JP4586628B2 - Semiconductor substrate surface treatment agent and treatment method - Google Patents

Description

  The present invention relates to a processing agent and a processing method for a surface of a semiconductor substrate, and more particularly to an etching agent and an etching method for a semiconductor substrate.

A semiconductor wafer is generally manufactured by the following steps.
(1) Slicing step: A step of slicing a single crystal ingot manufactured by FZ method, CZ method or the like to obtain a thin disc-shaped wafer (ascut wafer).
(2) Beveling process: A process of chamfering the outer periphery of an as-cut wafer.
(3) Lapping process: In order to reduce the processing strain layer on the wafer surface and reduce variations and unevenness of the wafer thickness, the chamfered wafer was polished on both sides with loose abrasive grains to make the thickness uniform. The process of obtaining a wafer (wrapped wafer).
(4) Etching process: The processing strain layer remaining on the wrapped wafer is removed by a chemical method (chemical etching), and at the same time, the abrasive, metal impurities, particles, etc. adhering to the wafer surface are removed to produce a clean wafer (etched). A process for obtaining a wafer.
(5) Heat treatment step: a step of stabilizing resistance by eliminating the oxidized donor doped in the crystal by low-temperature heat treatment.
(6) Polishing process: A process of obtaining a mirror wafer (polished wafer) having a highly flat mirror surface by polishing the surface of the etched wafer with extremely fine abrasive grains.
(7) Cleaning process: A process of cleaning a polished wafer to remove abrasives, metal impurities, particles, etc. adhering to the wafer surface to obtain a cleaner wafer.

There are two types of chemical etching in the above etching process: acid etching performed by immersing a semiconductor wafer in an acidic solution and alkali etching performed by immersing in an alkaline solution.
However, acid etching is difficult to etch the wafer uniformly due to the high etching rate, there is a problem that the flatness of the wafer is deteriorated, a harmful by-product such as NOx is generated, etc. Recently, alkaline etching is widely used, which enables uniform etching, does not deteriorate the flatness of the wafer, and causes less harmful by-products.

  By the way, in the alkali etching of the semiconductor wafer described above, commercially available alkaline solutions for industrial or electronic industries (for example, sodium hydroxide solution, potassium hydroxide solution, etc.) are used, but industrial alkaline solutions are several ppm. Contains high concentration metal impurities (eg nickel, chromium, iron, copper, etc.) of about tens of ppm, and even alkaline solutions for the electronics industry contain tens of ppb to several ppm of metal impurities. Yes.

  When alkali etching is performed using an alkali solution as described above, metal impurities in the solution adhere to the wafer, and metal ions of the metal impurities diffuse into the wafer, degrading the quality of the wafer, or the wafer There is a problem that the characteristics of the semiconductor device formed by the method are significantly deteriorated.

  In order to solve such a problem, a method in which metal silicon and / or a silicon compound is dissolved in an alkaline solution in advance or hydrogen gas is dissolved to deionize metal ions in the alkaline solution (Patent Document 1), ions A method of removing metal ions in an alkaline solution using an exchange resin (Patent Document 1), a reducing agent having a base oxidation potential, such as dithionite, having a base oxidation potential compared to the reversible potential of the metal ion. A method of deionizing metal ions in an alkali solution by performing the above (Patent Document 2) has been proposed. However, these methods also deionize or remove metal ions derived from metal impurities present in an alkali solution. Was insufficient.

Furthermore, in order to solve the above problems, a method has been proposed in which metal ions in an alkaline solution are reduced by immersing stainless steel in the alkaline solution for 10 hours or more (Patent Document 3).
However, in this method, the alkaline solution and the stainless steel need to be brought into contact with each other for a long time of 10 hours or more under a high temperature condition, and the stainless steel needs to be drawn out from the alkaline solution. .

Japanese Patent Laid-Open No. 9-129624 Japanese Patent Laid-Open No. 10-310883 JP 2001-250807 A

  The present invention provides a semiconductor substrate surface treating agent and a semiconductor substrate surface treating method that can suppress contamination of metal impurities on the semiconductor substrate, and in particular, a semiconductor substrate etching agent and etching method.

The present invention has been made for the purpose of solving the above-described problems, and has the following configuration.
(1) A semiconductor substrate surface treating agent comprising a silicon-based material, comprising diethylenetriaminepentaacetic acid or an inorganic salt thereof and 20% (W / W) or more of sodium hydroxide .
(2) An etching agent for a semiconductor substrate made of a silicon-based material, comprising diethylenetriaminepentaacetic acid or an inorganic salt thereof and 20% (W / W) or more of sodium hydroxide .
(3) A method for treating a surface of a semiconductor substrate, comprising treating a semiconductor substrate made of a silicon-based material with the treatment agent described in (1) above.
(4) A method for etching a semiconductor substrate, comprising etching a semiconductor substrate made of a silicon-based material with the etching agent according to (2).

