JPH09255991A - Surface-treating solution and process for treating substrate surface - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively prevent a substrate from causing the redeposition of metal ions eluted in an alkaline treating soln. by incorporating a specified sequestering agent into the soln. so as to remove the metal staining the surface of the substrate to be treated by using a small amount of the additive. SOLUTION: Since a metal ion coordinated with H2 O or OH in an alkaline treating soln. easily adheres to a substrate, an electron is fed into the metal ion to reduce the positive charge or to make it negative, thereby inhibiting the bonding of the metal ion to the substrate surface. For this purpose, the surface-treating sol. contains at least one of the following sequestering agents (1), (2) and (3): (1) diethylenetriaminepentaacetic acid of such a concn. that the wt. ratio thereof to the eluted iron ion is at least 3,000:1 and the one to the zinc ion eluted from the treated substrate is at least 30,000:1, (2) triethylenetetraminehexaacetic acid of such a concn. that the wt. ratio thereof to the copper ion eluted from the treated substrate is at least 40,000/1 and the one to the nickel ion is at least 40:1, and (3) glutamic acid of such a concn. that the wt. ratio thereof to aluminum ion eluted from the treated substrate is at least 30,000:1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface treatment liquid and a surface treatment method for removing contaminant metals and preventing adhesion thereof, which are suitable for treatments requiring high cleanliness, such as semiconductor device manufacturing processes. .

[0002]

2. Description of the Related Art In the manufacture of semiconductor devices, not only contamination due to foreign substances but also contamination due to metals has become a serious problem as element structures have become finer and thinner. Especially,
Contamination of a semiconductor device with aluminum, iron, nickel, copper, or zinc causes defects in the electrical characteristics of the element such as deterioration of lifetime and defective oxide film withstand voltage.

Nowadays, as the surface area of a substrate increases due to the increase in size of the substrate, the amount of metal ions eluted in the surface treatment solution for removing the contaminated metal increases, and the problem of metal contamination becomes more serious. There is. Therefore, the amount of metal ion contamination on the surface of the semiconductor substrate is set to 1 × 10 ¹⁰ atoms / cm 2.
² or less technology is required ("Technology for cleaning silicon wafer surface", pages 3 to 9 (published by Realize,
Published February 1995)).

In order to prevent metal contamination, materials such as ceramics (SiC) having a low content of metals leading to contamination have been conventionally used in manufacturing equipment and transportation equipment.
However, metals such as aluminum and copper used for semiconductor materials such as wiring materials cannot be ignored as pollution sources. Further, in terms of cost, strength, and characteristics, some parts of the manufacturing apparatus have no choice but to use metal, and these metal parts are also sources of pollution. In particular, since the back surface of the substrate is in contact with the transfer jig, the amount of contamination increases. In addition, depending on the treatment process, metal contamination cannot be avoided. In particular, CVD (Chemical Vapor Deposition) using plasma and ions
In processes such as Deposition), dry etching, and ion implantation, the amount of metal contamination is particularly large. According to "Cleaning Technology for Silicon Wafer Surface", pages 18 to 23 (published by Realize Co., Ltd., February 1995), the amount of metal contamination adhered to the substrate surface after these steps is 1 × 10 ¹² iron.
atoms / cm ² or more, 1 × 10 ¹¹ a with copper or nickel
More than toms / cm ² .

As described above, it is almost impossible to completely prevent the contamination metal from adhering to the substrate in the manufacturing process. Therefore, it is essential to remove the contaminated metal adhering to the substrate surface in each step of the manufacturing process in the cleaning step. In today's cleaning process, the metal ion content of the surface treatment liquid is suppressed to the limit, and the cleaning equipment
A material having a metal content as low as possible, for example, a resin such as polytetrafluoroethylene or quartz, is used not only in the liquid contact part but also in the device parts. This is to prevent adhesion of contaminated metal in the cleaning process.

