JPH0393229A - Purification of semiconductor wafer - Google Patents

Abstract

PURPOSE:To improve cleaning efficiency by cleaning a semiconductor wafer with an aqueous solution of specific component after its treatment with a liquid whose main agent is a specific alkylether. CONSTITUTION:After organic substances deposited on a semiconductor silicon wafer are removed with a liquid whose main agent is either one of triethylene glycolmonoalkylether and tetraethylene glycolmonoalkylether, the wafer is cleaned with an aqueous solution containing an organic strong alkali and peroxide hydrogen. Cleaning wafers in this way removes organic substances and Cu readily.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention provides a chemically ultra-clean surface for semiconductor silicon wafers to which organic substances have adhered (in this specification, each harmful metal element is approximately 10 I0 The present invention relates to a surface treatment method in which organic adsorbed films other than natural oxide films and foreign structures such as clouds are not substantially observed.

[Prior art and problems to be solved by the invention] In wafer processing related to semiconductor device manufacturing, it is necessary to attach organic substances to the wafer, completely remove the organic substances, and at the same time ultra-clean the wafer. There is a process. One is the process of mirror polishing silicon wafers.

Since the projection exposure method was adopted for microfabrication of LSIs, strict flatness and parallelism have been required for mirror polishing of silicon. Then, using a trowel, attach the back side of the wafer to the mounting plate using wax with appropriate adhesive strength, while pouring an alkaline polishing liquid containing mainly silica particles onto the surface of the polishing cloth adhered to the surface plate. , the polishing surface of the wafer on the mount plate is pressed against it, and both parts are rotated independently to perform precise polishing. After polishing, the wafer is peeled off from the mounting plate, and the wax attached to the back side is usually paraffin-based and dissolves well only in chlorinated hydrocarbon solvents, so trichlorethylene is generally used as a removal agent and it is treated with ultrasonic waves at a temperature close to its boiling point. Steam cleaning etc. are being carried out. This type of solvent is chemically unstable and generates fine particles that contaminate the wafer surface, and the remaining polishing agent cannot be completely removed. It is widely practiced to subsequently perform wafer cleaning with a processing solution (abbreviated as -1). However, this cleaning solution contains Cu. Zn
, Co. Although it has a cleaning effect on chemical contamination such as Ni due to its complexing action, it has a cleaning effect on chemical contamination such as Ni. It is known that cleaning power is weak against chemical contamination such as Aj2. Therefore, dilute hydrofluoric acid treatment, which has extremely strong cleaning power, is usually added to the cleaning process.

Now, impurities on the surface of wafers for memory devices from various silicon manufacturers currently on the market are treated with a trace amount of high-purity acid to concentrate them in a small area on the surface, and then analyzed by total internal reflection fluorescence X-ray analysis. Or SIMS analysis, etc., detects Na+K, Ca. F
e. ^l. Cu, Cr, Zn, etc. are detected. In particular, the elements with high contamination levels that are common to each company's Way8 are AN.
Approximately 1011 atoms/cd or more have been detected for Cu and Cu. This ^l could be reduced to 1010 atoms/c+i or less by a combination of hydrofluoric acid treatment and acid treatment described below, but for Cu of about 1 to 5) XIO'' atoms/cd that was not detected here, Cu removal SC-1 or hydrochloric acid + hydrogen peroxide + water (referred to as SC-2 of the RCA method), which is effective in
It was difficult to reliably reduce the amount to a certain extent. C above
For elements other than u, we were able to reduce them to 101o atoms/cd or less by additionally washing them with one of the treatment solutions shown here. However, in the semiconductor device manufacturing process, Cu has a high diffusion rate in silicon and is susceptible to crystal defects. Because it is easy to remove, it reduces the lifetime of minority carriers in key parts of the device structure, deteriorates the withstand voltage of the insulating film, and lowers the charge retention characteristics. That is, it is a typical impurity that adversely affects device performance and yield. The next generation target for the surface impurity concentration of cleaned wafers, that is, 4 to 16 megabits in the DRAM era, is thought to be 10I0 atoms/d or less, but it is difficult to achieve this for Cu using conventional cleaning methods in the silicon mirror polishing process.

