 cleaning to 10 ¹⁰ atoms / cm ² or less. Must be controlled.

[0008] Therefore, not only expensive chemicals of ultra-high purity are required, but also the cleanliness of the cleaning liquid or the chemical liquid supply system must be controlled particularly strictly, but Fe and Al are the impurities most easily contaminated in the clean room. Because of this, this management is not easy. Further, since the wafers are continuously loaded into the cleaning tank, Fe and Al carried by the wafers are accumulated in the cleaning liquid in the tank. Therefore, in order to ensure high cleanliness, the cleaning liquid may have to be replaced every time, which increases not only the direct material cost but also the burden of waste liquid treatment.

Therefore, in practice, the cleaning process is performed by SC-1 → SC.
In the order of −2 → DHF, ultrasonic waves of about 1 MHz are applied at the time of rinsing to remove fine particles generated in the final DHF. That is, SC-1
The heavy metal taken into the native oxide film by S is as described above.
C-2 is not effectively cleaned, and the removal of the natural oxide film by DHF is effectively carried out together with the cleaning power of hydrofluoric acid.

However, it is extremely difficult to satisfactorily remove fine particles by the above method. Further, no matter which of the above-mentioned methods is adopted, when the surface of the wafer after cleaning is analyzed, contaminant metals of 10 ¹⁰ atoms / cm ² or more are often detected. At present, metal contamination of about 10 ¹² atoms / cm ² may be observed even in a well-controlled and clean semiconductor manufacturing line. Since ultra-high integration devices require cleaning up to the order of 10 ⁸ atoms / cm ² , cleaning systems are desired to reduce the surface contamination metal level by three orders of magnitude or more. In the RCA cleaning method, even if the chemical solution itself has sufficient cleaning power, strict control is required in terms of the quality of chemicals used, pure water, maintenance of the cleaning device, and the like.

Also, as the diameter of the wafers used for production increases, the size of the cleaning equipment also increases, and the length of the cleaning equipment having a 6-tank structure of 8 "wafers is 10 m including the loader section, the drying section and the unloader section. On the other hand, with the sophistication of devices, the required new manufacturing equipment will increase rapidly and the clean room area will inevitably increase accordingly. It is not preferable in terms of economy or maintenance for maintaining cleanliness inside the device.

Further advanced devices also require a dry process of removing the natural oxide film with hydrogen fluoride gas immediately before the wafer is put into the process chamber of the manufacturing apparatus. This process cannot remove contaminants such as fine particles and metallic elements, so that it is necessary to prepare a wafer having a clean native oxide film that has been sufficiently washed to a level below the required level for the deposition of these harmful substances.

Therefore, it is an object of the present invention that a large number of cleaning tanks are not required, and silicon wafers can be cleaned with a small number of cleaning tanks, and DHF → SC.
-1 → SC-2 in order of fine particle removal capacity comparable to RCA cleaning method, and SC-1 → DHF → SC-2 in order of R
It is an object of the present invention to provide a method for cleaning a silicon wafer, which has a chemical contamination removing ability comparable to that of the CA cleaning method and can be a wafer having a clean natural oxide film.

[0015]

According to the present invention, a cleaning solution consisting of alkali, hydrogen peroxide and water can be used in an amount of 0.1 to 100 p
The silicon wafer is washed by adding a chelating agent in which the pm complexan or its carboxylic acid group ligand is replaced with another acid group, and then rinsing with water containing 1 ppm or more of hydrofluoric acid. A method for cleaning a semiconductor silicon wafer is provided, which is characterized by being performed.

[0016]

In the present invention, SC-2, which is the main force for removing metal elements in RCA cleaning, is omitted, and instead, a chelating agent such as complexan is added to SC-1 to enhance the metal contamination cleaning power. , SC-1 → SC-2, or a cleaning effect equivalent to or higher than SC-2 was successfully achieved. In addition, DH that produces a hydrophobic surface that is easily contaminated with fine particles
F cleaning is not carried out, but instead, after the SC-1 cleaning, rinsing is carried out using water to which a slight amount of hydrofluoric acid has been added, whereby residual contaminant metals and adsorption additives unevenly distributed in the surface layer of the natural oxide film are absorbed. And the hydrophilic surface where the fine particles are easily released is maintained and the fine particle removing effect is enhanced.