In the above-mentioned processes such as CVD, dry etching and ion implantation, not only metal contamination but also contamination due to foreign matter is severe. Therefore, in general, the substrate that has undergone these steps is cleaned by a cleaning method using an ammonia-hydrogen peroxide cleaning solution that is effective in removing foreign matter (hereinafter referred to as "SC-1 cleaning").
Called) (“RCA Review” No. 1)
87-206 (issued June 1970)). In addition, as the ammonia-hydrogen peroxide cleaning liquid, a mixed liquid (NH ₄ OH (27
_{%): H 2 O 2 (} 30%): H 2 O = 1: 1: 5~1:
A volume ratio of 2: 7) is used. This cleaning solution
Hereinafter referred to as "SC-1 cleaning solution".

When a substrate contaminated with a metal is immersed in the SC-1 cleaning solution, the metal adhering to the surface of the substrate is oxidized by the oxidizing action of hydrogen peroxide and is eluted as a metal ion in the cleaning solution. For example, the above-mentioned 1 × 10 ¹² atoms / cm ²
The concentration of metal ions eluted and accumulated in the cleaning solution is 0.01 p by simply cleaning 25 pieces of the 8-inch diameter substrate contaminated with the metal with 50 liters of SC-1 cleaning solution.
becomes pb. When treated with a cleaning solution containing 0.01 ppb of these metal ions, 1 × 10 ¹⁰ was generated due to an adsorption phenomenon.
Metal ions of atoms / cm ² adhere to the substrate surface. That is, in this method, the number of metal ions on the substrate is 1
It is only reduced to / 100. Generally, in SC-1 cleaning, 250 substrates are processed per 50 liters of cleaning liquid in terms of semiconductor production rate, so the amount of metal ion contamination is greater than in the above example.

As described above, the SC-1 cleaning solution is effective in removing foreign matters due to the oxidizing action and the etching action, but the contaminated metal removed from the front and back surfaces of the substrate and eluted in the processing liquid re-cleans the clean surface. Since it contaminates, the effect of suppressing the amount of metal ion contamination is not sufficient.

Therefore, as a method for solving the metal contamination problem, Kern has proposed a cleaning method using hydrofluoric acid containing ethylenediaminetetraacetic acid (hereinafter abbreviated as EDTA) as a chelating agent (“RCA Revie”).
w "pp. 234-264 (issued in June 1970)). The chelating agent can prevent the re-adsorption of the metal ion released from the substrate to the substrate by capturing the metal ion by the coordinate bond.

However, as is well known in the field of solution chemistry,
The chelating effect of metal ions increases as the cleaning solution becomes more alkaline. Therefore, a cleaning method using a cleaning liquid in which a chelating agent having a phosphonic acid group is added to an alkaline SC-1 cleaning liquid has been proposed (JP-A-5-275).
405).

[0011]

With the recent advances in semiconductor production equipment, the types of metals adhering to substrates increase year by year, and there are various types of metals such as aluminum, iron, nickel, copper and zinc. This is because iron, nickel, copper, and zinc contained in materials such as the substrate transport system of the production equipment and the processing chamber, and aluminum and copper as wiring materials on the substrate adhere to the substrate as contaminant metals. is there. However, the above-mentioned chelating agent having a phosphonic acid group is extremely effective for iron but does not have sufficient coordination ability for aluminum, nickel, copper and zinc.

The chelating agent having a phosphonic acid group contains phosphorus (P) in its molecular skeleton. Therefore, when this compound is adsorbed on the substrate and P diffuses into the substrate in the heat treatment step, an n-type layer is formed, which causes a change in the characteristics of the semiconductor.

Further, when a metal ion scavenger such as a chelating agent is added to the SC-1 cleaning liquid and used, the contamination with organic substances (metal ion scavengers) and
Problems such as an increase in the cost of additives and waste liquid treatment also occur. Therefore, it is desirable to reduce the addition amount of the metal ion scavenger as much as possible.

Therefore, the present invention uses an alkaline treatment liquid to contaminate the surface of the object to be treated (in particular, aluminum, iron,
A surface treatment solution capable of effectively preventing recontamination of the substrate by metal ions eluted in the treatment solution with a small amount of an additive when removing at least one of nickel, copper and zinc). It is an object to provide a surface treatment method.

