CN211929444U - Semiconductor silicon chip surface cleaning mechanism - Google Patents
Semiconductor silicon chip surface cleaning mechanism Download PDFInfo
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- CN211929444U CN211929444U CN202020774497.3U CN202020774497U CN211929444U CN 211929444 U CN211929444 U CN 211929444U CN 202020774497 U CN202020774497 U CN 202020774497U CN 211929444 U CN211929444 U CN 211929444U
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- 238000004140 cleaning Methods 0.000 title claims abstract description 263
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 title claims abstract description 171
- 229910052710 silicon Inorganic materials 0.000 title claims abstract description 151
- 239000010703 silicon Substances 0.000 title claims abstract description 151
- 230000007246 mechanism Effects 0.000 title claims abstract description 24
- 239000004065 semiconductor Substances 0.000 title claims abstract description 21
- 238000005554 pickling Methods 0.000 claims abstract description 100
- 238000005406 washing Methods 0.000 claims abstract description 78
- 239000002253 acid Substances 0.000 claims abstract description 61
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 57
- 229910001868 water Inorganic materials 0.000 claims abstract description 54
- 235000012431 wafers Nutrition 0.000 claims description 137
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- 238000011010 flushing procedure Methods 0.000 claims description 2
- 239000012535 impurity Substances 0.000 abstract description 30
- 239000003513 alkali Substances 0.000 abstract description 15
- 229910021645 metal ion Inorganic materials 0.000 abstract description 14
- 239000000428 dust Substances 0.000 abstract description 5
- 239000005416 organic matter Substances 0.000 abstract 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 39
- 239000007788 liquid Substances 0.000 description 35
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- 150000004706 metal oxides Chemical class 0.000 description 16
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- 229910052751 metal Inorganic materials 0.000 description 13
- 238000006243 chemical reaction Methods 0.000 description 9
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 8
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 8
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- 150000002739 metals Chemical class 0.000 description 7
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- 229910003638 H2SiF6 Inorganic materials 0.000 description 4
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- 229910052682 stishovite Inorganic materials 0.000 description 2
- ZEFWRWWINDLIIV-UHFFFAOYSA-N tetrafluorosilane;dihydrofluoride Chemical compound F.F.F[Si](F)(F)F ZEFWRWWINDLIIV-UHFFFAOYSA-N 0.000 description 2
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Abstract
The utility model provides a semiconductor silicon wafer surface cleaning mechanism, which is at least provided with a pre-cleaning unit and an acid washing unit in sequence; the system comprises a pre-cleaning unit, an acid cleaning unit, a pre-acid cleaning unit, an alkali cleaning unit and a water tank, wherein the pre-acid cleaning unit and the alkali cleaning unit are sequentially arranged between the pre-cleaning unit and the acid cleaning unit; cleaning tanks are respectively arranged behind the pre-pickling unit, the alkaline washing unit and the acid washing unit; or the pre-pickling unit and the pickling unit are respectively provided with the cleaning tanks. The utility model discloses can reduce the dirty flower rate in silicon chip surface effectively under the prerequisite of not destroying silicon chip surface characteristic and electric characteristic to together remove micronic dust, metal ion, organic matter and other impurity that will remain on the silicon chip, improve the cleaning efficiency, guarantee cleaning quality.
Description
Technical Field
The utility model belongs to the technical field of semiconductor silicon chip washs, especially, relate to a semiconductor silicon chip surface cleaning mechanism.
Background
With the advanced process nodes of the semiconductor integrated circuit, new requirements are provided for several actual manufacturing links, and the importance of the cleaning link is increasingly prominent. The critical aspect of cleaning is that as feature sizes continue to shrink, semiconductors become more sensitive to impurity levels, which inevitably introduce contaminants such as particles, organics, metals, and oxides. In order to reduce the influence of impurities on the yield of chips, in actual production, not only the single cleaning efficiency needs to be improved, but also the cleaning is frequently performed before and after almost all the processes, the cleaning steps account for about 33% of the whole steps, and the cleaning mainly comprises a multi-step highly pollution-free cleaning procedure, including various highly clean cleaning liquid treatments, so as to remove all the pollutants on the surfaces of the chips, and enable the chips to reach the state of chip processing.
The large-size silicon wafer is the development trend of the semiconductor silicon wafer nowadays, and along with the increase of the size area of the silicon wafer, a large amount of silicon powder is generated in the cutting process, and meanwhile, the surface of the silicon wafer is extremely easy to be oxidized in air, sand slurry and water liquid to form silicon dioxide; with the increase of the content of the silicon powder, agglomerated granular silicon powder is formed in the cutting process, and the granular silicon powder and the bulk silicon powder can cause the dirty and patterned quality of the silicon wafer together with organic matters in silicon dioxide oxide and mortar and other impurities on the surface of the silicon wafer, so that the product quality is seriously influenced. Because each element and connecting line in the integrated circuit are quite fine, the existing silicon chip has high dirty-flower rate in the manufacturing process, and if the silicon chip is polluted by dust particles and metal, the functions of the circuit in the silicon chip are easily damaged, short circuit or open circuit is formed, the integrated circuit is failed, and the formation of geometric characteristics is influenced.