  That is, as a result of intensive studies to achieve the above object, the present inventors comprise an aminopolycarboxylic acid chelating agent or an inorganic salt thereof and 20% (W / W) or more of an alkali metal hydroxide. When a semiconductor substrate is processed using a solution, contamination of the semiconductor substrate by metal impurities present in the alkaline solution (adsorption of the metal impurities to the surface of the semiconductor substrate) can be effectively suppressed. It is found that if a semiconductor substrate is etched using a metal substrate, contamination of the semiconductor substrate, which is an object to be etched, due to metal impurities can be reduced, and the solution can be prepared easily and in a short time, thereby completing the present invention. It came to.

  According to the present invention, contamination of a semiconductor substrate by metal impurities (adsorption of the metal impurities to the surface of the semiconductor substrate) can be effectively suppressed during processing of the surface of the semiconductor substrate, particularly etching of the semiconductor substrate.

In the present invention, “treatment” refers to bringing the semiconductor substrate surface treating agent of the present invention into contact with the semiconductor substrate. More specifically, it is a process performed in a general process of manufacturing a semiconductor wafer as described above, such as a slicing process, a beveling process, a lapping process, an etching process, a heat treatment process, a polishing process, and a cleaning process. It is not limited to these.
That is, the semiconductor substrate surface treatment agent of the present invention is a treatment agent that is brought into contact with the semiconductor substrate in the “treatment” as described above (for example, slicing process, beveling process, lapping process, etching process, heat treatment process, polishing process, cleaning process, etc. Treatment agent used in Specifically, it can be used as an abrasive used in a lapping process or a polishing process, an etchant used in an etching process, a cleaning agent used in a cleaning process or the whole process, and the like.
Among these, the semiconductor substrate surface treating agent of the present invention is particularly useful as an etching agent.

The aminopolycarboxylic acid chelating agent used in the present invention is not particularly limited as long as it is usually used in this field. For example, alkyliminopolycarboxylic acid optionally having a hydroxy group [hydroxyethyliminodiacetic acid (HIDA ), Iminodiacetic acid (IDA), etc.], nitrilopolycarboxylic acid [nitrilotriacetic acid (NTA), nitrilotripropionic acid (NTP), etc.], monoalkylene polyamine polycarboxylic acid [ethylenediaminetetraacetic acid (EDTA), ethylenediaminediacetic acid (EDDA), ethylenediaminedipropionic acid dihydrochloride (EDDP), hydroxyethylethylenediaminetriacetic acid (EDTA-OH), 1,6-hexamethylenediamine-N, N, N ', N'-tetraacetic acid (HDTA), N, N-bis (2-hydroxybenzyl) ethylenediamine-N, N-diacetic acid (HBED) etc.], polyalkylene polyamine polycarboxylic acid [ Ethylenetriamine-N, N, N ', N'',N''-pentaacetic acid (DTPA), triethylenetetramine hexaacetic acid (TTHA), etc., polyaminoalkanepolycarboxylic acid [diaminopropanetetraacetic acid (Methyl-EDTA) , Trans-1,2-diaminocyclohexane-N, N, N ', N'-tetraacetic acid (CyDTA) etc.], polyaminoalkanol polycarboxylic acid [diaminopropanol tetraacetic acid (DPTA-OH) etc.], hydroxyalkyl ether polyamine Examples thereof include nitrogen-containing polycarboxylic acids having 1 to 4 nitrogen atoms and 2 to 6 carboxyl groups in a molecule such as polycarboxylic acid [glycol ether diamine tetraacetic acid (GEDTA) and the like].
Examples of these inorganic salts include alkali metal salts (sodium salts, potassium salts, lithium salts, cesium salts, etc.), alkaline earth metal salts (calcium salts, magnesium salts), and the like. preferable.
Among these, monoalkylene polyamine carboxylic acid, polyalkylene polyamine carboxylic acid or an inorganic salt thereof is preferable, and polyalkylene polyamine carboxylic acid or an inorganic salt thereof is particularly preferable. Specifically, EDTA, DTPA or an inorganic salt thereof is preferable, and DTPA or an inorganic salt thereof is particularly preferable.
These aminopolycarboxylic acid-based chelating agents or inorganic salts thereof may be used alone or in appropriate combination of two or more.
In addition, the amount of aminopolycarboxylic acid chelating agent or its inorganic salt used cannot be generally described because it varies depending on the type of chelating agent or the amount of alkali metal hydroxide used together, but the lower limit is usually 50 ppm or more, for example. The upper limit is usually not more than the saturation amount, preferably not more than 10,000 ppm, more preferably not more than 5000 ppm.