[0015]

[Means for Solving the Problems] In order to solve the above problems, the present inventors theoretically elucidated the adsorption mechanism of metal ions on a substrate by quantum chemical calculation, and found the concentration distribution of metal ion species in a liquid. Invented a method for preventing the contamination of the substrate with respect to all of the problematic metal ions by finding the adsorbed ion species and adding the most effective metal scavenger depending on the type of metal ions. The description will be made in the following order.

First, the mechanism of metal ion adsorption on the substrate surface will be described. On the surface of the substrate in the SC-1 cleaning solution, an oxide film having a film thickness of 5 to 10 angstrom is formed by the oxidizing action of hydrogen peroxide. Most of the surface of the oxide film is covered with O ⁻ because the pH of the SC-1 cleaning solution is higher than 3. It is covered with OH ₂ ⁺ in an acidic treatment liquid having a pH of less than 2, and with OH in a treatment liquid having an equipotential point of pH 2 to 3.

Therefore, the adsorption energy of metal ions on the surface of the oxide film was determined by quantum chemical calculation according to the surface state. As an example, FIG. 1 shows the case of Fe ions and Cu ions. As shown in FIG. 1, in the case of a neutral to alkaline treatment liquid having a pH higher than 3, pH 2
The adsorption energy becomes significantly higher than that in the acidic treatment liquid of less than. The increase in the adsorption energy indicates that the equilibrium relationship between the adsorption and desorption of the metal ion on the substrate is largely biased to the adsorption state. That is, it can be seen from FIG. 1 that metal ions are easily adsorbed under alkaline conditions. Therefore, SC-
Metal ion contamination is likely to occur in a treatment liquid having a pH higher than 3, such as 1 cleaning liquid.

From the result of the quantum chemical calculation, it was found that the adsorption energy between the substrate surface and the metal ions is an interaction due to the Coulomb force due to the positive and negative charges. Therefore, it is possible to prevent the metal ions from adsorbing to the substrate by giving electrons to the metal ions having a positive charge to reduce the positive charge or making the negative charge to eliminate the adsorption energy.

As a method of changing the charge of the metal ion, it is possible to coordinate a ligand having a large electron donating property. Therefore, when the adsorption energy between the metal ion coordinated with a ligand having a large electron donating property and the substrate was calculated by quantum chemical calculation, as shown in FIG. 2, Fe ion has a reduced adsorption energy and Cu ion has It became negative energy. This is because not only the positive charge of the metal ion is reduced, but also the ligand having a negative charge covers the metal ion, so that the Coulomb repulsive force is generated between the negatively charged substrate surface and O ^−. This is because. From the above, it was found that coordination of a ligand having a large electron donating property prevents adsorption of metal ions.

Next, in order to verify the result of the quantum chemical calculation, an experiment was conducted in which the substrate was immersed in an alkaline treatment liquid contaminated with metal ions. In FIG. 3, C is shown as a contaminant metal ion.
The relationship between the immersion time of the substrate and the amount of metal ion contamination on the substrate surface when u ions are used is shown. In addition, in order to remove the oxidizing action and the etching action from the SC-1 cleaning solution, the treatment solution was adjusted to pH with ammonium chloride and ammonia.
The alkaline treatment liquid adjusted to 10 was used.

As can be seen from FIG. 3, the amount of metal ion contamination increases with the immersion time and depends on the concentration of metal ion contamination in the treatment liquid. From this, it was found that the adsorption of metal ions is a diffusion-controlled reaction on the substrate surface. Therefore, the contamination can be reduced by lowering the concentration of the metal ion species adsorbed on the substrate in the treatment liquid.

Next, an experiment was conducted in which a metal ion scavenger (ligand) was added to an alkaline treatment liquid contaminated with metal ions, and then the substrate was dipped to measure the adsorption amount of metal ions. Cu is used as a pollutant metal ion, and triethylenetetramine hexaacetic acid (hereinafter,
The result of the experiment using TTHA) is shown in FIG.
Shown in The horizontal axis of FIG. 4 represents the addition amount of the metal ion scavenger by the molar ratio with Cu ions in the treatment liquid, and the vertical axis represents the adsorption amount of Cu ions on the substrate. As can be seen from FIG. 4, the amount of metal ion contamination on the substrate decreases as the amount of metal ion scavenger added increases.

