CN115295400A - Chemical cleaning method for particles and metal residues on surface of groove type compound wafer - Google Patents
Chemical cleaning method for particles and metal residues on surface of groove type compound wafer Download PDFInfo
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- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 40
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 28
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/02041—Cleaning
- H01L21/02043—Cleaning before device manufacture, i.e. Begin-Of-Line process
- H01L21/02052—Wet cleaning only
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- Condensed Matter Physics & Semiconductors (AREA)
- General Physics & Mathematics (AREA)
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Abstract
The invention relates to a chemical cleaning method for particles and metal residues on the surface of a tank type compound wafer, which comprises the steps of sequentially carrying out acid cleaning, SPM cleaning, HQDR cleaning, SC1 cleaning, QDR cleaning, SC2 cleaning, QDR cleaning, DHF cleaning, HQDR cleaning, HOFR cleaning and drying on the wafer. According to the invention, by optimally designing each flow, the cleaning flow is short, and the operation is simple and convenient; the invention can remove particles with different sizes step by step, grading and step by step, reduce the residual quantity of surface particles, dirt and metal residues and greatly improve the quality of the wafer. Finally, the following steps can be achieved: the total metal content of the cleaned wafer surface is less than or equal to 2E10atomS/cm < 2 >, and the metals comprise 16 types (Na, al, K, ca, ti, cr, mn, fe, co, ni, cu, zn, au, ag, V and Hg).
Description
Technical Field
The invention relates to a chemical cleaning method for particles and metal residues on the surface of a groove type compound wafer, belonging to the technical field of chemical cleaning of wafers.
Background
The cleaning method of semiconductor wafer usually adopts chemical method to clean, chemical cleaning refers to a process of utilizing various chemical reagents and organic solvents to react with impurities and oil stains adsorbed on the surface of the cleaned wafer or dissolve the impurities, so that the impurities are desorbed from the surface of the cleaned wafer, and then washing the wafer with a large amount of high-purity hot and cold deionized water, so as to obtain a clean surface. The chemical cleaning can be divided into wet chemical cleaning and dry chemical cleaning, wherein the wet chemical cleaning is still dominant in the semiconductor cleaning process.
Wet chemical cleaning includes solution immersion
(1) Solution soaking method. The solution immersion method is a method of immersing a wafer in a chemical solution to remove surface contamination. It is one of the most common methods used in wet chemical cleaning. Different solutions are selected to remove different types of pollution impurities on the surface of the wafer, for example, organic solvents are adopted to remove organic pollutants, and RCA solutions are adopted to remove organic, inorganic, metal ion and other impurities. Usually, this method cannot completely remove impurities on the wafer surface, so the soaking is usually assisted by physical measures such as heating, ultrasound, stirring, etc.
(2) And (4) ultrasonic cleaning. Ultrasonic cleaning is a cleaning method widely applied in the semiconductor industry, and has the advantages that: the cleaning effect is good, the operation is simple, and complex devices and containers can be cleaned. In the cleaning method, under the action of strong ultrasonic waves (the common ultrasonic frequency is 20-40 kHz), a sparse part and a dense part are generated in a liquid medium, the sparse part generates cavity bubbles which are nearly vacuum, and when the cavity bubbles disappear, strong local pressure is generated nearby the cavity bubbles, so that chemical bonds in molecules are broken, and impurities on the surface of a wafer are desorbed. The effect of ultrasonic cleaning is related to ultrasonic conditions (such as temperature, pressure, ultrasonic frequency, power, etc.), and is mostly used for removing bulk contamination and particles attached to the wafer surface.
(3) And (5) megasonic cleaning. Megasonic cleaning not only has the advantages of ultrasonic cleaning, but also overcomes the disadvantages thereof. Megasonic cleaning is the cleaning of wafers by the high energy (850 kHz) frequency vibration effect combined with the chemical reaction of chemical cleaning agents. During cleaning, solution molecules are driven by megasonic waves to do accelerated motion (the maximum instantaneous speed can reach 30 cm/s), and the solution molecules continuously impact the surface of the wafer by high-speed fluid waves, so that pollutants and fine particles attached to the surface of the wafer are forcibly removed and enter the cleaning solution. The method can simultaneously play the roles of a mechanical wiping piece and a chemical cleaning method. Currently, megasonic cleaning has become an effective method for cleaning polishing pads.
