Method for cleaning surface of silicon wafer by adopting micro-nano bubble water
By using micro-nano bubble water adsorption and bursting technology, the problem of residual particles at the bottom of the pyramid on the silicon wafer surface was solved, achieving a highly efficient cleaning effect and improving the cleanliness of the silicon wafer and the quality of subsequent film layers.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-01
- Publication Date
- 2026-03-10
AI Technical Summary
In existing silicon wafer cleaning processes, particles remaining at the bottom of the pyramid cannot be completely cleaned, resulting in excessive residual particles on the silicon wafer surface, which affects the quality of subsequent film layers.
Micro-nano bubble water is used to clean the surface of silicon wafers. Particles are adsorbed by micro-nano bubbles with opposite charges, and the shock wave generated by the bursting of the bubbles removes the particles from the surface of the silicon wafers. The process is then combined with tunnel drying technology for drying.
It significantly reduces the amount of particles on the silicon wafer surface, achieving a cleaning effect of over 97%, thus improving the quality of the film and cleaning efficiency.
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Figure CN121646290A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application belongs to the technical field of silicon wafer cleaning, and particularly relates to a method for cleaning the surface of a silicon wafer by using micro-nano bubble water. BACKGROUND
[0002] The cleaning method for the surface of a silicon wafer mainly includes alkali etching cleaning and RCA cleaning. The conventional alkali etching cleaning process generally includes the following steps: pre-cleaning, water washing, alkali etching, water washing, post-cleaning, water washing, acid washing, water washing, slow lifting and dehydration, drying, etc. The existing cleaning mainly removes the residual acid and particles on the surface of a silicon wafer by water washing after acid washing, and performs drying treatment by tank drying. The conventional RCA cleaning process generally includes the following steps: alkali etching, water washing, post-cleaning, water washing, acid washing, water washing, acid washing, water washing, slow lifting, drying, etc. At present, the residual acid and particles on the surface of a silicon wafer are mainly removed by water washing after acid washing, and drying treatment is performed by tank drying.
[0003] However, both alkali etching cleaning and RCA cleaning need to remove the residual acid after acid washing and the final residual particles by water washing. Since the surface tension of water is large, the bottom of the pyramid on the surface of a silicon wafer cannot be cleaned deeply, and secondary pollution occurs in the subsequent drying process, which finally leads to more than 500 residual particles on the surface of a silicon wafer.
[0004] Therefore, how to overcome the defect that the bottom of the pyramid cannot be cleaned completely in the existing silicon wafer cleaning process is a technical problem that needs to be solved in the field.
[0005] It should be noted that the above information disclosed in the background section is only used to understand the background of the present application, and therefore, the above description is not considered as information of the prior art. SUMMARY
[0006] The present application at least provides a method for cleaning the surface of a silicon wafer by using micro-nano bubble water.
[0007] In a first aspect, the present application provides a method for cleaning the surface of a silicon wafer by using micro-nano bubble water, which includes the following steps: S1, adding a silicon wafer into functional water, wherein the functional water includes micro-nano bubbles and is loaded with charges opposite to the particles; S2, allowing the micro-nano bubbles to form adsorption on the particles on the surface of the silicon wafer, and then making the micro-nano bubbles separate from the surface of the silicon wafer; and S3, blasting the micro-nano bubbles remaining on the surface of the silicon wafer, so that the residual particles are affected by the shock wave generated by the blasting of the micro-nano bubbles and separate from the surface of the silicon wafer.
[0008] In an optional embodiment, the functional water is micro-nano bubble water, the diameter of the micro-nano bubbles ranges from 10 nm to 100 μm, and the concentration is 10 6 ~ 109 grains / ml.
[0009] In an alternative embodiment, the silicon wafer in step S1 is further subjected to a pre-treatment before being immersed in the functional water.
[0010] In an alternative embodiment, the pre-treatment comprises immersing the silicon wafer in a metal ion solution to charge the surface grains of the silicon wafer.
[0011] In an alternative embodiment, the silicon wafer in step S1 is placed in at least one of a horizontal position and a vertical position.
[0012] In an alternative embodiment, the silicon wafer in step S1 is subjected to a surface grain and micro-nano bubble contact by being sprayed with the functional water or immersed in the functional water.
