CN102403192A - Cleaning method for substrates - Google Patents

Abstract

The invention provides a cleaning method for substrates, which includes steps of providing a substrate with a bonding pad, cleaning the substrate by means of DSP (dilute sulfuric peroxide) solution, and cleaning the substrate in a cleaning chamber by means of carbon dioxide and deionized water. Using the carbon dioxide and deionized water to clean the substrate can protect the bonding pad from being corroded by fluoride ions to the maximum extent, and meanwhile, contamination of polymers or other particles generated in etching can be removed more effectively, so that reliability of products can be improved.

Description

Substrate cleaning method

Technical field

The present invention relates to integrated circuit fabrication process, particularly a kind of substrate cleaning method.

Background technology

Along with the integrated circuit minimum dimension constantly reduces, the improving constantly and the expansion of silicon monocrystalline substrate size of integrated level; The modern semiconductors manufacturing industry needs the feature pattern of massive duplication sub-micron strictly, and plasma etching is unique technology that can satisfy this requirement cost-effectively.Plasma etching is accomplished through the plasma etching reative cell, and said plasma etching reative cell is mainly by a vacuum cavity and vacuum system, and a gas system is used to provide accurate gaseous species and flow, and radio-frequency power supply and adjusting match circuit system thereof form.The principle of plasma etching may be summarized to be following step: under low pressure; Reacting gas is under the exciting of radio-frequency power; Produce ionization and form plasma, plasma is made up of charged electronics and ion, and the gas in the reaction cavity is under the bump of electronics; Except being transformed into ion, can also absorbing energy and form a large amount of active groups; Active reactive group forms chemical reaction and forms volatile reaction product with the material surface that is etched; Reaction product breaks away from the material surface that is etched, and is extracted out cavity by vacuum system, thereby accomplishes the etching to wafer.

In the manufacturing process of semiconductor device, often need to use plasma etching industrial.For example, in the process that forms aluminum pad, need carry out the several times of plasma etching process.Detailed, seeing also Figure 1A～1D, it is the generalized section of each step corresponding construction of aluminum pad formation method.

With reference to Figure 1A, onSemiconductor substrate 11, form metal layer attop 12, said metal layer at top is a copper metal layer.Be formed with semiconductor device structure on theSemiconductor substrate 11, for different processes, the structure ofSemiconductor substrate 11 is different, and for simplifying, this sentences blank Semiconductor substrate and representes.

With reference to Figure 1B; On metal layer attop 12, form the passivation layer with opening, said passivation layer comprisescover layer 13 andovercoat 14, wherein; The material ofcover layer 13 includes but not limited to silicon nitride, and the material ofovercoat 14 includes but not limited to the combination of silicon nitride and silica.

With reference to Fig. 1 C,form barrier layer 15, it includes but not limited to silicon nitride.

With reference to Fig. 1 D, deposition of aluminum onbarrier layer 15, process photoetching and dry etching are to formaluminum pad 16.

Wherein, the forming process with passivation layer of opening specifically comprises: on the metal layer attop 12 successively behindsedimentary cover 13 and theovercoat 14, and rotary coating photoresistance onovercoat 14; Adopt existing photoetching and developing technique then; On overcoat 14, form patterns of openings, utilize photoresistance to do afterwards and shelter, utilize the plasma etching industrial etching not by behind the overcoat 14 of photoresistance covering; Etching then forms the passivation layer with opening not by thecover layer 13 of photoresistance covering again.Deposition of aluminum onbarrier layer 15, process photoetching and dry etching are to formaluminum pad 16.

Can be learnt by foregoing description, in the photoetching and dry etching process of aluminum pad, can use plasma etching industrial, common used etching reaction gas can comprise CF in this plasma etching technology₄, CF₈, C₅F₈, C₄F₆, CHF₃A kind of in the gas, they and meetings such as photoresist, etching product produce certain combining, and form polymer, and this polymer can stop the etching of oppose side wall, strengthens the directivity of etching, thereby realizes the excellent control to the aperture size of etching structure.But these polymer must be removed after etching is accomplished, otherwise will become particle and the contamination sources that increases surface defects of products density, damage device function, influence the rate of finished products and the reliability of device.