Therefore, how to design a cleaning mechanism and a cleaning process suitable for large-size silicon wafers in the cleaning process effectively reduces the dirty flower rate of the surfaces of the silicon wafers on the premise of not damaging the surface characteristics and the electrical characteristics of the silicon wafers, removes micro dust, metal ions, organic matters and other impurities remained on the silicon wafers together, and improves the cleaning efficiency is the key for processing the large-size silicon wafers with high quality and low cost.
SUMMERY OF THE UTILITY MODEL
The utility model provides a semiconductor silicon chip surface cleaning mechanism is particularly useful for the washing of jumbo size silicon chip, has solved the technical problem of the dirty flower rate height of silicon chip and the unclean formation of surface cleaning in the current cleaning process.
In order to solve the technical problem, the utility model discloses a technical scheme is:
a semiconductor silicon wafer surface cleaning mechanism at least sequentially comprises a pre-cleaning unit and an acid cleaning unit; wherein,
a pre-pickling unit and an alkaline washing unit are sequentially arranged between the pre-cleaning unit and the pickling unit, and the pre-pickling unit is arranged close to the pre-cleaning unit;
cleaning tanks are respectively arranged behind the pre-pickling unit, the alkaline washing unit and the acid washing unit;
or the pre-pickling unit and the pickling unit are respectively provided with the cleaning tanks.
Further, the pre-pickling unit, the alkaline washing unit and the pickling unit respectively at least comprise a pre-pickling tank, an alkaline washing tank and a pickling tank.
Furthermore, two cleaning tanks are arranged behind the pickling unit, and the cleaning tank close to the pickling unit is a quick-draining flushing tank.
Furthermore, the pre-pickling tank, the alkaline washing tank and the pickling tank are all provided with megasonic devices for emitting megasonic waves, and the megasonic frequencies in the pre-pickling tank, the alkaline washing tank and the pickling tank are the same.
Further, the megasonic frequency in the pre-pickling tank, the alkaline washing tank and the pickling tank is 860-950 kHz.
Further, heaters are arranged in the pre-pickling tank, the alkaline washing tank and the pickling tank, and the temperature of the heaters in the pre-pickling tank is different from that in the alkaline washing tank and the pickling tank.
Further, the pre-cleaning unit at least comprises a pre-cleaning tank, and the pre-cleaning tank and the cleaning tank are pure water tanks.
Furthermore, an ultrasonic device for emitting ultrasonic waves is arranged in the pre-cleaning tank, and the frequency of the ultrasonic waves in the pre-cleaning tank is less than the frequency of megasonic waves in the pre-pickling tank.
Further, the ultrasonic frequency in the pre-cleaning tank is 25-35 kHz.
Further, a drying unit is arranged behind the pickling unit, and comprises a full lifting groove and a drying groove; the full pulling groove is arranged close to the pickling unit.
Compared with the prior art, the cleaning mechanism provided by the utility model can effectively reduce the dirty flower rate of the surface of the silicon wafer and make the dirty flower rate of the silicon wafer less than 0.5% on the premise of not damaging the surface characteristics and the electrical characteristics of the silicon wafer; the residual dust, metal ions, organic matters and other impurities on the silicon wafer can be completely removed together, the cleaning quality is good, and the cleaning efficiency is high.
Drawings
Fig. 1 is a schematic structural view of a silicon wafer surface cleaning mechanism according to an embodiment of the present invention;
fig. 2 is a schematic structural diagram of a pre-cleaning unit according to an embodiment of the present invention;
FIG. 3 is a schematic structural diagram of a pre-pickling unit according to an embodiment of the present invention;
fig. 4 is a schematic structural view of a first cleaning tank according to an embodiment of the present invention;
fig. 5 is a schematic structural view of a third cleaning tank according to an embodiment of the present invention;
FIG. 6 is a schematic structural diagram of a silicon wafer surface cleaning mechanism according to another embodiment of the present invention;
FIG. 7 shows the surface topography of a silicon wafer after being cleaned by the cleaning process of the present embodiment;
FIG. 8 is a silicon wafer surface topography after cleaning using a prior art cleaning process.
In the figure:
100. pre-cleaning unit 110, pre-cleaning tank 120, and ultrasonic apparatus
200. Pre-pickling unit 210, pre-pickling tank 220, and heater
230. Megasonic device 300, alkaline washing unit 310 and alkaline washing tank
400. Pickling unit 410, pickling tank 500, cleaning tank group
510. First cleaning tank 520, second cleaning tank 530 and third cleaning tank
531. Upper groove 532, lower groove 533, spray pipe
540. No. four cleaning tank 600, drying unit 610, full pull tank
620. Drying groove
Detailed Description
The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.