[0013] In an alternative embodiment, the micro-nano bubbles with the adsorbed grains are detached from the surface of the silicon wafer in step S2 by bubbling or brushing.
[0014] In an alternative embodiment, step S2 further comprises turning on an electric field to adsorb the micro-nano bubbles in the functional water to the surface of the grains and / or horizontally repelling or moving up and down the micro-nano bubbles with the adsorbed grains by the electric field.
[0015] In a second aspect, the embodiments of the present disclosure further provide an alkaline cleaning process, which comprises, in sequence, pre-cleaning, water washing, alkaline cleaning, water washing, post-cleaning, water washing, acid cleaning, water washing, functional water washing, slow lifting, and drying; wherein the functional water washing uses the micro-nano bubble water to clean the surface of the silicon wafer according to the method described above; and the drying comprises tunnel drying.
[0016] In a third aspect, the embodiments of the present disclosure further provide an RCA cleaning process, which comprises, in sequence, alkaline etching, water washing, post-cleaning, water washing, acid cleaning, water washing, acid cleaning, functional water washing, slow lifting, and drying; wherein the functional water washing uses the micro-nano bubble water to clean the surface of the silicon wafer according to the method described above; and the drying comprises tunnel drying.
[0017] The method for cleaning the surface of the silicon wafer by using the micro-nano bubble water has the advantages that: the high permeability and low surface tension of the functional water, and the micro-nano bubbles with a diameter of microns are used to thoroughly clean the deep-layer grains at the bottom of the silicon wafer pyramid and the bottom of the alkaline cleaning tower; the effective adsorption of the micro-nano bubbles and the surface grains of the silicon wafer is achieved by using opposite positive and negative electrodes; the effective cleaning of the residual micron-level grains is achieved in the pre-adsorption and post-adsorption detachment and the post-blast detachment; and the grains on the surface of the silicon wafer are reduced by more than 97% compared with the conventional process, while the drying treatment is performed in cooperation with the tunnel drying.
[0018] Other features and advantages of the present application will be set forth in the descriptions that follow, and in part will be apparent from the description or can be learned by practice of the application. The purposes and other advantages of the application will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
[0019] To make the above objectives, features and advantages of the present application more obvious and easy to understand, the following preferred embodiments are specifically described below, and the accompanying drawings are referred to. BRIEF DESCRIPTION OF DRAWINGS
[0020] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the following will briefly introduce the drawings needed to be used in the specific embodiments or the prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.
[0021] Figure 1 The pure water + tank drying particle increase amount characterization graph of the comparative group provided by the embodiment of the present disclosure;
[0022] Figure 2 The functional water + tunnel drying particle increase amount characterization graph of the experimental group provided by the embodiment of the present disclosure;
[0023] Figure 3 The tank drying and tunnel drying particle increase amount comparison graph provided by the embodiment of the present disclosure. DETAILED DESCRIPTION
[0024] In order to make the purposes, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions of the present application will be described clearly and completely in combination with the drawings. Obviously, the described embodiments are some of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the present application.
[0025] As used herein, the phrases "in one embodiment", "according to one embodiment", "in some embodiments", and the like are generally intended to refer to the fact that a particular feature, structure, or characteristic described in connection with a given embodiment can be included in at least one embodiment of the disclosure. Thus, the appearances of the phrases "in one embodiment", "according to one embodiment", "in some embodiments", and the like are not necessarily referring to the same embodiment. As used herein, the terms "example", "exemplary", and the like are used as examples, instances, or illustrations. Any implementation, aspect, or design described herein as "example" or "exemplary" is not necessarily to be construed as preferred or advantageous over other implementations, aspects, or designs. Rather, the use of the terms "example", "exemplary", and the like is intended to present concepts in a concrete manner.
[0026] In this document, example embodiments of the disclosure will be described in greater detail with reference to the attached drawings. As used herein, expressions such as "at least one of", when preceded by the term "comprising", are intended to mean one or more of the listed elements or ingredients. For example, the expression "at least one of a, b and c" is intended to mean a, b, c, a and b, a and c, b and c, or a, b and c.