However, the cleaning methods are all single; therefore, it is necessary to develop a new cleaning method combining a plurality of cleaning methods.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a chemical cleaning method for particles and metal residues on the surface of a groove type compound wafer, and the specific technical scheme is as follows:
the chemical cleaning method of the groove type compound wafer surface particles and metal residues comprises the following steps:
sequentially carrying out acid washing, SPM cleaning, HQDR cleaning, SC1 cleaning, QDR cleaning, SC2 cleaning, QDR cleaning, DHF cleaning, HQDR cleaning, HOFR cleaning and drying on the wafer;
the cleaning solution for acid cleaning is sulfuric acid solution;
the cleaning liquid cleaned by the SPM is a mixed liquid of sulfuric acid and hydrogen peroxide;
the cleaning liquid for cleaning the HQDR is hot deionized water;
the cleaning solution for cleaning the SC1 is a mixed solution of ammonia water, hydrogen peroxide and water;
the cleaning solution for cleaning the QDR is deionized water;
the cleaning solution for cleaning the SC2 is a mixed solution of hydrochloric acid, hydrogen peroxide and water;
the cleaning liquid for cleaning the DHF is hydrofluoric acid;
and the cleaning solution for HOFR cleaning is deionized water.
As an improvement of the technical scheme, the pickling temperature is 100-150 ℃, the SPM cleaning temperature is 100-150 ℃, the HQDR cleaning temperature is 60-80 ℃, the SC1 cleaning temperature is 60-95 ℃, the QDR cleaning temperature is 15-25 ℃, the SC2 cleaning temperature is 60-95 ℃, the DHF cleaning temperature is 15-25 ℃, and the HOFR cleaning temperature is 60-80 ℃.
As an improvement of the technical scheme, a cleaning solution circulation mode is adopted for the acid washing, the SPM cleaning, the SC1 cleaning, the SC2 cleaning and the DHF cleaning, a filter is adopted for filtering in the cleaning solution circulation process, and an online concentration meter is adopted for monitoring the concentration of the cleaning solution online; and when the concentration of the cleaning liquid is lower than a set value, replenishing the cleaning liquid by adopting a quantitative pump. Besides the fixed displacement pump, a flow meter or a weighing type method can be adopted.
As an improvement of the above technical solution, the cleaning manner of the SC1 cleaning employs a multi-frequency ultrasonic cleaning having a plurality of resonance frequencies.
As an improvement of the above technical solution, the SC2 cleaning and the HOFR cleaning both adopt megasonic cleaning.
As an improvement of the technical scheme, the drying temperature is 30-80 ℃.
As an improvement of the technical scheme, in the cleaning solution for SC2 cleaning, the volume ratio of hydrogen chloride, hydrogen peroxide and water is 1.1 (11-13).
As an improvement of the above technical solution, a washing tank for QDR washing is provided with a rotation mechanism for rotating a washing basket.
As an improvement of the technical scheme, the complex frequency ultrasonic cleaning has two resonance frequencies which are 51.3kHz and 81.2kHz respectively.
As an improvement of the technical scheme, the megasonic cleaning frequency is 950-1000 kHz.
All cleaning liquids have an online concentration analysis function, for example, an online concentration meter is adopted to monitor the concentration of the cleaning liquid online; when the concentration of the cleaning liquid is lower than the set value, the quantitative pump is adopted to supplement the cleaning liquid (if the cleaning liquid is hydrofluoric acid, when the cleaning liquid needs to be supplemented, the quantitative pump is used to supplement the high-concentration hydrofluoric acid), so that the uniformity of the concentration of the cleaning liquid in the process tank is ensured, and the yield of the wafer is increased. The conventional method utilizes the cleaning time and batch time to perform quantitative and timed replenishment, so that the concentration of the cleaning solution is not uniform in the later period, thereby causing the yield of the wafer to be reduced.
