Cleaning method for silicon wafer without end face treatment
The organic acid cleaning method solves the problem of particulate contamination on the surface of silicon wafers without end face treatment, achieving high-cleanliness silicon wafer cleaning. It is applicable to all types of silicon wafers, especially silicon wafers without end face treatment, and is low in cost.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-16
- Publication Date
- 2026-04-14
AI Technical Summary
Existing cleaning technologies are ineffective at removing particulate contamination from the surface of silicon wafers without end face treatment, and DHF reacts with the SiO2 layer at the edge of the silicon wafer chamfer, leading to increased particulate contamination.
An organic acid cleaning method is employed, which involves multiple steps of cleaning the silicon wafer using a mixture of pure water, NH4OH, H2O2 and H2O, and acetic acid solution to avoid reaction with the SiO2 layer and remove metal, organic matter and particulate contamination.
It achieves high cleanliness of silicon wafer surfaces without end face processing, reduces particulate contamination, is applicable to all types of silicon wafers, especially those without end face processing, and is less expensive than traditional methods.
Smart Images
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Abstract
Description
Technical Field
[0001] This application relates to the field of silicon wafer cleaning, and in particular to a cleaning method for silicon wafers without end face processing. Background Technology
[0002] In the semiconductor manufacturing industry, silicon wafers, as the fundamental material for integrated circuits, directly impact the performance and reliability of the final product due to their surface quality. As semiconductor technology advances towards the nanoscale, the requirements for the cleanliness of silicon wafer surfaces become increasingly stringent. Even minute contamination can lead to short circuits and leakage during downstream chip manufacturing, affecting the chip's electrical characteristics and reducing product quality. Research on particles on the silicon wafer surface has long been a subject of intense study and research for many semiconductor industry professionals. This is because particulate contaminants on the silicon wafer surface can amplify during subsequent processing, potentially causing scratches or defects on the chip surface, affecting the precision of the photolithography process, and ultimately leading to device failure.
[0003] Silicon wafer manufacturing typically involves processes such as crystal growth, crystal pulling, slicing, chamfering, grinding, etching, chemical vapor deposition (CVD), chemical mechanical polishing (CMP), and cleaning. Silicon wafer cleaning usually employs the standard RCA cleaning method, namely SC1+SC-2 or SC-1+DHF, which effectively removes metal, organic matter, and particulate contaminants from the silicon wafer surface. However, the SC-2 process, due to the use of HCl, is corrosive and requires sophisticated equipment and plant systems. DHF, with its lower concentration, removes the oxide layer and metallic impurities from the silicon wafer surface through etching, making it suitable for cleaning most silicon wafer products. However, when cleaning silicon wafers without end-face treatment, a loose SiO2 layer is deposited at the chamfered edges. DHF reacts with this layer, causing SiO2 particles to fall off, resulting in particulate contamination. Furthermore, with each cleaning cycle, the SiO2 layer becomes increasingly porous, leading to more particle loss. Therefore, continuously improving the silicon wafer cleaning process, especially for silicon wafers without end-face treatment, to obtain wafers with high surface cleanliness remains a subject of ongoing research. Summary of the Invention
[0004] This invention proposes an organic acid cleaning method that can remove metal and organic contaminants to a certain extent, and improve the particle level on the silicon wafer surface. It is particularly suitable for cleaning silicon wafers without end face treatment.
[0005] This application provides a cleaning method for silicon wafers without end-face processing, comprising the following steps:
[0006] 1) The silicon wafer is cleaned with pure water to obtain the first silicon wafer;
[0007] 2) The first silicon wafer is cleaned with the first chemical solution to obtain the second silicon wafer. The first chemical solution is a mixture of NH4OH, H2O2 and H2O.
[0008] 3) Clean the second silicon wafer with pure water to obtain the third silicon wafer;
[0009] 4) Clean the third silicon wafer with the second chemical solution to obtain the fourth silicon wafer. The second chemical solution is an acetic acid solution.
[0010] 5) Clean the fourth silicon wafer with pure water, spin dry, and obtain a clean silicon wafer.
[0011] The beneficial effects of this application include, but are not limited to: using organic acids (acetic acid) for silicon wafer cleaning has the following advantages: ① ensuring the removal of both metal and organic contaminants; ② applicable to all types of silicon wafer cleaning, especially silicon wafers without end face treatment, as it does not react with the SiO2 layer at the edge of the silicon wafer chamfer, reducing particulate contamination; ③ other organic acid-based cleaning methods focus on removing metal from the silicon wafer surface and are costly, usually requiring composite formulations, while this invention focuses on exploring the particulate removal of organic acids, is low-cost, and can achieve the desired effect with acetic acid alone. Attached Figure Description
[0012] This application will be further described by way of exemplary embodiments, which will be described in detail with reference to the accompanying drawings. These embodiments are not limiting, wherein:
[0013] Figure 1 Data on silicon wafer particles measured for SP-1.
