JP4472369B2 - Method for cleaning semiconductor substrate or semiconductor element - Google Patents

Description

  The present invention relates to a non-fluorinated residue cleaning agent for copper wiring and a method for manufacturing a copper wiring semiconductor substrate or a semiconductor element using the cleaning agent. More specifically, in a process of forming a semiconductor element on a semiconductor substrate such as a silicon wafer, a process using a wiring having copper or a copper alloy, and removing a so-called polymer after dry etching or ashing treatment is performed. The present invention relates to a non-fluorinated residue cleaning agent for copper wiring to be used. Furthermore, the present invention relates to a cleaning method and a manufacturing method for a semiconductor substrate or a semiconductor element.

  In recent years, with the miniaturization of electronic devices, semiconductor elements have been increased in speed and integration, and miniaturization of wiring is required for high integration. As a result, wiring is shifting from conventional aluminum to high conductivity copper. Therefore, in the cleaning process of the copper wiring semiconductor substrate, when using the residue cleaning agent for the aluminum wiring semiconductor substrate currently used, the polymer derived from the copper wiring has insufficient cleaning power, Since the copper wiring itself is deteriorated by the cleaning agent and the film thickness is reduced, the electrical characteristics at the time of device formation are affected, and the productivity is lowered.

  In addition, the insulating film constituting the semiconductor element is also shifting from a plasma TEOS oxide film to a low dielectric constant film, a so-called Low-k film. As the Low-k film, fluorine resins such as HSQ, MSQ, organic SOG, and SiOF, SiOC, and SilK are well known. However, the Low-k film itself is not chemically stable, and the existing residue cleaning is performed. The agent is damaged, and the increase in relative dielectric constant and the decrease in film thickness are one of the causes that hinder its spread.

  Furthermore, it is known that the porous material called Ultra-low-k, which is being developed as a next-generation insulating film, is more susceptible to material damage than ever before, and the residual cleaning agent with less damage. Development is needed.

  However, there has not yet been obtained a cleaning agent for a copper wiring semiconductor substrate that can efficiently clean a polymer derived from copper wiring without damaging an insulating film such as a copper wiring, a low-k film, or an ultra-low-k film. Is the current situation.

  For example, Patent Document 1 proposes a resist stripping solution containing a phosphonic acid chelating agent, an oxidizing agent, a water-soluble fluorine compound, and an organic solvent. However, although these stripping solutions and cleaning agents are effective for aluminum wiring, they are highly damaged and difficult to use for copper wiring.

Further, Patent Document 2 proposes a semiconductor surface cleaning agent containing ozone or / and fluorine ions in addition to a phosphonic acid chelating agent. However, as in Patent Document 1, damage to copper wiring is large. It is difficult to use.
JP 2000-258924 A JP 11-340182 A

  An object of the present invention is to provide a copper wiring that can effectively remove a residue after etching or ashing in a manufacturing process of a copper wiring semiconductor substrate or a semiconductor element without damaging an insulating film such as a copper wiring or a low-k film. An object of the present invention is to provide a non-fluorine-based residue cleaning agent, a semiconductor substrate or semiconductor element cleaning method using the cleaning agent, and a semiconductor substrate or semiconductor element manufacturing method using the cleaning method.

That is, the gist of the present invention is as follows.
[1] A non-fluorine residue cleaning agent for copper wiring, containing phosphorous acid and / or organic phosphonic acid and water,
[2] A method for cleaning a semiconductor substrate or a semiconductor element, comprising a step of cleaning the semiconductor substrate or the semiconductor element using the non-fluorine-based residue cleaning agent for copper wiring according to [1], and [3] the above [2] ] The manufacturing method of a semiconductor substrate or a semiconductor element including the washing | cleaning process using the washing | cleaning method of description.

  The non-fluorine residue cleaning agent for copper wiring of the present invention has excellent releasability for copper wiring residue generated during the formation of a semiconductor substrate or semiconductor element, and can also etch a wiring metal material having a narrow wiring width. It does not occur and has excellent corrosion resistance. Therefore, by using the non-fluorine residue cleaning agent for copper wiring of the present invention, it is possible to increase the speed and integration of semiconductor elements, and to manufacture electronic parts such as LCDs, memories, and CPUs with excellent quality. The effect that it is possible is expressed.