The embodiment proposes a semiconductor silicon wafer surface cleaning mechanism, as shown in fig. 1, at least a pre-cleaning unit 100 and an acid cleaning unit 400 are sequentially provided, wherein a pre-acid cleaning unit 200 and a caustic cleaning unit 300 are further sequentially provided between the pre-cleaning unit 100 and the acid cleaning unit 400, a drying unit 600 is further provided after the acid cleaning unit 400, the pre-acid cleaning unit 200 is arranged close to the pre-cleaning unit 100, and the caustic cleaning unit 300 is arranged close to the acid cleaning unit 400. A cleaning tank group 500 is further arranged among the pre-pickling unit 200, the alkaline washing unit 300 and the acid washing unit 400, and a first cleaning tank 510, a second cleaning tank 520, a third cleaning tank 530 and a fourth cleaning tank 540 are respectively arranged behind the pre-pickling unit 200, the alkaline washing unit 300 and the acid washing unit 400.
Specifically, as shown in fig. 2, the pre-cleaning unit 100 at least includes a pre-cleaning tank 110 for removing silicon powder, large particles and impurities attached to the surface of the silicon wafer, and an ultrasonic device 120 for emitting ultrasonic waves is further disposed in the pre-cleaning tank 110, the pre-cleaning tank 110 is a pure water tank, i.e., a deionized water tank, and the temperature of the pure water in the pre-cleaning tank 110 is normal temperature. The ultrasonic frequency of the ultrasonic device 120 in the preliminary cleaning tank 110 is 25 to 35 kHz. Because the silicon wafer which is just cut contains a large amount of granular silicon powder on the surface and the bulk silicon powder has larger volume relative to other particle impurities, massive granules or massive metal impurities are adhered on the surface of the silicon wafer. An ultrasonic device 120 with the frequency of 25-35kHz is arranged in a pre-cleaning tank 110 of the pre-cleaning unit 100, under the action of strong ultrasonic waves, bulk particles on the surface of the silicon wafer are vibrated by sound waves, gaps are generated among silicon powder, the bulk particles and impurities and the silicon wafer, and meanwhile, the silicon powder is impacted by water flow, so that particle type and bulk type silicon powder particles, bulk pollution impurities and bulk metal particles attached to the surface of the silicon wafer are cleaned in an accelerated manner. The ultrasonic wave is arranged, so that the structure is simple, the operation is convenient, the cleaning area comprises but is not limited to the surface area of the silicon wafer, especially for cleaning large-size silicon wafers, the surface quality of the silicon wafer cannot be damaged, the pre-cleaning effect can be further improved, and the pre-cleaning efficiency is improved.
As shown in fig. 3, the pre-pickling unit 200 is mainly used to remove an oxide layer on the surface of the silicon wafer, form a substance that is easily soluble in water, and then is discharged in the first cleaning tank 510 along with pure water. The pre-pickling unit 200 comprises at least one pre-pickling tank 210, wherein the liquid medicine in the pre-pickling tank 210 is HF and H2O, wherein HF: h2The volume ratio of O is 1: 15-20, a heater 220 is required to be arranged in the pre-pickling tank 210, and the temperature of the heater 220 is kept within 25-35 ℃, so that the liquid medicine can react more fully at the temperature. HF reacts with silicon dioxide on the surface oxide layer of the silicon wafer, and the specific reaction formula is as follows:
6HF+SiO2＝H2SiF6+2H2O
H2SiF6the silicon dioxide pre-pickling solution is a substance which is easy to dissolve in water, and after being pickled in the pre-pickling tank 210, oxide layer silicon dioxide and organic stains attached to the oxide layer of the silicon dioxide can be completely removed, so that the surface cleanliness of the silicon wafer can be improved, and a good surface foundation is provided for subsequent alkali washing and acid pickling.
In order to further accelerate the reaction of the liquid medicine, a megasonic device 230 which emits megasonic waves with the frequency of 860 and 950kHz is also arranged in the pre-pickling tank 210, and the frequency of the megasonic waves emitted by the megasonic device 230 is greater than the frequency of the ultrasonic waves emitted by the ultrasonic device 120 in the pre-pickling tank 110. During cleaning, the megasonic wave of the frequency vibration pushes the liquid medicine molecules to move in an accelerated way, and the accelerated solution molecules continuously impact the surface of the wafer by high-speed fluid waves, so that the silicon dioxide of the oxide layer on the surface of the silicon wafer is fully reacted with HF to generate H which is easily dissolved in water2SiF6Thereby further effectively removing silicon dioxide on the oxide layer on the surface of the silicon chip and organic stains attached on the oxide layer of the silicon dioxide.
The cleaning mechanism provided in this embodiment gradually and layer by layer removes metal impurities and particulate impurities on the surface of the silicon wafer, and needs to sequentially perform alkali washing and acid washing on the surface of the silicon wafer after the pre-acid washing, so only HF with one component is used in the pre-acid washing unit 200, and acid solution with other components does not need to be added.