Another major process that requires complete removal of organic matter and ultra-cleaning of the silicon surface is resist removal after etching in photolithography. Generally, Ox plasma ashing is widely used, but the resist usually contains
Cu of oppb level. Since metal impurities such as Fe are included, they remain on the wafer surface as the resist ashes, and the amount of contamination reaches IQII atoms/d. From the viewpoint of removing such contamination and preventing element damage caused by plasma, wet processing is preferable for resist removal.

Hydrogen peroxide or sulfuric acid to which ozone is added is generally used for wet treatment, but heat treatment at about 120 to 130°C is required.

By the way, since the chlorinated hydrocarbons such as trichlorethylene used in mirror polishing are processed at temperatures close to their boiling point, a considerable portion of the amount used evaporates and contaminates the atmosphere of the processing chamber. Contaminates and forms an organic adsorption film. Furthermore, following this process (in SC-1 cleaning, a large amount of ammonia gas evaporates and contaminates the processing chamber atmosphere, which also causes secondary contamination and reactions on the cleaned wafer surface, resulting in a foreign surface condition such as cloudiness). occurs.

In addition, since the sulfuric acid-based wet process for resist removal requires a temperature of about 130°C, sulfuric acid fust is generated, contaminates the processing chamber environment, and, like ammonia, directly or indirectly affects the wafer. Organic solvent-based stripping agents have also been tried for removing positive type resists, but those with good removal ability contain organic alkalis such as monoethanolamine or diethanolamine, which have a considerable vapor pressure at the required processing temperature. Since it is expensive, it contaminates the processing chamber atmosphere and becomes a source of secondary contamination of organic films on wafers. Such a polluted atmosphere is discharged outside the factory through a duct and an exhaust gas treatment device, but it is not easy to completely remove the chemical substances listed here. Even a small amount of air pollution can cause trichlorethylene pollution, acid rain, etc., so exhaust gas treatment poses a large economic and management burden.

The purpose of the present invention is to remove organic matter adhering to the wafer by using a non-evaporating treatment liquid that does not become a source of contamination through the atmosphere and does not cause air pollution on the surface once cleaned. The present invention provides an ultra-cleaning method for silicon wafer surfaces that can remove metal impurities harmful to semiconductors to approximately 10I0 atoms/C for each element. [Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention removes organic substances attached to silicon wafers for semiconductors using a small amount selected from triethylene glycol monoalkyl ether and tetraethylene glycol monoalkyl ether. The present invention provides an ultra-cleaning method for wafers in which a cleaning treatment is performed using a solution containing one type of main ingredient, and then a cleaning treatment is performed using an aqueous solution containing a strong organic alkali and hydrogen peroxide.

We selected wax in mirror polishing and resist in photolithography as the organic substances to be removed, and after clarifying the behavior of Cu, which is the most difficult to clean, in each conventional process, we
The features of the action of the processing liquid that constitutes the present invention will be shown in comparison with the conventional one.

First, we investigated the behavior of Cu during mirror polishing. When the polishing liquid was collected from the polishing cloth during operation of the polishing machine with a cast iron surface plate and analyzed, the Cu concentration was found to be 10=15 ppb. After polishing, the wafers were peeled off from the mount plate and washed with water without removing the wax on the back side, and the surface analysis described above was performed, and 10 wafers were found to have (8 to 18) XIOII atoms/c.
Adsorption of Ti was detected. When boiling and steam cleaning with trichlorethylene to remove wax, the Cu concentration on the surface was reduced by about half, to (4 to 10) x 10'' atoms/C+a.

Subsequently, SC-1 cleaning consisting of aqueous ammonia (l volume), hydrogen peroxide (l volume) + water (5 volumes) was performed at 80°C for IO minutes, but (1.1-2)XIO'' atoms/aJ Further addition of dilute hydrofluoric acid treatment had no significant effect; the degree of cubing was only reduced by about 20% on average.

