Method for processing a semiconductor wafer

Abstract

The invention relates to a method for treating a semiconductor wafer (1), the method having a step for cleaning and / or conditioning a surface (11) of the semiconductor wafer (1), wherein the surface (11) is brought into contact with an aqueous solution (2) containing chloride ions and an oxidizing agent.

Description

Technical Field

[0001] This invention relates to a method for processing semiconductor wafers. More particularly, this invention relates to a method for processing semiconductor wafers, the method comprising steps for cleaning and / or conditioning the semiconductor wafers. Background Technology

[0002] Due to the sawing process used to prepare wafers from silicon ingots and / or due to the handling of semiconductor wafers, the surface of semiconductor wafers may have crystal defects, crystal damage, and / or contaminants. The depth of crystal damage and / or the type of contaminants depend on the specific process flow described above.

[0003] To obtain high-efficiency and mechanically stable semiconductor wafer solar cells, the semiconductor wafer should have as few contaminants as possible on its surface. Furthermore, to create a uniform texture on the surface of the semiconductor wafer, the surface needs to be cleaned and / or conditioned to be as uniform as possible before the texturing step.

[0004] Many methods are known for cleaning and conditioning the surface of semiconductor wafers. These methods are often referred to by abbreviations that are not universally accepted but commonly used in various fields, such as SC1, pSC1, and SCHMID cleaning. Additionally, as known from DE102008014166B3, the surface is treated with ozone in deionized water when appropriate. However, there is a need for an improved method for cleaning and / or conditioning the surface of semiconductor wafers, especially prior to the texturing step, in order to obtain semiconductor wafer solar cells with high solar cell efficiency and mechanical stability as much as possible. Summary of the Invention

[0005] Therefore, the object of the present invention is to provide a method for processing semiconductor wafers, the method having a step for cleaning and / or conditioning the surface of the semiconductor wafer, the step being effective in cleaning and / or conditioning the surface.

[0006] According to the invention, this objective is achieved by a method having the features described in claim 1. Advantageous improvements and modifications are given in the dependent claims.

[0007] This invention relates to a method for processing semiconductor wafers, the method comprising the step of cleaning and / or conditioning the surface of the semiconductor wafer, wherein the surface is contacted with an aqueous solution containing chloride ions and an oxidizing agent. Hereinafter, the aqueous solution containing chloride ions and an oxidizing agent is also referred to as a cleaning solution or conditioning solution.

[0008] The chloride ion / oxidant mixture exhibits very high reactivity and can react with organic or inorganic contaminants, such as metals, adhering to the surface of a semiconductor wafer, converting them into a water-soluble form. This effectively removes contaminants from the surface of the semiconductor wafer. The active cleaning substances formed in the mixture, such as HClO or Cl2, can be generated in situ during this step by mixing the oxidant with an initial material containing Cl ions in an aqueous solution. This method is preferably formulated for cleaning and conditioning the surface of the semiconductor wafer.

[0009] In a preferred embodiment, the oxidant is selected from the group consisting of H2O2 or ozone. H2O2 is preferred as the oxidant. Alternatively, ozone is preferred as the oxidant.

[0010] The initial material containing Cl ions is preferably a liquid. This eliminates the costly stoichiometric process required for solids (e.g., sodium salts). The chloride ions are preferably derived from HCl (hydrochloric acid) contained in the aqueous solution. The overall chemical formula can be represented as HCl(aq). HCl(aq), also known as hydrochloric acid, is an aqueous solution of gaseous hydrogen chloride, which dissociates into hydrated hydrogen ions (H3O+) and chloride ions.

[0011] In a preferred embodiment, the cleaning or conditioning solution is generated by adding ozone to an aqueous solution having a Cl ion ratio of 0.01-10.00% by weight (e.g., hydrochloric acid) and 90.00-99.90% by weight of water.

[0012] In a preferred embodiment, the cleaning or conditioning solution is generated by adding 1.00-10.00% hydrogen to an aqueous solution having a Cl ion ratio of 0.01-10.00% by weight (e.g., hydrochloric acid) and 80.00-90.00% by weight of water.

[0013] In a preferred embodiment, the aqueous solution further comprises HF (hydrofluoric acid). This also allows for improved surface conditioning.