After the pre-pickling, the silicon wafer is flowed into a first cleaning tank 510 for cleaning, the first cleaning tank 510 is a pure water tank, the cleaning temperature is room temperature, and the water is stored continuously, the structure is shown in fig. 4, and the oxide layer removed by HF on the surface of the silicon wafer and organic stains attached on the silicon dioxide oxide layer are mainly removed, and the pre-pickling liquid medicine is removed at the same time.
The alkaline washing unit 300 at least comprises an alkaline washing tank 310, which is mainly used for removing part of metal particles and organic matters attached below an oxidation layer. The chemical liquid of the alkaline washing tank 310 is NH4OH、H2O2And H2Mixed liquid of O, NH4OH:H2O2:H2The volume ratio of O is 3-4:4-5:12-15, the alkali washing temperature is 45-55 ℃, the structure of the alkali washing tank is the same as that of the pre-pickling tank 210, and a heater is also arranged in the alkali washing tank 310 to ensure the liquid medicine to be clearThe washing temperature is kept within the range of 45-55 ℃; meanwhile, a megasonic device (not shown) for emitting megasonic waves is also arranged in the alkaline washing tank 310, and the frequency of the megasonic waves is the same as that of the megasonic waves in the pre-acid washing tank 210 and is 860-950 kHz. The megasonic device can further accelerate the chemical reaction of the components of the liquid medicine, namely, the liquid medicine firstly passes through H2O2Part of metal particles and organic matters are strongly oxidized, and substances after strong oxidation are NH4OH is dissolved to change partial metal particles and organic matters into water-soluble compounds, the metal removed by washing with alkali liquor is mainly Cu, and the removed metal particles and organic matters can be removed in a subsequent washing tank along with the washing of pure water.
A second cleaning tank 520 can be arranged between the alkaline cleaning unit 200 and the acid cleaning unit 300, as shown in fig. 1, the metal particles and organic matters removed by alkaline cleaning are mainly washed and discharged with pure water before the silicon wafers are acid cleaned, and the second cleaning tank 520 has the same structure as the first cleaning tank 510 and is at normal temperature. The structure can be used for instantly oxidizing and immediately cleaning without deposition, so that the crossed cleaning by liquid medicine is avoided, the residual alkali cleaning liquid medicine of the silicon wafer after alkali cleaning can be timely treated, the cleaning effect is good, and the cleaning efficiency is high.
The pickling unit 300 is mainly used for removing metal ions and metal oxides on the surface of a silicon wafer, and at least comprises a pickling tank 310, and the liquid medicine in the pickling tank 310 is HCL and H2O2And H2Mixed liquid of O, HCL, H2O2:H2The volume ratio of O is 1:1:3-5, and the pickling temperature is 45-55 ℃. The pickling tank 310 is provided with a heater and a megasonic device (not shown), the heater can ensure that the pickling temperature is constant within the range of 45-55 ℃, the megasonic frequency in the pickling tank 310 is also 860-950kHz, and the chemical reaction of the liquid medicine components, namely H, can be further accelerated2O2The metal ions are oxidized to produce metal oxides, the metal oxides react with hydrochloric acid solution to generate soluble complexes, metals removed by acid cleaning are mainly metal ions such as AL, Fe, Na and the like, and the complexes are cleaned by rapidly-washed pure water in a third cleaning tank 630.
The acid-washed silicon wafer sequentially enters a third cleaning tank 530 for rapid drainage and washing to be cleaned, and the structure of the third cleaning tank 530 comprises an upper tank 531 and a lower tank 532 which are communicated up and down as shown in fig. 5, wherein two groups of spray pipes 533 symmetrically arranged along the length direction of the upper tank 531 are arranged on the inner side of the upper tank 531 and spray towards the center of the silicon wafer to form a crossed spray mode for spraying and washing the silicon wafer; the lower tank 532 is filled with pure water as a water storage tank, and the upper tank 531 is filled with water and submerged in the silicon wafer during cleaning. During cleaning, after pure water flows for a certain time, water in the upper tank 531 quickly enters the lower tank 532 of the water storage tank, and meanwhile, the spraying pipes 533 in the upper tank 531 always perform cross spraying on the silicon wafers; and stopping spraying after a certain time of spraying, and further finishing the cleaning work of the silicon wafer. The third cleaning tank 530 is mainly used for removing residual pickling solution and residual impurities on the surface of the silicon wafer. And finally cleaning the silicon wafer in a fourth cleaning tank 540 to ensure that the surface of the silicon wafer is cleaned.