[0014] Figure 2 Data on silicon wafer metal levels as determined by ICP-MS. Detailed Implementation
[0015] To more clearly illustrate the technical solutions of the embodiments in this specification, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are merely some examples or embodiments of this specification. For those skilled in the art, these drawings can be applied to other similar scenarios without creative effort. Unless obvious from the context or otherwise specified, the same reference numerals in the drawings represent the same structures or operations.
[0016] As indicated in this specification and claims, unless the context clearly indicates otherwise, the words "a," "an," "an," and / or "the" do not specifically refer to the singular and may also include the plural. Generally speaking, the terms "comprising" and "including" only indicate the inclusion of expressly identified steps and elements, which do not constitute an exclusive list, and the method or apparatus may also include other steps or elements.
[0017] Flowcharts are used in this specification to illustrate the operations performed by the system according to embodiments of this specification. It should be understood that the preceding or following operations are not necessarily performed in exact order. Instead, the steps can be processed in reverse order or simultaneously. Furthermore, other operations can be added to these processes, or one or more steps can be removed from them.
[0018] This application provides a cleaning method for silicon wafers without end-face processing, comprising the following steps:
[0019] 1) The silicon wafer is cleaned with pure water to obtain the first silicon wafer;
[0020] 2) The first silicon wafer is cleaned with the first chemical solution to obtain the second silicon wafer. The first chemical solution is a mixture of NH4OH, H2O2 and H2O.
[0021] 3) Clean the second silicon wafer with pure water to obtain the third silicon wafer;
[0022] 4) Clean the third silicon wafer with the second chemical solution to obtain the fourth silicon wafer. The second chemical solution is an acetic acid solution.
[0023] 5) Clean the fourth silicon wafer with pure water, spin dry, and obtain a clean silicon wafer.
[0024] In some embodiments, the cleaning can be performed in a tank cleaning machine.
[0025] In some embodiments, during pure water rinsing in step 1), the overflow rate of the pure water in the pure water rinsing tank can be 1000–1100 L / h. For example, during pure water rinsing in step 1), the overflow rate of the pure water in the pure water rinsing tank can be 1000, 1010, 1020, 1030, 1040, 1050, 1060, 1070, 1080, 1090, 1000, or 1100 L / h. Any range characterized by combinations of the above values is also included, which will not be elaborated here.
[0026] In some embodiments, in step 2), the volume ratio of NH4OH, H2O2, and H2O can be 1:1:5 to 1:1:7. In some embodiments, in step 2), the volume ratio of NH4OH, H2O2, and H2O can be 1:1:6 to 1:1:7.
[0027] In some embodiments, the operating temperature of the first liquid medicine in step 2) can be 60–70°C. For example, in step 2), the operating temperature of the first liquid medicine can be 60, 62, 64, 66, 68, or 70°C. It also includes any range characterized by combinations of the above-mentioned values, which will not be elaborated here.
[0028] In some embodiments, in step 2), cleaning can be assisted by acoustic waves with a power of 400 to 800 MHz. For example, in step 2), cleaning can be assisted by acoustic waves with power of 400, 420, 440, 460, 480, 500, 520, 540, 560, 580, 600, 620, 640, 660, 680, 700, 720, 740, 760, 780, or 800 MHz. Any range characterized by combinations of the above-mentioned values is also included, which will not be elaborated here.
[0029] In some embodiments, in step 2), the cleaning may be repeated 1 to 3 times in different cleaning tanks. In some embodiments, in step 2), the cleaning may be repeated 1 to 2 times in different cleaning tanks.
[0030] In some embodiments, during pure water rinsing in step 3), the overflow rate of the pure water in the pure water rinsing tank can be 1000–1100 L / h. For example, during pure water rinsing in step 3), the overflow rate of the pure water in the pure water rinsing tank can be 1000, 1010, 1020, 1030, 1040, 1050, 1060, 1070, 1080, 1090, 1000, or 1100 L / h. Any range characterized by combinations of the above values is also included, which will not be elaborated here.
[0031] In some embodiments, the concentration of the acetic acid solution in step 4) can be 0.5% to 1%. For example, in step 4), the concentration of the acetic acid solution can be 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, or 1%. Any range characterized by combinations of the above values is also included, which will not be elaborated here.
[0032] In some embodiments, the acetic acid solution may be an aqueous solution of acetic acid.
[0033] In some embodiments, step 4) can be a room temperature cleaning process without overflow.
[0034] In some embodiments, during pure water rinsing in step 5), the overflow rate of the pure water in the pure water rinsing tank can be 1000–1100 L / h. For example, during pure water rinsing in step 5), the overflow rate of the pure water in the pure water rinsing tank can be 1000, 1010, 1020, 1030, 1040, 1050, 1060, 1070, 1080, 1090, 1000, or 1100 L / h. Any range characterized by combinations of the above values is also included, which will not be elaborated here.