An unexpected result obtained in this series of experiments was the cleaning effect of sc-i on wafers treated with trichlorethylene, and although it is expected to have an excellent effect on Co, the residual rate of Cu after cleaning was very low. It was 15-25%. On the other hand, for comparison, Cu dissolved in dilute hydrofluoric acid was applied to the silicon surface for 10'! When SC-1 cleaning of the same type and under the same conditions was performed on a contaminated sample with about atomic/d precipitation, the Cu residual rate was 4 to 6%, which was quite good and can be said to be the original cleaning effect of SC-1. Good morning. Therefore, trichlorethylene treatment was found to reduce the ability of SC11 cleaning. When SC-2 cleaning, which is widely used by LSI manufacturers due to its good cleaning effect on heavy metal impurities, was used instead of SC-1 cleaning, the results were even worse. Hydrochloric acid (l volume) and hydrogen oxide (1 volume)
When SC-2 cleaning consisting of 10 water (5 volumes) was performed at 80°C for 10 minutes, the reduction was only to 4 and 6XIO'' atoms/C-, which was compared to the comparative cleaning test described above for SC-1 cleaning. In this case, a residual rate of at least 7% can be expected, but in this case, the residual rate was over 30%.Even if this SC-1 cleaning or SC-2 cleaning was repeated, the cleaning ability would not improve the second time. The above series of experimental results can be explained by the diffusion of Cu.

In other words, experiments using radioactive isotopes and 4Cu have shown that C has a much higher diffusion rate in silicon than other elements.
It was found that u penetrates into the extremely thin altered layer near the surface created by the mechanical process of mirror polishing, even at temperatures around 87°C, the boiling point of trichlorethylene. Trichlorethylene does not dissolve Cu ions adsorbed on the silicon surface at all, nor does it have the function of forming a layer that can trap Cu, such as a natural oxide film. Therefore, in the trichlorethylene treatment, only the Cu attached to the very surface layer can be removed together with the abrasive and the like. Cu trapped below the surface becomes difficult to clean and S
It seems that the effectiveness of C-1 and SC-2 cleaning is reduced, and the reason why SC-2 cleaning is even worse is probably because it does not have an etching effect. Therefore, an organic solvent that can sufficiently reduce the CuJ degree is required at the wax removal stage.

(1) The ability to release Cu adsorbed during the mirror polishing process is greater than that of trichlorethylene.

(2) There is a wax that is soluble in this solvent and has adhesive strength that enables precise polishing.

(3) Low evaporation to avoid environmental pollution. 20 as a guide
The vapor pressure at °C is 0. OL IIlmog and below.

Triethylene glycol monoalkyl ether and tetraethylene glycol monoalkyl ether were found as organic solvents that satisfy the above three conditions. When heated to temperatures below 100°C, where the vapor pressure is very low, it is almost odorless and evaporation can be ignored. In addition, there are glycol phthalate-based waxes that are soluble in this wax and have suitable adhesion for polishing (as disclosed in published patents). Publication [A] 1986-16477
7 and Showa 62-219526). Here, the inventor of the present invention used these organic solvents to reduce the residual rate of Cu after wax removal treatment to about 20% of the Cu adsorbed on the silicon polished surface, that is, 1/2 to 1/3 of that in the case of trichlorethylene treatment.
This could be reduced to The removal effect on Cu is a property of these organic solvents themselves, regardless of the type of wax.

Moreover, the present organic solvent treatment provides a unique effect on the Cu removal ability of the subsequent sc-i cleaning. In the case of trichlorethylene treatment, the subsequent SC-1 cleaning significantly reduced the Cu removal effect, but after this treatment, S
The Cu residual rate after C-1 cleaning is 6-10%, which is about 1% of the former.
/2, and the removal effect has been improved to almost the ability of the original SC-1. From this result, it is presumed that the present organic solvent prevents Cu from penetrating into the interior during the treatment and captures less Cu in the altered layer, thus improving the SC-1 cleaning effect.