[0027] Some embodiments of the present application will be described in detail with reference to the drawings in conjunction with the following embodiments. The embodiments described below and the features in the embodiments can be combined with each other as long as there is no conflict.
[0028] The embodiment of the present disclosure provides a method for cleaning the surface of a silicon wafer by using micro-nano bubble water, comprising the following steps: S1, adding a silicon wafer into functional water, wherein the functional water comprises micro-nano bubbles and carries opposite charges to the particles; S2, after the micro-nano bubbles adsorb the particles on the surface of the silicon wafer, the micro-nano bubbles are separated from the surface of the silicon wafer; S3, the micro-nano bubbles remaining on the surface of the silicon wafer are burst, and the residual particles are separated from the surface of the silicon wafer under the influence of the shock wave generated by the burst of the micro-nano bubbles.
[0029] In some embodiments, specifically, the functional water is micro-nano bubble water, the diameter of the micro-nano bubble ranges from 10 nm to 100 μm, and the concentration is 10 6 ~10 9 μg / ml.
[0030] Specifically, there are charges on the surface of the functional water. During the rising of the bubbles in the liquid, the bubbles shrink and become smaller, and the charge density increases. When the functional water disappears, a large amount of energy is released, and the particles are stripped from the surface of the object under the action of the force through the different charges carried by the surface of the functional water and the surface of the particles.
[0031] Specifically, in the functional water, the energy released when the bubbles with surface charges disappear makes the functional water generate a large number of hydroxyl radicals, which have strong oxidizing properties and can remove the organic matter on the surface of the object to be cleaned.
[0032] In some embodiments, specifically, the step S1 further includes a pretreatment before the silicon wafer is put into the functional water.
[0033] In some embodiments, specifically, the pretreatment includes soaking the silicon wafer in a metal ion solution to load charges on the surface particles of the silicon wafer.
[0034] In some embodiments, specifically, the way of placing the silicon wafer in the step S1 includes at least one of horizontal placement and vertical placement.
[0035] Specifically, the micro-nano bubbles in the functional water will rise, and the horizontal placement of the silicon wafer before the vertical placement can more effectively improve the cleaning efficiency.
[0036] In some embodiments, specifically, in the step S1, the surface particles of the silicon wafer are in sufficient contact with the micro-nano bubbles by being sprayed with the functional water or soaked in the functional water.
[0037] Specifically, by pre-soaking the functional water, the micro-nano bubbles are more easily adsorbed on the edges, peaks and other uneven places when slowly lifting, thereby improving the cleaning efficiency.
[0038] In some embodiments, specifically, in the step S2, the micro-nano bubbles adsorbed with the particles are detached from the surface of the silicon wafer by bubbling or brushing.
[0039] In some embodiments, specifically, the step S2 further includes turning on an electric field to adsorb the micro-nano bubbles in the functional water to the surface of the particles and / or horizontally repelling or moving up and down the micro-nano bubbles adsorbed with the particles by the electric field.
[0040] The embodiments of the present disclosure also provide an alkaline cleaning process, which includes, in sequence, pre-cleaning, water washing, alkaline cleaning, water washing, post-cleaning, water washing, acid cleaning, water washing, functional water cleaning, slow lifting, and drying; wherein the functional water cleaning uses the method described above to clean the surface of the silicon wafer with micro-nano bubble water; and the drying includes tunnel drying.
[0041] The embodiments of the present disclosure also provide an RCA cleaning process, which includes, in sequence, alkaline etching, water washing, post-cleaning, water washing, acid cleaning, water washing, acid cleaning, functional water cleaning, slow lifting, and drying; wherein the functional water cleaning uses the method described above to clean the surface of the silicon wafer with micro-nano bubble water; and the drying includes tunnel drying.
[0042] Specifically, the tunnel drying adopts a ring closed loop drying, avoids the particulate matter in the external space from entering the drying cavity to cause secondary pollution on the surface of the silicon wafer after cleaning, thereby improving the cleanliness of the silicon wafer after drying.