Na or Fe labeled with a radioisotope
For a wafer contaminated with 10 ¹² atoms / cm ² of the amount, the residual amount of the metal after RCA cleaning is calculated from the radioactivity count value, and no matter which order method is used, 1
Since it is about 0 ⁸ atoms / cm ² , a very good cleaning effect can be confirmed. However, in the surface analysis of the RCA cleaned wafer in the actual production line, both Na and Fe show 10 ¹⁰ atom.
Contamination of s / cm ² or more may be seen. In such a case, these are detected even by an environmental pollution test in the equipment in which a clean wafer is left in the cleaning equipment for a predetermined time and surface analysis is performed, and it is left when the use of the SC-2 cleaning tank in the cleaning equipment is stopped. The cleanliness of the test wafer is improved. SC-2
When cleaning is performed, the higher the degree of cleaning, the more severe the structural and management requirements of the cleaning device.
In the present invention, SC-2 wash omission is one feature.

In the method of the present invention, first, a chelating agent is added to SC-1, and cleaning is performed using a cleaning liquid having an enhanced cleaning power for metal contamination. As this chelating agent, a chelating agent in which complexan or its carboxylic acid group ligand is substituted with another acid group is used. SC-1
Although it is easily conceivable to add a complexing agent to Fe to improve the cleaning effect on Fe and Al, all effective complexing agents are organic substances. That is, when this organic substance adheres to the wafer from the cleaning liquid, carbon adversely affects the device characteristics. Therefore, an extremely small amount of a high-performance complexing agent required by the TOC standard for high-purity inorganic chemicals for semiconductors is used. There must be. However, in the present invention, since the organic substances adsorbed on the natural oxide film are removed by the hydrofluoric acid-added pure water rinse performed after this cleaning, a relatively large amount of the chelating agent, for example, about 10 ppm, and in some cases 100 ppm. Does not leave a harmful level of organic contamination on the wafer after cleaning. Therefore, regarding the chelating agent necessary for the present invention,
High performance is necessary, but super high performance is not always necessary.
Among the metallic elements that tend to remain on the wafer after SC-1 cleaning, Fe is a particularly problematic one in terms of device characteristics. Therefore, in the present invention, the residual rate of Fe after cleaning is about 1% or less at a concentration of 10 ppm or less. And complex complex were used as chelating agents.

In the present invention, as the complexant used as the chelating agent, ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA), cyclohexanediaminetetraacetic acid (CyDTA), triethylenetetraminehexaacetic acid (TTHA), etc. Can be illustrated as
In addition, examples in which the carboxylic acid group ligand is substituted with another acid group include dihydroxyethylglycine (DHEG). Some of the substituted ligands containing P have a strong chelating effect according to the present invention, and examples thereof include alkylaminodimethylene diphosphonic acid, polymethylene bis (nitridimethylene) tetraphosphonic acid, and nitrilotrismethylene. Examples thereof include phosphonic acid (NTPO), and those obtained by substituting these phosphonic acids with phosphinic acid. These additives according to the present invention must be sufficiently purified in the liquid after addition to such a level that the metal impurities therein do not interfere with the cleaning. In addition, when the elements to be cleaned are various, it is possible to use two or more of these chelating agents in combination, if necessary. The amount of this chelating agent added is 0.1 to 100 ppm.
Is.

SC-to which the above chelating agent is added
As described above, 1 is composed of alkali, hydrogen peroxide and water. Examples of the alkali include ammonium hydroxide and organic alkalis having no metal component such as tetramethylammonium hydroxide and trimethyl (2-hydroxy) ethylammonium hydroxide. Its composition is generally 0 for alkali.
05 to 5% by weight, hydrogen peroxide is 0.05 to 10% by weight, and the balance is water.