The alkaline cleaning unit 200 can also be directly fed into the acid cleaning unit 300 for treatment after the alkaline cleaning unit 200 is completed, as shown in fig. 6, the structure omits a second cleaning tank 520 arranged between the alkaline cleaning tank 210 and the acid cleaning tank 310, the alkaline cleaning unit 200 and the acid cleaning unit 300 are continuously carried out, thereby saving one-time pure water cleaning, most of metal particles and organic matters removed by the alkaline cleaning unit 200 are dissolved in water and directly deposited or removed in the alkaline cleaning tank 210, only part of the particles or organic matters are not completely removed, but then the acid cleaning solution directly carries out oxidation and acid cleaning on other metals and metal oxides on the surface of the silicon wafer to form a complex which is easily dissolved in water after the metal particles and organic matters enter the acid cleaning tank 310, meanwhile, the alkaline solution remaining on the silicon wafer is neutralized by the HCL in the acid cleaning tank 310, and the part of the particles or organic matters remaining in the alkaline cleaning is removed by the acid cleaning solution HCL in the acid cleaning tank 310, and then the metal particles and the acid cleaning solution together with the other metals and metal oxides removed are 540, the impurities on the surface of the silicon wafer can still be completely removed, and the silicon wafer with a clean surface can be obtained.
And finally, drying and dehydrating in a drying unit 600, wherein the drying unit 600 is sequentially provided with a full lifting groove 610 and a drying groove 620, the slow lifting groove 610 is a pure water groove, and the silicon wafer is slowly driven to be lifted upwards so that a water film on the surface of the silicon wafer naturally flows down and the watermark is prevented from being formed on the surface of the silicon wafer after the silicon wafer is dried. After the slow pulling groove 610 is cleaned, the silicon wafer is moved into the drying groove 620 to be dried, the drying groove 620 is arranged to completely dry the silicon wafer, the whole drying process is in a high-purity nitrogen atmosphere, and finally the silicon wafer with clean surface quality and qualified product quality is obtained.
During operation, the pre-cleaning unit 100 mainly removes silicon powder, large particles and impurities attached to the surface of the silicon wafer; the pre-pickling unit 200 mainly uses HF to remove an oxide layer on the surface of the silicon wafer to form a substance easily soluble in water, and then is discharged along with pure water in the first cleaning tank 510; the alkaline washing unit 300 is mainly used for removing part of metal particles and organic matters below an oxidation layer, namely, firstly H is passed2O2Part of metal particles and organic matters are strongly oxidized, and substances after strong oxidation are NH4OH is dissolved, so that part of metal particles and organic matters are changed into water-soluble compounds, and can be removed along with the washing of pure water in the second cleaning tank 520; the pickling unit 400 is mainly used to remove metal ions and metal oxides, i.e., H, from the surface of the silicon wafer2O2Oxidizing metal ions to produce metal oxides, reacting the metal oxides with hydrochloric acid solution to generate soluble complexes, and then cleaning the soluble complexes by rapidly washing pure water in a third cleaning tank 530 to remove liquid medicine and residual impurities on the surface of the silicon wafer; then the silicon wafer enters a fourth cleaning tank 540 for final cleaning so as to ensure that the surface of the silicon wafer is cleaned; and finally, drying and dehydrating in a drying unit 600 to obtain the silicon wafer with clean surface quality and qualified product quality.
After being cleaned by the alkaline cleaning unit 300, the silicon wafer can also directly enter the acid cleaning unit 400 for continuous acid cleaning, then sequentially enter the third cleaning tank 530 for quick washing and the fourth cleaning tank 540 for final cleaning, and then enter the drying unit 600 for drying and dehydration, so that the required silicon wafer can be obtained.
A semiconductor silicon wafer surface cleaning process adopts the cleaning mechanism and comprises the following steps:
the first step is as follows: the silicon wafer is pre-cleaned in the pre-cleaning unit 10 to remove silicon powder, large particles and impurities attached to the surface of the silicon wafer.
Specifically, as shown in fig. 2, the pre-cleaning tank 110 of the pre-cleaning unit 100 is a pure water tank, and the temperature of the pure water is normal temperature; an ultrasonic device 120 for emitting ultrasonic waves is provided in the preliminary cleaning tank 110, and the frequency of the ultrasonic waves in the ultrasonic device 120 is 25 to 35 kHz. Because the silicon wafer which is just cut contains a large amount of granular silicon powder on the surface and the bulk silicon powder has larger volume relative to other particle impurities, massive granules or massive metal impurities are adhered on the surface of the silicon wafer. An ultrasonic device 120 with the frequency of 25-35kHz is arranged in the pre-cleaning tank 110, under the action of strong ultrasonic waves, bulk particles on the surface of the silicon wafer are vibrated by sound waves, gaps are generated among silicon powder, the bulk particles and impurities and the silicon wafer, and meanwhile, the silicon powder, the bulk contamination impurities and the bulk metal particles are impacted by water flow, so that the particle type and bulk type silicon powder particles, the bulk contamination impurities and the bulk metal particles attached to the surface of the silicon wafer are cleaned in an accelerated manner. The arrangement of the ultrasonic device 120 is simple in structure and convenient to operate, the cleaning area includes but is not limited to the surface area of the silicon wafer, and especially for cleaning large-size silicon wafers, the surface quality of the silicon wafer cannot be damaged, the pre-cleaning effect can be further improved, and the pre-cleaning efficiency is improved.