[0043] Specifically, the present application deals with the cleaning of silicon wafers in the production process of photovoltaic cells. After single-side BSG removal, the silicon wafers need to be treated by alkali etching. After alkali etching, a passivation film layer needs to be made on the polished surface. In order to ensure the quality of the film layer, the surface of the silicon wafer after alkali etching needs to maintain high cleanliness. The final cleaning of the traditional alkali etching process is pure water cleaning, and there are still many micron-sized particles remaining on the polished surface of the silicon wafer after cleaning. Since the thickness of the tunnel oxide layer and the polysilicon layer in the subsequent process is nanometer level, the micron-sized particle pollution has a great impact on the quality of the film layer. Therefore, a new functional water cleaning method for silicon wafers is invented to realize the above micron-sized particle cleaning function.
[0044] Example 1
[0045] The cleaning method is alkali etching cleaning, which comprises the following steps:
[0046] S11, the silicon wafer is placed in a carrier and put into a pre-cleaning tank, and the surface of the silicon wafer is cleaned by an alkaline hydrogen peroxide solution, the reaction temperature is 60-80℃, and the reaction time is 90-180 seconds;
[0047] S12, the carrier is transferred to a water washing tank, and the residual chemical liquid on the surface of the silicon wafer is removed by overflow rinsing with pure water, the rinsing temperature is normal temperature, and the rinsing time is 120-180 seconds;
[0048] S13, the carrier is transferred to an alkali etching tank, and the back surface of the silicon wafer is etched by alkali and additives, the reaction temperature is 50-80℃, and the reaction time is 180-300 seconds;
[0049] S14, the carrier is transferred to a water washing tank, and the residual chemical liquid on the surface of the silicon wafer is removed by overflow rinsing with pure water, the rinsing temperature is normal temperature, and the rinsing time is 120-180 seconds;
[0050] S15, the carrier is transferred to a post-cleaning tank, and the residual additives and alkaline chemical liquid on the surface of the silicon wafer are removed by an alkaline hydrogen peroxide solution;
[0051] S16, the carrier is transferred to a pure water rinsing tank, and the residual chemical liquid is removed by overflow rinsing with pure water, the rinsing temperature is normal temperature, and the rinsing time is 120-180 seconds;
[0052] S17, the carrier is transferred to an acid washing tank, and the residual alkali and metal ions on the surface of the silicon wafer are removed by an acidic chemical liquid;
[0053] S18, transfer the vehicle to the pure water rinsing tank and rinse it with pure water overflow to remove residual medicine. The rinsing temperature is room temperature and the rinsing time is 120-180 seconds.
[0054] S19, the carrier is transferred to a functional water rinsing tank to remove micron-sized particles from the silicon wafer surface. The functional water in the rinsing tank is micro / nano bubble water with a diameter ranging from 10 nm to 100 μm and a concentration of 10%. 6 ~10 9 granules / ml;
[0055] S110, the carrier is transferred to the hot water slow-lift tank for pre-dehydration before drying;
[0056] S111: Transfer the carrier to the drying tank and dry the silicon wafers using a tunnel drying method. The drying temperature is 65-85℃ and the drying time is less than 10 minutes.
[0057] Specifically, step S19 uses the cleaning method described above to clean the surface of the silicon wafer with functional water.
[0058] Specifically, in step S19, the silicon wafers are placed vertically into a basket, and the robotic arm picks up the basket containing the silicon wafers and places it in a cleaning tank for soaking and cleaning.
[0059] Specifically, in step S19, the micro-nano bubbles detach because the surface charge of the micro-nano bubbles is the same as that of the silicon wafer. Under the action of repulsion, the micro-nano bubbles and the silicon wafer will not adhere to each other, and thus detach.
[0060] Please see Figure 1 and Figure 2 ,like Figure 1 and Figure 2 The figures shown are the particle size distribution charts for the control group (pure water + trough drying) and the experimental group (functional water + tunnel drying), respectively. Specific data are shown in Table 1 and below. Figure 3 As shown, the increase in particle size on the surface of silicon wafers properly treated with tunnel drying (right) is significantly lower than that with trough drying (left), and this applies to silicon wafers of different sizes.