1. The invention preferentially adopts acid cleaning which can remove organic matters and partial inorganic matters on the surface of the wafer.
2. In the invention, SPM is adopted for cleaning and removing most organic pollutants on the surface of the wafer, especially the organic film, so that other subsequent cleaning liquids can further clean the surface of the wafer deeply.
The cleaning liquid cleaned by the SPM is a mixed liquid of sulfuric acid and hydrogen peroxide; preferably, the sulfuric acid with the mass fraction of 98% is mixed with the hydrogen peroxide with the mass fraction of 30% in proportion, such as the mixture according to the volume ratio of 5. In the present invention, the temperature of the SPM cleaning is preferably 100 to 150 ℃. In the present invention, the wafer is preferably circularly rinsed by a circulation pump in the SPM cleaning process.
3. The HQDR cleaning effect is more effective than that of QDR cleaning at normal temperature, and the water cleaning effect is improved more quickly. In the invention, the HQDR cleaning is used for washing away large particles oxidized in the SPM cleaning process, such as removing particles larger than 5 μm, and washing away residual SPM residual liquid and dirty particles. Meanwhile, due to the design of the subsequent process, the cleaning effect is improved without using ultrasonic waves in the step, and even if some dirty areas with larger areas possibly exist, the dirty areas can be cleaned in the subsequent cleaning. The cleaning temperature is preferably 60-80 ℃, and the cleaning time is 5 min.
The temperature of the HQDR bath after the SPM cleaning process also has an important role in preventing the wafer from being transferred from the high-temperature SPM bath to the QDR bath having too large temperature difference, so as to prevent the wafer from being cracked due to the instantaneous temperature difference change, thereby increasing the temperature of water.
4. In the invention, the SC1 cleaning is micro-etching and complexing cleaning. In the invention, the temperature of the SC1 cleaning is preferably 60-95 ℃; the cleaning effect is obviously superior to that of the conventional ultrasonic cleaning by adopting the complex frequency ultrasonic cleaning; the cleaning frequency is preferably 40 to 200kHz.
In the present invention, the SC1 cleaning is capable of slowly dissolving the dirt particles, mainly removing particles with a particle size greater than 0.5 μm; accordingly, the number of particles having a particle diameter of less than 0.5 μm is also increased; because of the complex reaction, some metals can be effectively removed, and a clean oxide layer is formed.
In the present invention, the hydrophobic organic film still exists on the wafer surface after the SPM cleaning, which cannot be completely cleaned by the HQDR cleaning. Only through the combination of SC1 cleaning and multi-frequency ultrasonic cleaning, the cleaning agent has super strong cleaning effect on removing organic films on the surface and adhering dirt, and particularly for a wafer with serious organic pollution, the cleaning agent needs SPM cleaning at 100-150 ℃ and SC1 cleaning of multi-frequency ultrasonic to be combined for treatment. Megasonic cleaning cannot be adopted in the step, and if megasonic cleaning equipment is forcibly installed, particle distribution on the surface and the sub-surface of the wafer is disturbed, and the cleaning difficulty of subsequent DHF cleaning is increased.
The ultrasonic cleaning effect is critical to the selected ultrasonic frequency, the low frequency is favorable for cleaning large-particle dirty particles, and the high frequency is favorable for deep cleaning of local small particles difficult to remove. Currently, a single frequency is mostly adopted in the ultrasonic cleaning equipment for the wafer in the market.
5. In the invention, the QDR cleaning mainly removes particles with the particle size of 1-5 microns, and particularly washes away particles crushed by SC1 cleaning of multi-frequency ultrasound in the previous step. As the former process adopts SC1 cleaning of multi-frequency ultrasound, the QDR cleaning only adopts conventional cleaning to meet the cleaning requirement, and the cleaning temperature is normal temperature.
6. The cleaning effect can be further improved by performing the SC1 cleaning of the complex frequency ultrasound again and then performing the QDR cleaning again.