However, SC-1 cleaning causes ammonia gas environmental contamination, which has a subtle effect on the wafer. Therefore, the ammonia component of SC-1 was replaced with a strong organic alkali that does not cause environmental pollution due to vaporization, such as a 1% by weight aqueous solution of tetramethyl ammonium hydroxide, that is, this aqueous solution (1 volume).
80℃ with a treatment solution of 10 hydrogen peroxide (1 volume) and 10 water (5 volumes).
A 10 minute wash followed the organic solvent wax removal treatment. When the purity of the chemicals in this solution was high, foaming was weaker than in SC-1, and ultrasonic cleaning could be effectively performed with less mist generation. The residual ratio of Cu remaining after wax removal after the main cleaning was 5 to 7%, which was a good result that was slightly higher than the SC-1 cleaning. Na * Fe + C
For r + Co + Nt, a radioactive isotope was used as a tracer, and for /l and Zn, using the above analysis method, the removal effect of this cleaning was expressed as a residual rate for a wafer with approximately (1 to 5) XIO'' atoms/cd attached, respectively. Seeking SC
This was compared with the case of -1 cleaning. The results are quite similar, with Fe and 1 not having very good cleaning effects, and other elements being able to be cleaned satisfactorily with a residual rate of less than 5%. In addition, the particulate removal effect of the main cleaning was compared with that of the SC-i cleaning for trichlorethylene-treated wafers where a large amount of particulate contamination occurs, and the results were almost comparable.

The higher the concentration of organic alkali, the lower the concentration of hydrogen peroxide, and the higher the processing temperature, the better the cleaning effect for both chemical and particulate contamination, but in these directions, etching is accelerated and pits are formed. This causes the surface to become rough. The concentration range that is practical as a cleaning solution is 0.01-
1% by weight, hydrogen peroxide o. t - t % by weight. Similar cleaning solutions can be prepared for other strong organic alkalis in the same concentration range, and results with no significant difference in cleaning effectiveness were obtained;
The following treatment is odorless and organic pollution to the environment can be ignored.

Therefore, in the mirror polishing process, by removing wax with triethylene glycol monoalkyl ether and/or tetraethylene glycol monoalkyl ether, followed by cleaning with strong organic alkali and hydrogen peroxide, the environmental atmosphere due to chemical evaporation and mist generation is removed. It has become possible to clean the silicon wafer surface by suppressing secondary contamination from carbon dioxide and reducing the Cu concentration to around 10111 atoms/cd.

Further, since triethylene glycol monoalkyl ether or tetraethylene glycol monoalkyl ether mixes freely with water and is alkaline and difficult to deteriorate, a small amount of a strong organic alkali and a highly concentrated aqueous solution of a surfactant can be added. By adding this, the liquid has a weak etching ability and can remove tens of λ of the silicon surface deterioration layer, so that the removal power for deposited Cu is further increased. Furthermore, since this addition increases the wax/dilute removal ability, the removal treatment temperature can be lowered. In this case, several to tens of ppm of EDTA, CVDTA. Addition of a complexing agent such as TTHA often enhances the Cu cleaning effect.

Therefore, the subsequent treatment with strong organic alkali and hydrogen peroxide can reliably reduce the Cu concentration on the surface to below IQIO atoms/cd. The addition of an organic alkali and a surfactant enhances the solvent's ability to dissolve wax, and the purpose can be achieved without heating too strongly during wax removal, that is, at around 40 to 50°C. Lowering the temperature further helps to suppress the diffusion of Cu into the silicon.

By the way, the positive photoresist normally used in LSI is made of an alkali-soluble phenolic resin and a quinone azide photosensitizer that becomes alkali-soluble when irradiated with light. For example, products containing triethanolamine have the ability to remove this type of resist. Although this processing liquid has a slightly slower peeling speed than existing organic solvent-based resist removers, it has the advantage of causing almost no organic contamination to the environmental atmosphere.

However, as in the case of wax removal, the peeling speed can be increased to a practically sufficient level by adding a small amount of a strong organic alkali and a surfactant.
As mentioned above, the organic solvent of the present invention has a removing effect on Cu, but when an organic alkali is added thereto, a complexing action occurs and the effect is enhanced. Furthermore, when a strong organic alkali is added, an etching effect is accompanied and the cleaning effect is accelerated. Then, as in the case of wax removal, cleaning with a strong organic alkali and hydrogen peroxide is followed to ultra-clean not only resist impurities but also metal element contamination from process equipment in the photolithography process to less than 1Ol0 atoms/c4. It can be transformed into

As described above, the present invention removes organic matter adhering to a semiconductor silicon wafer using a liquid containing at least one of triethylene glycol monoalkyl ether and tetraethylene glycol monoalkyl ether as a main ingredient, and then The present invention provides a wafer cleaning method that suppresses secondary contamination from a contaminated environmental atmosphere caused by chemicals and effectively reduces the surface Cu concentration of silicon wafers by cleaning with alkali and hydrogen peroxide. .