[0014] The cleaning and / or conditioning steps are preferably performed at a temperature in the range of 15°C to 60°C, preferably 20°C to 40°C. Contact between the surface and the aqueous solution (i.e., the cleaning or conditioning solution) is preferably maintained for 15 seconds to 60 minutes, preferably 3 to 40 minutes.

[0015] Following the steps of cleaning and / or conditioning the surface of the semiconductor wafer, the surface of the semiconductor wafer is preferably subjected to a rinsing step, in which the surface is rinsed with water, preferably pure water. This effectively removes the aqueous solutions used in the cleaning and / or conditioning steps, as well as contaminants converted into water-soluble forms, from the surface. The rinsing step can be performed by immersing, inserting, spraying, or wetting the semiconductor wafer surface that has undergone the cleaning and / or conditioning steps with water.

[0016] After the steps of cleaning and / or conditioning the surface of the semiconductor wafer, or after the rinsing step, the surface of the semiconductor wafer preferably undergoes a texturing step, in which the surface is brought into contact with a texturing solution. This causes the surface to undergo texturing etching, which produces a roughened semiconductor wafer surface such that at least a portion of the light not incident on the semiconductor wafer is reflected, thereby allowing the light to repeatedly strike the semiconductor wafer surface and then, as far as possible, be input into the semiconductor material. In most cases, such texturized surfaces have a pyramidal structure. The texturing step can be performed by immersing, inserting, spraying, or wetting the surface of the semiconductor wafer to be texturized with a texturing solution. The steps for cleaning and / or conditioning the surface specifically remove contaminants from the surface of the semiconductor wafer that might have acted as a mask during the texturing step. Therefore, this combination of these method steps is reasonable.

[0017] The texturing step preferably includes treating the semiconductor wafer with an alkaline solution. An aqueous solution of sodium hydroxide and / or potassium hydroxide with organic additives can be used as the alkaline solution. Alkaline texturing is performed anisotropically. Texturing conditions such as time and temperature depend on the type and concentration of the texturing solution.

[0018] The texturing process can be performed in one step or in multiple steps, and can form a combination of two or more texturing types. For example, the texturing process includes sawing etching and alkaline texturing.

[0019] In a preferred embodiment, the semiconductor wafer undergoes a single texturing step. The texturing step can also be performed such that both surfaces of the semiconductor wafer are texturized. However, it is preferred to perform the texturing step on one side only, so that the semiconductor wafer undergoes a single texturing step.

[0020] In the step of cleaning and / or conditioning the surface, contacting the aqueous solution with the surface of the semiconductor wafer, i.e., with the cleaning solution or conditioning solution, can be performed by immersing, inserting, spraying, or wetting the surface of the semiconductor wafer with the aqueous solution. In a preferred embodiment, contacting the surface of the semiconductor wafer is performed by immersing the semiconductor wafer in a pool containing the aqueous solution (i.e., the cleaning solution or conditioning solution). This further effectively removes contaminants from the surface.

[0021] In a preferred embodiment, the steps for cleaning and / or conditioning the surface of the semiconductor wafer are performed after the semiconductor wafer has been prepared by sawing. Therefore, the semiconductor wafer used in this method is preferably freshly sawn. Alternatively, prior to the steps for cleaning and / or conditioning the surface, the semiconductor wafer may preferably undergo an etching step, such as a sawing etching step, a damaging etching step, and / or a polishing etching step.

[0022] The semiconductor wafer is preferably a silicon wafer. Silicon is particularly suitable as a wafer material.

[0023] In a preferred embodiment, the method is carried out in a batch wet cleaning machine or an in-line wet cleaning machine. Alternatively, the above method steps may be carried out in a time-decoupled manner. The steps for cleaning and / or conditioning, the texturing step, and the rinsing step in between are preferably performed sequentially without any intervening steps. In a preferred embodiment, these steps can be carried out in a single facility. This saves costs and avoids processing. Attached Figure Description

[0024] Embodiments of the present invention are shown in the accompanying drawings by way of illustration only and will be described in detail below. The accompanying drawings are shown in an illustrative manner and not to scale:

[0025] Figures 1 to 3 The method steps of the present invention are illustrated in cross-sectional views of the respective facilities. Detailed Implementation

[0026] Figures 1 to 3 The method steps of the present invention are illustrated in cross-sectional views of the respective facilities. A semiconductor wafer 1 having surface 11 and another surface 12 is subjected to the method. The method includes steps for cleaning and / or conditioning surface 11. Figure 1 ), optional rinsing steps ( Figure 2 ) and the down-making process ( Figure 3 ).