7. In the invention, the SC2 cleaning is ion complexing cleaning which is mainly used for generating soluble ion complex, removing alkali metal ions and metal hydroxide, and dissolving residual metal to form a protective and passivated hydrated oxide film. In the present invention, the SC2 cleaning temperature is the same as the SC1 cleaning temperature. In the invention, the SC2 cleaning is immediately carried out only by carrying out the SC1 cleaning twice without carrying out the DHF cleaning transition in the middle, so the SC2 cleaning needs to adopt the megasonic cleaning technology to further improve the cleaning effect in the invention, and if the conventional ultrasonic cleaning technology or the multi-frequency ultrasonic cleaning technology is adopted in the SC2 cleaning, the cleaning requirement can not be met.
8. After the SC2 cleaning, the QDR cleaning is mainly used to wash away the particles crushed in the previous step.
The rotary function can be added in the cleaning tank for QDR cleaning, thereby avoiding the particles from agglomerating at the edge of the wafer, simultaneously reducing the requirement on the flow rate of deionized water and reducing the expenditure of energy cost. Wherein, a washing tank for QDR washing is provided with a rotating mechanism for rotating a washing basket. When multiple wafers are cleaned simultaneously, it is often necessary to place the wafers in a cleaning basket.
9. In the invention, the DHF cleaning is micro-etching stripping cleaning, mainly carries out micro-etching on embedded dirt particles on the surface of the wafer and particles in a superficial oxidation layer on the surface, and further cleans the sub-surface of the wafer. In the invention, hydrofluoric acid can corrode the surface of the wafer, accelerate the exposure of the sub-surface of the wafer and corrode and strip the silicon dioxide thermal growth layer containing metal or nonmetal dirt.
Because the DHF cleaning is only performed on the wafer surface and then on the sub-surface of the wafer, it is very reasonable to clean the wafer surface and the sub-surface incompletely. However, it is difficult to clean the wafer surface only by performing cleaning processes such as SPM cleaning, SC1 cleaning (repeated twice), SC2 cleaning, and the like. If DHF cleaning is inserted in the repeated process of SC1 cleaning, the cleaning effect of SC1 cleaning, especially low-concentration SC1 cleaning, is reduced by the DHF cleaning due to hydrofluoric acid used in the DHF cleaning because of ammonia contained in the SC1 cleaning.
If the SC2 cleaning is carried out by ultrasonic auxiliary cleaning, local micro-etching is accelerated to generate certain micro-roughness, so that not only can the surface of the wafer be seriously corroded, but also the difficulty in removing the adhered particles on the surface is increased.
After the SC2 is cleaned, only QDR cleaning, HQDR cleaning or DIW cleaning is adopted, and the SC2 is difficult to be soaked and removed no matter whether ultrasonic-assisted cleaning is adopted or not.
10. The HQDR cleaning is firstly adopted, mainly washing away the particles generated in the previous step, and then carrying out HOFR cleaning under the action of megasonic to carry out deep cleaning. The HOFR cleaning is to continuously introduce 60-80 ℃ deionized water into an overflow groove, and the megasonic auxiliary cleaning is adopted, so that the surface of a wafer can be deeply cleaned, and particularly, the residual medicine stains in the DHF cleaning can be completely cleaned.
Compared with the QDR cleaning, the HOFR cleaning with megasonic auxiliary cleaning has better cleaning effect on the residual DHF stains on the surface of the wafer.
11. Finally, the drying temperature is 30-80 ℃, and hot nitrogen can be used for drying. Besides hot nitrogen drying, a centrifugal force spin-drying process can also be selected. The choice of drying process depends on the material and internal structure of the compound wafer.
The invention has the function of water saving and reutilization and greatly introduces the usage amount of the deionized water.
The composite technology of complex frequency ultrasound (40-200 kHz) and secondary megasonic (950-1000 kHz) is utilized, and metal particles with different particle sizes can be removed more effectively.