From the results of the above-described quantum chemical calculations and experiments, by using a treatment liquid containing a metal ion scavenger that forms a metal complex by coordinating with metal ions, metal ion species that are easily adsorbed on the substrate surface are It was found that the metal ion contamination on the substrate can be prevented by changing to a metal complex that does not adsorb.

Next, the concentration distribution of the metal ion species in the alkaline treatment liquid was determined by using known equilibrium constants ("Stability Constants of Metal-Ion Complexes: Par", published by Pergamon Press).
t B Organic Ligands ”). As an example, FIG. 5 shows the result of obtaining the concentration distribution of each ionic species present in the treatment liquid when TTHA was added to the alkaline treatment liquid (aqueous ammonia solution) contaminated with Cu ions. In FIG. 5, the horizontal axis represents the addition amount of the metal ion trapping agent as in FIG. 4, and the vertical axis represents the concentration of each metal ion species in the treatment liquid.

The metal ion species adsorbed on the substrate are a hydrate ion species coordinated with H ₂ O, a hydroxide ion species coordinated with OH, and an ammonium ion species coordinated with ammonia. As can be seen from FIGS. 4 and 5, when the metal ion scavenger is added in an amount that makes the concentration of the metal hydroxide ion species 1 × 10 ⁻²⁰ mol / liter or less, the contamination amount on the substrate is 1 × 10 5. It could be set to ¹⁰ atoms / cm ² or less.

The same calculation was performed for the SC-1 cleaning solution. As with the above case, the concentration of the metal hydroxide ion species present in the SC-1 cleaning solution was 1 × 10.
It was found that the amount of contamination on the substrate can be reduced to 1 × 10 ¹⁰ atoms / cm ² or less by setting the ^{concentration to −20} mol / liter or less.

Therefore, in order to select a metal ion trapping agent that effectively traps this ionic species, the equilibrium constant with the metal ion to be trapped was examined for various trapping agents. That is, for each metal ion of Al, Cu, Ni, Fe, and Zn, a scavenger (ligand) having a large equilibrium constant with the metal ion is extracted, and SC-1 when the scavenger is used The concentration distribution of metal ions in the cleaning liquid was calculated. In Table 1,
The equilibrium constant of each metal ion scavenger and the addition amount required to bring the concentration of the adsorbed ion species in the washing solution to 1 × 10 ⁻²⁰ mol / liter are summarized. In Table 1, T
THA represents triethylenetetramine hexaacetic acid, DTP
A represents diethylenetriaminepentaacetic acid, EDTA represents ethylenediaminetetraacetic acid, and AP represents 2-aminopropane-2-phosphonic acid.

[0028]

[Table 1]

As can be seen from this table, glutamic acid is used for Al and TTHA is used for Cu and Ni.
(Triethylenetetramine hexaacetic acid), Fe and Zn
For DTPA (diethylenetriaminepentaacetic acid)
However, it was found that the concentration of the adsorbed ion species in the cleaning liquid can be reduced to 1 × 10 ⁻²⁰ mol / liter or less with the smallest addition amount.

Based on the above findings, in order to achieve the above object, the present invention provides an alkaline surface treatment liquid for removing contaminant metals on the surface of an object to be treated with diethylenetriaminepentaacetic acid and triethylenetetraminehexaacetic acid. , And a surface treatment solution containing at least one metal ion scavenger of glutamic acid, and a surface treatment method using the surface treatment solution. Diethylenetriaminepentaacetic acid
It is a scavenger of iron and zinc ions, triethylenetetramine hexaacetic acid is a scavenger of copper ions and nickel ions, and glutamic acid is a scavenger of aluminum ions. The surface treatment liquid containing all of these three kinds of scavengers can prevent re-adsorption of iron ions, zinc ions, copper ions, nickel ions, and aluminum ions.

The surface treatment liquid of the present invention is an alkaline aqueous solution, which contains at least one base selected from the group consisting of ammonia and tetramethylammonium hydroxide.
It is desirable to be kept alkaline. Further, in order to oxidize the contaminated metal and release it as a metal ion, it is desirable to contain, for example, 0.01 mol / liter or more of hydrogen peroxide as an oxidizing agent. Examples of such a surface treatment liquid include the above-mentioned SC-1 cleaning liquid to which the above metal ion scavenger is added.