[0035] In some embodiments, in step 5), the cleaning may be repeated 1 to 3 times in different cleaning tanks. In some embodiments, in step 5), the cleaning may be repeated 1 to 2 times in different cleaning tanks.
[0036] In some embodiments, the cleaning time for each cycle can be 240s to 270s. For example, the cleaning time for each cycle can be 240s, 245s, 250s, 255s, 260s, 265s, or 270s.
[0037] This invention proposes a cleaning method applicable to all types of silicon wafers, especially for cleaning silicon wafers without end face treatment, ensuring the removal of metal, organic matter and particulate contaminants from the silicon wafers, resulting in silicon wafers with high surface cleanliness.
[0038] Using DHF as a control, washing process experiments were conducted using 0.5% and 1% acetic acid concentrations to compare the particle improvement effect and optimal process conditions of the acetic acid process.
[0039] Table 1
[0040] Experimental sequence Classification Cleaning process 1 Original process DHF 2 New process 1 0.5% HAC 3 New process 2 1% HAC
[0041] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the experimental materials used in the following examples were all purchased from conventional biochemical reagent companies. All quantitative experiments in the following examples were performed in triplicate, and the results were averaged.
[0042] Example
[0043] (1) The following is the cleaning process of silicon wafers in the cleaning machine:
[0044] Silicon wafers were cleaned using a fully automated tank cleaning machine. The cleaning process in tank 6 was modified by replacing hydrofluoric acid with acetic acid of different concentrations. The following three sets of cleaning processes were performed sequentially:
[0045] Table 2
[0046]
[0047] Notes: DIW: Overflow pure water; SC-1: NH4OH + H2O2; DHF: 0.02% HF; HAc :acetic acid
[0048] Original process: 2-bacth silicon wafers are placed into the loading end of a fully automatic tank-type cleaning machine. A robotic arm sequentially clamps the wafers into the cleaning tanks. The wafers are then cleaned by levers within the tanks to ensure thorough contact with the cleaning solution. The DIW tank has a pure water overflow rate of 1000-1100 L / h; the SC-1 tank operates at 60-70℃ and is equipped with 400-800 MHz ultrasonic-assisted cleaning, using NH4OH:H2O2:H2O = 1:1:5 to 1:1:7; the 6th tank automatically prepares 0.02% HF solution for room temperature cleaning without overflow; the cleaning time for each tank is 240-270 seconds; after cleaning and drying, the wafers in tanks 7-9 are collected in the unloading tank for particle and metal testing.
[0049] New Process 1: Place 2-bacth silicon wafers into the loading end of a fully automatic tank-type cleaning machine. A robotic arm sequentially clamps the wafers into the cleaning tanks. A rocker arm within the tank drives the wafers to fully contact the cleaning solution for cleaning. The DIW tank has a pure water overflow rate of 1000-1100 L / h; the SC-1 tank operates at 60-70℃ and is equipped with 400-800 MHz ultrasonic-assisted cleaning, using NH4OH:H2O2:H2O = 1:1:5 to 1:1:7; the 6th tank is manually prepared with 0.5% HAc, cleaned at room temperature without overflow; the cleaning time for each tank is 240-270 seconds; after cleaning and drying, the silicon wafers are collected in the unloading tank for particle and metal testing.
[0050] New Process 2: 2-bacushion silicon wafers are placed into the loading end of a fully automatic tank-type cleaning machine. A robotic arm sequentially clamps the wafers into the cleaning tanks, and a rocker arm within the tank ensures thorough contact between the wafers and the cleaning solution. The DIW tank has a pure water overflow rate of 1000-1100 L / h; the SC-1 tank operates at 60-70℃ and is equipped with 400-800 MHz ultrasonic-assisted cleaning, using NH4OH:H2O2:H2O = 1:1:5 to 1:1:7; the 6th tank is manually prepared with 1% HAc and cleaned at room temperature without overflow; the cleaning time for each tank is 240-270 seconds; after cleaning and drying, the silicon wafers are collected in the unloading tank for particle and metal testing.
[0051] (2) Experimental results:
[0052] Particle data determined by SP-1 (see...) Figure 1 It can be concluded that:
[0053] The HAc group had lower particle sizes across all sizes than the DHF group, with the 0.5% HAc group having the lowest particle levels, and its 0.12-0.3µm particle levels being almost half that of the DHF group.
[0054] ICP-MS determination of metal levels (see) Figure 2 It can be concluded that:
[0055] Both 0.5% and 1% HAc concentrations can effectively maintain the concentration of various metal elements at 1E10 Atoms / cm². 2 Within this range, there is no significant difference compared to DHF cleaning.