Triethylene glycol monoalkyl ether or tetraethylene glycol monoalkyl ether, which is the organic matter removing agent in the present invention, has a vapor pressure of 0.0 at 20°C, regardless of whether the alkyl group is methyl, ethyl, proyl, butyl, etc. 0 1 +u+Hg or less, and there is no significant difference in the removal effect against Cu. Therefore, they may be selected depending on the nature of the organic matter to be removed, and two or more types may be used in combination if necessary.

The vapor pressure at 20°C is 0. The reason why the temperature is limited to 0.01 msHg or less is that as long as this condition is satisfied, the commonly used removal treatment at 100°C or less is almost odorless, does not generate evaporation or mist, and organic contamination of the environment can be avoided. Therefore, the vapor pressure of any substances added to the organic solvent must be similarly limited. Therefore, examples of alkaline organic solvents that can be added in the present invention include triethanolamine and tetraethylenebentamine.
Up to about % by weight. Addition of a strong organic alkali or surfactant has a clear effect even in a small amount, and the effect can be seen at 0.01 weight % or more and several weight % or less.

The strong organic alkali used for cleaning in combination with hydrogen peroxide in the present invention is not effective unless it is a 1% by weight aqueous solution with a pH of 12 or higher at room temperature. That is, for example, tetramethyl ammonium hydroxide, choline, guanidine, etc., and their carbonates, silicates, etc. are applicable. Among these, choline has a fishy odor when it is in high concentration, and guanidine easily decomposes unless it is salt. The most suitable is tetramethyl ammonium hydroxide.

In addition, in the method of the present invention, a conventionally known dilute hydrofluoric acid treatment can be used in combination, if necessary.

〔Example〕

The present invention will be explained in detail below by comparing it with a conventional method using examples. Hereinafter, "%" representing concentration means "% by weight".

Example 1 A polishing machine equipped with four wafer mount plates for single-sided mirror polishing of silicon wafers, two of which were equipped with the organic solvent-soluble wax proposed in the present invention, that is, the glycol phthalate-based wax manufactured by Nikka Seiko Co., Ltd. Wax “Phthalic Blue” (
For comparison, we glued four pieces of way eight each using conventional general paraffin wax (denoted as symbol (P) below) for comparison. We performed mirror polishing to create a standard specification mirror polished wafer. In addition, the abrasive liquid was sampled during polishing, and the Cu concentration was measured and confirmed to be 10 to 20 ppb. Wafers with attached wax (Nl) are removed by treatment with triethylene glycol monomethyl ether at 70°C/lO (hereinafter referred to as the wax removal treatment using an organic solvent of the present invention (BGRE treatment)), and after rinsing with pure water. Subsequently, an aqueous solution of O. 1% tetramethyl ammonium hydroxide and 5% hydrogen peroxide was heated to 80°C and subjected to ultrasonic cleaning for 10 minutes (hereinafter, the cleaning treatment using a strong organic alkali/hydrogen peroxide of the present invention will be referred to as [OAHO Wafers with wax CP) adhered to them are removed by treatment with trichlorethylene at 70°C for 10 minutes (hereinafter, this conventional wax removal process is abbreviated as (TCE treatment)). After water rinsing, SC-1 cleaning was subsequently performed. During both cleaning processes, four 1111 wafers were sequentially subjected to the above-mentioned surface analysis to track the cleaning status of Cu adsorbed on the surface during polishing. The results are compared and shown in the figure.A glance at the figure shows that even after wax removal,
It can be seen that even after the cleaning treatment, when wax was removed using triethylene glycol monomethyl ether, the effect of removing Cu was clearly high. The effect of alkaline hydrogen peroxide treatment on Cu is remarkable within the first 3 minutes of cleaning, and therefore, it can be said that the cleaning effect is related to the ease with which the contamination of Cu can be removed before starting this cleaning, that is, the wax removal method.