[0032]

BEST MODE FOR CARRYING OUT THE INVENTION In the alkaline processing liquid, as described above, the metal ion species coordinated with H ₂ O or OH is easily adsorbed on the substrate. In order to prevent the bond between these metal ions and the substrate surface from being generated, the Coulomb force between the metal ions and the substrate may be eliminated. This can be realized by sending electrons to the metal ions to make the positive charge small or negative.

A ligand having a large equilibrium constant with a metal ion forms a coordinate bond by delocalizing an unshared electron pair in an empty orbit of the metal ion. As a result of this coordinate bond, the electron density in the metal ion increases, so that the metal ion cannot be bonded to the substrate. Therefore, by using such a metal ion scavenger that functions as an electron-donating ligand, recontamination by metal ions can be prevented. The metal ion scavenger may be dissolved in the treatment liquid in advance, or may be added to the treatment liquid prior to or during the treatment.

The amount of the metal ion scavenger is sufficient to capture the metal ion by complex formation with respect to the amount of the metal ion eluted from the object to be treated and accumulated in the treatment liquid. desirable.

Therefore, the concentration of diethylenetriaminepentaacetic acid is 3000 times or more the weight ratio with respect to the concentration of iron ions eluted from the object to be treated, and the weight ratio with respect to the concentration of zinc ions eluted from the object to be treated. It is advisable to increase it by more than 30,000 times. The concentration of triethylenetetramine hexaacetic acid is 40,000 times or more by weight the concentration of copper ions eluted from the object to be treated, and 40% by weight relative to the concentration of nickel ions eluted from the object to be treated.
It is desirable to make it twice or more. The concentration of glutamic acid is
It is desirable that the weight ratio is 30,000 times or more the concentration of aluminum ions eluted from the object to be treated.

Since the surface treatment liquid and the surface treatment method of the present invention can effectively prevent recontamination by metal ions with a small amount of an additive (metal ion scavenger), a semiconductor device which requires particularly high cleanliness. It is suitable for cleaning semiconductor substrates in the manufacturing process. As described above, the amount of the metal ion scavenger is preferably determined according to the amount of the metal ions to be eluted, but when it is used for cleaning the substrate in the manufacturing process of the semiconductor element, it is usually 1 × 10 ⁻⁷ to 1 x 10
Within the range of ^-1 % by weight, a sufficient effect of preventing re-adsorption of metal ions can be obtained.

[0037]

【Example】

<Example 1> In this example, Al of a treatment liquid to which glutamic acid was added as a scavenger (ligand) for trivalent Al ions.
The effect of preventing ion contamination was verified. As the treatment liquid, 27 wt / vol% aqueous ammonia solution and 30 wt
/ Vol% hydrogen peroxide water, 10 ppm aluminum nitrate aqueous solution was added dropwise to a cleaning solution which is a mixed solution of water (volume ratio 1: 1: 5), and a predetermined amount was added to the solution having an Al ion concentration of 10 ppb. Glutamic acid was added and dissolved.

A silicon substrate whose surface is kept clean (the amount of Al contamination on the surface is below the detection limit) is dipped in this treatment liquid kept at 80 ° C. for 10 minutes, and then dipped in pure water for 10 minutes. The amount of Al contamination on the substrate surface was measured by analysis. FIG. 6 shows the results.

According to this embodiment, the cleaning liquid contains 3 × 10 ^-2 wt.
%, The amount of aluminum contamination of the substrate can be detected at the detection limit (1 × 10 ¹⁰ atoms / c).
m ²⁾ may be referred to be below was demonstrated.

Comparative Example 1 Instead of glutamic acid, ethylenediaminetetraacetic acid (abbreviated as EDTA) or 2
In the same manner as in Example 1 except that -aminopropane-2-phosphonic acid (abbreviated as AP) was used, the aluminum contamination preventing effect of these chelating agents was measured. The results are shown in FIG. 6 together with the results of Example 1. As can be seen from FIG. 6, EDTA and AP were not effective in preventing contamination by aluminum.