The chelating agents used in the present invention are rarely stable for a long period of time in high-concentration hydrogen peroxide or alkali. Therefore, a chelating agent is added in advance to prepare a cleaning solution. If stored, the storage period should be as short as possible. Many of these chelating agents are usually sparingly soluble in water, but can be easily made into an aqueous solution by making them alkaline. Therefore, when a sparingly water-soluble chelating agent is used, this alkaline aqueous solution can be added to the preparation tank attached to the cleaning device to prepare the cleaning liquid having the above-mentioned composition. Further, particularly when treating a wafer with severe metal contamination, an aqueous solution of this chelating agent is added directly to the cleaning tank to enhance the cleaning effect and enhance the effect of suppressing adsorption contamination from the liquid on subsequent wafers. You can also

The cleaning solution prepared by adding the above-mentioned chelating agent to the SC-1 cleaning solution having the above composition generally has an addition amount of about 10 ppm, and in addition to Fe, Ni, Cr, Cu, Zn.
For example, the amount of harmful heavy metals adhering to the surface in the semiconductor process can be reduced by two digits or more. Particularly, those containing P in the complexan-substituted ligand have a further enhanced cleaning effect on these metals. For example, with respect to Fe, the addition amount is 10 pp.
It is possible to reduce by about 3 digits at m and 1 digit by 2 digits.
However, all of them are group III acceptors and are not sufficient for Al contamination, which is harmful to the control of the film growth process, and the reduction effect is almost one digit. It is understood that most of Al contaminating the natural oxide film is replaced with Si atoms, and this removal is performed by rinsing etching.

In the present invention, the cleaning liquid is supplied to the cleaning tank to clean the wafer, and then rinsed with pure water containing 1 ppm or more of hydrofluoric acid. A small amount of hydrofluoric acid has a strong effect on the natural oxide film of silicon when it enters the cleaning solution, but it does not show reactivity in an alkaline solution.
Therefore, even if a slight amount of hydrofluoric acid is added to the rinse pure water after the SC-1 cleaning, the SC- which has been charged into the rinse tank is used.
It can be said that there is almost no effect on the silicon surface wet with one liquid. From the stage where most of the SC-1 solution is removed by the flow of rinse water, the action characteristic of the present invention appears. That is, 1
Rinsing with pure water containing at least ppm hydrofluoric acid has a strong removing effect on the chelating agent adsorbed on the wafer surface in the previous cleaning. Further, as the pure water is heated, the removing action becomes stronger. On the other hand, in the process of treating with DHF during RCA treatment and then rinsing with pure water, it becomes difficult for the chelating agent to be transferred to the wafer surface and removed immediately after the DHF treatment.

The concentration of hydrofluoric acid in the rinse water is preferably as high as possible in terms of removing chemical contamination. However, if the concentration is too high, there is a problem that contamination from piping materials and the like necessitates a special rinse liquid supply mechanism. Therefore, the concentration of hydrofluoric acid is generally 1
It is preferably about 00 ppm or less. When the concentration is higher than this, it is necessary to stop the addition of hydrofluoric acid to pure water for a short time at the final stage of rinsing to remove the F atoms adsorbed on the wafer.

In the present invention, Al which cannot be removed sufficiently by the washing with the chelating agent-added SC-1 liquid which is carried out previously.
In order to remarkably enhance the cleaning effect of the above hydrofluoric acid-added pure water rinse on atoms, the pure water is heated (usually 40
It is desirable to perform rinsing at about 70 ° C.). For example, the surface Al concentration can be reduced to about 1/20 by rinsing for 10 minutes at a hydrofluoric acid concentration of 100 ppm and 50 ° C. This can be considered that Al is unevenly distributed in a thin layer near the surface of the natural oxide film formed on the wafer surface, and the layer is etched. From the experiment investigating the change of contact angle of water drop under long-term rinse under these conditions, it was estimated that the amount of etching under this rinse was several Å. Since the etching action in SC-1 proceeds along with the formation of a natural oxide film on the silicon surface, there is a high possibility that uncleaned impurities or impurities adsorbed from a liquid will be unevenly distributed on the surface layer of the natural oxide film. The effect of removing the surface chelating agent by the rinse in the present invention can be explained as a similar action.