[0061] Table 1
[0062] Particle size (um) Pure water washing + tray drying Functional water washing + tunnel drying 0.1-0.136 318 2 0.136-0.202 80 0 0.202-0.309 230 0 0.309-1.005 75 3 1.005-2.005 28 7 2.005-5.125 2 0 ＞5.125 18 6 Total 751 18
[0063] Specifically, as shown in Table 2, the alkaline polishing machine with water + tunnel drying method was used as the experimental group, and the alkaline polishing machine with pure water + tank drying method was used as the control group. The electrical performance verification data are as follows:
[0064] Table 2
[0065]
[0066]
[0067] Specifically, in the table, Eta refers to conversion efficiency, Uoc refers to open circuit voltage (v), Isc refers to short circuit current (A), FF refers to fill factor, Rs refers to contact resistance (ohm), Rsh refers to parallel resistance (ohm), and Irev refers to leakage current (A). The same meaning as herein is used again below.
[0068] Specifically, the present application deals with the RCA cleaning of a silicon wafer in the production process of a photovoltaic cell. After single-sided PSG removal, the silicon wafer needs to be subjected to front-side polysilicon plating etching and cleaning treatment. After RCA, an aluminum oxide passivation film layer needs to be made on the front side. In order to ensure the quality of the film layer, the surface of the silicon wafer after RCA needs to maintain high cleanliness. The final cleaning of the traditional RCA process is pure water cleaning, and after cleaning, there are still many micron-sized particles on the surface of the silicon wafer, which greatly affects the quality of the subsequent aluminum oxide passivation film layer. Therefore, a brand new functional water silicon wafer cleaning method is invented to achieve the above micron-sized particle cleaning function and improve the passivation effect of the subsequent film layer.
[0069] Example 2
[0070] The cleaning method is RCA cleaning, which comprises the following steps:
[0071] S21, the silicon wafer is placed in a carrier and put into an alkali etching tank to etch the front-side plated polysilicon through an alkaline solution, the reaction temperature is 60-80℃, and the reaction time is 300-400 seconds;
[0072] S22, the carrier is transferred to a water washing tank to remove the residual chemical liquid on the surface of the silicon wafer by overflow rinsing with pure water, the rinsing temperature is normal temperature, and the rinsing time is 120-180 seconds;
[0073] S23, the carrier is transferred to a post-cleaning tank to remove the additives and residual alkaline chemical liquid on the surface of the silicon wafer through an alkaline hydrogen peroxide solution;
[0074] S24, the carrier is transferred to a pure water rinsing tank to remove the residual chemical liquid by overflow rinsing with pure water, the rinsing temperature is normal temperature, and the rinsing time is 120-180 seconds;
[0075] S25, the carrier is transferred to an acid washing tank to remove the alkaline liquid and oxide layer on the surface of the silicon wafer through an acidic chemical liquid;
[0076] S26, the carrier is transferred to a pure water rinsing tank to remove the residual chemical liquid by overflow rinsing with pure water, the rinsing temperature is normal temperature, and the rinsing time is 120-180 seconds;
[0077] S27, the carrier is transferred to an acid washing tank to remove the oxide layer on the surface of the silicon wafer through an acidic chemical liquid to improve the hydrophobicity of the surface of the silicon wafer;
[0078] S28, transfer the carrier to a pure water rinsing tank to remove residual chemical liquid by pure water overflow, the rinsing temperature is normal temperature, and the rinsing time is 120-180 seconds;
[0079] S29, transfer the carrier to a functional water cleaning tank to remove micrometer-level particles on the surface of the silicon wafer, wherein the functional water in the functional water cleaning tank is micro-nano bubble water, the diameter range is 10 nm-100 pm, and the concentration is 10 6 ~10 9 particles per ml;
[0080] S210, transfer the carrier to a hot water slow lifting tank body to perform pre-dewatering before drying, improve the subsequent drying effect, and shorten the drying time;
[0081] S211, transfer the carrier to a drying tank to dry the silicon wafer in a tunnel drying manner, the drying temperature is 65-85 DEG C, and the drying time is less than 10 minutes.
[0082] Specifically, the step S29 adopts the cleaning method as described above to clean the surface of the silicon wafer by the functional water.
[0083] Specifically, in the step S29, the silicon wafer is vertically inserted into a basket, and a mechanical hand holds the basket containing the silicon wafer and is placed in the cleaning tank for immersion cleaning.