Examples of the alkali metal hydroxide used in the present invention include sodium hydroxide and potassium hydroxide.
These alkali metal hydroxides may be used alone or in appropriate combination of two or more.
In addition, the amount of alkali metal hydroxide used varies depending on the type of alkali metal hydroxide and the like, and thus cannot be generally stated. For example, the lower limit is usually 20 (W / W)% or more, preferably 40% (W / W W) or more, more preferably 45% (W / W) or more, and the upper limit is usually 60% (W / W) or less, preferably 55% (W / W) or less, more preferably 52 (W / W) )% Or less.

  The semiconductor substrate surface treating agent of the present invention comprises the aminopolycarboxylic acid chelating agent as described above or an inorganic salt thereof and a high concentration alkali metal oxide of 20% (W / W) or more.

The semiconductor substrate surface treating agent of the present invention is usually in an aqueous solution, and the aminopolycarboxylic acid chelating agent or inorganic salt thereof and a high concentration alkali metal oxide are added to water so that the concentration range is as described above. It is prepared by mixing and dissolving.
As a method for dissolving the aminopolycarboxylic acid-based chelating agent or its inorganic salt and alkali metal oxide in water, any method can be used as long as these components can be finally mixed and dissolved in water. Method of adding dissolved aminopolycarboxylic acid chelating agent or inorganic salt or / and alkali metal oxide, or adding aminopolycarboxylic acid chelating agent or inorganic salt and alkali metal oxide directly to water and dissolving And a stirring method. That is, each component may be sequentially added and mixed in water in an appropriate order, or all components may be added and then dissolved in water.
The treatment agent according to the present invention thus prepared is preferably filtered before use. The water used here may be any water purified by distillation, ion exchange treatment, or the like, but so-called ultrapure water used in this field is more preferable.

  The treating agent in the present invention is strongly alkaline and usually has a pH of 13 or higher.

  Further, in the treating agent according to the present invention, additives usually used in this field can be used in addition to the aminopolycarboxylic acid chelating agent or the inorganic salt and alkali metal oxide as described above. Examples of such additives include surfactants, oxidizing agents (hydrogen peroxide, ozone, oxygen, etc.), reducing agents (hydrazine, etc.), silicon, dissolved gases (hydrogen, argon, nitrogen, etc.), abrasive grains, etc. Solids such as silicon dioxide (colloidal silica, fumed silica, precipitated silica, etc.), alumina, ceria, etc.

In addition to the aminopolycarboxylic acid chelating agent or its inorganic salt and alkali metal oxide, the treatment agent of the present invention is a surfactant, oxidizing agent, reducing agent, silicon, dissolved gas, and abrasive-like solids. One additive selected from the group consisting of a surfactant, an oxidizing agent, a reducing agent, silicon, and abrasive-like solids among the above-mentioned additives. Are preferably included, and more preferably include one kind of additive selected from surfactants, reducing agents, silicon and abrasive-like solids.
. In particular, when the treating agent of the present invention is used as an etching agent, the etching agent includes one kind of additive selected from the above-mentioned surfactant, oxidizing agent, reducing agent, silicon and dissolved gas. Among these additives, those containing one kind of additive selected from a surfactant, an oxidizing agent, a reducing agent and silicon are preferable, and one kind selected from a surfactant, a reducing agent and silicon. More preferred are those containing the above additives, and particularly preferred are those containing a reducing agent and / or silicon.
As such a reducing agent, for example, a reducing agent having a base oxidation potential that is lower than the reversible potential of metal ions such as iron, nickel, copper, etc., and having a very low oxidation potential [eg, hypophosphite, dithione, etc. Acid salts, borohydride compounds, aldehydes, hydrazine compounds, etc.]. Further, the amount of such a reducing agent used varies depending on the type of the reducing agent and cannot be generally specified. For example, in the case of dithionite, it is 2.5 g / L or more.
In addition, examples of the origin (material used) of silicon include metal silicon [polycrystalline or single crystal silicon] and silicon compounds [for example, silica, silicate glass, etc.], and the amount of silicon used is 2 g / L or more. is there.