Example 2 In this example, triethylenetetramine hexaacetic acid (TTHA) for divalent Cu ions is used.
Abbreviated) was verified. In this embodiment, as the treatment liquid, a cleaning liquid similar to that in the first embodiment is added with 10 p
pm copper nitrate aqueous solution was added dropwise to adjust the Cu ion concentration to 10p.
The pb was added with a predetermined amount of TTHA and dissolved therein.

A silicon substrate whose surface was kept clean (the amount of Cu contamination on the surface was below the detection limit) was dipped in this treatment liquid kept at 80 ° C. for 10 minutes, and then dipped in pure water for 10 minutes, and then subjected to total reflection. The amount of Cu contamination on the substrate surface was measured by fluorescent X-ray analysis. FIG. 7 shows the results.

According to this embodiment, the cleaning liquid contains 3 × 10 ⁻² wt.
It was demonstrated that the amount of copper contamination of the substrate can be made lower than the detection limit (1 × 10 ¹⁰ atoms / cm ² ) by adding TTHA of 10%.

<Comparative Example 2> Instead of TTHA, EDT
The copper contamination preventing effect of these chelating agents was measured in the same manner as in Example 2 except that A or diethylenetriaminepentaacetic acid (abbreviated as DTPA) was used. The results are shown in FIG. 7 together with the results of Example 2. As can be seen from FIG. 7, in order to obtain the same effect as in Example 2, DTPA having a weight 10 times that of TTHA or E having a weight 100 times that of TTHA is used.
Had to use DTA.

<Example 3> In this example, the effect of TTHA for preventing contamination of divalent Ni ions was verified. In this example, as a treatment liquid, a 10 ppm nickel nitrate aqueous solution was added dropwise to the same cleaning liquid as in Example 1,
A predetermined amount of TT for i-ion concentration of 10 ppb
What was added and dissolved was used.

A silicon substrate whose surface was kept clean (the amount of Ni contamination on the surface was below the detection limit) was dipped in this treatment liquid kept at 80 ° C. for 10 minutes, and then dipped in pure water for 10 minutes, and then subjected to total reflection. The amount of Ni contamination on the substrate surface was measured by fluorescent X-ray analysis. The results are shown in Fig. 8.

According to this embodiment, the cleaning liquid contains 3 × 10 ⁻⁵ wt.
It has been proved that the amount of nickel contamination of the substrate can be made below the detection limit (1 × 10 ¹⁰ atoms / cm ² ) by adding TTHA.

<Comparative Example 3> Instead of TTHA, EDT was used.
The nickel contamination preventing effect of these chelating agents was measured in the same manner as in Example 3 except that A or ethylenebis [imino (phenyl) methylenephosphinic acid] (abbreviated as EBIM) was used. The results are shown in FIG. 8 together with the results of Example 3. As can be seen from FIG. 8, in order to obtain the same effect as in Example 3, the ED having a weight 5 times that of TTHA is used.
TA, or 10,000 times the weight of EBIM had to be used.

Example 4 In this example, the effect of DTPA for preventing trivalent Fe ions from contamination was verified. In this example, as a treatment liquid, a 10 ppm iron nitrate aqueous solution was added dropwise to the same cleaning liquid as in Example 1 and the Fe ion concentration was set to 10 ppb, and a predetermined amount of DTPA was added and dissolved. Using.

A silicon substrate whose surface was kept clean (the amount of Fe contamination on the surface was below the detection limit) was dipped in this treatment liquid kept at 80 ° C. for 10 minutes, and then dipped in pure water for 10 minutes. The amount of Fe contamination on the substrate surface was measured by fluorescent X-ray analysis. The results are shown in Fig. 9.

According to this embodiment, the cleaning liquid contains 3 × 10 ⁻³ wt.
It was demonstrated that the amount of iron contamination of the substrate can be made lower than the detection limit (1 × 10 ¹⁰ atoms / cm ² ) by adding DTPA of 10%.