Example 2 Using a polishing machine in the same manner as in Example 1, using (N) wax, [EGRE treatment] was performed with triethylene glycol monoethyl ether at 70°C for 10 minutes, and Fe
After a 10-minute immersion treatment in diluted hydrofluoric acid diluted 200 times with water to compensate for the lack of cleaning ability for
OAIO cleaning] was compared with conventional (P) wax, (TCE treatment), diluted hydrochloric acid treatment under the same conditions, and SC-1 cleaning. The Cul degree was analyzed. Two wafers were provided for each condition, and the results obtained for each wafer are shown in Table 1.

Table 1 Even if dilute hydrofluoric acid treatment was applied after wax removal, it cannot be said that either treatment was particularly effective as far as Cu removal was concerned.
What is clear from this example is that even if monomethyl ether is changed to monoethyl ether, the Cu removal effect after wax removal and after cleaning treatment (EGRE treatment) is superior to conventional treatment. Example 3 A polishing machine was used in the same manner as in Example 1, and a phthalate wax (hereinafter abbreviated as CM), which was prototyped by Mitsui Toatsu Chemical Co., Ltd. as being particularly suitable for (EGR2 processing), was used. After attaching the wafer to the mount plate and polishing, wax was removed using tetraethylene glycol monomethyl ether, followed by the first cleaning.
The wafer on the mounting plate is coated with a strong organic alkali, choline 0.
1% and 5% hydrogen peroxide (cleaning process N
+lL1), and the second mount plate uses tetramethyl ammonium hydroxide as a strong organic alkali (Nα2
), and the third mounting plate was made using guanidine carbonate as a strong organic alkali (Na3). The remaining mounting plates were made using a conventional process using (P) wax and [T
CE treatment] and SC-1 cleaning.

These four processes were carried out in a special clean booth in which high-purity nitrogen was introduced independently, and the treatment tanks were arranged side by side, and the treatment temperature and treatment time were the same as in Example 1. After cleaning, the wafers were rinsed with pure water and left in the booth to air dry.

The surface Cul of the wafer during the cleaning step for each process.
Analysis was carried out nine times, and the cleaned wafers were subjected to Auger electron spectroscopy to determine whether or not there was organic environmental contamination based on the presence or absence of a 272 eV C peak. The results are shown in Table 2.

Table 2 Unit IQII + Atom/CTII Even if triethylene glycol is changed to tetraethylene glycol or the type of strong organic alkali is changed, the cleaning effect is almost the same as in the previous example. Great removal ability. There is also a difference in the C concentration on the surface of the cleaned wafer, and since the chemicals used in the present invention consist of only three elements, C, O, and H, there is concern about C contamination either directly or as a result of secondary contamination after scattering into the environment. However, as a result of Auger analysis, no C was detected, which satisfies one of the conditions for ultra-cleanliness. If the concentration of choline is as high as in this example, the environmental pollution can be ignored. In conventional methods, C contamination of the wafer through environmental atmosphere contamination caused by processing chemicals is unavoidable.

Example 4 (M) wax was used for all mounting plates, the polishing machine was treated as in Example 1, and 0.8% by volume of a 25% aqueous solution of tetramethyl ammonium hydroxide in triethylene glycol monomethyl ether was used. , 0.0% polyoxyethylene nonionic surfactant (solid content 30%). 1% by volume, more I! Wax was removed by ultrasonic cleaning at 45° C. for 10 minutes using a wax remover made by adding 30 ppm of DTA. The wafers for the two mounting plates were then prepared using Example 1 using tetramethyl ammonium hydroxide.
OAHO cleaning] and SC-1 cleaning for the rest. The changes in surface Cu concentration at each stage of cleaning were measured. Two wafers were provided for each condition, and the results obtained for each wafer are shown in Table 3.

Table 3 Unit: 10l0 atoms/cnl Because a trace amount of alkali, surfactant, and complexing agent were added to the wax removal agent as a wax removal promoter and a Cu dissolution promoter on the silicon surface, wax removal was performed at a relatively low temperature. Regardless, a strong Cu removal effect was obtained at this stage. Lowering the temperature is thought to reduce the diffusion of Cu into the interior, and therefore the subsequent cleaning process is performed using a strong organic alkali.
Effectively removes C from both hydrogen peroxide and ammonia/hydrogen peroxide.
The u removal effect continues.