The second step is that: pre-pickling is performed in the pre-pickling unit 200 to remove an oxide layer on the surface of the silicon wafer to form a substance easily soluble in water, and then discharged in the first cleaning tank 510 along with pure water.
Specifically, as shown in FIG. 3, the liquid in the pre-pickling tank 210 is HF and H2O, wherein HF: h2The volume ratio of O is 1: 15-20. The heater 220 is provided in the pre-pickling tank 210 to maintain the temperature within 25-35 c, which allows the solution to react more fully. HF reacts with silicon dioxide on the surface oxide layer of the silicon wafer, and the specific reaction formula is as follows:
6HF+SiO2＝H2SiF6+2H2O
H2SiF6is a substance which is easy to dissolve in water, and can completely remove the silicon dioxide of the oxide layer and the organic stains attached on the silicon dioxide oxide layer after being acid-washed by the liquid medicine in the pre-pickling tank 210, thereby improving the silicon qualityThe cleanliness of the surface of the sheet provides a good surface foundation for subsequent alkali washing and acid washing.
In order to further accelerate the reaction of the liquid medicine, a megasonic device 230 which emits megasonic waves with the frequency of 860-950kHz is also arranged in the pre-pickling tank 210, when cleaning, the megasonic waves with the frequency can push the liquid medicine molecules to move in an accelerated way, the accelerated solution molecules continuously impact the surface of the wafer with high-speed fluid waves, so that the silicon dioxide of the oxide layer on the surface of the wafer is fully reacted with HF to generate H which is easily dissolved in water2SiF6Thereby further effectively removing silicon dioxide on the oxide layer on the surface of the silicon chip and organic stains attached on the oxide layer of the silicon dioxide.
After the pre-pickling, the silicon wafer is washed by flowing into a first washing tank 510 for washing in pure water at room temperature, as shown in fig. 4, mainly to remove the oxide layer removed by HF and the organic stains attached to the oxide layer of silicon dioxide on the surface of the silicon wafer, and simultaneously to remove the pre-pickling chemical.
The third step: an alkaline wash is performed in the alkaline wash unit 300 to remove a portion of the metal particles and organics below the oxide layer.
Specifically, the chemical solution of the alkaline washing tank 310 is NH4OH、H2O2And H2Mixed liquid of O, NH4OH:H2O2:H2The volume ratio of O is 3-4:4-5:12-15, the alkaline washing temperature is 45-55 ℃, the structure of the alkaline washing tank is the same as that of the pre-pickling tank 210, and a heater is also arranged in the alkaline washing tank 310 to ensure that the cleaning temperature of the liquid medicine is kept within the range of 45-55 ℃; meanwhile, a megasonic device for emitting megasonic waves is also arranged in the alkaline washing tank 310, and the frequency of the megasonic waves is the same as that of the pre-acid washing tank 210 and is 860-950 kHz. The megasonic device can further accelerate the chemical reaction of the components of the liquid medicine, namely, the liquid medicine firstly passes through H2O2Part of metal particles and organic matters are strongly oxidized, and substances after strong oxidation are NH4OH is dissolved to change partial metal particles and organic matters into water-soluble compounds, the metal removed by washing with alkali liquor is mainly Cu, and the removed metal particles and organic matters can be removed in a subsequent washing tank along with the washing of pure water.
A second cleaning tank 520 can be arranged between the alkaline cleaning unit 200 and the acid cleaning unit 300, as shown in fig. 1, the metal particles and organic matters removed by alkaline cleaning are mainly washed and discharged with pure water before the silicon wafers are acid cleaned, and the second cleaning tank 520 has the same structure as the first cleaning tank 510 and is at normal temperature. The structure can be used for instantly oxidizing and immediately cleaning without deposition, so that the crossed cleaning by liquid medicine is avoided, the residual alkali cleaning liquid medicine of the silicon wafer after alkali cleaning can be timely treated, the cleaning effect is good, and the cleaning efficiency is high.
The alkaline cleaning unit 200 can also be directly fed into the acid cleaning unit 300 for treatment after the alkaline cleaning unit 200 is completed, as shown in fig. 6, the structure omits a second cleaning tank 520 arranged between the alkaline cleaning tank 210 and the acid cleaning tank 310, the alkaline cleaning unit 200 and the acid cleaning unit 300 are continuously carried out, thereby saving one-time pure water cleaning, most of metal particles and organic matters removed by the alkaline cleaning unit 200 are dissolved in water and directly deposited or removed in the alkaline cleaning tank 210, only part of the particles or organic matters are not completely removed, but then the acid cleaning solution directly carries out oxidation and acid cleaning on other metals and metal oxides on the surface of the silicon wafer to form a complex which is easily dissolved in water after the metal particles and organic matters enter the acid cleaning tank 310, meanwhile, the alkaline solution remaining on the silicon wafer is neutralized by the HCL in the acid cleaning tank 310, and the part of the particles or organic matters remaining in the alkaline cleaning is removed by the acid cleaning solution HCL in the acid cleaning tank 310, and then the metal particles and the acid cleaning solution together with the other metals and metal oxides removed are 540, the impurities on the surface of the silicon wafer can still be completely removed, and the silicon wafer with a clean surface can be obtained.