<Comparative Example 4> In the same manner as in Example 4, except that hydroxyethylethylenediamine triacetic acid (abbreviated as HEDTA), EDTA, or TTHA was used in place of DTPA, iron contamination of these chelating agents was performed. The preventive effect was measured. The results are shown in FIG. 9 together with the results of Example 4.
Shown in As can be seen from FIG. 9, in order to obtain the same effect as that of Example 4, TTH of 100 times the weight of DTPA was used.
A or 500 times the weight of EDTA had to be used, with HEDTA having only a slight effect.

In place of DTPA, dihydroxyethylglycine (DHEG) or ethylenebis [imino (2-hydroxyphenyl) methylene (methyl) phosphinic acid] (abbreviated as EBIH) was used, and the same procedure as in Example 4 was performed. The iron contamination effect was measured by HEDT
Similar to A, only a slight antifouling effect was obtained.

<Embodiment 5> In this embodiment, the effect of DTPA on the contamination of divalent Zn ions was verified. In this example, as a treatment liquid, a 10 ppm zinc nitrate aqueous solution was added dropwise to the same cleaning liquid as in Example 1 to obtain a Zn ion concentration of 10 ppb and a predetermined amount of DTPA.
What was added and dissolved was used.

A silicon substrate whose surface was kept clean (the amount of Zn contamination on the surface was below the detection limit) was dipped in this treatment liquid kept at 80 ° C. for 10 minutes, and then dipped in pure water for 10 minutes, and then subjected to total reflection. The amount of Zn contamination on the substrate surface was measured by fluorescent X-ray analysis. The results are shown in FIG.

According to this embodiment, the cleaning liquid contains 2 × 10 ⁻² wt.
It was demonstrated that the amount of zinc contamination of the substrate can be made lower than the detection limit (1 × 10 ¹⁰ atoms / cm ² ) by adding DTPA of 10%.

<Comparative Example 5> Instead of DTPA, EDT
The iron contamination preventing effect of these chelating agents was measured in the same manner as in Example 5 except that A or EBIM was used. The results are shown in FIG. 10 together with the results of Example 5.
As can be seen from FIG. 10, in order to obtain the same effect as in Example 5, EDTA of 100 times the weight of DTPA had to be used, and EBIM had only a slight effect.

<Embodiment 6> In this embodiment, as the treatment liquid, the same cleaning liquid as in Embodiment 1 is used, and aluminum nitrate is added.
Copper nitrate, iron nitrate, nickel nitrate, and zinc nitrate,
An aqueous solution containing 10 ppm each was dropped, and each metal ion concentration was adjusted to 10 ppb. As a metal ion trapping agent, 33 ppm of DTPA and 4 parts of TTHA were added.
0 ppm and 30 ppm of glutamic acid were added and dissolved. The DTPA concentration is 3000 times the Fe ion concentration and 30,000 times the Zn ion concentration. TTHA concentration is 40,000 of Cu ion concentration
And 40 times the Ni ion concentration. The glutamic acid concentration is 30,000 times the Al ion concentration.

A silicon substrate whose surface was kept clean (the amount of Cu contamination on the surface was below the detection limit) was dipped in this treatment liquid kept at 80 ° C. for 10 minutes, and then dipped in pure water for 10 minutes. The amount of Al contamination on the substrate surface was analyzed and Cu, Fe, Ni, Z on the substrate surface was measured by total reflection X-ray fluorescence analysis.
The contamination amount of n was measured respectively. Table 2 shows the results.

[0060]

[Table 2]

In this example, the amount of contamination on the substrate surface is the detection limit (1 × 10 ¹⁰⁾ for all measured metal ions.
It was less than or equal to atoms / cm ² ). From this fact, the treatment liquid of the present embodiment is suitable for Al, Cu, Fe, Ni, and Z.
It was confirmed to have sufficient anti-redeposition ability for all metal ions of n.

Comparative Example 6 The amount of metal ion contamination of the substrate was measured in the same manner as in Example 6 except that no metal ion scavenger was added to the treatment liquid. , For all metal ions measured, 3
A high contamination amount of × 10 ¹⁰ atoms / cm ² or more was detected.

[0063]

As described above, according to the present invention, contaminant metals (Al, Fe, Cu, Ni, Z) in an alkaline treatment liquid are used.
When removing n), recontamination of the substrate due to metal ions eluted in the treatment liquid can be effectively prevented by a small amount of the additive.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing adsorption energies of metal ions and a substrate, which are obtained by quantum chemical calculation.