With respect to the Fe remaining after the SC-1 cleaning, for example, when the rinsing water temperature is heated to about 50 ° C., the residual ratio is about 1 after 10 minutes of rinsing at a hydrofluoric acid concentration of about 10 ppm. %, The surface density is reduced by two digits. C
The cleaning effect of the warm hydrofluoric acid-added pure water rinse on r, Ni, and Zn is about the same as that of Fe. The cleaning effect on Cu is inferior to these, but the concentration of hydrofluoric acid is 100 ppm, 50
A 10-minute rinsing at a temperature of about 1 digit is possible.

In the cleaning for ultra-cleaning, even if the required cleanliness level is reached in the chemical treatment step, there is a risk of contaminating it in the ultra-pure water rinsing step. Since there are elements that are easily adsorbed from the water to the silicon surface, if we try to keep their concentration on the cleaned surface at a level of 10 ⁸ atoms / cm ² ,
Extremely strict purity control is required for ultrapure water for rinsing. Impurities that are easily adsorbed from water are Fe, Al, Cu, etc., and the longer the rinsing time and the higher the pH, the easier the adsorption becomes. Although a quick dump method or the like is used to improve the rinse efficiency, the rinse time is usually 10 minutes. Especially in the rinsing tank after SC-1 cleaning, the pH first rises, so Fe, Al, etc. can be absorbed in ultrapure water.
Rinse 10 minutes at 10 ⁹ at even a very small amount of ppt
Possibly causing oms / cm ² level contamination. But 1p
In the case of hydrofluoric acid-added pure water rinse of pm or more, even if Fe, Al, etc. are present in the rinse water in the order of several tens of ppt, the contamination from these can be stopped at the level of 10 ⁸ atoms / cm ² .

As is well known, when the surface of an oxide film is etched with dilute hydrofluoric acid, the surface is strongly hydrophilized and a strong departing action is observed while the film remains. To be Also in the hydrofluoric acid-added pure water rinse of the present invention, as long as there is a natural oxide film on the silicon surface, a sufficient departing effect is recognized, and the hydrophilicity of the wafer surface after cleaning is strong. The SC-1 cleaning in which the chelating agent is added in the present invention has no difference in the effect of removing fine particles from the conventional SC-1 cleaning. Therefore, in the method of the present invention, SC-
Even if only two cleaning tanks, one cleaning tank and one rinsing tank, are treated with the synergistic effect, D has the largest particle removal effect in the RCA method.
The particle removal effect is superior to that of the 6-tank treatment of HF → SC-1 → SC-2.

In the present invention, when importance is attached to the removal of metal contamination, the purpose is to add dilute hydrofluoric acid directly to the rinse tank only once so that the DHF treatment is performed once during the quick dump rinse. Can be achieved. At that time, the wafer surface becomes hydrophobic and inferior in terms of removing fine particles, but on the other hand, there is also an advantage that a natural oxide film is less likely to be generated by the rinse after this, and the present invention finally requires a surface without a natural oxide film. It can also be used for easy cleaning.

[0030]

EXAMPLES The present invention will now be described with reference to examples, but of course the present invention is not limited thereto. The present invention aims at ultra-cleaning of a wafer by cleaning, and since the target cleanliness is on the order of 10 ⁸ atoms / cm ² ,
It is difficult to confirm the effect by surface analysis. Therefore, some of the following examples used the RI tracer method in which the cleaning effect on a test wafer contaminated with an element labeled with a radioisotope (RI) was compared by comparing the radioactivity counts before and after cleaning. ⁵⁹ Fe in the following examples are intended to mean Fe labeled with ⁵⁹ Fe.

Example 1 For a silicon wafer in which 10 ¹² atoms / cm ² of ⁵⁹ Fe was contaminated as iron hydroxide colloid, NH ₄ OH: H ₂ O was used.
_2: H ₂ O = 1 volume: 1 volume: the SC-1 solution of 5 volumes of residual rate of ⁵⁹ Fe after cleaning when performing the cleaning of 70 ° C. × 10 minutes using a chelating agent of the present invention It shows in Table 1. Where C (P1)
Is an abbreviation for alkylaminodimethylene diphosphonic acid having a low molecular weight. By the way, it was 6.5% when the chelating agent was not added. 10 ppm for both chelating agents
Addition of ~ 100ppm increases the surface concentration level of ⁵⁹ Fe from 2 digits to 3
The digit can be lowered. Further, those containing P in the ligand had a great cleaning effect, and with C (P1), a reduction of almost two orders of magnitude was obtained even at 0.1 ppm.