The cleaning solution used for cleaning is sulfuric acid solution, mixed solution of sulfuric acid and hydrogen peroxide, deionized water, mixed solution of ammonia water, hydrogen peroxide and water, mixed solution of hydrochloric acid, hydrogen peroxide and water, hydrofluoric acid and the like, and can oxidize, dissolve and complex to remove organic and inorganic pollutants and metal ions on the surface of the wafer; the unique cleaning process of the invention has good effect of removing metal particles in particular. The cleaning effect that can reach finally is:
the particle index is more than or equal to 0.2 mu m 10EA, and the particle index is more than or equal to 0.16 mu m 20EA. Wherein, 0.2 μm 10EA means that the particle contamination degree (more than or equal to 0.2 microns) on the wafer surface can be less than 10 particles/piece. The rest is analogized in the same way.
The invention has the beneficial effects that:
compared with the prior art, the cleaning method has the advantages that through the optimized design of each process, the cleaning process is short, and the operation is simple and convenient; the invention can remove particles with different sizes step by step, grading and step by step, reduce the residual quantity of surface particles, dirt and metal residues and greatly improve the quality of the wafer. Finally, the following steps can be achieved: the total metal content of the surface of the cleaned wafer is less than or equal to 2E10atomS/cm 2 The metals include 16 types (Na, al, K, ca, ti, cr, mn, fe, co, ni, cu, zn, au, ag, V, hg).
Drawings
Fig. 1 is a graph of cleaning frequency versus removal rate for cleaning process 1.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Example 1
The chemical cleaning method for the particles and the metal residues on the surface of the groove type compound wafer comprises the following steps:
the wafer is subjected to acid washing, SPM cleaning, HQDR cleaning, SC1 cleaning, QDR cleaning, SC2 cleaning, QDR cleaning, DHF cleaning, HQDR cleaning, HOFR cleaning, and drying in this order.
The cleaning solution for acid washing is sulfuric acid solution, and the temperature for acid washing is 100 ℃; the cleaning liquid for cleaning the SPM is a mixed liquid of sulfuric acid and hydrogen peroxide, and the temperature for cleaning the SPM is 100 ℃; the cleaning liquid for the HQDR cleaning is hot deionized water, and the temperature for the HQDR cleaning is 60 ℃; the cleaning solution for cleaning the SC1 is a mixed solution of ammonia water, hydrogen peroxide and water, and the cleaning temperature of the SC1 is 60 ℃; the cleaning solution for QDR cleaning is deionized water, and the temperature for QDR cleaning is 15 ℃; the cleaning solution for cleaning the SC2 is a mixed solution of hydrochloric acid, hydrogen peroxide and water, and the cleaning temperature of the SC2 is 60 ℃; the cleaning liquid for DHF cleaning is hydrofluoric acid, and the temperature for DHF cleaning is 15 ℃; the cleaning solution for HOFR cleaning is deionized water, and the cleaning temperature for HOFR cleaning is 60 ℃.
The cleaning solution circulation mode is adopted for the acid cleaning, the SPM cleaning, the SC1 cleaning, the SC2 cleaning and the DHF cleaning, a filter is adopted for filtering in the cleaning solution circulation process, and an online concentration meter is adopted for monitoring the concentration of the cleaning solution on line; and when the concentration of the cleaning liquid is lower than a set value, the cleaning liquid is supplemented by adopting a quantitative pump. The cleaning mode of SC1 cleaning adopts multi-frequency ultrasonic cleaning with a plurality of resonance frequencies. The cleaning modes of the SC2 cleaning and the HOFR cleaning are megasonic cleaning, and the volume ratio of hydrogen chloride to hydrogen peroxide to water in the cleaning solution of the SC2 cleaning is 1.1. The temperature of the drying was 30 ℃.
After cleaning, the particle on the surface of the wafer is detected to reach the particle index:
the particle index is more than or equal to 0.2 mu m 10EA, and the particle index is more than or equal to 0.16 mu m 20EA; the total metal content of the surface of the cleaned wafer is less than or equal to 2E10atomS/cm 2 The metals include 16 types (Na, al, K, ca, ti, cr, mn, fe, co, ni, cu, zn, au, ag, V, hg).
Example 2
The chemical cleaning method for the particles and the metal residues on the surface of the groove type compound wafer comprises the following steps:
the wafer is subjected to acid washing, SPM cleaning, HQDR cleaning, SC1 cleaning, QDR cleaning, SC2 cleaning, QDR cleaning, DHF cleaning, HQDR cleaning, HOFR cleaning, and drying in this order.