[0084] Specifically, in the step S29, the micro-nano bubble is detached in the following manner: the surface charge of the micro-nano bubble is of the same polarity as the surface charge of the silicon wafer, and under the repulsive force, the micro-nano bubble does not adhere to the silicon wafer, and is detached.
[0085] Specifically, as shown in Table 3, the RCA functional water + tunnel drying method is used as an experimental group, and the RCA pure water + tank drying method is used as a comparison group, and the electrical performance verification data are as follows:
[0086] Table 3
[0087] Type Eta Uoc Isc FF Rs Rsh Irev Comparative group 26.236 0.7393 13.8946 85.51 0.00052 3430 0.029 Experimental group 26.292 0.7402 13.9003 85.55 0.00052 3463 0.026 GAP (experimental - comparative) 0.056 0.0009 0.0057 0.04 0 33 -0.003
[0088] In summary, the method for cleaning the surface of the silicon wafer by the micro-nano bubble water can thoroughly clean the micrometer-level particles on the bottom of the silicon wafer pyramid and the bottom of the alkali etching tower by the high permeability and low surface tension of the functional water, the effective adsorption of the micro-nano bubble and the silicon wafer surface particles by the opposite positive and negative poles, and the effective cleaning of the residual micrometer-level particles in the front adsorption and detachment and the rear explosion detachment. Meanwhile, the tunnel drying is used for drying treatment, so that the particle amount on the surface of the silicon wafer is reduced by more than 97% compared with the conventional process.
[0089] With the above ideal embodiments according to the present application as the inspiration, through the above description, relevant staff can make various changes and modifications without deviating from the technical idea of the present application. The technical scope of the present application is not limited to the content of the specification, and must be determined according to the scope of the claims.
Claims
1. A method for cleaning the surface of a silicon wafer using micro-nano bubble water, characterized by, The method comprises the following steps: S1, adding the silicon wafer into functional water, wherein the functional water comprises micro-nano bubbles and is loaded with charges opposite to the particles on the surface of the silicon wafer; S2, allowing the micro-nano bubbles to adsorb the particles on the surface of the silicon wafer, and then separating the micro-nano bubbles from the surface of the silicon wafer; S3, blasting the micro-nano bubbles remaining on the surface of the silicon wafer, and allowing the residual particles to be separated from the surface of the silicon wafer under the impact of the shock wave generated by the blasting of the micro-nano bubbles.
2. The method according to claim 1, wherein the silicon wafer is placed in at least one of a horizontal manner and a vertical manner in the step S1. The functional water is micro-nano bubble water, the micro-nano bubble diameter range is 10nm-100μm, and the concentration is 10 6 -10 9 μg / ml.
3. The method according to claim 1, wherein the silicon wafer is pre-treated before being added into the functional water in the step S1.
4. The method according to claim 3, wherein the pre-treatment comprises immersing the silicon wafer in a metal ion solution to load the particles on the surface of the silicon wafer with charges.
5. The method according to claim 1, wherein the particles on the surface of the silicon wafer are fully contacted with the micro-nano bubbles by spraying or immersing the silicon wafer in the functional water in the step S1.
6. The method according to claim 1, wherein the particles on the surface of the silicon wafer are fully contacted with the micro-nano bubbles by spraying or immersing the silicon wafer in the functional water in the step S1.
7. The method according to claim 1, wherein the micro-nano bubbles adsorbed with the particles are separated from the surface of the silicon wafer by bubbling or brushing in the step S2.
8. The method according to claim 1, wherein the step S2 further comprises turning on an electric field to adsorb the micro-nano bubbles in the functional water to the surface of the particles and / or moving the micro-nano bubbles adsorbed with the particles horizontally or up and down by the electric field. The sequence comprises pre-cleaning, water washing, alkali etching, water washing, post-cleaning, water washing, acid washing, water washing, functional water washing, slow pulling, and drying; The functional water washing is performed by the method according to any one of claims 1-8; The drying comprises tunnel drying. The sequence comprises alkali etching, water washing, post-cleaning, water washing, acid washing, water washing, acid washing, functional water washing, slow pulling, and drying; The functional water washing is performed by the method according to any one of claims 1-8; The drying comprises tunnel drying.
9. An alkaline throwaway cleaning process characterized by, 10. An RCA cleaning process characterized by,