The conventional way of removing this polymer pollution in the industry is to utilize DSP (Dilute SulfuricPeroxide; The sulfuric acid mixing hydrogen peroxide solution of dilution) solution cleans substrate surface, and said DSP solution is the mixed solution of deionization deionized water, hydrogen peroxide, sulfuric acid and hydrofluoric acid.Yet, also introduced fluorine ion when polluting through the caused polymer of said DSP solution removal plasma etching, this fluorine ion can cause corrosion to aluminum pad.Specifically, fluorine ion and the aluminium generation reactions that exists with ionic forms:

Reaction 1:6F^-+ Al³⁺→ (AlF₆)^3-,

Because the change of effects of ion number, this reaction will promote the carrying out of following three reactions simultaneously:

Reaction 2:3H₂+ N₂+ 2H₂O → 2OH^-+ 2NH₄⁺

Reaction 3: (AlF₆)^3-+ 3OH^-→ Al (OH)₃+ 6F^-

Reaction 4: (AlF₆)^3-+ 3NH₄⁺→ (AlF₆) (NH₄)₃,

And because reaction 3,4 all will consume (AlF₆)^3-, reaction 3,4 will promote the carrying out of reaction 1 again, constitute a chain reaction thus, constantly consume aluminium ion, finally cause the heavy corrosion of aluminum pad.

Can cause aluminum pad to come off during the seriously corroded of aluminum pad, reduce product reliability.In order to solve when using DSP solution removal polymer to pollute, introduce fluorine ion aluminum pad is caused the problem of corrosion, at present, common way is when cleaning substrate surface through DSP solution, feeds CO₂Gas, CO₂The feeding of gas will slow down the corrosion of fluorine ion to aluminum pad.Entire reaction course is following:

Reaction 1:6F^-+ Al³⁺→ (AlF₆)^3-

Reaction 2:3H₂+ N₂+ 2H₂O → 2OH^-+ 2NH₄⁺

Reaction 3 ': H₂O+CO₂→ 2H⁺+ CO₃^2-

Reaction 3 ": H⁺+ OH^-→ H₂O;

Reaction 4: (AlF₆)^3-+ 3NH₄⁺→ (AlF₆) (NH₄)₃,

CO₂The feeding of gas has interrupted original reaction 3, new reaction 3 ' and 3 " do not promote to react 1 carrying out, thereby reduced the corrosion of fluorine ion to aluminum pad.

But, when cleaning, feed CO through DSP solution₂There is such problem in gas, promptly feeds CO₂Behind the gas, because CO₂Gas not free with DSP solution in deionized water fully react, cause producing enough H⁺To remove OH^-Thereby, interrupt original reaction 3, reduce (AlF₆)^3-Loss.Promptly through existing substrate cleaning method, can not prevent the aluminum pad corrosion that fluorine ion causes substantially, certainly, also there is same problem during as the pad material in other metal like copper, tin.

Summary of the invention

The object of the present invention is to provide a kind of substrate cleaning method, can not prevent the pad corrosion that fluorine ion causes effectively, and can not effectively remove the problem of the pollutant of substrate surface in order to the solution prior art.

For solving the problems of the technologies described above, the present invention provides a kind of substrate cleaning method, comprising: the substrate that is formed with pad is provided; Utilize DSP solution to clean said substrate; Utilize carbon dioxide and deionized water to clean said substrate in wash chamber.

Optional, said pad is an aluminum pad.

Optional, the time of utilizing DSP solution to clean said substrate is more than or equal to 1 minute.

Optional, the time of utilizing carbon dioxide and the said substrate of washed with de-ionized water is more than or equal to 1 minute.