The fourth step: and (4) carrying out acid cleaning in an acid cleaning unit 400 to remove metal ions and metal oxides on the surface of the silicon wafer.
Specifically, the chemical solution in the pickling tank 310 is HCL, H2O2And H2Mixed liquid of O, HCL, H2O2:H2The volume ratio of O is 1:1:3-5, and the pickling temperature is 45-55 ℃. The acid washing tank 310 is provided with a heater and a megasonic device for emitting megasonic waves, the heater can ensure that the acid washing temperature is constant within the range of 45-55 ℃, the megasonic frequency in the acid washing tank 310 is also 860-950kHz, and the chemical reaction of the liquid medicine components, namely H, can be further accelerated2O2The metal ions are oxidized to produce metal oxides, the metal oxides react with hydrochloric acid solution to generate soluble complexes, metals removed by acid cleaning are mainly metal ions such as AL, Fe, Na and the like, and the complexes are cleaned by rapidly-washed pure water in a third cleaning tank 630.
The silicon wafer after being acid-washed enters a third washing tank 530 for quick draining and washing, and mainly removes acid-washing liquid medicine and residual impurities remained on the surface of the silicon wafer. In the structure of the third cleaning tank 530, as shown in fig. 5, during cleaning, after pure water flows for a certain time, water in the upper tank 531 quickly enters the lower tank 532 of the water storage tank, and meanwhile, the spray pipes 533 in the upper tank 531 always perform cross spray on the silicon wafers; and stopping spraying after a certain time of spraying, and further finishing the cleaning work of the silicon wafer. And finally cleaning the silicon wafer in a fourth cleaning tank 540 to ensure that the surface of the silicon wafer is cleaned.
The fifth step: and dehydrating and drying in the drying unit 600 to obtain the silicon wafer with clean surface quality and qualified product quality.
Specifically, the cleaned silicon wafer sequentially enters a full lifting groove 610 and a drying groove 620 in the drying unit 600, and the slow lifting groove 610 is a pure water groove, and the silicon wafer is slowly driven to lift upwards, so that a water film on the surface of the silicon wafer naturally flows down, and the formation of watermarks on the surface of the silicon wafer after drying is avoided. After the slow pulling groove 610 is cleaned, the silicon wafer is moved into the drying groove 620 to be dried, the drying groove 620 is arranged to completely dry the silicon wafer, the whole drying process is in a high-purity nitrogen atmosphere, and finally the silicon wafer with clean surface quality and qualified product quality is obtained.
Taking a silicon wafer with a diameter of 300mm as an example, the contrast values of the dirty flower ratio obtained by the cleaning process described in the facility example compared with the prior art are shown in table 1, except that the parameters are unchanged.
TABLE 1 dirty flower ratio contrast value
The surface topography of the silicon wafer cleaned by the cleaning process of the embodiment is shown in fig. 7, the surface topography of the silicon wafer cleaned by the existing cleaning process is shown in fig. 8, and the two figures show that the surface of the silicon wafer cleaned by the cleaning process is clean, smooth and bright, has no dirty flowers and has good cleaning quality; the silicon wafer surface cleaned by the existing cleaning process has obvious dirty patterns, oil stains, incapability of being cleaned and poor cleaning effect.
1. By adopting the cleaning mechanism and the cleaning process provided by the utility model, the dirty flower rate of the surface of the silicon wafer can be effectively reduced and the dirty flower rate of the silicon wafer can be less than 0.5% on the premise of not damaging the surface characteristics and the electrical characteristics of the silicon wafer; the residual dust, metal ions, organic matters and other impurities on the silicon wafer can be completely removed together, the cleaning quality is good, and the cleaning efficiency is high.
2. Ultrasonic waves or megasonic waves with different frequencies are set according to different cleaning characteristics of the pre-cleaning unit, the pre-pickling unit, the alkaline cleaning unit and the pickling unit so as to improve the cleaning effect; ultrasonic waves with the frequency of 25-35kHz are arranged in a pre-cleaning unit to accelerate cleaning of granular and bulk silicon powder particles, large pollution impurities and large metal particles attached to the surface of a silicon wafer; megasonic waves with the frequency of 860 and 950kHz are arranged in the pre-pickling unit, the alkaline washing unit and the pickling unit and combined with chemical reaction of a liquid reagent, so that the accelerated motion of liquid molecules can be further pushed, the surface of the wafer is continuously impacted by high-speed fluid waves, and tiny particles and tiny impurities attached to the surface of the wafer are forcibly removed and enter the cleaning liquid.