1. Non-fluorine residue cleaning agent for copper wiring The non-fluorine residue cleaning agent for copper wiring of the present invention (hereinafter simply referred to as cleaning agent) contains phosphorous acid and / or organic phosphonic acid and water. There is one major feature, and by having such a feature, the residue after etching and ashing treatment in the manufacturing process of the copper wiring semiconductor substrate, so-called polymer, is damaged to the insulating film such as copper wiring and low-k film. Therefore, the effect that it can be removed effectively is produced.
The cleaning agent of the present invention is a non-fluorine cleaning agent, and the fluorine compound content is less than 0.1% by weight, preferably 0.05% by weight or less in the cleaning agent. .

  As phosphorous acid in the cleaning agent of the present invention, those containing the salt form in addition to the acid form can be used.

  The balance of the cleaning agent is water. Examples of water include distilled water, ion exchange water, pure water, and ultrapure water. The water content is preferably 70 to 99% by weight, more preferably 80 to 99% by weight, and still more preferably 85 to 98% in the cleaning agent from the viewpoint of workability and environmental performance such as waste liquid treatment. .5% by weight.

  Examples of the organic phosphonic acid used in the present invention include 1-hydroxyethylidene-1,1-diphosphonic acid, aminotri (methylenephosphonic acid), ethylenediaminetetra (methylenephosphonic acid), and diethylenetriaminepenta (methylenephosphonic acid). Among them, 1-hydroxyethylidene-1,1-diphosphonic acid is preferable from the viewpoint of removing etching residues or ashing residues and preventing corrosion of wirings, insulating films and the like.

  The content of phosphorous acid and / or organic phosphonic acid is preferably 0.5 to 10% by weight, and preferably 0.5 to 5% by weight in the cleaning agent from the viewpoint of copper wiring corrosion and low-k film damage. Is more preferable, and 1.0 to 5 weight is still more preferable.

  The cleaning agent of the present invention further contains a water-soluble organic solvent in order to increase the permeability of the cleaning agent to the etching residue or ashing residue and to increase the wettability of the cleaning agent to the low-k film. It is preferable.

  Examples of the water-soluble organic solvent include alcohols such as methanol, ethanol, isopropyl alcohol, benzyl alcohol, 3-methoxy-1-butanol, 4-methoxy-1-butanol, methyl 2-hydroxyisobutyrate, phenol, cresol, and the like. Phenols, sulfoxides such as dimethyl sulfoxide and diethyl sulfoxide, sulfones such as dimethyl sulfone and diethyl sulfone, N-methylformamide, N, N-dimethylformamide, N-methylacetamide, N, N-dimethylacetamide, N, Amides such as N-diethylacetamide, lactams such as N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N-hydroxymethyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, 1, 3- Imidazolidinones such as ethyl-2-imidazolidinone, lactones such as γ-butyrolactone, δ-valerolactone, multivalents such as ethylene glycol, diethylene glycol, butyl diglycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether Alcohols and alkyl ether derivatives thereof, 1,3-dioxane, 1,4-dioxane, methyl glyceryl ether, dimethyl glyceryl ether, trimethyl glyceryl ether, ethyl glyceryl ether and other ethers, methyl propionate, methyl oxalate, methyl lactate, oxalic acid Examples thereof include esters such as ethyl and ethyl lactate, ketones such as methyl isobutyl ketone, and nitriles such as acetonitrile, and one or more of them can be used.

Among these, alcohols, phenols, polyhydric alcohols and alkyl ether derivatives thereof, sulfoxides, amides, and lactams are preferable, and alcohols and alkyls of polyhydric alcohols such as butyl diglycol are more preferable. Ether derivatives, dimethyl sulfoxide, N, N-dimethylformamide, N-methyl-2-pyrrolidone and the like, more preferably alcohols or alkyl ether derivatives of polyhydric alcohols such as butyl diglycol, among which butyl Diglycol is most effective.
These water-soluble organic solvents may be used alone or in admixture of two or more.