Optionally, utilize carbon dioxide and deionized water before wash chamber is cleaned said substrate, earlier said carbon dioxide and deionized water are mixed.

Optional, said carbon dioxide and deionized water at room temperature mix.

Optional, utilize carbon dioxide and deionized water when wash chamber is cleaned said substrate, said carbon dioxide feeds said wash chamber to clean said substrate through different pipelines respectively with deionized water.

Optional, said carbon dioxide and deionized water feed said wash chamber simultaneously.

Optional, it is long that the time ratio that feeds said deionized water feeds time of said carbon dioxide.

Optional, through the mode of high-pressure injection, said carbon dioxide and deionized water are sprayed onto said substrate surface to clean said substrate.

Optional, said high-pressure injection is under inert gas environment, to carry out.

Optional, said high-pressure injection is under nitrogen environment, to carry out.

Compared with prior art, substrate cleaning method provided by the invention has the following advantages:

The present invention utilizes the cleaning of DSP solution to be formed with after the substrate of aluminum pad, utilizes the said substrate of carbon dioxide and washed with de-ionized water again, can fully react with deionized water to guarantee carbon dioxide, produces enough H⁺To remove OH^-Thereby, interrupt OH^-With the reaction of metal fluoride ion, reduce the loss of metal fluoride thus, farthest prevent the aluminum pad corrosion that fluorine ion causes.

In addition, utilize DSP solution to clean after the substrate, again through this substrate of washed with de-ionized water; Deionized water can be taken away the particle of substrate surface; The polymer that produces in the more effective removal etching or other particulate pollutant can improve cleaning efficiency, thereby improve reliability of products.

Description of drawings

Figure 1A～1D is the generalized section of each step corresponding construction of aluminum pad formation method;

Fig. 2 is the flow chart of substrate cleaning method of the present invention;

Fig. 3 a is a polymer residue design sketch behind the embodiment of the present invention substrate cleaning method step S12;

Fig. 3 b is a polymer residue design sketch behind the embodiment of the present invention substrate cleaning method step S13;

Fig. 4 a is aluminium corrosive effect figure behind the embodiment of the present invention substrate cleaning method step S12;

Fig. 4 b is aluminium corrosive effect figure behind the embodiment of the present invention substrate cleaning method step S13.

Embodiment

Below in conjunction with accompanying drawing and specific embodiment the substrate cleaning method that the present invention proposes is done further explain.According to following explanation and claims, advantage of the present invention and characteristic will be clearer.

Core concept of the present invention is, a kind of substrate cleaning method is provided, utilize DSP solution to clean the substrate after the aluminum pad etching after, utilize carbon dioxide and washed with de-ionized water again.Fully react through carbon dioxide and deionized water, produce enough H⁺To remove OH^-Thereby, interrupt OH^-With the reaction of metal fluoride ion, reduce the loss of metal fluoride thus, farthest prevent the pad corrosion that fluorine ion causes.In addition, utilize DSP solution to clean after the substrate, again through this substrate of washed with de-ionized water; Deionized water can be taken away the particle of substrate surface; The polymer that produces in the more effective removal etching or other particulate pollutant can improve cleaning efficiency, thereby improve reliability of products.

Please refer to Fig. 1, it is the flow chart of substrate cleaning method of the present invention, and in conjunction with this Fig. 1, this method may further comprise the steps:

At first, execution in step S11 provides the substrate that is formed with pad.

In the present embodiment, said pad is an aluminum pad, and said aluminum pad can form through following process: on Semiconductor substrate, form metal layer at top; On the metal layer at top successively behind sedimentary cover and the overcoat, rotary coating photoresistance on overcoat adopts existing photoetching and developing technique then; On overcoat, form patterns of openings, utilize photoresistance to do afterwards and shelter, etching is not by behind the overcoat of photoresistance covering; Etching then forms the passivation layer with opening not by the cover layer of photoresistance covering again, on passivation layer, forms the barrier layer; Deposition of aluminum on the barrier layer, process photoetching and dry etching are to form aluminum pad.Can learn that in the photoetching and dry etching process of aluminum pad, can use plasma etching industrial, said etching technics has brought the problem of polymer residue.