[0027] exist Figure 1The diagram illustrates steps for cleaning and / or conditioning the surface 11 of a semiconductor wafer 1, wherein the surface 11 is brought into contact with an aqueous solution 2 (i.e., a cleaning solution or conditioning solution), which is contained in a pool 3 of a facility (not shown). The surface 11 is immersed in the aqueous solution 2 containing chloride ions and an oxidizing agent (such as H2O2 or ozone).

[0028] Following the steps for cleaning and / or conditioning the surface 11 of the semiconductor wafer 1, the surface 11 undergoes an optional rinsing step, in which the surface is immersed in another pool 6 containing pure water 4, as in Figure 2 As shown in the diagram. The rinsing step may include immersing the semiconductor wafer 1 multiple times in another pool 6.

[0029] After the step of cleaning and / or conditioning the surface 11 of the semiconductor wafer 1, or after an optional rinsing step, the surface 11 undergoes a texturing step in which the surface is immersed in a further pool 7 containing a texturing solution 5, so that the surface 11 comes into contact with the texturing solution 5 and is thus texturized.

[0030] In the method shown, surface 11 is subjected to the method, but surface 11 and another surface 12 can also be subjected to the method or method steps simultaneously, which is not shown here. Similarly, not only a single semiconductor wafer 1, but also multiple semiconductor wafers 1 can be subjected to the method or method steps simultaneously.

[0031] The following will explain the implementation details:

[0032] Example 1:

[0033] Ozone is added to an aqueous solution having a Cl ion ratio of 0.01-10.00% by weight (such as hydrochloric acid) and 90.00-99.90% water to produce an aqueous solution 2 as a cleaning or conditioning solution, which allows one or more semiconductor wafers to contact the aqueous solution with both surfaces.

[0034] The temperature of aqueous solution 2 is 25°C to 30°C. After a processing time of 10 minutes, the semiconductor wafers are subjected to a rinsing step, in which they are rinsed with water at 25°C to 30°C. Subsequently, the semiconductor wafers are subjected to an alkaline texturing step.

[0035] List of reference numerals in the attached diagram:

[0036] 1 semiconductor wafer

[0037] 11 Surface

[0038] 12 Another surface

[0039] 2 solutions

[0040] 3 pools

[0041] 4 water

[0042] 5. Texturing solution

[0043] 6 Another pool

[0044] 7. In another pool

Claims

1. A method for processing a semiconductor wafer (1), the method comprising steps for cleaning and / or conditioning the surface (11) of the semiconductor wafer (1), wherein the surface (11) is contacted with an aqueous solution (2) comprising chloride ions, an oxidant and HF (hydrofluoric acid), after the step of cleaning and / or conditioning the surface (11) of the semiconductor wafer (1), the surface (11) of the semiconductor wafer (1) is subjected to a rinsing step in which the surface is rinsed with water (4), and the surface (11) of the semiconductor wafer (1) is subjected to a texturing step in which the surface (11) is contacted with a texturing solution (5).

2. The method according to claim 1, characterized in that, The oxidant consists of H2O2 or ozone.

3. The method according to claim 1 or 2, characterized in that, The chloride ions originate from HCl (hydrochloric acid) contained in the aqueous solution.

4. The method according to claim 1, characterized in that, The semiconductor wafer undergoes a single texturing process.

5. The method according to claim 1, characterized in that, The surface (11) is brought into contact with an aqueous solution (2) containing chloride ions, an oxidant and HF (hydrofluoric acid) by immersing the semiconductor wafer (1) in a pool (3) containing the aqueous solution (2).

6. The method according to claim 1, characterized in that, The semiconductor wafer (1) is a silicon wafer.

7. The method according to claim 1, characterized in that, The method is performed in a batch wet cleaning machine or an online wet cleaning machine.

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