  The content of the water-soluble organic solvent is preferably from 0.5 to 20% by weight in the cleaning agent, more preferably from 0.5 to 20% by weight from the viewpoints of permeability and wettability, and damage to the low-k film. 15% by weight, more preferably 0.5 to 10% by weight.

  If the cleaning agent of the present invention is a composition containing the components as described above, the residue after etching or ashing treatment can be effectively performed without damaging the insulating film such as copper wiring or low-k film. Can be removed. In the present invention, such an effect is expressed because phosphorous acid or organic phosphonic acid can specifically dissolve copper etching residue or ashing residue and is an aqueous cleaning agent, so that an insulating film, etc. The material damage can be suppressed.

  In addition, the cleaning agent of the present invention may contain additives such as other anticorrosives, preservatives, surfactants and antifoaming agents as long as the effects as described above are not impaired. The content of the additive is preferably 1% by weight or less in the cleaning agent of the present invention, from the viewpoint of exhibiting the performance of each additive without impairing the effect of the cleaning agent of the present invention. 5% by weight or less is more preferable.

  The concentration of each component in the cleaning agent may be either the concentration at the time of manufacturing the cleaning agent or the concentration at the time of use. Usually, a cleaning agent is produced as a concentrated liquid, and it is often used after being diluted at the time of use.

  The cleaning agent of the present invention can be prepared by mixing the above-mentioned components by a known method.

  The pH of the cleaning agent of the present invention is preferably 1 to 4 and more preferably 1 to 3 from the viewpoint of obtaining excellent residue removability, copper wiring anticorrosion, and reducing damage to the low-k film.

  In the low-k film which is a highly hydrophobic material, the cleaning agent of the present invention preferably has a surface tension of 50 mN / m or less from the viewpoint of increasing the wettability of the cleaning agent and improving the cleaning property. Preferably it is 45 mN / m or less, More preferably, it is 40 mN / m or less. The surface tension can be measured based on the method described in Examples described later.

  Moreover, the cleaning agent of the present invention is excellent in removability of etching residues derived from copper wiring. The removability of the etching residue derived from the copper wiring can be evaluated by, for example, the amount of dissolved copper dioxide (CuO) measured in the following standard test (A).

Standard test (A)
1) Put 20 g of cleaning agent in a 100 ml polyethylene container, and make it constant temperature in a thermostatic bath at 25 ° C.
2) Next, 0.1 g of copper (II) oxide powder (manufactured by Wako Pure Chemicals: 038-04345; average particle size of about 3 μm) is added and stirred sufficiently for 30 minutes.
3) 10g of the supernatant was collected in a centrifuge tube and separated using a centrifuge (made by Hitachi, trade name “himac CP56G”) under the conditions of 20000 r / min for 15 minutes, and the resulting supernatant was obtained. Is measured using an ICP emission spectrometer (trade name “JY238”, manufactured by HORIBA, Ltd.).
4) The dissolution amount of copper is determined from a calibration curve prepared with a copper aqueous solution having a known concentration.

  The amount of dissolution is preferably 1000 ppm or more, more preferably 1500 ppm or more, and still more preferably 2000 ppm or more, from the viewpoint of removing the residue at a low temperature for a short time.

  Moreover, the cleaning agent of the present invention has little damage to the copper wiring. This physical property can be evaluated by the amount of copper corrosion measured in the following standard test (B).

Standard test (B)
1) From a substrate on which a copper plating layer (thickness: about 500 nm) formed by plating on silicon is formed, a 3 cm square is cut out to prepare a test piece.
2) Pre-clean the test piece by immersing it in a 0.1 wt% hydrofluoric acid aqueous solution at room temperature for 30 seconds, rinsing with water, and drying with nitrogen blow. The test piece is measured for the strength of copper using a fluorescent X-ray measuring device (manufactured by Rigaku Corporation: “ZSX100e”) (measurement of film thickness before immersion of the cleaning agent).
4) After that, immerse the test piece in 20g of constant temperature 25 ° C cleaning agent for 30 minutes, rinse with ion-exchanged water, dry by nitrogen blow, and measure the same place as measured before immersion by X-ray fluorescence. The strength of copper is measured using an apparatus (measurement of film thickness after immersion in a cleaning agent).
5) The copper corrosion amount is calculated by calculating the film thickness before and after the immersion of the cleaning agent from a calibration curve prepared in advance using a fluorescent X-ray measuring apparatus for a copper plating film having a known film thickness.