The cleaning solution for acid washing is sulfuric acid solution, and the temperature for acid washing is 130 ℃; the cleaning liquid for cleaning the SPM is a mixed liquid of sulfuric acid and hydrogen peroxide, and the temperature for cleaning the SPM is 130 ℃; the cleaning liquid for the HQDR cleaning is hot deionized water, and the temperature for the HQDR cleaning is 70 ℃; the cleaning solution for cleaning the SC1 is a mixed solution of ammonia water, hydrogen peroxide and water, and the cleaning temperature of the SC1 is 80 ℃; the cleaning solution for QDR cleaning is deionized water, and the temperature for QDR cleaning is 20 ℃; the cleaning solution for cleaning the SC2 is a mixed solution of hydrochloric acid, hydrogen peroxide and water, and the cleaning temperature of the SC2 is 80 ℃; the cleaning liquid for DHF cleaning is hydrofluoric acid, and the temperature for DHF cleaning is 20 ℃; the cleaning solution for HOFR cleaning is deionized water, and the cleaning temperature for HOFR cleaning is 70 ℃.
The cleaning solution circulation mode is adopted for the acid cleaning, the SPM cleaning, the SC1 cleaning, the SC2 cleaning and the DHF cleaning, a filter is adopted for filtering in the cleaning solution circulation process, and an online concentration meter is adopted for monitoring the concentration of the cleaning solution on line; and when the concentration of the cleaning liquid is lower than a set value, the cleaning liquid is supplemented by adopting a quantitative pump. The cleaning mode of SC1 cleaning adopts multi-frequency ultrasonic cleaning with a plurality of resonance frequencies. The cleaning modes of the SC2 cleaning and the HOFR cleaning are megasonic cleaning, and the volume ratio of hydrogen chloride, hydrogen peroxide and water in the cleaning solution of the SC2 cleaning is 1.1. The temperature of the drying was 60 ℃.
After cleaning, the particle on the surface of the wafer is detected to reach the particle index:
the particle index is more than or equal to 0.2 mu m 10EA, and the particle index is more than or equal to 0.16 mu m 20EA; the total metal content of the cleaned wafer surface is less than or equal to 2E10atomS/cm 2 The metals include 16 types (Na, al, K, ca, ti, cr, mn, fe, co, ni, cu, zn, au, ag, V, hg).
Example 3
The chemical cleaning method for the particles and the metal residues on the surface of the tank type compound wafer comprises the following steps:
the wafer is subjected to acid washing, SPM cleaning, HQDR cleaning, SC1 cleaning, QDR cleaning, SC2 cleaning, QDR cleaning, DHF cleaning, HQDR cleaning, HOFR cleaning, and drying in this order.
The cleaning solution for acid washing is sulfuric acid solution, and the temperature for acid washing is 150 ℃; the cleaning liquid for cleaning the SPM is a mixed liquid of sulfuric acid and hydrogen peroxide, and the temperature for cleaning the SPM is 150 ℃; the cleaning liquid for the HQDR cleaning is hot deionized water, and the temperature for the HQDR cleaning is 80 ℃; the cleaning solution for cleaning the SC1 is a mixed solution of ammonia water, hydrogen peroxide and water, and the cleaning temperature of the SC1 is 95 ℃; the cleaning solution for QDR cleaning is deionized water, and the temperature for QDR cleaning is 25 ℃; the cleaning solution for cleaning the SC2 is a mixed solution of hydrochloric acid, hydrogen peroxide and water, and the cleaning temperature of the SC2 is 95 ℃; the cleaning liquid for DHF cleaning is hydrofluoric acid, and the temperature for DHF cleaning is 25 ℃; the cleaning solution for HOFR cleaning is deionized water, and the cleaning temperature for HOFR cleaning is 80 ℃.