[0032]

[Table 2]

Example 2 The composition of the SC-1 solution was NH ₄ OH: H ₂ O ₂ : H ₂ O =
Table 2 shows the results of washing in the same manner as in Example 1 with 1 volume: 1 volume: 12.5 volume and 1 volume: 1 volume: 25 volume.
Even if the SC-1 solution is diluted to 2 times or 3 times the standard composition, the effect of the chelating agent used in the present invention does not change. Here, C (P2) is an abbreviation for a low molecular weight polymethylenebis (nitridimethylene) tetraphosphonic acid.

[0034]

[Table 2]

Example 3 ⁶⁴ Cu was precipitated from dilute hydrofluoric acid to obtain ²² Na, ⁵¹ Cr and ⁵⁷ N.
i is a chloride, and about 10 ¹² atoms / cm ^{2 of} each is attached to a silicon wafer, NH ₄ OH: H ₂ O ₂ : H ₂ O = 1 volume: 1 volume: 12.5 volume SC-1 liquid 10% of the chelating agent of the present invention, TTHA, is added to Table 3, and the residual rate after washing at 70 ° C. for 10 minutes is shown in Table 3. Na does not chelate, but SC
-1 itself has detergency, and chelating agents do not otherwise interfere with this.

[0036]

[Table 3]

Example 4 A minute amount of aluminum chloride was dissolved in SC-1 solution containing no chelating agent, and six silicon wafers were simultaneously immersed. The amount of Al adhering to the three wafers was vapor-phase decomposed with hydrofluoric acid. An average of 9x when analyzed by flameless atomic absorption spectrometry
It was 10 ¹¹ atoms / cm ² . NTP for the remaining 3 sheets
When SC-1 added with 10 ppm of O was washed at 70 ° C. for 10 minutes and the same analysis was conducted, it was 1.04 × 1 on average.
It was 0 ¹¹ atoms / cm ² . The cleaning effect of the chelating agent-added SC-1 used in the present invention is rather bad against Al contamination, and in this example, about 10% remains after cleaning.

Example 5 Rinse on how much the chelating agent of the present invention adsorbed by SC-1 washing can be removed by rinsing the subsequent hydrofluoric acid-added water R
It was examined by the I tracer method. Chelating agents NTPO is the same the number of the number of P atoms C atoms, and so can be relatively easily synthesized from ammonium chloride, formaldehyde and phosphorous acid, choose the subject of this study, by neutron irradiation ³²
NPO labeled with P was synthesized. I chose ³² P without using ¹⁴ C because the latter gives much higher non-radioactive activity and also has much stronger energy for β rays. A silicon wafer was treated with SC-1 containing 100 ppm of NTPO at 70 ° C. for 10 minutes, rinsed with pure water several times and naturally dried, and the adsorption amount of ³² P, that is, C was found to be about 5 × 10 ¹⁵ atoms. Adsorption to the wafer of / cm ² was observed. When this was rinsed with HF 10 ppm and pure water at 50 ° C., the detection limit was 5 × 10 ¹³ atoms / cm ² or less. Wafers washed with SC-1 containing 10 ppm of NTPO have P even if rinsed with pure water at room temperature containing 1 ppm of HF.
That is, the adsorption of C was below the detection limit. The HF-added pure water of the present invention can reduce the chelating agent adsorbed on the wafer to a level without causing any actual damage.

Example 6 Under the same conditions as in Example 4, a SC-1 solution added with a trace amount of aluminum chloride was used to obtain a surface Al concentration of 1 to 2 × 10 ¹¹ at.
A test wafer of oms / cm ² was prepared, and the Al cleaning effect by the HF-added pure water rinse was examined. The results are shown in Table 4. still,
The analysis method is the same as in Example 4. For Al, it was confirmed that increasing the amount of HF added to the rinse pure water and heating were effective.