  From the viewpoint of preventing wiring damage, the copper corrosion amount is preferably less than 10 nm, more preferably 7 nm or less, and even more preferably 5 nm or less.

  Further, the cleaning agent of the present invention has little damage to the insulating film. This physical property can be evaluated by measuring the corrosion amount of the insulating film. The amount of corrosion of the insulating film is preferably 10 nm or less, and more preferably 5 nm or less. The amount of corrosion of the insulating film can be measured by the method described in Examples described later.

  The cleaning agent of the present invention has, for example, a metal wiring such as copper and an insulating film, that is, after ashing the resist of the semiconductor substrate before and after the step of forming the metal wiring and insulating film such as copper, after light ashing, or In any case where ashing is not performed, the resist can be suitably used for peeling.

2. Semiconductor substrate or semiconductor element cleaning method The semiconductor substrate or semiconductor element cleaning method of the present invention is characterized by cleaning the semiconductor substrate or semiconductor element using the cleaning agent of the present invention. Such cleaning means is not particularly limited, and immersion peeling cleaning, rocking peeling cleaning, single wafer peeling cleaning, peeling cleaning using rotation such as a spinner, paddle cleaning, peeling by air or liquid spray. Examples thereof include cleaning, peeling cleaning using ultrasonic waves, and the like. Among them, it is suitable for immersion peeling cleaning and swing peeling cleaning.

  The washing temperature is preferably 20 to 60 ° C., more preferably 20 to 40 ° C. from the viewpoint of residue solubility, residue peelability, corrosion resistance of metal wiring material, safety, and operability, and 20 to 30 ° C. is more preferable. Or room temperature (about 25 degreeC) is still more preferable. The other cleaning conditions in the cleaning means are not particularly limited.

  In the rinsing step after washing with the cleaning agent of the present invention, water rinsing is possible. Since conventional amine-based cleaning agents such as ammonium fluoride-based cleaning agents and hydroxylamine are solvent-based release agents, they are difficult to rinse with water, and there is a risk of corrosion of wiring etc. when mixed with water. Generally, a method of rinsing with a solvent such as isopropanol has been used. However, since the cleaning agent of the present invention is water-based and has high resistance against corrosion of wiring even when water is excessive, water rinsing is possible, and an economical cleaning method is obtained with an extremely low environmental load.

  In the present invention, examples of the copper wiring include copper and a wiring made of an alloy containing 30% by weight or more of copper. The copper wiring is formed by plating, CVD, PVD, or the like.

  In addition to the copper wiring, the semiconductor substrate may include wiring such as aluminum, tungsten, titanium, tantalum, and chromium, and these metal wirings may be alloys containing different kinds of metals. Pure metal may be used, and the shape of the wiring is not limited.

The insulating film that can be used in the semiconductor substrate according to the present invention includes a plasma TEOS oxide film, a low-k film having a relative dielectric constant of 3.0 or less, and an ultra-low-k having a relative dielectric constant of 2.0 or less. Examples thereof include a low dielectric constant insulating film such as a film. Specific examples of the low-k film include hydrogen silsesquioxane-based HSQ, methyl silsesquioxane-based MSQ, fluorine resins such as organic SOG and SiOF, SiOC, aromatic polyaryl ether-based SiLK, and the like. Is mentioned. Examples of the ultra-low-k film include porous MSQ, porous SiOC, and porous SiLK. The cleaning agent of the present invention can be used even for materials that have a high residue removal effect and are susceptible to damage such as low-k films and ultra-low-k films. The damage to the low-k film due to the cleaning agent includes a decrease in film thickness, an increase (swelling), a change in relative dielectric constant, and the like. The impact is small and these changes are unlikely to occur.
The insulating film can be used as a barrier film, a stopper film, an interlayer insulating film, and the like.