The cleaning solution circulation mode is adopted for the acid cleaning, the SPM cleaning, the SC1 cleaning, the SC2 cleaning and the DHF cleaning, a filter is adopted for filtering in the cleaning solution circulation process, and an online concentration meter is adopted for monitoring the concentration of the cleaning solution on line; and when the concentration of the cleaning liquid is lower than a set value, replenishing the cleaning liquid by adopting a quantitative pump. The cleaning mode of SC1 cleaning adopts multi-frequency ultrasonic cleaning with a plurality of resonance frequencies. The cleaning modes of the SC2 cleaning and the HOFR cleaning are megasonic cleaning, and the volume ratio of hydrogen chloride, hydrogen peroxide and water in the cleaning solution of the SC2 cleaning is 1.1. The temperature of the drying was 80 ℃.
After cleaning, the particle on the surface of the wafer is detected, and the particle index is reached:
the particle index is more than or equal to 0.2 mu m 10EA, and the particle index is more than or equal to 0.16 mu m 20EA; the total metal content of the surface of the cleaned wafer is less than or equal to 2E10atomS/cm 2 The metals include 16 types (Na, al, K, ca, ti, cr, mn, fe, co, ni, cu, zn, au, ag, V, hg).
Characterization test of particle cleaning Effect
1. A wafer to be cleaned was prepared by coating a 6-inch wafer with 40nm (60, 80, 100, 200 nm) polystyrene latex particles.
2. Cleaning according to different cleaning processes, wherein the cleaning time is 1h.
3. The removal rate was calculated from the number of particles on the wafer measured by the particle measuring instrument, and the values after and before cleaning.
The cleaning process 1: SC1 cleaning is adopted, ultrasonic auxiliary cleaning is adopted during cleaning, and the curve of the removal rate is shown in figure 1 under the condition that the cleaning frequency is 40-200 kHz. The 40nm curve in FIG. 1 represents the removal curve for 40nm polystyrene latex particles, and the 200nm curve in FIG. 1 represents the removal curve for 200nm polystyrene latex particles.
As can be seen from FIG. 1, the low frequency facilitates the cleaning of large particles (e.g., 200 nm), while the high frequency facilitates the deep cleaning of small particles (e.g., 40 nm) that are locally difficult to remove. As can be seen from FIG. 1, the cleaning frequency is selectable in the range of 40 to 100kHz for the overall cleaning effect.
And (3) a cleaning process 2: SC1 cleaning was used, and complex frequency ultrasonic cleaning with 2 resonance frequencies was used. The complex frequency ultrasonic cleaning has two resonance frequencies of 51.3kHz and 81.2kHz respectively. The removal rate is shown in Table 1.
TABLE 1
| Particle size | 40nm | 60nm | 80nm | 100nm | 200nm |
| Removal rate of | 98.2％ | 98.7％ | 98.5％ | 98.9％ | 99.1％ |
As can be seen from Table 1, the cleaning method can clean large-particle dirt particles and small-particle dirt particles by adopting multi-frequency ultrasonic cleaning, and has high cleaning removal rate which exceeds 98 percent.
And (3) a cleaning process: SC1 cleaning was used, and complex frequency ultrasonic cleaning with 2 resonance frequencies was used. The complex frequency ultrasonic cleaning has two resonance frequencies, the two resonance frequencies are shown in table 2, and the corresponding removal rates are also shown in table 3.
TABLE 2
TABLE 3
| Particle size | 40nm | 60nm | 80nm | 100nm | 200nm |
| Group 1 removal Rate | 85.1％ | 88.3％ | 91.5％ | 96.2％ | 97.8％ |
| Group 2 removal Rate | 86.6％ | 88.9％ | 92.1％ | 95.5％ | 97.1％ |
| Group 3 removal Rate | 88.5％ | 89.9％ | 90.2％ | 95.0％ | 95.8％ |
| Group 4 removal Rate | 81.5％ | 85.7％ | 93.8％ | 97.1％ | 96.6％ |
| Group 5 removal Rate | 90.3％ | 92.5％ | 89.8％ | 95.3％ | 96.6％ |
| Group 6 removal Rate | 86.7％ | 88.1％ | 91.5％ | 92.1％ | 93.5％ |
| Group 7 removal Rate | 93.8％ | 95.1％ | 87.3％ | 92.2％ | 90.2％ |
| Group 8 removal Rate | 95.2％ | 95.9％ | 86.2％ | 93.6％ | 91.5％ |
As can be seen from tables 2 and 3, when there are two resonant frequencies, the frequency in the low frequency band is not as low as possible, nor is it as high as possible; the lower the frequency at the high frequency band, the better, the higher the frequency. In the process of multi-frequency ultrasonic cleaning, a proper resonance frequency is searched within the range of 40-200 kHz, so that the two resonance frequencies can play a synergistic effect.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.