In the treatment method of the present invention, the treatment agent of the present invention as described above may be brought into contact with the semiconductor substrate, and the surface of the semiconductor substrate may be treated with the treatment agent of the present invention.
The method for treating the surface of the semiconductor substrate with the treatment agent of the present invention may be any method known per se usually performed in this field. Specifically, the semiconductor substrate is simply immersed in the treatment agent of the present invention. The surface of the semiconductor substrate and the processing agent of the present invention are brought into contact with each other by a method such as dip treatment or single wafer processing in which the processing agent of the present invention is sprinkled on the semiconductor substrate in the form of a shower, and in the presence of the processing agent of the present invention, for example, slicing Examples include a process, a beveling process, a lapping process, an etching process, a heat treatment process, a polishing process, and a cleaning process.
As the temperature conditions for the treatment, the lower limit is usually room temperature or higher, preferably 60 degrees or higher, more preferably 65 degrees or higher, and the upper limit is usually 100 ° C. or lower, preferably 90 ° C. or lower, more preferably 85 ° C. It is as follows. In other words, the temperature of the treatment agent of the present invention may be in the temperature range as described above, and this may be brought into contact with the semiconductor substrate.

  Hereinafter, a case where a semiconductor substrate is etched using the treatment agent of the present invention, that is, a case where a semiconductor substrate is etched using the etching agent of the present invention will be described in detail.

  The etching method of the present invention is known per se except that the semiconductor substrate is etched using the treating agent according to the present invention containing an aminopolycarboxylic acid chelating agent or an inorganic salt thereof and an alkali metal oxide as an etching agent. This may be performed according to a method such as a dip method or a spray etch method.

More specifically, for example, (1) a method of immersing a semiconductor substrate in an etching agent, (2) a method of stirring the solution by mechanical means in a state where the semiconductor substrate is immersed in an etching agent, and (3) a semiconductor substrate. And a method in which the solution is vibrated and stirred with an ultrasonic wave or the like while being immersed in an etching agent, and (4) a method in which an etching agent is sprayed onto a semiconductor substrate.
In the method of the present invention, when performing etching as described above, the semiconductor may be swung as necessary.
In the method of the present invention, the etching method is not particularly limited, and for example, a batch method, a single wafer method, or the like can be used.

  As the temperature conditions for etching, the lower limit is usually room temperature or higher, preferably 60 degrees or higher, more preferably 65 degrees or higher, and the upper limit is usually 100 ° C. or lower, preferably 90 ° C. or lower, more preferably 85 ° C. It is as follows. In other words, the temperature of the etching agent of the present invention may be in the temperature range as described above, and this may be brought into contact with the semiconductor substrate.

The semiconductor substrate to which the treatment agent and the treatment method of the present invention are applied may be any substrate that is usually used in this field, and depends on the purpose of use of the treatment agent (treatment method). Examples thereof include semiconductor substrates made of silicon-based materials such as crystalline silicon, polysilicon, silicon oxide film, and silicon nitride film, and compound semiconductors such as gallium arsenide, gallium-phosphorus, and indium-phosphorus.
Especially, the processing agent and processing method of this invention are used suitably for the semiconductor substrate which consists of a silicon-type material.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

Example 1
(1) Preparation of etching agent
To a 48% NaOH (“CLEARCUT-S” manufactured by Tsurumi Soda Co., Ltd.) solution or a 48% KOH (“CLEARCUT-P” manufactured by Tsurumi Soda Co., Ltd.) solution, 1000 ppm of the predetermined chelating agent shown in Table 1 was added. In addition, an iron standard solution (manufactured by Wako Pure Chemical Industries, Ltd., containing 1000 ppm Fe), a nickel standard solution (manufactured by Wako Pure Chemical Industries, Ltd., containing 1000 ppm Ni), and a copper standard solution [Wako Pure Chemical Industries, Ltd. ), 1000 ppm Cu contained] was added so that the amount of metal in the etching agent was 15 ppb.
In the table, the abbreviations of chelating agents are as follows.
・ EDTA: Ethylenediaminetetraacetic acid ・ DTPA: Diethylenetriamine-N, N, N ', N'',N''-pentaacetic acid ・ EDTPO: Ethylenediaminetetrakis (methylenephosphonic acid)
・ DEPPO: Diethylenetriaminepentakis (methylenephosphonic acid)
(2) Etching The etching agent obtained in (1) above is pre-heated at 85 ° C. for a predetermined time, and then a 6-inch wafer is immersed in each etching agent heated to 85 ° C. for 5 minutes for etching treatment (85 ° C. ) The wafer was taken out and washed with running water, followed by pure water washing and spin drying. In Table 1, “Etching agent preheating time at 85 ° C.”, “0 hour” means that the etching treatment was performed immediately after heating the etching agent to 85 ° C. "Means that the etching treatment was performed after heating the etching agent at 85 ° C for 24 hours.
(3) Results The amount of metal on the etched wafer surface obtained in the above (2) was measured with a total reflection fluorescent X-ray apparatus (“TREX610” manufactured by Technos).
The results are shown in Table 1.