FIG. 2 is an explanatory diagram showing adsorption energies of metal ions and a substrate obtained by quantum chemical calculation when a metal ion scavenger is added.

FIG. 3 is a substrate immersion time in an alkaline treatment liquid,
It is a graph which shows the relationship with the adsorption amount of a metal ion to a substrate.

FIG. 4 is a graph showing the relationship between the amount of metal ion scavenger added and the amount of metal ion adsorbed on the substrate in the alkaline treatment liquid.

FIG. 5 is a graph showing the relationship between the amount of metal ion trapping agent added and the concentration of metal ion species in the alkaline treatment liquid.

6 is a graph showing the amount of metal ion trapping agent added and the amount of Al ion contamination of the substrate in Example 1 and Comparative Example 1. FIG.

FIG. 7 is a graph showing the amount of metal ion scavenger added and the amount of Cu ion contamination of the substrate in Example 2 and Comparative Example 2.

FIG. 8 is a graph showing the amount of metal ion trapping agent added and the amount of Ni ion contamination of the substrate in Example 3 and Comparative Example 3.

9 is a graph showing the amount of metal ion trapping agent added and the amount of Fe ion contamination of the substrate in Example 4 and Comparative Example 4. FIG.

FIG. 10 is a graph showing the amount of metal ion scavenger added and the amount of Zn ion contamination of the substrate in Example 5 and Comparative Example 5.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location C23G 1/14 C23G 1/14 H01L 21/304 341 H01L 21/304 341L (72) Inventor Sai Oka 292, Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Stock company Hitachi, Ltd.

Claims (11)

[Claims] 1. An alkaline surface treatment liquid for removing contaminant metals on the surface of an object to be treated, comprising at least one metal ion scavenger selected from diethylenetriaminepentaacetic acid, triethylenetetraminehexaacetic acid, and glutamic acid. And surface treatment liquid. 2. The concentration of the diethylenetriaminepentaacetic acid according to claim 1, which is 3000 times by weight or more than the concentration of iron ions eluted from the object to be treated, and is eluted from the object to be treated. A surface treatment liquid, which is 30,000 times or more in weight ratio with respect to the concentration of zinc ions. 3. The concentration of triethylenetetramine hexaacetic acid according to claim 1, which is 40,000 times by weight or more the concentration of copper ions eluted from the object to be treated, and A surface treatment liquid which is 40 times or more in weight ratio with respect to the concentration of eluted nickel ions. 4. The surface treatment liquid according to claim 1, wherein the concentration of glutamic acid is 30,000 times or more the weight ratio of the concentration of aluminum ions eluted from the object to be treated. 5. The surface treatment liquid according to claim 1, which is kept alkaline by at least one base of ammonia and tetramethylammonium hydroxide. 6. The surface treatment solution according to claim 5, further comprising 0.01 mol / liter or more of hydrogen peroxide. 7. A surface treatment method for removing a contaminating metal on the surface of an object to be treated by bringing it into contact with an alkaline surface treatment liquid, wherein the surface treatment liquid comprises diethylenetriaminepentaacetic acid, triethylenetetraminehexaacetic acid, and glutamic acid. A surface treatment method comprising at least one metal ion trapping agent. 8. The concentration of the diethylenetriaminepentaacetic acid according to claim 7, which is 3000 times or more in weight ratio with respect to the concentration of iron ions eluted from the object to be treated, and is eluted from the object to be treated. A surface treatment method, characterized in that the weight ratio of the zinc ion is 30,000 times or more. 9. The concentration of the triethylenetetramine hexaacetic acid according to claim 7, which is 40,000 times or more in weight ratio with respect to the concentration of copper ions eluted from the object to be treated, and from the object to be treated. A surface treatment method, characterized in that the concentration of nickel ions to be eluted is 40 times or more in weight ratio. 10. The surface treatment method according to claim 7, wherein the concentration of glutamic acid is 30,000 times or more in weight ratio with respect to the concentration of aluminum ions eluted from the object to be treated. 11. The surface treatment method according to claim 7, wherein the object to be treated is a semiconductor substrate.