[0056] Contact angle level (see Table 3):
[0057] Acetic acid can effectively remove organic contaminants from the surface of silicon wafers, making the surface of silicon wafers hydrophilic.
[0058] Table 3
[0059] Sample Name Average contact angle (°) 1% HAC 2.995 0.5% HAC 2.988
[0060] In summary, acetic acid cleaning is a cleaning method suitable for all types of silicon wafers, especially for silicon wafers without end face treatment. At the small particle level, it is almost half the cleaning efficiency of DHF cleaning, and can effectively ensure the removal of silicon wafer metals and organic matter, resulting in silicon wafers with high surface cleanliness.
[0061] The basic concepts have been described above. Obviously, for those skilled in the art, the detailed disclosure above is merely illustrative and does not constitute a limitation of this specification. Although not explicitly stated herein, those skilled in the art may make various modifications, improvements, and corrections to this specification. Such modifications, improvements, and corrections are suggested in this specification and therefore remain within the spirit and scope of the exemplary embodiments described herein.
[0062] Furthermore, this specification uses specific terms to describe embodiments thereof. For example, "an embodiment," "one embodiment," and / or "some embodiments" refer to a particular feature, structure, or characteristic associated with at least one embodiment of this specification. Therefore, it should be emphasized and noted that references to "an embodiment," "one embodiment," or "an alternative embodiment" in different locations throughout this specification do not necessarily refer to the same embodiment. Moreover, certain features, structures, or characteristics in one or more embodiments of this specification can be appropriately combined.
[0063] In some embodiments, numbers describing the quantity of components and attributes are used. It should be understood that such numbers used in the description of embodiments are modified in some examples with the terms "approximately," "approximately," or "generally." Unless otherwise stated, "approximately," "approximately," or "generally" indicates that the numbers are allowed to vary by ±20%. Accordingly, in some embodiments, the numerical parameters used in the specification and claims are approximate values, which may be changed depending on the characteristics required by individual embodiments. In some embodiments, numerical parameters should take into account specified significant digits and employ a general method of digit reservation. Although the numerical ranges and parameters used to confirm their breadth of range in some embodiments of this specification are approximate values, in specific embodiments, such values are set as precisely as feasible.
[0064] Finally, it should be understood that the embodiments described in this specification are merely illustrative of the principles of the embodiments described herein. Other variations may also fall within the scope of this specification. Therefore, alternative configurations of the embodiments described herein are intended to be illustrative rather than limiting, and should be considered consistent with the teachings of this specification. Accordingly, the embodiments described herein are not limited to those explicitly introduced and described herein.
Claims
1. A cleaning method for silicon wafers without end-face processing, characterized in that, Includes the following steps: 1) The silicon wafer is cleaned with pure water to obtain the first silicon wafer; 2) The first silicon wafer is cleaned with the first chemical solution to obtain the second silicon wafer. The first chemical solution is a mixture of NH4OH, H2O2 and H2O. 3) Clean the second silicon wafer with pure water to obtain the third silicon wafer; 4) Clean the third silicon wafer with the second chemical solution to obtain the fourth silicon wafer. The second chemical solution is an acetic acid solution. 5) Clean the fourth silicon wafer with pure water, spin dry, and obtain a clean silicon wafer.
2. The cleaning method as described in claim 1, characterized in that, The cleaning is carried out in a trough-type cleaning machine.
3. The cleaning method as described in claim 1, characterized in that, In step 1), during pure water cleaning, the pure water overflow rate of the pure water cleaning tank is 1000-1100 L / h.
4. The cleaning method as described in claim 1, characterized in that, In step 2), the volume ratio of NH4OH, H2O2 and H2O is 1:1:5 to 1:1:
7. And / or, in step 2), the working temperature of the first liquid is 60-70°C.
5. The cleaning method as described in claim 1, characterized in that, In step 2), the cleaning is assisted by acoustic waves with a power of 400-800 MHz. And / or, in step 2), the cleaning is repeated 1 to 3 times in different cleaning tanks.
6. The cleaning method as described in claim 1, characterized in that, In step 3), during pure water cleaning, the pure water overflow rate of the pure water cleaning tank is 1000-1100 L / h.
7. The cleaning method as described in claim 1, characterized in that, In step 4), the concentration of the acetic acid solution is 0.5% to 1%.
8. The cleaning method as described in claim 1, characterized in that, In step 4), the cleaning is performed at room temperature with no overflow.
9. The cleaning method as described in claim 1, characterized in that, In step 5), during pure water cleaning, the pure water overflow rate of the pure water cleaning tank is 1000-1100 L / h. And / or, in step 5), the cleaning is repeated 1 to 3 times in different cleaning tanks.
10. The cleaning method as described in claim 1, characterized in that, Each cleaning session lasts 240 to 270 seconds.