  The residue that is one of the objects to be cleaned of the present invention is a residue attached to the top or side wall of a via hole or a via trench hole formed during the formation of a dual damascene structure by etching, or a copper wiring when the barrier film is etched. The upper residue, the top of the hole, or the copper-based residue attached to the side wall portion, or the titanium-based residue is shown. However, the residue is not limited as long as it is a residue generated in the manufacturing process of the electronic substrate.

  Furthermore, the cleaning object includes a resist used when forming the metal wiring such as the copper wiring. Examples of the resist include a positive type, a negative type, and a positive / negative type photoresist, and include a post-embedding material. Further, it can be suitably used when forming a via hole and a via trench hole. For example, resists described in pages 67 to 169 of “Resist Material Handbook for Semiconductor Integrated Circuits” (1996) published by Realize, Inc. can be used.

3. Manufacturing method of semiconductor substrate or semiconductor element The manufacturing method of a semiconductor substrate or semiconductor element of the present invention includes a cleaning step using the cleaning method, and specifically, using the cleaning agent, It has the process of wash | cleaning a semiconductor element.
The method for cleaning the semiconductor substrate or semiconductor element used in the manufacturing method is preferably the same as the above method. The semiconductor substrate or semiconductor element obtained by using the cleaning agent and the method for cleaning the semiconductor substrate or semiconductor element has no residual residue and extremely little corrosion of the metal wiring material. It can be used to clean semiconductor substrates or semiconductor elements with very fine wiring widths, and the damage to the low-k film is small, making it possible to reduce the size and performance of electronic components such as LCDs, memories, and CPUs. It can be suitably used for production. Furthermore, it can be suitably used for manufacturing a semiconductor substrate or a semiconductor element using a porous material that is easily damaged such as Ultra-low-k, which is being developed as a next-generation insulating film.

Examples 1-5, Comparative Examples 1-4 (Example 1 is a reference example)
1. Preparation of cleaning agent A cleaning agent having the composition shown in Table 1 (the numerical value is% by weight) was prepared, and the pH was measured. Further, the physical properties of the obtained cleaning agent were measured and evaluated according to the following methods. These results are shown in Table 2.

2. Measurement of surface tension Measurement of surface tension was performed using an automatic surface tension meter “CBVP-Z type” (Kyowa Interface Science Co., Ltd.).

3. Measurement of dissolution amount of copper dioxide (CuO) and corrosion amount of copper plating film The dissolution amount of copper dioxide was measured by the standard test (A), and the corrosion amount of copper plating film was measured by the standard test (B). .
The calibration curve in the standard test (A) was prepared by ICP measurement using standard solutions with known Cu contents of about 0, 2, and 20 ppm. The cleaning agent was measured by diluting so that the measured value was within the calibration curve range of 0 to 20 ppm.
In addition, the calibration curve in the standard test (B) was prepared by measuring the fluorescent X-ray intensity using standard samples with known copper plating film thicknesses of about 0, 250 and 500 nm.

4). Measurement of corrosion amount of insulating film A wafer (silicon thickness: 0.7 mm) in which porous SiOC (relative dielectric constant 2.2) is uniformly formed on silicon as a low dielectric constant insulating film with a thickness of 500 nm is 1 cm. A sample was cut at the corner. After accurately measuring the film thickness of this insulating film sample using an optical interference film thickness meter (Dainippon Screen Mfg. Co., Ltd., optical interference film thickness measuring device “Lambda Ace VM-1000”), It was immersed in 30 g of cleaning agent at 25 ° C. for 30 minutes. Then, the amount of corrosion was calculated | required by measuring a film thickness again and calculating the film thickness difference before and behind immersion. The porous SiLK (relative dielectric constant: 2.2) was also measured by the same method.

In the table,
HEDP is 1-hydroxyethylidene-1,1-diphosphonic acid,
BDG is butyl diglycol,
DMSO is dimethyl sulfoxide,
DMF represents dimethylformamide, respectively.