[0040]

[Table 4]

Example 7 70 using SC-1 with the addition of the chelating agent TTHA
The wafer that has been washed at ℃ × 10 minutes, rinsed by heating pure water containing 100 ppm HF to 50 ℃,
Table 5 shows changes in the contact angle of water droplets with respect to the rinse time. H
It is estimated that the pure water rinse of F100ppm, 50 ° C probably removed a few Å of the natural oxide film surface even by the rinse time of 10 minutes.

[0042]

[Table 5]

Example 8 1 to 3 × 10 ¹⁰ after being treated with SC-1 solution containing ⁵⁹ Fe
For a wafer with atoms / cm ² of ⁵⁹ Fe remaining,
⁵⁹ when pure water containing HF was heated and rinsed for 10 minutes
Table 6 shows the residual ratio of Fe. Decrease pollution level by 2 digits, 1
Is observed can be reduced to a level of 0 ⁸ atoms / cm ^2.

[0044]

[Table 6]

Example 9 With respect to ⁶⁴ Cu, the cleaning effect of the HF-added pure water rinse heated in the same manner as in Example 8 was examined. The results are shown in Table 7. Cu
For, the cleaning effect of the HF-added pure water rinse is weak. Therefore, it is necessary to use a chelating agent having a strong cleaning effect on Cu as the chelating agent added to SC-1, but in general, many complexants have a chelating effect on Cu.

[0046]

[Table 7]

Example 10 In order to evaluate the effect of removing fine particles in a pure water rinse containing hydrofluoric acid, an RI tracer method was performed using dust labeled with a radioactive element. That is, the indoor dust adsorbed with ⁹⁹ Tc-labeled carbon fine particles was transferred to a DHF-treated hydrophobic silicon wafer surface and a hydrophilic silicon surface treated with the EDTA-added SC-1 solution, respectively, to obtain radioactivity count values (5,000- 10,0
(00) cpm was applied. When these were rinsed with pure water for 10 minutes, the count value of the former decreased by about 30% and that of the latter decreased by about 35%. HF 10 ppm added pure water rinse was heated to 50 ° C. on these wafers that had been similarly deposited, and
After rinsing for 0 minutes, the former count value was halved, while the remaining count value on the hydrophilic silicon surface was several tens cpm, and 99% or more of the adhered dust could be removed. SC-
In the rinse of the present invention after 1 treatment, since it is a rinse on the hydrophilic surface in which the natural oxide film is left in principle, it is expected that HF-added pure water can remove extremely fine particles.

Example 11 There were six quartz glass experimental tanks in the clean booth,
In the cleaning experiment equipment where the odd number is the chemical solution tank, the even number is the running water rinse tank capable of quick dump, and a sufficient exhaust mechanism is installed at the upper edge of the chemical solution tank, the chemicals have the highest commercially available analytical values. 18 MΩ for rinse water
Fluorine resin P is used for 5 "wafers that have been intentionally contaminated with chemicals and fine particles by being immersed in industrial chemicals using ultrapure water of cm.
A cleaning experiment was carried out by placing the carrier in FA carrier. First, a series of cleaning experiments by the RCA method was repeated for 1 week, and after 1 month, the cleaning method of the present invention was repeated for 1 week using the fifth tank and the sixth tank. For drying, use a spinner to extract one cleaned wafer from the carrier, perform gas phase decomposition with hydrofluoric acid, and analyze the surface by atomic absorption method. On other wafers, a laser scattering surface inspection device detects fine particles of 0.2 μm or more. I counted. The results are shown in Table 8. From this result, it is understood that the two-tank system cleaning method of the present invention is superior to any of the RCA systems for removing fine particles. Further, in the case of the RCA method, the wafer surface analysis result containing a slight amount of metal contamination, which is considered to be caused by SC-2 environmental pollution due to HCl, insufficient control of impurities in the SC-1 tank, etc., was obtained. The cleaning system provides more stable surface cleanliness.