In order to solve above-mentioned polymer residue problem, need execution in step S12, promptly utilize DSP solution to clean said substrate.Preferably, the time of utilizing DSP solution to clean said substrate is more than or equal to 1 minute.

Fig. 3 a is a polymer residue design sketch behind the embodiment of the present invention substrate cleaning method step S12; Shown in Fig. 3 a, behind the execution in step S12, still have partial polymer to remain on the said substrate; Specifically, through still havingpolymer 100 to remain on the said substrate after the cleaning of DSP solution.

And,, caused the aluminum pad corrosion thus because therefore the mixed solution that the employed DSP solution of step S12 is deionized water, hydrogen peroxide, sulfuric acid and hydrofluoric acid, when utilizing DSP solution to clean substrate, has inevitably introduced fluorine ion.Specifically shown in Fig. 4 a, it is aluminium corrosive effect figure behind the embodiment of the present invention substrate cleaning method step S12, and it has shown that cleaning the back through DSP solution corrodes 110 by the caused serious aluminium of fluorine ion.Need to prove that Fig. 3 a and 4a all are behind execution in step S12, through light microscope, with the taken design sketch of the different parts of a slice substrate.

Clean the back by the caused aluminium etching problem of fluorine ion in order farthest to solve through DSP solution, key of the present invention is, execution in step S13 utilizes carbon dioxide and deionized water to clean said substrate in wash chamber.Through inventor's discovery that studies for a long period of time, carbon dioxide can fully react with deionized water, produces enough H⁺To remove OH^-Thereby, interrupt original reaction 3, reduce (AlF₆)^3-Loss, farthest prevent the aluminum pad corrosion that fluorine ion causes.In addition, owing to utilize the cleaning of deionized water, further removed the polymer residue that brought in the aluminum pad etching and other particle contamination, can improve cleaning efficiency, thereby improve reliability of products substrate.

Optional, when carrying out step S13 of the present invention, the time of utilizing carbon dioxide and the said substrate of washed with de-ionized water is for more than or equal to 1 minute.Certainly, under and situation that aluminium etching problem less demanding residual to substrate polymers, the time of said cleaning also can be less than 1 minute.In the prior art, when utilizing DSP solution to clean substrate, feed CO₂Gas, this CO₂The time that gas fed is often above 3 minutes.Compared with prior art; Utilize method of the present invention to clean substrate, saved DSP solution and cleaned the time of substrate, though add through carbon dioxide and washed with de-ionized water substrate time also the time than prior art cleaning substrate few; Improve production efficiency, reduced cost.

In the present embodiment, utilize before the said substrate of carbon dioxide and washed with de-ionized water, can earlier said carbon dioxide and deionized water be mixed.Because before cleaning substrate, carbon dioxide mixes earlier with deionized water, make carbon dioxide to react with deionized water better, thereby produce enough H⁺To remove OH^-Preferable, can at room temperature said carbon dioxide and deionized water be mixed, the technology of this mixed process routine capable of using realizes, repeats no more at this.

Optional; In another embodiment of the present invention; Also can utilize carbon dioxide and deionized water when wash chamber is cleaned said substrate, said carbon dioxide is being fed said wash chamber to clean said substrate through different pipelines respectively with deionized water.Said carbon dioxide and deionized water feed wash chamber simultaneously, and it is long that the time ratio that can feed deionized water feeds time of carbon dioxide.So, behind carbon dioxide and washed with de-ionized water substrate, deionized water can further clean said substrate, has further removed the polymer residue that brought in the aluminum pad etching and other particle contamination, has improved the reliability of substrate.