Claims (10)
1. The chemical cleaning method for the particles and the metal residues on the surface of the groove type compound wafer is characterized by comprising the following steps:
sequentially carrying out acid washing, SPM cleaning, HQDR cleaning, SC1 cleaning, QDR cleaning, SC2 cleaning, QDR cleaning, DHF cleaning, HQDR cleaning, HOFR cleaning and drying on the wafer;
the cleaning solution for acid washing is sulfuric acid solution;
the cleaning liquid cleaned by the SPM is a mixed liquid of sulfuric acid and hydrogen peroxide;
the cleaning liquid for cleaning the HQDR is hot deionized water;
the cleaning solution for cleaning the SC1 is a mixed solution of ammonia water, hydrogen peroxide and water;
the cleaning solution for cleaning the QDR is deionized water;
the cleaning solution for cleaning the SC2 is a mixed solution of hydrochloric acid, hydrogen peroxide and water;
the cleaning liquid for cleaning the DHF is hydrofluoric acid;
and the cleaning solution for HOFR cleaning is deionized water.
2. The method of claim 1 wherein the chemical cleaning of the surface particles and metal residues of the trench compound wafer comprises: the pickling temperature is 100-150 ℃, the SPM cleaning temperature is 100-150 ℃, the HQDR cleaning temperature is 60-80 ℃, the SC1 cleaning temperature is 60-95 ℃, the QDR cleaning temperature is 15-25 ℃, the SC2 cleaning temperature is 60-95 ℃, the DHF cleaning temperature is 15-25 ℃, and the HOFR cleaning temperature is 60-80 ℃.
3. The method of claim 1 wherein the chemical cleaning of the surface particles and metal residues of the trench compound wafer comprises: the acid washing, the SPM cleaning, the SC1 cleaning, the SC2 cleaning and the DHF cleaning all adopt a cleaning liquid circulation mode, a filter is adopted for filtering in the cleaning liquid circulation process, and an online concentration meter is adopted for monitoring the concentration of the cleaning liquid on line; and when the concentration of the cleaning liquid is lower than a set value, the cleaning liquid is supplemented by adopting a quantitative pump.
4. The method of claim 1 wherein the chemical cleaning of the surface particles and metal residues from the trench compound wafer comprises: the cleaning mode of SC1 cleaning adopts multi-frequency ultrasonic cleaning with a plurality of resonance frequencies.
5. The method of claim 1 wherein the chemical cleaning of the surface particles and metal residues from the trench compound wafer comprises: and the SC2 cleaning mode and the HOFR cleaning mode adopt megasonic cleaning.
6. The method of claim 1 wherein the chemical cleaning of the surface particles and metal residues from the trench compound wafer comprises: the drying temperature is 30-80 ℃.
7. The method of claim 1 wherein the chemical cleaning of the surface particles and metal residues of the trench compound wafer comprises: in the cleaning solution for cleaning SC2, the volume ratio of hydrogen chloride, hydrogen peroxide and water is 1.1 (11-13).
8. The method of claim 1 wherein the chemical cleaning of the surface particles and metal residues of the trench compound wafer comprises: the cleaning tank for QDR cleaning is provided with a rotation mechanism for rotating the cleaning basket.
9. The method of claim 4 further comprising the step of chemically cleaning the surface of the wafer with chemicals selected from the group consisting of: the complex frequency ultrasonic cleaning has two resonance frequencies of 51.3kHz and 81.2kHz respectively.
10. The method of claim 5 further comprising the step of chemically cleaning the surface of the wafer with chemicals selected from the group consisting of: the megasonic cleaning frequency is 950-1000 kHz.
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