[0049]

[Table 8]

SC-1 is 1 volume: 1 volume: 12.5 volume, SC
-2 was 1 volume: 1 volume: 5 volumes, and each was dipped at 70 ° C. for 10 minutes. DHF was immersed in 1 volume: 50 volumes for 30 seconds. The chelating agent was NTPO 3 ppm, and the HF-added pure water rinse was HF 10 ppm and heated water at 50 ° C.

Example 12 In accordance with the present invention, the first stage chelating agent added SC-1
It was confirmed by the yield of dielectric strength with a MOS diode (500 mμ □) that the cleanliness sufficient for device fabrication can be obtained only by cleaning with a liquid. The case of using the SC-1 solution of the additive-free high-purity chemical is compared by washing at 70 ° C. for 10 minutes. The results are shown in Fig. 1. The chelating agent used in the method of the present invention was 1 ppm of NTPO, and the rinse was performed with ultrapure water.

Example 13 In order to confirm the effect of the hydrofluoric acid-added pure water rinse of the present invention on the electrical characteristics, it was washed with the chelating agent-free SC-1 liquid of the above example and rinsed with ultrapure water. Wafer and this
The recombination lifetime was compared when rinsed with 100 ppm HF-added pure water at 50 ° C. for 10 minutes. The results are shown in Figure 2. From these results, it is understood that the cleaning effect of the warm HF-added water rinse is clear and a sufficient lifetime can be obtained.

Example 14 The cleaning effect of the present invention when the ammonia water of SC-1 having a standard composition was replaced with 1% by weight of tetramethylammonium (TMAH) was used. It was examined under the same washing and rinsing conditions.
The results are shown in Table 9. Good results, which are not different from the case where the chelating agent-added SC-1 is used, are obtained.

[0054]

[Table 9]

[0055]

According to the present invention, a cleaning system for RCA treatment which requires at least 6 cleaning tanks or rinsing tanks can be basically constructed with only 2 tanks. It is far more advantageous in terms of equipment price, equipment required area, and operating cost. Moreover, in the RCA cleaning, there is a contradiction between the chemical contamination removal and the particulate contamination removal, no matter how the chemical treatment order is changed. However, in the method of the present invention, the chemical contamination removal capability equivalent to that of the RCA treatment and Has the ability to remove fine particles that is superior to processing. Needless to say, the chelating agent required for the present invention is preferably as strong as the metal chelating action, but even if it is not a special substance having a particularly high action, for example, commercially available complex complex chelating agent is easily available. The purpose can be sufficiently achieved with a drug.

[Brief description of drawings]

FIG. 1 SC-1 with chelating agent added in the method of the present invention
The figure which shows the dielectric strength yield of a MOS diode before and after cleaning by a liquid.

[FIG. 2] Wafers washed with SC-1 liquid without chelating agent and rinsed with ultrapure water.
The figure which compares and shows the recombination lifetime at the time of rinsing with added pure water at 50 degreeC x 10 minute (s).

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hideo Akitani Hideo Akiya 1-14-5 Kichijojihonmachi, Musashino-shi, Tokyo Nihon Kogyo Bank Building 8F Inside NTT Electric Electronics Technology Co., Ltd. (72) Inventor Shuji Kuwano Tokyo Musashino City Kichijoji Honcho 1-14-5 Nihon Kogyo Bank Building 8F Entiti Electronicstronics Technology Co., Ltd. (72) Inventor Toru Matsumoto 1-14-5 Kichijoji Honcho, Musashino-shi Tokyo Metropolitan Bank Building 8F NTT Electronics Corp. Technologies Co., Ltd. (72) Inventor Hisashi Muraoka 3-15-2 Migaoka, Midori-ku, Yokohama-shi, Kanagawa

Claims (2)

[Claims] 1. A silicon wafer prepared by adding a chelating agent in which 0.1 to 100 ppm of complexan or its carboxylic acid group ligand is replaced with another acid group to a cleaning solution comprising alkali, hydrogen peroxide and water. Wash, then 1pp
A method for cleaning a semiconductor silicon wafer, which comprises rinsing with water to which hydrofluoric acid of m or more is added. 2. The cleaning method according to claim 1, wherein the rinsing is performed by heating the water containing the hydrofluoric acid.