  Next, the wafer was cleaned using the obtained cleaning agent, and its copper wiring residue peelability, copper wiring corrosiveness and insulating film corrosiveness were measured and evaluated according to the following procedures. These results are shown in Table 3.

5). Wafer for evaluation A copper, silicon nitride film, a low dielectric constant insulating film {(porous SiOC (relative dielectric constant 2.2)}) and a silicon nitride film are formed in this order on a silicon wafer, and a polyvinylphenol-based positive electrode is formed thereon. A sample wafer was prepared by applying a resist resist composition and drying to form a resist film, followed by lithography with a hole pattern transferred, and using this as a mask, a silicon nitride film without a resist film, a low dielectric constant The insulating film and silicon nitride film were removed by dry etching with a fluorocarbon (CF) or oxygen etching gas, and finally the resist was removed by ashing with oxygen plasma to form a hole pattern. (Evaluation wafer 1) Also, a system using porous SiLK (relative dielectric constant 2.2) as a low dielectric constant insulating film is processed in the same manner by using the same method. It was formed over emissions (evaluation wafer 2).
By observing these wafers with SEM (scanning electron microscope) (50000 times to 100000 times), it was confirmed that residues after etching and ashing, that is, polymers were formed inside the holes.
These wafers were cut into 1 cm squares and used for cleaning tests.

6). Evaluation of Detergency (1) Peeling Method: The above evaluation wafers 1 and 2 were immersed in 30 ml of cleaning agent at 25 ° C. for 3 minutes and cleaned.
(2) Rinsing and drying method: The evaluation wafers 1 and 2 were immersed in 30 ml of ultrapure water at 25 ° C. for 1 minute, and this was repeated twice, followed by drying by nitrogen blowing.
(3) Evaluation method: After the rinsed evaluation wafers 1 and 2 have been rinsed, they are observed using a FE-SEM (scanning electron microscope) at a magnification of 50000 times to 100000 times to remove copper wiring residues. In addition, the corrosivity of the copper wiring was evaluated in the following three stages.

(Removability of copper wiring residue)
○: No residue is confirmed.
Δ: A part of the residue remains.
X: Most residue remains.

(Corrosion of copper wiring)
○: No corrosion of copper wiring is confirmed.
Δ: Some corrosion of copper wiring occurred.
X: Corrosion of copper wiring is greatly generated.

(Insulating film corrosiveness)
○: No insulation wire corrosion was confirmed.
Δ: Some corrosion of the insulating film has occurred.
X: Corrosion of the insulating film is greatly generated.

  In addition, it is assumed that the acceptable product is “◯” for the removal of copper wiring residue, the corrosivity of copper wiring, and the corrosivity of the insulating film.

  From the results in Table 3, the cleaning agents obtained in Examples 1 to 5 are any of residue removal, copper wiring corrosion prevention, and insulation film corrosion prevention compared to those obtained in Comparative Examples 1 to 4. It turns out that it is also excellent.

  The non-fluorine residue cleaning agent for copper wiring of the present invention can be suitably used for the production of electronic components such as high performance LCDs, memories, and CPUs.

Claims (4)

After ashing treatment of a semiconductor substrate or a semiconductor element using a non-fluorine-based residual cleaning agent for copper wiring having a pH of 1 to 4, comprising phosphorous acid and / or organic phosphonic acid, water and a water-soluble organic solvent A method for cleaning a semiconductor substrate or a semiconductor element having a low-k film, comprising a step of cleaning a residue . In the fluorine-free residue cleaners for copper wiring, the content of phosphorous acid and / or an organic phosphonic acid is 0.5 to 10 wt%, claim 1 Symbol placement content of water is 70 to 99 wt% Cleaning method . The cleaning method according to claim 1 or 2 , wherein the surface tension of the non-fluorine residue cleaning agent for copper wiring is 50 mN / m or less. Copper wiring fluorine-free residue cleaners are the dissolution of the second copper oxide in the standard test (A) is 1000ppm or higher, and claim 1-3 corrosion amount of copper in the standard test (B) is less than 10nm Any of the washing | cleaning methods .