In the present embodiment, when carrying out step S13 of the present invention, during promptly through the said substrate of carbon dioxide and washed with de-ionized water, the mode of high-pressure injection capable of using is sprayed onto said carbon dioxide and deionized water on the said substrate.Preferable, said high-pressure injection is under inert gas or nitrogen environment, to carry out, thereby prevents sneaking into of some other gases in the used usually air ambient, changes the component of deionized water, prevents to influence the effect of cleaning.

Please continue with reference to figure 3b and Fig. 4 b, wherein, Fig. 3 b is a polymer residue design sketch behind the embodiment of the present invention substrate cleaning method step S13, and Fig. 4 b is aluminium corrosive effect figure behind the embodiment of the present invention substrate cleaning method step S13.After Fig. 3 b and Fig. 4 b are execution in step S13, situation about arriving in different parts photographs through light microscope with a slice substrate.

Shown in Fig. 3 b; Than the polymer residue design sketch shown in Fig. 3 a; Behind step S13 of the present invention, promptly utilize the said substrate of carbon dioxide and washed with de-ionized water after, the polymer residue that the aluminum pad etching is brought has been removed fully; No longer includepolymer 100 the tangible polymer residues shown in Fig. 3 a among Fig. 3 b, the reliability of substrate has obtained further raising.

Shown in Fig. 4 b; Than the aluminium corrosive effect figure shown in Fig. 4 a; Through behind the step S13 of the present invention; After promptly utilizing the said substrate of carbon dioxide and washed with de-ionized water, the aluminum pad corrosion that fluorine ion causes has obtained tangible improvement, no longer includestangible aluminium corrosion 110 as shown in Fig. 4 a among Fig. 4 b.

In sum, through Fig. 3 a and 3b, the contrast between Fig. 4 a and the 4b can know, carry out step S13 of the present invention through carbon dioxide and the said substrate of washed with de-ionized water after, polymer residue on the substrate and aluminium etching problem have all obtained fairly obvious improvement.

Foregoing description only is the description to preferred embodiment of the present invention, is not any qualification to the scope of the invention, and any change, modification that the those of ordinary skill in field of the present invention is done according to above-mentioned disclosure all belong to the protection range of claims.

Claims (12)

1. a substrate cleaning method is characterized in that, comprising:

The substrate that is formed with pad is provided;

Utilize DSP solution to clean said substrate;

Utilize carbon dioxide and deionized water to clean said substrate in wash chamber.

2. substrate cleaning method as claimed in claim 1 is characterized in that said pad is an aluminum pad.

3. substrate cleaning method as claimed in claim 1 is characterized in that, utilizes time that DSP solution cleans said substrate more than or equal to 1 minute.

4. substrate cleaning method as claimed in claim 1 is characterized in that, the time of utilizing carbon dioxide and the said substrate of washed with de-ionized water was more than or equal to 1 minute.

5. substrate cleaning method as claimed in claim 1 is characterized in that, utilizes carbon dioxide and deionized water before wash chamber is cleaned said substrate, earlier said carbon dioxide and deionized water is mixed.

6. substrate cleaning method as claimed in claim 5 is characterized in that said carbon dioxide and deionized water at room temperature mix.

7. substrate cleaning method as claimed in claim 1; It is characterized in that; Utilize carbon dioxide and deionized water when wash chamber is cleaned said substrate, said carbon dioxide feeds said wash chamber to clean said substrate through different pipelines respectively with deionized water.

8. substrate cleaning method as claimed in claim 7 is characterized in that said carbon dioxide and deionized water feed said wash chamber simultaneously.

9. substrate cleaning method as claimed in claim 8 is characterized in that, it is long that the time ratio that feeds said deionized water feeds time of said carbon dioxide.

10. substrate cleaning method as claimed in claim 1 is characterized in that, through the mode of high-pressure injection, said carbon dioxide and deionized water is sprayed onto said substrate surface.

11. substrate cleaning method as claimed in claim 10 is characterized in that, said high-pressure injection is carried out under inert gas environment.

12. substrate cleaning method as claimed in claim 10 is characterized in that, said high-pressure injection is carried out under nitrogen environment.

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