3. The pre-cleaning unit is mainly used for removing silicon powder, large particles and impurities attached to the surface of the silicon wafer; the pre-pickling unit mainly uses HF to remove an oxide layer on the surface of the silicon wafer to form a substance which is easy to dissolve in water, and then the substance is discharged along with pure water in a first cleaning tank; the alkali washing unit is mainly used for removing partial metal particles and organic matters below the oxide layer, namely, the metal particles and the organic matters pass through H firstly2O2Part of metal particles and organic matters are strongly oxidized, and substances after strong oxidation are NH4OH is dissolved, so that partial metal particles and organic matters are changed into water-soluble compounds, and can be removed along with the washing of pure water in a second washing tank; pickling unit mainIs to be used for removing metal ions and metal oxides, i.e. H, from the surface of a silicon wafer2O2Oxidizing metal ions to produce metal oxides, reacting the metal oxides with hydrochloric acid solution to generate soluble complexes, and then cleaning the soluble complexes by rapidly-washed pure water in a third cleaning tank to remove liquid medicine and residual impurities on the surface of the silicon wafer; then the silicon wafer enters a fourth cleaning tank for final cleaning so as to ensure that the surface of the silicon wafer is cleaned; and finally, drying and dehydrating in a drying unit to obtain the silicon wafer with clean surface quality and qualified product quality.
4. After being cleaned by the alkaline cleaning unit, the silicon wafer can also directly enter the acid cleaning unit for continuous acid cleaning, then sequentially enters the third cleaning tank for quick washing and the fourth cleaning tank for final cleaning, and then enters the drying unit for drying and dehydration, so that the required silicon wafer can be obtained.
The embodiments of the present invention have been described in detail, and the description is only for the preferred embodiments of the present invention, and should not be construed as limiting the scope of the present invention. All the equivalent changes and improvements made according to the application scope of the present invention should still fall within the patent coverage of the present invention.
Claims (10)
1. A semiconductor silicon wafer surface cleaning mechanism is characterized by at least sequentially comprising a pre-cleaning unit and an acid washing unit; wherein,
a pre-pickling unit and an alkaline washing unit are sequentially arranged between the pre-cleaning unit and the pickling unit, and the pre-pickling unit is arranged close to the pre-cleaning unit;
cleaning tanks are respectively arranged behind the pre-pickling unit, the alkaline washing unit and the acid washing unit;
or the pre-pickling unit and the pickling unit are respectively provided with the cleaning tanks.
2. The semiconductor silicon wafer surface cleaning mechanism according to claim 1, wherein the pre-pickling unit, the alkaline washing unit and the pickling unit respectively comprise at least one pre-pickling tank, one alkaline washing tank and one pickling tank.
3. The surface cleaning mechanism for semiconductor silicon wafers as claimed in claim 2, wherein two of the cleaning tanks are provided after the pickling unit, and the cleaning tank adjacent to the pickling unit is a fast draining flushing tank.
4. The surface cleaning mechanism for the semiconductor silicon wafer as claimed in claim 2 or 3, wherein the pre-pickling tank, the alkaline washing tank and the pickling tank are respectively provided with a megasonic device for emitting megasonic waves, and the megasonic frequencies in the pre-pickling tank, the alkaline washing tank and the pickling tank are the same.
5. The mechanism as claimed in claim 4, wherein the megasonic frequencies in the pre-pickling tank, the alkaline washing tank and the pickling tank are 860-950 kHz.
6. The semiconductor silicon wafer surface cleaning mechanism according to claim 5, wherein heaters are provided in the pre-pickling tank, the alkaline washing tank and the pickling tank, and the temperature of the heaters in the pre-pickling tank is different from the temperature in the alkaline washing tank and the pickling tank.
7. The surface cleaning mechanism for semiconductor silicon wafers as claimed in any one of claims 2-3 and 5-6, wherein the pre-cleaning unit comprises at least one pre-cleaning tank, and the pre-cleaning tank and the cleaning tank are pure water tanks.
8. The surface cleaning mechanism for semiconductor silicon wafers as set forth in claim 7, wherein the pre-cleaning tank is provided therein with ultrasonic means for emitting ultrasonic waves, and the frequency of the ultrasonic waves in the pre-cleaning tank is lower than the frequency of the megasonic waves in the pre-pickling tank.
9. The surface cleaning mechanism for the semiconductor silicon wafer as claimed in claim 8, wherein the ultrasonic frequency in the pre-cleaning tank is 25-35 kHz.
10. The semiconductor silicon wafer surface cleaning mechanism according to any one of claims 1 to 3, 5 to 6 and 8 to 9, wherein a drying unit is further provided after the pickling unit, the drying unit comprising a full-drawing tank and a drying tank; the full pulling groove is arranged close to the pickling unit.
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