As is clear from Table 1, EDTA and DTPA, which are aminopolycarboxylic acid chelating agents, have a high effect of suppressing the adsorption of metal to the semiconductor substrate surface, whereas EDTPO and DEPPO, which are phosphonic acid chelating agents, adsorb. It can be seen that the suppression effect is low.
In addition, among the aminopolycarboxylic acid-based chelating agents, it can be seen that DTPA does not lower its adsorption suppressing effect even after heat treatment at 85 ° C. for 24 hours. It was unexpected that such a chelating agent retained its chelating ability (adsorption suppression effect) even after being treated for a long time at a high temperature in a highly concentrated alkaline solution.

Example 2
(1) Preparation of Etching Agent The etching agent was prepared in the same manner as in Example 1 except that a predetermined amount of DTPA shown in Table 2 was used as a chelating agent.
(2) Etching Performed in the same manner as in Example 1.
(3) Results In the same manner as in Example 1, the amount of metal on the etched wafer surface was measured.
The results are shown in Table 2.

  As can be seen from Table 2, DTPA has an effect of suppressing the adsorption to metals only by adding it, but the effect of suppressing the adsorption to metals is good when the concentration in the etching agent is 50 ppm or more, and more particularly when the concentration is 1000 ppm or more. It turns out that becomes high.

Example 3
(1) Preparation of Etching Agent 1000 ppm of DTPA was added to NaOH (“CLEARCUT-S” manufactured by Tsurumi Soda Co., Ltd.) having a predetermined concentration shown in Table 3.
(2) Etching After heating the etching agent obtained in the above (1) to various temperatures of 85 ° C., a wafer piece (2 cm × 2 cm) was immersed therein for 5 minutes for etching treatment (85 ° C.).
(3) Results The roughness of the wafer piece surface obtained in the above (2) was measured with an atomic force microscope (“Nanopics 2100” manufactured by SII).
The results are shown in Table 3.

  As is clear from Table 3, it can be seen that sodium hydroxide has a rough surface on the semiconductor substrate at a low concentration, and the amount used is preferably 20% (W / W) or more as the concentration in the etching agent.

If a semiconductor substrate is processed using the processing agent according to the present invention, contamination of the semiconductor substrate by metal impurities present in the alkaline solution (adsorption of the metal impurities to the surface of the semiconductor substrate) can be effectively suppressed. . In particular, if the semiconductor substrate is etched using the etching agent according to the present invention, it is possible to reduce contamination of the semiconductor substrate, which is an object to be etched, due to metal impurities in the etching process.

Claims (12)

A semiconductor substrate surface treatment agent comprising a silicon-based material, comprising diethylenetriaminepentaacetic acid or an inorganic salt thereof and 20% (W / W) or more of sodium hydroxide . It is intended to include diethylenetriaminepentaacetic acid or an inorganic salt or 50 ppm, the treatment agent according to claim 1. pH is 13 or more, the processing agent according to claim 1. An etching agent for a semiconductor substrate made of a silicon-based material, comprising diethylenetriaminepentaacetic acid or an inorganic salt thereof and 20% (W / W) or more of sodium hydroxide . The etching agent according to claim 4 , comprising 50 ppm or more of diethylenetriaminepentaacetic acid or an inorganic salt thereof. The etching agent of Claim 4 whose pH is 13 or more. The etching agent of Claim 4 for removing the process distortion layer on a board | substrate. A method for treating a surface of a semiconductor substrate, comprising treating a semiconductor substrate made of a silicon-based material with the treatment agent according to any one of claims 1 to 3 . The processing method of Claim 8 whose temperature of a processing agent is 60-100 degreeC. A method of etching a semiconductor substrate, comprising etching a semiconductor substrate made of a silicon-based material with the etching agent according to claim 4 . The etching method of Claim 10 whose temperature of an etching agent is 60-100 degreeC. The etching method according to claim 10, wherein the processing strain layer on the substrate is removed.