Example 5 After mirror polishing using wax (M) as in the above example, the wax was removed by adding 1% by volume of a 25% aqueous solution of tetramethyl ammonium hydroxide to triethylene glycol monobrobyl ether, which was different from Example 4. Polyoxyethylene nonionic surfactant (solid content 30%) 0. 0 5
10% by volume at 45°C.
Performed under ultrasound for minutes. After rinsing with pure water, perform tetramethyl ammonium hydroxide (AOHO cleaning), rinse with pure water, and use dilute HC/! with 2% hydrofluoric acid added according to Patent No. 638281! (1:1) at 20°C for 10 minutes.

The analysis results of the wafer surface after cleaning showed Cu, Na,
K, Ca+ Fe, l/! +Cr. All Zn values were below IQIII atoms/cd.

Example 6 A commercially available semiconductor body resist with a thickness of 1.5 μI was applied to a silicon wafer with an oxide film of 500 mm thickness.
After pre-baking at 90° C. for 30 minutes, exposure and development was carried out in the usual manner using a test pattern mask, and a resist pattern was created through post-baking at 140° C. for 30 minutes. O for this! Plasma etching is 0. After removing the resist by ashing at 8 Torr and 200°C, and dissolving the oxide film with a small amount of ultra-high purity hydrofluoric acid, total internal reflection X-ray fluorescence analysis was performed using the method described above. Cu of c4 was detected.Next, the Lenist pattern oxide film wafer was diluted with tetramethyl ammonium hydroxide 2 in a solution of 70% triethylene glycol monomethyl ether and 30% triethanolamine.
It was treated at 90°C with a stripping solution containing 0.2% by volume of a 5% aqueous solution and 0.05% by volume of a polyoxyethylene nonionic surfactant (30% solids) at 90°C. Subsequent washing was performed using tetramethylammonium hydroxide (AOHO) from Example I.
washing) was performed. The surface condition after treatment was observed using an electron microscope with monochromatic light at a magnification of 800 times, but no resist remained, and Auger analysis was performed on the surface, but no C was detected. In addition, analysis of the oxide film of another wafer subjected to the same resist removal process revealed that Cu is IQIO atoms/cii
Met.

〔Effect of the invention〕

As described above, the method of the present invention can easily remove organic substances attached to wafers, such as silicon mirror polishing wax and photolithography resist, and can also remove Cu, which is particularly difficult to clean, and which is probably caused by the generation of a degraded layer. , effective ultra-cleaning has become possible with unique processes ranging from organic matter removal to cleaning.

Naturally, similar effects can be obtained with other elements.

Cleaning of oil, fingerprints, etc. is much easier.

The method of the present invention not only eliminates the need for polluting chlorinated organic solvents such as trichlorethylene, sulfuric acid, etc., but also the organic solvents proposed in the present invention have extremely low vapor pressures and hardly pollute the environmental atmosphere. . This is very important for ultra-cleanliness because there is no risk of secondary chemical contamination, such as ammonia gas contamination, on the wafer surface via the environmental atmosphere caused by chemicals, and it is important for yield and reliability for ultra-high performance devices. Effects can be expected on the surface. In addition, the organic solvent used in this treatment is used for wax, resist, water, organic alkali, etc.
All surfactants, complexing agents, etc. are removed by vacuum distillation, allowing almost 100% recovery, making it highly economical.

[Brief explanation of drawings]

The figure shows the results of Example 1.

Claims (2)

[Claims] (1) After treating a semiconductor silicon wafer with organic matter attached to it with a liquid containing at least one selected from triethylene glycol monoalkyl ether and tetraethylene glycol monoalkyl ether as a main ingredient, a strong organic alkali and hydrogen peroxide are added. An ultra-cleaning method for the surface of silicon wafers, which is characterized by performing cleaning treatment with an aqueous solution containing (2) A silicon wafer for semiconductors to which organic matter has been attached is made of at least one selected from triethylene glycol monoalkyl ether and tetraethylene glycol monoalkyl ether as a main ingredient, further contains an organic alkali, and all components are heated at 20°C. Vapor pressure is 0.01
An ultra-cleaning method for the surface of a silicon wafer, which is characterized in that the surface of a silicon wafer is treated with a low-evaporation treatment liquid having a temperature of mmHg or less, and then a cleaning treatment is performed with an aqueous solution containing a strong organic alkali and hydrogen peroxide.